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Sample records for tough high performance

  1. Fracture toughness of ultra high performance concrete by flexural performance

    Directory of Open Access Journals (Sweden)

    Manolova Emanuela

    2016-01-01

    Full Text Available This paper describes the fracture toughness of the innovative structural material - Ultra High Performance Concrete (UHPC, evaluated by flexural performance. For determination the material behaviour by static loading are used adapted standard test methods for flexural performance of fiber-reinforced concrete (ASTM C 1609 and ASTM C 1018. Fracture toughness is estimated by various deformation parameters derived from the load-deflection curve, obtained by testing simple supported beam under third-point loading, using servo-controlled testing system. This method is used to be estimated the contribution of the embedded fiber-reinforcement into improvement of the fractural behaviour of UHPC by changing the crack-resistant capacity, fracture toughness and energy absorption capacity with various mechanisms. The position of the first crack has been formulated based on P-δ (load- deflection response and P-ε (load - longitudinal deformation in the tensile zone response, which are used for calculation of the two toughness indices I5 and I10. The combination of steel fibres with different dimensions leads to a composite, having at the same time increased crack resistance, first crack formation, ductility and post-peak residual strength.

  2. Mental Toughness Moderates Social Loafing in Cycle Time-Trial Performance.

    Science.gov (United States)

    Haugen, Tommy; Reinboth, Michael; Hetlelid, Ken J; Peters, Derek M; Høigaard, Rune

    2016-09-01

    The purpose of this study was to determine if mental toughness moderated the occurrence of social loafing in cycle time-trial performance. Twenty-seven men (Mage = 17.7 years, SD = 0.6) completed the Sport Mental Toughness Questionnaire prior to completing a 1-min cycling trial under 2 conditions: once with individual performance identified, and once in a group with individual performance not identified. Using a median split of the mental toughness index, participants were divided into high and low mental toughness groups. Cycling distance was compared using a 2 (trial) × 2 (high-low mental toughness) analysis of variance. We hypothesized that mentally tough participants would perform equally well under both conditions (i.e., no indication of social loafing) compared with low mentally tough participants, who would perform less well when their individual performance was not identifiable (i.e., demonstrating the anticipated social loafing effect). The high mental toughness group demonstrated consistent performance across both conditions, while the low mental toughness group reduced their effort in the non-individually identifiable team condition. The results confirm that (a) clearly identifying individual effort/performance is an important situational variable that may impact team performance and (b) higher perceived mental toughness has the ability to negate the tendency to loaf.

  3. Flexural toughness of steel fiber reinforced high performance concrete containing nano-SiO2 and fly ash.

    Science.gov (United States)

    Zhang, Peng; Zhao, Ya-Nan; Li, Qing-Fu; Wang, Peng; Zhang, Tian-Hang

    2014-01-01

    This paper aims to clarify the effect of steel fiber on the flexural toughness of the high performance concrete containing fly ash and nano-SiO2. The flexural toughness was evaluated by two methods, which are based on ASTM C1018 and DBV-1998, respectively. By means of three-point bending method, the flexural toughness indices, variation coefficients of bearing capacity, deformation energy, and equivalent flexural strength of the specimen were measured, respectively, and the relational curves between the vertical load and the midspan deflection (P(V)-δ) were obtained. The results indicate that steel fiber has great effect on the flexural toughness parameters and relational curves (P(V)-δ) of the three-point bending beam specimen. When the content of steel fiber increases from 0.5% to 2%, the flexural toughness parameters increase gradually and the curves are becoming plumper and plumper with the increase of steel fiber content, respectively. However these flexural toughness parameters begin to decrease and the curves become thinner and thinner after the steel fiber content exceeds 2%. It seems that the contribution of steel fiber to the improvement of flexural toughness of the high performance concrete containing fly ash and nano-SiO2 is well performed only when the steel fiber content is less than 2%.

  4. Strength-toughness requirements for thick walled high pressure vessels

    International Nuclear Information System (INIS)

    Kapp, J.A.

    1990-01-01

    The strength and toughness requirements of materials for use in high pressure vessels has been the subject of some discussion in the meetings of the Materials Task Group of the Special Working Group High Pressure Vessels. A fracture mechanics analysis has been performed to theoretically establish the required toughness for a high pressure vessel. This paper reports that the analysis performed is based on the validity requirement for plane strain fracture of fracture toughness test specimens. This is that at the fracture event, the crack length, uncracked ligament, and vessel length must each be greater than fifty times the crack tip plastic zone size for brittle fracture to occur. For high pressure piping applications, the limiting physical dimension is the uncracked ligament, as it can be assumed that the other dimensions are always greater than fifty times the crack tip plastic zone. To perform the fracture mechanics analysis several parameters must be known: these include vessel dimensions, material strength, degree of autofrettage, and design pressure. Results of the analysis show, remarkably, that the effects of radius ratio, pressure and degree of autofrettage can be ignored when establishing strength and toughness requirements for code purposes. The only parameters that enter into the calculation are yield strength, toughness and vessel thickness. The final results can easily be represented as a graph of yield strength against toughness on which several curves, one for each vessel thickness, are plotted

  5. Relationship between mental toughness, stress appraisal, and innovation performance of R&D personnel

    Directory of Open Access Journals (Sweden)

    Feng Jin

    2016-01-01

    Full Text Available Four hundred and two R&D personnel were surveyed through questionnaires to study the relationship between mental toughness, stress appraisal (including experience of stress and stress control, and innovation performance. The findings reveal a significant negative correlation between mental toughness and stress experience and a significant positive correlation between mental toughness and both stress control and innovation performance. Furthermore, although the experience of stress was negatively correlated with innovation performance, stress control had the opposite effect. Experience of stress and stress control were the mediating variables for mental toughness and innovation performance, respectively. There was also a significant interaction effect between stress appraisal and mental toughness.

  6. Mental toughness in sport: motivational antecedents and associations with performance and psychological health.

    Science.gov (United States)

    Mahoney, John W; Gucciardi, Daniel F; Ntoumanis, Nikos; Mallett, Cliff J; Mallet, Cliff J

    2014-06-01

    We argue that basic psychological needs theory (BPNT) offers impetus to the value of mental toughness as a mechanism for optimizing human functioning. We hypothesized that psychological needs satisfaction (thwarting) would be associated with higher (lower) levels of mental toughness, positive affect, and performance and lower (higher) levels of negative affect. We also expected that mental toughness would be associated with higher levels of positive affect and performance and lower levels of negative affect. Further, we predicted that coaching environments would be related to mental toughness indirectly through psychological needs and that psychological needs would indirectly relate with performance and affect through mental toughness. Adolescent cross-country runners (136 male and 85 female, M(age) = 14.36) completed questionnaires pertaining to BPNT variables, mental toughness, and affect. Race times were also collected. Our findings supported our hypotheses. We concluded that BPNT is generative in understanding some of the antecedents and consequences of mental toughness and is a novel framework useful for understanding mental toughness.

  7. Study on elastic-plastic fracture toughness test in high temperature water

    International Nuclear Information System (INIS)

    Miura, Yasufumi

    2016-01-01

    Structural integrity of internal components in light water reactors is important for the safety of operation and service lifetime. Fracture toughness is important parameter for structural integrity assessment of nuclear power plant. In general, fracture toughness of materials which compose the components in light water reactor is obtained with fracture toughness tests in air although some components are subjected to high temperature water because of the difficulty of fracture toughness test in high temperature water. However, the effects of high temperature water and hydrogen on fracture behavior of the structural materials in nuclear power plant such as low alloy steel, cast austenitic stainless steel, and Ni base alloy are concerned recently. In this study, elastic-plastic fracture toughness test of low alloy steel in simulated BWR water environment was studied. Fracture toughness test in high temperature water with original clip gage and normalization data reduction technique was established. The difference of fracture toughness J_Q tested in air between using elastic unload compliance method and normalization data reduction technique was also discussed. As a result, obtained value with normalization data reduction technique tended to be higher than the value with elastic unload compliance. (author)

  8. Mental Toughness Moderates Social Loafing in Cycle Time-Trial Performance

    Science.gov (United States)

    Haugen, Tommy; Reinboth, Michael; Hetlelid, Ken J.; Peters, Derek M.; Høigaard, Rune

    2016-01-01

    Purpose: The purpose of this study was to determine if mental toughness moderated the occurrence of social loafing in cycle time-trial performance. Method: Twenty-seven men (M[subscript age] = 17.7 years, SD = 0.6) completed the Sport Mental Toughness Questionnaire prior to completing a 1-min cycling trial under 2 conditions: once with individual…

  9. Electrostatic Assembly Preparation of High-Toughness Zirconium Diboride-Based Ceramic Composites with Enhanced Thermal Shock Resistance Performance.

    Science.gov (United States)

    Zhang, Baoxi; Zhang, Xinghong; Hong, Changqing; Qiu, Yunfeng; Zhang, Jia; Han, Jiecai; Hu, PingAn

    2016-05-11

    The central problem of using ceramic as a structural material is its brittleness, which associated with rigid covalent or ionic bonds. Whiskers or fibers of strong ceramics such as silicon carbide (SiC) or silicon nitride (Si3N4) are widely embedded in a ceramic matrix to improve the strength and toughness. The incorporation of these insulating fillers can impede the thermal flow in ceramic matrix, thus decrease its thermal shock resistance that is required in some practical applications. Here we demonstrate that the toughness and thermal shock resistance of zirconium diboride (ZrB2)/SiC composites can be improved simultaneously by introducing graphene into composites via electrostatic assembly and subsequent sintering treatment. The incorporated graphene creates weak interfaces of grain boundaries (GBs) and optimal thermal conductance paths inside composites. In comparison to pristine ZrB2-SiC composites, the toughness of (2.0%) ZrB2-SiC/graphene composites exhibited a 61% increasing (from 4.3 to 6.93 MPa·m(1/2)) after spark plasma sintering (SPS); the retained strength after thermal shock increased as high as 74.8% at 400 °C and 304.4% at 500 °C. Present work presents an important guideline for producing high-toughness ceramic-based composites with enhanced thermal shock properties.

  10. Comparisons of irradiation-induced shifts in fracture toughness, crack arrest toughness, and Charpy impact energy in high-copper welds

    International Nuclear Information System (INIS)

    Corwin, W.R.; Nanstad, R.K.; Iskander, S.K.

    1991-01-01

    The Heavy-Section Steel Irradiation (HSSI) Program is examining relative shifts and changes in shape of fracture and crack-arrest toughness versus temperature behavior for two high-copper welds. Fracture toughness 100-MPa√m temperature shifts are greater than Charpy 41-J shifts for both welds. Mean curve fits to the fracture toughness data provide mixed results regarding curve shape changes, but curves constructed as lower boundaries indicate lower slopes. Preliminary crack-arrest toughness results indicate that shifts of lower-bound curves are approximately the same as CVN 41-J shifts with no shape changes

  11. Processing of a new high strength high toughness steel with duplex microstructure (Ferrite + Austenite)

    International Nuclear Information System (INIS)

    Martis, Codrick J.; Putatunda, Susil K.; Boileau, James

    2013-01-01

    Highlights: ► This new steel has exceptional combination of high strength and fracture toughness. ► Austempering treatment resulted in a very fine scale bainitic ferrite microstructure. ► As the austempering temperature increases yield strength and toughness decreases. ► Maximum fracture toughness of 105 MPa √m is obtained after austempering at 371 °C. ► A relationship between fracture toughness and the parameter σ y (X γ C γ ) 1/2 was observed. - Abstract: In this investigation a new third generation advanced high strength steel (AHSS) has been developed. This steel was synthesized by austempering of a low carbon and low alloy steel with high silicon content. The influence of austempering temperature on the microstructure and the mechanical properties including the fracture toughness of this steel was also examined. Compact tension and cylindrical tensile specimens were prepared from a low carbon low alloy steel and were initially austenitized at 927 °C for 2 h and then austempered in the temperature range between 371 °C and 399 °C to produce different microstructures. The microstructures were characterized by X-ray diffraction, scanning electron microscopy and optical metallography. Test results show that the austempering heat treatment has resulted in a microstructure consisting of very fine scale bainitic ferrite and austenite. A combination of very high tensile strength of 1388 MPa and fracture toughness of 105 MPa √m was obtained after austempering at 371 °C

  12. Mental toughness latent profiles in endurance athletes.

    Science.gov (United States)

    Zeiger, Joanna S; Zeiger, Robert S

    2018-01-01

    Mental toughness in endurance athletes, while an important factor for success, has been scarcely studied. An online survey was used to examine eight mental toughness factors in endurance athletes. The study aim was to determine mental toughness profiles via latent profile analysis in endurance athletes and whether associations exist between the latent profiles and demographics and sports characteristics. Endurance athletes >18 years of age were recruited via social media outlets (n = 1245, 53% female). Mental toughness was measured using the Sports Mental Toughness Questionnaire (SMTQ), Psychological Performance Inventory-Alternative (PPI-A), and self-esteem was measured using the Rosenberg Self-Esteem Scale (RSE). A three-class solution emerged, designated as high mental toughness (High MT), moderate mental toughness (Moderate MT) and low mental toughness (Low MT). ANOVA tests showed significant differences between all three classes on all 8 factors derived from the SMTQ, PPI-A and the RSE. There was an increased odds of being in the High MT class compared to the Low MT class for males (OR = 1.99; 95% CI, 1.39, 2.83; Pathletes who were over 55 compared to those who were 18-34 (OR = 2.52; 95% CI, 1.37, 4.62; Pathletes. High MT is associated with demographics and sports characteristics. Mental toughness screening in athletes may help direct practitioners with mental skills training.

  13. Mental toughness latent profiles in endurance athletes.

    Directory of Open Access Journals (Sweden)

    Joanna S Zeiger

    Full Text Available Mental toughness in endurance athletes, while an important factor for success, has been scarcely studied. An online survey was used to examine eight mental toughness factors in endurance athletes. The study aim was to determine mental toughness profiles via latent profile analysis in endurance athletes and whether associations exist between the latent profiles and demographics and sports characteristics. Endurance athletes >18 years of age were recruited via social media outlets (n = 1245, 53% female. Mental toughness was measured using the Sports Mental Toughness Questionnaire (SMTQ, Psychological Performance Inventory-Alternative (PPI-A, and self-esteem was measured using the Rosenberg Self-Esteem Scale (RSE. A three-class solution emerged, designated as high mental toughness (High MT, moderate mental toughness (Moderate MT and low mental toughness (Low MT. ANOVA tests showed significant differences between all three classes on all 8 factors derived from the SMTQ, PPI-A and the RSE. There was an increased odds of being in the High MT class compared to the Low MT class for males (OR = 1.99; 95% CI, 1.39, 2.83; P<0.001, athletes who were over 55 compared to those who were 18-34 (OR = 2.52; 95% CI, 1.37, 4.62; P<0.01, high sports satisfaction (OR = 8.17; 95% CI, 5.63, 11.87; P<0.001, and high division placement (OR = 2.18; 95% CI, 1.46,3.26; P<0.001. The data showed that mental toughness latent profiles exist in endurance athletes. High MT is associated with demographics and sports characteristics. Mental toughness screening in athletes may help direct practitioners with mental skills training.

  14. Fracture toughness measurements on a glass bonded sodalite high-level waste form

    International Nuclear Information System (INIS)

    DiSanto, T.; Goff, K. M.; Johnson, S. G.; O'Holleran, T. P.

    1999-01-01

    The electrometallurgical treatment of metallic spent nuclear fuel produces two high-level waste streams; cladding hulls and chloride salt. Argonne National Laboratory is developing a glass bonded sodalite waste form to immobilize the salt waste stream. The waste form consists of 75 Vol.% crystalline sodalite (containing the salt) with 25 Vol.% of an ''intergranular'' glassy phase. Microindentation fracture toughness measurements were performed on representative samples of this material using a Vickers indenter. Palmqvist cracking was confirmed by post-indentation polishing of a test sample. Young's modulus was measured by an acoustic technique. Fracture toughness, microhardness, and Young's modulus values are reported, along with results from scanning electron microscopy studies

  15. User's Guide for TOUGH2-MP - A Massively Parallel Version of the TOUGH2 Code

    International Nuclear Information System (INIS)

    Earth Sciences Division; Zhang, Keni; Zhang, Keni; Wu, Yu-Shu; Pruess, Karsten

    2008-01-01

    TOUGH2-MP is a massively parallel (MP) version of the TOUGH2 code, designed for computationally efficient parallel simulation of isothermal and nonisothermal flows of multicomponent, multiphase fluids in one, two, and three-dimensional porous and fractured media. In recent years, computational requirements have become increasingly intensive in large or highly nonlinear problems for applications in areas such as radioactive waste disposal, CO2 geological sequestration, environmental assessment and remediation, reservoir engineering, and groundwater hydrology. The primary objective of developing the parallel-simulation capability is to significantly improve the computational performance of the TOUGH2 family of codes. The particular goal for the parallel simulator is to achieve orders-of-magnitude improvement in computational time for models with ever-increasing complexity. TOUGH2-MP is designed to perform parallel simulation on multi-CPU computational platforms. An earlier version of TOUGH2-MP (V1.0) was based on the TOUGH2 Version 1.4 with EOS3, EOS9, and T2R3D modules, a software previously qualified for applications in the Yucca Mountain project, and was designed for execution on CRAY T3E and IBM SP supercomputers. The current version of TOUGH2-MP (V2.0) includes all fluid property modules of the standard version TOUGH2 V2.0. It provides computationally efficient capabilities using supercomputers, Linux clusters, or multi-core PCs, and also offers many user-friendly features. The parallel simulator inherits all process capabilities from V2.0 together with additional capabilities for handling fractured media from V1.4. This report provides a quick starting guide on how to set up and run the TOUGH2-MP program for users with a basic knowledge of running the (standard) version TOUGH2 code. The report also gives a brief technical description of the code, including a discussion of parallel methodology, code structure, as well as mathematical and numerical methods used

  16. Fracture toughness of welded joints of a high strength low alloy steel

    International Nuclear Information System (INIS)

    Veiga, S.M.B. da; Bastian, F.L.; Pope, A.M.

    1985-10-01

    The fracture toughness of the different regions of welded joints of a high strength low alloy steel, Niocor 2, was evaluated at different temperatures and compared with the toughness of the base metal. The studied regions were: the weld metal, fusion boundary and heat affected zone. The welding process used was the manual metal arc. It is shown that the weld metal region has the highest toughness values. (Author) [pt

  17. Process development for 9Cr nanostructured ferritic alloy (NFA) with high fracture toughness

    International Nuclear Information System (INIS)

    Byun, Thak Sang; Yoon, Ji Hyun; Hoelzer, David T.; Lee, Yong Bok; Kang, Suk Hoon; Maloy, Stuart A.

    2014-01-01

    This article is to summarize the process development and key characterization results for the newly-developed Fe–9Cr based nanostructured ferritic alloys (NFAs) with high fracture toughness. One of the major drawbacks from pursuing ultra-high strength in the past development of NFAs is poor fracture toughness at high temperatures although a high fracture toughness is essential to prevent cracking during manufacturing and to mitigate or delay irradiation-induced embrittlement in irradiation environments. A study on fracture mechanism using the NFA 14YWT found that the low-energy grain boundary decohesion in fracture process at a high temperature (>200 °C) resulted in low fracture toughness. Lately, efforts have been devoted to explore an integrated process to enhance grain bonding. Two base materials were produced through mechanical milling and hot extrusion and designated as 9YWTV-PM1 and 9YWTV-PM2. Isothermal annealing (IA) and controlled rolling (CR) treatments in two phase region were used to enhance diffusion across the interfaces and boundaries. The PM2 alloy after CR treatments showed high fracture toughness (K JQ ) at represented temperatures: 240–280 MPa √m at room temperature and 160–220 MPa √m at 500 °C, which indicates that the goal of 100 MPa √m over possible nuclear application temperature range has been well achieved. Furthermore, it is also confirmed by comparison that the CR treatments on 9YWTV-PM2 result in high fracture toughness similar to or higher than those of the conventional ferritic–martensitic steels such as HT9 and NF616

  18. Anisotropy of fracture toughness of austenitic high nitrogen chromium-manganese steel

    International Nuclear Information System (INIS)

    Balitskii, A.I.; Pokhmurskii, V.I.; Diener, M.; Magdowski, R.; Speidel, M.O.

    1999-01-01

    The anisotropy of mechanical properties, in particular of the fracture toughness measured by the J-integral method, is demonstrated for industrially manufactured high strength retaining rings made from the nitrogen alloyed steel 18Mn18Cr. The RT-orientation turns out to be the weakest with regard to the resistance of the material to stable crack growth. The fracture toughness results are compared with results from calorimetric measurements. Here, also an orientation dependence of the heat irradiation energy is observed, clearly showing the same ranking of specimen orientation as the toughness data suggest. (orig.)

  19. Performance and biocompatibility of extremely tough alginate/polyacrylamide hydrogels.

    Science.gov (United States)

    Darnell, Max C; Sun, Jeong-Yun; Mehta, Manav; Johnson, Christopher; Arany, Praveen R; Suo, Zhigang; Mooney, David J

    2013-11-01

    Although hydrogels now see widespread use in a host of applications, low fracture toughness and brittleness have limited their more broad use. As a recently described interpenetrating network (IPN) of alginate and polyacrylamide demonstrated a fracture toughness of ≈ 9000 J/m(2), we sought to explore the biocompatibility and maintenance of mechanical properties of these hydrogels in cell culture and in vivo conditions. These hydrogels can sustain a compressive strain of over 90% with minimal loss of Young's Modulus as well as minimal swelling for up to 50 days of soaking in culture conditions. Mouse mesenchymal stem cells exposed to the IPN gel-conditioned media maintain high viability, and although cells exposed to conditioned media demonstrate slight reductions in proliferation and metabolic activity (WST assay), these effects are abrogated in a dose-dependent manner. Implantation of these IPN hydrogels into subcutaneous tissue of rats for 8 weeks led to mild fibrotic encapsulation and minimal inflammatory response. These results suggest the further exploration of extremely tough alginate/PAAM IPN hydrogels as biomaterials. © 2013 Elsevier Ltd. All rights reserved.

  20. High-temperature fracture toughness of duplex microstructures

    International Nuclear Information System (INIS)

    French, J.D.; Chan, H.M.; Harmer, M.P.; Miller, G.A.

    1996-01-01

    The temperature dependence of the fracture toughness of ceramics exhibiting duplex microstructures was studied relative to their single-phase constituents using two test methods: bend testing of chevron-notched beams, and the indentation-crack-length technique. The two materials systems studied were Al 2 O 3 :c-ZrO 2 (Y) and Al 2 O 3 :Y 3 Al 5 O 12 (YAG), and the testing temperature ranged from room temperature to 1,200 C. The study showed that in both systems the duplex materials showed higher toughness values than their single-phase constituents above 800 C. This result was attributed to the contribution of low-energy interphase boundaries to the overall composite toughness. Indentation crack length measurements gave toughness values and trends comparable to those determined by the chevron-notched beam method. By comparing the results of the two test methods it was possible to demonstrate that the indentation calibration constant (ξ) shows no significant temperature or material dependence. For the zirconia-containing materials, however, indentation at elevated temperatures is accompanied by significant localized plasticity, which suppressed the radial cracking. Under such conditions, some caution is warranted, since localized plasticity can lead to an overestimation of the fracture toughness

  1. Thin slab processing of acicular ferrite steels with high toughness

    Energy Technology Data Exchange (ETDEWEB)

    Reip, Carl-Peter; Hennig, Wolfgang; Hagmann, Rolf [SMS Demag Aktiengesellschaft, Duesseldorf (Germany); Sabrudin, Bin Mohamad Suren; Susanta, Ghosh; Lee, Weng Lan [Megasteel Sdn Bhd, Banting (Malaysia)

    2005-07-01

    Near-net-shape casting processes today represent an important option in steelmaking. High productivity and low production cost as well as the variety of steel grades that can be produced plus an excellent product quality are key factors for the acceptance of such processes in markets all over the world. Today's research focuses on the production of pipe steel with special requirements in terms of toughness at low temperatures. The subject article describes the production of hot strip made from acicular ferritic / bainitic steel grades using the CSP thin-slab technology. In addition, the resulting strength and toughness levels as a function of the alloying concepts are discussed. Optimal control of the CSP process allows the production of higher-strength hot-rolled steel grades with a fine-grain acicular-ferritic/bainitic microstructure. Hot strip produced in this way is characterized by a high toughness at low temperatures. In a drop weight tear test, transition temperatures of up to -50 deg C can be achieved with a shear-fracture share of 85%. (author)

  2. High toughness alumina/aluminate: The role of hetero-interfaces

    International Nuclear Information System (INIS)

    Brito, M.E.; Yasuoka, M.; Kanzaki, S.

    1996-01-01

    Silica doped alumina/aluminate materials present a combination of high strength and high toughness not achieved before in other alumina systems, except for transformation toughened alumina. The authors have associated the increase in toughness to crack bridging by anisotropically grown alumina grains with concurrent interfacial debonding of these grains. A HREM study of grain boundaries and hetero-interface structures in this material shows the absence of amorphous phases at grain boundaries. Local Auger electron analysis of fractured surfaces revealed the coexistence of Si and La at the grain facets exposed by the noticeable intergranular fracture mode of this material. It is concluded that a certain and important degree of boundaries weakness is related to both presence of Si at the interfaces and existence of alumina/aluminate hetero-interfaces

  3. Effect on High-Intensity Fields of a Tough Hydrophone With Hydrothermal PZT Thick-Film Vibrator and Titanium Front Layer.

    Science.gov (United States)

    Okada, Nagaya; Takeuchi, Shinichi

    2017-07-01

    A novel tough hydrophone was fabricated by depositing hydrothermally synthesized lead zirconate titanate polycrystalline film on the back-side surface of a titanium plate. Our developed tough hydrophone resisted damage in a high-pressure field (15 MPa) at a focal point of a sinusoidal continuous wave driven by a concave high-intensity focused ultrasound (HIFU) transducer with up to 50 W of power input to the sound source. The hydrophone was suitable for the HIFU field, even though the hydrophone has a flat-shape tip of 3.5 mm diameter, which is slightly larger than the wavelength of a few megahertz. In this paper, experiments are performed to assess the effect on the HIFU field of changing the shape of the tough hydrophone, with the aim of developing a tough hydrophone. The spatial distribution of the acoustic bubbles around the focal point was visualized by using ultrasonic diagnostic equipment with the tough hydrophone located at the focal point of the HIFU transducer. From the visualization, the trapped acoustic bubbles were seen to arise from the standing wave, which implies that the acoustic pressure is reduced by this cloud of acoustic bubbles that appeared during hydrophone measurement. Although cavitation and acoustic bubbles may be unavoidable when using high-intensity ultrasound, the estimated result of evaluating acoustic fields without misunderstanding by acoustic bubbles can be obtained by the aid of visualizing bubbles around the tough hydrophone.

  4. Master curve based correlation between static initiation toughness KIC and crack arrest toughness KIa

    International Nuclear Information System (INIS)

    Wallin, K.; Rintamaa, R.

    1999-01-01

    Historically the ASME reference curve concept assumes a constant relation between static fracture toughness initiation toughness and crack arrest toughness. In reality, this is not the case. Experimental results show that the difference between K IC and K Ia is material specific. For some materials there is a big difference while for others they nearly coincide. So far, however, no systematic study regarding a possible correlation between the two parameters has been performed. The recent Master curve method, developed for brittle fracture initiation estimation, has enabled a consistent analysis of fracture initiation toughness data. The Master curve method has been modified to be able to describe also crack arrest toughness. Here, this modified 'crack arrest master curve' is further validated and used to develop a simple, but yet (for safety assessment purpose) adequately accurate correlation between the two fracture toughness parameters. The correlation enables the estimation of crack arrest toughness from small Charpy-sized static fracture toughness tests. The correlation is valid for low Nickel steels ≤ (1.2% Ni). If a more accurate description of the crack arrest toughness is required, it can either be measured experimentally or estimated from instrumented Charpy-V crack arrest load information. (orig.)

  5. Recent advances in high performance poly(lactide): From ``green'' plasticization to super-tough materials via (reactive) compounding

    Science.gov (United States)

    Kfoury, Georgio; Raquez, Jean-Marie; Hassouna, Fatima; Odent, Jérémy; Toniazzo, Valérie; Ruch, David; Dubois, Philippe

    2013-12-01

    Due to its origin from renewable resources, its biodegradability, and recently, its industrial implementation at low costs, poly(lactide) (PLA) is considered as one of the most promising ecological, bio-sourced and biodegradable plastic materials to potentially and increasingly replace traditional petroleum derived polymers in many commodity and engineering applications. Beside its relatively high rigidity (high tensile strength and modulus compared with many common thermoplastics such as poly(ethylene terephthalate) (PET), high impact poly(styrene) (HIPS) and poly(propylene) (PP)), PLA suffers from an inherent brittleness, which can limit its applications especially where mechanical toughness such as plastic deformation at high impact rates or elongation is required. Therefore, the curve plotting stiffness vs. impact resistance and ductility must be shifted to higher values for PLA-based materials, while being preferably fully bio-based and biodegradable upon the application. This review aims to establish a state of the art focused on the recent progresses and preferably economically viable strategies developed in the literature for significantly improve the mechanical performances of PLA. A particular attention is given to plasticization as well as to impact resistance modification of PLA in the case of (reactive) blending PLA-based systems.

  6. Recent advances in high performance poly(lactide: From green plasticization to super-tough materials via (reactive compounding

    Directory of Open Access Journals (Sweden)

    Georgio eKfoury

    2013-12-01

    Full Text Available Due to its origin from renewable resources, its biodegradability, and recently, its industrial implementation at low costs, poly(lactide (PLA is considered as one of the most promising ecological, bio-sourced and biodegradable plastic materials to potentially and increasingly replace traditional petroleum derived polymers in many commodity and engineering applications. Beside its relatively high rigidity (high tensile strength and modulus compared with many common thermoplastics such as poly(ethylene terephthalate (PET, high impact poly(styrene (HIPS and poly(propylene (PP, PLA suffers from an inherent brittleness, which can limit its applications especially where mechanical toughness such as plastic deformation at high impact rates or elongation is required. Therefore, the curve plotting stiffness vs. impact resistance and ductility must be shifted to higher values for PLA-based materials, while being preferably fully bio-based and biodegradable upon the application.This review aims to establish a state of the art focused on the recent progresses and preferably economically viable strategies developed in the literature for significantly improve the mechanical performances of PLA. A particular attention is given to plasticization as well as to impact resistance modification of PLA in the case of (reactive blending PLA-based systems.

  7. The weak interfaces within tough natural composites: experiments on three types of nacre.

    Science.gov (United States)

    Khayer Dastjerdi, Ahmad; Rabiei, Reza; Barthelat, Francois

    2013-03-01

    Mineralization is a typical strategy used in natural materials to achieve high stiffness and hardness for structural functions such as skeletal support, protection or predation. High mineral content generally leads to brittleness, yet natural materials such as bone, mollusk shells or glass sponge achieve relatively high toughness considering the weakness of their constituents through intricate microstructures. In particular, nanometers thick organic interfaces organized in micro-architectures play a key role in providing toughness by various processes including crack deflection, crack bridging or energy dissipation. While these interfaces are critical in these materials, their composition, structure and mechanics is often poorly understood. In this work we focus on nacre, one of the most impressive hard biological materials in terms of toughness. We performed interfacial fracture tests on chevron notched nacre samples from three different species: red abalone, top shell and pearl oyster. We found that the intrinsic toughness of the interfaces is indeed found to be extremely low, in the order of the toughness of the mineral inclusions themselves. Such low toughness is required for the cracks to follow the interfaces, and to deflect and circumvent the mineral tablets. This result highlights the efficacy of toughening mechanisms in natural materials, turning low-toughness inclusions and interfaces into high-performance composites. We found that top shell nacre displayed the highest interfacial toughness, because of higher surface roughness and a more resilient organic material, and also through extrinsic toughening mechanisms including crack deflection, crack bridging and process zone. In the context of biomimetics, the main implication of this finding is that the interface in nacre-like composite does not need to be tough; the extensibility or ductility of the interfaces may be more important than their strength and toughness to produce toughness at the macroscale

  8. Assessment of fracture toughness of structural steels

    Energy Technology Data Exchange (ETDEWEB)

    Gomes Junyor, José Onésimo; Faria, Stéfanno Bruno; Rocha, Nirlando Antônio; Reis, Emil; Vilela, Jefferson José, E-mail: ze_onezo@hotmail.com, E-mail: sbrunofaria@gmail.com, E-mail: nar@cdtn.br, E-mail: emilr@cdtn.br, E-mail: jjv@cdtn.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil); Centro Universitário de Belo Horizonte (UNIBH), MG (Brazil); Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2017-11-01

    The fracture toughness parameters are applied to estimate the lifetime of mechanical components and define the criteria of safe failure and tolerable damages. This information allows equipment to be used longer with a high degree of safety. These techniques are applied in the Leak-Before-Break (LBB) concept that is accepted for designing the piping system of the primary circuit of the pressurized water reactor (PWR). In this work, fracture toughness tests such as J{sub IC} and CTOD were performed on some structural steels. The fracture toughness parameters were determined using SE(B) and C(T) test specimens. The fracture toughness values for the same material varied according to the type specimen. The parameter δ{sub 1c} showed different values when it was calculated using the ASTM E1820 standard and using the BS 7448: Part 1 standard. These results indicate that procedures of these standards need to be improved. Two systems with different sensitivity in the force measurement were used that showed similar results for toughness fracture but the dispersion was different. (author)

  9. High hardness-high toughness WC-20Co nanocomposites: Effect of VC variation and sintering temperature

    International Nuclear Information System (INIS)

    Kumar, Devender; Singh, K.

    2016-01-01

    WC-Co nanocomposites with variable VC content are synthesized by liquid phase sintering at two different temperatures. The as synthesized samples are characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and optical microscope. The mechanical properties are obtained by Vickers indentation method. The high content of VC, lead to high porosity when sintering temperature is increased from 1350 to 1400 °C. The relative density of all the samples is more than 95%. Microstructure reveals that agglomeration of W-Co-C and V-W-C increases at 1400 °C, which generates layered interfaces in radial direction and hence the material inhomogeneity. XRD pattern shows that the formation of η phase increases at 1400 °C, which is responsible to decrease the fracture toughness of the present samples. The average particle size of 102 nm, highest hardness of 1870.6 kgf/mm"2 with fracture toughness of 14.4 MN/mm"3"/"2 is observed in sample having 7.5 wt% VC, sintered at 1350 °C for one minute. This combination shows the highest hardness and reasonably high toughness as compared to conventionally sintered materials reported so far.

  10. High temperature homogenization improves impact toughness of vitamin E-diffused, irradiated UHMWPE.

    Science.gov (United States)

    Oral, Ebru; O'Brien, Caitlin; Doshi, Brinda; Muratoglu, Orhun K

    2017-06-01

    Diffusion of vitamin E into radiation cross-linked ultrahigh molecular weight polyethylene (UHMWPE) is used to increase stability against oxidation of total joint implant components. The dispersion of vitamin E throughout implant preforms has been optimized by a two-step process of doping and homogenization. Both of these steps are performed below the peak melting point of the cross-linked polymer (homogenization of antioxidant-doped, radiation cross-linked UHMWPE could improve its toughness. We found that homogenization at 300°C for 8 h resulted in an increase in the impact toughness (74 kJ/m 2 compared to 67 kJ/m 2 ), the ultimate tensile strength (50 MPa compared to 43 MPa) and elongation at break (271% compared to 236%). The high temperature treatment did not compromise the wear resistance or the oxidative stability as measured by oxidation induction time. In addition, the desired homogeneity was achieved at a much shorter duration (8 h compared to >240 h) by using high temperature homogenization. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1343-1347, 2017. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

  11. Architected Lattices with High Stiffness and Toughness via Multicore-Shell 3D Printing.

    Science.gov (United States)

    Mueller, Jochen; Raney, Jordan R; Shea, Kristina; Lewis, Jennifer A

    2018-03-01

    The ability to create architected materials that possess both high stiffness and toughness remains an elusive goal, since these properties are often mutually exclusive. Natural materials, such as bone, overcome such limitations by combining different toughening mechanisms across multiple length scales. Here, a new method for creating architected lattices composed of core-shell struts that are both stiff and tough is reported. Specifically, these lattices contain orthotropic struts with flexible epoxy core-brittle epoxy shell motifs in the absence and presence of an elastomeric silicone interfacial layer, which are fabricated by a multicore-shell, 3D printing technique. It is found that architected lattices produced with a flexible core-elastomeric interface-brittle shell motif exhibit both high stiffness and toughness. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Ultrahigh Charpy impact toughness (~450J) achieved in high strength ferrite/martensite laminated steels

    Science.gov (United States)

    Cao, Wenquan; Zhang, Mingda; Huang, Chongxiang; Xiao, Shuyang; Dong, Han; Weng, Yuqing

    2017-02-01

    Strength and toughness are a couple of paradox as similar as strength-ductility trade-off in homogenous materials, body-centered-cubic steels in particular. Here we report a simple way to get ultrahigh toughness without sacrificing strength. By simple alloying design and hot rolling the 5Mn3Al steels in ferrite/austenite dual phase temperature region, we obtain a series of ferrite/martensite laminated steels that show up-to 400-450J Charpy V-notch impact energy combined with a tensile strength as high as 1.0-1.2 GPa at room temperature, which is nearly 3-5 times higher than that of conventional low alloy steels at similar strength level. This remarkably enhanced toughness is mainly attributed to the delamination between ferrite and martensite lamellae. The current finding gives us a promising way to produce high strength steel with ultrahigh impact toughness by simple alloying design and hot rolling in industry.

  13. Tough nanocomposite ionogel-based actuator exhibits robust performance.

    Science.gov (United States)

    Liu, Xinhua; He, Bin; Wang, Zhipeng; Tang, Haifeng; Su, Teng; Wang, Qigang

    2014-10-20

    Ionogel electrolytes can be fabricated for electrochemical actuators with many desirable advantages, including direct low-voltage control in air, high electrochemical and thermal stability, and complete silence during actuation. However, the demands for active actuators with above features and load-driving ability remain a challenge; much work is necessary to enhance the mechanical strength of electrolyte materials. Herein, we describe a cross-linked supramolecular approach to prepare tough nanocomposite gel electrolytes from HEMA, BMIMBF4, and TiO2 via self-initiated UV polymerization. The tough and stable ionogels are emerging to fabricate electric double-layer capacitor-like soft actuators, which can be driven by electrically induced ion migration. The ionogel-based actuator shows a displacement response of 5.6 mm to the driving voltage of 3.5 V. After adding the additional mass weight of the same as the actuator, it still shows a large displacement response of 3.9 mm. Furthermore, the actuator can not only work in harsh temperature environments (100°C and -10°C) but also realize the goal of grabbing an object by adjusting the applied voltage.

  14. Recent advances in high performance poly(lactide): from “green” plasticization to super-tough materials via (reactive) compounding

    Science.gov (United States)

    Kfoury, Georgio; Raquez, Jean-Marie; Hassouna, Fatima; Odent, Jérémy; Toniazzo, Valérie; Ruch, David; Dubois, Philippe

    2013-01-01

    Due to its origin from renewable resources, its biodegradability, and recently, its industrial implementation at low costs, poly(lactide) (PLA) is considered as one of the most promising ecological, bio-sourced and biodegradable plastic materials to potentially and increasingly replace traditional petroleum derived polymers in many commodity and engineering applications. Beside its relatively high rigidity [high tensile strength and modulus compared with many common thermoplastics such as poly(ethylene terephthalate) (PET), high impact poly(styrene) (HIPS) and poly(propylene) (PP)], PLA suffers from an inherent brittleness, which can limit its applications especially where mechanical toughness such as plastic deformation at high impact rates or elongation is required. Therefore, the curve plotting stiffness vs. impact resistance and ductility must be shifted to higher values for PLA-based materials, while being preferably fully bio-based and biodegradable upon the application. This review aims to establish a state of the art focused on the recent progresses and preferably economically viable strategies developed in the literature for significantly improve the mechanical performances of PLA. A particular attention is given to plasticization as well as to impact resistance modification of PLA in the case of (reactive) blending PLA-based systems. PMID:24790960

  15. Crack Arrest Toughness of Two High Strength Steels (AISI 4140 and AISI 4340)

    Science.gov (United States)

    Ripling, E. J.; Mulherin, J. H.; Crosley, P. B.

    1982-04-01

    The crack initiation toughness ( K c ) and crack arrest toughness ( K a ) of AISI 4140 and AISI 4340 steel were measured over a range of yield strengths from 965 to 1240 MPa, and a range of test temperatures from -53 to +74°C. Emphasis was placed on K a testing since these values are thought to represent the minimum toughness of the steel as a function of loading rate. At the same yield strengths and test temperatures, K a for the AISI 4340 was about twice as high as it was for the AISI 4140. In addition, the K a values showed a more pronounced transition temperature than the K c values, when the data were plotted as a function of test temperature. The transition appeared to be associated with a change in fracture mechanism from cleavage to dimpled rupture as the test temperature was increased. The occurrence of a “pop-in” behavior at supertransition temperatures has not been found in lower strength steels, and its evaluation in these high strength steels was possible only because they are not especially tough at their supertransition temperatures. There is an upper toughness limit at which pop-in will not occur, and this was found for the AISI 4340 steel when it was tempered to its lowest yield strength (965 MPa). All the crack arrest data were identified as plane strain values, while only about one-half of the initiation values could be classified this way.

  16. The Evolution of Plate and Extruded Products with High Strength and Fracture Toughness

    Science.gov (United States)

    Denzer, D. K.; Rioja, R. J.; Bray, G. H.; Venema, G. B.; Colvin, E. L.

    From the first use of 2017-T74 on the Junkers F13, improvements have been made to plate and extruded products for applications requiring the highest attainable strength and adequate fracture toughness. One such application is the upper wing of large aircraft. The progression of these product improvements achieved through the development of alloys that include 7075-(T6 & T76), 7150-(T6 & T77) and 7055-(T77 & T79) and most recently 7255-(T77 & T79) is reviewed. The most current advancements include aluminum-copper-lithium, alloy 2055 plate and extruded products that can attain strength equivalent to that of 7055-T77 with higher modulus, similar fracture toughness and improved fatigue, fatigue crack growth and corrosion performance. The achievement of these properties is explained in terms of the several alloy design principles. The highly desired and balanced characteristics make these products ideal for upper wing applications.

  17. Fracture toughness of welded joints of ASTM A543 steel plate

    International Nuclear Information System (INIS)

    Susukida, H.; Uebayashi, T.; Yoshida, K.; Ando, Y.

    1977-01-01

    Fracture toughness and weldability tests have been performed on a high strength steel which is a modification of ASTM A543 Grade B Class 1 steel, with a view to using it for nuclear reactor containment vessels. The results showed that fracture toughness of welded joints of ASTM A543 modified high strength steel is superior and the steel is suitable for manufacturing the containment vessels

  18. GOAL PROFILES, MENTAL TOUGHNESS AND ITS INFLUENCE ON PERFORMANCE OUTCOMES AMONG WUSHU ATHLETES

    Directory of Open Access Journals (Sweden)

    Garry Kuan

    2007-10-01

    Full Text Available This study examined the association between goal orientations and mental toughness and its influence on performance outcomes in competition. Wushu athletes (n = 40 competing in Intervarsity championships in Malaysia completed Task and Ego Orientations in Sport Questionnaire (TEOSQ and Psychological Performance Inventory (PPI. Using cluster analysis techniques including hierarchical methods and the non-hierarchical method (k-means cluster to examine goal profiles, a three cluster solution emerged viz. cluster 1 - high task and moderate ego (HT/ME, cluster 2 - moderate task and low ego (MT/LE and, cluster 3 - moderate task and moderate ego (MT/ME. Analysis of the fundamental areas of mental toughness based on goal profiles revealed that athletes in cluster 1 scored significantly higher on negative energy control than athletes in cluster 2. Further, athletes in cluster 1 also scored significantly higher on positive energy control than athletes in cluster 3. Chi-square (χ2 test revealed no significant differences among athletes with different goal profiles on performance outcomes in the competition. However, significant differences were observed between athletes (medallist and non medallist in self- confidence (p = 0.001 and negative energy control (p = 0.042. Medallist's scored significantly higher on self-confidence (mean = 21.82 ± 2.72 and negative energy control (mean = 19.59 ± 2.32 than the non-medallists (self confidence-mean = 18.76 ± 2.49; negative energy control mean = 18.14 ± 1.91.

  19. Use of TOUGH2 on small computers

    Energy Technology Data Exchange (ETDEWEB)

    Antunez, E.; Pruess, K.; Moridis, G. [Lawrence Berkeley Laboratory, CA (United States)

    1995-03-01

    TOUGH2/PC has been tested extensively on different PC platforms (486-33, 486-66, Pentium-90), with encouraging results. TOUGH2 performance has also been tested in other 32-bit computers as the MacIntosh Quadra 800, and a workstation IBM RISC 6000. Results obtained with these machines are compared with PCs` performance. PC results for 3-D geothermal reservoir models are discussed, including: (a) a Cartesian; and (b) a geothermal reservoir model with 1,411 irregular grid blocks. Also discussed are the results of the TOUGH2-compiler performance tests conducted on small computer systems. Code modifications required to operate on 32-bit computers and its setup in each machine environment are described. It is concluded that in today`s market PCs provide the best price/performance alternative to conduct TOUGH2 numerical simulations.

  20. Self-concept organisation and mental toughness in sport.

    Science.gov (United States)

    Meggs, Jennifer; Ditzfeld, Christopher; Golby, Jim

    2014-01-01

    The present study examines the relationship between individual differences in evaluative self-organisation and mental toughness in sport, proposing that motivation and emotional resiliency (facets of mental toughness) stem from differences in core self. A cross-sectional assessment of 105 athletes competing at a range of performance levels took part in an online study including measures of self-reported mental toughness (Sport Mental Toughness Questionnaire; Sheard, M., Golby, J., & van Wersch, A. (2009). Progress towards construct validation of the Sports Mental Toughness Questionnaire (SMTQ). European Journal of Psychological Assessment, 25(3), 186-193. doi:10.1027/1015-5759.25.3.186) and self-organisation (self-descriptive attribute task; Showers, C. J. (2002). Integration and compartmentalisation: A model of self-structure and self-change. In D. Cervone & W. Mischel (Eds.), Advances in personality science (pp. 271-291). New York, NY: Guilford Press). As predicted, global mental toughness was associated with self-concept positivity, which was particularly high in individuals with positive-integrative self-organisation (individuals who distribute positive and negative self-attributes evenly across multiple selves). Specifically, positive integration was associated with constancy (commitment to goal achievement despite obstacles and the potential for failure), which extends presumably from positive integratives' emotional stability and drive to resolve negative self-beliefs.

  1. The development and maintenance of mental toughness: perceptions of elite performers.

    Science.gov (United States)

    Connaughton, Declan; Wadey, Ross; Hanton, Sheldon; Jones, Graham

    2008-01-01

    Seven participants from a previous study (Jones, Hanton, & Connaughton, 2002) agreed to be interviewed about the development of mental toughness. We also aimed to determine whether mental toughness requires maintenance. Semistructured interviews were conducted to elicit the participants' perceptions of how mental toughness is cultivated and retained. Findings indicated that the development of mental toughness is a long-term process that encompasses a multitude of underlying mechanisms that operate in a combined, rather than independent, fashion. In general, these perceived underlying mechanisms related to many features associated with a motivational climate (e.g. enjoyment, mastery), various individuals (i.e. coaches, peers, parents, grandparents, siblings, senior athletes, sport psychologists, team-mates), experiences in and outside sport, psychological skills and strategies, and an insatiable desire and internalized motives to succeed. It was also reported that once mental toughness had been developed, three perceived underlying mechanisms were required to maintain this construct: a desire and motivation to succeed that was insatiable and internalized, a support network that included sporting and non-sporting personnel, and effective use of basic and advanced psychological skills. Practical implications and future avenues of research are discussed.

  2. The limit of strength and toughness of steel

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Zhen [Univ. of California, Berkeley, CA (United States)

    2001-12-01

    The ideal structural steel combines high strength with high fracture toughness. This dissertation discusses the governing principles of strength and toughness, along with the approaches that can be used to improve these properties and the inherent limits to how strong and tough a steel can be.

  3. MICROTOUGH - calculation of characteristic upper shelf fracture toughness values from microstructural parameters for high strength structural steels with normalized or quenched and tempered microstructure

    International Nuclear Information System (INIS)

    Muenstermann, S.; Dahl, W.; Langenberg, P.; Deimel, P.; Sattler, E.

    2004-01-01

    In modern applications, high strength steels are often utilised to increase the load bearing capacity of components. For safe design it is also necessary that these steels have an adequate fracture toughness. The mechanical properties of high strength structural steels are a result of the production process. In consequence, they are strongly related to the microstructure. Therefore, the aim of the research work in the Microtough project is to develop and apply a new method of quantitative correlation between microstructural parameters and characteristic fracture toughness values. This correlation will on the one hand help for the design of new structural steels with high toughness. On the other hand, it shall allow to characterise the fracture toughness of steel without performing expensive fracture mechanics tests. The research work is carried out in the full temperature range from lower to upper shelf. As both RWTH Aachen University and MPA Uni Stuttgart concentrate on ductile fracture behaviour in their research work, the focus of the presentation lies in the upper shelf. (orig.)

  4. TOUGH2 software qualification

    Energy Technology Data Exchange (ETDEWEB)

    Pruess, K.; Simmons, A.; Wu, Y.S.; Moridis, G.

    1996-02-01

    TOUGH2 is a numerical simulation code for multi-dimensional coupled fluid and heat flow of multiphase, multicomponent fluid mixtures in porous and fractured media. It belongs to the MULKOM ({open_quotes}MULti-KOMponent{close_quotes}) family of codes and is a more general version of the TOUGH simulator. The MULKOM family of codes was originally developed with a focus on geothermal reservoir simulation. They are suited to modeling systems which contain different fluid mixtures, with applications to flow problems arising in the context of high-level nuclear waste isolation, oil and gas recovery and storage, and groundwater resource protection. TOUGH2 is essentially a subset of MULKOM, consisting of a selection of the better tested and documented MULKOM program modules. The purpose of this package of reports is to provide all software baseline documents necessary for the software qualification of TOUGH2.

  5. TOUGH2 software qualification

    International Nuclear Information System (INIS)

    Pruess, K.; Simmons, A.; Wu, Y.S.; Moridis, G.

    1996-02-01

    TOUGH2 is a numerical simulation code for multi-dimensional coupled fluid and heat flow of multiphase, multicomponent fluid mixtures in porous and fractured media. It belongs to the MULKOM (open-quotes MULti-KOMponentclose quotes) family of codes and is a more general version of the TOUGH simulator. The MULKOM family of codes was originally developed with a focus on geothermal reservoir simulation. They are suited to modeling systems which contain different fluid mixtures, with applications to flow problems arising in the context of high-level nuclear waste isolation, oil and gas recovery and storage, and groundwater resource protection. TOUGH2 is essentially a subset of MULKOM, consisting of a selection of the better tested and documented MULKOM program modules. The purpose of this package of reports is to provide all software baseline documents necessary for the software qualification of TOUGH2

  6. Tough hybrid ceramic-based material with high strength

    International Nuclear Information System (INIS)

    Guo, Shuqi; Kagawa, Yutaka; Nishimura, Toshiyuki

    2012-01-01

    This study describes a tough and strong hybrid ceramic material consisting of platelet-like zirconium compounds and metal. A mixture of boron carbide and excess zirconium powder was heated to 1900 °C using a liquid-phase reaction sintering technique to produce a platelet-like ZrB 2 -based hybrid ceramic bonded by a thin zirconium layer. The platelet-like ZrB 2 grains were randomly present in the as-sintered hybrid ceramic. Relative to non-hybrid ceramics, the fracture toughness and flexural strength of the hybrid ceramic increased by approximately 2-fold.

  7. Microstructure and fracture toughness of Mn-stabilized cubic titanium trialuminide

    Science.gov (United States)

    Zbroniec, Leszek Ireneusz

    This thesis project is related to the fracture toughness aspects of the mechanical behavior of the selected Mn-modified cubic Ll2 titanium trialuminicles. Fracture toughness was evaluated using two specimen types: Single-Edge-Precracked-Beam (SEPB) and Chevron-Notched-Beam (CNB). The material tested was in cast, homogenized and HIP-ed condition. In the preliminary stage of the project due to lack of the ASTM Standard for fracture toughness testing of the chevron-notched specimens in bending the analyses of the CNB configuration were done to establish the optimal chevron notch dimensions. Two types of alloys were investigated: (a) boron-free and boron doped low-Mn (9at.% Mn), as well as (b) boron-free and boron-doped high-Mn (14at.% Mn). Toughness was investigated in the temperature range from room temperature to 1000°C and was calculated from the maximum load. It has been found that toughness of coarse-grained "base" 9Mn-25Ti alloy exhibits a broad peak at the 200--500°C temperature range and then decreases with increasing temperature, reaching its room temperature value at 10000°C. However, the work of fracture (gammaWOF) and the stress intensity factor calculated from it (KIWOF) increases continuously with increasing temperature. Also the fracture mode dependence on temperature has been established. To understand the effect of environment on the fracture toughness of coarse-grained "base", boron-free 9Mn-25Ti alloy, the tests were carried out in vacuum (˜1.3 x 10-5 Pa), argon, oxygen, water and liquid nitrogen. It has been shown that fracture toughness at ambient temperature is not affected by the environments containing moisture (water vapor). It seems that at ambient temperatures these materials are completely immune to the water-vapor hydrogen embrittlement and their cause of brittleness is other than environment. To explore the influence of the grain size on fracture toughness the fracture toughness tests were also performed on the dynamically

  8. High performance thermoplastics: A review of neat resin and composite properties

    Science.gov (United States)

    Johnston, Norman J.; Hergenrother, Paul M.

    1987-01-01

    A review was made of the principal thermoplastics used to fabricate high performance composites. Neat resin tensile and fracture toughness properties, glass transition temperatures (Tg), crystalline melt temperatures (Tm) and approximate processing conditions are presented. Mechanical properties of carbon fiber composites made from many of these thermoplastics are given, including flexural, longitudinal tensile, transverse tensile and in-plane shear properties as well as short beam shear and compressive strengths and interlaminar fracture toughness. Attractive features and problems involved in the use of thermo-plastics as matrices for high performance composites are discussed.

  9. Enhancements to the TOUGH2 Simulator as Implemented in iTOUGH2

    Energy Technology Data Exchange (ETDEWEB)

    Finsterle, Stefan [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2015-03-01

    iTOUGH2 is a program for parameter estimation, sensitivity analysis, and uncertainty propagation analysis. It is based on the TOUGH2 simulator for non-isothermal multiphase, multicomponent flow and transport in fractured and porous media [Pruess, 1987, 1991, 2005, 2011; Falta et al., 1995; Pruess et al., 1999, 2002, 2012; Doughty, 2013]. The core of iTOUGH2 contains slightly modified versions of TOUGH2 modules. Most code modifications are editorial and do not affect the simulation results. As a result, standard TOUGH2 input files can be used in iTOUGH2, and identical results are obtained if iTOUGH2 is run in forward mode. However, a number of modifications have been made as described in this report. They enhance the functionality, flexibilitu, and eas-of-use of the forward simulator. This report complements the reports iTOUGH2 User's Guide, iTOUGH2 Command Referecne, and the collection of tutorial examples in iTOUGH2 Sample Problems.

  10. Microstructural characteristics and toughness of the simulated coarse grained heat affected zone of high strength low carbon bainitic steel

    International Nuclear Information System (INIS)

    Lan Liangyun; Qiu Chunlin; Zhao Dewen; Gao Xiuhua; Du Linxiu

    2011-01-01

    Highlights: → Total toughness can be separated into crack initiation energy and crack propagation energy. → Small effective grain size of lath martensite can improve the crack propagation energy. → MA constituent is mainly responsible for the low toughness of coarse bainite specimens. → High angle packet boundary in coarser bainite has few contributions to improving crack propagation energy. - Abstract: The correlation of microstructural characteristics and toughness of the simulated coarse grained heat affected zone (CGHAZ) of low carbon bainitic steel was investigated in this study. The toughness of simulated specimens was examined by using an instrumented Charpy impact tester after the simulation welding test was conducted with different cooling times. Microstructure observation and crystallographic feature analysis were conducted by means of optical microscope and scanning electron microscope equipped with electron back scattered diffraction (EBSD) system, respectively. The main microstructure of simulated specimen changes from lath martensite to coarse bainite with the increase in cooling time. The deterioration of its toughness occurs when the cooling time ranges from 10 to 50 s compared with base metal toughness, and the toughness becomes even worse when the cooling time increases to 90 s or more. The MA (martensite-austenite) constituent is primary responsible for the low toughness of simulated CGHAZ with high values of cooling time because the large MA constituent reduces the crack initiation energy significantly. For crack propagation energy, the small effective grain size of lath martensite plays an important role in improving the crack propagation energy. By contrast, high misorientation packet boundary in coarse bainite seems to have few contributions to the improvement of the toughness because cleavage fracture micromechanism of coarse bainite is mainly controlled by crack initiation.

  11. Microstructural characteristics and toughness of the simulated coarse grained heat affected zone of high strength low carbon bainitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Lan Liangyun, E-mail: lly.liangyun@gmail.com [State Key Laboratory of Rolling Technology and Automation, Northeastern University, Shenyang 110819 (China); Qiu Chunlin; Zhao Dewen; Gao Xiuhua; Du Linxiu [State Key Laboratory of Rolling Technology and Automation, Northeastern University, Shenyang 110819 (China)

    2011-11-25

    Highlights: {yields} Total toughness can be separated into crack initiation energy and crack propagation energy. {yields} Small effective grain size of lath martensite can improve the crack propagation energy. {yields} MA constituent is mainly responsible for the low toughness of coarse bainite specimens. {yields} High angle packet boundary in coarser bainite has few contributions to improving crack propagation energy. - Abstract: The correlation of microstructural characteristics and toughness of the simulated coarse grained heat affected zone (CGHAZ) of low carbon bainitic steel was investigated in this study. The toughness of simulated specimens was examined by using an instrumented Charpy impact tester after the simulation welding test was conducted with different cooling times. Microstructure observation and crystallographic feature analysis were conducted by means of optical microscope and scanning electron microscope equipped with electron back scattered diffraction (EBSD) system, respectively. The main microstructure of simulated specimen changes from lath martensite to coarse bainite with the increase in cooling time. The deterioration of its toughness occurs when the cooling time ranges from 10 to 50 s compared with base metal toughness, and the toughness becomes even worse when the cooling time increases to 90 s or more. The MA (martensite-austenite) constituent is primary responsible for the low toughness of simulated CGHAZ with high values of cooling time because the large MA constituent reduces the crack initiation energy significantly. For crack propagation energy, the small effective grain size of lath martensite plays an important role in improving the crack propagation energy. By contrast, high misorientation packet boundary in coarse bainite seems to have few contributions to the improvement of the toughness because cleavage fracture micromechanism of coarse bainite is mainly controlled by crack initiation.

  12. Fracture Toughness of Ceramics Fired at Different Temperatures

    Directory of Open Access Journals (Sweden)

    Peter SIN

    2012-03-01

    Full Text Available The fracture toughness test was performed at room temperature on sets of 5 ceramic samples made from material for high voltage insulators (kaolin 36 wt. %, Al2O3 30 wt. %, clay 12 wt. % and feldspar 22 wt. % fired at temperatures 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1250, 1300, 1400, 1500 °C at heating and cooling rate of 5 °C/min. The precrack was made to each sample by indentation under the loads 10 N – 200 N, the dwell time was 45 s and the loading rate was 10 N/s. Results of the fracture toughness tests were in accordance with changes of structure of the samples after the partial firings. Fracture toughness from 20 °C to 500 °C is almost constant and it varies between 0.1 MPa·m0.5and 0.2 MPa·m0.5. Dehydroxylation (420 °C – 600 °C does not influence the value of fracture toughness. At temperature interval where we assume sintering (700 °C – 1250 °C we observe exponential dependence of fracture toughness up to 1.5 MPa·m0.5. From comparison of the fracture toughness, Young’s modulus and flexural strength follows a correlation and proporcionality of these mechanical properties.DOI: http://dx.doi.org/10.5755/j01.ms.18.1.1349

  13. Irradiation effects on fracture toughness of two high-copper submerged-arc welds, HSSI Series 5

    International Nuclear Information System (INIS)

    Nanstad, R.K.; Haggag, F.M.; McCabe, D.E.; Iskander, S.K.; Bowman, K.O.; Menke, B.H.

    1992-10-01

    The Fifth Irradiation Series in the Heavy-Section Steel Irradiation Program obtained a statistically significant fracture toughness data base on two high-copper (0.23 and 0.31 wt %) submerged-arc welds to determine the shift and shape of the K Ic curve as a consequence of irradiation. Compact specimens with thicknesses to 101.6 mm (4 in) in the irradiated condition and 203.2 mm (8 in) in the unirradiated condition were tested, in addition to Charpy impact, tensile, and drop-weight specimens. Irradiations were conducted at a nominal temperature of 288 degree C and an average fluence of 1.5 x 10 19 neutrons/cm 2 (>l MeV). The Charpy 41-J temperature shifts are about the same as the corresponding drop-weight NDT temperature shifts. The irradiated welds exhibited substantial numbers of cleavage pop-ins. Mean curve fits using two-parameter (with fixed intercept) nonlinear and linearized exponential regression analysis revealed that the fracture toughness 100 MPa lg-bullet √m shifts exceeded the Charpy 41-J shifts for both welds. Analyses of curve shape changes indicated decreases in the slopes of the fracture toughness curves, especially for the higher copper weld. Weibull analyses were performed to investigate development of lower bound curves to the data, including the use of a variable K min parameter which affects the curve shape

  14. SITA version 0. A simulation and code testing assistant for TOUGH2 and MARNIE

    Energy Technology Data Exchange (ETDEWEB)

    Seher, Holger; Navarro, Martin

    2016-06-15

    High quality standards have to be met by those numerical codes that are applied in long-term safety assessments for deep geological repositories for radioactive waste. The software environment SITA (''a simulation and code testing assistant for TOUGH2 and MARNIE'') has been developed by GRS in order to perform automated regression testing for the flow and transport simulators TOUGH2 and MARNIE. GRS uses the codes TOUGH2 and MARNIE in order to assess the performance of deep geological repositories for radioactive waste. With SITA, simulation results of TOUGH2 and MARNIE can be compared to analytical solutions and simulations results of other code versions. SITA uses data interfaces to operate with codes whose input and output depends on the code version. The present report is part of a wider GRS programme to assure and improve the quality of TOUGH2 and MARNIE. It addresses users as well as administrators of SITA.

  15. Effect of prestrain on ductility and toughness in high strength line pipe steels

    Energy Technology Data Exchange (ETDEWEB)

    Shinohara, Y.; Besson, J. [Paristech, Evry (France). Centre des Materiaux, Mines Paris; Madi, Y. [Ecole d' Ingenieurs, Sceaux (France). Ermess EPF; Paristech, Evry (France). Centre des Materiaux, Mines Paris

    2009-07-01

    The anisotropic plasticity, ductility and toughness of an X100 steel pipeline was investigated both before and after a series of prestraining experiments. The aim of the study was to determine the effect of prestraining on ductility and toughness in high strength pipe steels. Results of the study showed that primary void growth and coalescence was dependent on initial plastic anisotropy and not dependent on tensile prestrain. Secondary void nucleation and growth was not influenced by either the initial plastic anisotropy or by prestraining. Scanning electron microscopy (SEM) studies showed that the main damage mechanism was the void growth of primary dimples. Dimples in the prestrained materials were larger than those observed in materials that had not been prestrained. However, the effect on prestrain on dimple size was limited. Results showed both plastic and rupture anisotropies. It was concluded that prestraining induces a decrease in ductility, but has a significant impact on toughness. 4 refs., 2 tabs., 12 figs.

  16. Improvement of performance of ultra-high performance concrete based composite material added with nano materials

    Directory of Open Access Journals (Sweden)

    Pang Jinchang

    2016-03-01

    Full Text Available Ultra-high performance concrete (UHPC, a kind of composite material characterized by ultra high strength, high toughness and high durability. It has a wide application prospect in engineering practice. But there are some defects in concrete. How to improve strength and toughness of UHPC remains to be the target of researchers. To obtain UHPC with better performance, this study introduced nano-SiO2 and nano-CaCO3 into UHPC. Moreover, hydration heat analysis, X-Ray Diffraction (XRD, mercury intrusion porosimetry (MIP and nanoindentation tests were used to explore hydration process and microstructure. Double-doped nanomaterials can further enhance various mechanical performances of materials. Nano-SiO2 can promote early progress of cement hydration due to its high reaction activity and C-S-H gel generates when it reacts with cement hydration product Ca(OH2. Nano-CaCO3 mainly plays the role of crystal nucleus effect and filling effect. Under the combined action of the two, the composite structure is denser, which provides a way to improve the performance of UHPC in practical engineering.

  17. Developing Mental Toughness: Lessons from Paralympians

    Directory of Open Access Journals (Sweden)

    Alexander J. Powell

    2017-08-01

    Full Text Available Mental toughness (MT is a key psychological variable related to perseverance and success in performance domains. MT and its development has been explored across a range of contexts and across different sports, but no research to date has examined MT in relation to Paralympic athletes. We sought to understand the lived-experiences of mentally tough Paralympians, aiming to conceptualize MT in a Paralympic context and investigate its development. Ten Paralympic athletes were interviewed using in-depth, semi-structured interviews. The verbatim transcripts of the interviews served as the data for an interpretative phenomenological analysis. Three broad themes and several subthemes emerged in conceptualizing Paralympian MT: characteristics (determination, defiance, pragmatic, optimistic, resilient, self-belief and independence and autonomy, cognitions (normalization, sense of escape, non-acceptance of constraints, influence perception and connection and cognitive strategies (rational thinking, goal setting, pain management and control. In understanding MT development, two broad themes and several subthemes emerged: formative experiences (challenge, classification, setbacks, critical incident, trauma and recovery, sustained commitment, development of mind-set and perspective during challenge, failure, and acceptance, and support and coping resources (social support and significant others, external shaping, social support, overcoming problems, social comparison and reflective practice. The findings suggest that Paralympians benefited from exposure to highly demanding situations in a supportive environment and this helped develop mentally tough characteristics and behaviors and individualized cognitive coping strategies. Our findings highlight the association between the adaptive development of personal characteristics by overcoming physical and mental setbacks over a sustained time period. Overall, the findings suggest that to develop mentally tough

  18. Developing Mental Toughness: Lessons from Paralympians.

    Science.gov (United States)

    Powell, Alexander J; Myers, Tony D

    2017-01-01

    Mental toughness (MT) is a key psychological variable related to perseverance and success in performance domains. MT and its development has been explored across a range of contexts and across different sports, but no research to date has examined MT in relation to Paralympic athletes. We sought to understand the lived-experiences of mentally tough Paralympians, aiming to conceptualize MT in a Paralympic context and investigate its development. Ten Paralympic athletes were interviewed using in-depth, semi-structured interviews. The verbatim transcripts of the interviews served as the data for an interpretative phenomenological analysis. Three broad themes and several subthemes emerged in conceptualizing Paralympian MT: characteristics (determination, defiance, pragmatic, optimistic, resilient, self-belief and independence and autonomy), cognitions (normalization, sense of escape, non-acceptance of constraints, influence perception and connection) and cognitive strategies (rational thinking, goal setting, pain management and control). In understanding MT development, two broad themes and several subthemes emerged: formative experiences (challenge, classification, setbacks, critical incident, trauma and recovery, sustained commitment, development of mind-set and perspective during challenge, failure, and acceptance), and support and coping resources (social support and significant others, external shaping, social support, overcoming problems, social comparison and reflective practice). The findings suggest that Paralympians benefited from exposure to highly demanding situations in a supportive environment and this helped develop mentally tough characteristics and behaviors and individualized cognitive coping strategies. Our findings highlight the association between the adaptive development of personal characteristics by overcoming physical and mental setbacks over a sustained time period. Overall, the findings suggest that to develop mentally tough characteristics

  19. Use of Synergistic Interactions to Fabricate Strong, Tough, and Conductive Artificial Nacre Based on Graphene Oxide and Chitosan.

    Science.gov (United States)

    Wan, Sijie; Peng, Jingsong; Li, Yuchen; Hu, Han; Jiang, Lei; Cheng, Qunfeng

    2015-10-27

    Graphene is the strongest and stiffest material, leading to the development of promising applications in many fields. However, the assembly of graphene nanosheets into macrosized nanocomposites for practical applications remains a challenge. Nacre in its natural form sets the "gold standard" for toughness and strength, which serves as a guide to the assembly of graphene nanosheets into high-performance nanocomposites. Here we show the strong, tough, conductive artificial nacre based on graphene oxide through synergistic interactions of hydrogen and covalent bonding. Tensile strength and toughness was 4 and 10 times higher, respectively, than that of natural nacre. The exceptional integrated strong and tough artificial nacre has promising applications in aerospace, artificial muscle, and tissue engineering, especially for flexible supercapacitor electrodes due to its high electrical conductivity. The use of synergistic interactions is a strategy for the development of high-performance nanocomposites.

  20. Fracture toughness properties of similar and dissimilar electron beam welds

    International Nuclear Information System (INIS)

    Kocak, M.; Junghans, E.

    1994-01-01

    The weldability aspects, tensile and Crack Tip Opening Displacement (CTOD) toughness properties of 9Cr1MoNbV (P91) martensitic steel with austenitic 316L steel were evaluated for electron beam (EB) welds on 35 mm thick pates. The effects of mechanical heterogeneity (mis-matching) at the vicinity of the crack tip of dissimilar three point bend specimens on the CTOD fracture toughness values was also discussed. The CTOD tests were performed on similar and dissimilar EB welds of austenitic and tempered martensitic P91 steels at room temperature. Dilution of austenitic with martensitic steel resulted in predominantly martensitic EB weld metal, exhibiting rather high yield strength and hardness. Nevertheless, the weld metal produced high CTOD toughness values due to the beneficial effect of the lower strength austenitic steel part of the specimen in which crack deviation occured (mis-match effect). The coarse grained HAZ of the P91 steel side exhibits extremely poor CTOD toughness properties in the as-welded condition at room temperature. The CTOD values obtained are believed to be representing the intrinsic property of this zone since the distance of the crack tip to the weaker austenitic steel part of the SENB specimens was too large to cause an effective stress relaxation at the crack tip. Further post weld heat treatment at 750 C for two hours improved the CTOD toughness marginally. (orig.)

  1. Microstructure, Composition, and Impact Toughness Across the Fusion Line of High-Strength Bainitic Steel Weldments

    Science.gov (United States)

    Lan, Liangyun; Kong, Xiangwei; Chang, Zhiyuan; Qiu, Chunlin; Zhao, Dewen

    2017-09-01

    This paper analyzed the evolution of microstructure, composition, and impact toughness across the fusion line of high-strength bainitic steel weldments with different heat inputs. The main purpose was to develop a convenient method to evaluate the HAZ toughness quickly. The compositions of HAZ were insensitive to higher contents of alloy elements ( e.g., Ni, Mo) in the weld metal because their diffusion distance is very short into the HAZ. The weld metal contained predominantly acicular ferrite at any a heat input, whereas the main microstructures in the HAZ changed from lath martensite/bainite to upper bainite with the increasing heat input. The evolution of HAZ toughness in relation to microstructural changes can be revealed clearly combined with the impact load curve and fracture morphology, although the results of impact tests do not show an obvious change with heat input because the position of Charpy V notch contains the weld metal, HAZ as well as a part of base metal. As a result, based on the bead-on-plate welding tests, the welding parameter affecting the HAZ toughness can be evaluated rapidly.

  2. Veins improve fracture toughness of insect wings.

    Directory of Open Access Journals (Sweden)

    Jan-Henning Dirks

    Full Text Available During the lifetime of a flying insect, its wings are subjected to mechanical forces and deformations for millions of cycles. Defects in the micrometre thin membranes or veins may reduce the insect's flight performance. How do insects prevent crack related material failure in their wings and what role does the characteristic vein pattern play? Fracture toughness is a parameter, which characterises a material's resistance to crack propagation. Our results show that, compared to other body parts, the hind wing membrane of the migratory locust S. gregaria itself is not exceptionally tough (1.04±0.25 MPa√m. However, the cross veins increase the wing's toughness by 50% by acting as barriers to crack propagation. Using fracture mechanics, we show that the morphological spacing of most wing veins matches the critical crack length of the material (1132 µm. This finding directly demonstrates how the biomechanical properties and the morphology of locust wings are functionally correlated in locusts, providing a mechanically 'optimal' solution with high toughness and low weight. The vein pattern found in insect wings thus might inspire the design of more durable and lightweight artificial 'venous' wings for micro-air-vehicles. Using the vein spacing as indicator, our approach might also provide a basis to estimate the wing properties of endangered or extinct insect species.

  3. Fracture Toughness and Fatigue Crack Growth Behavior of As-Cast High-Entropy Alloys

    Science.gov (United States)

    Seifi, Mohsen; Li, Dongyue; Yong, Zhang; Liaw, Peter K.; Lewandowski, John J.

    2015-08-01

    The fracture toughness and fatigue crack growth behavior of two as-vacuum arc cast high-entropy alloys (HEAs) (Al0.2CrFeNiTi0.2 and AlCrFeNi2Cu) were determined. A microstructure examination of both HEA alloys revealed a two-phase structure consisting of body-centered cubic (bcc) and face-centered cubic (fcc) phases. The notched and fatigue precracked toughness values were in the range of those reported in the literature for two-phase alloys but significantly less than recent reports on a single phase fcc-HEA that was deformation processed. Fatigue crack growth experiments revealed high fatigue thresholds that decreased significantly with an increase in load ratio, while Paris law slopes exhibited metallic-like behavior at low R with significant increases at high R. Fracture surface examinations revealed combinations of brittle and ductile/dimpled regions at overload, with some evidence of fatigue striations in the Paris law regime.

  4. Toughness testing and high-temperature oxidation evaluations of advanced alloys for core internals

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Lizhen [ORNL; Pint, Bruce A [ORNL; Chen, Xiang [ORNL

    2016-09-16

    Alloy X-750 was procured from Carpenter Technology and Bodycote in this year. An appropriate TMT was developed on Alloy 439 to obtain materials with refined grain size for property screening tests. Charpy V-notch impact tests were completed for the three ferritic steels Grade 92, Alloy 439, and 14YWT. Fracture toughness tests at elevated temperatures were completed for 14YWT. The tests will be completed for the other alloys in next fiscal year. Steam oxidation tests of the three ferritic steels, 316L, and Zr–2.5Nb have been completed. The steam tests of the Ni-based superalloys and the other austenitic stainless steels will be continued and finished in next fiscal year. Performance ranking in terms of steam oxidation resistance and impact/fracture toughness of the alloys will be deduced.

  5. Analysis of tensile and fracture toughness results on irradiated molybdenum alloys, TZM and Mo-5%Re. Analysis of results performed in the frame of the NET task PDS 1.4

    Energy Technology Data Exchange (ETDEWEB)

    Scibetta, M.; Chaouadi, R.; Puzzolante, J.L

    1999-10-01

    Due to their good resistance at high temperature, good thermal conductivity and swelling resistance, molybdenum alloys are considered amongst the candidates for divertor structural materials. However, little is known about their tensile and fracture toughness behaviour, in particular after irradiation. This report aims to investigate the tensile and fracture toughness properties of two molybdenum alloys, namely TZM and Mo-5%Re. Tensile and compact tension specimens were irradiated in the BR2 reactor at 40 and 450 degrees Celsius up to a fast neutron fluence of 3.5 1020 n/cm{sup 2} (0.2 dpa). Fracture toughness tests were performed on both precracked and notched specimens. Results show a drastic decrease of the ductility due to irradiation, but only a slight decrease of the fracture toughness in the lower shelf domain.

  6. Analysis of tensile and fracture toughness results on irradiated molybdenum alloys, TZM and Mo-5%Re. Analysis of results performed in the frame of the NET task PDS 1.4

    International Nuclear Information System (INIS)

    Scibetta, M.; Chaouadi, R.; Puzzolante, J.L.

    1999-10-01

    Due to their good resistance at high temperature, good thermal conductivity and swelling resistance, molybdenum alloys are considered amongst the candidates for divertor structural materials. However, little is known about their tensile and fracture toughness behaviour, in particular after irradiation. This report aims to investigate the tensile and fracture toughness properties of two molybdenum alloys, namely TZM and Mo-5%Re. Tensile and compact tension specimens were irradiated in the BR2 reactor at 40 and 450 degrees Celsius up to a fast neutron fluence of 3.5 1020 n/cm 2 (0.2 dpa). Fracture toughness tests were performed on both precracked and notched specimens. Results show a drastic decrease of the ductility due to irradiation, but only a slight decrease of the fracture toughness in the lower shelf domain

  7. Fracture toughness evaluation of Eurofer'97 by testing small specimens

    International Nuclear Information System (INIS)

    Serrano, M.; Fernandez, P.; Lapena, J.

    2006-01-01

    The Eurofer'97 is the structural reference material that will be tested in the ITER modules. Its metallurgical properties have been well characterized during the last years. However, more investigations related with the fracture toughness of this material are necessary because this property is one of the most important to design structural components and to study their integrity assessment. In the case of structural materials for fusion reactor the small specimen technology (SSTT) are being actively developed to investigate the fracture toughness among other mechanical properties. The use of small specimens is due to the small available irradiation volume of IFMIF and also due to the high fluence expected in the fusion reactor. The aim of this paper is to determine the fracture toughness of the Eurofer'97 steel by testing small specimens of different geometry in the ductile to brittle transition region, with the application of the Master Curve methodology, and to evaluate this method to assess the decrease in fracture toughness due to neutron irradiation. The tests and data analysis have been performed following the Master Curve approach included in the ASTM Standard E1921-05. Specimen size effect and comparison of the fracture toughness results with data available in the literature are also considered. (author)

  8. High performance thermoplastics - A review of neat resin and composite properties

    Science.gov (United States)

    Johnston, Norman J.; Hergenrother, Paul M.

    1987-01-01

    A review was made of the principal thermoplastics used to fabricate high performance composites. Neat resin tensile and fracture toughness properties, glass transition temperatures (Tg), crystalline melt temperatures (Tm) and approximate processing conditions are presented. Mechanical properties of carbon fiber composites made from many of these thermoplastics are given, including flexural, longitudinal tensile, transverse tensile and in-plane shear properties as well as short beam shear and compressive strengths and interlaminar fracture toughness.

  9. Strong, tough and stiff bioinspired ceramics from brittle constituents

    Science.gov (United States)

    Bouville, Florian; Maire, Eric; Meille, Sylvain; van de Moortèle, Bertrand; Stevenson, Adam J.; Deville, Sylvain

    2014-05-01

    High strength and high toughness are usually mutually exclusive in engineering materials. In ceramics, improving toughness usually relies on the introduction of a metallic or polymeric ductile phase, but this decreases the material’s strength and stiffness as well as its high-temperature stability. Although natural materials that are both strong and tough rely on a combination of mechanisms operating at different length scales, the relevant structures have been extremely difficult to replicate. Here, we report a bioinspired approach based on widespread ceramic processing techniques for the fabrication of bulk ceramics without a ductile phase and with a unique combination of high strength (470 MPa), high toughness (22 MPa m1/2), and high stiffness (290 GPa). Because only mineral constituents are needed, these ceramics retain their mechanical properties at high temperatures (600 °C). Our bioinspired, material-independent approach should find uses in the design and processing of materials for structural, transportation and energy-related applications.

  10. Fracture toughness of manet II steel

    International Nuclear Information System (INIS)

    Gboneim, M.M.; Munz, D.

    1997-01-01

    High fracture toughness was evaluated according to the astm and chromium (9-12) martensitic steels combine high strength and toughness with good corrosion and oxidation resistance in a range of environments, and also show relatively high creep strength at intermediate temperatures. They therefore find applications in, for example, the offshore oil and gas production and chemical industries i pipe work and reaction vessels, and in high temperature steam plant in power generation systems. Recently, the use of these materials in the nuclear field was considered. They are candidates as tubing materials for breeder reactor steam generators and as structural materials for the first wall and blanket in fusion reactors. The effect of ageing on the tensile properties and fracture toughness of a 12 Cr-1 Mo-Nb-v steel, MANET II, was investigated in the present work. Tensile specimens and compact tension (CT) specimens were aged at 550 degree C for 1000 h. The japanese standards. Both microstructure and fracture surface were examined using optical and scanning electron microscopy (SEM). The results showed that ageing did not affect the tensile properties. However, the fracture toughness K Ic and the tearing modules T were reduced due to the ageing treatment. The results were discussed in the light of the chemical composition and the fracture surface morphology. 9 figs., 3 tabs

  11. Development of fracture toughness test method for nuclear grade graphite

    Energy Technology Data Exchange (ETDEWEB)

    Chang, C. H.; Lee, J. S.; Cho, H. C.; Kim, D. J.; Lee, D. J. [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2006-02-15

    Because of its high strength and stability at very high temperature, as well as very low thermal neutron absorption cross-section, graphite has been widely used as a structural material in Gas Cooled Reactors (GCR). Recently, many countries are developing the Very High Temperature gas cooled Reactor (VHTR) because of the potentials of hydrogen production, as well as its safety and viable economics. In VHTR, helium gas serves as the primary coolant. Graphite will be used as a reflector, moderator and core structural materials. The life time of graphite is determined from dimensional changes due to neutron irradiation, which closely relates to the changes of crystal structure. The changes of both lattice parameter and crystallite size can be easily measured by X-ray diffraction method. However, due to high cost and long time of neutron irradiation test, ion irradiation test is being performed instead in KAERI. Therefore, it is essential to develop the technique for measurement of ion irradiation damage of nuclear graphite. Fracture toughness of nuclear grade graphite is one of the key properties in the design and development of VHTR. It is important not only to evaluate the various properties of candidate graphite but also to assess the integrity of nuclear grade graphite during operation. Although fracture toughness tests on graphite have been performed in many laboratories, there have been wide variations in values of the calculated fracture toughness, due to the differences in the geometry of specimens and test conditions. Hence, standard test method for nuclear graphite is required to obtain the reliable fracture toughness values. Crack growth behavior of nuclear grade graphite shows rising R-curve which means the increase in crack growth resistance as the crack length increases. Crack bridging and microcracking have been proposed to be the dominant mechanisms of rising R-curve behavior. In this paper, the technique to measure the changes of crystallite size and

  12. Highly tough and transparent layered composites of nanocellulose and synthetic silicate

    Science.gov (United States)

    Wu, Chun-Nan; Yang, Quanling; Takeuchi, Miyuki; Saito, Tsuguyuki; Isogai, Akira

    2013-12-01

    A highly tough and transparent film material was prepared from synthetic saponite (SPN) nanoplatelets of low aspect ratios and nanofibrillar cellulose. The nanofibrillar cellulose was chemically modified by topological surface oxidation using 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) as a catalyst. Both synthetic SPN nanoplatelets and TEMPO-oxidized cellulose nanofibrils (TOCNs) have abundant negative charges in high densities on their surfaces and are dispersed in water at the individual nanoelement level. Layered nanocomposite structures of the SPN nanoplatelets and TOCNs were formed through a simple cast-drying process of the mixed aqueous dispersions. The TOCN/SPN composites with 0-50% w/w SPN content were optically transparent. Mechanical properties of the TOCN/SPN composites varied depending on the SPN content. The composite with 10% w/w SPN content (5.6% volume fraction) exhibited characteristic mechanical properties: Young's modulus of 14 GPa, tensile strength of 420 MPa, and strain-to-failure of 10%. The work of fracture of the composites increased from 4 to 30 MJ m-3 - or by more than 700% - as the SPN content was increased from 0 to 10% w/w. This surprising improvement in toughness was interpreted based on a model for fracture of polymer composites reinforced with low-aspect-ratio platelets.A highly tough and transparent film material was prepared from synthetic saponite (SPN) nanoplatelets of low aspect ratios and nanofibrillar cellulose. The nanofibrillar cellulose was chemically modified by topological surface oxidation using 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) as a catalyst. Both synthetic SPN nanoplatelets and TEMPO-oxidized cellulose nanofibrils (TOCNs) have abundant negative charges in high densities on their surfaces and are dispersed in water at the individual nanoelement level. Layered nanocomposite structures of the SPN nanoplatelets and TOCNs were formed through a simple cast-drying process of the mixed aqueous dispersions. The

  13. Fracture toughness measurements with subsize disk compact specimens

    International Nuclear Information System (INIS)

    Alexander, D.J.

    1994-01-01

    Special fixtures and test methods have been developed for testing small disk compact specimens (1.25 mm diam by 4.6 mm thick). Specimens of European type 316L austenitic stainless steel were irradiated to damage levels of about 3 dpa at nominal irradiation temperatures of either 90 or 250 C and tested over a temperature range from 20 to 250 C. Results show that irradiation to this dose level at these temperatures reduces the fracture toughness but the toughness remains quite high. The toughness decreases as the test temperature increases. Irradiation at 250 C is more damaging than at 90 C, causing larger decreases in the fracture toughness. The testing shows that it is possible to generate useful fracture toughness data with a small disk compact specimens

  14. Effect of weld metal toughness on fracture behavior under ultra-low cycle fatigue loading (earthquake)

    Energy Technology Data Exchange (ETDEWEB)

    Kermajani, M. [School of Materials Engineering, College of Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Ghaini, F. Malek, E-mail: Fmalek@modares.ac.ir [School of Materials Engineering, College of Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Miresmaeili, R. [School of Materials Engineering, College of Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Aghakouchak, A.A. [School of Civil Engineering, College of Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Shadmand, M. [Department of Research and Development, MAPNA Electric and Control (MECO) Company, Karaj (Iran, Islamic Republic of)

    2016-06-21

    Results from 12 ultra-low cycle fatigue tests performed on the weld metals of both toughness and non-toughness rated grades are presented. Fracture resistance under these loadings seemed to be dependent on materials' toughness, displacement amplitude, and stress state triaxiality, while the toughness effect was more highlighted at high stress levels and concentrations. To study the effect of microstructures on these failures, supporting ancillary tests including all-weld tension coupons, Charpy V-notched impact tests, and optical and scanning electron microscope analyses were performed. The favored microstructures appeared to be those which absorbed energy by plastic deformation and, hence, hindered void formation and/or could avoid crack propagation by deflection. Considering the response of the tested materials to cyclic loadings and the requirements of the materials specified in AISC341 Provisions could question the adequacy of these requirements for weld metals. However, the role of microstructural features like inclusions would be the same in both the Charpy impact tests and ultra-low cycle loadings.

  15. Shallow-crack toughness results for reactor pressure vessel steel

    International Nuclear Information System (INIS)

    Theiss, T.J.; Shum, D.K.M.; Rolfe, S.T.

    1992-01-01

    The Heavy Section Steel Technology Program (HSST) is investigating the influence of flaw depth on the fracture toughness of reactor pressure vessel (RPV) steel. To complete this investigation, techniques were developed to determine the fracture toughness from shallow-crack specimens. A total of 38 deep and shallow-crack tests have been performed on beam specimens about 100 mm deep loaded in 3-point bending. Two crack depths (a ∼ 50 and 9 mm) and three beam thicknesses (B ∼ 50, 100, and 150 mm) have been tested. Techniques were developed to estimate the toughness in terms of both the J-integral and crack-tip opening displacement (CTOD). Analytical J-integral results were consistent with experimental J-integral results, confirming the validity of the J-estimation schemes used and the effect of flaw depth on fracture toughness. Test results indicate a significant increase in the fracture toughness associated with the shallow flaw specimens in the lower transition region compared to the deep-crack fracture toughness. There is, however, little or no difference in toughness on the lower shelf where linear-elastic conditions exist for specimens with either deep or shallow flaws. The increase in shallow-flaw toughness compared with deep-flaw results appears to be well characterized by a temperature shift of 35 degree C

  16. Fracture toughness evaluation of circumferentially-cracked round bars

    International Nuclear Information System (INIS)

    Scibetta, M.

    1996-05-01

    The measure of the fracture toughness of a circumferentially-cracked round bar is generally performed through approximate formulae. Comparison of existing formulae to finite element results does not always show good agreement. Therefore an eta factor is introduced in order to improve the existing analytical formula. The axisymmetrical geometry is generally considered to be a high constrained geometry. Finite element calculations are performed to verify and quantify the constraint relative to the three point bending configuration (precracked Charpy)

  17. Lanthanum additions and the toughness of ultra-high strength steels and the determination of appropriate lanthanum additions

    International Nuclear Information System (INIS)

    Garrison, Warren M.; Maloney, James L.

    2005-01-01

    Studies of commercial heats of AF1410 steel suggest that under appropriate conditions additions of rare-earth elements can significantly enhance fracture toughness. This improvement in toughness is not due to an extremely low inclusion volume fraction but is apparently due to the formation of larger and more widely spaced inclusions. The purpose of this work is to discuss our experience in using rare-earth additions to laboratory scale vacuum induction melted and subsequently vacuum arc remelted heats of ultra-high strength steels to achieve inclusion distributions similar to those observed in commercial heats modified with lanthanum additions. The results indicate that lanthanum additions of 0.015 wt.% to low sulfur steels which have been well deoxidized using carbon-vacuum deoxidation can result in lanthanum rich inclusions which are similar in size, volume fraction and spacing to those obtained in commercially produced heats of ultra-high strength steel to which lanthanum has been added. The heat of steel to which lanthanum additions of 0.015 wt.% were made had significantly higher toughness than did the heat of the same steel in which the sulfur had been gettered as small and closely spaced particles of MnS and which had an inclusion volume fraction similar to that of the heat modified by the addition of 0.015 wt.% lanthanum. This improvement in toughness was attributed to an increase in inclusion spacing. An addition of 0.06 wt.% lanthanum was excessive. Such an addition of lanthanum resulted in a huge volume fraction of large cuboidal inclusions which primarily contain lanthanum and oxygen and which are extremely detrimental to toughness

  18. Probabilistic fracture mechanics analysis of reactor vessels with low upper-shelf fracture toughness

    International Nuclear Information System (INIS)

    Yoon, K.K.

    1993-01-01

    A class of submerged-arc welds used in fabricating early reactor vessels has relatively high copper contents. Studies have shown that when such vessels are irradiated, the copper contributes to lowering the Charpy upper-shelf energy level. To address this concern, 10CFR50, Appendix G requires a fracture mechanics analysis to demonstrate an adequate margin of safety for continued service. The B and W Owners Group (B and WOG) has been accumulating J-resistance fracture toughness data for these weld metals. Based on a mathematical model derived from this B and WOG data base, the first Appendix G analysis was performed. Another important issue affecting reactor vessel integrity is pressurized thermal shock (PIS) transients. In the early 1980s, probabilistic fracture mechanics analyses were performed on a reactor vessel to determine the probability of failure under postulated accident scenarios. Results of such analyses were used by the Nuclear Regulatory Commission (NRC) to establish the screening criteria for assessing reactor vessel integrity under PTS transient loads. This paper addresses the effect of low upper-shelf toughness on the probability of failure of reactor vessels under PTS loads. Probabilistic fracture mechanics codes were modified to include the low upper-shelf toughness model used in a reference and a series of analyses was performed using plant-specific material conditions and realistic PTS scenarios. The results indicate that low upper-shelf toughness has an insignificant effect on the probability of reactor vessel failures. This is mostly due to PTS transients being susceptible to crack initiation at low temperatures and not affected by upper-shelf fracture toughness

  19. Fracture toughness shifts in high-copper weldments (series 5 and 6)

    International Nuclear Information System (INIS)

    Iskander, S.K.

    1995-01-01

    The specific activities to be performed in this task are the: (1) continuation of Phase 2 of the Fifth Irradiation Series, and (2) completion of the Sixth Irradiation Series, including testing nine irradiated Italian crack-arrest specimens. The test results of the Italian crack-arrest specimens are being analyzed, and full details will be published in a NUREG report currently in preparation. The crack-mouth opening displacement (CMOD) was measured at a distance greater than that prescribed in the American Society for Testing and Materials (ASTM) open-quotes Test for Determining Plane-Strain Crack-Arrest Fracture Toughness, K la , of Ferritic Steelsclose quotes (E 1221-88). A method for adjusting the CMOD to account for this has been developed and is presented. The correction was ∼4% for small specimens and ∼2% for the larger ones. As part of this task, irradiation of HSSI weld 73W to a high fluence [5 x 10 19 neutrons/cm 2 ( > 1 MeV)] will be performed to determine whether the K Jc curve shape change observed in the Fifth HSSI Series is exacerbated. The design and fabrication of the temperature and dosimetry verification capsules are performed under this task, but for purposes of continuity, their progress will be reported under Task 6, where the design of the new irradiation facilities and capsules is performed

  20. Finite Element Simulation of Fracture Toughness Test

    International Nuclear Information System (INIS)

    Chu, Seok Jae; Liu, Cong Hao

    2013-01-01

    Finite element simulations of tensile tests were performed to determine the equivalent stress - equivalent plastic strain curves, critical equivalent stresses, and critical equivalent plastic strains. Then, the curves were used as inputs to finite element simulations of fracture toughness tests to determine the plane strain fracture toughness. The critical COD was taken as the COD when the equivalent plastic strain at the crack tip reached a critical value, and it was used as a crack growth criterion. The relationship between the critical COD and the critical equivalent plastic strain or the reduction of area was found. The relationship between the plane strain fracture toughness and the product of the critical equivalent stress and the critical equivalent plastic strain was also found

  1. iTOUGH2 Universal Optimization Using the PEST Protocol

    International Nuclear Information System (INIS)

    Finsterle, S.A.

    2010-01-01

    iTOUGH2 (http://www-esd.lbl.gov/iTOUGH2) is a computer program for parameter estimation, sensitivity analysis, and uncertainty propagation analysis [Finsterle, 2007a, b, c]. iTOUGH2 contains a number of local and global minimization algorithms for automatic calibration of a model against measured data, or for the solution of other, more general optimization problems (see, for example, Finsterle [2005]). A detailed residual and estimation uncertainty analysis is conducted to assess the inversion results. Moreover, iTOUGH2 can be used to perform a formal sensitivity analysis, or to conduct Monte Carlo simulations for the examination for prediction uncertainties. iTOUGH2's capabilities are continually enhanced. As the name implies, iTOUGH2 is developed for use in conjunction with the TOUGH2 forward simulator for nonisothermal multiphase flow in porous and fractured media [Pruess, 1991]. However, iTOUGH2 provides FORTRAN interfaces for the estimation of user-specified parameters (see subroutine USERPAR) based on user-specified observations (see subroutine USEROBS). These user interfaces can be invoked to add new parameter or observation types to the standard set provided in iTOUGH2. They can also be linked to non-TOUGH2 models, i.e., iTOUGH2 can be used as a universal optimization code, similar to other model-independent, nonlinear parameter estimation packages such as PEST [Doherty, 2008] or UCODE [Poeter and Hill, 1998]. However, to make iTOUGH2's optimization capabilities available for use with an external code, the user is required to write some FORTRAN code that provides the link between the iTOUGH2 parameter vector and the input parameters of the external code, and between the output variables of the external code and the iTOUGH2 observation vector. While allowing for maximum flexibility, the coding requirement of this approach limits its applicability to those users with FORTRAN coding knowledge. To make iTOUGH2 capabilities accessible to many application models

  2. A-TOUGH: A multimedia fluid-flow/energy-transport model for fully- coupled atmospheric-subsurface interactions

    International Nuclear Information System (INIS)

    Montazer, P.; Hammermeister, D.; Ginanni, J.

    1994-01-01

    The long-term effect of changes in atmospheric climatological conditions on subsurface hydrological conditions in the unsaturated zone in and environments is an important factor in defining the performance of a high-level and low-level radioactive waste repositories in geological environment. Computer simulation coupled with paleohydrological studies can be used to understand and quantify the potential impact of future climatological conditions on repository performance. A-TOUGH efficiently simulates (given current state-of-the-art technology) the physical processes involved in the near-surface atmosphere and its effect on subsurface conditions. This efficiency is due to the numerical techniques used in TOUGH and the efficient computational techniques used in V-TOUGH to solve non-linear thermodynamic equations that govern the flux of vapor and energy within subsurface porous and fractured media and between these media and the atmosphere

  3. Tensile toughness test and high temperature fracture analysis of thermal barrier coatings

    International Nuclear Information System (INIS)

    Qian, G.; Nakamura, T.; Berndt, C.C.; Leigh, S.H.

    1997-01-01

    In this paper, an effective fracture toughness test which uses interface fracture mechanics theory is introduced. This method is ideally suited for determining fracture resistance of multilayered thermal barrier coatings (TBCs) consisting of ceramic and bond layers and, unlike other fracture experiments, requires minimal set-up over a simple tensile adhesion test. Furthermore, while other test methods usually use edge cracked specimens, the present test models a crack embedded within the coatings, which is more consistent with actual TBCs where failure initiates from internal voids or defects. The results of combined computational and experimental analysis show that any defects located within the ceramic coating can significantly weaken a TBC, whereas the debonding resistances of the bond coating and its interfaces are found to be much higher. In a separate analysis, the authors have studied fracture behavior of TBCs subjected to thermal loading in a high temperature environment. The computed fracture parameters reveal that when the embedded crack size is on order of the coating thickness, the fracture driving force is comparable to the fracture resistance of the coating found in the toughness test. In addition, the major driving force for fracture derives from the thermal insulating effect across the crack faces rather than the mismatch in the coefficients of thermal expansion. The authors have also investigated the effects of functionally graded material (FGM) within TBCs and found its influences on the fracture parameters to be small. This result implies that the FGM may not contribute toward enhancing the fracture toughness of the TBCs considered here

  4. Graphical user interface for TOUGH/TOUGH2 - development of database, pre-processor, and post-processor

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Tatsuya; Okabe, Takashi; Osato, Kazumi [Geothermal Energy Research and Development Co., Ltd., Tokyo (Japan)

    1995-03-01

    One of the advantages of the TOUGH/TOUGH2 (Pruess, 1987 and 1991) is the modeling using {open_quotes}free shape{close_quotes} polygonal blocks. However, the treatment of three-dimensional information, particularly for TOUGH/TOUGH2 is not easy because of the {open_quotes}free shape{close_quotes} polygonal blocks. Therefore, we have developed a database named {open_quotes}GEOBASE{close_quotes} and a pre/post-processor named {open_quotes}GEOGRAPH{close_quotes} for TOUGH/TOUGH2 on engineering work station (EWS). {open_quotes}GEOGRAPH{close_quotes} is based on the ORACLE{sup *1} relational database manager system to access data sets of surface exploration (geology, geophysics, geochemistry, etc.), drilling (well trajectory, geological column, logging, etc.), well testing (production test, injection test, interference test, tracer test, etc.) and production/injection history.{open_quotes}GEOGRAPH{close_quotes} consists of {open_quotes}Pre-processor{close_quotes} that can construct the three-dimensional free shape reservoir modeling by mouse operation on X-window and {open_quotes}Post-processor{close_quotes} that can display several kinds of two/three-dimensional maps and X-Y plots to compile data on {open_quotes}GEOBASE{close_quotes} and result of TOUGH/TOUGH2 calculation. This paper shows concept of the systems and examples of utilization.

  5. Mental Toughness in Education: Exploring Relationships with Attainment, Attendance, Behaviour and Peer Relationships

    Science.gov (United States)

    St Clair-Thompson, Helen; Bugler, Myfanwy; Robinson, Jamey; Clough, Peter; McGeown, Sarah P.; Perry, John

    2015-01-01

    Mental toughness has frequently been associated with successful performance in sport; however, recent research suggests that it may also be related to academic performance in Higher Education. In a series of three exploratory studies, we examined the relationship between mental toughness and different aspects of educational performance in…

  6. Fracture toughness prediction for RPV Steels with various degree of embrittlement

    International Nuclear Information System (INIS)

    Margolin, B.; Gulenko, A.; Shvetsova, V.

    2003-01-01

    In the present report, predictions of the temperature dependence of cleavage fracture toughness are performed on the basis of the Master Curve approach and a probabilistic model named now the Prometey model. These predictions are performed for reactor pressure vessel steels in different states, the initial (as-produced), irradiated state with moderate degree of embrittlement and in the highly embrittled state. Calculations of the K IC (T) curves may be performed with both approaches on the basis of fracture toughness test results from pre-cracked Charpy specimens at some (one) temperature. The calculated curves are compared with test results. It is shown that the K IC (T) curves for the initial state calculated with the Master Curve approach and the probabilistic model show good agreement. At the same time, for highly embrittled RPV steel, the K IC (T) curve predicted with the Master Curve approach is not an adequate fit to the experimental data, whereas the agreement of the test results and the K IC (T) curve calculated with the probabilistic model is good. An analysis is performed for a possible variation of the K IC (T) curve shape and the scatter in K IC results. (author)

  7. Technology development on analysis program for measuring fracture toughness of irradiated specimens

    International Nuclear Information System (INIS)

    Shibata, Akira; Takada, Fumiki

    2007-03-01

    The fracture toughness which represents resistance for brittle or ductile fracture is one of the most important material property concerning linear and non-linear fracture mechanics analyses. In order to respond to needs of collecting data relating to fracture toughness of pressure vessel and austenitic stainless steels, fracture toughness test for irradiated materials has been performed in JMTR hot laboratory. On the other hand, there has been no computer program for analysis of fracture toughness using the test data obtained from the test apparatus installed in the hot cell. Therefore, only load-displacement data have been provided to users to calculate fracture toughness of irradiated materials. Recently, request of analysis of fracture toughness have been increased. Thus a computer program, which calculates the amount of the crack extension, the compliance and the fracture toughness from the data acquired from the test apparatus installed in the hot cell, has been developed. In the program unloading elastic compliance method is applied based on ASTM E1820-01. Through the above development, the request for the fracture toughness analysis can be satisfied and the fracture toughness of irradiated test specimens can be provided to users. (author)

  8. Status report on the use of the CRB for the measurement of fracture toughness of RPV steels

    International Nuclear Information System (INIS)

    Scibetta, M.; Chaouadi, R.; Van Walle, E.

    1998-02-01

    A large number of fracture toughness tests were performed in order to assess the use of the circumferentially-Cracked Round Bar (CRB) as a potential method for the measurement of fracture toughness of Reactor Pressure Vessel steels. Test conditions were selected to: (1) characterise fracture toughness in the transition region; (2) study the size effect and loss of constraint; (3) establish the limit of validity of this geometry; (4) investigate the ductile fracture at the upper shelf. In the transition region, the fracture toughness obtained from the CRB over-estimates the actual value as long as the loss of constraint and size effect were not taken into account. In addition, the B1/4 size correction is verified and gives a very good description of the size effect. The application of these corrections allows a good prediction of the normalised fracture toughness up to high levels of fracture toughness.In the upper shelf region, promising results were obtained with this geometry to characterise the ductile crack initiation and propagation

  9. A statistical approach to the prediction of pressure tube fracture toughness

    International Nuclear Information System (INIS)

    Pandey, M.D.; Radford, D.D.

    2008-01-01

    The fracture toughness of the zirconium alloy (Zr-2.5Nb) is an important parameter in determining the flaw tolerance for operation of pressure tubes in a nuclear reactor. Fracture toughness data have been generated by performing rising pressure burst tests on sections of pressure tubes removed from operating reactors. The test data were used to generate a lower-bound fracture toughness curve, which is used in defining the operational limits of pressure tubes. The paper presents a comprehensive statistical analysis of burst test data and develops a multivariate statistical model to relate toughness with material chemistry, mechanical properties, and operational history. The proposed model can be useful in predicting fracture toughness of specific in-service pressure tubes, thereby minimizing conservatism associated with a generic lower-bound approach

  10. 46 CFR 154.605 - Toughness test.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Toughness test. 154.605 Section 154.605 Shipping COAST....605 Toughness test. (a) Each toughness test under §§ 154.610 through 154.625 must meet Subpart 54.05 of this chapter. (b) If subsize test specimens are used for the Charpy V-notch toughness test, the...

  11. A comparative assessment of the fracture toughness behavior of ferritic-martensitic steels and nanostructured ferritic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Byun, Thak Sang, E-mail: thaksang.byun@pnnl.gov [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Hoelzer, David T. [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Kim, Jeoung Han [Hanbat National University, Daejeon 305-719 (Korea, Republic of); Maloy, Stuart A. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2017-02-15

    The Fe-Cr alloys with ultrafine microstructures are primary candidate materials for advanced nuclear reactor components because of their excellent high temperature strength and high resistance to radiation-induced damage such as embrittlement and swelling. Mainly two types of Fe-Cr alloys have been developed for the high temperature reactor applications: the quenched and tempered ferritic-martensitic (FM) steels hardened primarily by ultrafine laths and carbonitrides and the powder metallurgy-based nanostructured ferritic alloys (NFAs) by nanograin structure and nanoclusters. This study aims at elucidating the differences and similarities in the temperature and strength dependences of fracture toughness in the Fe-Cr alloys to provide a comparative assessment of their high-temperature structural performance. The K{sub JQ} versus yield stress plots confirmed that the fracture toughness was inversely proportional to yield strength. It was found, however, that the toughness data for some NFAs were outside the band of the integrated dataset at given strength level, which indicates either a significant improvement or deterioration in mechanical properties due to fundamental changes in deformation and fracture mechanisms. When compared to the behavior of NFAs, the FM steels have shown much less strength dependence and formed narrow fracture toughness data bands at a significantly lower strength region. It appeared that at high temperatures ≥600 °C the NFAs cannot retain the nanostructure advantage of high strength and high toughness either by high-temperature embrittlement or by excessive loss of strength. Irradiation studies have revealed, however, that the NFAs have much stronger radiation resistance than tempered martensitic steels, such as lower radiation-induced swelling, finer helium bubble formation, lower irradiation creep rate and reduced low temperature embrittlement.

  12. Fabrication of tough epoxy with shape memory effects by UV-assisted direct-ink write printing.

    Science.gov (United States)

    Chen, Kaijuan; Kuang, Xiao; Li, Vincent; Kang, Guozheng; Qi, H Jerry

    2018-03-07

    3D printing of epoxy-based shape memory polymers with high mechanical strength, excellent thermal stability and chemical resistance is highly desirable for practical applications. However, thermally cured epoxy in general is difficult to print directly. There have been limited numbers of successes in printing epoxy but they suffer from relatively poor mechanical properties. Here, we present an ultraviolet (UV)-assisted 3D printing of thermally cured epoxy composites with high tensile toughness via a two-stage curing approach. The ink containing UV curable resin and epoxy oligomer is used for UV-assisted direct-ink write (DIW)-based 3D printing followed by thermal curing of the part containing the epoxy oligomer. The UV curable resin forms a network by photo polymerization after the 1st stage of UV curing, which can maintain the printed architecture at an elevated temperature. The 2nd stage thermal curing of the epoxy oligomer yields an interpenetrating polymer network (IPN) composite with highly enhanced mechanical properties. It is found that the printed IPN epoxy composites enabled by the two-stage curing show isotropic mechanical properties and high tensile toughness. We demonstrated that the 3D-printed high-toughness epoxy composites show good shape memory properties. This UV-assisted DIW 3D printing via a two-stage curing method can broaden the application of 3D printing to fabricate thermoset materials with enhanced tensile toughness and tunable properties for high-performance and functional applications.

  13. The elevated temperature and thermal shock fracture toughnesses of nuclear pressure vessel steel

    International Nuclear Information System (INIS)

    Hirano, Kazumi; Kobayashi, Hideo; Nakazawa, Hajime; Nara, Atsushi.

    1979-01-01

    Thermal shock experiments were conducted on nuclear pressure vessel steel A533 Grade B Class 1. Elastic-plastic fracture toughness tests were carried out within the same high temperature range of the thermal shock experiment and the relation between stretched zone width, SZW and J-integral was clarified. An elastic-plastic thermal shock fracture toughness value. J sub(tsc) was evaluated from a critical value of stretched zone width, SZW sub(tsc) at the initiation of thermal shock fracture by using the relation between SZW and J. The J sub(tsc) value was compared with elastic-plastic fracture toughness values, J sub( ic), and the difference between the J sub(tsc) and J sub( ic) values was discussed. The results obtained are summarized as follows; (1) The relation between SZW and J before the initiation of stable crack growth in fracture toughness test at a high temperature can be expressed by the following equation regardless of test temperature, SZW = 95(J/E), where E is Young's modulus. (2) Elevated temperature fracture toughness values ranging from room temperature to 400 0 C are nearly constant regardless of test temperature. It is confirmed that upper shelf fracture toughness exists. (3) Thermal shock fracture toughness is smaller than elevated temperature fracture toughness within the same high temperature range of thermal shock experiment. (author)

  14. Development of high toughness, high strength aluminide-bonded carbide ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Becher, P.F.; Plucknett, K.P.; Tiegs, T.N. [Oak Ridge National Lab., TN (United States)] [and others

    1997-04-01

    Cemented carbides are widely used in applications where resistance to abrasion and wear are important, particularly in combination with high strength and stiffness. In the present case, ductile aluminides have been used as a binder phase to fabricate dense carbide cermets by either sintering of mixed powders or a melt-infiltration sintering process. The choice of an aluminide binder was based on the exceptional high temperature strength and chemical stability exhibited by these alloys. For example, TiC-based composites with a Ni{sub 3}Al binder phase exhibit improved oxidation resistance, Young`s moduli > 375 GPa, high fracture strengths (> 1 GPa) that are retained to {ge} 900{degrees}C, and fracture toughness values of 10 to 15 MPa{radical}m, identical to that measured in commercial cobalt-bonded WC with the same test method. The thermal diffusivity values at 200{degrees}C for these composites are {approximately} 0.070 to 0.075 cm{sup 2}/s while the thermal expansion coefficients rise with Ni3Al content from {approximately} 8 to {approximately}11 x 10{sup {minus}6}/{degrees}C over the range of 8 to 40 vol. % Ni{sub 3}Al. The oxidation and acidic corrosion resistances are quite promising as well. Finally, these materials also exhibit good electrical conductivity allowing them to be sectioned and shaped by electrical discharge machining (EDM) processes.

  15. Influence of grain boundaries on the fracture toughness of tungsten alloys

    International Nuclear Information System (INIS)

    Gludovatz, B.; Faleschini, M.; Pippan, R.; Hoffmann, A.

    2007-01-01

    Full text of publication follows: Tungsten and tungsten alloys are possible candidates for future fusion reactors because of their high melting points, high thermal conductivity and their high erosion resistance. Since these materials have a body-centered cubic (bcc) structure, they show a typical change in fracture behaviour from brittle at low temperatures to ductile at high temperatures. For that reason the fracture behaviour of pure tungsten (W), potassium doped tungsten (AKS) and tungsten with 1 wt% La 2 O 3 (WL10) was studied, taking into account the influence of temperature and fabrication condition. Especially AKS has been studied to investigate the longitudinal splitting of the AKS-wires, the crack propagation direction with the lowest fracture toughness. This alloy subjected to intense deformation leads to a material with an elongated grain structure after recrystallization because of the potassium bubbles. Fracture toughness has been investigated by means of 3-point bending (3PB) specimens, double cantilever beam (DCB) specimens and compact tension (CT) specimens. Tests were performed in the range -196 deg. C to more than 1000 deg. C. Though all these materials show an expected increase in fracture toughness with increasing temperature, influences like texture, chemical composition, grain boundary segregation and dislocation density seem to have an extreme influence on the obtained results. These influences can especially be seen in the fracture behaviour and morphology, where two kinds of fracture can occur: on one hand the trans-crystalline and on the other hand the intercrystalline fracture. Therefore techniques like electron backscatter diffraction, auger electron spectroscopy and X-ray line profile analysis were used to determine the parameter influencing fracture toughness. Also new testing techniques have been devised and successfully applied. Additional tests like an 'in-situ EBSD' technique for investigating the formation of dislocations during

  16. Tailoring the toughness and CTE of high temperature bisphenol E cyanate ester (BECy resin

    Directory of Open Access Journals (Sweden)

    M. Thunga

    2014-05-01

    Full Text Available The objective of the present work is to enhancing the toughness and minimizing the CTE of a special class of bisphenol E cyanate ester (BECy resin by blending it with a thermoplastic toughening agent. Poly(ether sulfone was chosen as a high temperature resistant thermoplastic resin to enhance the thermo-mechanical properties of BECy. The influence of poly(ether sulfone/BECy blend composition on the morphology and phase behavior was studied using scanning electron microscopy and dynamic mechanical analysis. The mechanical properties of the blends were evaluated by flexural tests, which demonstrated significant enhancement in the material’s toughness with an increase in PES concentration from 0 to 15 wt%. The coefficient of thermal expansion of pure BECy was reduced from 61 to 48 ppm/°C in the blends with PES, emphasizing the multi-functional benefits of PES as a toughening agent in BECy.

  17. Mental toughness in soccer

    DEFF Research Database (Denmark)

    Diment, Gregory Michael

    2014-01-01

    a systematic observation checklist of mental toughness behavior in professional soccer. Consistent with existing studies, the results created a systematic observation instrument containing 15 mental toughness behaviors. Practical implications include goal-setting, game analysis and self-modeling interventions...

  18. Correlation Between Microstructure and Low-Temperature Impact Toughness of Simulated Reheated Zones in the Multi-pass Weld Metal of High-Strength Steel

    Science.gov (United States)

    Kang, Yongjoon; Park, Gitae; Jeong, Seonghoon; Lee, Changhee

    2018-01-01

    A large fraction of reheated weld metal is formed during multi-pass welding, which significantly affects the mechanical properties (especially toughness) of welded structures. In this study, the low-temperature toughness of the simulated reheated zone in multi-pass weld metal was evaluated and compared to that of the as-deposited zone using microstructural analyses. Two kinds of high-strength steel welds with different hardenabilities were produced by single-pass, bead-in-groove welding, and both welds were thermally cycled to peak temperatures above Ac3 using a Gleeble simulator. When the weld metals were reheated, their toughness deteriorated in response to the increase in the fraction of detrimental microstructural components, i.e., grain boundary ferrite and coalesced bainite in the weld metals with low and high hardenabilities, respectively. In addition, toughness deterioration occurred in conjunction with an increase in the effective grain size, which was attributed to the decrease in nucleation probability of acicular ferrite; the main cause for this decrease changed depending on the hardenability of the weld metal.

  19. Fracture toughness and stress relief response of irradiated Type 347/348 stainless steel

    International Nuclear Information System (INIS)

    Haggag, F.M.

    1985-01-01

    A test program has experimentally determined: (1) The fracture toughness of Type 347/348 stainless steel (SS) specimens with high values of irradiation fluence (2.3 to 4.8 x 10 22 n/cm 2 , E > 1.0 MeV) and experiencing different levels of irradiation creep (0.0, 0.6, 1.1, 1.8%), (2) the effect of thermal stress relief on fracture toughness recovery for the highly irradiated material, and (3) the mechanisms associated with fracture toughness recovery due to thermal stress relief. The postirradiation fracture toughness tests and tensile tests were conducted at 427 0 C

  20. The microstructure effect on the fracture toughness of ferritic Ni-alloyed steels

    International Nuclear Information System (INIS)

    Scheid, Adriano; Félix, Lorenzo Marzari; Martinazzi, Douglas; Renck, Tiago; Fortis Kwietniewski, Carlos Eduardo

    2016-01-01

    Production of oil and gas in the Brazilian pre-salt faces several technical challenges and one of them that is a major concern is the presence of CO_2 in high concentration. The aim of this work is to evaluate the fracture toughness of two nickel-containing steels as an alternative material to manufacture low-temperature toughness improved CO_2 transporting pipelines for Enhanced oil recovery (EOR). Optical and scanning electron microscopies were employed to characterize the steels microstructures. Electron back-scattered diffraction was used to estimate the effective grain size and the density of high-angle grain boundaries. Fracture toughness was determined by the use of the crack tip opening displacement methodology. The results indicated that for the as-rolled condition the large islands of the microconstituent M/A in the 5"1"/"2 Ni steel had a detrimental effect on fracture toughness at −100 °C, while finer M/A particles and lower effective grain size with higher density of high-angle grain boundaries in the 9 Ni steel turned its fracture toughness practically temperature independent. Additionally, heat treatment (quenching and tempering) has the potential to dissolve the M/A hard particles and consequently improve fracture toughness at low temperature.

  1. The microstructure effect on the fracture toughness of ferritic Ni-alloyed steels

    Energy Technology Data Exchange (ETDEWEB)

    Scheid, Adriano, E-mail: scheid@ufpr.br [Programa de Pos-Graduação em Engenharia Mecânica, PGMec, Universidade Federal do Paraná, Av. Cel. Francisco H. dos Santos, 210, Curitiba (Brazil); Félix, Lorenzo Marzari; Martinazzi, Douglas; Renck, Tiago; Fortis Kwietniewski, Carlos Eduardo [Programa de Pos-Graduação em Engenharia de Minas, Metalurgia e Materiais, PPGE3M, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500, Porto Alegre (Brazil)

    2016-04-20

    Production of oil and gas in the Brazilian pre-salt faces several technical challenges and one of them that is a major concern is the presence of CO{sub 2} in high concentration. The aim of this work is to evaluate the fracture toughness of two nickel-containing steels as an alternative material to manufacture low-temperature toughness improved CO{sub 2} transporting pipelines for Enhanced oil recovery (EOR). Optical and scanning electron microscopies were employed to characterize the steels microstructures. Electron back-scattered diffraction was used to estimate the effective grain size and the density of high-angle grain boundaries. Fracture toughness was determined by the use of the crack tip opening displacement methodology. The results indicated that for the as-rolled condition the large islands of the microconstituent M/A in the 5{sup 1/2} Ni steel had a detrimental effect on fracture toughness at −100 °C, while finer M/A particles and lower effective grain size with higher density of high-angle grain boundaries in the 9 Ni steel turned its fracture toughness practically temperature independent. Additionally, heat treatment (quenching and tempering) has the potential to dissolve the M/A hard particles and consequently improve fracture toughness at low temperature.

  2. Interlaminar Fracture Toughness of CFRP Laminates Incorporating Multi-Walled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Elisa Borowski

    2015-06-01

    Full Text Available Carbon fiber reinforced polymer (CFRP laminates exhibit limited fracture toughness due to characteristic interlaminar fiber-matrix cracking and delamination. In this article, we demonstrate that the fracture toughness of CFRP laminates can be improved by the addition of multi-walled carbon nanotubes (MWCNTs. Experimental investigations and numerical modeling were performed to determine the effects of using MWCNTs in CFRP laminates. The CFRP specimens were produced using an epoxy nanocomposite matrix reinforced with carboxyl functionalized multi-walled carbon nanotubes (COOH–MWCNTs. Four MWCNTs contents of 0.0%, 0.5%, 1.0%, and 1.5% per weight of the epoxy resin/hardener mixture were examined. Double cantilever beam (DCB tests were performed to determine the mode I interlaminar fracture toughness of the unidirectional CFRP composites. This composite material property was quantified using the critical energy release rate, GIC. The experimental results show a 25%, 20%, and 17% increase in the maximum interlaminar fracture toughness of the CFRP composites with the addition of 0.5, 1.0, and 1.5 wt% MWCNTs, respectively. Microstructural investigations using Fourier transform infrared (FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS verify that chemical reactions took place between the COOH–MWCNTs and the epoxy resin, supporting the improvements experimentally observed in the interlaminar fracture toughness of the CFRP specimens containing MWCNTs. Finite element (FE simulations show good agreement with the experimental results and confirm the significant effect of MWCNTs on the interlaminar fracture toughness of CFRP.

  3. Mental Toughness Attributes of Junior Level Medalist Badminton Players

    Directory of Open Access Journals (Sweden)

    Varghese C. Antony

    2016-10-01

    Full Text Available The study aims to compare the mental toughness attributes between medalist and non-medalist badminton players and between male and female players. Participants were 15 male and 15 female badminton players aged between 13-19 years (M= 15.71, SD=2.82. Mental toughness questionnaire of Tiwari and Sharma was administered and the data were analyzed by using descriptive statistics and t-test. Medalist players have exhibited higher mean values on self-confidence, attention control, motivation and goal setting attributes. Overall mental toughness of medalists was higher 180.80±17.15 than non-medalists 170.25±20.10. Comparison analysis showed significant difference between medalists and non-medalists on mental toughness attributes: Self-confidence (SCO: p=0.001<0.05, medalists scored (M±SD=31.33±2.10 higher than non-medalists; motivation (MOT: p=0.006<0.05, medalist scored higher (M±SD=33.50±4.07; goal setting (GSE: p=0.044<0.05, medalists scored significantly higher (M±SD=33.55±4.11 than non-medalists. Other attributes did not show any significant difference between medalist and non-medalist players. When compared with gender, no significant difference was observed on mental toughness attributes except attention control (ATNCON: p=0.044<0.05, female players scored (M±SD=38.97±3.08 higher than male players. The findings confirm that mental toughness is a desired attribute which differentiates a medalist and non-medalist player. Connaughton et al., (2007 stated that elite competitive athletes possess better mental toughness. Medalist players displayed better self-confidence than the non-medalists as supported by Kuan and Roy (2007, Loehr (1986. Motivation helps players to achieve their best and enhance mental toughness (Connaughton et al., 2008; Mohammad et al., 2009. Goal setting determines successful performance Weinberg and Weigand (1993, Weinberg (2003. It was concluded that medalist badminton players showed better mental toughness

  4. Investigation of impact toughness of a Ni-based superalloy at elevated temperature

    International Nuclear Information System (INIS)

    Yang, Y.H.; Yu, J.J.; Sun, X.F.; Jin, T.; Guan, H.R.; Hu, Z.Q.

    2012-01-01

    Highlights: ► The samples show highest impact toughness at 600 °C. ► The impact toughness of samples impact at 760 °C drops sharply. ► The voids nucleation and growth are fracture mechanism at elevated temperature. ► The decrease in strength of grain boundaries causes reduction in impact toughness. -- Abstract: The impact toughness of M951 alloy is investigated in temperature range between 20 °C and 800 °C. The results show that the impact toughness of samples impacted at 600 °C shows highest impact toughness value, the impact toughness value drops sharply when the samples impacted at 760 °C. In addition samples impacted at 800 °C show the higher impact toughness than that of samples impact at 760 °C. The scanning electron microscope observations show that cracks initiate at carbides particles due to high stress concentration, which leads to low impact toughness value at 20 °C. The dimples which can absorb more energy are formed during the impact at 600 °C. The samples impacted at 760 °C show lowest impact toughness. Additionally, the dimples nucleation, growth and coalescence are the major fracture mechanism at elevated temperature.

  5. Fracture toughness evaluation of elastic-plastic J-integral for high temperature components of gas turbine in power plants

    International Nuclear Information System (INIS)

    Chung, Nam Yong; Kim, Moon Young; Kim, Jong Woo

    1999-01-01

    In the study, the analysis of elastic-plastic J-integral was performed in high temperature components for gas turbine based on elastic-plastic fracture mechanics. It had been operated on the range of about 700 deg C and degraded by high temperature. It was tested for material properties of used component because of material properties changing at high temperature condition. The elastic-plastic fracture mechanics parameter, J is obtained with finite element method. A method is suggested which determines J Ic applying analysis of elastic-plastic finite element method and results of experimental load-displacements with CT specimen. It is also investigated that J-integral is applied for the elastic-plastic analysis in high temperature components. The elastic-plastic fracture toughness. J Ic determined by finite element was obtained with high accuracy using the experimental method.=20

  6. Fracture toughness of irradiated beryllium

    International Nuclear Information System (INIS)

    Beeston, J.M.

    1978-01-01

    The fracture toughness of nuclear grade hot-pressed beryllium upon irradiation to fluences of 3.5 to 5.0 x 10 21 n/cm 2 , E greater than 1 MeV, was determined. Procedures and data relating to a round-robin test contributing to a standard ASTM method for unirradiated beryllium are discussed in connection with the testing of irradiated specimens. A porous grade of beryllium was also irradiated and tested, thereby enabling some discrimination between the models for describing the fracture toughness behavior of porous beryllium. The fracture toughness of unirradiated 2 percent BeO nuclear grade beryllium was 12.0 MPa m/sup 1 / 2 /, which was reduced 60 percent upon irradiation at 339 K and testing at 295 K. The fracture toughness of a porous grade of beryllium was 13.1 MPa m/sup 1 / 2 /, which was reduced 68 percent upon irradiation and testing at the same conditions. Reasons for the reduction in fracture toughness upon irradiation are discussed

  7. Effect of welding heat input on microstructures and toughness in simulated CGHAZ of V–N high strength steel

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Jun, E-mail: hujunral@163.com [The State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819 (China); Du, Lin-Xiu [The State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819 (China); Wang, Jian-Jun [Institute of Materials Research, School of Material and Metallurgy, Northeastern university, Shenyang 110819 (China); Gao, Cai-Ru [The State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819 (China)

    2013-08-10

    For the purpose of obtaining the appropriate heat input in the simulated weld CGHAZ of the hot-rolled V–N microalloyed high strength S-lean steel, the microstructural evolution, hardness, and toughness subjected to four different heat inputs were investigated. The results indicate that the hardness decreases with increase in the heat input, while the toughness first increases and then decreases. Moderate heat input is optimum, and the microstructure is fine polygonal ferrite, granular bainite, and acicular ferrite with dispersive nano-scale V(C,N) precipitates. The hardness is well-matched with that of the base metal. Moreover, the occurrence of energy dissipating micromechanisms (ductile dimples, tear ridges) contributes to the maximum total impact energy. The detrimental effect of the free N atoms on the toughness can be partly remedied by optimizing the microstructural type, fraction, morphologies, and crystallographic characteristics. The potency of V(C,N) precipitates on intragranular ferrite nucleation without MnS assistance under different heat inputs was discussed.

  8. High toughness in the intercritically reheated coarse-grained (ICRCG) heat-affected zone (HAZ) of low carbon microalloyed steel

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Jun, E-mail: hujunral@163.com [The State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819 (China); Du, Lin-Xiu [The State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819 (China); Wang, Jian-Jun [Institute of Materials Research, School of Material and Metallurgy, Northeastern University, Shenyang 110819 (China); Xie, Hui; Gao, Cai-Ru [The State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819 (China); Misra, R.D.K. [Laboratory for Excellence in Advanced Steel Research, Center for Structural and Functional Materials, University of Louisiana at Lafayette, Lafayette, LA 70504-4130 (United States)

    2014-01-10

    Motivated by the small lattice mismatch between ferrite and vanadium nitride (VN), we describe here the welding thermal cycle simulation that provides high toughness in the ICRCG HAZ of low carbon V–N steel. This unique behavior is attributed to the formation of ultra-fine grained ferrite along prior austenite grain boundaries generated by the first pass welding thermal cycle with high misorientation boundaries, where V(C, N) precipitates provide potential nucleation sites for ferrite, leading to extraordinary refinement of martensite/austenite (M/A) constituent. Nitrogen stimulates the precipitation behavior of V(C, N). The nucleation of high density of V(C, N) precipitates consumes carbon-content in the austenite, leading to decrease in the carbon-content in the M/A constituent, with consequent decrease in hardness. The increase in toughness is explained in terms of Griffith's crack propagation theory.

  9. High toughness in the intercritically reheated coarse-grained (ICRCG) heat-affected zone (HAZ) of low carbon microalloyed steel

    International Nuclear Information System (INIS)

    Hu, Jun; Du, Lin-Xiu; Wang, Jian-Jun; Xie, Hui; Gao, Cai-Ru; Misra, R.D.K.

    2014-01-01

    Motivated by the small lattice mismatch between ferrite and vanadium nitride (VN), we describe here the welding thermal cycle simulation that provides high toughness in the ICRCG HAZ of low carbon V–N steel. This unique behavior is attributed to the formation of ultra-fine grained ferrite along prior austenite grain boundaries generated by the first pass welding thermal cycle with high misorientation boundaries, where V(C, N) precipitates provide potential nucleation sites for ferrite, leading to extraordinary refinement of martensite/austenite (M/A) constituent. Nitrogen stimulates the precipitation behavior of V(C, N). The nucleation of high density of V(C, N) precipitates consumes carbon-content in the austenite, leading to decrease in the carbon-content in the M/A constituent, with consequent decrease in hardness. The increase in toughness is explained in terms of Griffith's crack propagation theory

  10. Test methodology and technology of fracture toughness for small size specimens

    Energy Technology Data Exchange (ETDEWEB)

    Wakai, E.; Takada, F.; Ishii, T.; Ando, M. [Japan Atomic Energy Agency, Naga-gun, Ibaraki-ken (Japan); Matsukawa, S. [JNE Techno-Research Co., Kanagawa-ken (Japan)

    2007-07-01

    Full text of publication follows: Small specimen test technology (SSTT) is required to investigate mechanical properties in the limited availability of effective irradiation volumes in test reactors and accelerator-based neutron and charged particle sources. The test methodology guideline and the manufacture processes for very small size specimens have not been established, and we would have to formulate it. The technology to control exactly the load and displacement is also required in the test technology under the environment of high dose radiation produced from the specimens. The objective of this study is to examine the test technology and methodology of fracture toughness for very small size specimens. A new bend test machine installed in hot cell has been manufactured to obtain fracture toughness and DBTT (ductile - brittle transition temperature) of reduced-activation ferritic/martensitic steels for small bend specimens of t/2-1/3PCCVN (pre-cracked 1/3 size Charpy V-notch) with 20 mm length and DFMB (deformation and fracture mini bend specimen) with 9 mm length. The new machine can be performed at temperatures from -196 deg. C to 400 deg. C under unloading compliance method. Neutron irradiation was also performed at about 250 deg. C to about 2 dpa in JMTR. After the irradiation, fracture toughness and DBTT were examined by using the machine. Checking of displacement measurement between linear gauge of cross head's displacement and DVRT of the specimen displacement was performed exactly. Conditions of pre-crack due to fatigue in the specimen preparation were also examined and it depended on the shape and size of the specimens. Fracture toughness and DBTT of F82H steel for t/2-1/3PCCVN, DFMB and 0.18DCT specimens before irradiation were examined as a function of temperature. DBTT of smaller size specimens of DFMB was lower than that of larger size specimen of t/2-1/3PCCVN and 0.18DCT. The changes of fracture toughness and DBTT due to irradiation were also

  11. Mezzo-scopic Analysis of Fracture Toughness in Steels

    Directory of Open Access Journals (Sweden)

    Miyata Takashi

    2002-01-01

    Full Text Available The cleavage fracture toughness of steels was mezzo-scopically analyzed on the basis of the statistical local fracture criterion approach. The statistical stress criterion at the crack tip region suggests that the cleavage fracture toughness in steels can be described as a function of the yield stress, the cleavage fracture stress, and other mechanical properties of the materials. Formulation of the cleavage fracture toughness was first examined through an investigation on correlation between the cleavage toughness and the cleavage fracture stress obtained in notched round bar specimens in accordance with the theoretical prediction. Then, the scatter of the toughness, specimen thickness effect on the toughness, deterioration of the toughness due to cold working and irradiation, and improvement of the toughness caused by the Ni addition, were analyzed through the formulation of the toughness.

  12. The statistical background to proposed ASME/MPC fracture toughness reference curves

    International Nuclear Information System (INIS)

    Oldfield, W.

    1981-01-01

    The ASME Pressure Vessel Codes define, in Sec. 11, lower bound fracture toughness curves. These curves are used to predict the lower bound fracture toughness on the basis of the RT test procedure. This test is used to remove heat to heat differences, by permitting the lower bound (reference) curve to be moved along the temperature scale according to the measured RT. Numerous objections have been raised to the procedure, and a Subcommittee (the ASME/MPC Working Group on Reference Toughness) is currently revising the codified procedures for fracture toughness prediction. The task has required a substantial amount of statistical work, since the new procedure are to have a statistical basis. Using initiation fracture toughness (J-Integral R curve procedures in the ductile domain) it was shown that when CVN energy data is properly transformed it is highly correlated with valid fracture toughness measurements. A single functional relationship can be used to predict the mean fracture toughness for a sample of steel from a set of CVN energy measurements, and the coefficients of the function tabulated. More importantly, the approximate lower statistical bounds to the initiation fracture toughness behaviour can be similarly predicted, and coefficients for selected bounds have also been tabulated. (orig.)

  13. Use of alternative waste materials in producing ultra-high performance concrete

    Directory of Open Access Journals (Sweden)

    Ahmad Shamsad

    2017-01-01

    Full Text Available In a corrosive environment similar to that of the Arabian Gulf, use of high-performance concrete is one of the options to ensure a target service life of concrete structures. However, in absence of good quality coarse aggregates, it is a challenging task to produce high-performance concrete. Recently, the possibility of producing ultra-high-performance concrete (UHPC has been widely reported in the literature. UHPC is produced without coarse aggregates at very low water to cementitious materials ratio, high amounts of cement, mineral admixtures, and superplasticizer along with fine quartz sand as aggregate, quartz powder as micro-filler, a nd steel fibres for fracture toughness. In the present work, an effort was made to utilize local waste materials as alternative mineral admixtures and local dune sand as aggregate in producing different UHPC mixtures without addition of quartz powder. The mechanical properties, shrinkage, and durability characteristics of the UHPC mixtures were studied. Test results indicate that it is possible to produce UHPC mixtures using alternative waste materials, which would have targeted flow, strength, toughness, and resistance against reinforcement corrosion. The information presented in the paper would help in optimum selection of a mixture of UHPC considering the availability of local materials, exposure conditions and structural requirements.

  14. Fracture toughness of stainless steel welds

    International Nuclear Information System (INIS)

    Mills, W.J.

    1985-11-01

    The effects of temperature, composition and weld-process variations on the fracture toughness behavior for Types 308 and 16-8-2 stainless steel (SS) welds were examined using the multiple-specimen J/sub R/-curve procedure. Fracture characteristics were found to be dependent on temperature and weld process but not on filler material. Gas-tungsten-arc (GTA) welds exhibited the highest fracture toughness, a shielded metal-arc (SMA) weld exhibited an intermediate toughness and submerged-arc (SA) welds yielded the lowest toughness. Minimum-expected fracture properties were defined from lower-bound J/sub c/ and tearing modulus values generated here and in previous studies. Fractographic examination revealed that microvoid coalescence was the operative fracture mechanism for all welds. Second phase particles of manganese silicide were found to be detrimental to the ductile fracture behavior because they separated from the matrix during the initial stages of plastic straining. In SA welds, the high density of inclusions resulting from silicon pickup from the flux promoted premature dimple rupture. The weld produced by the SMA process contained substantially less manganese silicide, while GTA welds contained no silicide inclusions. Delta ferrite particles present in all welds were substantially more resistant to local failure than the silicide phase. In welds containing little or no manganese silicide, delta ferrite particles initiated microvoid coalescence but only after extensive plastic straining

  15. Fracture toughness of zirconia ceramic crowns made by feather-edge tooth preparation design

    Directory of Open Access Journals (Sweden)

    Mirković Nemanja

    2012-01-01

    Full Text Available Background/Aim. Fracture toughness determines functional crown strenght and prevents damages on ceramics during mastication. There is a lack of relevant literature data about fracture toughness of crowns made by feather-edge preparation. Mechanical testing of ceramic samples is supposed to show if feather-edge tooth preparation is a successful method for making ceramic crowns without any risk of reduction of their mechanical properties. This research was done to establish effects of feather-edge tooth preparation on fracture toughness of single zirconia ceramic crowns. Methods. The research was performed as an experimental study. Sixty (60 ceramic crowns were made on non-carious extracted human premolars. Thirty (30 crowns were made on the basis of feather-edge preparation (experimental group I. The group II included 30 crowns made on 1 mm rounded shoulder. Crowns fabrication was executed on a copy mill production system “Zirkonzahn” (Zirkonzahn GMBH, Gais, Germany. The spherical compression test was used to determine fracture toughness, using 6 mm diameter ceramic ball. Fracture load for damaging ceramic crown was recorded on a universal testing machine - Zwick, type 1464, with the speed of 0.05 mm/min. Results. The results of this research introduced significant differences between fracture toughness of ceramic samples in every examined group. However, fracture toughness of crowns from both group was above 2 000 N, what was double beyond a recommended value. The mean value of fracture toughness in the feather-edge group was 2 090 N, and in shoulder group it was 2 214 N. Conclusion. This research showed a high fracture toughness of zirconia crowns made on feather-edge preparation. The examined crowns showed a fracture resistance at a sufficient distance in relation to the minimum values of functional loads. Further research of functional loads of these crown is necessary, as well as research of marginal adaptation of cemented crowns and

  16. Advanced Vadose Zone Simulations Using TOUGH

    Energy Technology Data Exchange (ETDEWEB)

    Finsterle, S.; Doughty, C.; Kowalsky, M.B.; Moridis, G.J.; Pan,L.; Xu, T.; Zhang, Y.; Pruess, K.

    2007-02-01

    The vadose zone can be characterized as a complex subsurfacesystem in which intricate physical and biogeochemical processes occur inresponse to a variety of natural forcings and human activities. Thismakes it difficult to describe, understand, and predict the behavior ofthis specific subsurface system. The TOUGH nonisothermal multiphase flowsimulators are well-suited to perform advanced vadose zone studies. Theconceptual models underlying the TOUGH simulators are capable ofrepresenting features specific to the vadose zone, and of addressing avariety of coupled phenomena. Moreover, the simulators are integratedinto software tools that enable advanced data analysis, optimization, andsystem-level modeling. We discuss fundamental and computationalchallenges in simulating vadose zone processes, review recent advances inmodeling such systems, and demonstrate some capabilities of the TOUGHsuite of codes using illustrative examples.

  17. Fracture toughness of irradiated candidate materials for ITER first wall/blanket structures: Preliminary results

    International Nuclear Information System (INIS)

    Alexander, D.J.; Pawel, J.E.; Grossbeck, M.L.; Rowcliffe, A.F.

    1993-01-01

    Candidate materials for first wall/blanket structures in ITER have been irradiated to damage levels of about 3 dpa at temperatures of either 60 or 250 degrees C. Preliminary results have been obtained for several of these materials irradiated at 60 degrees C. The results show that irradiation at this temperature reduces the fracture toughness of austenitic stainless steels, but the toughness remains quite high. The unloading compliance technique developed for the subsize disk compact specimens works quite well, particularly for materials with lower toughness. Specimens of materials with very high toughness deform excessively, and this results in experimental difficulties

  18. New classes of tough composite materials-Lessons from natural rigid biological systems

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, G. [Department of Materials Science and Engineering, Box 352120, University of Washington, Seattle, WA 98195-2120 (United States)]. E-mail: gmayer@u.washington.edu

    2006-09-15

    The structures and properties of a new class of composite materials, containing a predominantly high volume fraction ceramic or glass phase, combined with minor organic (adhesive) phases, have been studied. These composites have unusual combinations of mechanical properties, such as stiffness, strength, and toughness. They are based on the architecture of a rigid natural material, the nacre structure, such as those found in the shells of the abalone Haliotis rufescens, and those of other mollusk shells. The mechanisms underlying these properties have also been studied. Analogs (utilizing high-performance engineering materials), that mimic many of the mechanisms underlying those superior combinations of properties, have been built. The results of the foregoing investigations are discussed. It was found that the toughness of segmented composite beams which have high volume fractions of ceramic (89 v / o) exceeded those of continuous layered beams, as well as the monolithic ceramic (alumina) on which they are based.

  19. New classes of tough composite materials-Lessons from natural rigid biological systems

    International Nuclear Information System (INIS)

    Mayer, G.

    2006-01-01

    The structures and properties of a new class of composite materials, containing a predominantly high volume fraction ceramic or glass phase, combined with minor organic (adhesive) phases, have been studied. These composites have unusual combinations of mechanical properties, such as stiffness, strength, and toughness. They are based on the architecture of a rigid natural material, the nacre structure, such as those found in the shells of the abalone Haliotis rufescens, and those of other mollusk shells. The mechanisms underlying these properties have also been studied. Analogs (utilizing high-performance engineering materials), that mimic many of the mechanisms underlying those superior combinations of properties, have been built. The results of the foregoing investigations are discussed. It was found that the toughness of segmented composite beams which have high volume fractions of ceramic (89 v / o) exceeded those of continuous layered beams, as well as the monolithic ceramic (alumina) on which they are based

  20. Toughness of the Virunga mountain gorilla (Gorilla beringei beringei) diet across an altitudinal gradient.

    Science.gov (United States)

    Glowacka, Halszka; McFarlin, Shannon C; Vogel, Erin R; Stoinski, Tara S; Ndagijimana, Felix; Tuyisingize, Deo; Mudakikwa, Antoine; Schwartz, Gary T

    2017-08-01

    The robust masticatory system of mountain gorillas is thought to have evolved for the comminution of tough vegetation, yet, compared to other primates, the toughness of the mountain gorilla diet is unremarkable. This may be a result of low plant toughness in the mountain gorilla environment or of mountain gorillas feeding selectively on low-toughness foods. The goal of this paper is to determine how the toughness of the mountain gorilla diet varies across their habitat, which spans a large altitudinal range, and whether there is a relationship between toughness and food selection by mountain gorillas. We collected data on the following variables to determine whether, and if so how, they change with altitude: leaf toughness of two plant species consumed by mountain gorillas, at every 100 m increase in altitude (2,600-3,700 m); toughness of consumed foods comprising over 85% of the gorilla diet across five vegetation zones; and toughness of unconsumed/infrequently consumed plant parts of those foods. Although leaf toughness increased with altitude, the toughness of the gorilla diet remained similar. There was a negative relationship between toughness and consumption frequency, and toughness was a better predictor of consumption frequency than plant frequency, biomass, and density. Consumed plant parts were less tough than unconsumed/infrequently consumed parts and toughness of the latter increased with altitude. Although it is unclear whether gorillas select food based on toughness or use toughness as a sensory cue to impart other plant properties (e.g., macronutrients, chemicals), our results that gorillas maintain a consistent low-toughness dietary profile across altitude, despite toughness increasing with altitude, suggest that the robust gorilla masticatory apparatus evolved for repetitive mastication of foods that are not high in toughness. © 2017 Wiley Periodicals, Inc.

  1. Fracture toughness of irradiated candidate materials for ITER first wall/blanket structures

    International Nuclear Information System (INIS)

    Alexander, D.J.; Pawel, J.E.; Grossbeck, M.L.; Rowcliffe, A.F.; Shiba, Kiyoyuki

    1994-01-01

    Disk compact specimens of candidate materials for first wall/blanket structures in ITER have been irradiated to damage levels of about 3 dpa at nominal irradiation temperatures of either 90 or 250 degrees C. These specimens have been tested over a temperature range from 20 to 250 degrees C to determine J-integral values and tearing moduli. The results show that irradiation at these temperatures reduces the fracture toughness of austenitic stainless steels, but the toughness remains quite high. The toughness decreases as the test temperature increases. Irradiation at 250 degrees C is more damaging than at 90 degrees C, causing larger decreases in the fracture toughness. Ferritic-martensitic steels are embrittled by the irradiation, and show the lowest toughness at room temperature

  2. Status of the TOUGH-FLAC simulator and recent applications related to coupled fluid flow and crustal deformations

    Energy Technology Data Exchange (ETDEWEB)

    Rutqvist, J.

    2010-06-01

    This paper presents recent advancement in and applications of TOUGH-FLAC, a simulator for multiphase fluid flow and geomechanics. The TOUGH-FLAC simulator links the TOUGH family multiphase fluid and heat transport codes with the commercial FLAC{sup 3D} geomechanical simulator. The most significant new TOUGH-FLAC development in the past few years is a revised architecture, enabling a more rigorous and tight coupling procedure with improved computational efficiency. The applications presented in this paper are related to modeling of crustal deformations caused by deep underground fluid movements and pressure changes as a result of both industrial activities (the In Salah CO{sub 2} Storage Project and the Geysers Geothermal Field) and natural events (the 1960s Matsushiro Earthquake Swarm). Finally, the paper provides some perspectives on the future of TOUGH-FLAC in light of its applicability to practical problems and the need for high-performance computing capabilities for field-scale problems, such as industrial-scale CO{sub 2} storage and enhanced geothermal systems. It is concluded that despite some limitations to fully adapting a commercial code such as FLAC{sup 3D} for some specialized research and computational needs, TOUGH-FLAC is likely to remain a pragmatic simulation approach, with an increasing number of users in both academia and industry.

  3. Processing bulk natural wood into a high-performance structural material

    Science.gov (United States)

    Song, Jianwei; Chen, Chaoji; Zhu, Shuze; Zhu, Mingwei; Dai, Jiaqi; Ray, Upamanyu; Li, Yiju; Kuang, Yudi; Li, Yongfeng; Quispe, Nelson; Yao, Yonggang; Gong, Amy; Leiste, Ulrich H.; Bruck, Hugh A.; Zhu, J. Y.; Vellore, Azhar; Li, Heng; Minus, Marilyn L.; Jia, Zheng; Martini, Ashlie; Li, Teng; Hu, Liangbing

    2018-02-01

    Synthetic structural materials with exceptional mechanical performance suffer from either large weight and adverse environmental impact (for example, steels and alloys) or complex manufacturing processes and thus high cost (for example, polymer-based and biomimetic composites). Natural wood is a low-cost and abundant material and has been used for millennia as a structural material for building and furniture construction. However, the mechanical performance of natural wood (its strength and toughness) is unsatisfactory for many advanced engineering structures and applications. Pre-treatment with steam, heat, ammonia or cold rolling followed by densification has led to the enhanced mechanical performance of natural wood. However, the existing methods result in incomplete densification and lack dimensional stability, particularly in response to humid environments, and wood treated in these ways can expand and weaken. Here we report a simple and effective strategy to transform bulk natural wood directly into a high-performance structural material with a more than tenfold increase in strength, toughness and ballistic resistance and with greater dimensional stability. Our two-step process involves the partial removal of lignin and hemicellulose from the natural wood via a boiling process in an aqueous mixture of NaOH and Na2SO3 followed by hot-pressing, leading to the total collapse of cell walls and the complete densification of the natural wood with highly aligned cellulose nanofibres. This strategy is shown to be universally effective for various species of wood. Our processed wood has a specific strength higher than that of most structural metals and alloys, making it a low-cost, high-performance, lightweight alternative.

  4. Fracture-toughness variations in Alloy 718

    International Nuclear Information System (INIS)

    Mills, W.J.; Blackburn, L.D.

    1983-04-01

    The effect of product-form variations within a single heat on the J Ic fracture toughness behavior of Alloy 718 was examined at 24, 427 and 538 degree C using the multiple-specimen J R -curve method. Three product forms (plate, round bar and upset forging) were tested in both the conventional and modified heat-treatment (CHT and MHT) conditions. In CHT material, the fracture toughness response was different for the three product forms -- plate having the highest toughness, bar the lowest. The MHT was found to improve the overall fracture resistance for each product form. In this condition, plate and forging had very similar toughness values, but J Ic levels for the bar were considerably lower. These results and WHC data previously reported for four other Alloy 718 heats were unalloyed statistically to establish minimum-expected J Ic values based on tolerance limits bracketing 90% of a total population at a 95% confidence level. Metallographic and fractographic examinations of the seven material lots were performed to relate key microstructural features and operative fracture mechanisms to macroscopic properties. Generally, coarse δ precipitates controlled fracture properties in CHT material by initiating secondary dimples that pre-empted growth of the primary dimples nucleated by broken carbide inclusions. The MHT dissolved the coarse δ particles and thereby suppressed secondary microvoid coalescence. This generally enhanced the fracture resistance of Alloy 718, except when alternate secondary fracture mechanism, such as channel fracture and dimple rupture at δ-phase remnants, prematurely interrupted primary microvoid growth. 25 refs., 12 figs., 12 tabs

  5. Tensile and fracture toughness characteristics of Zr-2.5Nb pressure tube

    International Nuclear Information System (INIS)

    Jung, H. C.; Kim, Y. S.; Ahn, S. B.; Kim, S. S.; Im, K. S.

    2004-01-01

    The object of this study is to evaluate the characteristics of tensile and fracture toughness of Zr-2.5Nb pressure tube. The transverse tensile tests were performed at various temperatures and the fracture toughness tests were carried out at room temperature using the CCT (curved compact tension) specimen. These specimens were directly machined from the pressure tube retaining original curvatures. Also, the fracture toughness of two sets of Zr-2.5Nb manufactured at different time was compared. The chemical analysis and the Vicker's hardness tests were performed at two sets of Zr-2.5Nb pressure tube. The Vicker's hardness value of SET-2 containing more oxygen and carbon relatively was higher about 11 than that of SET-1

  6. Fracture Toughness and Reliability in High-Temperature Structural Ceramics and Composites: Prospects and Challenges for the 21st Century

    Science.gov (United States)

    Dutta, Sunil

    1999-01-01

    The importance of high fracture toughness and reliability in Si3N4, and SiC-based structural ceramics and ceramic matrix composites is reviewed. The potential of these ceramics and ceramic matrix composites for high temperature applications in defense and aerospace applications such as gas turbine engines, radomes, and other energy conversion hardware have been well recognized. Numerous investigations were pursued to improve fracture toughness and reliability by incorporating various reinforcements such as particulate-, whisker-, and continuous fiber into Si3N4 and SiC matrices. All toughening mechanisms, e.g. crack deflection, crack branching, crack bridging, etc., essentially redistribute stresses at the crack tip and increase the energy needed to propagate a crack through the composite material, thereby resulting in improved fracture toughness and reliability. Because of flaw insensitivity, continuous fiber reinforced ceramic composite (CFCC) was found to have the highest potential for higher operating temperature and longer service conditions. However, the ceramic fibers should display sufficient high temperature strength and creep resistance at service temperatures above 1000 'C. The greatest challenge to date is the development of high quality ceramic fibers with associate coatings able to maintain their high strength in oxidizing environment at high temperature. In the area of processing, critical issues are, preparation of optimum matrix precursors, precursor infiltration into fiber array, and matrix densification at a temperature, where grain crystallization and fiber degradation do not occur. A broad scope of effort is required for improved processing and properties with a better understanding of all candidate composite systems.

  7. Biaxial loading effects on fracture toughness of reactor pressure vessel steel

    International Nuclear Information System (INIS)

    McAfee, W.J.; Bass, B.R.; Bryson, J.W. Jr.; Pennell, W.E.

    1995-03-01

    The preliminary phases of a program to develop and evaluate fracture methodologies for assessing crack-tip constraint effects on fracture toughness of reactor pressure vessel (RPV) steels have been completed by the Heavy-Section Steel Technology (HSST) Program. Objectives were to investigate effect of biaxial loading on fracture toughness, quantify this effect through existing stress-based, dual-parameter, fracture-toughness correlations, or propose and verify alternate correlations. A cruciform beam specimen with 2-D, shallow, through-thickness flaw and a special loading fixture was designed and fabricated. Tests were performed using biaxial loading ratios of 0:1 (uniaxial), 0.6:1, and 1:1 (equi-biaxial). Critical fracture-toughness values were calculated for each test. Biaxial loading of 0.6:1 resulted in a reduction in the lower bound fracture toughness of ∼12% as compared to that from the uniaxial tests. The biaxial loading of 1:1 yielded two subsets of toughness values; one agreed well with the uniaxial data, while one was reduced by ∼43% when compared to the uniaxial data. Results were evaluated using J-Q theory and Dodds-Anderson (D-A) micromechanical scaling model. The D-A model predicted no biaxial effect, while the J-Q method gave inconclusive results. When applied to the 1:1 biaxial data, these constraint methodologies failed to predict the observed reduction in fracture toughness obtained in one experiment. A strain-based constraint methodology that considers the relationship between applied biaxial load, the plastic zone width in the crack plane, and fracture toughness was formulated and applied successfully to the data. Evaluation of this dual-parameter strain-based model led to the conclusion that it has the capability of representing fracture behavior of RPV steels in the transition region, including the effects of out-of-plane loading on fracture toughness. This report is designated as HSST Report No. 150

  8. A New Method for Evaluating the Indentation Toughness of Hardmetals

    Directory of Open Access Journals (Sweden)

    Prem C. Jindal

    2018-05-01

    Full Text Available This paper proposes a new method of evaluating the indentation toughness of hardmetals using the length of Palmqvist cracks (C and Vickers indentation diagonal size (di. Indentation load “P” is divided into two parts: Pi for plastic indentation size and Pc for Palmqvist cracks. Pi depends upon the square of the indentation size (di2 and Pc depends upon (C3/2. The new method produces a very good linear relationship between the calculated indentation toughness values and the standard conventional linear elastic fracture mechanics toughness values with the same cemented carbide materials for a large number of standard Kennametal grades for both straight WC-Co carbide grades and grades containing cubic carbides. The new method also works on WC-Co hardmetal data selected from recently published literature. The technique compares the indentation toughness values of WC-Co materials before and after vacuum annealing at high temperature. The indentation toughness values of annealed carbide samples were lower than for un-annealed WC-Co hardmetals.

  9. TOUGH, Unsaturated Groundwater Transport and Heat Transport Simulation

    International Nuclear Information System (INIS)

    Pruess, K.A.; Cooper, C.; Osnes, J.D.

    1992-01-01

    thermophysical properties of liquid water and vapor are obtained from steam table equations, as given by the International Formulation Committee, 1967. Air is treated as an ideal gas, and additivity of partial pressures is assumed for air/vapor mixtures. The viscosity of these mixtures is computed by a formulation given by Hirschfelder et al., but using steam table values instead of approximations from kinetic gas theory for vapor viscosity. Air dissolution in water is represented by Henry's law. The basic mass- and energy-balance equations are written in integral form for an arbitrary flow domain. The continuum equations are discretized in space using the 'integral finite difference' method. Time is discretized fully implicitly as a first-order finite difference to obtain the needed numerical stability for an efficient calculation of multi-phase flow. The resulting set of algebraic equations are strongly coupled and highly nonlinear. A completely simultaneous solution of the discretized mass- and energy-balance equations is performed taking all coupling terms into account. The nonlinearities are handled by Newton-Raphson iteration. The discretized equations are valid for one-, two-, or three-dimensional regular and irregular geometries and for porous as well as fractured media. 3 - Restrictions on the complexity of the problem - Maxima of: 500 grid blocks, 27 reservoir domains, 8 relative permeability functions, 7 capillary pressure functions. No allowance is made for vapor pressure lowering or for hysteresis in either capillary pressure or relative permeability. TOUGH does not perform stress calculations for the solid skeleton, but does allow for porosity changes in response to changes in pore pressure (compressibility) and temperature (expansivity)

  10. Bioinspired, Graphene/Al2O3 Doubly Reinforced Aluminum Composites with High Strength and Toughness.

    Science.gov (United States)

    Zhang, Yunya; Li, Xiaodong

    2017-11-08

    Nacre, commonly referred to as nature's armor, has served as a blueprint for engineering stronger and tougher bioinspired materials. Nature organizes a brick-and-mortar-like architecture in nacre, with hard bricks of aragonite sandwiched with soft biopolymer layers. However, cloning nacre's entire reinforcing mechanisms in engineered materials remains a challenge. In this study, we employed hybrid graphene/Al 2 O 3 platelets with surface nanointerlocks as hard bricks for primary load bearer and mechanical interlocking, along with aluminum laminates as soft mortar for load distribution and energy dissipation, to replicate nacre's architecture and reinforcing effects in aluminum composites. Compared with aluminum, the bioinspired, graphene/Al 2 O 3 doubly reinforced aluminum composite demonstrated an exceptional, joint improvement in hardness (210%), strength (223%), stiffness (78%), and toughness (30%), which are even superior over nacre. This design strategy and model material system should guide the synthesis of bioinspired materials to achieve exceptionally high strength and toughness.

  11. Modifications and additions to selected TOUGH2 modules

    International Nuclear Information System (INIS)

    Wu, Y.S.; Mishra, A.K.

    1998-01-01

    The purpose of this report is to provide all software baseline documents necessary for the software qualification of the revised versions of the selected TOUGH2 modules, which include single-phase gas (EOS1G), effective continuum method (EOS3/ECM), saturated/unsaturated flow (EOS9), and radionuclide transport (T2R3D) modules of the TOUGH2 code. TOUGH2 is a numerical simulation code for multi-dimensional, coupled fluid and heat flow of multiphase, multicomponent fluid mixtures in porous and fractured media. This report augments the document Software Qualification of Selected TOUGH2 modules. This report contains the following sections: (1) requirement specifications and code development and (2) software validation test plan and results. These sections comprise sequential parts of Software Lifecycle, and should be used in conjunction with the TOUGH User's Guide, TOUGH2 documentation, TOUGH2 Software Qualification, and Software Qualification of Selected TOUGH2 modules. The version of TOUGH2 used with the software being qualified herein is the October 1996 Standard Version 1.2, as qualified in Wu et al. (1996) and housed at the Department of Energy's Energy Science and Technology Software Center (ESTSC) in Oak Ridge, Tennessee

  12. THE RELATIONSHIP BETWEEN MENTAL TOUGHNESS, STRESS, AND BURNOUT AMONG ADOLESCENTS: A LONGITUDINAL STUDY WITH SWISS VOCATIONAL STUDENTS (.).

    Science.gov (United States)

    Gerber, Markus; Feldmeth, Anne Karina; Lang, Christin; Brand, Serge; Elliot, Catherine; Holsboer-Trachsler, Edith; Pühse, Uwe

    2015-12-01

    Past research has shown that higher stress is associated with increased burnout symptoms. The purpose of this study was to test whether mental toughness protects against symptoms of burnout and whether mental toughness moderates the relationship between perceived stress and burnout over time. Fifty-four vocational students (M age = 18.1 yr., SD = 1.2; 27 males, 27 females) completed self-report questionnaires twice, 10 mo. apart. Perceived stress, mental toughness, and burnout were measured using the Adolescent Stress Questionnaire (ASQ), the Mental Toughness Questionnaire (MTQ), and the Shirom-Melamed Burnout Measure (SMBM). Students who perceived higher stress and lower mental toughness scores reported higher burnout symptoms. Although no significant interaction effects were found between stress and mental toughness in the prediction of burnout, the graphical inspection of the interactions indicated that among students with high stress, those with high mental toughness remained below the cutoff for mild burnout, whereas an increase in burnout symptoms was observable among peers with low mental toughness.

  13. Laboratory Powder Metallurgy Makes Tough Aluminum Sheet

    Science.gov (United States)

    Royster, D. M.; Thomas, J. R.; Singleton, O. R.

    1993-01-01

    Aluminum alloy sheet exhibits high tensile and Kahn tear strengths. Rapid solidification of aluminum alloys in powder form and subsequent consolidation and fabrication processes used to tailor parts made of these alloys to satisfy such specific aerospace design requirements as high strength and toughness.

  14. Application of tan h curve fitting to toughness data

    International Nuclear Information System (INIS)

    Sakai, Yuzuru; Ogura, Nobukazu

    1985-01-01

    Curve-fitting regression procedures for toughness data have been examined. The objectives of fitting curve in the context of the study of nuclear pressure vessel steels are (1) convenient summarization of test data to permit comparison of materials and testing methods; (2) development of statistical base concerning the data; (3) the surveying of the relationships between charpy data and fracture toughness data; (4) estimation of fracture toughness level from charpy absorbed energy data. The computational procedures using the tanh function have been applied to the toughness data (charpy absorbed energy, static fracture toughness, dynamic fracture toughness, crack arrest toughness) of A533B cl.1 and A508 cl.3 steels. The results of the analysis shows the statistical features of the material toughness and gives the method for estimating fracture toughness level from charpy absorbed energy data. (author)

  15. Fracture toughness of fibrous composite materials

    Science.gov (United States)

    Poe, C. C., Jr.

    1984-01-01

    Laminates with various proportions of 0 deg, 45 deg, and 90 deg plies were fabricated from T300/5208 and T300/BP-907 graphite/epoxy prepreg tape material. The fracture toughness of each laminate orientation or lay-up was determined by testing center-cracked specimens, and it was also predicted with the general fracture-toughness parameter. The predictions were good except when crack-tip splitting was large, at which time the toughness and strengths tended to be underpredicted. By using predictions, a parametric study was also made of factors that influence fracture toughness. Fiber and matrix properties as well as lay-up were investigated. Without crack-tip splitting, fracture toughness increases in proportion to fiber strength and fiber volume fraction, increases linearly with E(22)/E(11), is largest when the modulus for non-0 deg fibers is greater than that of 0 deg fibers, and is smallest for 0(m)/90(p)(s) lay-ups. (The E(11) and E(22) are Young's moduli of the lamina parallel to and normal to the direction of the fibers, respectively). For a given proportion of 0 deg plies, the most notch-sensitive lay-ups are 0(m)/90(p)(s) and the least sensitive are 0(m)/45(n)(s) and alpha(s). Notch sensitivity increases with the proportion of 0 deg plies and decreases with alpha. Strong, tough matrix materials, which inhibit crack-tip splitting, generally lead to minimum fracture toughness.

  16. Results of ASTM round robin testing for mode 1 interlaminar fracture toughness of composite materials

    Science.gov (United States)

    Obrien, T. Kevin; Martin, Roderick H.

    1992-01-01

    The results are summarized of several interlaboratory 'round robin' test programs for measuring the mode 1 interlaminar fracture toughness of advanced fiber reinforced composite materials. Double Cantilever Beam (DCB) tests were conducted by participants in ASTM committee D30 on High Modulus Fibers and their Composites and by representatives of the European Group on Fracture (EGF) and the Japanese Industrial Standards Group (JIS). DCB tests were performed on three AS4 carbon fiber reinforced composite materials: AS4/3501-6 with a brittle epoxy matrix; AS4/BP907 with a tough epoxy matrix; and AS4/PEEK with a tough thermoplastic matrix. Difficulties encountered in manufacturing panels, as well as conducting the tests are discussed. Critical issues that developed during the course of the testing are highlighted. Results of the round robin testing used to determine the precision of the ASTM DCB test standard are summarized.

  17. MENTAL TOUGHNESS: A COMPARATIVE STUDY ON KFUPM UNIVERSITY TEAMS

    Directory of Open Access Journals (Sweden)

    MOHAMMED HAMDAN

    2012-06-01

    Full Text Available AbstractMental toughness is an attribute that is often associated with successful performance in competitions. Mental toughness and its importance in competitive Sports have been documented in literature (A.S. Goldberg, 1998; K. Hodge, 1994; J. Tunney, 1987; R.M. Williams, 1988. In sports, many things are left to chance as, sports are predictably unpredictable. Sports persons who enter the competitive arena soon realize that there is more to competition than simply learning the physical skills. It is one thing to possess the physical and mental skills and yet another to be able to use them when needed. Every athletic contest is a contest of control of the delicate mind-body connection, which is dramatically clear within the competitive arena (J.E. Loehr, 1982.Purpose: 1. To compare the mental toughness between King Fahd University of Petroleum and Minerals (KFUPM Judo and Karate teams; 2. To compare the mental toughness between KFUPM Swimming and Track & Field teams. Methods A total of 26 players who are part of KFUPM Judo, Karate , Swimming and Track & Field University teams (2011-12 with age ranging from 18-20 years were selected as subjects for study and were divided into four groups namely; Judo (N= 6, Karate (N= 5, Swimming (N= 8 and Track & Field (N= 7. Mental toughness questionnaire of Tiwari and Sharma (2006 was administered to the subjects. The questionnaire consists of 48 statements and has six sub- scales namely: Self Confidence, Attention Control, Motivation, Goal Setting, Visual Imagery and Attitude Control. T- Test was applied to compare means between the groups. Statistical significance was set at 0.05 levels. Results T- Test failed to reveal significant difference on mental toughness (MT between KFUPM Judo and Karate teams (p = .7 > .05. T-Test also failed to reveal significant difference on MT between KFUPM Swimming and Track & Field teams (p = .122 > .05. T-Test revealed significant difference on Self Confidence between KFUPM

  18. Effect of microstructure on the impact toughness of high strength steels

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez, I.

    2014-07-01

    One of the major challenges in the development of new steel grades is to get increasingly high strength combined with a low ductile brittle transition temperature and a high upper shelf energy. This requires the appropriate microstructural design. Toughness in steels is controlled by different microstructural constituents. Some of them, like inclusions, are intrinsic while others happening at different microstructural scales relate to processing conditions. A series of empirical equations express the transition temperature as a sum of contributions from substitutional solutes, free nitrogen, carbides, pearlite, grain size and eventually precipitation strengthening. Aimed at developing a methodology that could be applied to high strength steels, microstructures with a selected degree of complexity were produced at laboratory in a Nb-microalloyed steel. As a result a model has been developed that consistently predicts the Charpy curves for ferrite-pearlite, bainitic and quenched and tempered microstructures using as input data microstructural parameters. This model becomes a good tool for microstructural design. (Author)

  19. Nanoindentation and micro-mechanical fracture toughness of electrodeposited nanocrystalline Ni–W alloy films

    International Nuclear Information System (INIS)

    Armstrong, D.E.J.; Haseeb, A.S.M.A.; Roberts, S.G.; Wilkinson, A.J.; Bade, K.

    2012-01-01

    Nanocrystalline nickel–tungsten alloys have great potential in the fabrication of components for microelectromechanical systems. Here the fracture toughness of Ni–12.7 at.%W alloy micro-cantilever beams was investigated. Micro-cantilevers were fabricated by UV lithography and electrodeposition and notched by focused ion beam machining. Load was applied using a nanoindenter and fracture toughness was calculated from the fracture load. Fracture toughness of the Ni–12.7 at.%W was in the range of 1.49–5.14 MPa √m. This is higher than the fracture toughness of Si (another important microelectromechanical systems material), but considerably lower than that of electrodeposited nickel and other nickel based alloys. - Highlights: ► Micro-scale cantilevers manufactured by electro-deposition and focused ion beam machining. ► Nanoindenter used to perform micro-scale fracture test on Ni-13at%W micro-cantilevers. ► Calculation of fracture toughness of electrodeposited Ni-13at%W thin films. ► Fracture toughness values lower than that of nanocrystalline nickel.

  20. Nanoindentation and micro-mechanical fracture toughness of electrodeposited nanocrystalline Ni-W alloy films

    Energy Technology Data Exchange (ETDEWEB)

    Armstrong, D.E.J., E-mail: david.armstrong@materials.ox.ac.uk [Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH (United Kingdom); Haseeb, A.S.M.A. [Department of Mechanical Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Roberts, S.G.; Wilkinson, A.J. [Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH (United Kingdom); Bade, K. [Institut fuer Mikrostrukturtechnik (IMT), Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

    2012-04-30

    Nanocrystalline nickel-tungsten alloys have great potential in the fabrication of components for microelectromechanical systems. Here the fracture toughness of Ni-12.7 at.%W alloy micro-cantilever beams was investigated. Micro-cantilevers were fabricated by UV lithography and electrodeposition and notched by focused ion beam machining. Load was applied using a nanoindenter and fracture toughness was calculated from the fracture load. Fracture toughness of the Ni-12.7 at.%W was in the range of 1.49-5.14 MPa {radical}m. This is higher than the fracture toughness of Si (another important microelectromechanical systems material), but considerably lower than that of electrodeposited nickel and other nickel based alloys. - Highlights: Black-Right-Pointing-Pointer Micro-scale cantilevers manufactured by electro-deposition and focused ion beam machining. Black-Right-Pointing-Pointer Nanoindenter used to perform micro-scale fracture test on Ni-13at%W micro-cantilevers. Black-Right-Pointing-Pointer Calculation of fracture toughness of electrodeposited Ni-13at%W thin films. Black-Right-Pointing-Pointer Fracture toughness values lower than that of nanocrystalline nickel.

  1. TOUGH User's Guide

    International Nuclear Information System (INIS)

    Pruess, K.

    1987-08-01

    This document contains a technical description of the TOUGH computer program, which was developed at Lawrence Berkeley Laboratory for simulating the coupled transport of water, vapor, air and heat in porous and fractured media. The physical processes taken into account in TOUGH are discussed, and the governing equations actually solved by the simulator are stated in full detail. A brief overview is given of the mathematical and numerical methods, and the code architecture. The report provides detailed instructions for preparing input decks. Code applications are illustrated by means of six sample problems

  2. Tough-coated hard powders for hardmetals of novel properties

    International Nuclear Information System (INIS)

    Toth, R.E.; Smid, I.; Kladler, G.; Korb, G.; Sherman, A.; Ettmayer, P.

    2001-01-01

    The properties and performance of conventional materials and composites are constrained by solubility limits, diffusion coefficients, and compatibility of physical and chemical constituent properties in their phase equilibria. To escape these limits, ingenious ways of combining strength, toughness, and wear resistance by way of various coatings and laminations have been devised. These coated tools are systematically discarded after only about 10 % of their wear tolerance has been used. Tough-coated hard powders (TCHP), patented by EnDurAloy (USA), are hard refractory particles CVD coated with nanolayers of WC and Co. Consolidation of TCHP creates an engineered homogeneous cellular structure whose interconnected tough WC-Co 'shells' each contain a wear-resistant core (e.g., TiN). In TCHP's, the coating is throughout the tool, not only on the surface, combining the strength, heat resistance, and toughness of cemented carbides with the chemical and abrasion wear resistance of harder materials. As wear progresses, new wear-resistant material continuously replaces the working surfaces and edges of the tool until its geometry reaches its maximum limits. TCHP tools are then reusable many times. Specific coating and consolidation processes, characterization of compacts, and test comparisons with conventional materials are discussed. (author)

  3. A Comparative Study of Fracture Toughness at Cryogenic Temperature of Austenitic Stainless Steel Welds

    Science.gov (United States)

    Aviles Santillana, I.; Boyer, C.; Fernandez Pison, P.; Foussat, A.; Langeslag, S. A. E.; Perez Fontenla, A. T.; Ruiz Navas, E. M.; Sgobba, S.

    2018-03-01

    The ITER magnet system is based on the "cable-in-conduit" conductor (CICC) concept, which consists of stainless steel jackets filled with superconducting strands. The jackets provide high strength, limited fatigue crack growth rate and fracture toughness properties to counteract the high stress imposed by, among others, electromagnetic loads at cryogenic temperature. Austenitic nitrogen-strengthened stainless steels have been chosen as base material for the jackets of the central solenoid and the toroidal field system, for which an extensive set of cryogenic mechanical property data are readily available. However, little is published for their welded joints, and their specific performance when considering different combinations of parent and filler metals. Moreover, the impact of post-weld heat treatments that are required for Nb3Sn formation is not extensively treated. Welds are frequently responsible for cracks initiated and propagated by fatigue during service, causing structural failure. It becomes thus essential to select the most suitable combination of parent and filler material and to assess their performance in terms of strength and crack propagation at operation conditions. An extensive test campaign has been conducted at 7 K comparing tungsten inert gas (TIG) welds using two fillers adapted to cryogenic service, EN 1.4453 and JK2LB, applied to two different base metals, AISI 316L and 316LN. A large set of fracture toughness data are presented, and the detrimental effect on fracture toughness of post-weld heat treatments (unavoidable for some of the components) is demonstrated. In this study, austenitic stainless steel TIG welds with various filler metals have undergone a comprehensive fracture mechanics characterization at 7 K. These results are directly exploitable and contribute to the cryogenic fracture mechanics properties database of the ITER magnet system. Additionally, a correlation between the impact in fracture toughness and microstructure

  4. Fracture toughness determination in steam generator tubes

    International Nuclear Information System (INIS)

    Bergant M; Yawny, A; Perez Ipina, J

    2012-01-01

    The assessment of the structural integrity of steam generator tubes in nuclear power plants deserved increasing attention in the last years due to the negative impact related to their failures. In this context, elastic plastic fracture mechanics (EPFM) methodology appears as a potential tool for the analysis. The application of EPFM requires, necessarily, knowledge of two aspects, i.e., the driving force estimation in terms of an elastic plastic toughness parameter (e.g., J) and the experimental measurement of the fracture toughness of the material (e.g., the material J-resistance curve). The present work describes the development of a non standardized experimental technique aimed to determine J-resistance curves for steam generator tubes with circumferential through wall cracks. The tubes were made of Incoloy 800 (Ni: 30.0-35.0; Cr: 19.0-23.0; Fe: 35.5 min, % in weight). Due to its austenitic microstructure, this alloy shows very high toughness and is widely used in applications where a good corrosion resistance in aqueous environment or an excellent oxidation resistance in high temperature environment is required. Finally, a procedure for the structural integrity analysis of steam generator tubes with crack-like defects, based on a FAD diagram (Failure Assessment Diagram), is briefly described (author)

  5. Long-term toughness of photopolymerizable (meth)acrylate networks in aqueous environments.

    Science.gov (United States)

    Smith, Kathryn E; Trusty, Phillip; Wan, Beatrice; Gall, Ken

    2011-02-01

    Photopolymerizable (meth)acrylate networks are potentially advantageous biomaterials due to their ability to be formed in situ, their fast synthesis rates and their tailorable material properties. The objective of this study was to evaluate how immersion time in phosphate-buffered saline (PBS) affects the toughness of photopolymerizable methyl acrylate (MA)-co-methyl methacrylate-co-poly(ethylene glycol) dimethacrylate networks containing various concentrations of MA. Stress-strain behavior was determined by performing tensile strain to failure testing after soaking in PBS for different periods (1 day up to 9 months). In tandem, differential scanning calorimetry and PBS content measurements were undertaken at each time point in order to determine whether time-dependent changes in toughness were related to changes in T(g) or PBS absorption. The effect of immersion time on network toughness was shown to be dependent upon composition in a manner related to the viscoelastic state of the polymer upon initial immersion in PBS. The results demonstrate that tough acrylate-based materials may not maintain their toughness after several months in PBS. In addition, decreasing the PBS content by changing the network hydrophobicity resulted in better toughness maintenance after 9 months. The results provide a possible means to toughen various amorphous acrylate-based implant materials that are being explored for load-bearing biomedical applications, beyond the systems considered in this work. Published by Elsevier Ltd.

  6. Irradiation effects on fracture toughness of two high-copper submerged-arc welds, HSSI series 5

    International Nuclear Information System (INIS)

    Nanstad, R.K.; Haggag, F.M.; McCabe, D.E.; Iskander, S.K.; Bowman, K.O.; Menke, B.H.

    1992-10-01

    The Fifth Irradiation Series in the Heavy-Section Steel irradiation (HSSI) Program was aimed at obtaining a statistically significant fracture toughness data base on two weldments with high-copper contents to determine the shift and shape of the K lc curve as a consequence of irradiation. The program included irradiated Charpy V-notch impact, tensile, and drop-weight specimens in addition to compact fracture toughness specimens. Compact specimens with thicknesses of 25.4, 50.8, and 101.6 mm [1T C(T), 2T C(T), and 4T C(T), respectively] were irradiated. Additionally, unirradiated 6T C(T) and 8T C(T) specimens with the same K lc measuring capacity as the irradiated specimens were tested. The materials for this irradiation series were two weldments fabricated from special heats of weld wire with copper added to the melt. One lot of Linde 0124 flux was used for all the welds. Copper levels for the two welds are 0.23 and 0.31 wt %, while the nickel contents for both welds are 0.60 wt %. Twelve capsules of specimens were irradiated in the pool-side facility of the Oak Ridge Research Reactor at a nominal temperature of 288 degree C and an average fluence of about 1.5 x 10 19 neutrons/cm 2 (> 1 MeV). This volume, Appendices E and F, contains the load-displacement curves and photographs of the fracture toughness specimens from the 72W weld (0.23 wt % Cu) and the 73 W weld (0.31 wt % Cu), respectively

  7. Fracture toughness evaluations of TP304 stainless steel pipes

    International Nuclear Information System (INIS)

    Rudland, D.L.; Brust, F.W.; Wilkowski, G.M.

    1997-02-01

    In the IPIRG-1 program, the J-R curve calculated for a 16-inch nominal diameter, Schedule 100 TP304 stainless steel (DP2-A8) surface-cracked pipe experiment (Experiment 1.3-3) was considerably lower than the quasi-static, monotonic J-R curve calculated from a C(T) specimen (A8-12a). The results from several related investigations conducted to determine the cause of the observed toughness difference are: (1) chemical analyses on sections of Pipe DP2-A8 from several surface-cracked pipe and material property specimen fracture surfaces indicate that there are two distinct heats of material within Pipe DP2-A8 that differ in chemical composition; (2) SEN(T) specimen experimental results indicate that the toughness of a surface-cracked specimen is highly dependent on the depth of the initial crack, in addition, the J-R curves from the SEN(T) specimens closely match the J-R curve from the surface-cracked pipe experiment; (3) C(T) experimental results suggest that there is a large difference in the quasi-static, monotonic toughness between the two heats of DP2-A8, as well as a toughness degradation in the lower toughness heat of material (DP2-A8II) when loaded with a dynamic, cyclic (R = -0.3) loading history

  8. Effect of copper precipitates on the toughness of low alloy steels for pressure boundary components

    International Nuclear Information System (INIS)

    Foehl, J.; Willer, D.; Katerbau, K.H.

    2004-01-01

    The ferritic bainitic steel 15NiCuMoNb5 (WB 36)is widely used for pressure boundary components. Due to the high copper content which leads to precipitation hardening high strength and toughness are characteristic for this type of steel. However, in the initial state, there is still a high amount of dissolved copper in an oversaturated state which makes the steel susceptible to thermal ageing. Ageing and annealing experiments were performed, and the change in microstructure was investigated by small angle neutron scattering (SANS), measurements of the residual electric resistance and hardness measurements. A correlation between micro structural changes and changes in mechanical properties could be established. It could clearly be shown that significant effects on strength and toughness have to be considered when the size of the copper rich precipitates vary in the range from 1.2 to 2.2 nm in radius. The changes in microstructure affect both, the Carpy impact transition temperature and the fracture toughness qualitatively and quantitatively in a similar way. The investigations have contributed to a better understanding of precipitation hardening by copper not only for this type of steel but also for copper containing steels and weld subjected to neutron irradiation. (orig.)

  9. Fracture toughness in metal matrix composites

    Directory of Open Access Journals (Sweden)

    Perez Ipiña J.E.

    2000-01-01

    Full Text Available Evaluations of the fracture toughness in metal matrix composites (Duralcan reinforced with 15% of Al(20(3 and SiC are presented in this work. The application of Elastic Plastic Fracture Mechanics is discussed and the obtained values are compared with the ones obtained by means of Linear Elastic Fracture Mechanics. Results show that J IC derived K JC values are higher than the corresponding values obtained by direct application of the linear elastic methodology. The effect of a heat treatment on the material fracture toughness was also evaluated in which the analyzed approaches showed, not only different toughness values, but also opposite tendencies. A second comparison of the J IC and K JC values obtained in this work with toughness values reported in the literature is presented and discussed.

  10. The effect of the precipitation of coherent and incoherent precipitates on the ductility and toughness of high-strength steel

    International Nuclear Information System (INIS)

    Hamano, R.

    1993-01-01

    The effect of the coexistence of coherent and incoherent precipitates, such as M 2 C and NiAl, on the ductility and plane strain fracture toughness of 5 wt pct Ni-2 wt pct Al-based high-strength steels was studied. In order to disperse coherent and incoherent precipitates, the heat treatments were carried out as follows: (a) austenitizing at 1373 K, (b) tempering at 1023 or 923 K for dispersing the incoherent precipitates of M 2 C and NiAl, and then (c) aging at 843 K for 2.4 ks to disperse the coherent precipitate of NiAl into the matrix, which contains incoherent precipitates, such as M 2 C and NiAl. The results were obtained as follows: (a) when the strengthening precipitates consist of coherent ones, such as M 2 C and/or NiAl, the ductility and toughness are extremely low, and (b) when the strengthening precipitates consist of coherent and incoherent precipitates, such as M 2 C and NiAl, the ductility and fracture toughness significantly increase with no loss in strength. It is shown that the coexistence of coherent and incoherent precipitates increases homogeneous deformation, thus preventing local strain concentration and early cleavage cracking. Accordingly, the actions of coherent precipitates in strengthening the matrix and of incoherent precipitates in promoting, homogeneous deformation can be expected to increase both the strength and toughness of the material

  11. Tough and Conductive Hybrid Hydrogels Enabling Facile Patterning.

    Science.gov (United States)

    Zhu, Fengbo; Lin, Ji; Wu, Zi Liang; Qu, Shaoxing; Yin, Jun; Qian, Jin; Zheng, Qiang

    2018-04-25

    Conductive polymer hydrogels (CPHs) that combine the unique properties of hydrogels and electronic properties of conductors have shown their great potentials in wearable/implantable electronic devices, where materials with remarkable mechanical properties, high conductivity, and easy processability are demanding. Here, we have developed a new type of polyion complex/polyaniline (PIC/PAni) hybrid hydrogels that are tough, conductive, and can be facilely patterned. The incorporation of conductive phase (PAni) into PIC matrix through phytic acid resulted in hybrid gels with ∼65 wt % water; high conductivity while maintaining the key viscoelasticity of the tough matrix. The gel prepared from 1 M aniline (Ani) exhibited the breaking strain, fracture stress, tensile modulus, and electrical conductivity of 395%, 1.15 MPa, 5.31 MPa, and 0.7 S/m, respectively, superior to the most existing CPHs. The mechanical and electrical performance of PIC/PAni hybrid hydrogels exhibited pronounced rate-dependent and self-recovery behaviors. The hybrid gels can effectively detect subtle human motions as strain sensors. Alternating conductive/nonconductive patterns can be readily achieved by selective Ani polymerization using stencil masks. This facile patterning method based on PIC/PAni gels can be readily scaled up for fast fabrication of wavy gel circuits and multichannel sensor arrays, enabling real-time monitoring of the large-extent and large-area deformations with various sensitivities.

  12. Bioinspired Hierarchical Alumina-Graphene Oxide-Poly(vinyl alcohol) Artificial Nacre with Optimized Strength and Toughness.

    Science.gov (United States)

    Wang, Jinrong; Qiao, Jinliang; Wang, Jianfeng; Zhu, Ying; Jiang, Lei

    2015-05-06

    Due to hierarchical organization of micro- and nanostructures, natural nacre exhibits extraordinary strength and toughness, and thus provides a superior model for the design and fabrication of high-performance artificial composite materials. Although great progress has been made in constructing layered composites by alternately stacking hard inorganic platelets and soft polymers, the real issue is that the excellent strength of these composites was obtained at the sacrifice of toughness. In this work, inspired by the layered aragonite microplatelets/chitin nanofibers-protein structure of natural nacre, alumina microplatelets-graphene oxide nanosheets-poly(vinyl alcohol) (Al2O3/GO-PVA) artificial nacre is successfully constructed through layer-by-layer bottom-up assembly, in which Al2O3 and GO-PVA act as "bricks" and "mortar", respectively. The artificial nacre has hierarchical "brick-and-mortar" structure and exhibits excellent strength (143 ± 13 MPa) and toughness (9.2 ± 2.7 MJ/m(3)), which are superior to those of natural nacre (80-135 MPa, 1.8 MJ/m(3)). It was demonstrated that the multiscale hierarchical structure of ultrathin GO nanosheets and submicrometer-thick Al2O3 platelets can deal with the conflict between strength and toughness, thus leading to the excellent mechanical properties that cannot be obtained using only one size of platelet. We strongly believe that the work presented here provides a creative strategy for designing and developing new composites with excellent strength and toughness.

  13. Towards high-performance materials for road construction

    Science.gov (United States)

    Gladkikh, V.; Korolev, E.; Smirnov, V.

    2017-10-01

    Due to constant increase of traffic, modern road construction is in need of high-performance pavement materials. The operational performance of such materials can be characterized by many properties. Nevertheless, the most important ones are resistance to rutting and resistance to dynamical loads. It was proposed earlier to use sulfur extended asphalt concrete in road construction practice. To reduce the emission of sulfur dioxide and hydrogen sulfide during the concrete mix preparation and pavement production stages, it is beneficial to make such a concrete on the base of complex sulfur modifier. In the present work the influence of the complex modifier to mechanical properties of sulfur extended asphalt concrete was examined. It was shown that sulfur extended asphalt concrete is of high mechanical properties. It was also revealed that there as an anomalous negative correlations between strain capacity, fatigue life and fracture toughness.

  14. Influence of crack depth on the fracture toughness of reactor pressure vessel steel

    International Nuclear Information System (INIS)

    Theiss, T.J.; Bryson, J.W.

    1991-01-01

    The Heavy Section Steel Technology Program (HSST) at Oak Ridge National Laboratory (ORNL) is investigating the influence of flaw depth on the fracture toughness of reactor pressure vessel (RPV) steel. Recently, it has been shown that, in notched beam testing, shallow cracks tend to exhibit an elevated toughness as a result of a loss of constraint at the crack tip. The loss of constraint takes place when interaction occurs between the elastic-plastic crack-tip stress field and the specimen surface nearest the crack tip. An increased shallow-crack fracture toughness is of interest to the nuclear industry because probabilistic fracture-mechanics evaluations show that shallow flaws play a dominant role in the probability of vessel failure during postulated pressurized-thermal-shock (PTS) events. Tests have been performed on beam specimens loaded in 3-point bending using unirradiated reactor pressure vessel material (A533 B). Testing has been conducted using specimens with a constant beam depth (W = 94 mm) and within the lower transition region of the toughness curve for A533 B. Test results indicate a significantly higher fracture toughness associated with the shallow flaw specimens compared to the fracture toughness determined using deep-crack (a/W = 0.5) specimens. Test data also show little influence of thickness on the fracture toughness for the current test temperature (-60 degree C). 21 refs., 5 figs., 3 tabs

  15. Mental Toughness and Individual Differences in Learning, Educational and Work Performance, Psychological Well-being, and Personality: A Systematic Review.

    Science.gov (United States)

    Lin, Ying; Mutz, Julian; Clough, Peter J; Papageorgiou, Kostas A

    2017-01-01

    Mental toughness (MT) is an umbrella term that entails positive psychological resources, which are crucial across a wide range of achievement contexts and in the domain of mental health. We systematically review empirical studies that explored the associations between the concept of MT and individual differences in learning, educational and work performance, psychological well-being, personality, and other psychological attributes. Studies that explored the genetic and environmental contributions to individual differences in MT are also reviewed. The findings suggest that MT is associated with various positive psychological traits, more efficient coping strategies and positive outcomes in education and mental health. Approximately 50% of the variation in MT can be accounted for by genetic factors. Furthermore, the associations between MT and psychological traits can be explained mainly by either common genetic or non-shared environmental factors. Taken together, our findings suggest a 'mental toughness advantage' with possible implications for developing interventions to facilitate achievement in a variety of settings.

  16. Mental Toughness and Individual Differences in Learning, Educational and Work Performance, Psychological Well-being, and Personality: A Systematic Review

    Directory of Open Access Journals (Sweden)

    Ying Lin

    2017-08-01

    Full Text Available Mental toughness (MT is an umbrella term that entails positive psychological resources, which are crucial across a wide range of achievement contexts and in the domain of mental health. We systematically review empirical studies that explored the associations between the concept of MT and individual differences in learning, educational and work performance, psychological well-being, personality, and other psychological attributes. Studies that explored the genetic and environmental contributions to individual differences in MT are also reviewed. The findings suggest that MT is associated with various positive psychological traits, more efficient coping strategies and positive outcomes in education and mental health. Approximately 50% of the variation in MT can be accounted for by genetic factors. Furthermore, the associations between MT and psychological traits can be explained mainly by either common genetic or non-shared environmental factors. Taken together, our findings suggest a ‘mental toughness advantage’ with possible implications for developing interventions to facilitate achievement in a variety of settings.

  17. Mental Toughness and Individual Differences in Learning, Educational and Work Performance, Psychological Well-being, and Personality: A Systematic Review

    Science.gov (United States)

    Lin, Ying; Mutz, Julian; Clough, Peter J.; Papageorgiou, Kostas A.

    2017-01-01

    Mental toughness (MT) is an umbrella term that entails positive psychological resources, which are crucial across a wide range of achievement contexts and in the domain of mental health. We systematically review empirical studies that explored the associations between the concept of MT and individual differences in learning, educational and work performance, psychological well-being, personality, and other psychological attributes. Studies that explored the genetic and environmental contributions to individual differences in MT are also reviewed. The findings suggest that MT is associated with various positive psychological traits, more efficient coping strategies and positive outcomes in education and mental health. Approximately 50% of the variation in MT can be accounted for by genetic factors. Furthermore, the associations between MT and psychological traits can be explained mainly by either common genetic or non-shared environmental factors. Taken together, our findings suggest a ‘mental toughness advantage’ with possible implications for developing interventions to facilitate achievement in a variety of settings. PMID:28848466

  18. Fracture toughness of steel--aluminum deformation welds

    International Nuclear Information System (INIS)

    Albright, C.E.

    1978-11-01

    A study of the fracture toughness (in this case, G/sub Ic/) of steel--aluminum deformation welds using a specially developed double cantilever beam fracture toughness specimen is presented. Welds made at 350 0 C were heat treated at 360, 380, 400, 420, and 440 0 C. An intermetallic reaction product layer of Fe 2 Al 5 is formed at the steel--aluminum interface with increasing heat treating temperature and time by a process of nucleation and growth of discrete particles. A transition in toughness from a higher average G/sub Ic/ value (6097 N/m) to a very low average G/sub Ic/ value (525 N/m) is observed. The decrease in toughness is accompanied by an increase in Fe 2 Al 5 particle diameter from 4 to 8 μm. Failure at the higher toughness values is characterized by ductile rupture through the aluminum. At the lower toughness values, failure occurs between the aluminum and the Fe 2 Al 5 reaction product layer. A void layer forming by a vacancy condensation mechanism in the aluminum adjacent to the Fe 2 Al 5 is shown to cause the embrittlement

  19. Fracture toughness testing on ferritic alloys using the electropotential technique

    International Nuclear Information System (INIS)

    Huang, F.H.; Wire, G.L.

    1981-01-01

    Fracture toughness measurements as done conventionally require large specimens (5 x 5 x 2.5 cm) which would be prohibitively expensive to irradiate over the fluence and temperature ranges required for first wall design. To overcome this difficulty a single specimen technique for J intergral fracture toughness measurements on miniature specimens (1.6 cm OD x 0.25 cm thick) was developed. Comparisons with specimens three times as thick show that the derived J/sub 1c/ is constant, validating the specimen for first wall applications. The electropotential technique was used to obtain continuous crack extension measurements, allowing a ductile fracture resistence curve to be constructed from a single specimen. The irradiation test volume required for fracture toughness measurements using both miniature specimens and single specimen J measurements was reduced a factor of 320, making it possible to perform a systematic exploration of irradiation temperature and dose variables as required for qualification of HT-9 and 9Cr-1Mo base metal and welds for first wall application. Fracture toughness test results for HT-9 and 9Cr-1Mo from 25 to 539 0 C are presented to illustrate the single specimen technique

  20. Effect of Al and N on the toughness of heavy section steel plates

    International Nuclear Information System (INIS)

    Kikutake, Tetsuo; Tokunaga, Yoshikuni; Nakao, Hitoji; Ito, Kametaro; Takaishi, Shogo.

    1988-01-01

    The effect of Al and N on the notch toughness and tensile strength of heavy section pressure vessel steel plates is investigated. Notch toughness of steel A533B (Mn-Mo-Ni), which has mixed microstructure of ferrite and bainite, is drastically changed by the ratio of sol.N/sol.Al. With metallurgical observations, it is revealed that AlN morphology is influenced by the ratio of sol.N/sol.Al through the level of solute Al(C Al ). At the heat treatment of heavy section steel plate, AlN shows OSTWALD ripening and its speed depends upon C Al . When Al is added (Al ≥ 0.010%) in steel and sol.N/sol.Al ≤ 0.5, C Al remains low. This prevents AlN ripening, and brings fine austenite grain size and high toughness. On the other hand, when sol.N/sol.Al Al becomes high and this gives poor toughness through coarse AlN precipitates and coarse austenite grain. Therefore, controll of sol.N/sol.Al over 0.5 is favorable to keep high toughness in A533B steel. In steel A387-22 (Cr-Mo) which has full bainitic microstructure, too fine austenite grain brings about poor hardenability, and polygonal ferrite, which brings about both poor strength and tughness, appears in microstructure. Then sol.N/sol.Al < 0.5 is better to give high hardenability in steel A387-22. (author)

  1. Plastic flow properties and fracture toughness characterization of unirradiated and irradiated tempered martensitic steels

    International Nuclear Information System (INIS)

    Spaetig, P.; Bonade, R.; Odette, G.R.; Rensman, J.W.; Campitelli, E.N.; Mueller, P.

    2007-01-01

    We investigate the plastic flow properties at low and high temperature of the tempered martensitic steel Eurofer97. We show that below room temperature, where the Peierls friction on the screw dislocation is active, it is necessary to modify the usual Taylor's equation between the flow stress and the square root of the dislocation density and to include explicitly the Peierls friction stress in the equation. Then, we compare the fracture properties of the Eurofer97 with those of the F82H steel. A clear difference of the fracture toughness-temperature behavior was found in the low transition region. The results indicate a sharper transition for Eurofer97 than for the F82H. Finally, the shift of the median toughness-temperature curve of the F82H steel was determined after two neutron irradiations performed in the High Flux Reactor in Petten

  2. Hydrogen fracture toughness tester completion

    Energy Technology Data Exchange (ETDEWEB)

    Morgan, Michael J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-09-30

    The Hydrogen Fracture Toughness Tester (HFTT) is a mechanical testing machine designed for conducting fracture mechanics tests on materials in high-pressure hydrogen gas. The tester is needed for evaluating the effects of hydrogen on the cracking properties of tritium reservoir materials. It consists of an Instron Model 8862 Electromechanical Test Frame; an Autoclave Engineering Pressure Vessel, an Electric Potential Drop Crack Length Measurement System, associated computer control and data acquisition systems, and a high-pressure hydrogen gas manifold and handling system.

  3. Rapid Thermal Processing to Enhance Steel Toughness.

    Science.gov (United States)

    Judge, V K; Speer, J G; Clarke, K D; Findley, K O; Clarke, A J

    2018-01-11

    Quenching and Tempering (Q&T) has been utilized for decades to alter steel mechanical properties, particularly strength and toughness. While tempering typically increases toughness, a well-established phenomenon called tempered martensite embrittlement (TME) is known to occur during conventional Q&T. Here we show that short-time, rapid tempering can overcome TME to produce unprecedented property combinations that cannot be attained by conventional Q&T. Toughness is enhanced over 43% at a strength level of 1.7 GPa and strength is improved over 0.5 GPa at an impact toughness of 30 J. We also show that hardness and the tempering parameter (TP), developed by Holloman and Jaffe in 1945 and ubiquitous within the field, is insufficient for characterizing measured strengths, toughnesses, and microstructural conditions after rapid processing. Rapid tempering by energy-saving manufacturing processes like induction heating creates the opportunity for new Q&T steels for energy, defense, and transportation applications.

  4. Ion implantation and fracture toughness of ceramics

    International Nuclear Information System (INIS)

    Clark, J.; Pollock, J.T.A.

    1985-01-01

    Ceramics generally lack toughness which is largely determined by the ceramic surface where stresses likely to cause failure are usually highest. Ion implantation has the capacity to improve the surface fracture toughness of ceramics. Significantly reduced ion size and reactivity restrictions exist compared with traditional methods of surface toughening. We are studying the effect of ion implantation on ceramic fracture toughness using indentation testing as the principal tool of analysis

  5. Multiscale Polymer Composites: A Review of the Interlaminar Fracture Toughness Improvement

    Directory of Open Access Journals (Sweden)

    Vishwesh Dikshit

    2017-10-01

    Full Text Available Composite materials are prone to delamination as they are weaker in the thickness direction. Carbon nanotubes (CNTs are introduced as a multiscale reinforcement into the fiber reinforced polymer composites to suppress the delamination phenomenon. This review paper presents the detailed progress made by the scientific and research community to-date in improving the Mode I and Mode II interlaminar fracture toughness (ILFT by various methodologies including the effect of multiscale reinforcement. Methods of measuring the Mode I and Mode II fracture toughness of the composites along with the solutions to improve them are presented. The use of different methodologies and approaches along with their performance in enhancing the fracture toughness of the composites is summarized. The current state of polymer-fiber-nanotube composites and their future perspective are also deliberated.

  6. Toughness behaviour of tungsten-carbide-cobalt alloys

    International Nuclear Information System (INIS)

    Sigl, L.S.

    1985-05-01

    In the present work the mechanisms of crack propagation in technically important WC-Co alloys are investigated and a model describing the influence of microstructural parameters and of the mechanical properties of the constituents is developed. An energy concept is used for modelling fracture toughness. The energies dissipated in the four crack-paths (trans- and intergranular carbide fracture, fracture across the binder-ligaments, fracture in the binder close to the carbide/binder interface) are summed up using the experimentally determined area-fractions of the crack-paths, the specific energy of brittle fracture in the carbide and of ductile fracture is calculated by integrating the energy to deform a volume element over the plastically deformed region. In contrast to all earlier models, this concept describes fracture toughness of WC-Co alloys only with physically meaningful parameters. The excellent agreement with experimental toughness values and with qualitative observations of crack propagation show that the new model includes all effects which influence toughness. As demonstrated with WC-based hardmetals with a cobalt-nickel binder, the results open new possibilities for optimizing the toughness of composites in which a small amount of a tough phase is embedded in a brittle matrix. (Author, shortened by G.Q.)

  7. Heat treatments and low temperature fracture toughness of a Ti-6A1-4V alloy

    International Nuclear Information System (INIS)

    Nagai, K.; Hiraga, K.; Ishikawa, K.; Ogata, T.

    1984-01-01

    Titanium alloy is one of the reliable structural materials for cryogenic use owing to its high strength, high specific strength and low thermal conductivity. Heat treatment is one method of controlling the normally poor fracture toughness of this alloy at ambient temperature. However, there have been few attempts to improve the low temperature fracture toughness by heat treatment. This study was conducted to elucidate the effects of heat treatments on the low temperature fracture toughness in a Ti-6A1-4V alloy. The effects of the heat treatments were as follows: the beta treatment was a very feasible method to improve the low temperature fracture properties; the alpha+beta treatment was favorable for the increment in the low temperature ductility but did not largely improve the fracture toughness; the double treatment yielded good ductility but was not useful for improving the fracture toughness

  8. Effects of irradiation on initiation and crack-arrest toughness of two high-copper welds and on stainless steel cladding

    International Nuclear Information System (INIS)

    Nanstad, R.K.; Iskander, S.K.; Haggag, F.M.

    1990-01-01

    The objective of the study on the high-copper welds is to determine the effect of neutron irradiation on the shift and shape of the ASME K Ic and K Ia toughness curves. Two submerged-arc welds with copper contents of 0.23 and 0.31 wt % were commercially fabricated in 220-mm-thick plate. Compact specimens fabricated from these welds were irradiated at a nominal temperature of 288 degree C to fluences from 1.5 to 1.9 x 10 19 neutrons/cm 2 (>1 MeV). The fracture toughness test results show that the irradiation-induced shifts at 100 MPa/m were greater than the Charpy 41-J shifts by about 11 and 18 degree C. Mean curve fits indicate mixed results regarding curve shape changes, but curves constructed as lower boundaries to the data do indicate curves of lower slopes. A preliminary evaluation of the crack-arrest results shows that the neutron-irradiation induced crack-arrest toughness temperature shift is about the same as the Charpy V-notch impact temperature shift at the 41-J energy level. The shape of the lower bound curves (for the range of test temperatures covered), compared to those of the ASME K Ia curve did not appear to have been altered by the irradiation. Three-wire stainless steel weld overlay cladding was irradiated at 288 degree C to fluences of 2 and 5 x 10 19 neutrons/cm 2 (>1 MeV). Charpy 41-J temperature shifts of 13 and 28 degree C were observed, respectively. For the lower fluence only, 12.7-mm thick compact specimens showed decreases in both J Ic and the tearing modulus. Comparison of the fracture toughness results with typical plate and a low upper-shelf weld reveals that the irradiated stainless steel cladding possesses low ductile initiation fracture toughness comparable to the low upper-shelf weld. 8 refs., 12 figs., 2 tabs

  9. Development of a statistically-based lower bound fracture toughness curve (Ksub(IR) curve)

    International Nuclear Information System (INIS)

    Wullaert, R.A.; Server, W.L.; Oldfield, W.; Stahlkopf, K.E.

    1977-01-01

    A program of initiation fracture toughness measurements on fifty heats of nuclear pressure vessel production materials (including weldments) was used to develop a methodology for establishing a revised reference toughness curve. The new methodology was statistically developed and provides a predefined confidence limit (or tolerance limit) for fracture toughness based upon many heats of a particular type of material. Overall reference curves were developed for seven specific materials using large specimen static and dynamic fracture toughness results. The heat-to-heat variation was removed by normalizing both the fracture toughness and temperature data with the precracked Charpy tanh curve coefficients for each particular heat. The variance and distribution about the curve were determined, and lower bounds of predetermined statistical significance were drawn based upon a Pearson distribution in the lower shelf region (since the data were skewed to high values) and a t-distribution in the transition temperature region (since the data were normally distributed)

  10. Proceedings of the TOUGH Symposium 2009

    Energy Technology Data Exchange (ETDEWEB)

    Moridis, George J.; Doughty, Christine; Finsterle, Stefan; Sonnenthal, Eric

    2009-10-01

    Welcome to the TOUGH Symposium 2009. Within this volume are the Symposium Program for eighty-nine papers to be presented in both oral and poster formats. The full papers are available as pdfs linked from the Symposium Program posted on the TOUGH Symposium 2009 website http://esd.lbl.gov/newsandevents/events/toughsymposium09/program.html Additional updated information including any changes to the Program will also be available at the website. The papers cover a wide range of application areas and reflect the continuing trend toward increased sophistication of the TOUGH codes. A CD containing the proceedings papers will be published immediately following the Symposium and sent to all participants. As in the prior Symposium, selected papers will be invited for submission to a number of journals for inclusion in Special Issues focused on applications and developments of the TOUGH codes. These journals include, Transport in Porous Media, Geothermics, Energy Conversion and Management, Journal of Nuclear Science and Technology, and the Vadose Zone Journal.

  11. The use of TOUGH2/iTOUGH2 in support of the Yucca Mountain Project: Successes and limitations

    International Nuclear Information System (INIS)

    Bodvarsson, G.S.; Birkholzer, J.T.; Finsterle, S.; Liu, H.H.; Rutqvist, J.; Wu, Y.S.

    2003-01-01

    The TOUGH2/iTOUGH2 family of codes is being used to analyze various processes and phenomena in the unsaturated zone at the proposed high-level nuclear waste repository at Yucca Mountain, Nevada. Various models have been developed that help quantify properties of the volcanic tuffs, water flow, seepage into drifts, and thermally driven coupled processes arising from the heat emitted by radioactive waste. These models are based on various assumptions and approximations that are generally accepted in the literature, but can give rise to different degrees of uncertainty. Some of the key approaches utilized include the continuum approximation, the van Genuchten formulation, the active fracture model, and homogeneous sublayers. These and other approximations are presented separately for the five different models considered, and the resulting levels of uncertainty are discussed

  12. 46 CFR 54.05-16 - Production toughness testing.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Production toughness testing. 54.05-16 Section 54.05-16... Toughness Tests § 54.05-16 Production toughness testing. (a) For vessels of welded construction, production... welding procedures shall be the same as used in the fabrication of the vessel. From each test plate, one...

  13. On the determining role of microstructure of niobium-microalloyed steels with differences in impact toughness

    International Nuclear Information System (INIS)

    Anumolu, R.; Kumar, B. Ravi; Misra, R.D.K.; Mannering, T.; Panda, D.; Jansto, S.G.

    2008-01-01

    The relationship between microstructure and impact toughness was investigated for niobium-microalloyed steels with similar yield strength. The nominal steel composition was similar and any variation in processing history was unintentional. The general microstructure of the investigated steel was similar and consisted of 85% polygonal ferrite and 15% pearlite. Despite these similarities, they exhibited variation in toughness and were classified as high- and low-toughness steels. Detailed microstructural investigation including stereological analysis and electron microscopy implied that toughness is strongly influenced by mean intercept length of polygonal ferrite and pearlite colony, and their distribution, interlamellar spacing, and degenerated pearlite

  14. On the determining role of microstructure of niobium-microalloyed steels with differences in impact toughness

    Energy Technology Data Exchange (ETDEWEB)

    Anumolu, R. [Center for Structural and Functional Materials, University of Louisiana at Lafayette, LA 70504-4130 (United States); Department of Chemical Engineering, University of Louisiana at Lafayette, Lafayette, LA 70504-4130 (United States); Kumar, B. Ravi [Center for Structural and Functional Materials, University of Louisiana at Lafayette, LA 70504-4130 (United States); Misra, R.D.K. [Center for Structural and Functional Materials, University of Louisiana at Lafayette, LA 70504-4130 (United States); Department of Chemical Engineering, University of Louisiana at Lafayette, Lafayette, LA 70504-4130 (United States)], E-mail: dmisra@louisiana.edu; Mannering, T.; Panda, D. [Nucor-Yamato Steel, P.O. Box 1228, 5929 East State Highway 18, Blytheville, AR 72316 (United States); Jansto, S.G. [Reference Metals, 1000 Old Pond Road, Bridgeville, PA 15017 (United States)

    2008-09-15

    The relationship between microstructure and impact toughness was investigated for niobium-microalloyed steels with similar yield strength. The nominal steel composition was similar and any variation in processing history was unintentional. The general microstructure of the investigated steel was similar and consisted of 85% polygonal ferrite and 15% pearlite. Despite these similarities, they exhibited variation in toughness and were classified as high- and low-toughness steels. Detailed microstructural investigation including stereological analysis and electron microscopy implied that toughness is strongly influenced by mean intercept length of polygonal ferrite and pearlite colony, and their distribution, interlamellar spacing, and degenerated pearlite.

  15. C.O.D. toughness testing of medium strength steel as a preliminary development for single specimen J integral toughness tests of SA533-B steel

    International Nuclear Information System (INIS)

    Dean, P.; Tait, R.B.; Garrett, G.G.

    1981-10-01

    The primary purpose of this project is to set up a test facility and to develop the necessary expertise to enable reliable elasto-plastic fracture toughness tests to be performed. Initially, tests are to be conducted on material similar to that used in the Koeberg pressure vessel walls, with the ultimate goal of performing single specimen J integral tests on the pressure vessel steel itself to determine through-thickness toughness variations. The project will comprise a number of stages, each one necessary for the development of the techniques used in J integral testing. These include: (i) development of an appropriate specimen design, of suitable size and shape that is applicable to both crack opening displacement (C.O.D.) and J integral tests; (ii) development, testing and calibration of the necessary associated mechanical and electrical equipment (e.g. clip gauge, amplifiers, interface unit, etc.), with (iii) an estimation of the probable errors and noise levels with a view to their elimantion, leading to (iv) perfection of the sensitivity and reproducibility of, firstly, the multiple specimen C.O.D. technique and, secondly, the multiple specimen J integral techniques. (v) Based on the above techniques, development of the single specimen J integral test method incorporating development of a computerised testing procedure. All the above procedure is to be conducted on similar, but non-Koeberg pressure vessel material ('ROQ Tough'). (vi) Finally, development and testing of both multiple specimen and single specimen J integral tests on actual SA533B material and an investigation of the through thickness toughness and fatigue crack propagation behaviour

  16. Heat-affected-zone toughness in heavy wall pipe: Final report

    Energy Technology Data Exchange (ETDEWEB)

    Dyck, K.; Glover, A.G.; Varo, D.B.

    1988-02-01

    The objective of this program has been to determine the significance of low toughness regions on the service performance of heat-affected zones in heavy wall pipe materials. The low temperature HAZ toughness of welds in microalloyed and quenched and tempered materials at two heat inputs was established, a test technique to produce fatigue cracks in the HAZ was developed, and four full scale fracture tests were completed at /minus/49/degree/F. Publication available from the American Gas Association Order Processing Department, 1515 Wilson Boulevard, Arlington, Virginia 22209-2470 (703/841-8558). 17 refs. (JL)

  17. Mindfulness and mental toughness among provincial adolescent ...

    African Journals Online (AJOL)

    Kathryn van Boom

    psychological basis of mental toughness from within existing, evidence-based ... development of mental toughness among athletes. The existing studies have ... that advocated by cognitive-behavioural interventions and traditional mental skills ...

  18. Understanding Toughness in Bioinspired Cellulose Nanofibril/Polymer Nanocomposites.

    Science.gov (United States)

    Benítez, Alejandro J; Lossada, Francisco; Zhu, Baolei; Rudolph, Tobias; Walther, Andreas

    2016-07-11

    Cellulose nanofibrils (CNFs) are considered next generation, renewable reinforcements for sustainable, high-performance bioinspired nanocomposites uniting high stiffness, strength and toughness. However, the challenges associated with making well-defined CNF/polymer nanopaper hybrid structures with well-controlled polymer properties have so far hampered to deduce a quantitative picture of the mechanical properties space and deformation mechanisms, and limits the ability to tune and control the mechanical properties by rational design criteria. Here, we discuss detailed insights on how the thermo-mechanical properties of tailor-made copolymers govern the tensile properties in bioinspired CNF/polymer settings, hence at high fractions of reinforcements and under nanoconfinement conditions for the polymers. To this end, we synthesize a series of fully water-soluble and nonionic copolymers, whose glass transition temperatures (Tg) are varied from -60 to 130 °C. We demonstrate that well-defined polymer-coated core/shell nanofibrils form at intermediate stages and that well-defined nanopaper structures with tunable nanostructure arise. The systematic correlation between the thermal transitions in the (co)polymers, as well as its fraction, on the mechanical properties and deformation mechanisms of the nanocomposites is underscored by tensile tests, SEM imaging of fracture surfaces and dynamic mechanical analysis. An optimum toughness is obtained for copolymers with a Tg close to the testing temperature, where the soft phase possesses the best combination of high molecular mobility and cohesive strength. New deformation modes are activated for the toughest compositions. Our study establishes quantitative structure/property relationships in CNF/(co)polymer nanopapers and opens the design space for future, rational molecular engineering using reversible supramolecular bonds or covalent cross-linking.

  19. Fracture toughness of Al-Cr alloys with minor additions

    International Nuclear Information System (INIS)

    Datta, S.; Banerjee, M.K.

    2000-01-01

    Fracture toughness behavior of aluminium chromium alloys with minor additions is studied to determine its relation with microstructure and ageing conditions. The effect of the minor additions on the fracture toughness property of the alloys is also studied. Fracture toughness of Al-Cr alloys has been improved by selected minor additions. Also, the fracture toughness of the investigated alloys is found to be sensitive to ageing conditions. (author)

  20. Software qualification of selected TOUGH2 modules

    International Nuclear Information System (INIS)

    Wu, Y.S.; Ahlers, C.F.; Fraser, P.; Simmons, A.; Pruess, K.

    1996-10-01

    The purpose of this package of reports is to provide all software baseline documents necessary for the software qualification of the single-phase Gas (EOS1G), Effective Continuum Method (ECM), Saturated/Unsaturated Flow (EOS9), and Radionuclide Transport (T2R3D) modules of TOUGH2, a numerical simulation code for multi-dimensional coupled fluid and heat flow of multiphase, multicomponent fluid mixtures in porous and fractured media. This report contains the following sections: (1) Requirements Specification, (2) Design Description, (3) Software Validation Test Plan and Report, (4) Software User Documentation, and (5) Appendices. These sections comprise sequential parts of the Software Life Cycle, and are not intended to stand alone but should be used in conjunction with the TOUGH User's Guide (Pruess, 1987), TOUGH2--A General Purpose Numerical Simulator for Multiphase Fluid and Heat Flow (Pruess, 1991), and the above-referenced TOUGH2 software qualification document. The qualification package is complete with the attached Software Identification Form and executable source code for the single-phase Gas, Effective Continuum method, Saturated/Unsaturated Flow, and Radionuclide Transport modules of TOUGH2

  1. TOUGH2 modeling. Pre- and post processing; TOUGH2 Modellierungen. Prae- und Postprozessing

    Energy Technology Data Exchange (ETDEWEB)

    Frieling, Gerd; Bracke, Guido

    2013-12-15

    GRS is modeling the two-phase flow in porous media using the program TOUGH2. The report describes the TOUGH2 program structure and the essential input parameters. Some of the important physical models are discussed for better understanding of the required data input. The data processing and visualization that is very specific for the GRS work flow Is described in detail. GRS has refined the standard modules EOS7 and EOS7R, the model extensions consider the rock convergence, time dependent boundary conditions and include the direction dependent diffusion or dispersion.

  2. ITOUGH2: Solving TOUGH inverse problems

    Energy Technology Data Exchange (ETDEWEB)

    Finsterle, S.; Pruess, K. [Lawrence Berkeley Laboratory, CA (United States)

    1995-03-01

    ITOUGH2 is a program that provides inverse modeling capabilities for the TOUGH2 code. While the main purpose of ITOUGH2 is to estimate two-phase hydraulic properties of calibrating a TOUGH2 model to laboratory or field data, the information obtained by evaluating parameter sensitivities can also be used to optimize the design of an experiment, and to analyze the uncertainty of model predictions. ITOUGH2 has been applied to a number of laboratory and field experiments on different scales. Three examples are discussed in this paper, demonstrating the code`s capability to support test design, data analysis, and model predictions for a variety of TOUGH problems.

  3. Preface to the Special Issue on TOUGH Symposium 2015

    Science.gov (United States)

    Blanco-Martín, Laura

    2017-11-01

    The TOUGH Symposium 2015 was held in Berkeley, California, September 28-30, 2015. The TOUGH family of codes, developed at the Energy Geosciences Division of Lawrence Berkeley National Laboratory (LBNL), is a suite of computer programs for the simulation of multiphase and multicomponent fluid and heat flows in porous and fractured media with applications in many geosciences fields, such as geothermal reservoir engineering, nuclear waste disposal, geological carbon sequestration, oil and gas reservoirs, gas hydrate research, vadose zone hydrology and environmental remediation. Since the first release in the 1980s, many modifications and enhancements have been continuously made to TOUGH and its various descendants (iTOUGH2, TOUGH+, TOUGH-MP, TOUGHREACT, TOUGH+HYDRATE, TMVOC...), at LBNL and elsewhere. Today, these codes are used worldwide in academia, government organizations and private companies in problems involving coupled hydrological, thermal, biogeochemical and geomechanical processes. The Symposia, organized every 2-3 years, bring together developers and users for an open exchange on recent code enhancements and applications. In 2015, the Symposium was attended by one hundred participants, representing thirty-four nationalities. This Special Issue in Computers & Geosciences gathers extended versions of selected Symposium proceedings related to (i) recent enhancements to the TOUGH family of codes and (ii) coupled flow and geomechanics processes modeling.

  4. Fracture toughness of copper-base alloys for ITER applications: A preliminary report

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, D.J.; Zinkle, S.J.; Rowcliffe, A.F. [Oak Ridge National Lab., TN (United States)

    1997-04-01

    Oxide-dispersion strengthened copper alloys and a precipitation-hardened copper-nickel-beryllium alloy showed a significant reduction in toughness at elevated temperature (250{degrees}C). This decrease in toughness was much larger than would be expected from the relatively modest changes in the tensile properties over the same temperature range. However, a copper-chromium-zirconium alloy strengthened by precipitation showed only a small decrease in toughness at the higher temperatures. The embrittled alloys showed a transition in fracture mode, from transgranular microvoid coalescence at room temperature to intergranular with localized ductility at high temperatures. The Cu-Cr-Zr alloy maintained the ductile microvoid coalescence failure mode at all test temperatures.

  5. Fracture toughness of irradiated and recovered vessel steels

    International Nuclear Information System (INIS)

    Perosanz, F.; Lapena, J.

    1998-01-01

    This paper presents the fracture toughness measurements carried out on three vessel steels in an irradiated condition and after a post-irradiation recovery treatment. A statistical approach and the fracture parameters corresponding to two theoretical models of the fracture tests are used for evaluating toughness. Test results show that the neutron fluence gradually transforms the fracture behaviour of the vessel steels from ductile to brittle and seriously reduces their fracture toughness. The effectiveness of the recovery treatment, as evaluated from the toughness measurements, is confirmed, although the efficiency is not the same for the steels and depends on the evaluation parameter except in the case of almost complete recovery. The recovery effect increases with the received neutron fluence if the toughness values after treatment are compared with those in the irradiated condition rather than those in the as received condition. (orig.)

  6. Strength and low temperature toughness of Fe-13%Ni-Mo alloys

    International Nuclear Information System (INIS)

    Ishikawa, Keisuke; Maruyama, Norio; Tsuya, Kazuo

    1978-01-01

    Mechanical tests were made on newly developed Fe-13%Ni-Mo alloys for eryogenic service. The effects of the additional elements were investigated from the viewpoint of the strength and the low temperature toughness. The alloys added by Al, Ti or V have the better balance of these properties. They did not show low temperature brittleness induced by cleavage fracture in Charpy impact test at 77 K. The microfractography showed the utterly dimple rupture patterns on the broken surface of all specimens. It would be supposed that the cleavage fracture stress is considerably higher than the flow stress. These alloys are superior to some commercial structural materials for low temperature use in the balance between the strength at 300 K and the toughness at 77 K. Additionally, it is noted that these experimental alloys have a good advantage in getting high strength and high toughness by the rather simple heat treatment. (auth.)

  7. Friction weld ductility and toughness as influenced by inclusion morphology

    International Nuclear Information System (INIS)

    Eberhard, B.J.; Schaaf, B.W. Jr.; Wilson, A.D.

    1983-01-01

    Friction welding consistently provides high strength, freedom from fusion defects, and high productivity. However, friction welds in carbon steel exhibit impact toughness and bend ductility that are significantly lower than that of the base metal. The inclusion content and morphology were suspected to be major contributors to the reduction in weld ductility. For this reason, four electric furnace steels - three types of ASTM A516 Grade 70, and an ASTM A737 Grade B steel - were investigated. Friction welds were made by both the inertia and direct drive process variations and the welds evaluated. It was shown that friction welds of inclusion-controlled steels exhibited much improved toughness and bend ductility were demonstrated. Upper shelf impact energy was equivalent to or greater than that of the base metal in the short transverse direction. The transition temperature range for all four materials was shifted to higher temperatures for both types of friction welds. Under the conditions of this test, the direct drive friction welds showed a greater shift than the inertia friction welds. The ductility and toughness of welds in A737 Grade B steel were superior to welds in A516 Grade 70 steels, reflecting the superior properties of the base metal. Welds of the A737 material had usable Charpy V-notch impact toughness of 20 to 30 ft-lb (27 to 41 J) at temperatures as low as -40 0 F (-40 0 C). All the welds had an acicular structure. The differences in properties between the inertia and direct drive friction welds appear associated with microstructural variations. These variations resulted from the different heat inputs and cooling rates of the two process variations were demonstrated. The beneficial effects of inclusion control on toughness and ductility. In addition, it also indicates that additional improvements may be attainable through control of the as-welded microstructure by process manipulation

  8. A direct method to measure the fracture toughness of indium tin oxide thin films on flexible polymer substrates

    International Nuclear Information System (INIS)

    Chang, Rwei-Ching; Tsai, Fa-Ta; Tu, Chin-Hsiang

    2013-01-01

    This work presents a straightforward method to measure the fracture toughness of thin films deposited on flexible substrates. A 200 nm thick indium tin oxide (ITO) thin film is deposited on a 188 μm thick terephthalate (PET) substrate by a radio frequency magnetron sputtering machine. Using nanoindentation to induce brittle fracture on the ITO thin films, the energy release is calculated from integrating the resulting load–depth curve. An approach that directly measures the fracture toughness of thin films deposited on flexible substrates is proposed. A comparison shows that the results of the proposed method agree well with those of other reports. Furthermore, in order to improve the toughness of the ITO thin films, a copper interlayer is added between the ITO thin film and PET substrate. It shows that the fracture toughness of the ITO thin film deposited on the copper interlayer is higher than that of the one without the interlayer, which agrees well with the critical load tested by micro scratch. Further observations on optical and electric performances are also discussed in this work. - Highlights: • A straightforward method to measure the film's toughness • Directly using the load-depth curve of nanoindentation • The toughness is consistent with the critical load tested by micro scratch. • Interlayers can improve the film's toughness. • Optical and electric performances are also discussed

  9. Fracture toughness of oxide-dispersion strengthened copper

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, D.J. [Oak Ridge National Lab., TN (United States)

    1996-10-01

    The fracture toughness of an oxide-dispersion strengthened copper alloy AL-15 has been examined at room temperature and 250{degrees}C, in air and in vacuum (< 10{sup {minus}6} torr). Increasing test temperature causes a significant decrease in the fracture toughness of this material, in either air or vacuum environments. In addition, specimens oriented in the T-L orientation (crack growth parallel to the extrusion direction) show significantly lower toughness than those in the L-T orientation (crack growth perpendicular to the extrusion direction).

  10. A statistical study on fracture toughness data of Japanese RPVS

    International Nuclear Information System (INIS)

    Sakai, Y.; Ogura, N.

    1987-01-01

    In a cooperative study for investigating fracture toughness on pressure vessel steels produced in Japan, a number of heats of ASTM A533B cl.1 and A508 cl.3 steels have been studied. Approximately 3000 fracture toughness data and 8000 mechanical properties data were obtained and filed in a computer data bank. Statistical characterization of toughness data in the transition region has been carried out using the computer data bank. Curve fitting technique for toughness data has been examined. Approach using the function to model the transition behaviours of each toughness has been applied. The aims of fitting curve technique were as follows; (1) Summarization of an enormous toughness data base to permit comparison heats, materials and testing methods; (2) Investigating the relationships among static, dynamic and arrest toughness; (3) Examining the ASME K(IR) curve statistically. The methodology used in this study for analyzing a large quantity of fracture toughness data was found to be useful for formulating a statistically based K(IR) curve. (orig./HP)

  11. TOUGH2 User's Guide Version 2

    International Nuclear Information System (INIS)

    Pruess, K.; Oldenburg, C.M.; Moridis, G.J.

    1999-01-01

    TOUGH2 is a numerical simulator for nonisothermal flows of multicomponent, multiphase fluids in one, two, and three-dimensional porous and fractured media. The chief applications for which TOUGH2 is designed are in geothermal reservoir engineering, nuclear waste disposal, environmental assessment and remediation, and unsaturated and saturated zone hydrology. TOUGH2 was first released to the public in 1991; the 1991 code was updated in 1994 when a set of preconditioned conjugate gradient solvers was added to allow a more efficient solution of large problems. The current Version 2.0 features several new fluid property modules and offers enhanced process modeling capabilities, such as coupled reservoir-wellbore flow, precipitation and dissolution effects, and multiphase diffusion. Numerous improvements in previously released modules have been made and new user features have been added, such as enhanced linear equation solvers, and writing of graphics files. The T2VOC module for three-phase flows of water, air and a volatile organic chemical (VOC), and the T2DM module for hydrodynamic dispersion in 2-D flow systems have been integrated into the overall structure of the code and are included in the Version 2.0 package. Data inputs are upwardly compatible with the previous version. Coding changes were generally kept to a minimum, and were only made as needed to achieve the additional functionalities desired. TOUGH2 is written in standard FORTRAN77 and can be run on any platform, such as workstations, PCs, Macintosh, mainframe and supercomputers, for which appropriate FORTRAN compilers are available. This report is a self-contained guide to application of TOUGH2 to subsurface flow problems. It gives a technical description of the TOUGH2 code, including a discussion of the physical processes modeled, and the mathematical and numerical methods used. Illustrative sample problems are presented along with detailed instructions for preparing input data

  12. Fracture toughness of irradiated stainless steel alloys

    International Nuclear Information System (INIS)

    Mills, W.J.

    1986-01-01

    The postirradiation fracture toughness responses of Types 316 and 304 stainless steel (SS) wrought products, cast CF8 SS and Type 308 SS weld deposit were characterized at 427 0 C using J/sub R/-curve techniques. Fast-neutron irradiation of these alloys caused an order of magnitude reduction in J/sub c/ and two orders of magnitude reduction in tearing modulus at neutron exposures above 10 dpa, where radiation-induced losses in toughness appeared to saturate. Saturation J/sub c/ values for the wrought materials ranged from 28 to 31 kJ/m 2 ; the weld exhibited a saturation level of 11 kJ/m 2 . Maximum allowable flaw sizes for highly irradiated stainless steel components stressed to 90% of the unirradiated yield strength are on the order of 3 cm for the wrought material and 1 cm for the weld. Electron fractographic examination revealed that irradiation displacement damage brought about a transition from ductile microvoid coalescence to channel fracture, associated with local separation along planar deformation bands. The lower saturation toughness value for the weld relative to that for the wrought products was attributed to local failure of ferrite particles ahead of the advancing crack which prematurely initiated channel fracture

  13. Fracture toughness testing of V-4Cr-4Ti at 25{degrees}C and -196{degrees}C

    Energy Technology Data Exchange (ETDEWEB)

    Li, H.X.; Kurtz, R.J. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-10-01

    Measurements of the fracture toughness of the production-scale heat (832665) of V-4Cr-4Ti have been performed at 25{degrees}C and {minus}196{degrees}C using compact tension (CT) specimens. Test specimens were vacuum annealed at either 1000{degrees}C for 1 hour (HT1) or 1050{degrees}C for two hours (HT2). Specimens given the HT1 treatment were annealed after final machining, whereas the HT2 specimens received the 1050{degrees}C anneal at Teledyne Wah Chang prior to final machining. Following machining HT2 specimens were then vacuum annealed at 180{degrees}C for two hours to remove hydrogen. Specimens treated using HT1 had a partially recrystallized microstructure and those treated using HT2 had a fully recrystallized microstructure. The fracture toughness at 25{degrees}C was determined by J-integral tests and at {minus}196{degrees}C by ASTM E 399 type tests. Toughness values obtained at {minus}196{degrees}C were converted to J-integral values for comparison to the 25{degrees}C data. The 25{degrees}C fracture toughness was very high with none of the specimens giving valid results per ASTM criteria. Specimens fractured by microvoid coalescence. The fracture toughness at {minus}196{degrees}C was much lower than that at 25{degrees}C and the fracture surface showed predominantly cleavage features. The present results show a transition from ductile to brittle behavior with decreasing test temperature which is not observed from one-third scale Charpy impact tests. The fracture toughness at {minus}196{degrees}C was still quite high, however, at about 75 kJ/m{sup 2}. Delaminations in planes normal to the thickness direction were seen at both test temperatures. Fracture surfaces inside the delaminations exhibited nearly 100% cleavage facets. The cause of the brittle delaminations was not determined, but will be a subject for further investigation.

  14. The significance of crack-resistance curves to the mixed-mode fracture toughness of human cortical bone

    Energy Technology Data Exchange (ETDEWEB)

    Zimmermann, Elizabeth A.; Launey, Maximilien E.; Ritchie, Robert O.

    2010-03-25

    The majority of fracture mechanics studies on the toughness of bone have been performed under tensile loading. However, it has recently been shown that the toughness of human cortical bone in the transverse (breaking) orientation is actually much lower in shear (mode II) than in tension (mode I); a fact that is physiologically relevant as in vivo bone is invariably loaded multiaxially. Since bone is a material that derives its fracture resistance primarily during crack growth through extrinsic toughening mechanisms, such as crack deflection and bridging, evaluation of its toughness is best achieved through measurements of the crack-resistance or R-curve, which describes the fracture toughness as a function of crack extension. Accordingly, in this study, we attempt to measure for the first time the R-curve fracture toughness of human cortical bone under physiologically relevant mixed-mode loading conditions. We show that the resulting mixed-mode (mode I + II) toughness depends strongly on the crack trajectory and is the result of the competition between the paths of maximum mechanical driving force and 'weakest' microstructural resistance.

  15. Prospering in Tough Economic Times Through Loyal Customers

    Directory of Open Access Journals (Sweden)

    Anderson Rolph

    2014-10-01

    Full Text Available In severe economic downturns, only a few business leaders have the courage and wisdom to invest in customer loyalty to increase profits instead of reflexively cutting costs to try to maintain falling profit margins. Moreover, the usual research and advice tends to focus on how companies can effectively and efficiently reduce costs in order to survive an economic decline. This study contributes to the literature by offering a fresh look at how best to respond in tough economic times by examining companies who have responded traditionally with cost cutting strategies versus companies who instead have invested in customer loyalty. We make the unique and contrarian argument that the latter strategy can be the superior business strategy, which underscores the originality of this investigation. Thus, the purpose of this study is to highlight why investing resources in creating and retaining loyal customers is the best strategy for companies to survive and prosper in tough economic conditions while simultaneously gaining longer-run competitive advantage. Based on quantitative and qualitative survey research methodology, the study findings identify and explain key customer loyalty measures, including: customization for customers, communication interactivity, nurturing of customers, commitment to customers, customer sharing networks, customer focused product assortments, facile exchanges, and customer engagement. Perceptive company executives will measure, benchmark, and regularly compare their performances on these key customer loyalty measures with different customer groups versus their company's past performances, managerial goals, and competitors, then make appropriate adjustments to retain their loyal customers and prosper during tough economic times.

  16. Dependence of Fracture Toughness on Crystallographic Orientation in Single-Crystalline Cubic (β) Silicon Carbide

    Energy Technology Data Exchange (ETDEWEB)

    Pharr, M.; Katoh, Y.; Bei, H.

    2006-01-01

    Along with other desirable properties, the ability of silicon carbide (SiC) to retain high strength after elevated temperature exposures to neutron irradiation renders it potentially applicable in fusion and advanced fission reactors. However, properties of the material such as room temperature fracture toughness must be thoroughly characterized prior to such practical applications. The objective of this work is to investigate the dependence of fracture toughness on crystallographic orientation for single-crystalline β-SiC. X-ray diffraction was first performed on the samples to determine the orientation of the crystal. Nanoindentation was used to determine a hardness of 39.1 and 35.2 GPa and elastic modulus of 474 and 446 GPa for the single-crystalline and polycrystalline samples, respectively. Additionally, crack lengths and indentation diagonals were measured via a Vickers micro-hardness indenter under a load of 100 gf for different crystallographic orientations with indentation diagonals aligned along fundamental cleavage planes. Upon examination of propagation direction of cracks, the cracks usually did not initiate and propagate from the corners of the indentation where the stresses are concentrated but instead from the indentation sides. Such cracks clearly moved along the {1 1 0} family of planes (previously determined to be preferred cleavage plane), demonstrating that the fracture toughness of SiC is comparatively so much lower along this set of planes that the lower energy required to cleave along this plane overpowers the stress-concentration at indentation corners. Additionally, fracture toughness in the <1 1 0> direction was 1.84 MPa·m1/2, lower than the 3.46 MPa·m1/2 measured for polycrystalline SiC (which can serve as an average of a spectrum of orientations), further demonstrating that single-crystalline β-SiC has a strong fracture toughness anisotropy.

  17. Validity of fracture toughness determined with small bend specimens

    International Nuclear Information System (INIS)

    Wallin, K.; Rintamaa, R.; Valo, M.

    1994-02-01

    This report considers the validity of fracture toughness estimates obtained with small bend specimens in relation to fracture toughness estimates obtained with large specimens. The study is based upon the analysis and comparison of actual test results. The results prove the validity of the fracture toughness determined based upon small bend specimens, especially when the results are only used to determine the fracture toughness transition temperature T o . In this case the possible error is typically less than 5 deg C and at most 10 deg C. It can be concluded that small bend specimens are very suitable for the estimation of fracture toughness in the case of brittle fracture, provided the results are corrected for statistical size effects. (orig.). (20 refs., 17 figs.)

  18. The use of thermally expandable microcapsules for increasing the toughness and heal structural adhesives

    Directory of Open Access Journals (Sweden)

    Chiaki Sato

    2011-04-01

    Full Text Available In this research, the effect of thermally expandable microcapsules (TEMs on mode I fracture toughness of structural adhesives were investigated. The single-edge-notch bending (SENB test was used. Firstly, a standard toughness test was performed on adhesives with microcapsules. Secondly, since TEMs start their expansion at approximately 60ºC, the next specimens were fatigue tested expecting a local heating in the notch leading to the desired expansion before being statically loaded for fracture toughness determination. Thirdly, a manual local heating at 90ºC was applied in the notch before the fracture static test. The experimental results were successfully cross-checked through a numerical analysis using the virtual crack closure technique (VCCT based on linear elastic fracture mechanics (LEFM. The major conclusion is that fracture toughness of the modified adhesives increased as the mass fraction of the TEMs increased.

  19. Fracture toughness of Dy123 low porosity bulks at liquid nitrogen temperature

    International Nuclear Information System (INIS)

    Murakami, A.; Otaka, K.; Miura, T.; Iwamoto, A.

    2011-01-01

    Fracture toughness values were measured for Dy123 bulks. Fracture toughness was improved by reducing porosity. Fracture toughness values at 77 K were higher than those at room temperature. Fracture toughness was also improved by Ag addition. In order to evaluate the fracture toughness of DyBa 2 Cu 3 O x (Dy123) low porosity bulks, bending tests of V-notched specimens cut from the bulks were carried out. Fracture toughness evaluations of a conventional Dy123 bulk which had pores were also carried out and effects of elimination of pores on the fracture toughness were investigated. Fracture toughness values at 77 K of the low porosity bulks were higher than those of the porous bulk. These fracture toughness values at 77 K were higher than the values at room temperature. Fracture toughness of the low porosity bulk was improved by Ag addition.

  20. A New Maraging Stainless Steel with Excellent Strength-Toughness-Corrosion Synergy.

    Science.gov (United States)

    Tian, Jialong; Wang, Wei; Babar Shahzad, M; Yan, Wei; Shan, Yiyin; Jiang, Zhouhua; Yang, Ke

    2017-11-10

    A new maraging stainless steel with superior strength-toughness-corrosion synergy has been developed based on an innovative concept of alloy design. The high strength-toughness combination is achieved by forming dispersive nano-sized intermetallic compounds in the soft lath martensitic matrix with a slight amount of residual austenite. The good corrosion resistance is guaranteed by exactly controlling the Co content based on understanding the synergistic effect between Co and Cr. The fine structure characteristics of two dominant strengthening precipitations including Ni₃Ti and Mo-rich phases were finely characterized associated with transmission electron microscope (TEM) and atom probe tomography (APT) analyses. The relationship among microstructure, strength and toughness is discussed. The precipitation mechanism of different precipitates in the new maraging stainless steel is revealed based on the APT analysis.

  1. Formation of tough composite joints

    International Nuclear Information System (INIS)

    Brun, M.K.

    1997-05-01

    Joints which exhibit tough fracture behavior were formed in a composite with a Si/SiC matrix reinforced with Textron SCS-6 fibers with either boron nitride or silicon nitride fiber coatings. In composites with BN coatings fibers were aligned uniaxially, while composites with Si 3 N 4 -coated fibers had a 0/90 degree architecture. Lapped joints (joints with overlapping fingers) were necessary to obtain tough behavior. Geometrical requirements necessary to avoid brittle joint failure have been proposed. Joints with a simple overlap geometry (only a few fingers) would have to be very long in order to prevent brittle failure. Typical failure in these joints is caused by a crack propagating along the interfaces between the joint fingers. Joints of the same overall length, but with geometry changed to be symmetric about the joint centerline and with an extra shear surface exhibited tough fractures accompanied with extensive fiber pullout. The initial matrix cracking of these joints was relatively low because cracks propagated easily through the ends of the fingers. Joints with an optimized stepped sawtooth geometry produced composite-like failures with the stress/strain curves containing an elastic region followed by a region of rising stress with an increase of strain. Increasing the fiber/matrix interfacial strength from 9 to 25 MPa, by changing the fiber coating, increased matrix cracking and ultimate strength of the composite significantly. The best joints had matrix cracking stress and ultimate strength of 138 and 240 MPa, respectively. Joint failure was preceded by multiple matrix cracking in the entire composite. The high strength of the joints will permit building of structures containing joints with only a minor reduction of design stresses

  2. Recent development in low-constraint fracture toughness testing for structural integrity assessment of pipelines

    Science.gov (United States)

    Kang, Jidong; Gianetto, James A.; Tyson, William R.

    2018-03-01

    Fracture toughness measurement is an integral part of structural integrity assessment of pipelines. Traditionally, a single-edge-notched bend (SE(B)) specimen with a deep crack is recommended in many existing pipeline structural integrity assessment procedures. Such a test provides high constraint and therefore conservative fracture toughness results. However, for girth welds in service, defects are usually subjected to primarily tensile loading where the constraint is usually much lower than in the three-point bend case. Moreover, there is increasing use of strain-based design of pipelines that allows applied strains above yield. Low-constraint toughness tests represent more realistic loading conditions for girth weld defects, and the corresponding increased toughness can minimize unnecessary conservatism in assessments. In this review, we present recent developments in low-constraint fracture toughness testing, specifically using single-edgenotched tension specimens, SENT or SE(T). We focus our review on the test procedure development and automation, round-robin test results and some common concerns such as the effect of crack tip, crack size monitoring techniques, and testing at low temperatures. Examples are also given of the integration of fracture toughness data from SE(T) tests into structural integrity assessment.

  3. Interlaminar fracture toughness for composite materials

    International Nuclear Information System (INIS)

    Lee, Kang Yong; Kwon, Soon Man

    1991-01-01

    The new equation of energy release rate for a double cantilever beam specimen is proposed within the framework of the higher order shear deformable plate theory. The interlaminar fracture toughnesses by present theory, ASTM round robin test method and acoustic emission method are compared for thermoset Graphite/Epoxy and thermoplastic AS4/PEEK composites. As a result, the interlaminar fracture toughness values by present theory show good agreement within 5% when compared with ones by ASTM method and it is shown that ones by acoustic emission method yield the lower values than ones by ASTM method. It is observed that the interlaminar fracture toughness of thermoplastic AS4/PEEK composite is about ten times larger than one of thermoset Graphite/Epoxy composite. (Author)

  4. Rapid estimation of fatigue entropy and toughness in metals

    Energy Technology Data Exchange (ETDEWEB)

    Liakat, M.; Khonsari, M.M., E-mail: khonsari@me.lsu.edu

    2014-10-15

    Highlights: • A correlation is developed to predict fatigue entropy and toughness of metals. • Predictions are made based on the thermal response of the materials. • The trend of hysteresis energy and temperature evolutions is discussed. • Predicted results are found to be in good agreement to those measured. - Abstract: An analytical model and an experimental procedure are presented for estimating the rate and accumulation of thermodynamic entropy and fatigue toughness in metals subjected to cyclic uniaxial tension–compression tests. Entropy and plastic strain energy generations are predicted based on the thermal response of a specimen at different levels of material damage. Fatigue tests are performed with cylindrical dogbone specimens made of tubular low-carbon steel 1018 and solid medium-carbon steel 1045, API 5L X52, and Al 6061. The evolution of the plastic strain energy generation, temperature, and thermal response throughout a fatigue process are presented and discussed. Predicted entropy accumulation and fatigue toughness obtained from the proposed method are found to be in good agreement to those obtained using a load cell and an extensometer over the range of experimental and environmental conditions considered.

  5. Rapid estimation of fatigue entropy and toughness in metals

    International Nuclear Information System (INIS)

    Liakat, M.; Khonsari, M.M.

    2014-01-01

    Highlights: • A correlation is developed to predict fatigue entropy and toughness of metals. • Predictions are made based on the thermal response of the materials. • The trend of hysteresis energy and temperature evolutions is discussed. • Predicted results are found to be in good agreement to those measured. - Abstract: An analytical model and an experimental procedure are presented for estimating the rate and accumulation of thermodynamic entropy and fatigue toughness in metals subjected to cyclic uniaxial tension–compression tests. Entropy and plastic strain energy generations are predicted based on the thermal response of a specimen at different levels of material damage. Fatigue tests are performed with cylindrical dogbone specimens made of tubular low-carbon steel 1018 and solid medium-carbon steel 1045, API 5L X52, and Al 6061. The evolution of the plastic strain energy generation, temperature, and thermal response throughout a fatigue process are presented and discussed. Predicted entropy accumulation and fatigue toughness obtained from the proposed method are found to be in good agreement to those obtained using a load cell and an extensometer over the range of experimental and environmental conditions considered

  6. Influence of heat treatment on the strength and fracture toughness of 7N01 aluminum alloy

    Energy Technology Data Exchange (ETDEWEB)

    Li, Bo [School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, 610031, Sichuan (China); Wang, Xiaomin, E-mail: xmwang991011@163.com [School of Life Science and Engineering, Southwest Jiaotong University, Chengdu, 610031, Sichuan (China); Chen, Hui; Hu, Jie [School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, 610031, Sichuan (China); Huang, Cui [School of Life Science and Engineering, Southwest Jiaotong University, Chengdu, 610031, Sichuan (China); Gou, Guoqing [School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, 610031, Sichuan (China)

    2016-09-05

    7N01 aluminum (Al) alloys are treated by five heat treatment methods as peak aging (T6), over aging (T74), high temperature and subsequently low temperature aging (HLA), retrogression and reaging (RRA) and double retrogression and reaging (DRRA). The strength and fracture toughness of the five samples are tested, and the microstructures are investigated by optical microscopy (OM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The results show that 7N01 Al-alloy treated at T6 condition has high strength but low fracture toughness. Compared with T6 treatment, T74 and HLA treatments increase the fracture toughness by 67% and 90% respectively, while the strength decrease by 9% and 17%. RRA process is a proper treatment method for 7N01 which improves the fracture toughness without sacrificing strength. The fracture toughness of DRRA treated alloy is much lower than that of RRA. Quantitative analysis through TEM images shows that the heat treatment affects the mechanical properties of 7N01 Al-alloy highly through changing the precipitates in grains and on grain boundaries, which can be explained by the coherency strengthening mechanism and Orowan mechanism. - Highlights: • Five heat treatments which can change the properties of 7N01 Al alloy were designed. • Quantitative analysis of precipitates was employed to study the mechanism. • RRA treatment can make proper strength/toughness property balances for 7N01 Al alloy.

  7. Influence of heat treatment on the strength and fracture toughness of 7N01 aluminum alloy

    International Nuclear Information System (INIS)

    Li, Bo; Wang, Xiaomin; Chen, Hui; Hu, Jie; Huang, Cui; Gou, Guoqing

    2016-01-01

    7N01 aluminum (Al) alloys are treated by five heat treatment methods as peak aging (T6), over aging (T74), high temperature and subsequently low temperature aging (HLA), retrogression and reaging (RRA) and double retrogression and reaging (DRRA). The strength and fracture toughness of the five samples are tested, and the microstructures are investigated by optical microscopy (OM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The results show that 7N01 Al-alloy treated at T6 condition has high strength but low fracture toughness. Compared with T6 treatment, T74 and HLA treatments increase the fracture toughness by 67% and 90% respectively, while the strength decrease by 9% and 17%. RRA process is a proper treatment method for 7N01 which improves the fracture toughness without sacrificing strength. The fracture toughness of DRRA treated alloy is much lower than that of RRA. Quantitative analysis through TEM images shows that the heat treatment affects the mechanical properties of 7N01 Al-alloy highly through changing the precipitates in grains and on grain boundaries, which can be explained by the coherency strengthening mechanism and Orowan mechanism. - Highlights: • Five heat treatments which can change the properties of 7N01 Al alloy were designed. • Quantitative analysis of precipitates was employed to study the mechanism. • RRA treatment can make proper strength/toughness property balances for 7N01 Al alloy.

  8. Bone toughness at the molecular scale: A model for fracture toughness using crosslinked osteopontin on synthetic and biogenic mineral substrates.

    Science.gov (United States)

    Cavelier, S; Dastjerdi, A K; McKee, M D; Barthelat, F

    2018-05-01

    The most prominent structural components in bone are collagen and mineral. However, bone additionally contains a substantial amount of noncollagenous proteins (most notably of the SIBLING protein family), some of which may act as cohesive/adhesive "binders" for the composite hybrid collagen/mineral scaffolding, whether in the bulk phase of bone, or at its interfaces. One such noncollagenous protein - osteopontin (OPN) - appears to be critical to the deformability and fracture toughness of bone. In the present study, we used a reconstructed synthetic mineral-OPN-mineral interface, and a biogenic (natural tooth dentin) mineral/collagen-OPN-mineral/collagen interface, to measure the fracture toughness of OPN on mineralized substrates. We used this system to test the hypothesis that OPN crosslinking by the enzyme tissue transglutaminase 2 (TG2) that is found in bone enhances interfacial adhesion to increase the fracture toughness of bone. For this, we prepared double-cantilever beam substrates of synthetic pure hydroxyapatite mineral, and of narwhal dentin, and directly apposed them to one another under different intervening OPN/crosslinking conditions, and fracture toughness was tested using a miniaturized loading stage. The work-of-fracture of the OPN interface was measured for different OPN formulations (monomer vs. polymer), crosslinking states, and substrate composition. Noncrosslinked OPN provided negligible adhesion on pure hydroxyapatite, whereas OPN crosslinking (by the chemical crosslinker glutaraldehyde, and TG2 enzyme) provided strong interfacial adhesion for both hydroxyapatite and dentin using monomeric and polymeric OPN. Pre-coating of the substrate beams with monomeric OPN further improved the adhesive performance of the samples, likely by allowing effective binding of this nascent OPN form to mineral/matrix components, with this pre-attachment providing a protein layer for additional crosslinking between the substrates. Copyright © 2018 Elsevier Inc

  9. Investigating liquid-metal embrittlement of T91 steel by fracture toughness tests

    Energy Technology Data Exchange (ETDEWEB)

    Ersoy, Feyzan, E-mail: fersoy@sckcen.be [SCK-CEN (Belgian Nuclear Research Centre), Boeretang 200, B-2400, Mol (Belgium); Department of Materials Science and Engineering, Ghent University (UGent), Technologiepark 903, B-9052, Ghent (Belgium); Gavrilov, Serguei [SCK-CEN (Belgian Nuclear Research Centre), Boeretang 200, B-2400, Mol (Belgium); Verbeken, Kim [Department of Materials Science and Engineering, Ghent University (UGent), Technologiepark 903, B-9052, Ghent (Belgium)

    2016-04-15

    Heavy liquid metals such as lead bismuth eutectic (LBE) are chosen as the coolant to innovative Generation IV (Gen IV) reactors where ferritic/martensitic T91 steel is a candidate material for high temperature applications. It is known that LBE has a degrading effect on the mechanical properties of this steel. This degrading effect, which is known as liquid metal embrittlement (LME), has been screened by several tests such as tensile and small punch tests, and was most severe in the temperature range from 300 °C to 425 °C. To meet the design needs, mechanical properties such as fracture toughness should be addressed by corresponding tests. For this reason liquid-metal embrittlement of T91 steel was investigated by fracture toughness tests at 350 °C. Tests were conducted in Ar-5%H{sub 2} and LBE under the same experimental conditions Tests in Ar-5%H{sub 2} were used as reference. The basic procedure in the ASTM E 1820 standard was followed to perform tests and the normalization data reduction (NDR) method was used for the analysis. Comparison of the tests demonstrated that the elastic–plastic fracture toughness (J{sub 1C}) of the material was reduced by a factor in LBE and the fracture mode changed from ductile to quasi-cleavage. It was also shown that the pre-cracking environment played an important role in observing LME of the material since it impacts the contact conditions between LBE and steel at the crack tip. It was demonstrated that when specimens were pre-cracked in air and tested in LBE, wetting of the crack surface by LBE could not be achieved. When specimens were pre-cracked in LBE though, they showed a significant reduction in fracture toughness.

  10. A proposed standard round compact specimen for plane strain fracture toughness testing

    Science.gov (United States)

    Underwood, J. H.; Newman, J. C., Jr.; Seeley, R. R.

    1980-01-01

    A round, disk-shaped specimen is proposed as a standard test specimen for addition to ASTM Test for Plane-Strain Fracture Toughness of Metallic Materials (E 399-78A). The specimen is diametrically cracked, and loaded in the same way as the existing standard compact specimen. Tests and analyses were performed to verify that the proposed round compact specimen and associated stress intensity factor K solution are appropriate for a standard plane strain fracture toughness test. The use of the round compact specimen for other fracture tests is described.

  11. Effects of electric field on the fracture toughness (KIc) of ceramic PZT

    International Nuclear Information System (INIS)

    Goljahi, Sam; Lynch, Christopher S

    2013-01-01

    This work was motivated by the observation that a small percentage of the ceramic lead zirconate titanate (PZT) parts in a device application, one that requires an electrode pattern on the PZT surface, developed fatigue cracks at the edges of the electrodes; yet all of the parts were subjected to similar loading. To obtain additional information on the fracture behavior of this material, similar specimens were run at higher voltage in the laboratory under a microscope to observe the initiation and growth of the fatigue cracks. A sequence of experiments was next performed to determine whether there were fracture toughness variations that depended on material processing. Plates were cut from a single bar in different locations and the Vickers indentation technique was used to measure the relative fracture toughness as a function of position along the bar. Small variations in toughness were found, that may account for some of the devices developing fatigue cracks and not others. Fracture toughness was measured next as a function of electric field. The surface crack in flexure technique was modified to apply an electric field perpendicular to a crack. The results indicate that the fracture toughness drops under a positive electric field and increases under a negative electric field that is less than the coercive field, but as the negative coercive field is approached the fracture toughness drops. Examination of the fracture surfaces using an optical microscope and a surface profilometer reveal the initial indentation crack shape and (although less accurately) the crack shape and size at the transition from stable to unstable growth. These results are discussed in terms of a ferroelastic toughening mechanism that is dependent on electric field. (paper)

  12. Effects of electric field on the fracture toughness (KIc) of ceramic PZT

    Science.gov (United States)

    Goljahi, Sam; Lynch, Christopher S.

    2013-09-01

    This work was motivated by the observation that a small percentage of the ceramic lead zirconate titanate (PZT) parts in a device application, one that requires an electrode pattern on the PZT surface, developed fatigue cracks at the edges of the electrodes; yet all of the parts were subjected to similar loading. To obtain additional information on the fracture behavior of this material, similar specimens were run at higher voltage in the laboratory under a microscope to observe the initiation and growth of the fatigue cracks. A sequence of experiments was next performed to determine whether there were fracture toughness variations that depended on material processing. Plates were cut from a single bar in different locations and the Vickers indentation technique was used to measure the relative fracture toughness as a function of position along the bar. Small variations in toughness were found, that may account for some of the devices developing fatigue cracks and not others. Fracture toughness was measured next as a function of electric field. The surface crack in flexure technique was modified to apply an electric field perpendicular to a crack. The results indicate that the fracture toughness drops under a positive electric field and increases under a negative electric field that is less than the coercive field, but as the negative coercive field is approached the fracture toughness drops. Examination of the fracture surfaces using an optical microscope and a surface profilometer reveal the initial indentation crack shape and (although less accurately) the crack shape and size at the transition from stable to unstable growth. These results are discussed in terms of a ferroelastic toughening mechanism that is dependent on electric field.

  13. Isolation of Aramid Nanofibers for High Strength and Toughness Polymer Nanocomposites.

    Science.gov (United States)

    Lin, Jiajun; Bang, Sun Hwi; Malakooti, Mohammad H; Sodano, Henry A

    2017-03-29

    The development of nanoscale reinforcements that can be used to improve the mechanical properties of a polymer remains a challenge due to the long-standing difficulties with exfoliation and dispersion of existing materials. The dissimilar chemical nature of common nanofillers (e.g., carbon nanotubes, graphene) and polymeric matrix materials is the main reason for imperfect filler dispersion and, consequently, low mechanical performance of their composites relative to theoretical predictions. Here, aramid nanofibers that are intrinsically dispersible in many polymers are prepared from commercial aramid fibers (Kevlar) and isolated through a simple, scalable, and low-cost controlled dissolution method. Integration of the aramid nanofibers in an epoxy resin results in nanocomposites with simultaneously improved elastic modulus, strength, and fracture toughness. The improvement of these two mutually exclusive properties of nanocomposites is comparable to the enhancement of widely reported carbon nanotube reinforced nanocomposites but with a cost-effective and more feasible method to achieve uniform and stable dispersion. The results indicate the potential for aramid nanofibers as a new class of reinforcements for polymers.

  14. Fracture toughness properties of rocks in Olkiluoto: Laboratory measurements 2008-2009

    Energy Technology Data Exchange (ETDEWEB)

    Siren, T.

    2012-05-15

    In Olkiluoto an underground rock characterization facility (ONKALO) for the final disposal site of spent nuclear fuel has been under thorough research many years, but further knowledge is needed on fracture toughness parameters. Fracture toughness parameters are important for example in fracture mechanics prediction for Posiva's Olkiluoto Spalling Experiment (POSE). This working report describes a laboratory campaign that was done between 2008 and 2009. The campaign aimed at determining the fracture mechanics parameters as well as density and ultrasonic velocities for Olkiluoto rocks. The specimens delivered were selected by Posiva; the core showed no damage and the quality of the delivered cores was good with varying sample diameter. Most of the test samples (9 out of 12) are gneissic rock. The Mode I fracture toughness was determined using two different methods to account for two different fracturing directions. The methods are the Chevron Bend (CB) test as proposed in the ISRM Suggested Method and a method based on the Brazilian Disk (BD) experiment. The Mode II fracture toughness was determined using the Punch-Through Shear with Confining Pressure experiment on the remaining pieces from the CB testing. The scatter in the results is very large, even within one piece of core sample. Usually the scatter of results is less than 5 %. The high scatter in the data at hand is believed to be due to the very inhomogeneous nature of the rock material. The magnitude of the determined Mode I fracture toughness compares well with available reported data for medium to coarse grained granitoide rocks. However the scatter of the mode II fracture toughness values is higher than experienced on other rock types, but the variability is reasonable for the inhomogeneous rock type. Distinguishing the fracture toughness values for different anisotropy directions would require more thorough testing with quality samples at different anisotropy directions. However since fracture

  15. Correlation of fracture toughness with tensile properties for irradiated 20% cold-worked 316 stainless steel

    International Nuclear Information System (INIS)

    Hamilton, M.L.; Garner, F.A.; Wolfer, W.G.

    1983-08-01

    A correlation has been developed which allows an estimate to be made of the toughness of austenitic alloys using more easily obtained tensile data. Tensile properties measured on 20% cold-worked AISI 316 specimens made from ducts and cladding irradiated in EBR-II were used to predict values for the plane strain fracture toughness according to a model originally developed by Krafft. Some microstructural examination is required to determine a parameter designated as the process zone size. In contrast to the frequently employed Hahn-Rosenfeld model, this model gives results which agree with recent experimental determinations of toughness performed in the transgranular failure regime

  16. Fracture toughness of dentin/resin-composite adhesive interfaces.

    Science.gov (United States)

    Tam, L E; Pilliar, R M

    1993-05-01

    The reliability and validity of tensile and shear bond strength determinations of dentin-bonded interfaces have been questioned. The fracture toughness value (KIC) reflects the ability of a material to resist crack initiation and unstable propagation. When applied to an adhesive interface, it should account for both interfacial bond strength and inherent defects at or near the interface, and should therefore be more appropriate for characterization of interface fracture resistance. This study introduced a fracture toughness test for the assessment of dentin/resin-composite bonded interfaces. The miniature short-rod specimen geometry was used for fracture toughness testing. Each specimen contained a tooth slice, sectioned from a bovine incisor, to form the bonded interface. The fracture toughness of an enamel-bonded interface was assessed in addition to the dentin-bonded interfaces. Tensile bond strength specimens were also prepared from the dentin surfaces of the cut bovine incisors. A minimum of ten specimens was fabricated for each group of materials tested. After the specimens were aged for 24 h in distilled water at 37 degrees C, the specimens were loaded to failure in an Instron universal testing machine. There were significant differences (p adhesives tested. Generally, both the fracture toughness and tensile bond strength measurements were highest for AllBond 2, intermediate for 3M MultiPurpose, and lowest for Scotchbond 2. Scanning electron microscopy of the fractured specimen halves confirmed that crack propagation occurred along the bond interface during the fracture toughness test. It was therefore concluded that the mini-short-rod fracture toughness test provided a valid method for characterization of the fracture resistance of the dentin-resin composite interface.

  17. Small Scale Yielding Correction of Constraint Loss in Small Sized Fracture Toughness Test Specimens

    International Nuclear Information System (INIS)

    Kim, Maan Won; Kim, Min Chul; Lee, Bong Sang; Hong, Jun Hwa

    2005-01-01

    Fracture toughness data in the ductile-brittle transition region of ferritic steels show scatter produced by local sampling effects and specimen geometry dependence which results from relaxation in crack tip constraint. The ASTM E1921 provides a standard test method to define the median toughness temperature curve, so called Master Curve, for the material corresponding to a 1T crack front length and also defines a reference temperature, T 0 , at which median toughness value is 100 MPam for a 1T size specimen. The ASTM E1921 procedures assume that high constraint, small scaling yielding (SSY) conditions prevail at fracture along the crack front. Violation of the SSY assumption occurs most often during tests of smaller specimens. Constraint loss in such cases leads to higher toughness values and thus lower T 0 values. When applied to a structure with low constraint geometry, the standard fracture toughness estimates may lead to strongly over-conservative estimates. A lot of efforts have been made to adjust the constraint effect. In this work, we applied a small-scale yielding correction (SSYC) to adjust the constraint loss of 1/3PCVN and PCVN specimens which are relatively smaller than 1T size specimen at the fracture toughness Master Curve test

  18. More progress on tough graphs -- The Y2K report

    NARCIS (Netherlands)

    Bauer, D.; Broersma, Haitze J.; Schmeichel, E.

    2000-01-01

    We now know that not every $2$-tough graph is hamiltonian. In fact for every $\\epsilon > 0$, there exists a ($9/4 - \\epsilon$) - tough nontraceable graph. We continue our quadrennial survey of results that relate the toughness of a graph to its cycle structure.

  19. Effect of hydrogen on the fracture toughness of 17-4 PH stainless steel

    International Nuclear Information System (INIS)

    Capeletti, T.L.

    1976-01-01

    Fracture toughness (K/sub c/) of 17-4 PH stainless steel decreased significantly with increased hydrogen test pressure for a variety of heat treatment conditions: solution annealed, underaged, peak-aged, and overaged. Minimum toughness (13 MPa√m) was obtained with peak-aged samples tested in 69.5-MPa hydrogen; toughness was maximum (100 MPa√m) for samples tested in helium. Aging treatments increased the hardness from 28 R/sub c/ for solution-annealed material to 42 R/c/ for peak-aged material and correspondingly decreased the fracture toughness in high-pressure hydrogen (K/sub H/) from 31 to 13 MPa√m. However, increased hardness had no substantial effect on the K/sub c/ in helium. Fracture mechanism changed from predominantly ductile rupture in helium to cleavage in 69.5-MPa hydrogen, with mixed-mode fractures at lower hydrogen pressure (3.5-MPa). On the basis of these data, 17-4 PH stainless steel is not recommended for hydrogen service

  20. Effects of Post-Weld Heat Treatment on the Microstructure and Toughness of Flash Butt Welded High-Strength Low-Alloy Steel

    Science.gov (United States)

    Shajan, Nikhil; Arora, Kanwer Singh; Asati, Brajesh; Sharma, Vikram; Shome, Mahadev

    2018-04-01

    Effect of post-weld heat treatment on the weld microstructure, texture, and its correlation to the toughness of flash butt welded joints were investigated. Upon flash butt welding, the α and γ-fiber in the parent material converted to Goss (110)[001], rotated Goss (110)[1 \\bar{1} 0], and rotated cube (001)[1 \\bar{1} 0], (001)[ \\overline{11} 0] textures along the fracture plane. Formation of these detrimental texture components was a result of shear deformation and recrystallization of austenite at temperatures above T nr resulting in a drop of toughness at the weld zone. Inter-critical and sub-critical annealing cycles proved to be less effective in reducing the Goss (110)[001], rotated Goss (110)[1 \\bar{1} 0], and rotated cube (001)[1 \\bar{1} 0], (001)[ \\overline{11} 0] texture components, and therefore, toughness values remained unaffected. Post-weld heat treatment in the austenite phase field at 1000 °C for 5 seconds resulted in the formation of new grains with different orientations leading to a reduction in the texture intensities of both Goss and rotated Goss components and therefore improved weld zone toughness. Prolonged annealing time was found to be ineffective in improving the toughness due to grain growth.

  1. Evaluation of WWER-1000 vessel materials fracture toughness

    International Nuclear Information System (INIS)

    Grinik, Eh.U.; Revka, V.N.; Chirko, L.I.; Chajkovskij, Yu.V.

    2007-01-01

    The lifetime of WWER-1000-type reactor vessels is finally conditioned by the fracture toughness (crack growth resistance) of RPV materials. Up to now in line with the regulations the fracture toughness is characterized by the critical temperature of brittleness determined by the results of the Charpy specimen impact testing. Such approach is typical for all countries operating the water pressure reactors. However, regulatory approach is known from the western specialists not always to characterize adequately the crack growth resistance of the vessel materials and in some cases to underestimate their characteristics in the reference state that leads to unreasonably high conservatism. Excessive conservatism may lead to the invalid restrictions in the operating modes and the service life of the reactor vessel. Therefore there appeared the necessity to apply another approaches based on the state-of-the-art experimental methods of the fracture mechanics and allowing evaluating the fracture toughness parameters sufficiently. The paper presents the results of the comparison of the regulatory approach and the Master curve approach from the point of view of the adequate determination of the vessel material crack growth resistance parameters. Analysis of the experimental data of the surveillance specimens illustrated the potential possibility of applying the new statistical method for the WWER-1000- type reactor vessel lifetime extension

  2. Effects of stitching on fracture toughness of uniweave textile graphite/epoxy laminates

    Science.gov (United States)

    Sankar, Bhavani V.; Sharma, Suresh

    1995-01-01

    The effects of through-the-thickness stitching on impact damage resistance, impact damage tolerance, and Mode 1 and Mode 2 fracture toughness of textile graphite/epoxy laminates were studied experimentally. Graphite/epoxy laminates were fabricated from AS4 graphite uniweave textiles and 3501-6 epoxy using Resin Transfer Molding. The cloths were stitched with Kevlar(tm) and glass yarns before resin infusion. Delamination was implanted during processing to simulate impact damage. Sublaminate buckling tests were performed in a novel fixture to measure Compression After Impact (CAI) strength of stitched laminates. The results show that CAI strength can be improved up to 400% by through-the-thickness stitching. Double Cantilever Beam tests were performed to study the effect of stitching on Mode 1 fracture toughness G(sub 1c). It was found that G(sub 1c) increased 30 times for a low stitching density of 16 stitches/sq in. Mode 2 fracture toughness was measured by testing the stitched beams in End Notch Flexure tests. Unlike in the unstitiched beams, crack propagation in the stitched beams was steady. The current formulas for ENF tests were not found suitable for determining G(sub 2C) for stitched beams. Hence two new methods were developed - one based on crack area measured from ultrasonic C-scanning and the other based on equivalent crack area measured from the residual stiffness of the specimen. The G(sub 2c) was found to be at least 5-15 times higher for the stitched laminates. The mechanisms by which stitching increases the CAI strength and fracture toughness are discussed.

  3. Prediction of fracture toughness based on experiments with sub-size specimens in the brittle and ductile regimes

    Energy Technology Data Exchange (ETDEWEB)

    Mahler, Michael, E-mail: Michael.Mahler@kit.edu; Aktaa, Jarir

    2016-04-15

    For determination of fracture toughness in the brittle regime or ductile fracture in the upper shelf region, special standard specifications are in use e.g. ASTM E399 or ASTM E1820. Due to the rigorous size requirements for specimen testing, it is necessary to use big specimens. To circumvent this problem an approach based on finite element (FE) simulations using the cohesive zone model (CZM) is used. The parameters of the cohesive zone model have been determined using sub-size specimens. With the identified parameters, simulations of standard-size specimens have been performed to successfully predict fracture toughness of standard-size specimens in the brittle and ductile regimes. The objective is to establish small size testing technology for the determination of fracture toughness. - Highlights: • Prediction of fracture toughness on standard-size specimens. • Valid fracture toughness based on sub-size specimens. • Triaxiality dependent cohesive zone model. • Approach works independent on fracture appearance (brittle, ductile).

  4. An evaluation of fracture toughness of bituminous coal

    International Nuclear Information System (INIS)

    Pathan, A.G.

    2005-01-01

    The role of fracture mechanics in the design of rock structures is vitally important. However, because of the complexities of rock structures and lack of understanding of the fundamentals of the failure mechanism, it has become customary to use the engineering properties approach in the design of stable rock structures. Recently considerable attention has been given and attempts are being made to apply the fracture mechanics approach to the design of safe mining structures. In mining engineering the fracture mechanics may be applied to calculate the formation of fracture zones around mine opening, thus estimating support requirements and formulating guide lines for the selection of mine roadway support system. The research work presented here is concerned with the evaluation of fracture toughness of coal under laboratory conditions. Diametral compression test method is used to determine the fracture toughness parameter of coal in the opening model failure. The effect of crack length and dimensionless crack length on the fracture toughness was studied also. A laboratory investigation of fracture toughness of coal in tensile mode failure has led to the conclusion that fracture toughness could be treated as a material property. (author)

  5. Sensitivity of Microstructural Factors Influencing the Impact Toughness of Hypoeutectoid Steels with Ferrite-Pearlite Structure using Multiple Regression Analysis

    International Nuclear Information System (INIS)

    Lee, Seung-Yong; Lee, Sang-In; Hwang, Byoung-chul

    2016-01-01

    In this study, the effect of microstructural factors on the impact toughness of hypoeutectoid steels with ferrite-pearlite structure was quantitatively investigated using multiple regression analysis. Microstructural analysis results showed that the pearlite fraction increased with increasing austenitizing temperature and decreasing transformation temperature which substantially decreased the pearlite interlamellar spacing and cementite thickness depending on carbon content. The impact toughness of hypoeutectoid steels usually increased as interlamellar spacing or cementite thickness decreased, although the impact toughness was largely associated with pearlite fraction. Based on these results, multiple regression analysis was performed to understand the individual effect of pearlite fraction, interlamellar spacing, and cementite thickness on the impact toughness. The regression analysis results revealed that pearlite fraction significantly affected impact toughness at room temperature, while cementite thickness did at low temperature.

  6. Fractal model for estimating fracture toughness of carbon nanotube reinforced aluminum oxide

    International Nuclear Information System (INIS)

    Rishabh, Abhishek; Joshi, Milind R.; Balani, Kantesh

    2010-01-01

    The current work focuses on predicting the fracture toughness of Al 2 O 3 ceramic matrix composites using a modified Mandelbrot's fractal approach. The first step confirms that the experimental fracture toughness values fluctuate within the fracture toughness range predicted as per the modified fractal approach. Additionally, the secondary reinforcements [such as carbon nanotubes (CNTs)] have shown to enhance the fracture toughness of Al 2 O 3 . Conventional fractural toughness evaluation via fractal approach underestimates the fracture toughness by considering the shortest crack path. Hence, the modified Mandelbrot's fractal approach considers the crack propagation along the CNT semicircumferential surface (three-dimensional crack path propagation) for achieving an improved fracture toughness estimation of Al 2 O 3 -CNT composite. The estimations obtained in the current approach range within 4% error regime of the experimentally measured fracture toughness values of the Al 2 O 3 -CNT composite.

  7. Toughness degradation evaluation of low alloyed steels by electrical resistivity

    Energy Technology Data Exchange (ETDEWEB)

    Nahm, S H; Yu, K M; Kim, S C [Korea Research Inst. of Standards and Science, Taejon (Korea, Republic of); Kim, A [Department of Mechanical Engineering, Kongju Univ., Kongju, Chungnam (Korea, Republic of)

    1997-09-01

    Remaining life of turbine rotors with a crack can be assessed by the fracture toughness on the aged rotors at service temperature. DC potential drop measurement system was constructed in order to evaluate material toughness nondestructively. Test material was 1Cr-1Mo-0.25V steel used widely for turbine rotor material. Seven kinds of specimen with different degradation levels were prepared according to isothermal aging heat treatment at 630 deg. C. Electrical resistivity of test material was measured at room temperature. It was observed that material toughness and electrical resistivity decreased with the increase of degradation. The relationship between fracture toughness and electrical resistivity was investigated. Fracture toughness of a test material may be determined nondestructively by electrical resistivity. (author). 13 refs, 7 figs.

  8. TOUGH2-GRS version 1. User manual

    Energy Technology Data Exchange (ETDEWEB)

    Navarro, Martin; Eckel, Jens

    2016-07-15

    TOUGH2 is a code for the simulation of multi-phase flow processes in porous media that has been developed by the Lawrence Berkeley National Laboratory, California, USA. Since 1991, GRS has been using the code for process analyses and safety assessments for deep geological repositories and has extended the code by several processes that are relevant for repository systems. The TOUGH2 source code that has been developed further by GRS is referred to as TOUGH2-GRS. The present report presents code version 1.1.g, which was developed in project UM13 A 03400 sponsored by the German Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety (BMUB).

  9. Tensile and fracture toughness properties of MA957: implications to the development of nanocomposited ferritic alloys

    International Nuclear Information System (INIS)

    Alinger, M.J.; Odette, G.R.; Lucas, G.E.

    2002-01-01

    A study to explore approaches to optimizing nanocomposited ferritic alloys was carried out on dispersion strengthened mechanically alloyed (MA) MA957, in the form of extruded bar stock. Previous studies had indicated that this alloy manifested superior high temperature strength and radiation stability, but was extremely brittle in notch impact tests. Thus our objective was to develop a combination of tensile, fracture toughness and microstructural data to clarify the basis for this brittle behavior. To this end, tensile properties and fracture toughness were characterized as a function of temperature in various orientations relative to the grain and inclusion structures. This database along with extensive fractography suggests that brittleness is due to the presence of a large volume fraction of impurity alumina stringers. In orientations where the effects of the stringers are reduced, much higher toughness was observed. These results provide a path for alloy development approach to achieve high strength and toughness

  10. Tensile and fracture toughness properties of MA957: implications to the development of nanocomposited ferritic alloys

    Science.gov (United States)

    Alinger, M. J.; Odette, G. R.; Lucas, G. E.

    2002-12-01

    A study to explore approaches to optimizing nanocomposited ferritic alloys was carried out on dispersion strengthened mechanically alloyed (MA) MA957, in the form of extruded bar stock. Previous studies had indicated that this alloy manifested superior high temperature strength and radiation stability, but was extremely brittle in notch impact tests. Thus our objective was to develop a combination of tensile, fracture toughness and microstructural data to clarify the basis for this brittle behavior. To this end, tensile properties and fracture toughness were characterized as a function of temperature in various orientations relative to the grain and inclusion structures. This database along with extensive fractography suggests that brittleness is due to the presence of a large volume fraction of impurity alumina stringers. In orientations where the effects of the stringers are reduced, much higher toughness was observed. These results provide a path for alloy development approach to achieve high strength and toughness.

  11. Fracture toughness of mountain gorilla (Gorilla gorilla beringei) food plants.

    Science.gov (United States)

    Elgart-Berry, Alison

    2004-04-01

    Mountain gorillas, the largest extant primates, subsist almost entirely on plant matter. Moreover, their diet includes a substantial amount of structural material, such as bark and stems, which other primates tend to avoid. Accordingly, the robust masticatory apparatus of gorillas may be adaptive to this presumably tough diet; however, quantitative information on this subject is lacking. In this study the fracture toughness of mountain gorilla foods was examined for the first time. Samples of 44 food plants from Bwindi-Impenetrable National Park (BINP) and Mgahinga Gorilla National Park (MGNP) were tested. These parks are inhabited by two gorilla populations that regarded by some as being distinct at the subspecific taxonomic level. Although food toughness did not differ between the two populations, both diets contained tough items. Tree barks were the toughest food items (varying from 0.23 to 8.2 kJ/m2), followed by shrub barks, pith, and stems. The toughness of leaves and fruit was negligible compared to that of bark. The toughness of bamboo was low in comparison to the toughest food items. Accordingly, the prominent toughness of bark, pith, and stems may be key factors in the evolution of orofacial robusticity in mountain gorillas. Copyright 2004 Wiley-Liss, Inc.

  12. Fracture capacity of HFIR vessel with random crack size and toughness

    International Nuclear Information System (INIS)

    Chang, S.J.

    1994-01-01

    The probability of fracture versus a range of applied hoop stresses along the High Flux Isotope Reactor vessel is obtained as an estimate of its fracture capacity. Both the crack size and the fracture toughness are assumed to be random variables and subject to assumed distribution functions. Possible hoop stress is based on the numerical solution of the vessel response by applying a point pressure-pulse at the center of the fluid volume within the vessel. Both the fluid-structure interaction and radiation embrittlement are taken into consideration. Elastic fracture mechanics is used throughout the analysis. The probability function of fracture for a single crack due to either a variable crack depth or a variable toughness is derived. Both the variable crack size and the variable toughness are assumed to follow known distributions. The probability of vessel fracture with multiple number of cracks is then obtained as a function of the applied hoop stress. The probability of fracture function is, then, extended to include different levels of confidence and variability. It, therefore, enables one to estimate the high confidence and low probability fracture capacity of the reactor vessel under a range of accident loading conditions

  13. Single specimen fracture toughness determination procedure using instrumented impact test

    International Nuclear Information System (INIS)

    Rintamaa, R.

    1993-04-01

    In the study a new single specimen test method and testing facility for evaluating dynamic fracture toughness has been developed. The method is based on the application of a new pendulum type instrumented impact tester equipped with and optical crack mouth opening displacement (COD) extensometer. The fracture toughness measurement technique uses the Double Displacement Ratio (DDR) method, which is based on the assumption that the specimen is deformed as two rigid arms that rotate around an apparent centre of rotation. This apparent moves as the crack grows, and the ratio of COD versus specimen displacement changes. As a consequence the onset ductile crack initiation can be detected on the load-displacement curve. Thus, an energy-based fracture toughness can be calculated. In addition the testing apparatus can use specimens with the Double ligament size as compared with the standard Charpy specimen which makes the impact testing more appropriate from the fracture mechanics point of view. The novel features of the testing facility and the feasibility of the new DDR method has been verified by performing an extensive experimental and analytical study. (99 refs., 91 figs., 27 tabs.)

  14. The fracture toughness of Type 316 steel and weld metal

    International Nuclear Information System (INIS)

    Picker, C.

    This paper describes the results of fracture toughness tests on Type 316 steel and Manual Metal Arc (MMA) weld metal over a range of temperatures from 20 deg. C to 550 deg. C, and includes the effects on toughness of specimen size, post weld heat treatment and thermal ageing. The conclusions reached are that Type 316 steel possesses a superior toughness to the weld metal in the as-welded or stress relieved conditions but the toughness of the steel is degraded to a level similar to that of the weld metal following thermal ageing at temperatures over 600 deg. C. Relatively short term thermal ageing in the temperature range 370 deg. C to 450 deg. C does not appear to affect the toughness of either Type 316 steel or weld metal. (author)

  15. The dose dependence of fracture toughness Of F82H steel

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, M. [Oak Ridge National Laboratory, Materials Science and Technology Div., TN (United States); Tanigawa, H.; Ando, M.; Shiba, K. [Japan Atomic Energy Agency, Tokai-mura, Naga-gun, Ibaraki-ken (Japan); Odette, G. [UCSB, Santa-Barbara, Dept. of Mechanical Engineering UCSB, AK (United States); Hirose, T. [Blanket Engineering Group, Japan Atomic Energy Agency, Naka, Ibaraki (Japan); Klueh, R.L. [Oak Ridge Noational Laboratory, TN (United States)

    2007-07-01

    Full text of publication follows: The ferritic-martensitic steel F82H is a primary candidate low-activation material for fusion applications, and it is being investigated in the joint U.S. Department of Energy-Japan Atomic Energy Agency. As a part of this program, several capsules containing fracture toughness specimens were irradiated in High-Flux Isotope Reactor. These specimens were irradiated to a wide range of doses from 3.5 to 25 dpa. The range of irradiation temperature was from 250 deg. C to 500 deg. C. This paper summarizes the changes in fracture toughness transition temperature and decrease in the ductile fracture toughness as result of various irradiation conditions. It is shown that in the 3.5 to 25 dpa dose range, irradiation temperature plays the key rote in determination of the shift of the transition temperature. Highest embrittlement observed at 250 deg.C and the lowest at 500 deg. C. At a given irradiation temperature, shift of the fracture toughness transition temperature increases slightly with dose within the studied dose range. It appears that main gain in transition temperature shift occurred during initial {approx}5 dpa of irradiation. The present data are compared to the available published trends. (authors)

  16. Effect of Grain Boundary Character Distribution on the Impact Toughness of 410NiMo Weld Metal

    DEFF Research Database (Denmark)

    Divya, M.; Das, Chitta Ranjan; Chowdhury, Sandip Ghosh

    2016-01-01

    Grain boundary character distributions in 410NiMo weld metal were studied in the as-welded, first-stage, and second-stage postweld heat treatment (PWHT) conditions, and these were correlated with the Charpy-V impact toughness values of the material. The high impact toughness values in the weld...... metal in the as-welded and first-stage PWHT conditions compared to that in the second-stage condition are attributed to the higher fraction of low-energy I pound boundaries. A higher volume fraction of retained austenite and coarser martensite after second-stage PWHT accompanied by the formation...... in the impact toughness. In addition to this, grain refinement during 4-hour PWHT in the second stage also increased the toughness of the weld metal....

  17. Tough graphene-polymer microcellular foams for electromagnetic interference shielding.

    Science.gov (United States)

    Zhang, Hao-Bin; Yan, Qing; Zheng, Wen-Ge; He, Zhixian; Yu, Zhong-Zhen

    2011-03-01

    Functional polymethylmethacrylate (PMMA)/graphene nanocomposite microcellular foams were prepared by blending of PMMA with graphene sheets followed by foaming with subcritical CO(2) as an environmentally benign foaming agent. The addition of graphene sheets endows the insulating PMMA foams with high electrical conductivity and improved electromagnetic interference (EMI) shielding efficiency with microwave absorption as the dominant EMI shielding mechanism. Interestingly, because of the presence of the numerous microcellular cells, the graphene-PMMA foam exhibits greatly improved ductility and tensile toughness compared to its bulk counterpart. This work provides a promising methodology to fabricate tough and lightweight graphene-PMMA nanocomposite microcellular foams with superior electrical and EMI shielding properties by simultaneously combining the functionality and reinforcement of the graphene sheets and the toughening effect of the microcellular cells.

  18. Potential impact of enhanced fracture-toughness data on pressurized-thermal-shock analysis

    International Nuclear Information System (INIS)

    Dickson, T.L.; Theiss, T.J.

    1990-01-01

    The Heavy Section Steel Technology (HSST) Program is involved with the generation of ''enhanced'' fracture-initiation toughness and fracture-arrest toughness data of prototypic nuclear reactor vessel steels. These two sets of data are enhanced because they have distinguishing characteristics that could potentially impact PWR pressure vessel integrity assessments for the pressurized-thermal shock (PTS) loading condition which is a major plant-life extension issue to be confronted in the 1990's. Currently, the HSST Program is planning experiments to verify and quantify, for A533B steel, the distinguishing characteristic of elevated initiation-fracture toughness for shallow flaws which has been observed for other steels. Deterministic and probabilistic fracture-mechanics analyses were performed to examine the influence of the enhanced initiation and arrest fracture-toughness data on the cleavage fracture response of a nuclear reactor pressure vessel subjected to PTS loading. The results of the analyses indicated that application of the enhanced K Ia data does reduce the conditional probability of failure P(F|E); however, it does not appear to have the potential to significantly impact the results of PTS analyses. The application of enhanced fracture-initiation-toughness data for shallow flaws also reduces P(F|E), but it does appear to have a potential for significantly affecting the results of PTS analyses. The effect of including Type I warm prestress in probabilistic fracture-mechanics analyses is beneficial. The benefit is transient dependent and, in some cases, can be quite significant. 19 refs., 12 figs., 1 tab

  19. A method to determine site-specific, anisotropic fracture toughness in biological materials

    International Nuclear Information System (INIS)

    Bechtle, Sabine; Özcoban, Hüseyin; Yilmaz, Ezgi D.; Fett, Theo; Rizzi, Gabriele; Lilleodden, Erica T.; Huber, Norbert; Schreyer, Andreas; Swain, Michael V.; Schneider, Gerold A.

    2012-01-01

    Many biological materials are hierarchically structured, with highly anisotropic structures and properties on several length scales. To characterize the mechanical properties of such materials, detailed testing methods are required that allow precise and site-specific measurements on several length scales. We propose a fracture toughness measurement technique based on notched focused ion beam prepared cantilevers of lower and medium micron size scales. Using this approach, site-specific fracture toughness values in dental enamel were determined. The usefulness and challenges of the method are discussed.

  20. Effects of stress and mental toughness on burnout and depressive symptoms: A prospective study with young elite athletes.

    Science.gov (United States)

    Gerber, Markus; Best, Simon; Meerstetter, Fabienne; Walter, Marco; Ludyga, Sebastian; Brand, Serge; Bianchi, Renzo; Madigan, Daniel J; Isoard-Gautheur, Sandrine; Gustafsson, Henrik

    2018-05-18

    To examine in a sample of young elite athletes (a) the presence of clinically relevant symptoms of burnout and depression, and (b) a possible interaction of perceived stress and mental toughness in the prediction of burnout and depressive symptoms. 6-month prospective study. A representative sample of 257 young elite athletes (M=16.82years, SD=1.44, 36% females) was recruited in North-Western Switzerland. 197 athletes were followed-up across a 6-month period. Burnout was assessed with the Shirom-Melamed Burnout Measure (SMBM), and depression with the 9-item depression module of the Patient Health Questionnaire (PHQ). Values of ≥4.40 (SMBM) and >14 (PHQ-9) were considered indicative of clinically relevant burnout or depression. Stress perceptions were assessed with the Perceived Stress Scale (PSS), and mental toughness with the Mental Toughness Questionnaire (MTQ). Hierarchical regression analyses were used to test stress-buffering effects. The percentage of athletes with clinically relevant levels of burnout and depressive symptoms was 12% and 9%, respectively. Both cross-sectional and prospective analyses showed that compared to participants with low mental toughness, those with higher mental toughness scores reported significantly fewer mental health issues, when exposed to high stress. By contrast, when stress levels were low, mental toughness was unrelated to psychological health complaints. About every tenth young elite athlete reported burnout or depressive symptoms of potential clinical relevance. While high perceived stress was associated with increased psychological health complaints, mental toughness was able to off-set some of the negative consequences resulting from high stress exposure. Copyright © 2018 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  1. The effective fracture toughness of structural components obtained with the blend rule

    International Nuclear Information System (INIS)

    Eriksson, K.

    1998-01-01

    The blend rule for the effective fracture toughness of a layered material was originally derived from the special case of a through crack in a globally elastic material and later extended to accomodate non-linear behaviour. It is now derived from a general case by considering material elements of finite size and of different toughness along and around the tip of a crack. Experimental results obtained with an inhomogeneous ordinary structural steel which support the blend rule are presented. It is shown that the effective fracture toughness governs the load-bearing capacity of a cracked full-scale structure. Some further results found in the literature for the heat-affected zone material of a high-strength microalloyed quenched and tempered structural steel and computational results for a structural steel typical of a nuclear pressure vessel are shown to support the blend rule. (orig.)

  2. Interpretation of toughness tests performed on A533, grade B steel in the transition regime. Modelling and numerical analysis

    International Nuclear Information System (INIS)

    Eripret, C.

    1994-01-01

    Modelling the fracture behaviour of pressure vessel steels is of major importance for related structural integrity assessments. It is essential to understand how the micromechanisms control the transition between ductile and brittle fracture for predicting geometry effects on transition temperature. To meet this goal, a model has been developed at EDF/R and DD in the framework of local approach to fracture. Its experimental validation has been achieved by analysing toughness tests performed by AEA Technology for a pressure vessel steel in the transition regime. This large data base has evidenced the specimen thickness effects on toughness properties of the material, as well as influence of prior ductile crack growth. Predictions of the model have been compared with experiments, which shows that the transition curve K 1C = f (T) can be drawn from model predictions and compared with the RCCM or ASME design curve. Substantial safety margins have been exhibited. They are greater for thin specimens (10 mm) than for thicker specimens (230 mm). However, the transition curve in the upper transition region is still underestimated by the model (for temperatures higher than RTNDT + 50 deg C). Improvement should be made to account for important plasticity development and significant crack growth. (author). 30 figs., 10 tabs., 12 refs

  3. Application of Ultra High Performance Fiber Reinforced Concrete – The Malaysia Perspective

    OpenAIRE

    Voo - Yen Lei; Behzad Nematollahi; Abu Bakar Mohamed Said; Balamurugan A Gopal; Tet Shun Yee

    2012-01-01

    One of the most significant breakthroughs in concrete technology at the end of the 20th century was the development of ultra-high performance fiber reinforced concrete (UHPFRC) with compressive strength and flexure strength beyond 160 MPa and 30 MPa, respectively; remarkable improvement in workability; durability resembled to natural rocks; ductility and toughness comparable to steel. While over the last two decades a tremendous amount of research works have been undertaken by academics and e...

  4. The toughness of secondary cell wall and woody tissue

    OpenAIRE

    Lucas, P. W.; Tan, H. T. W.; Cheng, P. Y.

    1997-01-01

    The 'across grain' toughness of 51 woods has been determined on thin wet sections using scissors. The moisture content of sections and the varying sharpness of the scissor blades had little effect on the results. In thin sections (less than 0.6mm), toughness rose linearly with section thickness. The intercept toughness at zero thickness, estimated from regression analysis, was proportional to relative density, consistent with values reported for non-woody plant tissues. Extrapolation of the i...

  5. On the Evolutionary Stability of 'Tough' Bargaining Behavior

    DEFF Research Database (Denmark)

    Poulsen, Anders

    2003-01-01

    This paper investigates whether 'tough' bargaining behavior, which gives rise to inefficiency, can be evolutionary stable. We show that in a two-stage Nash Demand Game such behavior survives. We also study the Ultimatum Game. Here evolutionary selection wipes out all tough behavior, as long as th...

  6. The Moderating Effect of Mental Toughness: Perception of Risk and Belief in the Paranormal.

    Science.gov (United States)

    Drinkwater, Kenneth; Dagnall, Neil; Denovan, Andrew; Parker, Andrew

    2018-01-01

    This research demonstrates that higher levels of mental toughness provide cognitive-perceptual processing advantages when evaluating risk. No previous research, however, has examined mental toughness in relation to perception of risk and paranormal belief (a variable associated with distorted perception of causality and elevated levels of perceived risk). Accordingly, the present paper investigated relationships between these factors. A sample of 174 participants completed self-report measures assessing mental toughness, general perception of risk, and paranormal belief. Responses were analyzed via correlations and moderation analyses. Results revealed that mental toughness correlated negatively with perception of risk and paranormal belief, whereas paranormal belief correlated positively with perception of risk. For the moderation effects, simple slopes analyses indicated that high levels of MT and subfactors of commitment and confidence reduced the strength of association between paranormal belief and perceived risk. Therefore, MT potentially acts as a protective factor among individuals who believe in the paranormal, reducing the tendency to perceive elevated levels of risk.

  7. Research and development of basic technologies for next generation industries, 'high-performance crystalline controlled alloys'. Evaluation on final research and development (first report); Jisedai sangyo kiban gijutsu kenkyu kaihatsu. Koseino kessho seigyo gokin (saishu kenkyu kaihatsu hyoka 1)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1989-05-01

    The present research work has been performing research and development of the following alloys: (1) 'single crystalline alloy' , the entire alloy being composed of one crystal eliminating crystalline boundaries as an ultra heat resistant alloy with emphasis placed on improvement in particularly the creep properties, and 'particle dispersion strengthened alloy', in which ultrafine particles of oxides are dispersed uniformly; and (2) 'ultra heat resistant and tough alloy' targeted at high-temperature toughness by using Ni-group allowing ultra plasticity forging processing by micronizing crystal particles, as an ultra plastic and highly tough alloy having better processibility than conventional alloys, and 'light-weight highly tough alloy' aimed at achieving light weight and high toughness by using Ti-group. Achievements derived from the present research and development may be summarized as follows: in alloy development, alloys having performance of the world's highest level or equivalent have been developed; a manufacturing technology to make products with complex shapes has been established by using the alloy material manufacturing technology and the alloy materials developed therefrom, where prototype components of such shapes as turbine blades and turbine disks for jet engines were fabricated successfully; and the big fruit obtained was that a large number of technological experiences were acquired from this research and development. (NEDO)

  8. The Influence of Instrumented Striker Configuration on the Results of Dynamic Toughness Testing

    International Nuclear Information System (INIS)

    Lucon, E.

    2008-01-01

    Several studies are available on the influence of the edge radius of instrumented strikers (ASTM - 8 mm or ISO - 2 mm) on the results of both non instrumented and instrumented Charpy tests. This paper investigates the effect of using either a 2 mm or a 8 mm striker when performing dynamic toughness tests at impact loading rates on precracked Charpy specimens. Existing data from tests run in the ductile-to-brittle region (dynamic Master Curve reference temperature) and in the upper shelf regime (ductile initiation fracture toughness and crack resistance curves) have been analyzed. The results show that 2 mm strikers tend to yield lower cleavage fracture toughness in the transition region (although the effect cannot be considered statistically significant), whereas the influence of striker configuration is negligible in the upper shelf regime when data are generated using the low-blow multiple-specimen technique.

  9. The Influence of Instrumented Striker Configuration on the Results of Dynamic Toughness Testing

    Energy Technology Data Exchange (ETDEWEB)

    Lucon, E.

    2008-09-15

    Several studies are available on the influence of the edge radius of instrumented strikers (ASTM - 8 mm or ISO - 2 mm) on the results of both non instrumented and instrumented Charpy tests. This paper investigates the effect of using either a 2 mm or a 8 mm striker when performing dynamic toughness tests at impact loading rates on precracked Charpy specimens. Existing data from tests run in the ductile-to-brittle region (dynamic Master Curve reference temperature) and in the upper shelf regime (ductile initiation fracture toughness and crack resistance curves) have been analyzed. The results show that 2 mm strikers tend to yield lower cleavage fracture toughness in the transition region (although the effect cannot be considered statistically significant), whereas the influence of striker configuration is negligible in the upper shelf regime when data are generated using the low-blow multiple-specimen technique.

  10. Dynamic Toughness Testing of Pre-Cracked Charpy V-Notch Specimens. Convention ELECTRABEL - SCK-CEN

    Energy Technology Data Exchange (ETDEWEB)

    Lucon, E

    1999-04-01

    This document describes the experimental and analytical procedures which have been adopted at the laboratories of the Belgian Nuclear Research Centre SCK-CEN for performing dynamic toughness tests on pre-cracked Charpy-V specimens. Such procedures were chosen on the basis of the existing literature on the subject, with several updates in the data analysis stages which reflect more recent developments in fracture toughness testing. Qualification tests have been carried out on PCCv specimens of JRQ steel, in order to assess the reliability of the results obtained; straightforward comparisons with reference data have been performed, as well as more advanced analyses using the Master Curve approach. Aspects related to machine compliance and dynamic tup calibration have also been addressed.

  11. Dynamic Fracture Toughness of TaC/CNTs/SiC CMCs Prepared by Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Qiaoyun Xie

    2015-01-01

    Full Text Available This study focuses on the fracture toughness of TaC and carbon nanotubes (CNTs reinforced SiC ceramic matrix composites (CMCs, prepared by spark plasma sintering (SPS technique. A high densification of 98.4% was achieved under the sintering parameter of 133°C/min, 1800°C, and 90 MPa pressure. Vickers indentation was employed to measure the indentation toughness on the polished surface of ceramic samples, SEM was applied to directly observe the crack propagation after indentation, and split Hopkinson pressure bar (SHPB was developed to determine the dynamic fracture toughness within the ceramic samples subjected to an impact in a three-point bending configuration.

  12. Evaluation of fracture toughness of ductile cast iron for casks

    International Nuclear Information System (INIS)

    Hide, Koh-ichiro; Arai, Taku; Takaku, Hiroshi; Shimazaki, Katsunori; Kusanagi, Hideo

    1988-01-01

    We studied the fracture toughness and tensile properties of ductile cast iron for casks, and tried to introduce a fatigue crack into partial cask model. Main results were shown as follows. (1) Fracture toughness were in the upper shelf area above -25deg C, and were in the transition area at -40 and -70deg C. (2) Increasing the value of K I , the fracture toughness decreased. (3) Increasing the specimen thickness, fracture toughness decreased. (4) Fracture toughness of an artificial flaw (ρ=0.1 mm) was the same as that of a fatigue crack at -40deg C. (5) Tensil properties were inferior at -196 and about 400deg C because of low temperature brittleness and blue brittleness. (6) Tensile properties in the middle of cask wall were inferior. (7) It seems to be possible to introduce a fatigue crack into a full size cask. (author)

  13. Fracture toughness of ferritic alloys irradiated at FFTF

    International Nuclear Information System (INIS)

    Huang, F.H.

    1986-05-01

    Ferritic compact tension specimens loaded in the Material Open Test Assembly (MOTA) for irradiation during FFTF Cycle 4 were tested at temperatures ranging from room temperature to 428/degree/C. The electrical potential single specimen method was used to measure the fracture toughness of the specimens. Results showed that the fracture toughness of both HT-9 and 9Cr-1Mo decreases with increasing test temperature and that the toughness of HT-9 was about 30% higher than that of 9Cr-1Mo. In addition, increasing irradiation temperature resulted in an increase in tearing modulus for both alloys. 4 refs., 5 figs., 1 tab

  14. 46 CFR 57.06-5 - Production toughness testing.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Production toughness testing. 57.06-5 Section 57.06-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING WELDING AND BRAZING Production Tests § 57.06-5 Production toughness testing. (a) In addition to the test specimens required by...

  15. In tropical lowland rain forests monocots have tougher leaves than dicots, and include a new kind of tough leaf.

    Science.gov (United States)

    Dominy, Nathaniel J; Grubb, Peter J; Jackson, Robyn V; Lucas, Peter W; Metcalfe, Daniel J; Svenning, Jens-Christian; Turner, Ian M

    2008-06-01

    There has been little previous work on the toughness of the laminae of monocots in tropical lowland rain forest (TLRF) despite the potential importance of greater toughness in inhibiting herbivory by invertebrates. Of 15 monocot families with >100 species in TLRF, eight have notably high densities of fibres in the lamina so that high values for toughness are expected. In north-eastern Australia punch strength was determined with a penetrometer for both immature leaves (approx. 30 % final area on average) and fully expanded, fully toughened leaves. In Singapore and Panama, fracture toughness was determined with an automated scissors apparatus using fully toughened leaves only. In Australia punch strength was, on average, 7x greater in shade-tolerant monocots than in neighbouring dicots at the immature stage, and 3x greater at the mature stage. In Singapore, shade-tolerant monocots had, on average, 1.3x higher values for fracture toughness than neighbouring dicots. In Panama, both shade-tolerant and gap-demanding monocots were tested; they did not differ in fracture toughness. The monocots had markedly higher values than the dicots whether shade-tolerant or gap-demanding species were considered. It is predicted that monocots will be found to experience lower rates of herbivory by invertebrates than dicots. The tough monocot leaves include both stiff leaves containing relatively little water at saturation (e.g. palms), and leaves which lack stiffness, are rich in water at saturation and roll readily during dry weather or even in bright sun around midday (e.g. gingers, heliconias and marants). Monocot leaves also show that it is possible for leaves to be notably tough throughout the expansion phase of development, something never recorded for dicots. The need to broaden the botanist's mental picture of a 'tough leaf' is emphasized.

  16. Applicability of the fracture toughness master curve to irradiated reactor pressure vessel steels

    International Nuclear Information System (INIS)

    Sokolov, M.A.; McCabe, D.E.; Alexander, D.J.; Nanstad, R.K.

    1997-01-01

    -thick (25-mm)] specimen. Thus, fracture toughness of the material can be described by a fracture toughness-based reference temperature rather that by a temperature derived from a combination of drop-weight and Charpy impact tests. A statistical size correction based upon weakest-link theory is used to adjust the measured fracture toughness to that expected from a 1T specimen. Although the details of a consensus procedure is still under development, the basic procedure is widely used now to characterize elastic-plastic K Jc values in the transition range. For application to commercial nuclear RPVs, however, various uncertainties are being investigated as part of the Heavy-Section Steel Irradiation (HSSI) Program managed by the Oak Ridge National laboratory (ORNL) for the U.S. Nuclear Regulatory Commission. These include the use of relatively small specimens, e.g., precracked CVN (PCVN) and smaller size specimens, the applicability of the master curve to highly irradiated steels, and the effects of intergranular fracture. (author)

  17. Latent profiles of elite Malaysian athletes’ use of psychological skills and techniques and relations with mental toughness

    Directory of Open Access Journals (Sweden)

    Vellapandian Ponnusamy

    2018-05-01

    Full Text Available Background The majority of past work on athletes’ use of psychological skills and techniques (PSTs has adopted a variable-centered approach in which the statistical relations among study variables are averaged across a sample. However, variable-centered-analyses exclude the possibility that PSTs may be used in tandem or combined in different ways across practice and competition settings. With this empirical gap in mind, the purposes of this study were to identify the number and type of profiles of elite athletes’ use of PSTs, and examine differences between these clusters in terms of their self-reported mental toughness. Methods In this cross-sectional survey study, 285 Malaysian elite athletes (170 males, 115 females aged 15–44 years (M = 18.89, SD = 4.49 completed measures of various PSTs and mental toughness. Latent profile analysis was employed to determine the type and number of profiles that best represent athletes’ reports of their use of PSTs in practice and competition settings, and examine differences between these classes in terms of self-reported mental toughness. Results Our results revealed three profiles (low, moderate, high use in both practice and competition settings that were distinguished primarily according to quantitative differences in the absolute levels of reported use across most of the PSTs assessed in practice and competition settings, which in turn, were differentially related with mental toughness. Specifically, higher use of PSTs was associated with higher levels of mental toughness. Conclusion This study provides one of the first analyses of the different configurations of athletes’ use of PSTs that typify unique subgroups of performers. An important next step is to examine the longitudinal (in stability of such classes and therefore provide insight into the temporal dynamics of different configurations of athletes’ use of PSTs.

  18. Impact Toughness of Subzones in the Intercritical Heat-Affected Zone of Low-Carbon Bainitic Steel.

    Science.gov (United States)

    Li, Zhenshun; Zhao, Xuemin; Shan, Dongri

    2018-06-06

    The subzones of the intercritical heat-affected zone (IC HAZ) of low-carbon bainitic steel were simulated by using a Gleeble-3500 simulator to study the impact toughness. The results showed that the IC HAZ is not entirely brittle and can be further divided into three subzones according to the impact toughness or peak welding temperature; the invariant subzone heated between the critical transformation start temperature ( A c1 ) and 770 °C exhibited unchanged high impact toughness. Furthermore, an extremely low impact toughness was found in the embrittlement subzone, heated between 770 and 830 °C, and the reduction subzone heated between 830 °C and the critical transformation finish temperature ( A c3 ) exhibited toughness below that of the original metal. The size of the blocky martensite-austenite (M-A) constituents was found to have a remarkable level of influence on the impact toughness when heated below 830 °C. Additionally, it was found that, once the constituent size exceeds a critical value of 3.0 µm at a peak temperature of 770 °C, the IC HAZ becomes brittle regardless of lath or twinned martensite constitution in the M-A constituent. Essentially, embrittlement was observed to occur when the resolved length of initial cracks (in the direction of the overall fracture) formed as a result of the debonding of M-A constituents exceeding the critical Griffith size. Furthermore, when the heating temperature exceeded 830 °C, the M-A constituents formed a slender shape, and the impact toughness increased as the area fraction of the slender M-A constituents decreased.

  19. Evaluating the fracture toughness and flexural strength of pressable dental ceramics: an in vitro study.

    Science.gov (United States)

    Gurram, Ravi; Krishna, C H Vamsi; Reddy, K Mahendranadh; Reddy, G V K Mohan; Shastry, Y Mahadev

    2014-12-01

    The study was undertaken to evaluate the biaxial flexural strength, biaxial flexural strength after etching with 9 % HF acid and fracture toughness of three commonly used pressable all ceramic core materials. Ninety glass ceramic specimens were fabricated from three commercially available leucite based core ceramic material (1) Esthetic Empress, (2) Cergo, and (3) Performance Plus. Thirty discs of each material were divided into three groups of 10 discs each. Biaxial flexural strength (30 discs,) Biaxial flexural strength for samples treated with 9 % HF acid (30 discs) and fracture toughness (30 discs) were evaluated. Core material Performance Plus had the lowest biaxial strength of 124.89 MPa, Cergo had strength of 152.22 MPa and the highest value of 163.95 was reported for Esthetic Empress. For samples treated 9 % HF, Performance Plus had the lowest biaxial strength of 98.37 MPa, Cergo had strength of 117.42 MPa and the highest value of 143.74 was reported for Esthetic Empress. Core material Performance Plus had the lowest fracture toughness of 1.063 MPa, Cergo had strength of 1.112 MPa and the highest value of 1.225 was reported for Esthetic Empress. The results shows that Esthetic Empress had better mechanical properties compared to Cergo had Performance Plus in relation to the parameters tested.

  20. An Effective Modal Approach to the Dynamic Evaluation of Fracture Toughness of Quasi-Brittle Materials

    Science.gov (United States)

    Ferreira, L. E. T.; Vareda, L. V.; Hanai, J. B.; Sousa, J. L. A. O.; Silva, A. I.

    2017-05-01

    A modal dynamic analysis is used as the tool to evaluate the fracture toughness of concrete from the results of notched-through beam tests. The dimensionless functions describing the relation between the frequencies and specimen geometry used for identifying the variation in the natural frequency as a function of crack depth is first determined for a 150 × 150 × 500-mm notched-through specimen. The frequency decrease resulting from the propagating crack is modeled through a modal/fracture mechanics approach, leading to determination of an effective crack length. This length, obtained numerically, is used to evaluate the fracture toughness of concrete, the critical crack mouth opening displacements, and the brittleness index proposed. The methodology is applied to tests performed on high-strength concrete specimens. The frequency response for each specimen is evaluated before and after each crack propagation step. The methodology is then validated by comparison with results from the application of other methodologies described in the literature and suggested by RILEM.

  1. Rock Fracture Toughness Study Under Mixed Mode I/III Loading

    Science.gov (United States)

    Aliha, M. R. M.; Bahmani, A.

    2017-07-01

    Fracture growth in underground rock structures occurs under complex stress states, which typically include the in- and out-of-plane sliding deformation of jointed rock masses before catastrophic failure. However, the lack of a comprehensive theoretical and experimental fracture toughness study for rocks under contributions of out-of plane deformations (i.e. mode III) is one of the shortcomings of this field. Therefore, in this research the mixed mode I/III fracture toughness of a typical rock material is investigated experimentally by means of a novel cracked disc specimen subjected to bend loading. It was shown that the specimen can provide full combinations of modes I and III and consequently a complete set of mixed mode I/III fracture toughness data were determined for the tested marble rock. By moving from pure mode I towards pure mode III, fracture load was increased; however, the corresponding fracture toughness value became smaller. The obtained experimental fracture toughness results were finally predicted using theoretical and empirical fracture models.

  2. Fracture toughness of silicon nitride thin films of different thicknesses as measured by bulge tests

    International Nuclear Information System (INIS)

    Merle, B.; Goeken, M.

    2011-01-01

    A bulge test setup was used to determine the fracture toughness of amorphous low-pressure chemical vapor deposited (LPCVD) silicon nitride films with various thicknesses in the range 40-108 nm. A crack-like slit was milled in the center of each free-standing film with a focused ion beam, and the membrane was deformed in the bulge test until failure occurred. The fracture toughness K IC was calculated from the pre-crack length and the stress at failure. It is shown that the membrane is in a transition state between pure plane-stress and plane-strain which, however, had a negligible influence on the measurement of the fracture toughness, because of the high brittleness of silicon nitride and its low Young's modulus over yield strength ratio. The fracture toughness K IC was found to be constant at 6.3 ± 0.4 MPa m 1/2 over the whole thickness range studied, which compares well with bulk values. This means that the fracture toughness, like the Young's modulus, is a size-independent quantity for LPCVD silicon nitride. This presumably holds true for all amorphous brittle ceramic materials.

  3. Effects of thermal annealing and reirradiation on toughness of reactor pressure vessel steels

    International Nuclear Information System (INIS)

    Nanstad, R.K.; Iskander, S.K.; Sokolov, M.A.

    1996-01-01

    One of the options to mitigate the effects of irradiation on reactor pressure vessels (RPV) is to thermally anneal them to restore the toughness properties that have been degraded by neutron irradiation. This paper summarizes recent experimental results from work performed at the Oak Ridge National Laboratory (ORNL) to study the annealing response, or open-quotes recovery,close quotes of several irradiated RPV steels; it also includes recent results from both ORNL and the Russian Research Center-Kurchatov Institute (RRC-KI) on a cooperative program of irradiation, annealing and reirradiation of both U.S. and Russian RPV steels. The cooperative program was conducted under the auspices of Working Group 3, U.S./Russia Joint Coordinating Committee for Civilian Nuclear Reactor Safety (JCCCNRS). The materials investigated are an RPV plate and various submerged-arc welds, with tensile, Charpy impact toughness, and fracture toughness results variously determined. Experimental results are compared with applicable prediction guidelines, while observed differences in annealing responses and reirradiation rates are discussed

  4. Effects of thermal annealing and reirradiation on toughness of reactor pressure vessel steels

    International Nuclear Information System (INIS)

    Nanstad, R.K.; Iskander, S.K.; Sokolov, M.A.

    1997-01-01

    One of the options to mitigate the effects of irradiation on reactor pressure vessels (RPV) is to thermally anneal them to restore the toughness properties that have been degraded by neutron irradiation. This paper summarizes recent experimental results from work performed at the Oak Ridge National Laboratory (ORNL) to study the annealing response, or open-quotes recovery,close quotes of several irradiated RPV steels; it also includes recent results from both ORNL and the Russian Research Center-Kurchatov Institute (RRC-KI) on a cooperative program of irradiation, annealing and reirradiation of both U.S. and Russian RPV steels. The cooperative program was conducted under the auspices of Working Group 3, U.S./Russia Joint Coordinating Committee for Civilian Nuclear Reactor Safety (JCCCNRS). The materials investigated are an RPV plate and various submerged-arc welds, with tensile, Charpy impact toughness, and fracture toughness results variously determined. Experimental results are compared with applicable prediction guidelines, while observed differences in annealing responses and reirradiation rates are discussed

  5. Effect of Temperature on the Fracture Toughness of Hot Isostatically Pressed 304L Stainless Steel

    OpenAIRE

    Cooper, Adam J.; Sherry, Andrew

    2018-01-01

    Herein, we have performed J-Resistance multi-specimen fracture toughness testing of hot isostatically pressed (HIP’d) and forged 304L austenitic stainless steel, tested at elevated (300 °C) and cryogenic (− 140 °C) temperatures. The work highlights that although both materials fail in a pure ductile fashion, stainless steel manufactured by HIP displays a marked reduction in fracture toughness, defined using J0.2BL, when compared to equivalently graded forged 304L, which is relatively constant...

  6. TOUGH2 User's Guide Version 2

    Energy Technology Data Exchange (ETDEWEB)

    Pruess, K.; Oldenburg, C.M.; Moridis, G.J.

    1999-11-01

    TOUGH2 is a numerical simulator for nonisothermal flows of multicomponent, multiphase fluids in one, two, and three-dimensional porous and fractured media. The chief applications for which TOUGH2 is designed are in geothermal reservoir engineering, nuclear waste disposal, environmental assessment and remediation, and unsaturated and saturated zone hydrology. TOUGH2 was first released to the public in 1991; the 1991 code was updated in 1994 when a set of preconditioned conjugate gradient solvers was added to allow a more efficient solution of large problems. The current Version 2.0 features several new fluid property modules and offers enhanced process modeling capabilities, such as coupled reservoir-wellbore flow, precipitation and dissolution effects, and multiphase diffusion. Numerous improvements in previously released modules have been made and new user features have been added, such as enhanced linear equation solvers, and writing of graphics files. The T2VOC module for three-phase flows of water, air and a volatile organic chemical (VOC), and the T2DM module for hydrodynamic dispersion in 2-D flow systems have been integrated into the overall structure of the code and are included in the Version 2.0 package. Data inputs are upwardly compatible with the previous version. Coding changes were generally kept to a minimum, and were only made as needed to achieve the additional functionalities desired. TOUGH2 is written in standard FORTRAN77 and can be run on any platform, such as workstations, PCs, Macintosh, mainframe and supercomputers, for which appropriate FORTRAN compilers are available. This report is a self-contained guide to application of TOUGH2 to subsurface flow problems. It gives a technical description of the TOUGH2 code, including a discussion of the physical processes modeled, and the mathematical and numerical methods used. Illustrative sample problems are presented along with detailed instructions for preparing input data.

  7. The loss of activating transcription factor 4 (ATF4) reduces bone toughness and fracture toughness.

    Science.gov (United States)

    Makowski, Alexander J; Uppuganti, Sasidhar; Wadeer, Sandra A; Whitehead, Jack M; Rowland, Barbara J; Granke, Mathilde; Mahadevan-Jansen, Anita; Yang, Xiangli; Nyman, Jeffry S

    2014-05-01

    Even though age-related changes to bone tissue affecting fracture risk are well characterized, only a few matrix-related factors have been identified as important to maintaining fracture resistance. As a gene critical to osteoblast differentiation, activating transcription factor 4 (ATF4) is possibly one of these important factors. To test the hypothesis that the loss of ATF4 affects the fracture resistance of bone beyond bone mass and structure, we harvested bones from Atf4+/+ and Atf4-/- littermates at 8 and 20 weeks of age (n≥9 per group) for bone assessment across several length scales. From whole bone mechanical tests in bending, femurs from Atf4-/- mice were found to be brittle with reduced toughness and fracture toughness compared to femurs from Atf4+/+ mice. However, there were no differences in material strength and in tissue hardness, as determined by nanoindentation, between the genotypes, irrespective of age. Tissue mineral density of the cortex at the point of loading as determined by micro-computed tomography was also not significantly different. However, by analyzing local composition by Raman Spectroscopy (RS), bone tissue of Atf4-/- mice was found to have higher mineral to collagen ratio compared to wild-type tissue, primarily at 20 weeks of age. From RS analysis of intact femurs at 2 orthogonal orientations relative to the polarization axis of the laser, we also found that the organizational-sensitive peak ratio, ν1Phosphate per Amide I, changed to a greater extent upon bone rotation for Atf4-deficient tissue, implying bone matrix organization may contribute to the brittleness phenotype. Target genes of ATF4 activity are not only important to osteoblast differentiation but also in maintaining bone toughness and fracture toughness. Published by Elsevier Inc.

  8. The Loss of Activating Transcription Factor 4 (ATF4) Reduces Bone Toughness and Fracture Toughness

    Science.gov (United States)

    Makowski, Alexander J.; Uppuganti, Sasidhar; Waader, Sandra A.; Whitehead, Jack M.; Rowland, Barbara J.; Granke, Mathilde; Mahadevan-Jansen, Anita; Yang, Xiangli; Nyman, Jeffry S.

    2014-01-01

    Even though age-related changes to bone tissue affecting fracture risk are well characterized, only a few matrix-related factors have been identified as important to maintaining fracture resistance. As a gene critical to osteoblast differentiation, activating transcription factor 4 (ATF4) is possibly one of the seimportant factors. To test the hypothesis that the loss of ATF4 affects the fracture resistance of bone beyond bone mass and structure, we harvested bones from Atf4+/+ and Atf4−/− littermates at 8 and 20 weeks of age (n≥9 per group) for bone assessment across several length scales. From whole bone mechanical tests in bending, femurs from Atf4−/− mice were found to be brittle with reduced toughness and fracture toughness compared to femurs from Atf4+/+ mice. However, there were no differences in material strength and in tissue hardness, as determined by nanoindentation, between the genotypes, irrespective age. Tissue mineral density of the cortex at the point of loading as determined by micro-computed tomography was also not significantly different. However, by analyzing local composition by Raman Spectroscopy (RS), bone tissue of Atf4−/− mice was found to have higher mineral to collagen ratio compared to wild-type tissue, primarily at 20 weeks of age. From RS analysis of intact femurs at 2 orthogonal orientations relative to the polarization axis of the laser, we also found that the organizational-sensitive peak ratio, ν1 Phosphate per Amide I, changed to a greater extent upon bone rotation for Atf4-deficient tissue, implying bone matrix organization may contribute to the brittleness phenotype. Target genes of ATF4 activity are not only important to osteoblast differentiation but also maintaining bone toughness and fracture toughness. PMID:24509412

  9. TOUGH2Biot - A simulator for coupled thermal-hydrodynamic-mechanical processes in subsurface flow systems: Application to CO2 geological storage and geothermal development

    Science.gov (United States)

    Lei, Hongwu; Xu, Tianfu; Jin, Guangrong

    2015-04-01

    Coupled thermal-hydrodynamic-mechanical processes have become increasingly important in studying the issues affecting subsurface flow systems, such as CO2 sequestration in deep saline aquifers and geothermal development. In this study, a mechanical module based on the extended Biot consolidation model was developed and incorporated into the well-established thermal-hydrodynamic simulator TOUGH2, resulting in an integrated numerical THM simulation program TOUGH2Biot. A finite element method was employed to discretize space for rock mechanical calculation and the Mohr-Coulomb failure criterion was used to determine if the rock undergoes shear-slip failure. Mechanics is partly coupled with the thermal-hydrodynamic processes and gives feedback to flow through stress-dependent porosity and permeability. TOUGH2Biot was verified against analytical solutions for the 1D Terzaghi consolidation and cooling-induced subsidence. TOUGH2Biot was applied to evaluate the thermal, hydrodynamic, and mechanical responses of CO2 geological sequestration at the Ordos CCS Demonstration Project, China and geothermal exploitation at the Geysers geothermal field, California. The results demonstrate that TOUGH2Biot is capable of analyzing change in pressure and temperature, displacement, stress, and potential shear-slip failure caused by large scale underground man-made activity in subsurface flow systems. TOUGH2Biot can also be easily extended for complex coupled process problems in fractured media and be conveniently updated to parallel versions on different platforms to take advantage of high-performance computing.

  10. 2016 Accomplishments. Tritium aging studies on stainless steel. Forging process effects on the fracture toughness properties of tritium-precharged stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Morgan, Michael J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2017-01-01

    Forged austenitic stainless steels are used as the materials of construction for pressure vessels designed to contain tritium at high pressure. These steels are highly resistant to tritium-assisted fracture but their resistance can depend on the details of the forging microstructure. During FY16, the effects of forging strain rate and deformation temperature on the fracture toughness properties of tritium-exposed-and-aged Type 304L stainless steel were studied. Forgings were produced from a single heat of steel using four types of production forging equipment – hydraulic press, mechanical press, screw press, and high-energy-rate forging (HERF). Each machine imparted a different nominal strain rate during the deformation. The objective of the study was to characterize the J-Integral fracture toughness properties as a function of the industrial strain rate and temperature. The second objective was to measure the effects of tritium and decay helium on toughness. Tritium and decay helium effects were measured by thermally precharging the as-forged specimens with tritium gas at 34.5 MPa and 350°C and aging for up to five years at -80°C to build-in decay helium prior to testing. The results of this study show that the fracture toughness properties of the as-forged steels vary with forging strain rate and forging temperature. The effect is largely due to yield strength as the higher-strength forgings had the lower toughness values. For non-charged specimens, fracture toughness properties were improved by forging at 871°C versus 816°C and Screw-Press forgings tended to have lower fracture toughness values than the other forgings. Tritium exposures reduced the fracture toughness values remarkably to fracture toughness values averaging 10-20% of as-forged values. However, forging strain rate and temperature had little or no effect on the fracture toughness after tritium precharging and aging. The result was confirmed by fractography which indicated that fracture modes

  11. Correlations between fracture toughness and microstructure in 4140 steel. MRL E-113

    Energy Technology Data Exchange (ETDEWEB)

    Odegaard, T K

    1979-06-01

    Correlations between the microstructure of an ultra-high strength steel and material resistance to fracture, as measured by blunt notch Charpy impact tests and sharp crack K/sub IC/ tests, were investigated for a standard 870/sup 0/C/oil and an experimental 1175/sup 0/C/oil austenitizing treatment. The increase in sharp crack toughness with higher temperature austenitizing treatments, for the as-quenched and 200/sup 0/C/oil temper conditions, was rationalized by a fracture criterion based on the notion that for fracture to occur, a critical strain, epsilon/sub f/, must be achieved over some critical distance, delta. The lath colonies were identified as the fracture controlling microstructural unit, and hence, their size was considered to be the critical distance, delta. Toughness in the 300/sup 0/C/l hour and 400/sup 0/C/l hour temper conditions, for which the mechanical data indicated an embrittlement, was clearly controlled by the cementite morphology in conjunction with the prior austenite grain size. Attempts to rationalize toughness in these temper conditions, using a stress-controlled fracture criterion, were unsuccessful and led to physically unreasonable results. In the 500/sup 0/C/l hour temper condition, stable crack growth and periodic ridge patterns were observed. Fracture toughness differences between the 870/sup 0/C and 1175/sup 0/C austenitizing treatments were qualitatively rationalized by the nature of the respective fracture morphologies. Good correspondence between J/sub IC/ and the so-called tearing modulus, T, as indicators of sharp crack fracture toughness, was observed.

  12. Correlations between fracture toughness and microstructure in 4140 steel. MRL E-113

    International Nuclear Information System (INIS)

    Odegaard, T.K.

    1979-06-01

    Correlations between the microstructure of an ultra-high strength steel and material resistance to fracture, as measured by blunt notch Charpy impact tests and sharp crack K/sub IC/ tests, were investigated for a standard 870 0 C/oil and an experimental 1175 0 C/oil austenitizing treatment. The increase in sharp crack toughness with higher temperature austenitizing treatments, for the as-quenched and 200 0 C/oil temper conditions, was rationalized by a fracture criterion based on the notion that for fracture to occur, a critical strain, epsilon/sub f/, must be achieved over some critical distance, delta. The lath colonies were identified as the fracture controlling microstructural unit, and hence, their size was considered to be the critical distance, delta. Toughness in the 300 0 C/l hour and 400 0 C/l hour temper conditions, for which the mechanical data indicated an embrittlement, was clearly controlled by the cementite morphology in conjunction with the prior austenite grain size. Attempts to rationalize toughness in these temper conditions, using a stress-controlled fracture criterion, were unsuccessful and led to physically unreasonable results. In the 500 0 C/l hour temper condition, stable crack growth and periodic ridge patterns were observed. Fracture toughness differences between the 870 0 C and 1175 0 C austenitizing treatments were qualitatively rationalized by the nature of the respective fracture morphologies. Good correspondence between J/sub IC/ and the so-called tearing modulus, T, as indicators of sharp crack fracture toughness, was observed

  13. Application of fracture toughness scaling models to the ductile-to- brittle transition

    International Nuclear Information System (INIS)

    Link, R.E.; Joyce, J.A.

    1996-01-01

    An experimental investigation of fracture toughness in the ductile-brittle transition range was conducted. A large number of ASTM A533, Grade B steel, bend and tension specimens with varying crack lengths were tested throughout the transition region. Cleavage fracture toughness scaling models were utilized to correct the data for the loss of constraint in short crack specimens and tension geometries. The toughness scaling models were effective in reducing the scatter in the data, but tended to over-correct the results for the short crack bend specimens. A proposed ASTM Test Practice for Fracture Toughness in the Transition Range, which employs a master curve concept, was applied to the results. The proposed master curve over predicted the fracture toughness in the mid-transition and a modified master curve was developed that more accurately modeled the transition behavior of the material. Finally, the modified master curve and the fracture toughness scaling models were combined to predict the as-measured fracture toughness of the short crack bend and the tension specimens. It was shown that when the scaling models over correct the data for loss of constraint, they can also lead to non-conservative estimates of the increase in toughness for low constraint geometries

  14. Dynamic fracture toughness and evaluation of fracture in a ferritic nodular cast iron for casks

    International Nuclear Information System (INIS)

    Yasunaka, T.; Nakano, K.

    1993-01-01

    The effect of loading rate and temperature on fracture toughness of a ferritic nodular cast iron obtained from a thick-walled cylindrical casting has been investigated. Based upon this result, the cast iron is evaluated as a material for casks. (1) In the ductile fracture region, fracture toughness increases with increases in loading rate. (2) Ductile-brittle transition temperature is linearly related to the logarithm of stress intensity rate. (3) In the ductile fracture region, converted plain strain fracture toughness divided by yield stress can be adopted as a material constant which is independent of loading rate and temperature. From the result of a static fracture toughness test, the evaluation of fracture in high loading rate can be made. (4) In the ductile fracture region of the material investigated, the maximum allowable flaw depth exceeded the minimum detectable flaw size by a nondestructive inspection. Ferritic nodular cast iron can be used as a material for casks in the ductile fracture region at least. (J.P.N.)

  15. Composite Strain Hardening Properties of High Performance Hybrid Fibre Reinforced Concrete

    Directory of Open Access Journals (Sweden)

    Vikram Jothi Jayakumar

    2014-01-01

    Full Text Available Hybrid fibres addition in concrete proved to be a promising method to improve the composite mechanical properties of the cementitious system. Fibre combinations involving different fibre lengths and moduli were added in high strength slag based concrete to evaluate the strain hardening properties. Influence of hybrid fibres consisting of steel and polypropylene fibres added in slag based cementitious system (50% CRL was explored. Effects of hybrid fibre addition at optimum volume fraction of 2% of steel fibres and 0.5% of PP fibres (long and short steel fibre combinations were observed in improving the postcrack strength properties of concrete. Test results also indicated that the hybrid steel fibre additions in slag based concrete consisting of short steel and polypropylene (PP fibres exhibited a the highest compressive strength of 48.56 MPa. Comparative analysis on the performance of monofibre concrete consisting of steel and PP fibres had shown lower residual strength compared to hybrid fibre combinations. Hybrid fibres consisting of long steel-PP fibres potentially improved the absolute and residual toughness properties of concrete composite up to a maximum of 94.38% compared to monofibre concrete. In addition, the relative performance levels of different hybrid fibres in improving the matrix strain hardening, postcrack toughness, and residual strength capacity of slag based concretes were evaluated systematically.

  16. Fracture toughness evaluation of select advanced replacement alloys for LWR core internals

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Lizhen [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Chen, Xiang [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-08-01

    Life extension of the existing nuclear reactors imposes irradiation of high fluences to structural materials, resulting in significant challenges to the traditional reactor materials such as type 304 and 316 stainless steels. Advanced alloys with superior radiation resistance will increase safety margins, design flexibility, and economics for not only the life extension of the existing fleet but also new builds with advanced reactor designs. The Electric Power Research Institute (EPRI) teamed up with Department of Energy (DOE) to initiate the Advanced Radiation Resistant Materials (ARRM) program, aiming to develop and test degradation resistant alloys from current commercial alloy specifications by 2021 to a new advanced alloy with superior degradation resistance in light water reactor (LWR)-relevant environments by 2024. Fracture toughness is one of the key engineering properties required for core internal materials. Together with other properties, which are being examined such as high-temperature steam oxidation resistance, radiation hardening, and irradiation-assisted stress corrosion cracking resistance, the alloys will be down-selected for neutron irradiation study and comprehensive post-irradiation examinations. According to the candidate alloys selected under the ARRM program, ductile fracture toughness of eight alloys was evaluated at room temperature and the LWR-relevant temperatures. The tested alloys include two ferritic alloys (Grade 92 and an oxide-dispersion-strengthened alloy 14YWT), two austenitic stainless steels (316L and 310), four Ni-base superalloys (718A, 725, 690, and X750). Alloy 316L and X750 are included as reference alloys for low- and high-strength alloys, respectively. Compact tension specimens in 0.25T and 0.2T were machined from the alloys in the T-L and R-L orientations according to the product forms of the alloys. This report summarizes the final results of the specimens tested and analyzed per ASTM Standard E1820. Unlike the

  17. Effect of Temperature on the Fracture Toughness of Hot Isostatically Pressed 304L Stainless Steel

    Science.gov (United States)

    Cooper, A. J.; Brayshaw, W. J.; Sherry, A. H.

    2018-03-01

    Herein, we have performed J- Resistance multi-specimen fracture toughness testing of hot isostatically pressed (HIP'd) and forged 304L austenitic stainless steel, tested at elevated (300 °C) and cryogenic (- 140 °C) temperatures. The work highlights that although both materials fail in a pure ductile fashion, stainless steel manufactured by HIP displays a marked reduction in fracture toughness, defined using J 0.2BL, when compared to equivalently graded forged 304L, which is relatively constant across the tested temperature range.

  18. Aqueous stress-corrosion cracking of high-toughness D6AC steel

    Science.gov (United States)

    Gilbreath, W. P.; Adamson, M. J.

    1976-01-01

    The crack growth behavior of D6AC steel as a function of stress intensity, stress and corrosion history, and test technique, under sustained load in filtered natural seawater, 3.3 per cent sodium chloride solution, and distilled water, was investigated. Reported investigations of D6AC were considered in terms of the present study with emphasis on thermal treatment, specimen configuration, fracture toughness, crack-growth rates, initiation period, and threshold. Both threshold and growth kinetics were found to be relatively insensitive to these test parameters. The apparent incubation period was dependent on technique, both detection sensitivity and precracking stress intensity level.

  19. To investigate the effect of heat treatment on fracture toughness of welded joints

    International Nuclear Information System (INIS)

    Hameed, A.; Pasha, R.A.; Shah, M.

    2013-01-01

    Annealing as a post weld heat treatment (PWHT), increases toughness in the welding joints of medium carbon steel in the same way as it increases toughness of the non-welded medium carbon steel. Measurement of increase in toughness through PWHT is focus of the present research work. Welded samples of commercially available steel AISI -1035 have been used for the proposed evaluation. The samples welded by two different techniques namely oxyacetylene gas welding and manual metal arc welding, passed through annealing process along with non-welded samples for comparison of increase in toughness. Toughness measured by impact tests revealed the improvement, which in the order of increasing effects is in gas welded, electric welded and non-welded samples. The aim of the present research was to measure the improvement in fracture toughness through post weld heat treatment (annealing). It has been shown that toughness increases as the structural flaws decrease. (author)

  20. Impact Toughness of Subzones in the Intercritical Heat-Affected Zone of Low-Carbon Bainitic Steel

    Directory of Open Access Journals (Sweden)

    Zhenshun Li

    2018-06-01

    Full Text Available The subzones of the intercritical heat-affected zone (IC HAZ of low-carbon bainitic steel were simulated by using a Gleeble-3500 simulator to study the impact toughness. The results showed that the IC HAZ is not entirely brittle and can be further divided into three subzones according to the impact toughness or peak welding temperature; the invariant subzone heated between the critical transformation start temperature (Ac1 and 770 °C exhibited unchanged high impact toughness. Furthermore, an extremely low impact toughness was found in the embrittlement subzone, heated between 770 and 830 °C, and the reduction subzone heated between 830 °C and the critical transformation finish temperature (Ac3 exhibited toughness below that of the original metal. The size of the blocky martensite-austenite (M-A constituents was found to have a remarkable level of influence on the impact toughness when heated below 830 °C. Additionally, it was found that, once the constituent size exceeds a critical value of 3.0 µm at a peak temperature of 770 °C, the IC HAZ becomes brittle regardless of lath or twinned martensite constitution in the M-A constituent. Essentially, embrittlement was observed to occur when the resolved length of initial cracks (in the direction of the overall fracture formed as a result of the debonding of M-A constituents exceeding the critical Griffith size. Furthermore, when the heating temperature exceeded 830 °C, the M-A constituents formed a slender shape, and the impact toughness increased as the area fraction of the slender M-A constituents decreased.

  1. Summary of pre and post-processors for V-TOUGH

    International Nuclear Information System (INIS)

    Daveler, S.

    1995-08-01

    This report summaries the preprocessor utility, LMESH and the postprocessor utility, EXTOOL. These utilities support the input file generation and postprocessing analysis for V-TOUGH. LMESH is a mesh generator for V-TOUGH and generates a rectangular or cylindrical mesh in two dimensions. The format for the LMESH summary is a discussion of input options, followed by a sample problem and output from the sample problem. EXTOOL is an analysis tool that extracts, manipulates and plots V-TOUGH output. The format for the EXTOOL summary is a discussion of the development of EXTOOL and an overview of the programs capabilities

  2. Fracture toughness of intermetallics using a micro-mechanical probe

    International Nuclear Information System (INIS)

    Gerberich, W.W.; Venkataraman, S.K.; Hoehn, J.W.; Marsh, P.G.

    1993-01-01

    A novel technique for determining the fracture toughness of brittle intermetallics is presented, wherein very small samples are used and multiple tests are easily conducted on a flat polished surface. The fracture toughness of single crystal NiAl and polycrystalline Al 3 Sc are evaluated with this continuous microscratch technique at scratch rates ranging from 0.5 to greater than 100 μm s - . For comparison, small compact tension samples of (100) NiAl are evaluated at applied stress intensity rates ranging from 1.5 to 5,400 MPa-m 1/2 s -1 . Good comparison of microscratch toughness to compact tension K Ic values are obtained in this study for (001) NiAl, 10.6 vs. 10.0 MPa-m 1/2 , from the literature for (001) , 13.5 vs. 12.2 MPa-m 1/2 , and from the literature for polycrystalline Al 3 Sc, 3.5 vs. 3.1 MPa-m 1/2 . Also, the fracture toughness of both NiAl and Al 3 Sc are found to be strongly dependent on strain rate at room temperature with toughness dropping by an order of magnitude over a decade increase in rate. Possible reasons and implications to improving low temperature brittleness are discussed

  3. Fracture toughness and strength change of neutron-irradiated ceramic materials

    International Nuclear Information System (INIS)

    Dienst, W.; Zimmermann, H.

    1994-01-01

    In order to analyse the results of bending strength measurements on neutron-irradiated samples of Al 2 O 3 , AlN and SiC, fracture toughness measurements were additionally conducted. The neutron fluences concerned were mostly in the range of 0.6 to 3.2x10 26 n/m 2 at irradiation temperatures of 400 to 550 C. A fracture toughness decrease was generally observed for polycrystalline materials which, however, was considerably smaller than the reduction of the fracture strength. Exceptional increase of the fracture toughness seems typical for the effect of rather coarse irradiation defects. The irradiation-induced change of the fracture toughness of single crystal Al 2 O 3 appeared dependent on the crystallographic orientation; both reduced and increased fracture toughness after irradiation was observed. Recent results of neutron irradiation to about 2x10 25 n/m 2 at 100 C showed, that the strength decrease of various Al 2 O 3 grades sets in at (3-5)x10 24 n/m 2 and seems to be little dependent on the irradiation temperature. ((orig.))

  4. New unified fracture toughness estimation scheme for structural integrity assessment

    Energy Technology Data Exchange (ETDEWEB)

    Wallin, K; Nevasmaa, P [VTT, Espoo (Finland); Bannister, A [Research and Development, British Steel plc., Swinden Technology Centre Rotherham (United Kingdom)

    1999-12-31

    At present, treatment of fracture toughness data varies depending on the type of data (K{sub IC}, J, CTOD) that are available for fracture mechanics analysis. This complicates structural integrity assessment and makes it difficult to apply any single, unified procedure. Within the Brite-Euram project `SINTAP` a fracture toughness estimation scheme has been developed for the unified treatment of data for use in structural integrity assessment. As a procedure, it can be applied to Charpy data, as well as to fracture toughness data, and is suitable for the treatment of data at both single and different temperatures. The data sets may contain results from both homogeneous and inhomogeneous material, making the procedure applicable also to welded joints. The procedure allows fracture toughness assessment with quantified probability and confidence levels. Irrespective of the type of the original data, one material-specific K{sub mat} value representing a conservative estimate of the mean fracture toughness is obtained (with its probability distribution). This information can then be applied to structural integrity assessment. (orig.) 4 refs.

  5. New unified fracture toughness estimation scheme for structural integrity assessment

    Energy Technology Data Exchange (ETDEWEB)

    Wallin, K.; Nevasmaa, P. [VTT, Espoo (Finland); Bannister, A. [Research and Development, British Steel plc., Swinden Technology Centre Rotherham (United Kingdom)

    1998-12-31

    At present, treatment of fracture toughness data varies depending on the type of data (K{sub IC}, J, CTOD) that are available for fracture mechanics analysis. This complicates structural integrity assessment and makes it difficult to apply any single, unified procedure. Within the Brite-Euram project `SINTAP` a fracture toughness estimation scheme has been developed for the unified treatment of data for use in structural integrity assessment. As a procedure, it can be applied to Charpy data, as well as to fracture toughness data, and is suitable for the treatment of data at both single and different temperatures. The data sets may contain results from both homogeneous and inhomogeneous material, making the procedure applicable also to welded joints. The procedure allows fracture toughness assessment with quantified probability and confidence levels. Irrespective of the type of the original data, one material-specific K{sub mat} value representing a conservative estimate of the mean fracture toughness is obtained (with its probability distribution). This information can then be applied to structural integrity assessment. (orig.) 4 refs.

  6. Fracture toughness testing of pipeline girth welds

    Energy Technology Data Exchange (ETDEWEB)

    Shen, G.; Gianetto, J.A.; Bouchard, R.; Bowker, J.T.; Tyson, W.R.

    2005-06-01

    This paper reviewed the fracture toughness test standards for pipeline girth welds outlined in CSA Z662-03, Annex K as well as the referenced testing standards BS 7448 and ASTM Standard E 1290. The requirements outlined in API 1104, appendix A were also reviewed given its application throughout the world. Crack tip opening displacement (CTOD) tests were conducted on a manual shielded-metal-arc weld (SMAW) that was prepared in a high strength X80 pipeline steel. Another girth weld test consisted of a mechanized gas metal arc weld (GMAW), but only the results for the SMAW were presented in this paper. Two tensile specimens were machined parallel to the pipe axis from the base metal of the X80 pipe used in preparing the pipeline girth welds. The tensile specimens from the pipe base metal and weld metal were tested at 20 degrees C. The yield strength at the CTOD test temperature was estimated by using the yield strength-temperature relationship given in BS 7448. The experimental results obtained by applying the two testing standards were compared. The intent was to identify the differences between these two standards and their influence on test results. The authors discussed critical issues for the fracture toughness tests, such as weld position and notch orientation, circumferential sampling location, residual stress and its modification, crack length measurement and the equations used to evaluate CTOD. The variation of strength and toughness with clock position around the circumference of the girth welds was also discussed. It was concluded that for a high-strength material, local compression may be needed to create a uniform fatigue crack front. For deep-cracked specimens, the maximum allowable difference of the measured fatigue crack length varies significantly between ASTM E 1290-02 and BS 7448 by a factor of about 1 to 3 for ASTM E 1290 and 3 to 15 for BS 7448. The CTOD calculated according to ASTM E 1290-02 and according to BS 7448 can also differ substantially

  7. Multiparameter structural optimization of single-walled carbon nanotube composites: toward record strength, stiffness, and toughness.

    Science.gov (United States)

    Shim, Bong Sup; Zhu, Jian; Jan, Edward; Critchley, Kevin; Ho, Szushen; Podsiadlo, Paul; Sun, Kai; Kotov, Nicholas A

    2009-07-28

    Efficient coupling of mechanical properties of SWNTs with the matrix leading to the transfer of unique mechanical properties of SWNTs to the macroscopic composites is a tremendous challenge of today's materials science. The typical mechanical properties of known SWNT composites, such as strength, stiffness, and toughness, are assessed in an introductory survey where we focused on concrete numerical parameters characterizing mechanical properties. Obtaining ideal stress transfer will require fine optimization of nanotube-polymer interface. SWNT nanocomposites were made here by layer-by-layer (LBL) assembly with poly(vinyl alcohol) (PVA), and the first example of optimization in respect to key parameters determining the connectivity at the graphene-polymer interface, namely, degree of SWNT oxidation and cross-linking chemistry, was demonstrated. The resulting SWNT-PVA composites demonstrated tensile strength (σ(ult)) = 504.5 ± 67.3 MPa, stiffness (E) = 15.6 ± 3.8 GPa, and toughness (K) = 121.2 ± 19.2 J/g with maximum values recorded at σ(ult) = 600.1 MPa, E = 20.6 GPa, and K = 152.1 J/g. This represents the strongest and stiffest nonfibrous SWNT composites made to date outperforming other bulk composites by 2-10 times. Its high performance is attributed to both high nanotube content and efficient stress transfer. The resulting LBL composite is also one of the toughest in this category of materials and exceeding the toughness of Kevlar by 3-fold. Our observation suggests that the strengthening and toughening mechanism originates from the synergistic combination of high degree of SWNT exfoliation, efficient SWNT-PVA binding, crack surface roughening, and fairly efficient distribution of local stress over the SWNT network. The need for a multiscale approach in designing SWNT composites is advocated.

  8. Influence of different surface treatments on the fracture toughness of a commercial ZTA dental ceramic

    Directory of Open Access Journals (Sweden)

    Flavio Teixeira da Silva

    2007-03-01

    Full Text Available The objective of this study was to investigate how mechanical surface treatments performed for removal of excess of molten glass, influence the fracture toughness of a dental zirconia toughened alumina (In-Ceram® Zirconia. Infiltrated ZTA disks were submitted to three different surface treatments (grinding, sandblasting and grinding + sandblasting + annealing. Fracture toughness was accessed through indentation strength test (IS. X ray diffraction was used to investigate the metastability of tetragonal zirconia particles under all treatments proposed. Kruskall-Wallis non-parametrical test and Weibull statistics were used to analyze the results. Grinding (group 1 introduced defects which decreased the fracture toughness and reliability, presenting the lowest K IC. On the other hand, grinding followed by sandblasting and annealing (group 3 presented the highest K IC. Sandblasting (group 2 presented the highest reliability but lower K IC compared to group 3.

  9. Fracture toughness improvements of dental ceramic through use of yttria-stabilized zirconia (YSZ) thin-film coatings.

    Science.gov (United States)

    Chan, Ryan N; Stoner, Brian R; Thompson, Jeffrey Y; Scattergood, Ronald O; Piascik, Jeffrey R

    2013-08-01

    The aim of this study was to evaluate strengthening mechanisms of yttria-stabilized zirconia (YSZ) thin film coatings as a viable method for improving fracture toughness of all-ceramic dental restorations. Bars (2mm×2mm×15mm, n=12) were cut from porcelain (ProCAD, Ivoclar-Vivadent) blocks and wet-polished through 1200-grit using SiC abrasive. A Vickers indenter was used to induce flaws with controlled size and geometry. Depositions were performed via radio frequency magnetron sputtering (5mT, 25°C, 30:1 Ar/O2 gas ratio) with varying powers of substrate bias. Film and flaw properties were characterized by optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Flexural strength was determined by three-point bending. Fracture toughness values were calculated from flaw size and fracture strength. Data show improvements in fracture strength of up to 57% over unmodified specimens. XRD analysis shows that films deposited with higher substrate bias displayed a high %monoclinic volume fraction (19%) compared to non-biased deposited films (87%), and resulted in increased film stresses and modified YSZ microstructures. SEM analysis shows critical flaw sizes of 67±1μm leading to fracture toughness improvements of 55% over unmodified specimens. Data support surface modification of dental ceramics with YSZ thin film coatings to improve fracture toughness. Increase in construct strength was attributed to increase in compressive film stresses and modified YSZ thin film microstructures. It is believed that this surface modification may lead to significant improvements and overall reliability of all-ceramic dental restorations. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  10. Biaxial loading and shallow-flaw effects on crack-tip constraint and fracture-toughness

    International Nuclear Information System (INIS)

    Pennell, W.E.; Bass, B.R.; Bryson, J.W.; McAfee, W.J.; Theiss, T.J.; Rao, M.C.

    1993-01-01

    Uniaxial tests of single-edged notched bend (SENB) specimens with both deep- and shallow-flaws have shown elevated fracture-toughness for the shallow flaws. The elevation in fracture-toughness for shallow flaws has been shown to be the result of reduced constraint at the crack-tip. Biaxial loading has the potential to increase constraint at the crack-tip and thereby reduce some of the shallow-flaw, fracture-toughness elevation. Biaxial fracture-toughness tests have shown that the shallow-flaw, fracture-toughness elevation is reduced but not eliminated by biaxial loading. Dual-parameter, fracture-toughness correlations have been proposed to reflect the effect of crack-tip constraint on fracture-toughness. Test results from the uniaxial and biaxial tests were analyzed using the dual-parameter technology. Discrepancies between analysis results and cleavage initiation site data from fractographic examinations indicate that the analysis models are in need of further refinement. Addition of a precleavage, ductile-tearing element to the analysis model has the potential to resolve the noted discrepancies

  11. Increasing strength, ductility and impact toughness of ultrafine-grained 6063 aluminium alloy by combining ECAP and a high-temperature short-time aging

    International Nuclear Information System (INIS)

    Meyer, L W; Schoenherr, R; Hockauf, M

    2010-01-01

    Since fully-dense ultrafine or nanocrystalline bulk materials can be processed, there has been an increasing scientific interest in several plastic deformation (SPD) procedures, particularly in the last decade. Especially the equal-channel angular pressing (ECAP) has widely been investigated due to its ability of producing billets sufficiently large for industrial applications in functional or structural components. The significant strength increase based on grain refinement is typically accompanied by a significant decrease in ductility and toughness. Within this work, a new methodology was applied for combining ECAP with a subsequent high-temperature short-time aging for the 6063 aluminium alloy. An increase in strength, ductility as well as impact toughness regarding its coarse grained counterparts was reached. More precisely, ultimate tensile strength, elongation to failure and impact toughness were increased by 46%, 21% and 40% respectively. This was observed after only one run of ECAP at room temperature in a solid-solution treated condition and an aging at 170 0 C for 18 minutes. The regular aging time for maximum strength at 170 0 C is around 6 hours. Longer exposure times lead to recrystallisation and, as for regular aging, it leads to overaging, both causing a decrease of properties. The work demonstrates a strategy for an efficient processing of commercial Al-Mg-Si alloys with outstanding mechanical properties.

  12. Preliminary test results from the HSST shallow-crack fracture toughness program

    International Nuclear Information System (INIS)

    Theiss, T.J.; Robinson, G.C.; Rolfe, S.T.

    1991-01-01

    The Heavy Section Steel Technology (HSST) Program under sponsorship of the Nuclear Regulatory Commission (NRC) is investigating the influence of crack depth on the fracture toughness of reactor pressure vessel steel. The ultimate goal of the investigation is the generation of a limited data base of elastic-plastic fracture toughness values appropriate for shallow flaws in a reactor pressure vessel and the application of this data to reactor vessel life assessments. It has been shown that shallow-flaws play a dominant role in the probabilistic fracture mechanics analysis of reactor pressure vessels during a pressurized-thermal-shock event. In addition, recent research has shown that the crack initiation toughness measured using specimens with shallow flaws is greater that the toughness determined with conventional, deeply notched specimens at temperatures within the transition region for non-nuclear steels. The influence of crack depth on the elastic-plastic fracture toughness for prototypic reactor material is being investigated. Preliminary results indicate a significant increase in the toughness associated with shallow-flaws which has the potential to significantly impact the conditional probability of vessel failure. 8 refs., 4 figs., 1 tab

  13. Comparison of Intralaminar and Interlaminar Mode-I Fracture Toughness of Unidirectional IM7/8552 Graphite/Epoxy Composite

    Science.gov (United States)

    Czabaj, Michael W.; Ratcliffe, James

    2012-01-01

    The intralaminar and interlaminar mode-I fracture-toughness of a unidirectional IM7/8552 graphite/epoxy composite were measured using compact tension (CT) and double cantilever beam (DCB) test specimens, respectively. Two starter crack geometries were considered for both the CT and DCB specimen configurations. In the first case, starter cracks were produced by 12.5 micron thick, Teflon film inserts. In the second case, considerably sharper starter cracks were produced by fatigue precracking. For each specimen configuration, use of the Teflon film starter cracks resulted in initially unstable crack growth and artificially high initiation fracture-toughness values. Conversely, specimens with fatigue precracks exhibited stable growth onset and lower initiation fracture toughness. For CT and DCB specimens with fatigue precracks, the intralaminar and interlaminar initiation fracture toughnesses were approximately equal. However, during propagation, the CT specimens exhibited more extensive fiber bridging, and rapidly increasing R-curve behavior as compared to the DCB specimens. Observations of initiation and propagation of intralaminar and interlaminar fracture, and the measurements of fracture toughness, were supported by fractographic analysis using scanning electron microscopy.

  14. Ultra-tough and strong, hybrid thin films based on ionically crosslinked polymers and 2D inorganic platelets

    Science.gov (United States)

    Ji, Dong Hwan; Choi, Suji; Kim, Jaeyun; nanobiomaterials lab Team

    Integration of high strength and toughness tend to be mutually exclusive and synthesized hybrid films with superior mechanical properties have been difficult to fabricate controllable shapes and various scales. Although diverse synthesized hybrid films consisting of organic matrix and inorganic materials with brick-and-mortar structure, show improved mechanical properties, these films are still limited in toughness and fabrication methods. Herein, we report ultra-tough and strong hybrid thin films with self-assembled uniform microstructures with controllable shapes and various scale based on hydrogel-mediated process. Ca2+-crosslinking in alginate chains and well-aligned alumina platelets in alginate matrix lead to a synergistic enhancement of strength and toughness in the resulting film. Consequentially, Ca2+-crosslinked Alg/Alu films showed outstanding toughness of 29 MJ m-3 and tensile strength of 160 MPa. Furthermore, modifying Alu surface with polyvinylpyrrolidone (PVP), tensile strength was further improved up to 200 MPa. Our results suggest an alternative approach to design and processing of self-assembled hydrogel-mediated hybrid films with outstanding mechanical properties.

  15. Research and development of basic technologies for next generation industries, 'high-performance crystalline controlled alloys'. Evaluation on final research and development (first report); Jisedai sangyo kiban gijutsu kenkyu kaihatsu. Koseino kessho seigyo gokin (saishu kenkyu kaihatsu hyoka 1)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1989-05-01

    The present research work has been performing research and development of the following alloys: (1) 'single crystalline alloy' , the entire alloy being composed of one crystal eliminating crystalline boundaries as an ultra heat resistant alloy with emphasis placed on improvement in particularly the creep properties, and 'particle dispersion strengthened alloy', in which ultrafine particles of oxides are dispersed uniformly; and (2) 'ultra heat resistant and tough alloy' targeted at high-temperature toughness by using Ni-group allowing ultra plasticity forging processing by micronizing crystal particles, as an ultra plastic and highly tough alloy having better processibility than conventional alloys, and 'light-weight highly tough alloy' aimed at achieving light weight and high toughness by using Ti-group. Achievements derived from the present research and development may be summarized as follows: in alloy development, alloys having performance of the world's highest level or equivalent have been developed; a manufacturing technology to make products with complex shapes has been established by using the alloy material manufacturing technology and the alloy materials developed therefrom, where prototype components of such shapes as turbine blades and turbine disks for jet engines were fabricated successfully; and the big fruit obtained was that a large number of technological experiences were acquired from this research and development. (NEDO)

  16. Pie technique of LWR fuel cladding fracture toughness test

    International Nuclear Information System (INIS)

    Endo, Shinya; Usami, Koji; Nakata, Masahito; Fukuda, Takuji; Numata, Masami; Kizaki, Minoru; Nishino, Yasuharu

    2006-01-01

    Remote-handling techniques were developed by cooperative research between the Department of Hot Laboratories in the Japan Atomic Energy Research Institute (JAERI) and the Nuclear Fuel Industries Ltd. (NFI) for evaluating the fracture toughness on irradiated LWR fuel cladding. The developed techniques, sample machining by using the electrical discharge machine (EDM), pre-cracking by fatigue tester, sample assembling to the compact tension (CT) shaped test fixture gave a satisfied result for a fracture toughness test developed by NFL. And post-irradiation examination (PIE) using the remote-handling techniques were carried out to evaluate the fracture toughness on BWR spent fuel cladding in the Waste Safety Testing Facility (WASTEF). (author)

  17. Optimizing Wear Resistance and Impact Toughness in High Chromium Iron Mo-Ni Alloy

    Science.gov (United States)

    Singh, K. K.; Verma, R. S.; Murty, G. M. D.

    2009-06-01

    An alloy with carbon and chromium in the range of 2.0 to 2.5% and 20 to 25%, respectively, with the addition of Mo and Ni in the range of 1.0 to 1.5% each when heat-treated at a quenching temperature of 1010 °C and tempering temperature of 550 °C produces a hardness in the range of 54 to 56 HRC and a microstructure that consists of discontinuous bands of high volume (35-40%) of wear resistant primary (eutectic) carbides in a tempered martensitic matrix with uniformly dispersed secondary precipitates. This alloy has been found to possess adequate impact toughness (5-6 J/cm2) with a wear resistance of the order of 3-4 times superior to Mn steel and 1.25 times superior to martensitic stainless steel with a reduction in cost-to-life ratio by a factor of 1.25 in both the cases.

  18. Fracture toughness measurements on zirconia toughened ceramics

    International Nuclear Information System (INIS)

    El Sayed Ali, M.; Toft Soerensen, O.

    1986-12-01

    Three techniques for fracture toughness measurements on zirconia toughened ceramics were evaluated: the notched beam (NB) technique, the indentation fracture (IF) technique and the indentation strength in bending (ISB) technique. Using these techniques comparative measurements were performed on samples prepared by pressing (uniaxial) and sintering of four commercially available powder types. These were: Toya Soda (Japan) powders with the designations TZ3Y (2.86 mole% Y 2 O 3 ), TZ3YA (2.77 mole% Y 2 O 3 , 0.1 wt% Al 2 O 3 ) and TZ3Y20A (2.88 mole% Y 2 O 3 , 20 wt.% Al 2 O 3 ) and a powder supplied by Viking Chemicals (Denmark) designated as YP5Z-2.5 (2.5 mole% Y 2 O 3 ). The measurements showed that similar K Ic values were obtained with the IF- and ISB-techniques, which therefore are recommended for K Ic measurements. Too high values were, however, obtained with the NB-technique which therefore cannot be recommended. Finally, the measurements showed that a high temperature annealing is recommended prior to testing for the IF-technique. (author)

  19. Application of ISRM testing methods to fracture toughness testing of graphite

    International Nuclear Information System (INIS)

    Hashida, T.; Fukasawa, T.; Takahashi, H.; Ishiyama, S.; Oku, T.

    1987-01-01

    Fracture toughness measurements of nuclear grade graphites, IG11 and PGX, were made by means of AE technique. Tests were conducted on edge-notched round bend bar, edge-notched short bar and round compact tension specimens. These round-shaped specimens used in this study have been proposed for standard fracture toughness tests of rock as a draft of testing standard of International Society for Rock Mechanics (ISRM). Taking the observed nonlinear deformation behavior into account, J-integral approach was utilized to determine the fracture toughness of the graphites. It is shown that the critical J integral determined by AE technique, J iAE , is independent of specimen geometry. Based on this experimental results, the fracture toughness K IC of the graphites was determined from the J iAE values. K IC value of IG11 was 1.04 MPa√m, and 0.77 MPa√m for PGX respectively. Furthermore, the specimen size effect of the fracture toughness determined by the J-integral/AE method is discussed. (author)

  20. A toughness and defect size assessment of welded stainless steel components

    International Nuclear Information System (INIS)

    Chipperfield, C.G.

    1978-01-01

    The results of an investigation of the effect of test temperature, stress relieving temperature and weld profile on the initiation toughness of 316 type steels are described. The data indicate that little improvement in weld metal toughness is obtained by stress relieving at temperatures of up to 850 0 C and the magnitude of the toughness is significantly below that of wrought 316 steel. The observed trends in toughness with test temperature or stress relieving temperature have been explained in terms of the effect of these variables on yield strength and work hardening rate. A defect size assessment of a particular component has been made for stress relieved and non-stress relieved conditions. Simple addition of residual to applied stress values indicated that the defect size is in many cases essentially controlled by the magnitude of the residual stress. The possible conservatism of this assessment and the use of initiation toughness values are discussed. (author)

  1. Tough Al-alginate/poly(N-isopropylacrylamide) hydrogel with tunable LCST for soft robotics.

    Science.gov (United States)

    Zheng, Wen Jiang; An, Ning; Yang, Jian Hai; Zhou, Jinxiong; Chen, Yong Mei

    2015-01-28

    Tough Al-alginate/poly(N-isopropylacrylamide) (PNIPAM) hydrogel has been synthesized by introducing an interpenetrating network with hybrid physically cross-linked alginate and chemically cross-linked PNIPAM. Varying the concentration of AlCl3 regulates the mechanical properties of the tough hydrogel and tunes its lower critical solution temperature (LCST) as well. The tough Al-alginate/PNIPAM exhibits 6.3 ± 0.3 MPa of compressive stress and 9.95 of uniaxial stretch. Tunability of LCST is also achieved in a wide range within 22.5-32 °C. A bending beam actuator and a four-arm gripper made of bilayer (Na-alginate/PNIPAM)/(Al-alginate/PNIPAM) hydrogel as prototype of all-hydrogel soft robotics are demonstrated. A finite element (FE) simulation model is developed to simulate the deformation of the soft robotics. The FE simulation not only reproduces the deformation process of performed experiments but also predicts more complicated devices that can be explored in the future. This work broadens the application of temperature-responsive PNIPAM-based hydrogels.

  2. A tough-love pedagogy in rehabilitation: integration of rehabilitation ideology with local cultures.

    Science.gov (United States)

    Chang, Ling-Hui; Wang, Jye

    2009-09-01

    This study problematizes a unique therapeutic relationship in rehabilitation and how the interaction reflects the integration of rehabilitation ideology with local cultures. The data drew from a larger ethnographic study of a rehabilitation unit in Taiwan. Participants included 21 patient-caregiver pairs and their rehabilitation professionals. They participated in in-depth interviews and participant observation. A tough-love pedagogy emerged as a unique therapeutic relationship in the unit. Patients were asked to interpret the stress with therapy as an inevitable, beneficial experience toward recovery. A prevalent supposition that equated poor physical performance with weak morale legitimized the approach. Cultural metaphors used to describe and define rehabilitation transformed the stress that patients experienced with strenuous exercises into a beneficial substance that aids recovery. The transformation of the therapeutic relationship into a pedagogical one helped connect rehabilitation to shared educational experiences. In the unit, the complicit practice of therapists, caregivers, and patients established and perpetuated the practice of a tough-love pedagogy. The congruence between this tough-love approach and traditional Chinese pedagogical principles made the approach legitimate and desired.

  3. Effect of Static-Dynamic Coupling Loading on Fracture Toughness and Failure Characteristics in Marble

    Directory of Open Access Journals (Sweden)

    Z. Q. Yin

    2014-03-01

    Full Text Available Fracture experiments in a notched semi-circular bend configuration were conducted to test the dynamic fracture toughness of a marble under static-dynamic coupling load using a modified split Hopkinson pressure bar. The fracture process of the specimen was monitored using a high speed (HS camera. Based on digital image correlation (DIC and strain gauges, the full-field strain fields and time-to-fracture of the marble were measured under static-dynamic coupling load. Experimental results show that dynamic fracture toughness was well determined, and the HS-DIC technique provides reliable full-field strain fields in the specimens under static-dynamic coupling loads. The failure characteristics of the marble under external impact were affected obviously by pre-compression stress. Increase of axial pre-compression stress was helpful to improve the crack propagation velocity, and dynamic crack initiation toughness was decreased.

  4. Coupling of the reservoir simulator TOUGH and the wellbore simulator WFSA

    Energy Technology Data Exchange (ETDEWEB)

    Hadgu, T.; Zimmerman, R.W.; Bodvarsson [Lawrence Berkeley Laboratory, Berkeley, CA (United States)

    1995-03-01

    The reservoir simulator TOUGH and the wellbore simulator WFSA have been coupled, so as to allow simultaneous modeling of the flow of geothermal brine in the reservoir as well as in the wellbore. A new module, COUPLE, allows WFSA to be called as a subroutine by TOUGH. The mass flowrate computed by WFSA now serves as a source/sink term for the TOUGH wellblocks. Sample problems are given to illustrate the use of the coupled codes. One of these problems compares the results of the new simulation method to those obtained using the deliverability option in TOUGH. The coupled computing procedure is shown to simulate more accurately the behavior of a geothermal reservoir under exploitation.

  5. The origins of mental toughness – prosocial behavior and low internalizing and externalizing problems at age 5 predict higher mental toughness scores at age 14

    Directory of Open Access Journals (Sweden)

    Dena Sadeghi Bahmani

    2016-08-01

    Full Text Available Background: The concept of mental toughness has gained increasing importance among groups other than elite athletes by virtue of its psychological importance and explanatory power for a broad range of health-related behaviors. However, no study has focused so far on the psychological origins of mental toughness. Therefore, the aims of the present study were: to explore, to what extent the psychological profiles of preschoolers aged five were associated with both 1 mental toughness scores and 2 sleep disturbances at age 14, and 3 to explore possible gender differences.Method: Nine years after their first assessment at age five (preschoolers, a total of 77 adolescents (mean age: 14.35 years; SD = 1.22; 42% females took part in this follow-up study. At baseline, both parents and teachers completed the Strengths and Difficulties Questionnaire (SDQ, covering internalizing and externalizing problems, hyperactivity, negative peer relationships, and prosocial behavior. At follow-up, participants completed a booklet of questionnaires covering socio-demographic data, mental toughness, and sleep disturbances.Results: Higher prosocial behavior, lower negative peer relationships, and lower internalizing and externalizing problems at age five, as rated by parents and teachers, were associated with self-reported higher mental toughness and lower sleep disturbances at age 14. At age 14, and relative to males, females had lower MT scores and reported more sleep disturbances.Results: Higher prosocial behavior, lower negative peer relationships, and lower internalizing and externalizing problems at age five, as rated by parents and teachers, predicted self-reported higher mental toughness and lower sleep disturbances at age 14. At age 14, and relative to males, females had lower MT scores and reported more sleep disturbance.Conclusions: The pattern of results suggests that mental toughness traits during adolescence may have their origins in the pre-school years.

  6. Solving iTOUGH2 simulation and optimization problems using the PEST protocol

    Energy Technology Data Exchange (ETDEWEB)

    Finsterle, S.A.; Zhang, Y.

    2011-02-01

    The PEST protocol has been implemented into the iTOUGH2 code, allowing the user to link any simulation program (with ASCII-based inputs and outputs) to iTOUGH2's sensitivity analysis, inverse modeling, and uncertainty quantification capabilities. These application models can be pre- or post-processors of the TOUGH2 non-isothermal multiphase flow and transport simulator, or programs that are unrelated to the TOUGH suite of codes. PEST-style template and instruction files are used, respectively, to pass input parameters updated by the iTOUGH2 optimization routines to the model, and to retrieve the model-calculated values that correspond to observable variables. We summarize the iTOUGH2 capabilities and demonstrate the flexibility added by the PEST protocol for the solution of a variety of simulation-optimization problems. In particular, the combination of loosely coupled and tightly integrated simulation and optimization routines provides both the flexibility and control needed to solve challenging inversion problems for the analysis of multiphase subsurface flow and transport systems.

  7. Research and Application of New Type of High Performance Titanium Alloy

    Directory of Open Access Journals (Sweden)

    ZHU Zhishou

    2016-06-01

    Full Text Available With the continuous extension of the application quantity and range for titanium alloy in the fields of national aviation, space, weaponry, marine and chemical industry, etc., even more critical requirements to the comprehensive mechanical properties, low cost and process technological properties of titanium alloy have been raised. Through the alloying based on the microstructure parameters design, and the comprehensive strengthening and toughening technologies of fine grain strengthening, phase transformation and process control of high toughening, the new type of high performance titanium alloy which has good comprehensive properties of high strength and toughness, anti-fatigue, failure resistance and anti-impact has been researched and manufactured. The new titanium alloy has extended the application quantity and application level in the high end field, realized the industrial upgrading and reforming, and met the application requirements of next generation equipment.

  8. Toughness of membranes applied in polymer electrolyte fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Kiefer, J; Brack, H P; Scherer, G G [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    Since several years we apply the radiation-grafting technique to prepare polymeric membranes for application in polymer electrolyte fuel cells (PEFCs). Our investigations presented here focus on changes in toughness of these materials after the various synthesis steps and the importance of membrane toughness for their application in PEFCs. (author) 2 figs., 4 refs.

  9. The Fracture Toughness of Nuclear Graphites Grades

    Energy Technology Data Exchange (ETDEWEB)

    Burchell, Timothy D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Erdman, III, Donald L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Lowden, Rick R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hunter, James A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hannel, Cara C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-04-01

    New measurements of graphite mode I critical stress intensity factor, KIc (commonly referred to as the fracture toughness) and the mode II critical shear stress intensity, KIIc, are reported and compared with prior data for KIc and KIIc. The new data are for graphite grades PCEA, IG-110 and 2114. Variations of KIc and acoustic emission (AE) data with graphite texture are reported and discussed. The Codes and Standards applications of fracture toughness, KIc, data are also discussed. A specified minimum value for nuclear graphite KIc is recommended.

  10. Tough Choices or Tough Times: The Report of the New Commission on the Skills of the American Workforce. Revised and Expanded Edition

    Science.gov (United States)

    Jossey-Bass, An Imprint of Wiley, 2008

    2008-01-01

    "Tough Choices or Tough Times," the report of the New Commission on the Skills of the American Workforce, shows how the dynamics of the global economy will lead to a steady decline in the American standard of living if this country does not undertake the first thorough overhaul of its education system in a century. This new revised and expanded…

  11. Fracture toughness of Ceramic-Fiber-Reinforced Metallic-Intermetallic-Laminate (CFR-MIL) composites

    International Nuclear Information System (INIS)

    Vecchio, Kenneth S.; Jiang, Fengchun

    2016-01-01

    Novel Ceramic-Fiber-Reinforced-Metal-Intermetallic-Laminate (CFR-MIL) composites, Ti–Al 3 Ti–Al 2 O 3 –Al, were synthesized by reactive foil sintering in air. Microstructure controlled material architectures were achieved with continuous Al 2 O 3 fibers oriented in 0° and 90° layers to form fully dense composites in which the volume fractions of all four component phases can be tailored. Bend fracture specimens were cut from the laminate plates in divider orientation, and bend tests were performed to study the fracture behavior of CFR-MIL composites under three-point and four-point bending loading conditions. The microstructures and fractured surfaces of the CFR-MIL composites were examined using optical microscopy and scanning electron microscopy to establish a correlation between the fracture toughness, fracture surface morphology and microstructures of CFR-MIL composites. The fracture and toughening mechanisms of the CFR-MIL composites are also addressed. The present experimental results indicate that the fracture toughness of CFR-MIL composites determined by three- and four-point bend loading configurations are quite similar, and increased significantly compared to MIL composites without ceramic fiber reinforcement. The interface cracking behavior is related to the volume fraction of the brittle Al 3 Ti phase and residual ductile Al, but the fracture toughness values appear to be insensitive to the ratio of these two phases. The toughness appears to be dominated by the ductility/strength of the Ti layers and the strength and crack bridging effect of the ceramic fibers.

  12. Application of local approach to quantitative prediction of degradation in fracture toughness of steels due to pre-straining and irradiation

    International Nuclear Information System (INIS)

    Miyata, T.; Tagawa, T.

    1996-01-01

    Degradation of cleavage fracture toughness for low carbon steels due to pre-straining and irradiation was investigated on the basis of the local fracture criterion approach. Formulation of cleavage fracture toughness through the statistical modelling proposed by BEREMIN has been simplified by the present authors to the expression involving yield stress and cleavage fracture stress of materials. A few percent pre-strain induced by cold rolling deteriorates significantly the cleavage fracture toughness. Ductile-brittle transition temperature is increased to more than 70 C higher by 8% straining in 500 MPa class high strength steel. Quantitative prediction of degradation has been successfully examined through the formulation of the cleavage fracture toughness. Analytical and experimental results indicate that degradation in toughness is caused by the increase of flow stress in pre-strained materials. Quantitative prediction of degradation of toughness due to irradiation has been also examined for the past experiments on the basis of the local fracture criterion approach. Analytical prediction from variance of yield stress by irradiation is well consistent with the experimental results. (orig.)

  13. The toughness of split graphs

    NARCIS (Netherlands)

    Woeginger, G.J.

    1998-01-01

    In this short note we argue that the toughness of split graphs can be computed in polynomial time. This solves an open problem from a recent paper by Kratsch et al. (Discrete Math. 150 (1996) 231–245).

  14. TOUGH Simulations of the Updegraff's Set of Fluid and Heat Flow Problems

    Energy Technology Data Exchange (ETDEWEB)

    Moridis, G.J.; Pruess (editor), K.

    1992-11-01

    The TOUGH code [Pruess, 1987] for two-phase flow of water, air, and heat in penneable media has been exercised on a suite of test problems originally selected and simulated by C. D. Updegraff [1989]. These include five 'verification' problems for which analytical or numerical solutions are available, and three 'validation' problems that model laboratory fluid and heat flow experiments. All problems could be run without any code modifications (*). Good and efficient numerical performance, as well as accurate results were obtained throughout. Additional code verification and validation problems from the literature are briefly summarized, and suggestions are given for proper applications of TOUGH and related codes.

  15. Evaluation of Microstructure and Toughness of AISI D2 Steel by Bright Hardening in Comparison with Oil Quenching

    Science.gov (United States)

    Torkamani, H.; Raygan, Sh.; Rassizadehghani, J.

    2011-12-01

    AISI D2 is used widely in the manufacture of blanking and cold-forming dies, on account of its excellent hardness and wear behavior. Increasing toughness at a fixed high level of hardness is growing requirement for this kind of tool steel. Improving microstructure characteristics, especially refinement of coarse carbides, is an appropriate way to meet such requirement. In this study, morphology and size of carbides in martensite matrix were compared between two kinds of samples, which were bright hardened (quenching in hot alkaline salt bath consisting of 60% KOH and 40% NaOH) at 230 °C and quenched in oil bath at 60 °C. Results showed that morphology and distribution of carbides in samples performed by bright hardening were finer and almost spherical compared to that of oil quenched. This microstructure resulted in an improvement in toughness and tensile properties of alloy.

  16. Fracture Toughness of Carbon Nanotube-Reinforced Metal- and Ceramic-Matrix Composites

    International Nuclear Information System (INIS)

    Chen, Y.L.; Liu, B.; Hwang, K.C.; Chen, Y.L.; Huang, Y.

    2011-01-01

    Hierarchical analysis of the fracture toughness enhancement of carbon nanotube- (CNT-) reinforced hard matrix composites is carried out on the basis of shear-lag theory and fracture mechanics. It is found that stronger CNT/matrix interfaces cannot definitely lead to the better fracture toughness of these composites, and the optimal interfacial chemical bond density is that making the failure mode just in the transition from CNT pull-out to CNT break. For hard matrix composites, the fracture toughness of composites with weak interfaces can be improved effectively by increasing the CNT length. However, for soft matrix composite, the fracture toughness improvement due to the reinforcing CNTs quickly becomes saturated with an increase in CNT length. The proposed theoretical model is also applicable to short fiber-reinforced composites.

  17. Fracture toughness of Charpy-size compound specimens and its application in engineering

    International Nuclear Information System (INIS)

    Zhang, X.P.; Shi, Y.W.

    1994-01-01

    The use of a pre-cracked Charpy-size specimen with a side-groove to evaluate the fracture toughness of materials has been researched and considered. This method not only satisfies the demand for small-size specimens in surveillance tests of fracture toughness but also avoids using complicated physical methods to monitor the initial conditions of crack propagation. For most materials this method has solved the problem in which the small-size specimen did not satisfy the valid conditions of a fracture toughness measurement. In order to obtain more information from neutron-irradiated sample specimens and raise the reliability of fracture toughness surveillance tests, it has been considered more important to repeatedly exploit the broken Charpy-size specimen tested in the surveillance test, and to make it renewable. In this work, on the renewing design and utilization of Charpy-size specimens, nine data on fracture toughness can be obtained from one pre-cracked side-grooved Charpy-size specimen, while at present usually only one to three data on fracture toughness can be obtained from one Charpy-size specimen. Thus, it is found that the new method would improve the reliability of fracture toughness surveillance testing and evaluation. In addition, some factors that affect the optimum design of pre-cracked deep side-groove Charpy-size compound specimens have also been discussed. (author)

  18. Fracture toughness of neutron irradiated solid and powder HIP 316L(N). ITER Task 214, NET deliverable GB6 ECN-5

    International Nuclear Information System (INIS)

    Rensman, J.; Van den Broek, F.P.; Jong, M.; Van Osch, E.V.

    1998-04-01

    The fracture toughness properties of unirradiated and neutron irradiated type 316L(N) stainless steel plate (European Reference Heat ERHII), conventional 316L(N) solid HIP joints (heat PM-130), and 316L(N)-1G powder HIP material have been measured. Compact tension specimens with a thickness of 12 and 5 mm were irradiated in the High Flux Reactor (HFR) in Petten, The Netherlands, simulating the fusion reactor's first wall conditions by a combination of high displacement damage with proportional amounts of helium. The solid HIP (or HIP-bonded) CT-specimens were irradiated in two separate experiments: SIWAS-6 with 1.3 to 2.3 dpa (1.7 dpa av.) at 353 K, and CHARIOT-3 with 2.7 to 3.1 dpa (2.9 dpa av.) at 600 K. The plate material and powder HIP CT-specimens were irradiated in one experiment only, SIWAS-6. The helium content is up to 20 appm for the 2.9 dpa (av.) dose level. Testing temperatures of 353K and 573K have been used for the fracture toughness experiments. The report contains the experimental conditions and summarises the results, which are given in terms of J-resistance curve fits. The main conclusions are that all three materials have very high toughness in the unirradiated state with little difference between them; the solid HIP has the highest toughness, the powder HIP lowest. The toughness of all three materials is reduced significantly by irradiation, the reduction is the least for the plate material and the highest for the powder HIP material. However, many, but not all, of the solid HIP CT specimens showed debonding of the joint during testing. The machined notch of the CT specimens was not exactly on the joint interface, which could lead to unjustified interpretation of the measured values as being the toughness of the joint, the toughness of the joint being probably much lower. The reduction by irradiation of the fracture toughness of the powder HIP material is clearly larger than for plate material, which is confirmed by the observed early initiation

  19. Influence of side-groove root radius on the ductile fracture toughness of miniature C(T) specimens

    Energy Technology Data Exchange (ETDEWEB)

    Lucon, E.; Scibetta, M.

    2009-05-15

    The use of miniature C(T) specimens, MC(T), for fracture toughness measurements in the upper shelf regime has been investigated at SCK-CEN since 2004, in the framework of the Electrabel/Tractebel SCK-CEN Convention (now General Framework Agreement SUEZ-SCK-CEN). This geometry has been used and validated on both unirradiated (2004-05) and irradiated (2006) materials, mainly reactor pressure vessel (RPV) steels. While side-grooved MC(T) specimens have shown in all conditions a systematically lower tearing resistance and ductile crack initiation toughness as compared to standard-size 1TC(T) samples, the only plain-sided MC(T) specimen tested in 2005 exhibited very high ductile fracture toughness, thus pointing at a strong influence of side-grooving on the upper shelf properties of MC(T) specimens. This study investigates the influence of side-grooving on the initiation toughness and tearing resistance of MC(T) specimens, as a function of the root radius of the side-groove (ranging from 0.1 to 1 mm) and in comparison with plain-sided MC(T) and reference 1TC(T) samples. The material used is the well characterized DIN 22NiMoCr37 RPV steel, which had been used in the European project which generated the famous EURO fracture toughness data set.

  20. Dynamic Fracture Initiation Toughness at Elevated Temperatures With Application to the New Generation of Titanium Aluminide Alloys. Chapter 8

    Science.gov (United States)

    Shazly, Mostafa; Prakash, Vikas; Draper, Susan; Shukla, Arun (Editor)

    2006-01-01

    Recently, a new generation of titanium aluminide alloy, named Gamma-Met PX, has been developed with better rolling and post-rolling characteristics. I'revious work on this alloy has shown the material to have higher strengths at room and elevated temperatures when compared with other gamma titanium aluminides. In particular, this new alloy has shown increased ductility at elevated temperatures under both quasi-static and high strain rate uniaxial compressive loading. However, its high strain rate tensile ductility at room and elevated temperatures is limited to approx. 1%. In the present chapter, results of a study to investigate the effects of loading rate and test temperature on the dynamic fracture initiation toughness in Gamma-Met PX are presented. Modified split Hopkinson pressure bar was used along with high-speed photography to determine the crack initiation time. Three-point bend dynamic fracture experiments were conducted at impact speeds of approx. 1 m/s and tests temperatures of up-to 1200 C. The results show that thc dynamic fracture initiation toughness decreases with increasing test temperatures beyond 600 C. Furthermore, thc effect of long time high temperature air exposure on the fracture toughness was investigated. The dynamic fracture initiation toughness was found to decrease with increasing exposure time. The reasons behind this drop are analyzed and discussed.

  1. Preface: Research advances in vadose zone hydrology through simulations with the TOUGH codes

    International Nuclear Information System (INIS)

    Finsterle, Stefan; Oldenburg, Curtis M.

    2004-01-01

    symposium, with special attention to issues related to the vadose zone and unsaturated flow systems. The first paper, written by the original developer of TOUGH, Karsten Pruess, provides an overview of the history of the TOUGH codes, the main physical processes considered, their mathematical and numerical implementation, and case studies. That paper is followed by a review article summarizing inverse modeling applications performed by iTOUGH2. A subsequent group of papers deals with diverse unsaturated zone systems, highlighting the versatility of the code to handle a variety of processes in different geologic settings. Simulation capabilities of the TOUGH codes are increasingly used for geologic carbon sequestration studies as testified by the next group of papers. The final series of papers demonstrates the use of the TOUGH codes in support of remediation and engineering applications. These studies discuss biological and reactive chemical transport simulations, the design of clean-up operations and landfill management, and the analysis of engineered soil stabilization. As guest editors, we thank the authors for their interesting contributions, and the many reviewers for their careful and constructive review comments. Finally, on behalf of all of the authors and ourselves, we express our sincerest appreciation to Rien van Genuchten for providing the opportunity to publish these papers together in a Special Section of ''Vadose Zone Journal''

  2. Tough Blends of Polylactide and Castor Oil

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, Megan L.; Paxton, Jessica M.; Hillmyer, Marc A. (UMM)

    2012-10-10

    Poly(l-lactide) (PLLA) is a renewable resource polymer derived from plant sugars with several commercial applications. Broader implementation of the material is limited due to its inherent brittleness. We show that the addition of 5 wt % castor oil to PLLA significantly enhances the overall tensile toughness with minimal reductions in the modulus and no plasticization of the PLLA matrix. In addition, we used poly(ricinoleic acid)-PLLA diblock copolymers, synthesized entirely from renewable resources, as compatibilizers for the PLLA/castor oil blends. Ricinoleic acid, the majority fatty acid comprising castor oil, was polymerized through a lipase-catalyzed condensation reaction. The resulting polymers contained a hydroxyl end-group that was subsequently used to initiate the ring-opening polymerization of L-lactide. The binary PLLA/castor oil blend exhibited a tensile toughness seven times greater than neat PLLA. The addition of block copolymer allowed for control over the morphology of the blends, and even further improvement in the tensile toughness was realized - an order of magnitude larger than that of neat PLLA.

  3. Tough blends of polylactide and castor oil.

    Science.gov (United States)

    Robertson, Megan L; Paxton, Jessica M; Hillmyer, Marc A

    2011-09-01

    Poly(l-lactide) (PLLA) is a renewable resource polymer derived from plant sugars with several commercial applications. Broader implementation of the material is limited due to its inherent brittleness. We show that the addition of 5 wt % castor oil to PLLA significantly enhances the overall tensile toughness with minimal reductions in the modulus and no plasticization of the PLLA matrix. In addition, we used poly(ricinoleic acid)-PLLA diblock copolymers, synthesized entirely from renewable resources, as compatibilizers for the PLLA/castor oil blends. Ricinoleic acid, the majority fatty acid comprising castor oil, was polymerized through a lipase-catalyzed condensation reaction. The resulting polymers contained a hydroxyl end-group that was subsequently used to initiate the ring-opening polymerization of l-lactide. The binary PLLA/castor oil blend exhibited a tensile toughness seven times greater than neat PLLA. The addition of block copolymer allowed for control over the morphology of the blends, and even further improvement in the tensile toughness was realized-an order of magnitude larger than that of neat PLLA.

  4. FLEXURAL TOUGHNESS OF STEEL FIBER REINFORCED CONCRETE

    Directory of Open Access Journals (Sweden)

    Fehmi ÇİVİCİ

    2006-02-01

    Full Text Available Fiber concrete is a composite material which has mechanical and physical characteristics unlike plain concrete. One of the important mechanical characteristics of fiber concrete is its energy absorbing capability. This characteristics which is also called toughness, is defined as the total area under the load-deflection curve. A number of composite characteristics such as crack resistance, ductility and impact resistance are related to the energy absorbtion capacity. According to ASTM C 1018 and JSCE SF-4 the calculation of toughness is determined by uniaxial flexural testing. Fiber concrete is often used in plates such as bridge decks, airport pavements, parking areas, subjected to cavitation and erosion. In this paper, toughness has been determined according to ASTM C 1018 and JSCE SF-4 methods by testing beam specimens. Energy absorbing capacities of plain and steel fiber reinforced concrete has been compared by evaluating the results of two methods. Also plain and steel fiber reinforced plate specimens behaviors subjected to biaxial flexure are compared by the loaddeflection curves of each specimen.

  5. The effect of specimen and flaw dimensions on fracture toughness

    International Nuclear Information System (INIS)

    Nevalainen, M.J.

    1997-06-01

    The effect of the specimen size and geometry on fracture toughness has been investigated both by experimental tests and computational analyses. The methods for constraint description, namely T-stress, Q-parameter and Small-Scale Yielding Correction (SSYC) have been compared and applied for various geometries. A statistical treatment for the specimen thickness effect on cleavage fracture toughness has been investigated. Elliptical surface cracks were compared with straight-thickness cracks and a method for crack shape correction was presented. Based on the results, the differences in apparent fracture toughness values obtained from various specimen configurations can be better understood and taken into account

  6. Incorporation of the capillary hysteresis model HYSTR into the numerical code TOUGH

    International Nuclear Information System (INIS)

    Niemi, A.; Bodvarsson, G.S.; Pruess, K.

    1991-11-01

    As part of the work performed to model flow in the unsaturated zone at Yucca Mountain Nevada, a capillary hysteresis model has been developed. The computer program HYSTR has been developed to compute the hysteretic capillary pressure -- liquid saturation relationship through interpolation of tabulated data. The code can be easily incorporated into any numerical unsaturated flow simulator. A complete description of HYSTR, including a brief summary of the previous hysteresis literature, detailed description of the program, and instructions for its incorporation into a numerical simulator are given in the HYSTR user's manual (Niemi and Bodvarsson, 1991a). This report describes the incorporation of HYSTR into the numerical code TOUGH (Transport of Unsaturated Groundwater and Heat; Pruess, 1986). The changes made and procedures for the use of TOUGH for hysteresis modeling are documented

  7. Enhancement of low temperature toughness of nanoprecipitates strengthened ferritic steel by delamination structure

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yu; Xu, Songsong; Li, Junpeng; Zhang, Jian [Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin 150001, P R China (China); Sun, Liangwei; Chen, Liang; Sun, Guangai; Peng, Shuming [Key Laboratory of Neutron Physics and Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics (CAEP), Mianyang 621999 (China); Zhang, Zhongwu, E-mail: zwzhang@hrbeu.edu.cn [Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin 150001, P R China (China)

    2017-04-13

    This study investigated the effects of aging and thermomechanical treatments on the microstructure evolution and mechanical properties of a nanoprecipitates strengthened ferritic steel. The toughness of steel at various temperatures was measured carefully and correlated with microstructural features. Tensile tests show that aging can improve the mechanical strength without scarifying the ductility. With high yield strength of ~1000 MPa, excellent low temperature Charpy impact energy more than 300 J at −80 °C can be obtained. The ductile brittle transition temperature (DBTT) is lower than −80 °C. The high strength can be contributed by the nanocluster precipitation as determined by small angle neutron scattering and transmission electron microscopy. The excellent low temperature toughness is attributed to the delamination structure of the steel, which blunts the cracks and restrains the crack propagation.

  8. Fracture toughness of irradiated Zr-2.5Nb pressure tube from KAPS-2 evaluated using disk compact tension specimens

    International Nuclear Information System (INIS)

    Shah, Priti Kotak; Dubey, J.S.; Balakrishnan, K.S.; Shriwastaw, R.S.; Dhotre, M.P.; Bhandekar, A.; Pandit, K.M.; Anantharaman, S.

    2013-12-01

    The report gives the results of the fracture toughness tests carried out over the range of temperatures on specimens prepared from the irradiated S-07Zr-2.5Nb pressure tube removed from Kakrapar Atomic Power Station-2 (KAPS-2) as a part of materials surveillance programme. The pressure tube had experienced ∼ 8 effective full power years (EFPY) of reactor operation and had hydrogen equivalent (H eq ) content less than 20 ppm along the tube length. The fracture toughness tests have been carried out using 30 mm Disk Compact Tension (DCT) specimens, that were punched out of the irradiated pressure tube. The disk punching was carried out using specially made shielded enclosure and hydraulic press. Fatigue pre-cracking and fracture toughness tests were performed using servo-hydraulic universal testing machine with Direct Current Potential Drop (DCPD) equipment to monitor the crack length. The tests were carried out at different test temperature from ambient to 300℃. The fracture toughness values have been used to estimate the critical pressure for the tube. The fracture properties indicate that such tubes have sufficient toughness to satisfy the Leak-Before-Break (LBB) criterion for in-reactor operation. (author)

  9. Fracture toughness behavior of irradiated stainless steel in PWR systems

    Energy Technology Data Exchange (ETDEWEB)

    Xu, H.; Fyfitch, S. [AREVA NP Inc., Lynchburg, Pennsylvania (United States); Tang, H.T. [Electric Power Research Inst., Palo Alto, California (United States)

    2007-07-01

    Data from available research programs were collected and evaluated by the Electric Power Research Institute (EPRI) Materials Reliability Program (MRP) to determine the relationship between fracture toughness and neutron fluence for conditions representative of pressurized water reactor (PWR) conditions. It is shown that the reduction of fracture toughness with increasing neutron dose in both boiling water reactors (BWRs) and PWRs is consistent with that observed in fast reactors. The lower bound fracture toughness observed for irradiated stainless steels in PWRs is 38 MPa{radical}m (34.6 ksi{radical}in) at neutron exposures greater than 6.7 X 10{sup 21} n/cm{sup 2} (E > 1.0 MeV) or approximately 10 dpa. For such levels of fracture toughness, it is recommended that linear-elastic fracture mechanics (LEFM) analyses be considered for design and operational analyses. The results from this study can be used by the nuclear industry to assess the effects of irradiation on stainless steels in PWR systems. (author)

  10. Fracture Toughness of Carbon Nanotube-Reinforced Metal- and Ceramic-Matrix Composites

    Directory of Open Access Journals (Sweden)

    Y. L. Chen

    2011-01-01

    Full Text Available Hierarchical analysis of the fracture toughness enhancement of carbon nanotube- (CNT- reinforced hard matrix composites is carried out on the basis of shear-lag theory and facture mechanics. It is found that stronger CNT/matrix interfaces cannot definitely lead to the better fracture toughness of these composites, and the optimal interfacial chemical bond density is that making the failure mode just in the transition from CNT pull-out to CNT break. For hard matrix composites, the fracture toughness of composites with weak interfaces can be improved effectively by increasing the CNT length. However, for soft matrix composite, the fracture toughness improvement due to the reinforcing CNTs quickly becomes saturated with an increase in CNT length. The proposed theoretical model is also applicable to short fiber-reinforced composites.

  11. FaceSheet Push-off Tests to Determine Composite Sandwich Toughness at Cryogenic Temperatures

    Science.gov (United States)

    Gates, Thomas S.; Herring, Helen M.

    2001-01-01

    A new novel test method, associated analysis, and experimental procedures are developed to investigate the toughness of the facesheet-to-core interface of a sandwich material at cryogenic temperatures. The test method is designed to simulate the failure mode associated with facesheet debonding from high levels of gas pressure in the sandwich core. The effects of specimen orientation are considered, and the results of toughness measurements are presented. Comparisons are made between room and liquid nitrogen (-196 C) test temperatures. It was determined that the test method is insensitive to specimen facesheet orientation and strain energy release rate increases with a decrease in the test temperature.

  12. Fracture toughness and crack growth resistance of pressure vessel plate and weld metal steels

    International Nuclear Information System (INIS)

    Moskovic, R.

    1988-01-01

    Compact tension specimens were used to measure the initiation fracture toughness and crack growth resistance of pressure vessel steel plates and submerged arc weld metal. Plate test specimens were manufactured from four different casts of steel comprising: aluminium killed C-Mn-Mo-Cu and C-Mn steel and two silicon killed C-Mn steels. Unionmelt No. 2 weld metal test specimens were extracted from welds of double V butt geometry having either the C-Mn-Mo-Cu steel (three weld joints) or one particular silicon killed C-Mn steel (two weld joints) as parent plate. A multiple specimen test technique was used to obtain crack growth data which were analysed by simple linear regression to determine the crack growth resistance lines and to derive the initiation fracture toughness values for each test temperature. These regression lines were highly scattered with respect to temperature and it was very difficult to determine precisely the temperature dependence of the initiation fracture toughness and crack growth resistance. The data were re-analysed, using a multiple linear regression method, to obtain a relationship between the materials' crack growth resistance and toughness, and the principal independent variables (temperature, crack growth, weld joint code and strain ageing). (author)

  13. Fracture toughness evaluation of steels through master curve approach using Charpy impact specimens

    International Nuclear Information System (INIS)

    Chatterjee, S.; Sriharsha, H.K.; Shah, Priti Kotak

    2007-01-01

    The master curve approach can be used for the evaluation of fracture toughness of all steels which exhibit a transition between brittle to ductile mode of fracture with increasing temperature, and to monitor the extent of embrittlement caused by metallurgical damage mechanisms. This paper details the procedure followed to evaluate the fracture toughness of a typical ferritic steel used as material for pressure vessels. The potential of master curve approach to overcome the inherent limitations of the estimation of fracture toughness using ASME Code reference toughness is also illustrated. (author)

  14. Fracture toughness calculation using dynamic testing

    International Nuclear Information System (INIS)

    Perosanz, F. J.; Serrano, M.; Martinez, C.; Lapena, J.

    1998-01-01

    The most critical component of a Nuclear Power Station is the Reactor Pressure Vessel (RPV), due to safety and integrity requirements. The RPV is subjected to neutron radiation and this phenomenon lead to microstructural changes in the material and modifications in the mechanical properties. Due to this effects, it is necessary to assess the structural integrity of the RPV along the operational life through surveillance programs. The main objective of this surveillance programs is to determine the fracture toughness of the material. At present this objective is reached combining direct measures and prediction techniques. In this work, direct measures of fracture toughness using instrumented Charpy V impact testing are present using a CIEMAT development on analysis of results. (Author) 6 refs

  15. Fracture toughness and failure mechanism of high performance concrete incorporating carbon nanotubes

    Directory of Open Access Journals (Sweden)

    A. Khitab

    2017-10-01

    Full Text Available Cement and concrete composites are inherently brittle and exhibit very less tensile/flexural strength capacity as compared to their compressive strength. Use of thoroughly dispersed carbon nanotubes in the concrete matrix is one of the possible solution for enhancing mechanical properties in tension/flexure. In the present research work, small fractions of multiwall carbon nanotube (MWCNTs i.e. 0.05 and 0.10 wt% of cement have been integrated into the cement concrete to study their effect on the mechanical properties of the resultant concrete mixtures. The enhanced performance of the whole mix lies on a single point that MWCNTs must be thoroughly disperse in the mixture. Hence, special arrangement through usage of high energy sonication along with amended acrylic based polymer (performing as a surfactant was made to have a uniform dispersion of MWCNTs in the concrete mix. The testing of concrete samples includes i.e., flexure, splitting tensile and compressive strengths after 3, 7, 28 and 56 days of curing. After having comparison with the control mix cured for 28 days, it was observed that the addition of 0.05 wt% MWCNTs increased the splitting tensile strength by 20.58%, flexural strength by 26.29% and compressive strength by 15.60%. Through above results, which verify the increase in concrete mix strength after adding MWCNTs, these MWCNTs may be incorporated in the treatment of Nano/micro cracks completed through process of connecting, branching and pinning. Similarly, as proved in threepoint bending tests, MWCNTs also enhances the breaking strains as well as the fracture energy of the concrete mixes, besides, imparting increase to the strength. The investigations have shown that incorporating lesser amounts of MWCNTs i.e., 0.05 and 0.10 wt% of cement to the concrete mixes after insuring there complete dispersion, unusually improve their properties like mechanical strengths and fracture behavior

  16. Evaluation of toughness degradation by small punch (SP) tests for neutron irradiated structural steels

    International Nuclear Information System (INIS)

    Misawa, Toshihei; Hamaguchi, Yoshikazu; Kimura, Akihiko; Eto, Motokuni; Suzuki, Masahide; Nakajima, Nobuya.

    1992-01-01

    The small punch (SP) test as one of the useful small specimen testing technique (SSTT) has been developed to evaluate the fracture toughness, ductile-brittle transition temperature (DBTT) and tensile properties for neutron irradiated structural materials. The SP tests using the miniaturized specimens of φ3 mm TEM disk and 10 mm 2 coupon were performed for six kinds of ferritic steels of F-82, F-82H, HT-9, JFMS, 2.25-1Mo and SQV2A. It was shown that the temperature dependence of SP fracture energies with scatter in miniaturized testing can give reliable information on the DBTT by use of the statistical analysis based on the Weibull distribution. A good correlation between the DBTT of the SP tests and that of the standard CVN test has been obtained for the various nuclear ferritic steels. The SP test was performed for cryogenic austenitic steels as a way of evaluating elastic-plastic fracture toughness, J IC , on the basis of a universal empirical relationship between J IC and SP equivalent fracture strain, ε-bar qf . The SP testing using the neutron irradiated specimens of 2.25Cr-1Mo, F-82, F-82H and HT-9 steels was successfully applied and presented the neutron radiation induced changes on the DBTT, fracture toughness and tensile properties. (author)

  17. [Reversed-phase high-performance liquid chromatograph--application to serum aluminium monitoring].

    Science.gov (United States)

    Hoshino, H; Kaneko, E

    1996-01-01

    High-Performance Liquid Chromatography (HPLC) with the reversed-phase partition mode separation (including ion-pair one) towards metal chelate compounds prepared in an off-line fashion (precolumn chelation) is most versatile in terms of high sensitivity with base-line flatness, unique selectivity and cost effectiveness. The extraordinary toughness to the complicated matrices encountered in clinical testing is exemplified by the successful application to the aluminium monitoring of human serum samples. The A1 chelate with 2,2'-dihydroxyazobenzene is efficiently chromatographed on a LiChroCART RP-18 column using an aqueous methanol eluent (63.6 wt%) containing tetrabutylammonium bromide as an ion-pair agent. The serum concentration level of A1 down to 6 micrograms dm-3 is readily monitored without influences from iron, chyle and haemolysis.

  18. Cohesive zone modelling of wafer bonding and fracture: effect of patterning and toughness variations

    Science.gov (United States)

    Kubair, D. V.; Spearing, S. M.

    2006-03-01

    Direct wafer bonding has increasingly become popular in the manufacture of microelectromechanical systems and semiconductor microelectronics components. The success of the bonding process is controlled by variables such as wafer flatness and surface preparation. In order to understand the effects of these variables, spontaneous planar crack propagation simulations were performed using the spectral scheme in conjunction with a cohesive zone model. The fracture-toughness on the bond interface is varied to simulate the effect of surface roughness (nanotopography) and patterning. Our analysis indicated that the energetics of crack propagation is sensitive to the local surface property variations. The patterned wafers are tougher (well bonded) than the unpatterned ones of the same average fracture-toughness.

  19. Fracture toughness behavior and its analysis on nuclear pressure vessel steels

    Energy Technology Data Exchange (ETDEWEB)

    Iwadate, Tadao; Tanaka, Yasuhiko; Ono, Shin-ichi; Tsukada, Hisashi [Japan Steel Works Ltd., Muroran, Hokkaido. Muroran Plant

    1983-02-01

    A drop weight J sub(Id) testing machine has been developed successfully, by which the multiple specimen J resistance curve test technique can be applied to measure the fracture toughness. In this study, the use of a small size round compact tension (RCT) specimen for measuring the fracture toughness J sub(Ic) or J sub(Id) of the nuclear pressure vessel steels is recommended and confirmed for the surveillance tests. The static and dynamic fracture toughness of ASTM A508 C 1.2, A508 C 1.3 and A533 Gr.B C 1.1 steels in the wide range of temperature including the upper shelf have been measured and their behavior has been analysed. The fracture toughness behavior under various strain rates and in a wide temperature range can be explained by the behavior of stretched zone formation preceding the crack initiation. The scatter of K sub(J) values in the transition range is caused by the amount of crack extension contained in the specimens. In this paper, the method to obtain the fracture toughness equivalent to the K sub(Ic) from the K sub(J) value is also presented.

  20. The crack layer approach to toughness characterization in steel

    Science.gov (United States)

    Bessendorff, M.; Chudnovsky, A.

    1986-01-01

    In a study of the laws of crack propagation and toughness characterization, it is feasible to employ two alternative approaches, including the fracture mechanics approach and the material science approach. The crack layer (CL) theory discussed by Khandogin and Chudnovsky (1978) and Chudnovsky (1980) considers the crack together with the surrounding defects as one system which has several degrees of freedom. It is pointed out that the CL theory defines the relationship between the parameters of fracture mechanics and the characteristics of microstructural changes which are the subject of material science. Experiments are described, taking into account a toughness characterization test and microscopic studies. Attention is given to a phenomenological study of toughness characterization, the morphology of crack layer, and the evaluation of energy stored in the dislocation network.

  1. Nanofiber reinforcement of a geopolymer matrix for improved composite materials mechanical performance

    Science.gov (United States)

    Rahman, AKM Samsur

    Geopolymers have the potential to cross the process performance gap between polymer matrix and ceramic matrix composites (CMC), enabling high temperature capable composites that are manufactured at relatively low temperatures. Unfortunately, the inherently low toughness of these geopolymers limits the performance of the resulting fiber reinforced geopolymer matrix composites. Toughness improvements in composites can be addressed through the adjustments in the fiber/matrix interfacial strength and through the improvements in the inherent toughness of the constituent materials. This study investigates the potential to improve the inherent toughness of the geopolymer matrix material through the addition of nanofillers, by considering physical dimensions, mechanical properties, reinforcing capability and interfacial bond strength effects. A process optimization study was first undertaken to develop the ability to produce consistent, neat geopolymer samples, a critical precursor to producing nano-filled geopolymer for toughness evaluation. After that, single edge notched bend beam fracture toughness and un-notched beam flexural strength were evaluated for silicon carbide, alumina and carbon nanofillers reinforced geopolymer samples treated at various temperatures in reactive and inert environments. Toughness results of silicon carbide and carbon nanofillers reinforced geopolymers suggested that with the improved baseline properties, high aspect ratio nanofillers with high interfacial bond strength are the most capable in further improving the toughness of geopolymers. Among the high aspect ratio nanofillers i.e. nanofibers, 2vol% silicon carbide whicker (SCW) showed the highest improvement in fracture toughness and flexural strength of ~164% & ~185%, respectively. After heat treatment at 650 °C, SCW reinforcement was found to be effective, with little reduction in the performance, while the performance of alumina nanofiber (ANF) reinforced geopolymer significantly

  2. Improving Fracture Toughness of Epoxy Nanocomposites by Silica Nanoparticles

    Directory of Open Access Journals (Sweden)

    Seyed Reza Akherati Sany

    2017-04-01

    Full Text Available An epoxy resin was modified by silica nanoparticles and cured with an anhydride. The particles with different batches of 12, 20, and 40 nm sizes were each distributed into the epoxy resin ultrasonically. Electron microscopy images showed that the silica particles were well dispersed throughout the resin. Tensile test results showed that Young’s modulus and tensile strength increased with the volume fraction and surface area of the silica particles. The simultaneous use of two average sizes of 20 and 40 nm diameter silica particles still increased these mechanical properties but other combinations of silica particles were unsuccessful. A three-point bending test on each pre-cracked specimen was performed to measure the mode I fracture toughness energy. The fracture energy increased from 283 J/m2 for the unmodified epoxy to about 740 J/m2 for the epoxy with 4.5 wt% of 12 nm diameter silica nanoparticles. The fracture energy of smaller particles was greater because of their higher surface to volume ratio. The fracture energy results showed also that the combined nanoparticles has a synergic effect on the fracture toughness of nanocomposites. Simultaneous use of 10 and 20 nm particles increased the fracture energy to about 770 J/m2. Finally, crack-opening displacement was calculated and found to be in the range of several micrometers which was much larger than the sizes of particles studied. Thus, the toughening mechanisms of crack pinning and crack deflection have a negligible effect on improvement of toughness, nevertheless, the plastic deformation and plastic void growth are dominant mechanisms in epoxy toughening by nanoparticles.

  3. Fracture toughness of China low activation martensitic (CLAM) steel at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Li, Kunfeng [University of Science and Technology of China, Hefei, Anhui 230027 (China); Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Liu, Shaojun, E-mail: shaojun.liu@fds.org.cn [Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Huang, Qunying [University of Science and Technology of China, Hefei, Anhui 230027 (China); Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Xu, Gang; Jiang, Siben [Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui 230031 (China)

    2014-04-15

    Highlights: • The fracture toughness of CLAM steel at room temperature is 417.9 kJ/m{sup 2} measured by unloading compliance method according to the ASTM E1820-11. • The fracture toughness of CLAM steel at room temperature can be calculated on the basis of the fractal dimensions measured under plane strain conditions. The calculated result and relative error for this experiment are 454.6 kJ/m{sup 2} and 8.78% respectively. • The calculation method could be used to estimate the fracture toughness of materials with analysis of the fracture surface. - Abstract: The fracture toughness (J{sub IC}) of China low activation martensitic (CLAM) steel was tested at room temperature through the compact tension specimen, the result is 417.9 kJ/m{sup 2}, which is similar to the JLF-1 at same experimental conditions. The microstructural observation of the fracture surface shows that the fracture mode is a typical ductile fracture. Meanwhile, the fracture toughness is also calculated on the basis of the fractal dimension and the calculated result is 454.6 kJ/m{sup 2}, which is consistent well with the experimental result. This method could be used to estimate the fracture toughness of materials by analyzing of the fracture surface.

  4. Optimization design of strong and tough nacreous nanocomposites through tuning characteristic lengths

    Science.gov (United States)

    Ni, Yong; Song, Zhaoqiang; Jiang, Hongyuan; Yu, Shu-Hong; He, Linghui

    2015-08-01

    How nacreous nanocomposites with optimal combinations of stiffness, strength and toughness depend on constituent property and microstructure parameters is studied using a nonlinear shear-lag model. We show that the interfacial elasto-plasticity and the overlapping length between bricks dependent on the brick size and brick staggering mode significantly affect the nonuniformity of the shear stress, the stress-transfer efficiency and thus the failure path. There are two characteristic lengths at which the strength and toughness are optimized respectively. Simultaneous optimization of the strength and toughness is achieved by matching these lengths as close as possible in the nacreous nanocomposite with regularly staggered brick-and-mortar (BM) structure where simultaneous uniform failures of the brick and interface occur. In the randomly staggered BM structure, as the overlapping length is distributed, the nacreous nanocomposite turns the simultaneous uniform failure into progressive interface or brick failure with moderate decrease of the strength and toughness. Specifically there is a parametric range at which the strength and toughness are insensitive to the brick staggering randomness. The obtained results propose a parametric selection guideline based on the length matching for rational design of nacreous nanocomposites. Such guideline explains why nacre is strong and tough while most artificial nacreous nanocomposites aere not.

  5. Feasibility analysis of ultra high performance concrete for prestressed concrete bridge applications.

    Science.gov (United States)

    2010-07-01

    UHPC is an emerging material technology in which concrete develops very high : compressive strengths and exhibits improved tensile strength and toughness. A : comprehensive literature and historical application review was completed to determine the :...

  6. Standard test method for plane-strain (Chevron-Notch) fracture toughness of metallic materials

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1997-01-01

    1.1 This test method covers the determination of plane-strain (chevron-notch) fracture toughnesses, KIv or KIvM, of metallic materials. Fracture toughness by this method is relative to a slowly advancing steady state crack initiated at a chevron-shaped notch, and propagating in a chevron-shaped ligament (Fig. 1). Some metallic materials, when tested by this method, exhibit a sporadic crack growth in which the crack front remains nearly stationary until a critical load is reached. The crack then becomes unstable and suddenly advances at high speed to the next arrest point. For these materials, this test method covers the determination of the plane-strain fracture toughness, KIvj or KIvM, relative to the crack at the points of instability. Note 1—One difference between this test method and Test Method E 399 (which measures KIc) is that Test Method E 399 centers attention on the start of crack extension from a fatigue precrack. This test method makes use of either a steady state slowly propagating crack, or a...

  7. Effect of Bainitic Microstructure on Ballistic Performance of Armour Steel Weld Metal Using Developed High Ni-Coated Electrode

    Science.gov (United States)

    Pramanick, A. K.; Das, H.; Reddy, G. M.; Ghosh, M.; Nandy, S.; Pal, T. K.

    2018-05-01

    Welding of armour steel has gained significant importance during the past few years as recent civilian and military requirements demand weld metal properties matching with base metal having good ballistic performance along with high strength and toughness at - 40 °C as per specification. The challenge of armour steel welding therefore lies in controlling the weld metal composition which is strongly dependent on welding electrode/consumables, resulting in desired weld microstructure consisting of lower bainite along with retained austenite. The performance of butt-welded armour steel joints produced by the developed electrodes was evaluated using tensile testing, ballistic testing, impact toughness at room temperature and subzero temperature. Microstructures of weld metals are exclusively characterized by x-ray diffraction technique, scanning electron microscope and transmission electron microscopy with selected area diffraction pattern. Experimental results show that weld metal with relatively lower carbon, higher manganese and lower nickel content was attributed to lower bainite with film type of retained austenite may be considered as a most covetable microstructure for armour steel weld metal.

  8. Effect of Bainitic Microstructure on Ballistic Performance of Armour Steel Weld Metal Using Developed High Ni-Coated Electrode

    Science.gov (United States)

    Pramanick, A. K.; Das, H.; Reddy, G. M.; Ghosh, M.; Nandy, S.; Pal, T. K.

    2018-04-01

    Welding of armour steel has gained significant importance during the past few years as recent civilian and military requirements demand weld metal properties matching with base metal having good ballistic performance along with high strength and toughness at - 40 °C as per specification. The challenge of armour steel welding therefore lies in controlling the weld metal composition which is strongly dependent on welding electrode/consumables, resulting in desired weld microstructure consisting of lower bainite along with retained austenite. The performance of butt-welded armour steel joints produced by the developed electrodes was evaluated using tensile testing, ballistic testing, impact toughness at room temperature and subzero temperature. Microstructures of weld metals are exclusively characterized by x-ray diffraction technique, scanning electron microscope and transmission electron microscopy with selected area diffraction pattern. Experimental results show that weld metal with relatively lower carbon, higher manganese and lower nickel content was attributed to lower bainite with film type of retained austenite may be considered as a most covetable microstructure for armour steel weld metal.

  9. The effect of specimen and flaw dimensions on fracture toughness

    Energy Technology Data Exchange (ETDEWEB)

    Nevalainen, M.J. [VTT Manufacturing Technology, Espoo (Finland)

    1997-06-01

    The effect of the specimen size and geometry on fracture toughness has been investigated both by experimental tests and computational analyses. The methods for constraint description, namely T-stress, Q-parameter and Small-Scale Yielding Correction (SSYC) have been compared and applied for various geometries. A statistical treatment for the specimen thickness effect on cleavage fracture toughness has been investigated. Elliptical surface cracks were compared with straight-thickness cracks and a method for crack shape correction was presented. Based on the results, the differences in apparent fracture toughness values obtained from various specimen configurations can be better understood and taken into account. 64 refs. The thesis includes also four previous publications by author.

  10. Fracture toughness of epoxy/multi-walled carbon nanotube nano-composites under bending and shear loading conditions

    International Nuclear Information System (INIS)

    Ayatollahi, M.R.; Shadlou, S.; Shokrieh, M.M.

    2011-01-01

    Research highlights: → Mode I and mode II fracture tests were conducted on epoxy/MWCNT nano-composites. → Addition of MWCNT to epoxy increased both K Ic and K IIc of nano-composites. → The improvement in K IIc was more pronounced than in K Ic . → Mode I and mode II fracture surfaces were studied by scanning electron microscopy. -- Abstract: The effects of multi-walled carbon nanotubes (MWCNTs) on the mechanical properties of epoxy/MWCNT nano-composites were studied with emphasis on fracture toughness under bending and shear loading conditions. Several finite element (FE) analyses were performed to determine appropriate shear loading boundary conditions for a single-edge notch bend specimen (SENB) and an equation was derived for calculating the shear loading fracture toughness from the fracture load. It was seen that the increase in fracture toughness of nano-composite depends on the type of loading. That is to say, the presence of MWCNTs had a greater effect on fracture toughness of nano-composites under shear loading compared with normal loading. To study the fracture mechanisms, several scanning electron microscopy (SEM) pictures were taken from the fracture surfaces. A correlation was found between the characteristics of fracture surface and the mechanical behaviors observed in the fracture tests.

  11. An overview of EXTOOL: An analysis tool for V-TOUGH and NUFT

    International Nuclear Information System (INIS)

    Daveler, S.

    1995-08-01

    Several post-processors have been used in connection with V-TOUGH. Initially, a sequence of utilities were used to extract and plot V-TOUGH information. This changed in 1991 as a new post-processor, EXTOOL, was developed. Currently, EXTOOL, is the main post-processor for the modeling codes V-TOUGH and NUFT. In the following sections, a history of V-TOUGH post-processing is discussed along with an overview of EXTOOL. This overview describes some of Extool's capabilities and suggests reasons for using this code instead of another postprocessor. More detailed information on EXTOOL can be found in the Extool User's Manual and the Extool Programmer's Guide. Both these manuals are drafts, and can be requested by sending email to daveler2 at sign llnl.gov

  12. The Relationship between Psychological Well-being and Mental Toughness Among Elders: Mediator Role of Physical Activity

    Directory of Open Access Journals (Sweden)

    Mahdi Sohrabi

    2017-03-01

    Conclusion In accordance with the results of this study, the elders should be encouraged to perform physical activities, which in turn improves aspects of mental health such as psychological well-being and mental toughness

  13. Macroscale and microscale fracture toughness of microporous sintered Ag for applications in power electronic devices

    International Nuclear Information System (INIS)

    Chen, Chuantong; Nagao, Shijo; Suganuma, Katsuaki; Jiu, Jinting; Sugahara, Tohru; Zhang, Hao; Iwashige, Tomohito; Sugiura, Kazuhiko; Tsuruta, Kazuhiro

    2017-01-01

    The application of microporous sintered silver (Ag) as a bonding material to replace conventional die-bonding materials in power electronic devices has attracted considerable interest. Characterization of the mechanical properties of microporous Ag will enable its use in applications such as lead-free solder electronics and provide a fundamental understanding of its design principles. However, the material typically suffers from thermal and mechanical stress during its production fabrication, and service. In this work, we have studied the effect of microporous Ag specimen size on fracture toughness from the microscale to the macroscale. A focused ion beam was used to fabricate 20-, 10- and 5-μm-wide microscale specimens, which were of the same order of magnitude as the pore networks in the microporous Ag. Micro-cantilever bending tests revealed that fracture toughness decreased as the specimen size decreased. Conventional middle-cracked tensile tests were performed to determine the fracture toughness of the macroscale specimens. The microscale and macroscale fracture toughness results showed a clear size effect, which is discussed in terms of both the deformation behavior of crack tip and the influence of pore networks within Ag with different specimen sizes. Finite element model simulations showed that stress at the crack tip increased as the specimen size increased, which led to larger plastic deformation and more energy being consumed when the specimen fractured.

  14. Foundation of the Outstanding Toughness in Biomimetic and Natural Spider Silk.

    Science.gov (United States)

    Anton, Arthur Markus; Heidebrecht, Aniela; Mahmood, Nasir; Beiner, Mario; Scheibel, Thomas; Kremer, Friedrich

    2017-12-11

    Spider dragline silk is distinguished through the highest toughness of all natural as well as artificial fiber materials. To unravel the toughness's molecular foundation and to enable manufacturing biomimetic analogues, we investigated the morphological and functional structure of recombinant fibers, which exhibit toughness similar to that of the natural template, on the molecular scale by means of vibrational spectroscopy and on the mesoscale by X-ray scattering. Whereas the former was used to identify protein secondary structures and their alignment in the natural as well as artificial silks, the latter revealed nanometer-sized crystallites on the higher structural level. Furthermore, a spectral red shift of a crystal-specific absorption band demonstrated that macroscopically applied stress is directly transferred to the molecular scale, where it is finally dissipated. Concerning this feature, both the natural as well as the biomimetic fibers are almost indistinguishable, giving rise to the toughness of both fiber materials.

  15. Fracture toughness evaluation in the transition region of reactor pressure vessel steel

    International Nuclear Information System (INIS)

    Onizawa, K.; Suzuki, M.

    1995-01-01

    The fracture toughness (K jc and Jc) values at the cleavage fracture initiation in the transition region of a RPV steel were investigated using mainly precracked Charpy specimens. A conventional statistical approach and a fractographic study were applied to analyze the scatter of the fracture toughness values from precracked Charpy specimens. The material used was an ASTM A533B class 1 steel, which was designated as an IAEA correlation monitor material, JRQ. A lower bound transition curve of the fracture toughness for unirradiated condition was determined by the 5% confidence limit from the Weibull and fractographic analyses. The lower bound transition curve after irradiation was evaluated based on the statistics of unirradiated specimens. The results indicated that the shift of the fracture toughness transition curbe were somewhat larger than the Charpy 41J transition temperature. The parameters to determine the lower bound toughness such as the Weibull slope and the amount of ductile crack growth are discussed. The results are also compared with a model based on weakest link theory. (author). 12 refs, 12 figs, 5 tabs

  16. A Novel Procedure for Prediction of Mixed Mode I/II in Fracture Toughness of Laminate Composites

    Directory of Open Access Journals (Sweden)

    M. Mahmood Shokrieh

    2014-06-01

    Full Text Available Delamination is one of the important modes of failure in laminated composite materials. In this respect, the mixed mode I/II fracture is the most major mode of delamination incidence in laminated composite. In the present research, a relation between the fracture toughness of double cantilever beam (DCB and asymmetric double cantilever beam (ADCB specimens is presented. The DCB and ADCB samples are used for measuring the mode I and mixed mode I/II fracture toughness (G of laminated composite materials, respectively. By considering the diversity of the stacking sequence of lay-ups, the test performance on all different types of lay-ups in order to measure the fracture toughness of laminated composites is a tedious, costly and time consuming task. The purpose of deriving this relation is to estimate the value of the strain energy release rate of laminated composite ADCB specimens by testing a unidirectional DCB. To develop this relationship, the geometry of DCB and ADCB specimens are considered to obtain fracture toughness of multi-directional laminate composites of ADCB samples with arbitrary ply sequence which may be used for design purposes. The procedure presented here reduces the calculation costs of the finite element modeling and its corresponding test significantly. The results obtained by this method are compared with those of experimental and numerical methods. It is shown that the fracture toughness of multi-directional lay-ups can be predicted by measuring the unidirectional ply with an error less than 10% demonstrating the accuracy of the procedure developed in the present research.

  17. Phase stability and fracture toughness of t' ZrO2 stabilised with MO1.5 (M=Yb and Gd) for thermal barrier application

    International Nuclear Information System (INIS)

    Loganathan, Archana; Gandhi, Ashutosh S.

    2010-01-01

    Thermal Barrier coatings (TBC's) protect the gas turbine blades at high temperature exposure. The t' phase is metastable and slowly transforms to the high-temperature equilibrium state consisting of tetragonal (t) and cubic (c) during high temperature exposure. Nanometric grain size also influences the fracture toughness and t' stability. A comparative study of the phase stability and fracture toughness evolution of Yb and Gd stabilized zirconia with composition 8 mol%MO 1.5 . The t' ZrO 2 -8mol% MO 1.5 (M = Yb and Gd) were prepared by co-precipitation method with crystallite size ∼ 20nm. Spark plasma sintering at 1250 deg C for 10 min was carried out to produce compacts with ∼ 96% relative density for fracture toughness measurements. The dense compacts were heat treated at 1250 deg C upto 192h. XRD studies revealed the partitioning of t' to t+c. No spontaneous monoclinic phase formed during cooling, except after 192h exposure. The fracture toughness of the sintered pellets with various time intervals of thermal exposure was measured. The results were analysed in terms of the effect of phase constitution on fracture toughness. The role of ferroelastic toughening in these materials was explored. (author)

  18. Development of the present reference fracture toughness curves in the ASME nuclear code

    International Nuclear Information System (INIS)

    Yukawa, S.; Merkle, J.G.

    1984-01-01

    Since the early 1970's, the Sections of the ASME Boiler and Pressure Vessel Code concerned with nuclear power plant components have included fracture mechanics procedures to analyze the effects of postulated or detected flaws. These procedures are contained in Appendix G of Section III and in Appendix A of Section XI of the Code. Specifically, Appendix G procedures are concerned with designing for protection against nonductile failures while Appendix A procedures are for evaluating the disposition of flaws detected during in-service inspection. An important element of the procedures is the inclusion of recommended material fracture toughness values. This paper describes the origin and development of these recommended fracture toughness values. Since these values appear in the Code in a graphical format, the values are often referred to as reference toughness curves. In the context of Code terminology, reference toughness means the allowable values of fracture toughness for the materials of concern that can be used in conjunction with the analytical procedures of Appendices G and A. The paper discusses the basis and rationale underlying the original formulation of these reference toughness curves and the modifications incorporated into them in the course of their adoption into the Code

  19. Visible Light Photoinitiator for 3D-Printing of Tough Methacrylate Resins

    Directory of Open Access Journals (Sweden)

    Bernhard Steyrer

    2017-12-01

    Full Text Available Lithography-based additive manufacturing was introduced in the 1980s, and is still the method of choice for printing accurate plastic parts with high surface quality. Recent progress in this field has made tough photopolymer resins and cheap LED light engines available. This study presents the influence of photoinitiator selection and post-processing on the thermomechanical properties of various tough photopolymers. The influence of three photoinitiators (Ivocerin, BAPO, and TPO-L on the double-bond conversion and mechanical properties was investigated by mid infrared spectroscopy, dynamic mechanical analysis and tensile tests. It was found that 1.18 wt % TPO-L would provide the best overall results in terms of double-bond conversion and mechanical properties. A correlation between double-bond conversion, yield strength, and glass transition temperature was found. Elongation at break remained high after post-curing at about 80–100%, and was not influenced by higher photoinitiator concentration. Finally, functional parts with 41 MPa tensile strength, 82% elongation at break, and 112 °C glass transition temperature were printed on a 405 nm DLP (digital light processing printer.

  20. Renewable Pentablock Copolymers Containing Bulky Natural Rosin for Tough Bioplastics

    Science.gov (United States)

    Rahman, Md Anisur; Ganewatta, Mitra S.; Lokupitiya, Hasala N.; Liang, Yuan; Stefik, Morgan; Tang, Chuanbing

    Renewable polymers have received significant attention due to environmental concerns on petrochemical counterparts. One of the most abundant natural biomass is resin acids. However, most polymers derived from resin acids are low molecular weight and brittle because of the high chain entanglement molecular weight resulted from the bulky hydrophenanthrene pendant group. It is well established that the brittleness can be overcome by synthesizing multi-block copolymers with low entanglement molecular weight components. We investigated the effects of chain architecture and microdomain orientation on mechanical properties of both tri and pentablock copolymers. We synthesized rosin-containing A-B-A-B-A type pentablock and A-B-A type triblock copolymers to improve their mechanical properties. Pentablock copolymers showed higher strength and better toughness as compared to triblock copolymers, both superior to homopolymers. The greater toughness of pentablock copolymers is due to the presence of the rosin based midblock chains that act as bridging chains between two polynorbornene blocks.

  1. A study on the fracture toughness of heavy section steel plates and forgings for nuclear pressure vessels produced in Japan, 2

    International Nuclear Information System (INIS)

    Sakai, Yuzuru; Ogura, Nobukazu; Takahashi, Isao; Miya, Kenzo; Ando, Yoshio.

    1984-01-01

    In this paper, the main results of a series of tests carried out by the Atomic Energy Research Committee, the Japan Welding Engineering Society, for six years for the purpose of evaluating the fracture toughness and strength of superthick steel materials for nuclear reactors made in Japan are reported. In this research, as the fracture toughness test, three kinds of static, dynamic and crack propagation stop tests were carried out. Not only parent metals but also welded parts were evaluated, and numerous data have been accumulated. The fracture toughness of structural materials generally depends on test temperature, and forms three regions of lower shelf, transition and upper shelf from low temperature side toward high temperature side. It is desired to establish the effective method to determine fracture toughness over wide temperature range with small test pieces, and as its promising method, J(IC) fracture toughness test based on elasto-plastic fracture mechanics is carried out. The toughness in lower shelf and transition regions was clarified by K(IC) test, and that in upper shelf region was evaluated by J(IC) test. The methods of test and analysis, and the results are reported. (Kako, I.)

  2. Fracture toughness of the IEA heat of F82H ferritic/martensitic stainless steel as a function of loading mode

    Energy Technology Data Exchange (ETDEWEB)

    Li, Huaxin; Gelles, D.S. [Pacific Northwest Labs., Richland, WA (United States); Hirth, J.P. [Washington State Univ., Pullman, WA (United States)] [and others

    1997-04-01

    Mode I and mixed-mode I/III fracture toughness tests were performed for the IEA heat of the reduced activation ferritic/martensitic stainless steel F82H at ambient temperature in order to provide comparison with previous measurements on a small heat given a different heat treatment. The results showed that heat to heat variations and heat treatment had negligible consequences on Mode I fracture toughness, but behavior during mixed-mode testing showed unexpected instabilities.

  3. Fracture toughness of A533B. Part 2. Review of data pertinent to upper shelf temperatures

    International Nuclear Information System (INIS)

    Druce, S.G.; Eyre, B.L.; Belcher, W.P.A.

    1978-08-01

    This report is the second in a series of three examining the state of the art of elastoplastic fracture mechanics as applied to A533B pressure vessel steel in the upper shelf temperature regime. Part II presents a review of fracture toughness data for A533B Class 1 plate tested in the longitudinal (RW) orientation. Data from USA, UK and Scandinavian sources published prior to September 1976 has been included. It is concluded that previous studies using a maximum load criterion have over-estimated the initiation toughness in the upper shelf regime. Results derived from J integral tests now show the mean toughness at 275 0 C to vary between 141 ksi sq. root in and 154 ksi sq. root in depending on the exact analytical procedure used. Limited statistical analysis of the results obtained using several heats of material suggest that standard deviation of the scatter of results is approximately 11% of the mean value. Recommendations for future work to improve our understanding of the fracture properties of A533B and similar medium strength high toughness materials, and their application to large structures, are presented. (author)

  4. Investigation on Microstructure and Impact Toughness of Different Zones in Duplex Stainless Steel Welding Joint

    Science.gov (United States)

    Zhang, Zhiqiang; Jing, Hongyang; Xu, Lianyong; Han, Yongdian; Li, Guolu; Zhao, Lei

    2017-01-01

    This paper investigated on microstructure and impact toughness of different zones in duplex stainless steel welding joint. High-temperature heat-affected zone (HTHAZ) contained coarse ferrite grains and secondary precipitates such as secondary austenite, Cr2N, and sigma. Intergranular secondary austenite was prone to precipitation in low-temperature heat-affected zone (LTHAZ). Both in weld metal (WM) and in HTHAZ, the austenite consisted of different primary and secondary austenite. The ferrite grains in base metal (BM) presented typical rolling texture, while the austenite grains showed random orientation. Both in the HTHAZ and in the LTHAZ, the ferrite grains maintained same texture as the ferrite in the BM. The secondary austenite had higher Ni but lower Cr and Mo than the primary austenite. Furthermore, the WM exhibited the highest toughness because of sufficient ductile austenite and unapparent ferrite texture. The HTHAZ had the lowest toughness because of insufficient austenite formation in addition to brittle sigma and Cr2N precipitation. The LTHAZ toughness was higher than the BM due to secondary austenite precipitation. In addition, the WM fracture was dominated by the dimple, while the cleavage was main fracture mode of the HTHAZ. Both BM and LTHAZ exhibited a mixed fracture mode of the dimple and quasi-cleavage.

  5. The fracture toughness and DBTT of MoB particle-reinforced MoSi2 composites

    International Nuclear Information System (INIS)

    Xiong Zhi; Wang Gang; Jiang Wan

    2005-01-01

    The room temperature fracture toughness and the high temperature DBTT of MoB particle-reinforced MoSi 2 composites were investigated using Vickers indentation technique and MSP testing method, respectively. Modified small punch (MSP) test is a method for evaluation of mechanical properties using very small specimens, and it's appropriate for the determination of strength and DBTT. It was found that the approximate fracture toughness of the composite is 1.3 times that of monolithic MoSi 2 , and its DBTT is 100 C higher than that of monolithic MoSi 2 materials. Cracks deflection is a probable mechanism responsible for this behavior. (orig.)

  6. Method to increase the toughness of aluminum-lithium alloys at cryogenic temperatures

    Science.gov (United States)

    Sankaran, Krishnan K. (Inventor); Sova, Brian J. (Inventor); Babel, Henry W. (Inventor)

    2006-01-01

    A method to increase the toughness of the aluminum-lithium alloy C458 and similar alloys at cryogenic temperatures above their room temperature toughness is provided. Increasing the cryogenic toughness of the aluminum-lithium alloy C458 allows the use of alloy C458 for cryogenic tanks, for example for launch vehicles in the aerospace industry. A two-step aging treatment for alloy C458 is provided. A specific set of times and temperatures to age the aluminum-lithium alloy C458 to T8 temper is disclosed that results in a higher toughness at cryogenic temperatures compared to room temperature. The disclosed two-step aging treatment for alloy 458 can be easily practiced in the manufacturing process, does not involve impractical heating rates or durations, and does not degrade other material properties.

  7. Stainless steel submerged arc weld fusion line toughness

    International Nuclear Information System (INIS)

    Rosenfield, A.R.; Held, P.R.; Wilkowski, G.M.

    1995-04-01

    This effort evaluated the fracture toughness of austenitic steel submerged-arc weld (SAW) fusion lines. The incentive was to explain why cracks grow into the fusion line in many pipe tests conducted with cracks initially centered in SAWS. The concern was that the fusion line may have a lower toughness than the SAW. It was found that the fusion line, Ji. was greater than the SAW toughness but much less than the base metal. Of greater importance may be that the crack growth resistance (JD-R) of the fusion line appeared to reach a steady-state value, while the SAW had a continually increasing JD-R curve. This explains why the cracks eventually turn to the fusion line in the pipe experiments. A method of incorporating these results would be to use the weld metal J-R curve up to the fusion-line steady-state J value. These results may be more important to LBB analyses than the ASME flaw evaluation procedures, since there is more crack growth with through-wall cracks in LBB analyses than for surface cracks in pipe flaw evaluations

  8. Effects of Rare Earth on the Microstructure and Impact Toughness of H13 Steel

    Directory of Open Access Journals (Sweden)

    Jinzhu Gao

    2015-03-01

    Full Text Available Studies of H13 steel suggest that under appropriate conditions, additions of rare-earth metals (REM can significantly enhance mechanical properties, such as impact toughness. This improvement is apparently due to the formation of finer and more dispersive RE inclusions and grain refinement after REM additions. In this present work, the microstructure evolution and mechanical properties of H13 steel with rare earth additions (0, 0.015, 0.025 and 0.1 wt.% were investigated. The grain size, inclusions and fracture morphology were systematically studied by means of optical microscopy (OM, scanning electron microscopy (SEM and transmission electron microscopy (TEM. The results indicate that REM addition of 0.015 wt.% can result in good improvement of performance compared to the REM additions of 0.025 wt.% and 0.1 wt.%. It is found that the impact toughness is significantly enhanced with the addition of 0.015% REM, which can be improved 90% from 10 J to 19 J. Such an addition of REM can result in a huge volume fraction of finer and more dispersive inclusions which are extremely good to toughness.

  9. Tough by name, tough by nature.

    Science.gov (United States)

    Baillie, Jonathan

    2015-04-01

    Few beds, one would imagine, could withstand three-quarters of a ton landing on them, but this was the challenge successfully met by a box bed from a furniture manufacturer for challenging behaviour environments, Tough Furniture, when, to reassure a customer that the bed could accommodate 30-stone patients, 13 of the company's staff jumped repeatedly on it to ensure that it would survive intact in a real-world setting. Such testing may seem extreme, but is vital, since much of the company's furniture is destined for environments where patients will abuse, and indeed attempt to destroy, components. As MD David Vesty explained to HEJ editor, Jonathan Baillie, when he visited the company's Shropshire headquarters, it is through manufacturing premium quality cabinet furniture that is both attractive and distinctly non-institutional, but will equally withstand the harshest use, that the company has ensured that its products can live up to the brand name.

  10. Correlation of microstructure and fracture toughness of advanced 9Cr/CrMoV dissimilarly welded joint

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Qian [Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Lu, Fenggui, E-mail: Lfg119@sjtu.edu.cn [Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Liu, Xia [Shanghai Turbine Plant of Shanghai Electric Power Generation Equipment Co. Ltd., Shanghai 200240 (China); Yang, Renjie [Shanghai Turbine Works Company, Shanghai 200240 (China); Cui, Haichao [Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Gao, Yulai, E-mail: ylgao@shu.edu.cn [State Key Laboratory of Advanced Special Steels, Shanghai University, Shanghai 200072 (China)

    2015-06-25

    In this paper, the fracture toughness and the related microstructure characteristics of dissimilarly welded joint manufactured by advanced 9Cr and CrMoV steels were systematically investigated. The dissimilarly welded joint was fabricated by narrow gap submerged arc welding (NG-SAW) applying multi-layer and multi-pass technique. Fracture toughness, as one of the most important property to assess the reliability of welded joint, was studied for different regions including CrMoV base metal (CrMoV-BM), heat affected zone (HAZ) of CrMoV side (CrMoV-HAZ), weld metal (WM), heat affected zone of 9Cr side (9Cr-HAZ) and 9Cr base metal (9Cr-BM). It was found that the fracture toughness of CrMoV-BM, CrMoV-HAZ and WM was better than that of 9Cr-HAZ and 9Cr-BM. In order to illustrate these results, the microstructure of the whole welded joint was observed by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM) detailedly. It was found that the fine high-temperature tempered martensite and bainite in WM, CrMoV-BM and CrMoV-HAZ contribute to the higher fracture toughness, while lower fracture toughness for 9Cr-BM and HAZ was caused by coarse tempered lath-martensite. Furthermore, the fracture morphology showed that ductile fracture occurred in WM and CrMoV side, while brittle fracture appeared in BM and HAZ of 9Cr side.

  11. Fracture toughness of a nanoscale WC-Co tool steel

    International Nuclear Information System (INIS)

    Densley, J.M.; Hirth, J.P.

    1997-01-01

    Tungsten carbide tool steels, comprising WC particles with 6.7--25wt% Co distributed in the interparticle regions as a quasi-continuous binder phase, can be considered as WC-Co composites. The fracture toughness of such WC-Co composites is dependent on the volume fraction, contiguity and thickness of the cobalt binder, and the size of the tungsten carbide grains. Research has shown that the ductile binder undergoes nearly all the plastic deformation during fracture, which provides the primary energy consuming process that enhances fracture resistance. Recent manufacturing developments have given rise to the production of a WC-6.7wt% Co cermet having an average WC grain size of 70 nm, with a corresponding binder mean thickness, h, of 9 nm calculated from d = h(1-V f )/V f where d = 70 nm and V f = 0.114. This composite has shown a higher wear resistance than that of conventional cermets in proportion to their hardness. Such improvement has been attributed to the difficulty in forming dislocations in the very small grains. There are also indications that the Co binder in the nanoscale cermet contains higher contents of dissolved W and C than for conventional scale cermets. Because plastic deformation is initially confined to the binder phase, it was of interest to perform mode 1 and mixed mode toughness tests on the nanoscale cermet to determine whether flow localization influenced mixed mode toughness as in bulk materials. Two generations of this cermet were provided by Rogers Tool Works. The first generation, A, had lower binder contiguity, with occasional agglomerations of WC grains. The second generation, B, was cleaner, with the cobalt binder more uniformly separating the WC grains

  12. Fracture toughness of borides formed on boronized ductile iron

    International Nuclear Information System (INIS)

    Sen, Ugur; Sen, Saduman; Koksal, Sakip; Yilmaz, Fevzi

    2005-01-01

    In this study, fracture toughness properties of boronized ductile iron were investigated. Boronizing was realized in a salt bath consisting of borax, boric acid and ferro-silicon. Boronizing heat treatment was carried out between 850 and 950 deg. C under the atmospheric pressure for 2-8 h. Borides e.g. FeB, Fe 2 B formed on ductile iron was verified by X-ray diffraction (XRD) analysis, SEM and optical microscope. Experimental results revealed that longer boronizing time resulted in thicker boride layers. Optical microscope cross-sectional observation of borided layers showed dentricular morphology. Both microhardness and fracture toughness of borided surfaces were measured via Vickers indenter. The harnesses of borides formed on the ductile iron were in the range of 1160-2140 HV 0.1 and fracture toughness were in the range of 2.19-4.47 MPa m 1/2 depending on boronizing time and temperature

  13. Next generation self-shielded flux cored electrode with improved toughness for off shore oil well platform structures

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Daya; Soltis, Patrick; Narayanan, Badri; Quintana, Marie; Fox, Jeff [The Lincoln Electric Company (United States)

    2005-07-01

    Self-shielded flux cored arc welding electrodes (FCAW-S) are ideal for outdoor applications, particularly open fabrication yards where high winds are a possibility. Development work was carried out on a FCAW-S electrode for welding 70 and 80 ksi yield strength base materials with a required minimum average Charpy V-Notch (CVN) absorbed energy value of 35 ft-lb at -40 deg F in the weld metal. The effect of Al, Mg, Ti, and Zr on CVN toughness was evaluated by running a Design of Experiments approach to systematically vary the levels of these components in the electrode fill and, in turn, the weld metal. These electrodes were used to weld simulated pipe joints. Over the range of compositions tested, 0.05% Ti in the weld metal was found to be optimum for CVN toughness. Ti also had a beneficial effect on the usable voltage range. Simulated offshore joints were welded to evaluate the effect of base metal dilution, heat input, and welding procedure on the toughness of weld metal. CVN toughness was again measured at -40 deg F on samples taken from the root and the cap pass regions. The root pass impact toughness showed strong dependence on the base metal dilution and the heat input used to weld the root and fill passes. (author)

  14. Fracture toughness in nuclear waste glasses and ceramics: environmental and radiation effects

    International Nuclear Information System (INIS)

    Weber, W.J.; Matzke, H.J.

    1986-03-01

    The effects of atmospheric moisture and radiation damage on fracture properties of nuclear waste glasses and ceramics was investigated by indentation techniques. In nuclear waste glasses, atmospheric moisture has no measurable effect on hardness but decreases the fracture toughness; radiation damage, on the other hand, decreased the hardness and increased the fracture toughness. In nuclear ceramics, self-radiation damage from alpha decay decreased the hardness and elastic modules; the fracture toughness increased with dose to a broad maximum and then decreased slightly with further increases in dose

  15. Dynamic fracture toughness testing of structural steels

    International Nuclear Information System (INIS)

    Debel, C.P.

    1978-01-01

    Two candidate test methods aimed at producing materials properties of interest in connection with crack arrest assessments are currently under evaluation. These methods and the significance of the results are described. The quasi-static as well as the dynamic fracture toughness of a plain C-Mn steel in the as-quenched and tempered condition have been examined at temperatures between -115 0 C and the ambient temperature. Wedge-loaded duplex DCB-specimens were used in dynamic tests. The crack extension velocity was measured using a surface deposited grid and a registration circuit based on TTL-electronics. The toughness transition-temperature at quasi-static loading rate is found to be low; but during dynamic crack-extension a substantial shift of the transition-region to higher temperatures is produced, and fast fracture was obtained even at ambient temperature. Even though the dynamic fracture toughness Ksub(ID) increases with temperature, it decreases with increasing crack-extension velocity at a given temperature and the rate of decrease with respect to crack-extension velocity seems to be independent of temperature. Ksub(ID) appears to be insensitive to heat treatments. Test results indicate insufficient load-train stiffness, and problems due to crack branching were encountered. (author)

  16. On the Relationship of Hemingway's Tough Guys and the China Dream

    Institute of Scientific and Technical Information of China (English)

    Qin Chenghua

    2017-01-01

    Tough guys are a series of literary characters in Hemingway's works.The China Dream is a dream that calls on all Chinese people to be hard-working and aims at full development of the self and the nation.To realize the China Dream,hard work,development and environment protection are essential factors.Hemingway's tough guys are famous for their dedication to work and strong willpower in overcoming difficulties and hardships.Some of their reflections are also pertaining to environmental issues.All of these are good references in realizing the China Dream.Thus,to re-read Hemingway's stories about tough guys nowadays is important for Chinese reading pubhc.

  17. Fracture Toughness (KIC) of Lithography Based Manufactured Alumina Ceramic

    Science.gov (United States)

    Nindhia, T. G. T.; Schlacher, J.; Lube, T.

    2018-04-01

    Precision shaped ceramic components can be obtained by an emerging technique called Lithography based Ceramic Manufacturing (LCM). A green part is made from a slurry consisting of a ceramic powder in a photocurable binder with addition of dispersant and plasticizer. Components are built in a layer–by-layer way by exposing the desired cross- sections to light. The parts are subsequently sintered to their final density. It is a challenge to produce ceramic component with this method that yield the same mechanical properties in all direction. The fracture toughness (KIc) of of LCM-alumina (prepared at LITHOZ GmbH, Austria) was tested by using the Single-Edge-V-Notched Beam (SEVNB) method. Notches are made into prismatic bend-bars in all three direction X, Y and Z to recognize the value of fracture toughness of the material in all three directions. The microstructure was revealed with optical microscopy as well as Scanning Electron Microscopy (SEM). The results indicate that the fracture toughness in Y-direction has the highest value (3.10 MPam1/2) that is followed by the one in X-direction which is just a bit lower (2.90 MPam1/2). The Z-direction is found to have a similar fracture toughness (2.95 MPam1/2). This is supported by a homogeneous microstructure showing no hint of the layers used during production.

  18. Dynamic fracture toughness of ASME SA508 Class 2a ASME SA533 grade A Class 2 base and heat affected zone material and applicable weld metals

    International Nuclear Information System (INIS)

    Logsdon, W.A.; Begley, J.A.; Gottshall, C.L.

    1978-03-01

    The ASME Boiler and Pressure Vessel Code, Section III, Article G-2000, requires that dynamic fracture toughness data be developed for materials with specified minimum yield strengths greater than 50 ksi to provide verification and utilization of the ASME specified minimum reference toughness K/sub IR/ curve. In order to qualify ASME SA508 Class 2a and ASME SA533 Grade A Class 2 pressure vessel steels (minimum yield strengths equal 65 kip/in. 2 and 70 kip/in. 2 , respectively) per this requirement, dynamic fracture toughness tests were performed on these materials. All dynamic fracture toughness values of SA508 Class 2a base and HAZ material, SA533 Grade A Class 2 base and HAZ material, and applicable weld metals exceeded the ASME specified minimum reference toughness K/sub IR/ curve

  19. Dependence of fracture toughness of molybdenum laser welds on processing parameters and in-situ oxygen gettering

    International Nuclear Information System (INIS)

    Pope, L.E.; Jellison, J.L.

    1980-01-01

    Fracture toughness properties have been determined for laser welds in different grades of molybdenum. The fracture toughness of welds in sintered molybdenum was consistently less than the fracture toughness of welds in vacuum arc remelted molybdenum. These differences cannot be attributed to oxygen content, since the oxygen level was nominally the same for all grades of molybdenum examined in this program. Alloy additions of titanium by means of physically deposited coatings significantly improved the fracture toughness of welds in sintered molybdenum, whereas titanium additions to welds in vacuum arc remelted molybdenum decreased the fracture toughness slightly. Pulsed laser welds exhibited fine columnar structures and, in the case of sintered molybdenum, superior fracture toughness when compared with continuous wave laser welds. 6 figures, 3 tables

  20. Application of Master Curve fracture toughness for reactor pressure vessel integrity assessment in the USA

    International Nuclear Information System (INIS)

    Server, William; Rosinski, Stan; Lott, Randy; Kim, Charles; Weakland, Dennis

    2002-01-01

    The Master Curve fracture toughness approach has been used in the USA for better defining the transition temperature fracture toughness of irradiated reactor pressure vessel (RPV) steels for end-of-life (EOL) and EOL extension (EOLE) time periods. The first application was for the Kewaunee plant in which the life-limiting material was a circumferential weld metal. Fracture toughness testing of this weld metal corresponding to EOL and beyond EOLE was used to reassess the PTS screening value, RT PTS , and to develop new operating pressure-temperature curves. The NRC has approved this application using a shift-based methodology and higher safety margins than those proposed by the utility and its contractors. Beaver Valley Unit 1, a First Energy nuclear plant, has performed similar fracture toughness testing, but none of the testing has been conducted at EOL or EOLE at this time. Therefore, extrapolation of the life-limiting plate data to higher fluences is necessary, and the projections will be checked in the next decade by Master Curve fracture toughness testing of all of the Beaver Valley Unit 1 beltline materials (three plates and three welds) at fluences near or greater than EOLE. A supplemental surveillance capsule has been installed in the sister plant, Beaver Valley Unit 2, which has the capability of achieving a higher lead factor while operating under essentially the same environment. The Beaver Valley Unit 1 evaluation has been submitted to the NRC. This paper reviews the shift-based approach taken for the Beaver Valley Unit 1 RPV and presents the use of the RT T 0 methodology (which evolved out of the Master Curve testing and endorsed through two ASME Code Cases). The applied margin accounts for uncertainties in the various material parameters. Discussion of a direct measurement of RT T 0 approach, as originally submitted for the Kewaunee case, is also presented

  1. Toughness and other mechanical properties of the duplex stainless steel 2205

    International Nuclear Information System (INIS)

    Sieurin, H.; Sandstroem, R.

    2003-01-01

    The use and range of potential applications of duplex stainless steel continuously increase. An overview of the mechanical properties of duplex stainless steel 2205 is presented with focus on toughness properties. Impact and fracture toughness as well as strength results from the European research project, EcoPress, are presented. (orig.)

  2. Four Takes on Tough Times

    Science.gov (United States)

    Rebell, Michael A.; Odden, Allan; Rolle, Anthony; Guthrie, James W.

    2012-01-01

    Educational Leadership talks with four experts in the fields of education policy and finance about how schools can weather the current financial crisis. Michael A. Rebell focuses on the recession and students' rights; Allan Odden suggests five steps schools can take to improve in tough times; Anthony Rolle describes the tension between equity and…

  3. Proceedings of the TOUGH workshop

    Energy Technology Data Exchange (ETDEWEB)

    Pruess, K. [ed.

    1990-09-01

    A workshop on applications and enhancements of the TOUGH/MULKOM family of multiphase fluid and heat flow simulation programs was held at Lawrence Berkeley Laboratory on September 13--14, 1990. The workshop was attended by 62 scientists from seven countries with interests in geothermal reservoir engineering, nuclear waste isolation, unsaturated zone hydrology, environmental problems, and laboratory and field experimentation. The meeting featured 21 technical presentations, extended abstracts of which are reproduced in the present volume in unedited form. Simulator applications included processes on a broad range of space scales, from centimeters to kilometers, with transient times from seconds to geologic time scales. A number of code enhancements were reported that increased execution speeds for large 3-D problems by factors of order 20, reduced memory requirements, and improved user-friendliness. The workshop closed with an open discussion session that focussed on future needs and means for interaction in the TOUGH user community. Input from participants was gathered by means of a questionnaire that is reproduced in the appendix. 171 refs., 91 figs., 16 tabs.

  4. Proceedings of the TOUGH workshop

    International Nuclear Information System (INIS)

    Pruess, K.

    1990-09-01

    A workshop on applications and enhancements of the TOUGH/MULKOM family of multiphase fluid and heat flow simulation programs was held at Lawrence Berkeley Laboratory on September 13--14, 1990. The workshop was attended by 62 scientists from seven countries with interests in geothermal reservoir engineering, nuclear waste isolation, unsaturated zone hydrology, environmental problems, and laboratory and field experimentation. The meeting featured 21 technical presentations, extended abstracts of which are reproduced in the present volume in unedited form. Simulator applications included processes on a broad range of space scales, from centimeters to kilometers, with transient times from seconds to geologic time scales. A number of code enhancements were reported that increased execution speeds for large 3-D problems by factors of order 20, reduced memory requirements, and improved user-friendliness. The workshop closed with an open discussion session that focussed on future needs and means for interaction in the TOUGH user community. Input from participants was gathered by means of a questionnaire that is reproduced in the appendix. 171 refs., 91 figs., 16 tabs

  5. Influence of texture on fracture toughness of zircaloy cladding

    International Nuclear Information System (INIS)

    Grigoriev, V.; Andersson, Stefan

    1997-06-01

    The correlation between texture and fracture toughness of Zircaloy 2 cladding has been investigated in connection with axial cracks in fuel rods. The texture of the cladding determines the anisotropy of plasticity of the cladding which, in turn, should influence the strain conditions at the crack-tip. Plastic strains in the cladding under uniaxial tension were characterised by means of the anisotropy constants F, G and H calculated according to Hill's theory. Test temperatures between 20 and 300 deg C do not influence the F, G and H values. Any significant effect of hydrogen (about 500 wtppm) on the anisotropy constants F, G and H has not been revealed at a test temperature of 300 deg C. The results, obtained for stress-relieved and recrystallized cladding with different texture, show an obvious influence of texture on the fracture toughness of Zircaloy cladding. A higher fracture toughness has been found for cladding with more radial texture

  6. Influence of texture on fracture toughness of zircaloy cladding

    Energy Technology Data Exchange (ETDEWEB)

    Grigoriev, V. [Studsvik Material AB, Nykoeping (Sweden); Andersson, Stefan [Royal Inst. of Tech., Stockholm (Sweden)

    1997-06-01

    The correlation between texture and fracture toughness of Zircaloy 2 cladding has been investigated in connection with axial cracks in fuel rods. The texture of the cladding determines the anisotropy of plasticity of the cladding which, in turn, should influence the strain conditions at the crack-tip. Plastic strains in the cladding under uniaxial tension were characterised by means of the anisotropy constants F, G and H calculated according to Hill`s theory. Test temperatures between 20 and 300 deg C do not influence the F, G and H values. Any significant effect of hydrogen (about 500 wtppm) on the anisotropy constants F, G and H has not been revealed at a test temperature of 300 deg C. The results, obtained for stress-relieved and recrystallized cladding with different texture, show an obvious influence of texture on the fracture toughness of Zircaloy cladding. A higher fracture toughness has been found for cladding with more radial texture. With a 2 page summary in Swedish. 32 refs, 18 figs.

  7. Crack arrest toughness measurements with A533B steel

    International Nuclear Information System (INIS)

    Salonen, Seppo.

    1979-11-01

    This work covers crack arrest toughness measurements on A533B steel done at the Technical Research Centre of Finland. These measurements are one part of a multinational effort, involving 30 laboratories. The aim of the cooperative test program is to examine two test procedures for measuring the crack arrest toughness, to give information about their reproducibility, and to identify the factors affecting the interpretation. The principles given for the testing were easy to apply in general and the results were satisfactory. Some factors in the test runs and in the specimen's behaviour are indicated which can cause error in the results or make implementation of the test more difficult. By comparing the results from our laboratory with average values from the test program a good agreement can be seen. Crack arrest toughness values derived from the compared procedures with a static analysis agree closely, but values calculated using a dynamic analysis differ considerably. (author)

  8. Analysis of interlaminar fracture toughness and damage mechanisms in composite laminates reinforced with sprayed multi-walled carbon nanotubes

    International Nuclear Information System (INIS)

    Almuhammadi, Khaled; Alfano, Marco; Yang, Yang; Lubineau, Gilles

    2014-01-01

    Highlights: • CNTs are solvent sprayed on CFRP prepreg to improve interlaminar fracture toughness. • Raman mapping revealed the actual penetration of CNTs across the interface. • A finite thickness nanoreinforced region was able to spread damage through CNT pull-out and peeling. • The induced dissipation mechanisms are operative at the microscale. • The nanoreinforcement strategy led to an increased fracture toughness. - Abstract: The present work is focused on the nanoreinforcement of prepreg based carbon fiber composite laminates to improve delamination resistance. Functionalized multi-walled carbon nanotubes (MWCNTs) were dispersed over the interface between prepreg layers through solvent spraying and the resulting mode I interlaminar fracture toughness was determined. For comparison, baseline samples with neat prepregs were also prepared. Results indicate that the introduction of functionalized MWCNTs can favorably affect the interlaminar fracture toughness, and the associated mechanisms of failure have been investigated. The manufacturing procedures and the interfacial reinforcing mechanism were explored by analyzing (i) the wettability between CNTs-solvent solution and prepreg surface, (ii) CNTs dispersion and (iii) the fractured surfaces through high resolution scanning electron microscopy and Raman mapping

  9. Fracture toughness evaluation of small notched specimen in consideration of notch effect and loading rate

    International Nuclear Information System (INIS)

    Lee, Baik Woo; Kwon, Dong Il; Jang, Jae Il

    2000-01-01

    Notch effect and loading rate dependency on fracture toughness were considered when evaluating fracture toughness of small notched specimens using the instrumented impact test. Notch effect was analyzed into stress redistribution effect and stress relaxation with a viewpoint of stress triaxiality. Stress redistribution effect was corrected by introducing effective crack length, which was the sum of actual crack length and plastic zone size. Stress relaxation effect was also corrected using elastic stress concentration factor, which would decrease if plastic deformation occurred. As a result, corrected fracture toughness of the notched specimen was very consistent with the reference fracture toughness obtained using precracked specimen. In addition, limiting notch root radius, below which fracture toughness was independent of notch radius, was observed and discussed. Loading rate dependency on fracture toughness, which was obtained from the static three point bending test and the instrumented impact test, was also discussed with stress field in plastic zone ahead of a notch and fracture based on stress control mechanism. (author)

  10. Air-tough: A fully 3-dimensional linking of atmosphere with soil using eddy diffusivity concept and V-TOUGH

    Energy Technology Data Exchange (ETDEWEB)

    Montazer, P. [Multimedia Environmental Technology, Inc., Newport Beach, CA (United States)

    1995-03-01

    In arid climates, evapotranspiration is a strongly-coupled thermodynamic process that is controlled by the interaction of the atmospheric boundary layer and the upper soil surface. Simulation of this process requires a fully-coupled thermodynamic multi-phase fluid-flow and energy-transport code. Such a code was developed in a previous investigation using V-TOUGH. The resulting efficient computer code, A-TOUGH, simulates the effect of dynamic atmospheric fluctuations on vapor movement between the soil and the atmosphere and the resulting moisture movement in the soil. However, the coupling between the atmosphere and soil employed eddy diffusivity which was only a function of time and not a function of space. In the present study the code is extended to allow spatial as well as temporal variation of eddy diffusivity.

  11. Effects of toughness anisotropy and combined tension, torsion, and bending loads on fracture behavior of ferritic nuclear pipe

    Energy Technology Data Exchange (ETDEWEB)

    Mohan, R.; Marshall, C.; Ghadiali, N.; Wilkowski, G. [Battelle, Columbus, OH (United States)

    1997-04-01

    This paper summarizes work on angled through-wall-crack initiation and combined loading effects on ferritic nuclear pipe performed as part of the Nuclear Regulatory Commission`s research program entitled {open_quotes}Short Cracks In Piping an Piping Welds{close_quotes}. The reader is referred to Reference 1 for details of the experiments and analyses conducted as part of this program. The major impetus for this work stemmed from the observation that initially circumferentially oriented cracks in carbon steel pipes exhibited a high tendency to grow at a different angle when the cracked pipes were subjected to bending or bending plus pressure loads. This failure mode was little understood, and the effect of angled crack grown from an initially circumferential crack raised questions about how cracks in a piping system subjected to combined loading with torsional stresses would behave. There were three major efforts undertaken in this study. The first involved a literature review to assess the causes of toughness anisotropy in ferritic pipes and to develop strength and toughness data as a function of angle from the circumferential plane. The second effort was an attempt to develop a screening criterion based on toughness anisotropy and to compare this screening criterion with experimental pipe fracture data. The third and more significant effort involved finite element analyses to examine why cracks grow at an angle and what is the effect of combined loads with torsional stresses on a circumferentially cracked pipe. These three efforts are summarized.

  12. Fracture Toughness Evaluation of Kori-1 RPV Beltline Weld for a Long-Term Operation

    International Nuclear Information System (INIS)

    Lee, Bong-Sang; Kim, Min-Chul; Ahn, Sang-Bok; Kim, Byung-Chul; Hong, Jun-Hwa

    2007-01-01

    Irradiation embrittlement of RPV (reactor pressure vessel) material is the most important aging issue for a long-term operation of nuclear power plants. KORI unit 1, which is the first PWR in Korea, is approaching its initial licensing life of 30 years. In order to operate the reactor for another 10 years and more, it should be demonstrated that the irradiation embrittlement of the reactor will be adequately managed by ensuring that the fracture toughness properties have a certain level of the safety margin. The current regulation requires Charpy V-notch impact data through conventional surveillance tests. It is based on the assumption that Charpy impact test results are well correlated with the fracture toughness properties of many engineering steels. However, Charpy V-notch impact data may not be adequate to estimate the fracture toughness of certain materials, such as Linde 80 welds. During the last decade, a tremendous number of fracture toughness data on many RPV steels have been produced in accordance with the new standard test method, the so-called master curve method. ASTM E1921 represents a revolutionary advance in characterizing fracture toughness of RPV steels, since it permits establishing the ductile to brittle transition portion of the fracture toughness curve with direct measurements on a relatively small number of relatively small specimens, such as pre-cracked Charpy specimens. Actual fracture toughness data from many different RPV steels revealed that the Charpy test estimations are generally conservative with the exception of a few cases. Recent regulation codes in USA permit the master curve fracture toughness methodology in evaluating an irradiation embrittlement of commercial nuclear reactor vessels

  13. The influence of hydride on fracture toughness of recrystallized Zircaloy-4 cladding

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Hsiao-Hung, E-mail: 175877@mail.csc.com.tw [Institute of Nuclear Energy Research (INER), Lungtan Township, Taoyuan County 32546, Taiwan, ROC (China); China Steel Corporation, Hsiao Kang District, Kaohsiung 81233, Taiwan, ROC (China); Chiang, Ming-Feng [China Steel Corporation, Hsiao Kang District, Kaohsiung 81233, Taiwan, ROC (China); Chen, Yen-Chen [Institute of Nuclear Energy Research (INER), Lungtan Township, Taoyuan County 32546, Taiwan, ROC (China)

    2014-04-01

    In this work, RXA cladding tubes were hydrogen-charged to target hydrogen content levels between 150 and 800 wppm (part per million by weight). The strings of zirconium hydrides observed in the cross sections are mostly oriented in the circumferential direction. The fracture toughness of hydrided RXA Zircaloy-4 cladding was measured to evaluate its hydride embrittlement susceptibility. With increasing hydrogen content, the fracture toughness of hydrided RXA cladding decreases at both 25 °C and 300 °C. Moreover, highly localized hydrides (forming a hydride rim) aggravate the degradation of the fracture properties of RXA Zircaloy-4 cladding at both 25 °C and 300 °C. Brittle features in the form of quasi-cleavages and secondary cracks were observed on the fracture surface of the hydride rim, even for RXA cladding tested at 300 °C.

  14. Study of cladding toughness in a pressure vessel steel water reactor

    International Nuclear Information System (INIS)

    Soulat, P.; Al Mundheri, M.

    1984-12-01

    Toughness of cladding and pressure vessel steel were determined at different temperatures in order to appreciate the participation of cladding resistance against crack propagation. The toughness of cladding is comparable with typical results on austenitic welds. The test on covered CT specimens shows the possibility of having a relatively good prevision of the behaviour of a coated structure

  15. A Comparative Study on Emotional Intelligence and Mental Toughness for Visually Impaired Male and Female Athletes

    Directory of Open Access Journals (Sweden)

    Robabeh Rostami

    2015-10-01

    Full Text Available Background: Nowadays researches find that athlete’s performance is affected not only by physical fitness, technical and tactical factors, but also mental and emotional features can affect sport performance. Objective: Hence, the aim of this study is examined the dimensions of emotional intelligence and mental toughness visually impaired male and female athletes. Methodology: This was a causal-comparative study, where the statistical population included 300 visually impaired male and female athletes taking part in the First National Cultural- Sports Festival featuring goalball, tug-of-war, track and field, swimming, and powerlifting. Using a smaple of convenience, 70 participants completed the Sheard, Golby, and van Wersch-questionnaire on mental toughness in three dimensions of  “confidence” “ control” and “constancy”, and the Petrides and Furnham’s questionnaire in four dimensions of “ understanding emotions”, “ social skills” “ controlling emotions” and “ optimism”. Results: Analysis of variables using an independent t-test showed significant differences in the dimensions of controlling emotions, understanding emotions, and social skills in favor of visually impaired sportswomen. However, there were no significant differences between the genders for optimism in the emotional intelligence questionnaire, and in mental toughness questionnaire. Conclusions: Visually impaired individuals pass through stages of emotional intelligence in a different way compared to those with normal vision. Moreover, motor skills and sports for the visually impaired are of a different kind. Moreover, our results showed that women benefited more from participating in physical and sporting activities than men did. Therefore, we recommend that authorities and people involved in sports for the visually impaired should make more use of exercises in psychological skills, along with technical and tactical ones, for visually impaired male

  16. Estimation of fracture toughness of cast stainless steels during thermal aging in LWR systems

    International Nuclear Information System (INIS)

    Chopra, O.K.

    1991-06-01

    A procedure and correlations are presented for predicting the change in fracture toughness of cast stainless steel components due to thermal aging during service in light water rectors (LWRs) at 280--330 degrees C (535--625 degrees F). The fracture toughness J-R curve and Charpy-impact energy of aged cast stainless steels are estimated from known mineral in formation. Fracture toughness of a specific cast stainless steel is estimated from the extent and kinetics of thermal embrittlement. The extent of thermal embrittlement is characterized by the room-temperature ''normalized'' Charpy-impact energy. A correlation for the extent of embrittlement at ''saturation,'' i.e., the minimum impact energy that would be achieved for the material after long-term aging, is given in terms of a material parameter, Φ, which is determined from the chemical composition. The fracture toughness J-R curve for the material is then obtained from correlations between room-temperature Charpy-impact energy and fracture toughness parameters. Fracture toughness as a function of time and temperature of reactor service is estimated from the kinetics of thermal embrittlement, which is determined from chemical composition. A common ''lower-bound'' J-R curve for cast stainless steels with unknown chemical composition is also defined for a given material specification, ferrite content, and temperature. Examples for estimating impact strength and fracture toughness of cast stainless steel components during reactor service are describes. 24 refs., 39 figs., 2 tabs

  17. Estimation of fracture toughness of cast stainless steels during thermal aging in LWR systems

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O.K. (Argonne National Lab., IL (USA))

    1991-06-01

    A procedure and correlations are presented for predicting the change in fracture toughness of cast stainless steel components due to thermal aging during service in light water rectors (LWRs) at 280--330{degrees}C (535--625{degrees}F). The fracture toughness J-R curve and Charpy-impact energy of aged cast stainless steels are estimated from known mineral in formation. Fracture toughness of a specific cast stainless steel is estimated from the extent and kinetics of thermal embrittlement. The extent of thermal embrittlement is characterized by the room-temperature normalized'' Charpy-impact energy. A correlation for the extent of embrittlement at saturation,'' i.e., the minimum impact energy that would be achieved for the material after long-term aging, is given in terms of a material parameter, {Phi}, which is determined from the chemical composition. The fracture toughness J-R curve for the material is then obtained from correlations between room-temperature Charpy-impact energy and fracture toughness parameters. Fracture toughness as a function of time and temperature of reactor service is estimated from the kinetics of thermal embrittlement, which is determined from chemical composition. A common lower-bound'' J-R curve for cast stainless steels with unknown chemical composition is also defined for a given material specification, ferrite content, and temperature. Examples for estimating impact strength and fracture toughness of cast stainless steel components during reactor service are describes. 24 refs., 39 figs., 2 tabs.

  18. Fracture toughness behaviour using small CCT specimen of Zr-2.5Nb pressure tube materials

    International Nuclear Information System (INIS)

    Oh, Dong Joon; Kim, Young Suk; Ahn, Sang Bok; Im, Kyung Soo; Kwon, Sang Chul; Cheong, Yong Mu

    2001-03-01

    Fracture toughness of Zr-2.5Nb pressure tube is the essential data to estimate the CCL(critical crack length) for the concept of LBB(Leak-Before-Break) in PHWR. Zr-2.5Nb pressure tubes could be degraded due to the absorption of hydrogen from coolant and the irradiation. To investigate the fracture toughness behaviour such as J-resistance curves, dJ/da, and CCL of some Zr-alloys (CANDU-double, -quad, CW-E125, TMT-E125, E-635), the transverse tensile test and the fracture toughness test of small CCT (Curved Compact Tension) specimen with 17 mm width were carried out with the variation of testing temperature at different testing condition. To define the fracture mechanism of degradation, the fractographic comparison of fracture surface was performed using the stereoscope and SEM. In addition, the effect of non-uniformed pre-fatigue crack was also studied. In conclusion, CANDU double-melted was less tougher than CANDU quad-melted and the hydrogen embrittlement was found at room temperature. Finally, while the effect of non-uniformed pre-fatigue crack was considerable at room temperature, this effect was disappeared at 250-300 .deg. C

  19. Resolution of the Task A-11 reactor-vessel materials-toughness safety issue. Appendices C-K

    International Nuclear Information System (INIS)

    1982-10-01

    The central problem in the unresolved safety issue A-11, Reactor Vessel Materials Toughness, was to provide guidance in performing analyses required by 10 CFR Part 50, Appendix G, Section V.C. for reactor pressure vessels (RPVs) which fail to meet the toughness requirement during service life as a result of neutron radiation embrittlement. Although the methods of linear-elastic fracture mechanics (LEFM) were adequate for low-temperature RPV problems, they were inapplicable under operating conditions because vessel steels, even those which exhibit less than 50 ft-lb of C/sub v/ energy, were relatively tough at temperatures where the impact energy reached its upper shelf values. A technical team of recognized experts was organized to assist the NRC staff in addressing the problem. Using the foundation of the tearing modulus concept, which had been developed under earlier NRC sponsorship, relationships were obtained which provided approximate solutions to the problem of RPV fracture with assumed beltline region flaws. The first paper of this report is a summary of the problem, the solutions, and the results of verification analyses. The details are provided in a series of appendices in Volumes I and II

  20. Aspects of the Fracture Toughness of Carbon Nanotube Modified Epoxy Polymer Composites

    Science.gov (United States)

    Mirjalili, Vahid

    Epoxy resins used in fibre reinforced composites exhibit a brittle fracture behaviour, because they show no sign of damage prior to a catastrophic failure. Rubbery materials and micro-particles have been added to epoxy resins to improve their fracture toughness, which reduces strength and elastic properties. In this research, carbon nanotubes (CNTs) are investigated as a potential toughening agent for epoxy resins and carbon fibre reinforced composites, which can also enhance strength and elastic properties. More specifically, the toughening mechanisms of CNTs are investigated theoretically and experimentally. The effect of aligned and randomly oriented carbon nanotubes (CNTs) on the fracture toughness of polymers was modelled using Elastic Plastic Fracture Mechanics. Toughening from CNT pull-out and rupture were considered, depending on the CNTs critical length. The model was used to identify the effect of CNTs geometrical and mechanical properties on the fracture toughness of CNT-modified epoxies. The modelling results showed that a uniform dispersion and alignment of a high volume fraction of CNTs normal to the crack growth plane would lead to the maximum fracture toughness enhancement. To achieve a uniform dispersion, the effect of processing on the dispersion of single walled and multi walled CNTs in epoxy resins was investigated. An instrumented optical microscope with a hot stage was used to quantify the evolution of the CNT dispersion during cure. The results showed that the reduction of the resin viscosity at temperatures greater than 100 °C caused an irreversible re-agglomeration of the CNTs in the matrix. The dispersion quality was then directly correlated to the fracture toughness of the modified resin. It was shown that the fine tuning of the ratio of epoxy resin, curing agent and CNT content was paramount to the improvement of the base resin fracture toughness. For the epoxy resin (MY0510 from Hexcel), an improvement of 38% was achieved with 0.3 wt

  1. Effect of zirconium purity on the glass-forming-ability and notch toughness of Cu{sub 43}Zr{sub 43}Al{sub 7}Be{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Andersen, Laura M. [Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA (United States); Hofmann, Douglas C. [Materials Development and Manufacturing Technology Group, NASA Jet Propulsion Laboratory/California Institute of Technology, MS 18-105, 4800 Oak Grove Dr. Pasadena, CA 91109 (United States); Vecchio, Kenneth S., E-mail: kvecchio@ucsd.edu [Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA (United States)

    2016-09-30

    The effect of substituting standard grade zirconium lump (99.8% excluding up to 4% hafnium) for high purity zirconium crystal bar (99.5%) in a Cu{sub 43}Zr{sub 43}Al{sub 7}Be{sub 7} bulk metallic glass (BMG) is examined. The final hafnium content in the BMG specimens was found to range from 0 to 0.44 at%. Introducing low purity zirconium significantly decreased the glass-forming-ability and reduced the notch toughness of the BMG. In contrast, when adding high purity hafnium to Cu{sub 43}Zr{sub 43}Al{sub 7}Be{sub 7} made with high purity zirconium, no significant change in the glass-forming-ability or toughness was observed. This suggests that the introduction of low purity zirconium in BMGs creates a more complex response than a simple addition of hafnium. It is likely that other impurities in the material, such as oxygen, play a role in the complex crystallization kinetics and change in mechanical properties. The notch toughness was measured through four-point-bend tests, which showed a decrease in notch toughness from an average of ~53 MPa m{sup 1/2} for the high purity samples to an average of ~29 MPa m{sup 1/2} with full substitution of low purity zirconium. A similar decrease in glass-forming-ability and toughness is observed in commercially synthesized high purity Cu{sub 43}Zr{sub 43}Al{sub 7}Be{sub 7}. The large scale commercial process is expected to introduced some unintentional impurities, which decrease the properties of the BMG in the same way as the lower purity elements. Lastly, Weibull statistics are used to provide an analysis of variability in toughness for both ingots synthesized in a small laboratory arc-melter and those synthesized commercially.

  2. Photoelastic stress analysis assisted evaluation of fracture toughness in hydrothermally aged epoxies

    Directory of Open Access Journals (Sweden)

    G. Pitarresi

    2014-10-01

    Full Text Available The present work has investigated the fracture toughness of a model DGEBA epoxy system subject to Hidro-Thermal aging. A Photoelastic Stress Analysis technique has been implemented, showing the evolution of stresses arising throughout the water uptake process due to the non-uniform swelling of the material. Gravimetric and Dynamic Mechanical Thermal Analyses have further complemented the characterization, showing the onset of plasticization effects with aging. The correlation of all previous characterizations has allowed to conclude that an increase of KIC fracture toughness is obtained at the fully saturated condition. In particular Photoelasticity has also revealed the onset of relevant swelling induced stresses during the first stages of water absorption, leading to an increase of fracture toughness due to compressive stresses settling near the crack tip. A stress free condition is instead reestablished at the later stages of absorption, suggesting that the increased toughness of the saturated material is an effect of the modifications induced by aging on the polymer structure.

  3. Mechanical Performance of Ferritic Martensitic Steels for High Dose Applications in Advanced Nuclear Reactors

    Science.gov (United States)

    Anderoglu, Osman; Byun, Thak Sang; Toloczko, Mychailo; Maloy, Stuart A.

    2013-01-01

    Ferritic/martensitic (F/M) steels are considered for core applications and pressure vessels in Generation IV reactors as well as first walls and blankets for fusion reactors. There are significant scientific data on testing and industrial experience in making this class of alloys worldwide. This experience makes F/M steels an attractive candidate. In this article, tensile behavior, fracture toughness and impact property, and creep behavior of the F/M steels under neutron irradiations to high doses with a focus on high Cr content (8 to 12) are reviewed. Tensile properties are very sensitive to irradiation temperature. Increase in yield and tensile strength (hardening) is accompanied with a loss of ductility and starts at very low doses under irradiation. The degradation of mechanical properties is most pronounced at martensitic steels exhibit a high fracture toughness after irradiation at all temperatures even below 673 K (400 °C), except when tested at room temperature after irradiations below 673 K (400 °C), which shows a significant reduction in fracture toughness. Creep studies showed that for the range of expected stresses in a reactor environment, the stress exponent is expected to be approximately one and the steady state creep rate in the absence of swelling is usually better than austenitic stainless steels both in terms of the creep rate and the temperature sensitivity of creep. In short, F/M steels show excellent promise for high dose applications in nuclear reactors.

  4. Irradiation and inhomogeneity effects on ductility and toughness of (ODS)-7 -13Cr steels

    International Nuclear Information System (INIS)

    Preininger, D.

    2007-01-01

    Full text of publication follows: The superimposed effect of irradiation defect and structural inhomogeneity formation on tensile ductility and dynamic toughness of ferritic-martensitic 7-13CrW(Mo)VTa(Nb) and oxide dispersion-strengthened (ODS)-7-13CrWVTa(Ti)- RAFM steels has been examined by work hardening and local stress/strain-induced ductile fracture models. Structural inhomogeneities which strongly promoting plastic instability and localized flow might be formed by the applied fabrication process, high dose irradiation and additionally further during deformation by enhanced local dislocation generation around fine particles or due to slip band formation with localized heating at high impact strain rates ε'. The work hardening model takes into account superimposed dislocation multiplication from stored dislocations, dispersions and also grain boundaries as well as annihilation by cross-slip. Analytical relations have been deduced from the model describing uniform ductility and ductile upper shelf energy (USE) observed from Charpy-impact testes. Especially, the influence of different irradiation defects like atomic clusters, dislocation loops and coherent chromium-rich α'- precipitates have been considered together with effects from strain rate as well as irradiation (TI) and test temperature TT. Strengthening by clusters and more pronounced by dislocation loops formed at higher TI>250 deg. C reduces uniform ductility and also distinctly stronger dynamic toughness USE. A superimposed hardening by the α'- formation in higher Cr containing 9-13Cr steels strongly reduces toughness assisted by a combined grain-boundary embrittlement with reduction of the ductile fracture stress. But that improves work hardening and uniform ductility as observed particularly due to nano-scale Y 2 O 3 - dispersions in ODS-RAFM steels. For ODS- steels additionally the strength-induced reduction of toughness is diminished by a combined microstructural-induced increase of the ductile

  5. Effects of Forming Process on Composite mode I Interlaminar Fracture Toughness

    Directory of Open Access Journals (Sweden)

    CHEN Xingyi

    2016-10-01

    Full Text Available In order to compare and analyse the effect of two different kinds of forming process on composite mode I interlaminar fracture toughness, the DCB specimens were tested by using hypothesis inspeetion method.A finite element model was also used to simulate the crack propagation process.The results demonstrate that the average of mode I interlaminar fracture toughness from silicon rubber flexible mold forming is a bit higher than that from metal rigid mold forming.Howevers the variance of mode I interlaminar fracture toughness from the two groups shows no significant difference.The crack propagation process of the two forming process is similar. The established finite element model, which is identical to the test results, can predict the process of the crack expansion effectively.

  6. Fracture toughness of titanium–cement interfaces: effects of fibers and loading angles

    Directory of Open Access Journals (Sweden)

    Khandaker M

    2014-04-01

    .05. The study also found a significant difference in the KC means of Ti–PMMA samples with and without fibers (P<0.05. The results showed that the addition of the micron- to nanosize PCL fibers on Ti improved the quality of the Ti–PMMA union. The results of the study are essential for fatigue testing and finite-element analysis of implant–cement interfaces to evaluate the performance of orthopedic and orthodontic implants.Keywords: titanium, cement, interface, PMMA, polycaprolactone, fracture toughness, orthopedics, orthodontics

  7. Effect of step-aging on the fracture toughness of Ti-15V-3Cr-3Sn-3Al alloy

    International Nuclear Information System (INIS)

    Niwa, Naotake

    1993-01-01

    Development and an application of a new high-low step-aging to improve the fracture toughness-strength balance of a Ti-15V-3Cr-3Sn-3Al alloy are studied. The high-low step-aging of aging at higher temperatures followed by aging at lower temperatures produces bi-modal microstructure composed of coarse and fine alpha precipitates in beta matrix. It greatly improves fracture toughness-strength balance compared with aging at a single temperature. Homogeneous distribution of coarse alpha precipitates produced by adding pre-aging at 573K before the high-low step-aging tends to reduce the superiority of the bi-modal microstructure in fracture toughness. The improvement is provided by the formation of microcracks and voids in the coarse alpha precipitates and rugged crack propagation due to the uneven microstructure. The high-low step-aging is applied to a TIG weldment of the alloy to improve the mechanical properties of the weldment. In the TIG weldment, strength of a fusion zone becomes much higher than that of a base metal after aging at a single temperature because of different aging response. In the first high temperature aging of the high low step-aging, coarse alpha particles that strengthen little and suppress strengthening by fine alpha precipitation in low temperature re-aging, precipitate more in fusion zone than in base metal because of the enhancement of aging in fusion zone. Therefore, strengthening of fusion zone in re-aging is less than in the base metal, resulting in comparable strength between the fusion zone and the base metal after re-aging. The bi-modal microstructure produced by the step-aging also improves, the, fracture toughness of the fusion zone of the weldment

  8. Toughness of submerged arc weld metals of controlled rolled NB bearing steel

    International Nuclear Information System (INIS)

    Yamaguchi, T.; Shiga, A.; Kamada, A.; Tsuboi, J.

    1982-01-01

    The toughness and the hardness of reheated weld metals depend on the maximum reheating temperature. When the maximum reheating temperature is 500 to 700 0 C, the hardness of single pass weld metal increases and the toughness decreases because of fine Nb- and V-carbonitride precipitation. When the maximum reheating temperature is over 800 0 C, the hardness and the toughness remain almost unchanged. The stress relieving treatment of single pass weld metal at 600 0 C for 1 up to about 100 hours causes the increase in hardness and then decreases the hardness gradually. It needs over 500 hours to obtain the same hardness value as that of as-welded metal. The addition of Ti to weld metal is very effective to improve the toughness, however excess Ti increases the hardness of stress relieved weld metal by precipitating as fine Ti-carbonitride. Therefore Ti addition should be restricted within the lowest limit required to improve as-welded metal toughness. The optimum Ti content is about 0.020% in the case of weld metal of which oxygen content is 350 ppM or so. In multipass welding, the hardness of weld metal affected by subsequent weld heat cycle varies from pass to pass, because Nb and V content change with the passes as the result of the change in dilution from base metal. The most hardened zone is observed in the reheated first pass weld metal, in which Nb and V content are the highest. Good weld metal toughness would be obtained by lowering dilution from base metal and taking advantage of grain refinement by subsequent passes

  9. Fatigue Performance and Multiscale Mechanisms of Concrete Toughened by Polymers and Waste Rubber

    Directory of Open Access Journals (Sweden)

    Bo Chen

    2014-01-01

    Full Text Available For improving bending toughness and fatigue performance of brittle cement-based composites, two types of water-soluble polymers (such as dispersible latex powder and polyvinyl alcohol powder and waste tire-rubber powders are added to concrete as admixtures. Multiscale toughening mechanisms of these additions in concretes were comprehensively investigated. Four-point bending fatigue performance of four series concretes is conducted under a stress level of 0.70. The results show that the effects of dispersible latex powder on bending toughness and fatigue life of concrete are better than those of polyvinyl alcohol powder. Furthermore, the bending fatigue lives of concrete simultaneously containing polymers and waste rubber powders are larger than those of concrete with only one type of admixtures. The multiscale physics-chemical mechanisms show that high bonding effect and high elastic modulus of polymer films as well as good elastic property and crack-resistance of waste tire-rubber powders are beneficial for improving bending toughness and fatigue life of cementitious composites.

  10. The Opportunity for High-Performance Biomaterials from Methane.

    Science.gov (United States)

    Strong, Peter James; Laycock, Bronwyn; Mahamud, Syarifah Nuraqmar Syed; Jensen, Paul Douglas; Lant, Paul Andrew; Tyson, Gene; Pratt, Steven

    2016-02-03

    Polyhydroxyalkanoate (PHA) biopolymers are widely recognised as outstanding candidates to replace conventional petroleum-derived polymers. Their mechanical properties are good and can be tailored through copolymer composition, they are biodegradable, and unlike many alternatives, they do not rely on oil-based feedstocks. Further, they are the only commodity polymer that can be synthesised intracellularly, ensuring stereoregularity and high molecular weight. However, despite offering enormous potential for many years, they are still not making a significant impact. This is broadly because commercial uptake has been limited by variable performance (inconsistent polymer properties) and high production costs of the raw polymer. Additionally, the main type of PHA produced naturally is poly-3-hydroxybutyrate (PHB), which has limited scope due to its brittle nature and low thermal stability, as well as its tendency to embrittle over time. Production cost is strongly impacted by the type of the feedstock used. In this article we consider: the production of PHAs from methanotrophs using methane as a cost-effective substrate; the use of mixed cultures, as opposed to pure strains; and strategies to generate a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer (PHBV), which has more desirable qualities such as toughness and elasticity.

  11. Development of a Weibull model of cleavage fracture toughness for shallow flaws in reactor pressure vessel material

    Energy Technology Data Exchange (ETDEWEB)

    Bass, B.R.; Williams, P.T.; McAfee, W.J.; Pugh, C.E. [Oak Ridge National Lab., Heavy-Section Steel Technology Program, Oak Ridge, TN (United States)

    2001-07-01

    A primary objective of the United States Nuclear Regulatory Commission (USNRC) -sponsored Heavy-Section Steel Technology (HSST) Program is to develop and validate technology applicable to quantitative assessments of fracture prevention margins in nuclear reactor pressure vessels (RPVs) containing flaws and subjected to service-induced material toughness degradation. This paper describes an experimental/analytical program for the development of a Weibull statistical model of cleavage fracture toughness for applications to shallow surface-breaking and embedded flaws in RPV materials subjected to multi-axial loading conditions. The experimental part includes both material characterization testing and larger fracture toughness experiments conducted using a special-purpose cruciform beam specimen developed by Oak Ridge National Laboratory for applying biaxial loads to shallow cracks. Test materials (pressure vessel steels) included plate product forms (conforming to ASTM A533 Grade B Class 1 specifications) and shell segments procured from a pressurized-water reactor vessel intended for a nuclear power plant. Results from tests performed on cruciform specimens demonstrated that biaxial loading can have a pronounced effect on shallow-flaw fracture toughness in the lower-transition temperature region. A local approach methodology based on a three-parameter Weibull model was developed to correlate these experimentally-observed biaxial effects on fracture toughness. The Weibull model, combined with a new hydrostatic stress criterion in place of the more commonly used maximum principal stress in the kernel of the Weibull stress integral definition, is shown to provide a scaling mechanism between uniaxial and biaxial loading states for 2-dimensional flaws located in the A533-B plate material. The Weibull stress density was introduced as a matrice for identifying regions along a semi-elliptical flaw front that have a higher probability of cleavage initiation. Cumulative

  12. Development of a Weibull model of cleavage fracture toughness for shallow flaws in reactor pressure vessel material

    International Nuclear Information System (INIS)

    Bass, B.R.; Williams, P.T.; McAfee, W.J.; Pugh, C.E.

    2001-01-01

    A primary objective of the United States Nuclear Regulatory Commission (USNRC) -sponsored Heavy-Section Steel Technology (HSST) Program is to develop and validate technology applicable to quantitative assessments of fracture prevention margins in nuclear reactor pressure vessels (RPVs) containing flaws and subjected to service-induced material toughness degradation. This paper describes an experimental/analytical program for the development of a Weibull statistical model of cleavage fracture toughness for applications to shallow surface-breaking and embedded flaws in RPV materials subjected to multi-axial loading conditions. The experimental part includes both material characterization testing and larger fracture toughness experiments conducted using a special-purpose cruciform beam specimen developed by Oak Ridge National Laboratory for applying biaxial loads to shallow cracks. Test materials (pressure vessel steels) included plate product forms (conforming to ASTM A533 Grade B Class 1 specifications) and shell segments procured from a pressurized-water reactor vessel intended for a nuclear power plant. Results from tests performed on cruciform specimens demonstrated that biaxial loading can have a pronounced effect on shallow-flaw fracture toughness in the lower-transition temperature region. A local approach methodology based on a three-parameter Weibull model was developed to correlate these experimentally-observed biaxial effects on fracture toughness. The Weibull model, combined with a new hydrostatic stress criterion in place of the more commonly used maximum principal stress in the kernel of the Weibull stress integral definition, is shown to provide a scaling mechanism between uniaxial and biaxial loading states for 2-dimensional flaws located in the A533-B plate material. The Weibull stress density was introduced as a matrice for identifying regions along a semi-elliptical flaw front that have a higher probability of cleavage initiation. Cumulative

  13. Effect of Precipitation on Cryogenic Toughness in Isothermally Aged Austenitic Stainless Steel

    Science.gov (United States)

    Saucedo-Muñoz, M. L.; Lopez-Hirata, V. M.; Avila-Davila, E. O.; Villegas-Cardenas, J. D.; Gonzalez-Velazquez, J. L.

    2017-03-01

    The effect of grain-boundary precipitates on cryogenic impact toughness of two corrosion steels (standard AISI 316 and a steel with a nitrogen additive) is studied. The steels are aged at 600 - 900°C with a hold of up to 1000 min. The KCV impact toughness at -196°C is determined. It is shown that the impact toughness of the nitrogen-containing steel decreases under cooling after the aging at 700 and 800°C more considerably than that of steel 316 after aging at 800 and 900°C. The causes of the embrittlement of the nitrogen-containing steel are determined.

  14. Upper shelf toughness of six submerged-arc weldmetals manufactured using Linde 124 flux

    International Nuclear Information System (INIS)

    Druce, S.G.; Hippsley, C.A.

    1984-06-01

    This paper describes the testing technique, data analysis procedures and results from the first phase of an experimental programme investigating upper shelf toughness of six submerged-arc weldmetals. The welds were manufactured using uncoated, Nickel coated and Copper coated wire electrodes and Linde 124 flux. J integral crack growth resistance curves have been derived from tests on single specimens over a range in temperature from 150 to 290 deg C. The results indicate a general decline in toughness with increasing temperature. At 290 deg C, the levels of initiation toughness from all six welds were essentially constant varying between 152 to 159 MPa square root of m. The Jsub(I)-R curves derived from this work are compared with toughness data used in the Marshall Study Group report of an assessment of the integrity of PWR pressure vessels. (author)

  15. Emotions & Relationships: Dealing with the Tough Stuff

    Science.gov (United States)

    Emotions & Relationships: Dealing with the Tough Stuff; emotional health; emotional health; emotional health article; emotional health articles; best way to deal with emotions; best ways to deal with relationships; how to build relationships; how to strengthen relationships

  16. TOUGH2: A general-purpose numerical simulator for multiphase nonisothermal flows

    Energy Technology Data Exchange (ETDEWEB)

    Pruess, K. [Lawrence Berkeley Lab., CA (United States)

    1991-06-01

    Numerical simulators for multiphase fluid and heat flows in permeable media have been under development at Lawrence Berkeley Laboratory for more than 10 yr. Real geofluids contain noncondensible gases and dissolved solids in addition to water, and the desire to model such `compositional` systems led to the development of a flexible multicomponent, multiphase simulation architecture known as MULKOM. The design of MULKOM was based on the recognition that the mass-and energy-balance equations for multiphase fluid and heat flows in multicomponent systems have the same mathematical form, regardless of the number and nature of fluid components and phases present. Application of MULKOM to different fluid mixtures, such as water and air, or water, oil, and gas, is possible by means of appropriate `equation-of-state` (EOS) modules, which provide all thermophysical and transport parameters of the fluid mixture and the permeable medium as a function of a suitable set of primary thermodynamic variables. Investigations of thermal and hydrologic effects from emplacement of heat-generating nuclear wastes into partially water-saturated formations prompted the development and release of a specialized version of MULKOM for nonisothermal flow of water and air, named TOUGH. TOUGH is an acronym for `transport of unsaturated groundwater and heat` and is also an allusion to the tuff formations at Yucca Mountain, Nevada. The TOUGH2 code is intended to supersede TOUGH. It offers all the capabilities of TOUGH and includes a considerably more general subset of MULKOM modules with added capabilities. The paper briefly describes the simulation methodology and user features.

  17. Heat-treatment and heat-to-heat variations in the fracture toughness of Alloy 718

    International Nuclear Information System (INIS)

    Mills, W.J.

    1981-07-01

    The effect of heat-treatment and heat-to-heat variations on the J Ic fracture toughness response of Alloy 718 was examined at room and elevated temperatures using the multiple-specimen R-curve technique. Six heats of alloy 718 were tested in the conventional and modified heat-treated conditions. The fracture toughness response for the modified superalloy was found to be superior to that exhibited by the conventional material. Heat-to-heat variations in the J Ic response of Alloy 718 were observed in both heat-treated conditions; the modified treatment exhibited much larger variability. The J Ic and corresponding K Ic fracture toughness values were analyzed statistically to establish minimum expected toughness, values for use in design and safety analyses. 26 refs., 10 figs., 9 tabs

  18. During early and mid-adolescence, greater mental toughness is related to increased sleep quality and quality of life.

    Science.gov (United States)

    Brand, Serge; Kalak, Nadeem; Gerber, Markus; Clough, Peter J; Lemola, Sakari; Pühse, Uwe; Holsboer-Trachsler, Edith

    2016-06-01

    The aim of this study was to explore the association between mental toughness, subjective sleep, physical activity, and quality of life during early and mid-adolescence. A total of 1475 participants (mean age = 13.4 years; range: 11-16 years) took part in the study. They completed questionnaires related to mental toughness, physical activity, subjective sleep, and quality of life. Greater mental toughness was related to more favorable quality of life and increased subjective sleep. Mental toughness was not related to physical activity. Increased mental toughness, favorable quality of life, and sleep are related during early and mid-adolescence. Against our expectations, mental toughness was not related to physical activity. © The Author(s) 2014.

  19. Interrelation of material microstructure, ultrasonic factors, and fracture toughness of two phase titanium alloy

    Science.gov (United States)

    Vary, A.; Hull, D. R.

    1982-01-01

    The pivotal role of an alpha-beta phase microstructure in governing fracture toughness in a titanium alloy, Ti-662, is demonstrated. The interrelation of microstructure and fracture toughness is demonstrated using ultrasonic measurement techniques originally developed for nondestructive evaluation and material property characterization. It is shown that the findings determined from ultrasonic measurements agree with conclusions based on metallurgical, metallographic, and fractographic observations concerning the importance of alpha-beta morphology in controlling fracture toughness in two phase titanium alloys.

  20. Fracture toughness and sliding properties of magnetron sputtered CrBC and CrBCN coatings

    Science.gov (United States)

    Wang, Qianzhi; Zhou, Fei; Ma, Qiang; Callisti, Mauro; Polcar, Tomas; Yan, Jiwang

    2018-06-01

    CrBC and CrBCN coatings with low and high B contents were deposited on 316L steel and Si wafers using an unbalanced magnetron sputtering system. Mechanical properties including hardness (H), elastic modulus (E) and fracture toughness (KIc) as well as residual stresses (σ) were quantified. A clear correlation between structural, mechanical and tribological properties of coatings was found. In particular, structural analyses indicated that N incorporation in CrBC coatings with high B content caused a significant structural evolution of the nanocomposite structure (crystalline grains embedded into an amorphous matrix) from nc-CrB2/(a-CrBx, a-BCx) to nc-CrN/(a-BCx, a-BN). As a result, the hardness of CrBC coating with high B content decreased from 23.4 to 16.3 GPa but the fracture toughness was enhanced. Consequently, less cracks initiated on CrBCN coatings during tribological tests, which combined with the shielding effect of a-BN on wear debris, led to a low friction coefficient and wear rate.

  1. Preparation and demonstration of poly(dopamine)-triggered attapulgite-anchored polyurethane as a high-performance rod-like elastomer to reinforce soy protein-isolated composites

    Science.gov (United States)

    Zhao, Shujun; Wen, Yingying; Wang, Zhong; Kang, Haijiao; Li, Jianzhang; Zhang, Shifeng; Ji, Yong

    2018-06-01

    Nanophase modification is an effective path to improve composite properties, however, it remains a great challenge to increase the mechanical strength of the modified materials without sacrificing elongation and toughness. This study presents a novel and efficient design for interface anchoring of a waterborne polyurethane (WPU) elastomer with attapulgite (ATP) triggered by poly(dopamine) (PDA) formation due to self-polymerization of the dopamine moieties. The WPU-PDA-ATP (WDA) rod-like elastomer served as an active enhancer for a soy protein isolate (SPI)-based composite to facilitate multiple interactions between SPI and the elastomer. As expected, the PDA layer was coated onto ATP, inducing the nanofiller to successfully anchor onto the WPU elastomer, as confirmed by solid-state 13C NMR, XPS, and ATR-FTIR results. Compared with the control SPI-based film, the tensile strength and toughness increased by 145.6% and 118.3% respectively by introducing WDA rod-like elastomer. The water resistance and thermal stability of the prepared SPI composites were also favorable. The proposed approach represents an efficient way to utilize high-performance elastomer in biobased materials to concurrently enhance strength and toughness.

  2. Determination of fracture toughness of human permanent and primary enamel using an indentation microfracture method.

    Science.gov (United States)

    Hayashi-Sakai, Sachiko; Sakai, Jun; Sakamoto, Makoto; Endo, Hideaki

    2012-09-01

    The purpose of the present study was to examine the fracture toughness and Vickers microhardness number of permanent and primary human enamel using the indentation microfracture method. Crack resistance and a parameter indirectly related to fracture toughness were measured in 48 enamel specimens from 16 permanent teeth and 12 enamel specimens obtained from six primary teeth. The Vickers microhardness number of the middle portion was greater than the upper portion in primary enamel. The fracture toughness was highest in the middle portion of permanent enamel, because fracture toughness greatly depends upon microstructure. These findings suggest that primary teeth are not miniature permanent teeth but have specific and characteristic mechanical properties.

  3. The effect of crack instability/stability on fracture toughness of brittle materials

    International Nuclear Information System (INIS)

    Baratta, F.I.

    1997-01-01

    This paper summarizes three recent experimental works coauthored by the present author regarding the effect of crack instability/stability on fracture toughness, and also includes the necessary formulae for predicting stability. Two recent works have shown that unstable crack extension resulted in apparent increases in fracture toughness compared to that determined during stable crack growth. In the first investigation a quasi-brittle polymer, polymethylmethacrylate, was examined. In the second, a more brittle metallic material, tungsten, was tested. In both cases the transition from unstable to stable behavior was predicted based on stability analyses. The third investigation was conducted on a truly brittle ceramic material, hot pressed silicon nitride. These three papers showed that fracture toughness test results conducted on brittle materials vary according to whether the material fractures in an unstable or stable manner. Suggestions for achieving this important yet difficult phenomenon of stable crack growth, which is necessary when determining the fracture toughness variation occurring during unstable/stable crack advance, are presented, as well as recommendations for further research

  4. Prediction of fracture toughness K/sub Ic/ of steel from Charpy impact test results

    Energy Technology Data Exchange (ETDEWEB)

    Iwadate, Tadao; Tanaka, Yasuhiko; Takemata, Hiroyuki; Terashima, Shuhei

    1986-08-01

    This paper presents a method to predict the fracture toughness K/sub Ic/ and/or K/sub Id/ of steels using their Charpy impact test results and tensile properties. The fracture toughness, Charpy impact and tensile properties of 2 1/4 Cr-1Mo, ASTM A508 Cl.1, A508 Cl.2 A508 Cl.3 and A533 Gr.B Cl.1 steels were measured and analysed on the basis of the excess temperature (test temperature minus FATT) and Rolfe-Novak correlation. The relationship between K/sub Ic//K/sub Ic-us/ and the excess temperature, where K/sub Ic-us/ is the upper-shelf fracture toughness K/sub Ic/ predicted by Rolfe-Novak correlation, discloses that the K/sub Ic/ transition curves of several steels are representable by only one trend curve of K/sub Ic//K/sub Ic-us/ or K/sub Id//K/sub Id-us/ versus excess temperature relation. This curve is denoted as a ''master curve''. By using this curve, the fracture toughness of steel can be predicted using Charpy impact and tensile test results. By taking account of the scattering of both the fracture toughness and Charpy impact test results, the confidence limits of the master curve were also determined. Another approach to develop more general procedure of predicting the fracture toughness K/sub Ic/ is also discussed.

  5. Fast reactor irradiation effects on fracture toughness of Si_3N_4 in comparison with MgAl_2O_4 and yttria stabilized ZrO_2

    International Nuclear Information System (INIS)

    Tada, K.; Watanabe, M.; Tachi, Y.; Kurishita, H.; Nagata, S.; Shikama, T.

    2016-01-01

    Fracture toughness of silicon nitride (Si_3N_4), magnesia-alumina spinel (MgAl_2O_4) and yttria stabilized zirconia (8 mol%Y_2O_3–ZrO_2) was evaluated by the Vickers-indentation technique after the fast reactor irradiation up to 55 dpa (displacement per atom) at about 700 °C in the Joyo. The change of the fracture toughness by the irradiation was correlated with nanostructural evolution by the irradiation, which was examined by transmission electron microscopy. The observed degradation of fracture toughness in Si_3N_4 is thought to be due to the relatively high density of small-sized of the irradiation induced defects, which should be resulted from a large amount of transmutation gases of hydrogen and helium. Observed improvement of fracture toughness in MgAl_2O_4 was due to the blocking of crack propagation by the antiphase boundaries. The radiation effects affected the fracture toughness of yttria stabilized zirconia at 55 dpa, suggesting that the generated high density voids would affect the propagation of cracks. - Highlights: • Si_3N_4, MgAl_2O_4 and YSZ were neutron irradiated up to 55dpa around 700 °C in the Joyo. • They are candidate ceramics for the inert matrices of nuclear fuels in the fast reactors. • The irradiation enhanced the fracture toughness of MgAl_2O_4 and YSZ, while degraded that of Si_3N_4. • The toughness changes were correlated with radiation induced defects and transmutation gases.

  6. Resolution of the reactor vessel materials toughness safety issue; Task Action Plan A-11; Appendices C-K

    International Nuclear Information System (INIS)

    Johnson, R.E.

    1981-09-01

    The central problem in the Unresolved Safety Issue A-11, 'Reactor Vessel Materials Toughness,' was to provide guidance in performing analyses for reactor pressure vessels (RPVs) which fail to meet the toughness requirements during service life as a result of neutron radiation embrittlement. A technical team of recognized experts was organized to assist the NRC staff in addressing the problem. Using the foundation of the tearing modulus concept, which has been developed under earlier NRC sponsorship, relationships were obtained which provided approximate solutions to the RPV fracture problem with assumed beltline region flaws. Volume I of this report is a brief presentation of the problem and the results; Volume II provides the detailed technical foundations

  7. Effects of minor Si on microstructures and room temperature fracture toughness of niobium solid solution alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Bin, E-mail: kongbin@buaa.edu.cn; Jia, Lina, E-mail: jialina@buaa.edu.cn; Su, Linfen, E-mail: sulinfen@mse.buaa.edu.cn; Guan, Kai, E-mail: guankai@mse.buaa.edu.cn; Weng, Junfei, E-mail: wengjf@mse.buaa.edu.cn; Zhang, Hu, E-mail: zhanghu@buaa.edu.cn

    2015-07-15

    Controlling the elements content in the niobium solid solution (Nb{sub SS}) is significant for the better comprehensive performance of Nb-silicide-based alloys. In this paper, the effects of minor Si on the microstructures and room temperature fracture toughness of Nb–(0/0.5/1/2)Si–27.63Ti–12.92Cr–2.07Al–1.12Hf (at%, unless stated otherwise) solid solution alloys were investigated. The alloys were processed by vacuum arc-casting (AC), and then heat treated (HT) at 1425 °C for 10 h. In HT alloys, Nb{sub SS} grains are refined gradually with the increase of Si content. Meanwhile, the volume fraction of Cr{sub 2}Nb and silicides phases precipitates increases. The fracture toughness of HT alloys decreases at first but then increases in the range of 0 to 2% Si, because it is a combinatorial process of positive and negative effects caused by the addition of Si. The refinement of Nb{sub SS} grains displays positive effect on fracture toughness, while the increase of solid solubility of Si in Nb{sub SS} and brittle Cr{sub 2}Nb and Nb-silicides precipitate phases display negative effect.

  8. Microhardness and fracture toughness of Ce0.9Gd0.1O1.95 for manufacturing solid oxide electrolytes

    International Nuclear Information System (INIS)

    Mangalaraja, R.V.; Ananthakumar, S.; Uma, Kasimayan; Jimenez, Romel M.; Lopez, Marta; Camurri, Carlos P.

    2009-01-01

    Synthesis of nanocrystalline gadolinium doped ceria (Ce 0.9 Gd 0.1 O 1.95 ) was attempted by nitrate-fuel combustion technique involving different organic fuels namely urea, citric acid, glycine and poly ethylene glycol. As-combusted ceria precursors were calcined at 700 deg. C for 2 h for obtaining fully dense, nanocrystalline ceria powders. Cylindrical ceria discs were fabricated by uni-axial pressing and sintered intentionally at low temperature of 1200 deg. C for 2 h for assessing the sintering characteristics of the nano powders as well as the mechanical performance of the sintered ceria body. The study confirms that the nano powders could be sintered to 98% theoretical sintered density at 1200 deg. C with a grain size of 400 nm to 1 μm. The sintered samples exhibited the Vickers microhardness of 8.82 ± 0.2 GPa and the fracture toughness of 1.75 ± 0.3 MPa m 1/2 at a load 20 N for glycine and citric acid fuels derived ceria, respectively. A comparison between the fuels was made with respect to the sintering and mechanical properties of doped ceria. Citric acid and glycine fuels resulted in sintered ceria with high hardness where as the urea and polyethylene fuels derived nano ceria resulted in high fracture toughness.

  9. Multiscale deformations lead to high toughness and circularly polarized emission in helical nacre-like fibres.

    Science.gov (United States)

    Zhang, Jia; Feng, Wenchun; Zhang, Huangxi; Wang, Zhenlong; Calcaterra, Heather A; Yeom, Bongjun; Hu, Ping An; Kotov, Nicholas A

    2016-02-24

    Nacre-like composites have been investigated typically in the form of coatings or free-standing sheets. They demonstrated remarkable mechanical properties and are used as ultrastrong materials but macroscale fibres with nacre-like organization can improve mechanical properties even further. The fiber form or nacre can, simplify manufacturing and offer new functional properties unknown yet for other forms of biomimetic materials. Here we demonstrate that nacre-like fibres can be produced by shear-induced self-assembly of nanoplatelets. The synergy between two structural motifs--nanoscale brick-and-mortar stacking of platelets and microscale twisting of the fibres--gives rise to high stretchability (>400%) and gravimetric toughness (640 J g(-1)). These unique mechanical properties originate from the multiscale deformation regime involving solid-state self-organization processes that lead to efficient energy dissipation. Incorporating luminescent CdTe nanowires into these fibres imparts the new property of mechanically tunable circularly polarized luminescence. The nacre-like fibres open a novel technological space for optomechanics of biomimetic composites, while their continuous spinning methodology makes scalable production realistic.

  10. Degradation of safety injection system and containment spray piping and tank fracture toughness analysis

    International Nuclear Information System (INIS)

    Douglas, A.; Doubel, P.; Wicker, C.

    2011-01-01

    Extensive stress corrosion cracking (SCC), induced by the marine environment and the presence of high residual stresses arising from the respective manufacturing processes has been encountered in the safety injection system piping (RIS), containment spray system piping (EAS) and reactor and spent fuel storage tank (PTR), or refuelling water storage tank (RWST) of the Koeberg plant. Type 304L steels from the RIS system and replacement components for the RIS and RWST systems have been subject to mechanical and fracture toughness testing. The following conclusions have been drawn. -) The piping sections of both the original and replacement components exhibit residual cold work. The level of cold work imparted to the piping and elbow have been estimated to be 2, 2 to 3, 9% and 5, 7 to 7, 3% respectively. -) Re-annealing produces different responses in type 304L as a function of prior cold work level. Re-annealing of material cold worked to low levels i.e. 3.5% maintain the cold worked level of UTS but can exhibit 0, 2% PS. levels below that of the mill annealed condition. There is the potential for the ASTM A312 minimum 0, 2% level to be breached. At higher levels of cold work i.e. 7% re-annealing results in extensive grain growth, a significant reduction in 0, 2% PS from the mill annealed condition and the recovery of the UTS to the mill annealed level. -) Cold work at the levels obtained significantly reduces the SOL initiation toughness Ji. The reduction in toughness can be greater than 50%. The resistance to ductile crack propagation, dJ/da, remains unchanged at least up to 5 % cold work. -) The defect assessment for the RIS/EAS systems have used highly conservative values of initiation toughness such that no crack initiation would occur under the loading conditions considered and in a non-hostile environment. -) Under the marine environment to which the RIS/EAS components are still subjected, the limiting criterion for operation of the RIS/EAS system remains a

  11. Controlling coaching and athlete thriving in elite adolescent netballers: The buffering effect of athletes' mental toughness.

    Science.gov (United States)

    Gucciardi, Daniel F; Stamatis, Andreas; Ntoumanis, Nikos

    2017-08-01

    The purposes of this study were to examine the association between controlling coach behaviours and athlete experiences of thriving and test the buffering effect of mental toughness on this relation. A cross-sectional survey. In total, 232 female netballers aged 11 to 17 years (14.97+1.52) with between 1 and 15 years of experience in their sport (7.50+2.28) completed measures of controlling coach interpersonal style, mental toughness and thriving. Latent moderated structural models indicated that (i) controlling coach behaviours were inversely related with experiences of vitality and learning; (ii) mental toughness was positively associated with psychological experiences of both dimensions of thriving; and (iii) mental toughness moderated the effect of coach's controlling interpersonal style on learning but not vitality experiences, such that the effect was weaker for individuals who reported higher levels of mental toughness. This study extends past work and theory to show that mental toughness may enable athletes to counteract the potentially deleterious effect of controlling coach interpersonal styles. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  12. 3D Voronoi grid dedicated software for modeling gas migration in deep layered sedimentary formations with TOUGH2-TMGAS

    Science.gov (United States)

    Bonduà, Stefano; Battistelli, Alfredo; Berry, Paolo; Bortolotti, Villiam; Consonni, Alberto; Cormio, Carlo; Geloni, Claudio; Vasini, Ester Maria

    2017-11-01

    As is known, a full three-dimensional (3D) unstructured grid permits a great degree of flexibility when performing accurate numerical reservoir simulations. However, when the Integral Finite Difference Method (IFDM) is used for spatial discretization, constraints (arising from the required orthogonality between the segment connecting the blocks nodes and the interface area between blocks) pose difficulties in the creation of grids with irregular shaped blocks. The full 3D Voronoi approach guarantees the respect of IFDM constraints and allows generation of grids conforming to geological formations and structural objects and at the same time higher grid resolution in volumes of interest. In this work, we present dedicated pre- and post-processing gridding software tools for the TOUGH family of numerical reservoir simulators, developed by the Geothermal Research Group of the DICAM Department, University of Bologna. VORO2MESH is a new software coded in C++, based on the voro++ library, allowing computation of the 3D Voronoi tessellation for a given domain and the creation of a ready to use TOUGH2 MESH file. If a set of geological surfaces is available, the software can directly generate the set of Voronoi seed points used for tessellation. In order to reduce the number of connections and so to decrease computation time, VORO2MESH can produce a mixed grid with regular blocks (orthogonal prisms) and irregular blocks (polyhedron Voronoi blocks) at the point of contact between different geological formations. In order to visualize 3D Voronoi grids together with the results of numerical simulations, the functionality of the TOUGH2Viewer post-processor has been extended. We describe an application of VORO2MESH and TOUGH2Viewer to validate the two tools. The case study deals with the simulation of the migration of gases in deep layered sedimentary formations at basin scale using TOUGH2-TMGAS. A comparison between the simulation performances of unstructured and structured

  13. Investigation on fracture toughness of laser beam welded steels

    International Nuclear Information System (INIS)

    Riekehr, S.; Cam, G.; Santos, J.F. dos; Kocak, M.; Klein, R.M.; Fischer, R.

    1999-01-01

    Laser beam welding is currently used in the welding of a variety of structural materials including hot and cold rolled steels, high strength low alloy and stainless steels, aluminium and titanium alloys, refractory and high temperature alloys and dissimilar materials. This high power density welding process has unique advantages of cost effectiveness, low distortion, high welding speed, easy automation, deep penetration, narrow bead width, and narrow HAZ compared to the conventional fusion welding processes. However, there is a need to understand the deformation and fracture properties of laser beam weld joints in order to use this cost effective process for fabrication of structural components fully. In the present study, an austenitic stainless steel, X5CrNi18 10 (1.4301) and a ferritic structural steel, RSt37-2 (1.0038), with a thickness of 4 mm were welded by 5 kW CO 2 laser process. Microhardness measurements were conducted to determine the hardness profiles of the joints. Flat micro-tensile specimens were extracted from the base metal, fusion zone, and heat affected zone of ferritic joint to determine the mechanical property variation across the joint and the strength mismatch ratio between the base metal and the fusion zone. Moreover, fracture mechanics specimens were extracted from the joints and tested at room temperature to determine fracture toughness, Crack Tip Opening Displacement (CTOD), of the laser beam welded specimens. The effect of the weld region strength mis-matching on the fracture toughness of the joints have been evaluated. Crack initiation, crack growth and crack deviation processes have also been examined. These results were used to explain the influence of mechanical heterogeneity of the weld region on fracture behaviour. This work is a part of the ongoing Brite-Euram project Assessment of Quality of Power Beam Weld Joints (ASPOW). (orig.)

  14. Development of CSS-42L{trademark}, a high performance carburizing stainless steel for high temperature aerospace applications

    Energy Technology Data Exchange (ETDEWEB)

    Burrier, H.I.; Milam, L. [Timken Co., Canton, OH (United States); Tomasello, C.M.; Balliett, S.A.; Maloney, J.L. [Latrobe Steel Co., Latrobe, PA (United States); Ogden, W.P. [MPB Corp., Lebanon, NH (United States)

    1998-12-31

    Today`s aerospace engineering challenges demand materials which can operate under conditions of temperature extremes, high loads and harsh, corrosive environments. This paper presents a technical overview of the on-going development of CSS-42L (US Patent No. 5,424,028). This alloy is a case-carburizable, stainless steel alloy suitable for use in applications up to 427 C, particularly suited to high performance rolling element bearings, gears, shafts and fasteners. The nominal chemistry of CSS-42L includes: (by weight) 0.12% carbon, 14.0% chromium, 0.60% vanadium, 2.0% nickel, 4.75% molybdenum and 12.5% cobalt. Careful balancing of these components combined with VIM-VAR melting produces an alloy that can be carburized and heat treated to achieve a high surface hardness (>58 HRC at 1mm (0.040 in) depth) with excellent corrosion resistance. The hot hardness of the carburized case is equal to or better than all competitive grades, exceeding 60 HRC at 427 C. The fracture toughness and impact resistance of the heat treated core material have likewise been evaluated in detail and found to be better than M50-NiL steel. The corrosion resistance has been shown to be equivalent to that of 440C steel in tests performed to date.

  15. Improvement of strength and toughness of SKD11 type cold work tool steel; SKD 11 gata reikan koguko no kyojinsei no kaizen

    Energy Technology Data Exchange (ETDEWEB)

    Fukaura, K.; Sunada, H.; Yokoyama, Y. [Himeji Inst. of Technology, Hyogo (Japan); Teramoto, K. [Himeji Inst. of Technology, Hyogo (Japan). Graduate School| Sanyo Special Steel Co. Ltd., Hyogo (Japan)

    1998-03-01

    Toughness and wear resistance are the factors which affect on the lifetime of cold work tool steels importantly. Generally, both properties show the contrary characteristics. The evaluation of tool steel materials has been carried out focusing on the strength and wear resistance mainly. However, owing to the rapid progress of recent plastic working techniques, usage environments are under the severe conditions more and more. Therefore, it is expected to develop the high reliable cold work tool steels which balanced with toughness including wear resistance. In this study, the strength and toughness of a newly developed 0.8C-8Cr cold work tool steel whose composition was controlled to suppress the precipitation of massive eutectic M7C3 carbides were investigated with reference to microstructure and were compared with conventional SKD11. The toughness was evaluated by the area under the stress-strain curve. As a result, it was clarified that the tensile strength of the newly developed steel designated as Mod. SKD 11 was about 400 MPa higher and the toughness was 1.8 times larger than that of SKD 11 throughout a wide range of tempering temperatures and so forth. 17 refs., 13 figs., 1 tab.

  16. Evaluation of fracture toughness for metal/ceramics composite materials by means of miniaturized specimen technique

    International Nuclear Information System (INIS)

    Saito, Masahiro; Takahashi, Hideaki; Jeong, Hee-Don; Kawasaki, Akira; Watanabe, Ryuzo

    1991-01-01

    In order to evaluate fracture strength for Y 2 O 3 -ZrO 2 , 3 mol% Y 2 O 3 -ZrO 2 (PSZ)/SUS 304 composite materials, Macor as a machinable ceramics and comercially available ceramics (SiC, Si 3 N 4 , PSZ, Al 2 O 3 ), fracture toughness tests were carried out by use of RCT or bending specimens. On the other hand, the fracture strength of these materials was evaluated and inspected the correlation between fracture toughness and fracture stress of small punch (SP) or modified small punch (MSP) test data to predict the fracture toughness value by using miniaturized specimens. Characteristic of the MSP testing method is the ability to evaluate elastic modulus (Young's modulus), fracture strength, yield strength, fracture strain, and fracture energy, etc., with high accuracy and good reproducibility for brittle materials. For a series of metal/ ceramics composites which from ductile to brittle, this paper clarified clear the applicable range for SP and MSP testing methods, which suggested that the simultaneous use of SP and MSP test methods can evaluate the fracture strength of metal/ ceramics composites. (author)

  17. Fracture toughness measurements of WC-based hard metals

    International Nuclear Information System (INIS)

    Prakash, L.; Albert, B.

    1983-01-01

    The fracture toughness of WC-based cemented carbides was determined by different methods. The values obtained are dependent on the procedure of measurement. Each method thoughness of hard metals mutually. (orig.) [de

  18. Analysis of size effect applicable to evaluation of fracture toughness of base metal for PWR vessel

    International Nuclear Information System (INIS)

    Benhamou, C.; Joly, P.; Andrieu, A.; Parrot, A.; Vidard, S.

    2015-01-01

    The objective of the present paper is to review the specimen size effect (also called crack front length effect) on Fracture Toughness of PWR Reactor Pressure Vessel Steel base metal. The analysis of the reality and amplitude of this effect is conducted in a first step on a database (the so-called GKSS database) including fracture toughness test results on a single representative material using specimens of different thicknesses, tested in the same temperature range. A realistic analytical form for describing the size effect observed in this data set is thus derived from statistical analyses and proposed for engineering application. In a second step, this size effect formulation is then applied to a large number of fracture toughness data, obtained in Irradiation Surveillance Programs, and also to the numerous data used for the definition of the ASME (and RCC-M) fracture toughness reference curves. This analysis allows normalizing all the available fracture toughness data with a single specimen width of 100 mm and defining the fracture toughness reference curve as the lower bound of this normalized set of data points. It is thus demonstrated that the fracture toughness reference curve is associated with a reference crack length of 100 mm, and can be used in RPV integrity analyses for other crack front length in association with the crack front length correction formula defined in the first step. (authors)

  19. Notch constraint effects on the dynamic fracture toughness of an unaged beta titanium alloy

    International Nuclear Information System (INIS)

    Rack, H.J.

    1975-01-01

    The influence of notch included angle and root radius on the apparent dynamic fracture toughness of an unaged metastable beta titanium alloy, Ti--3Al--8V--6Cr--4Zr--4Mo, has been examined. The apparent fracture toughness, K/sub Id/(rho), increases with both notch radius, rho and included angle, ω. These results have been compared with the theoretical predictions of Tetelman, et al. and Smith. The comparisons show that neither theory accurately describes the effect of varying notch constraint on the apparent dynamic fracture toughness. Although preliminary considerations indicate that qualitative descriptions of notch acuity effects may be given by recent finite element analysis of the stress and strain distributions below a notch root, there is presently no quantitative basis for determining the true dynamic fracture toughness of materials from the results of blunt notch experiments. (auth)

  20. Development of the transverse tensile and fracture toughness test techniques for spent fuel cladding

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, S. B.; Hong, K. P.; Jung, Y. H.; Seo, H. S.; Oh, W. H.; Yoo, B. O.; Kim, D. S.; Seo, K. S

    2001-12-01

    To define the cause of cladding damage which can take place during the operation of nuclear power plant and the storage through the degradation aspect of mechanical characteristics, the transverse tensile an fracture toughness test were developed in hot cell at IMEF(Irradiated Material Experiment Facility). The following hot cell techniques were developed. 1. The development of a jig and a specimen for transverse tensile test 2. The acquisition of a manufacturing technique for the transverse tensile specimen at hot cell 3. The acquisition of testing procedures and an analysis technque for the transverse tensile 4. The dimensional determination of an optimized fracture toughness specimen 5. The acquisition of manufacturing technique for the fracture toughness test specimen at the hot cell 6. The acquisition of testing procedures and analysis technique for the fracture toughness test (Multiple specimen method, DCPD method, Load ratio method)

  1. The effect of electric discharge machined notches on the fracture toughness of several structural alloys

    International Nuclear Information System (INIS)

    Joyce, J.A.; Link, R.E.

    1993-09-01

    Recent computational studies of the stress and strain fields at the tip of very sharp notches have shown that the stress and strain fields are very weakly dependent on the initial geometry of the notch once the notch has been blunted to a radius that is 6 to 10 times the initial root radius. It follows that if the fracture toughness of a material is sufficiently high so that fracture initiation does not occur in a specimen until the crack-tip opening displacement (CTOD) reaches a value from 6 to 10 times the size of the initial notch tip diameter, then the fracture toughness will be independent of whether a fatigue crack or a machined notch served as the initial crack. In this experimental program the fracture toughness (J Ic and J resistance (J-R) curve, and CTOD) for several structure alloys was measured using specimens with conventional fatigue cracks and with EDM machined notches. The results of this program have shown, in fact, that most structural materials do not achieve initiation CTOD values on the order of 6 to 10 times the radius of even the smallest EDM notch tip presently achievable. It is found furthermore that tougher materials do not seem to be less dependent on the type of notch tip present. Some materials are shown to be much more dependent on the type of notch tip used, but no simple pattern is found that relates this observed dependence to the material strength toughness, or strain hardening rate

  2. Conductive, tough, hydrophilic poly(vinyl alcohol)/graphene hybrid fibers for wearable supercapacitors

    Science.gov (United States)

    Chen, Shaohua; Ma, Wujun; Xiang, Hengxue; Cheng, Yanhua; Yang, Shengyuan; Weng, Wei; Zhu, Meifang

    2016-07-01

    Graphene fibers based flexible supercapacitors have great potential as wearable power sources for textile electronics. However, their electrochemical performance is limited by the serious stacking of graphene sheets and their hydrophobicity in aqueous electrolytes. Meanwhile, their brittleness is unfavorable for practical application. Incorporation of nanofillers into graphene fibers has been proved effective for enhancing their capacitance, whereas often leading to deteriorated mechanical strength. Herein we demonstrate that the strength, toughness and capacitive performance of graphene-based fibers can be significantly enhanced simultaneously, simply by incorporating hydrophilic poly(vinyl alcohol) (PVA) into a non-liquid-crystalline graphene oxide (GO) dispersion before wet spinning and chemical reduction. The structure and properties of the resulted PVA/graphene hybrid fibers are systematically investigated, and the mechanism behind these enhancements is discussed in detail. The hybrid fiber with a PVA/GO weight ratio of 10/90 possesses a strength of 186 MPa, a toughness of 11.3 J cm-3, and a capacitance of 241 F cm-3 in 1 M H2SO4. A solid-state yarn supercapacitor assembled from these fibers exhibits a device energy of 5.97 mW h cm-3, and features excellent flexibility and bending stability. This device is robust enough to be integrated into textile and thus promising as wearable power supply for smart textiles.

  3. Influence of hydrogen content on fracture toughness of CWSR Zr-2.5Nb pressure tube alloy

    Science.gov (United States)

    Singh, R. N.; Bind, A. K.; Srinivasan, N. S.; Ståhle, P.

    2013-01-01

    In this work, influence of hydrogen and temperature on the fracture toughness parameters of unirradiated, cold worked and stress relieved (CWSR) Zr-2.5Nb pressure tube alloys used in Indian Pressurized Heavy Water Reactor is reported. The fracture toughness tests were carried out using 17 mm width curved compact tension specimens machined from gaseously hydrogen charged tube-sections. Metallography of the samples revealed that hydrides were predominantly oriented along axial-circumferential plane of the tube. Fracture toughness tests were carried out in the temperature range of 30-300 °C as per ASTM standard E-1820-06, with the crack length measured using direct current potential drop (DCPD) technique. The fracture toughness parameters (JQ, JMax and dJ/da), were determined. The critical crack length (CCL) for catastrophic failure was determined using a numerical method. It was observed that for a given test temperature, the fracture toughness parameters representing crack initiation (JQ) and crack propagation (JMax, and dJ/da) is practically unaffected by hydrogen content. Also, for given hydrogen content, all the aforementioned fracture toughness parameters increased with temperature to a saturation value.

  4. Fracture toughness and fatigue crack propagation in cast irons with spheroidal vanadium carbides dispersed within martensitic matrix microstructure

    International Nuclear Information System (INIS)

    Uematsu, Y.; Tokaji, K.; Horie, T.; Nishigaki, K.

    2007-01-01

    Fracture toughness and fatigue crack propagation (FCP) have been studied using compact tension (CT) specimens of as-cast and subzero-treated materials in a cast iron with spheroidal vanadium carbides (VCs) dispersed in the martensitic matrix microstructure. X-ray diffraction (XRD) analysis revealed that retained austenite was transformed to martensite by subzero treatment. Vickers hardness was increased from 738 for the as-cast material to 782 for the subzero-treated material, which could be attributed to retained austenite to martensite transformation. The subzero-treated material exhibited lower fracture toughness than the as-cast material because soft and ductile retained austenite which possesses high fracture toughness was transformed to martensite in the subzero-treated material. Intrinsic FCP resistance after taking account of crack closure was decreased by the subzero treatment, which was attributed to the predominant crack propagation through the interface between VCs and the matrix and the straight crack path in the matrix microstructure

  5. Anisotropic toughness and strength in graphene and its atomistic origin

    Science.gov (United States)

    Hossain, M. Zubaer; Ahmed, Tousif; Silverman, Benjamin; Khawaja, M. Shehroz; Calderon, Justice; Rutten, Andrew; Tse, Stanley

    2018-01-01

    This paper presents the implication of crystallographic orientation on toughness and ideal strength in graphene under lattice symmetry-preserving and symmetry-breaking deformations. In symmetry-preserving deformation, both toughness and strength are isotropic, regardless of the chirality of the lattice; whereas, in symmetry-breaking deformation they are strongly anisotropic, even in the presence of vacancy defects. The maximum and minimum of toughness or strength occur for loading along the zigzag direction and the armchair direction, respectively. The anisotropic behavior is governed by a complex interplay among bond-stretching deformation, bond-bending deformation, and the chirality of the lattice. Nevertheless, the condition for crack-nucleation is dictated by the maximum bond-force required for bond rupture, and it is independent of the chiral angle of the lattice or loading direction. At the onset of crack-nucleation a localized nucleation zone is formed, wherein the bonds rupture locally satisfying the maximum bond-force criterion. The nucleation zone acts as the physical origin in triggering the fracture nucleation process, but its presence is undetectable from the macroscopic stress-strain data.

  6. Fracture toughness of the F-82H steel-effect of loading modes, hydrogen, and temperature

    International Nuclear Information System (INIS)

    Li, H.-X.; Jones, R.H.; Hirth, J.P.; Gelles, D.S.

    1996-01-01

    The effects of loading mode, hydrogen, and temperature on fracture toughness and tearing modulus were examined for a ferritic/martensitic steel (F-82H). The introduction of a shear load component, mode III, significantly decreased the initiation and propagation resistance of cracks compared to the opening load, mode I, behavior. Mode I crack initiation and propagation exhibited the highest resistance. A minimum resistance occurred when the mode I and mode III loads were nearly equal. The presence of 4 wppm hydrogen decreased the cracking resistance compared to behavior without H regardless of the loading mode. The minimum mixed-mode fracture toughness with the presence of hydrogen was about 30% of the hydrogen-free mode I fracture toughness. The mixed-mode toughness exhibited a lesser sensitivity to temperature than the mode I toughness. The J IC value was 284 kJ/m 2 at room temperature, but only 60 kJ/m 2 at -55 C and 30 kJ/m 2 at -90 C. The ductile to brittle transition temperature (DBTT) was apparently higher than -55 C. (orig.)

  7. Transforming Anaerobic Adhesives into Highly Durable and Abrasion Resistant Superhydrophobic Organoclay Nanocomposite Films: A New Hybrid Spray Adhesive for Tough Superhydrophobicity

    Science.gov (United States)

    Bayer, Ilker S.; Brown, Andrea; Steele, Adam; Loth, Eric

    2009-12-01

    The authors report fabrication of tough nanostructured self-cleaning superhydrophobic polymer-organoclay films from anaerobic acrylic adhesives displaying strong adhesion to metal surfaces. Both industrial and bio-grade anaerobic adhesives such as bone cements could be used. Montmorillonite clay filled anaerobic adhesives were modified by blending with a water dispersed fluoro-methacrylic latex in solution to form abrasion resistant interpenetrating polymer network films upon spray casting. The adhesive films could cure by thermosetting in oxygen-rich environments. Very high contact angles with low hysteresis were also measured for acidic (pH 2) and basic (pH 11) aqueous buffer solutions indicating resistance to acidic and basic media.

  8. Influence of PWHT on Toughness of High Chromium and Nickel Containing Martensitic Stainless Steel Weld Metals

    Science.gov (United States)

    Divya, M.; Das, Chitta Ranjan; Mahadevan, S.; Albert, S. K.; Pandian, R.; Kar, Sujoy Kumar; Bhaduri, A. K.; Jayakumar, T.

    2015-06-01

    Commonly used 12.5Cr-5Ni consumable specified for welding of martensitic stainless steels is compared with newly designed 14.5Cr-5Ni consumable in terms of their suitability for repair welding of 410 and 414 stainless steels by gas tungsten arc welding process. Changes in microstructure and austenite evolution were investigated using optical, scanning electron microscopy, X-ray diffraction techniques and Thermo-Calc studies. Microstructure of as-welded 12.5Cr-5Ni weld metal revealed only lath martensite, whereas as-welded 14.5Cr-5Ni weld metal revealed delta-ferrite, retained austenite, and lath martensite. Toughness value of as-welded 12.5Cr-5Ni weld metal is found to be significantly higher (216 J) than that of the 14.5Cr-5Ni weld metal (15 J). The welds were subjected to different PWHTs: one at 923 K (650 °C) for 1, 2, 4 hours (single-stage PWHT) and another one at 923 K (650 °C)/4 h followed by 873 K (600 °C)/2 h or 873 K (600 °C)/4 h (two-stage heat treatment). Hardness and impact toughness of the weld metals were measured for these weld metals and correlated with the microstructure. The study demonstrates the importance of avoiding formation of delta-ferrite in the weld metal.

  9. Postirradiation fracture toughness of Inconel X-750

    International Nuclear Information System (INIS)

    Mills, W.J.

    1983-01-01

    The effect of fast-neutron irradiation on the fracture toughness response of Inconel X-750 was characterized at 427 deg C using the J-R curve technique. Irradiation exposures ranging from 3 to 16 displacements per atom resulted in a reduction in Jsub(Ic) from 130 to 76 kJ/m 2 and a reduction in tearing modulus from 32 to 2.6. Postirradiation fractographic examination revealed that an intergranular fracture mechanism was dominant, in contrast to the extensive transgranular cracking mode found on unirradiated fracture surfaces. The enhanced intergranular failure observed after irradiation was caused by extensive heterogeneous slip in a matrix that was greatly strengthened by an irradiation-induced dislocation substructure. Specifically, intense planar slip bands impinged on the grain boundaries and generated large stress concentrations. Since the stress concentrations could not be relaxed by the hardened matrix, the grain boundaries 'unzipped' readily, resulting in the low toughness and tearing resistance. (author)

  10. Effect of delaminations on improvement of notch toughness at low temperatures

    International Nuclear Information System (INIS)

    Zhou, W.; Loh, N.L.

    1996-01-01

    The notched-bar impact test is often used to assess the notch toughness of engineering materials. The principle of the test is that a material absorbs a certain amount of energy when it breaks; the energy thus absorbed is an indication of the material's resistance to impact fracture. If the material is brittle, it breaks easily with a small amount of absorbed energy. If it is tough, it will absorb more energy to fracture. It has been well recognized that most engineering materials undergo a transition from notch tough to notch brittle behavior when the temperature is reduced. In the present study, however, an abnormal trend in the transition behavior was found for an austenitic stainless steel. V-notched specimens of the steel were tested under impact loading in a wide temperature range from -196 C to room temperature. Contrary to expectation, the impact energy values obtained at low temperatures were found to be much higher than those obtained at room temperature, indicating that the steel became tougher rather than more brittle when the test temperature was lowered. This intriguing phenomenon cannot be explained simply according to the tensile stress fracture criterion. Strong evidence has been obtained in the present study to show that the improvement of notch toughness at low temperatures is caused by delaminations

  11. The Opportunity for High-Performance Biomaterials from Methane

    Directory of Open Access Journals (Sweden)

    Peter James Strong

    2016-02-01

    Full Text Available Polyhydroxyalkanoate (PHA biopolymers are widely recognised as outstanding candidates to replace conventional petroleum-derived polymers. Their mechanical properties are good and can be tailored through copolymer composition, they are biodegradable, and unlike many alternatives, they do not rely on oil-based feedstocks. Further, they are the only commodity polymer that can be synthesised intracellularly, ensuring stereoregularity and high molecular weight. However, despite offering enormous potential for many years, they are still not making a significant impact. This is broadly because commercial uptake has been limited by variable performance (inconsistent polymer properties and high production costs of the raw polymer. Additionally, the main type of PHA produced naturally is poly-3-hydroxybutyrate (PHB, which has limited scope due to its brittle nature and low thermal stability, as well as its tendency to embrittle over time. Production cost is strongly impacted by the type of the feedstock used. In this article we consider: the production of PHAs from methanotrophs using methane as a cost-effective substrate; the use of mixed cultures, as opposed to pure strains; and strategies to generate a poly(3-hydroxybutyrate-co-3-hydroxyvalerate copolymer (PHBV, which has more desirable qualities such as toughness and elasticity.

  12. Review on "BBS Are Our Kids Tough Enough: Chinese Schools" Based on History, Literature and Personal Experience

    Science.gov (United States)

    Zhao, Yiran

    2015-01-01

    The aim behind this article is to clear up some misunderstandings about British and Chinese education approaches in the popular BBC documentary "Are our kids tough enough: Chinese Schools". The article evaluates the differences in academic performance, class disciplines and education values of two education practices that have caused…

  13. A turbulent transport network model in MULTIFLUX coupled with TOUGH2

    International Nuclear Information System (INIS)

    Danko, G.; Bahrami, D.; Birkholzer, J.T.

    2011-01-01

    A new numerical method is described for the fully iterated, conjugate solution of two discrete submodels, involving (a) a transport network model for heat, moisture, and airflows in a high-permeability, air-filled cavity; and (b) a variably saturated fractured porous medium. The transport network submodel is an integrated-parameter, computational fluid dynamics solver, describing the thermal-hydrologic transport processes in the flow channel system of the cavity with laminar or turbulent flow and convective heat and mass transport, using MULTIFLUX. The porous medium submodel, using TOUGH2, is a solver for the heat and mass transport in the fractured rock mass. The new model solution extends the application fields of TOUGH2 by integrating it with turbulent flow and transport in a discrete flow network system. We present demonstrational results for a nuclear waste repository application at Yucca Mountain with the most realistic model assumptions and input parameters including the geometrical layout of the nuclear spent fuel and waste with variable heat load for the individual containers. The MULTIFLUX and TOUGH2 model elements are fully iterated, applying a programmed reprocessing of the Numerical Transport Code Functionalization model-element in an automated Outside Balance Iteration loop. The natural, convective airflow field and the heat and mass transport in a representative emplacement drift during postclosure are explicitly solved in the new model. The results demonstrate that the direction and magnitude of the air circulation patterns and all transport modes are strongly affected by the heat and moisture transport processes in the surrounding rock, justifying the need for a coupled, fully iterated model solution such as the one presented in the paper.

  14. Acoustic emission characterization of fracture toughness for fiber reinforced ceramic matrix composites

    International Nuclear Information System (INIS)

    Mei, Hui; Sun, Yuyao; Zhang, Lidong; Wang, Hongqin; Cheng, Laifei

    2013-01-01

    The fracture toughness of a carbon fiber reinforced silicon carbide composite was investigated relating to classical critical stress intensity factor K IC , work of fracture, and acoustic emission energy. The K IC was obtained by the single edge notch beam method and the work of fracture was calculated using the featured area under the load–displacement curves. The K IC , work of fracture, and acoustic emission energy were compared for the composites before and after heat treatment and then analyzed associated with toughening microstructures of fiber pullout. It indicates that the work of fracture and acoustic emission energy can be more suitable to reflect the toughness rather than the traditional K IC , which has certain limitation for the fracture toughness characterization of the crack tolerant fiber ceramic composites.

  15. Evolution: Weevils Get Tough on Symbiotic Tyrosine.

    Science.gov (United States)

    Dale, Colin

    2017-12-04

    Weevils, which represent one of the most diverse groups of terrestrial insects in nature, obtain a tough exoskeleton through the activity of an ancient bacterial symbiont with a tiny genome that serves as a factory for the production of tyrosine. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Mode II Interlaminar Fracture Toughness and Fatigue Characterization of a Graphite Epoxy Composite Material

    Science.gov (United States)

    O'Brien, T. Kevin; Johnston, William M.; Toland, Gregory J.

    2010-01-01

    Mode II interlaminar fracture toughness and delamination onset and growth characterization data were generated for IM7/8552 graphite epoxy composite materials from two suppliers for use in fracture mechanics analyses. Both the fracture toughness testing and the fatigue testing were conducted using the End-notched Flexure (ENF) test. The ENF test for mode II fracture toughness is currently under review by ASTM as a potential standard test method. This current draft ASTM protocol was used as a guide to conduct the tests on the IM7/8552 material. This report summarizes the test approach, methods, procedures and results of this characterization effort.

  17. Fracture Toughness, Mechanical Property, And Chemical Characterization Of A Critical Modification To The NASA SLS Solid Booster Internal Material System

    Science.gov (United States)

    Pancoast, Justin; Garrett, William; Moe, Gulia

    2015-01-01

    A modified propellant-liner-insulation (PLI) bondline in the Space Launch System (SLS) solid rocket booster required characterization for flight certification. The chemical changes to the PLI bondline and the required additional processing have been correlated to mechanical responses of the materials across the bondline. Mechanical properties testing and analyses included fracture toughness, tensile, and shear tests. Chemical properties testing and analyses included Fourier transform infrared (FTIR) spectroscopy, cross-link density, high-performance liquid chromatography (HPLC), gas chromatography (GC), gel permeation chromatography (GPC), and wave dispersion X-ray fluorescence (WDXRF). The testing identified the presence of the expected new materials and found the functional bondline performance of the new PLI system was not significantly changed from the old system.

  18. Role of specimen size upon the measured toughness of cellular solids

    International Nuclear Information System (INIS)

    Christodoulou, I; Tan, P J

    2013-01-01

    It is well known that the mechanical properties of cellular solids depend critically upon the specimen size and that a 'sufficiently' large test specimen is needed to obtain representative bulk values. Notwithstanding, the fracture toughness of cellular solids is still measured experimentally based on standards, such as the ASTM E399 and E813, developed for solid materials that do not possess an intermediate, 'cell-level' length scale. Experimental data in the literature appears to show that the toughness of stochastic 3D foams is, also, size-dependent. This paper presents the results of a detailed finite element (FE) study that will quantify, and identify the physical origin of, the size-dependent effect. Three-point bending of a single-edge notched (or SEN(B)) specimen, with a 2D Voronoi micro-architecture, is modelled numerically to obtain estimates of fracture toughness which are compared to those obtained with a 'boundary-layer' analysis

  19. J/sub 1c/ fracture toughness transition behavior of HT-9

    International Nuclear Information System (INIS)

    Huang, F.H.

    1984-01-01

    Small compact tension specimens of two heats of HT-9 were tested at temperatures ranging from room temperature to -192 0 C. The ductile-brittle transition toughness of HT-9 was evaluated using the J-integral approach. There were two loading rates of 2.1 x 10 -5 m/s and 3.2 x 10 -2 m/s. The ductile-brittle transition temperatures of HT-9 (number 1 heat) tested at 2.1 x 10 -5 m/s and HT-9 (number 2 heat) tested at 3.2 x 10 -2 m/s were found to be -60 and -10 0 C, respectively. Results showed the fracture toughness of the former was not sensitive to loading rate and the lower shelf toughness decreased with temperature to a J/sub 1c/ value of 5 kJ/m 2 at -190 0 C. Furthermore, the values of J/sub 1c/ were valid since the thickness of the test specimens was well above the thickness criterion

  20. Influence of Post-Weld Heat Treatment on the Microstructure, Microhardness, and Toughness of a Weld Metal for Hot Bend

    Directory of Open Access Journals (Sweden)

    Xiu-Lin Han

    2016-03-01

    Full Text Available In this work, a weld metal in K65 pipeline steel pipe has been processed through self-designed post-weld heat treatments including reheating and tempering associated with hot bending. The microstructures and the corresponding toughness and microhardness of the weld metal subjected to the post-weld heat treatments have been investigated. Results show that with the increase in reheating temperature, austenite grain size increases and the main microstructures transition from fine polygonal ferrite (PF to granular bainitic ferrite (GB. The density of the high angle boundary decreases at higher reheating temperature, leading to a loss of impact toughness. Lots of martensite/austenite (M/A constituents are observed after reheating, and to a large extent transform into cementite after further tempering. At high reheating temperatures, the increased hardenability promotes the formation of large quantities of M/A constituents. After tempering, the cementite particles become denser and coarser, which considerably deteriorates the impact toughness. Additionally, microhardness has a good linear relation with the mean equivalent diameter of ferrite grain with a low boundary tolerance angle (2°−8°, which shows that the hardness is controlled by low misorientation grain boundaries for the weld metal.

  1. Effect of Temperature on the Toughness of Locally Manufactured Low Alloy Steel SUP9 Used for Manufacturing Leaf Springs

    Directory of Open Access Journals (Sweden)

    Muhammad Ishaque Abro

    2011-10-01

    Full Text Available The effect of heat treatment on locally manufactured low alloy steel grade SUP9 most frequently used in making leaf springs for automobiles was studied. While for determination of toughness and hardness Charpy impact testing machine and Rockwell hardness tester were used. The cryogenic test temperatures were achieved by soaking the samples in liquid nitrogen and temperature was measured using digital thermometer capable of reading the temperature from -40-200oC. Hardening, tempering and austempering treatments were conducted using muffle furnace and salt bath furnace. After heat treatment samples were quenched in oil. The results of present work confirmed that toughness and hardness are inversely related with each other and are highly dependent on the type of heat treatment employed. Highest toughness was measured after austempering at 450oC. Effect of test temperature revealed that toughness of the samples increased significantly with decreasing temperature. DBTT (Ductile to Brittle Transition Temperature of the austempered samples was observed at -10oC, whereas, that of tempered samples could not be determined. Based on the test results authors wish to recommend the 600oC tempering temperature in place of 450oC where normally tempering is practiced in Alwin industry Karachi during manufacturing of leaf spring.

  2. Factors Affecting Leaf Selection by Foregut-fermenting Proboscis Monkeys: New Insight from in vitro Digestibility and Toughness of Leaves

    Science.gov (United States)

    Matsuda, Ikki; Clauss, Marcus; Tuuga, Augustine; Sugau, John; Hanya, Goro; Yumoto, Takakazu; Bernard, Henry; Hummel, Jürgen

    2017-01-01

    Free-living animals must make dietary choices in terms of chemical and physical properties, depending on their digestive physiology and availability of food resources. Here we comprehensively evaluated the dietary choices of proboscis monkeys (Nasalis larvatus) consuming young leaves. We analysed the data for leaf toughness and digestibility measured by an in vitro gas production method, in addition to previously reported data on nutrient composition. Leaf toughness, in general, negatively correlated with the crude protein content, one of the most important nutritional factors affecting food selection by leaf-eating primates. This result suggests that leaf toughness assessed by oral sensation might be a proximate cue for its protein content. We confirmed the importance of the leaf chemical properties in terms of preference shown by N. larvatus; leaves with high protein content and low neutral detergent fibre levels were preferred to those of the common plant species. We also found that these preferred leaves were less tough and more digestible than the alternatives. Our in vitro results also suggested that N. larvatus were little affected by secondary plant compounds. However, the spatial distribution pattern of plant species was the strongest factor explaining the selection of the preferred leaf species. PMID:28211530

  3. Fracture fragility of HFIR vessel caused by random crack size or random toughness

    International Nuclear Information System (INIS)

    Chang, Shih-Jung; Proctor, L.D.

    1993-01-01

    This report discuses the probability of fracture (fracture fragility) versus a range of applied hoop stresses along the HFIR vessel which is obtained as an estimate of its fracture capacity. Both the crack size and the fracture toughness are assumed to be random variables that follow given distribution functions. Possible hoop stress is based on the numerical solution of the vessel response by applying a point pressure-pulse it the center of the fluid volume within the vessel. Both the fluid-structure interaction and radiation embrittlement are taken into consideration. Elastic fracture mechanics is used throughout the analysis. The probability of vessel fracture for a single crack caused by either a variable crack depth or a variable toughness is first derived. Then the probability of fracture with multiple number of cracks is obtained. The probability of fracture is further extended to include different levels of confidence and variability. It, therefore, enables one to estimate the high confidence and low probability capacity accident load

  4. Effect of TiC addition on fracture toughness of Al6061 alloy

    Science.gov (United States)

    Raviraj, M. S.; Sharanprabhu, C. M.; Mohankumar, G. C.

    2018-04-01

    Al 6061 matrix was reinforced with different proportions of TiC particles such as 3wt%, 5wt% and 7wt% and the effect on fracture toughness was studied. Al-TiC metal matrix composites were produced by stir casting method to ensure uniform distribution of the TiC particulates in the Al matrix. LEFM (Linear Elastic Fracture Mechanics) has been used to characterize the fracture toughness using various specimen geometries. The compact tension (CT) specimens with straight through notch were machined as per ASTM E399 specifications. All the specimens were machined to have constant a/W=0.5 and B/W was varied from 0.2 to 0.7. A sharp crack initiation was done at the end of notch by fatigue loading using servo-hydraulic controlled testing machine. Load v/s crack mouth opening displacement (CMOD) data was plotted and stress intensity factor, KQ determined. Critical stress intensity factor KIC was obtained by plotting KQ v/s thickness of specimen data. The fracture toughness of the composites varied between 16-19 MPa√m as compared to 23MPa√m for base alloy Al6061. Composites with 3wt% and 7wt% TiC showed better fracture toughness than 5wt% TiC reinforced Al metal matrix composites.

  5. WinGridder - An interactive grid generator for TOUGH - A user's manual (Version 1.0)

    International Nuclear Information System (INIS)

    Pan, Lehua; Hinds, Jennifer; Haukwa, Charles; Wu, Yu-Shu; Bodvarsson, Gudmundur

    2001-01-01

    WinGridder is a Windows-based software package for designing, generating, and visualizing at various spatial scales numerical grids used in reservoir simulations and groundwater modeling studies. Development of this software was motivated by the requirements of the TOUGH (Transport of Unsaturated Groundwater and Heat) family of codes (Pruess 1987, 1991) for simulating subsurface processes related to high-level nuclear waste isolation in partially saturated geological media. Although the TOUGH family of codes has great flexibility in handling the variety of grid information required to describe complex objects, designing and generating a suitable irregular grid can be a tedious and error-prone process, even with the help of existing grid generating programs. This is especially true when the number of cells and connections is very large. The processes of inspecting the quality of the grid or extracting sub-grids or other specific grid information are also complex. The mesh maker embedded within TOUGH2 generates only uniform numerical grids and handles only one set of uniform fracture and matrix properties throughout the model domain. This is not suitable for grid generation in complex flow and transport simulations (such as those of Yucca Mountain, which have heterogeneity in both fracture and matrix media). As a result, the software program Amesh (Haukwa 2000) was developed to generate irregular, effective-continuum (ECM) grids

  6. Effect of Thermal Aging and Test Temperatures on Fracture Toughness of SS 316(N) Welds

    Science.gov (United States)

    Dutt, B. Shashank; Babu, M. Nani; Shanthi, G.; Moitra, A.; Sasikala, G.

    2018-03-01

    The effect of thermal aging and test temperatures on fracture toughness (J 0.2) of SS 316(N) weld material has been studied based on J-R curve evaluations. The aging of the welds was carried out at temperatures 370, 475 and 550 °C and for durations varying from 1000 to 20,000 h. The fracture toughness (J-R curve) tests were carried out at 380 and 550 °C for specimens after all aging conditions, including as-weld condition. The initiation fracture toughness (J 0.2) of the SS 316(N) weld material has shown degradation after 20,000-h aging durations and is reflected in all the test temperatures and aging temperatures. The fracture toughness after different aging conditions and test temperatures, including as-weld condition, was higher than the minimum specified value for this class of welds.

  7. Experimental determination of dynamic fracture toughness by J integral method

    International Nuclear Information System (INIS)

    Marandel, B.; Phelippeau, G.; Sanz, G.

    1982-01-01

    Fracture toughness tests are conducted on fatigue precracked compact tension specimens (IT - CT) loaded at K rates of about 2 x 10 4 MPa square root of m/s on a servo-hydraulic machine using a damped set-up. A high frequency alternating current system (10 kHz) is used for the detection of subcritical crack growth during loading. The analog signals from the clip gage, load cell, ram travel and potential drop system are fed into a magnetic tape recorder, filtered and converted to digital data. Load-time and load-displacement-potential curves are plotted and analysed automatically by two different methods, according to the fracture mode: in the lower part of the transition curve, Ksub(ID) is calculated from the maximum load at failure in the linear elastic range (ASTM E399); in the transition and upper shelf regions, Ksub(JD) is calculated from Jsub(ID) at initiation of ductile crack growth in the elastic plastic range. The experimental method described here is applied, as an example, to the study of a low-alloy, medium strength pressure vessel steel (A 508 Cl.3). A comparison is established between the toughness transition curves obtained under quasi-static (Ksub(Jc)) and dynamic (Ksub(JD)) conditions. (author)

  8. Effects of irradiation on crack-arrest toughness of two high-copper welds

    International Nuclear Information System (INIS)

    Iskander, S.K.; Corwin, W.R.; Nanstad, R.K.

    1990-01-01

    The objective of this study is to determine the effect of neutron irradiation on the shift and shape of the lower-bound curve to crack-arrest data. Two submerged-arc welds with copper contents of 0.23 and 0.31 wt % were commercially fabricated in 220-mm-thick plate. Crack-arrest specimens fabricated from these welds were irradiated at a nominal temperature of 288 degree C to an average fluence of 1.9 x 10 19 neutrons/cm 2 (>1 MeV). A preliminary evaluation of the results shows that the neutron-irradiation induced crack-arrest toughness temperature shift is about the same as the Charpy V-notch impact temperature shift at the 41-J energy level. The shape of the lower-bound curves, (for the range of test temperatures covered), compared to those of the ASME K Ia -curve did not seem to have been altered by irradiation. 10 refs., 9 figs., 7 tabs

  9. Fracture toughness master curve characterization of Linde 1092 weld metal for Beaver valley 1 reactor

    International Nuclear Information System (INIS)

    Lee, Bong Sang; Yang, Won Jon; Hong, Jun Hwa

    2000-12-01

    This report summarizes the test results obtained from the Korean contribution to the integrity assessment of low toughness Beaver Valley reactor vessel by characterizing the fracture toughness of Linde 1092 (No. 305414) weld metal. 10 PCVN specimens and 10 1T-CT specimens were tested in accordance with the ASTM E 1921-97 standard, 'Standard test method for determination of reference temperature, T o , for ferritic steels in the transition range'. This results can also be useful for assessment of Linde 80 low toughness welds of Kori-1

  10. Fracture toughness master curve characterization of Linde 1092 weld metal for Beaver valley 1 reactor

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Bong Sang; Yang, Won Jon; Hong, Jun Hwa

    2000-12-01

    This report summarizes the test results obtained from the Korean contribution to the integrity assessment of low toughness Beaver Valley reactor vessel by characterizing the fracture toughness of Linde 1092 (No. 305414) weld metal. 10 PCVN specimens and 10 1T-CT specimens were tested in accordance with the ASTM E 1921-97 standard, 'Standard test method for determination of reference temperature, T{sub o}, for ferritic steels in the transition range'. This results can also be useful for assessment of Linde 80 low toughness welds of Kori-1.

  11. Effect of microstructure on the impact toughness of high strength steels

    Directory of Open Access Journals (Sweden)

    Gutiérrez, Isabel

    2014-12-01

    Full Text Available One of the major challenges in the development of new steel grades is to get increasingly high strength combined with a low ductile brittle transition temperature and a high upper shelf energy. This requires the appropriate microstructural design. Toughness in steels is controlled by different microstructural constituents. Some of them, like inclusions, are intrinsic while others happening at different microstructural scales relate to processing conditions. A series of empirical equations express the transition temperature as a sum of contributions from substitutional solutes, free nitrogen, carbides, pearlite, grain size and eventually precipitation strengthening. Aimed at developing a methodology that could be applied to high strength steels, microstructures with a selected degree of complexity were produced at laboratory in a Nb-microalloyed steel. As a result a model has been developed that consistently predicts the Charpy curves for ferrite-pearlite, bainitic and quenched and tempered microstructures using as input data microstructural parameters. This model becomes a good tool for microstructural design.El desarrollo de nuevos grados de acero se tropieza con frecuencia con la necesidad de incrementar la resistencia mecánica al mismo tiempo que se reduce la temperatura de transición dúctil-frágil y se eleva la energía del palier dúctil. Hacer frente a este reto requiere un diseño microestructural. La tenacidad en aceros está controlada por diferentes constituyentes microestructurales. Algunos de ellos, como las inclusiones son intrínsecos, pero otros que se manifiestan a diferentes escalas microestructurales dependen de las condiciones de proceso. Existen algunas ecuaciones empíricas que permiten calcular para ferrita-perlita en aceros de bajo carbono la temperatura de transición como suma de contribuciones de elementos en solución sólida, nitrógeno libre, carburos, fracción de perlita, tamaño de grano y, eventualmente

  12. Master curve characterization of the fracture toughness behavior in SA508 Gr.4N low alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki-Hyoung, E-mail: shirimp@kaist.ac.k [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of); Kim, Min-Chul; Lee, Bong-Sang [Nuclear Materials Research Division, KAERI, Daejeon 305-353 (Korea, Republic of); Wee, Dang-Moon [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of)

    2010-08-15

    The fracture toughness properties of the tempered martensitic SA508 Gr.4N Ni-Mo-Cr low alloy steel for reactor pressure vessels were investigated by using the master curve concept. These results were compared to those of the bainitic SA508 Gr.3 Mn-Mo-Ni low alloy steel, which is a commercial RPV material. The fracture toughness tests were conducted by 3-point bending with pre-cracked charpy (PCVN) specimens according to the ASTM E1921-09c standard method. The temperature dependency of the fracture toughness was steeper than those predicted by the standard master curve, while the bainitic SA508 Gr.3 steel fitted well with the standard prediction. In order to properly evaluate the fracture toughness of the Gr.4N steels, the exponential coefficient of the master curve equation was changed and the modified curve was applied to the fracture toughness test results of model alloys that have various chemical compositions. It was found that the modified curve provided a better description for the overall fracture toughness behavior and adequate T{sub 0} determination for the tempered martensitic SA508 Gr.4N steels.

  13. Fracture toughness of esthetic dental coating systems by nanoindentation and FIB sectional analysis.

    Science.gov (United States)

    Pecnik, Christina Martina; Courty, Diana; Muff, Daniel; Spolenak, Ralph

    2015-07-01

    Improving the esthetics of Ti-based dental implants is the last challenge remaining in the optimization process. The optical issues were recently solved by the application of highly and selectively reflective coatings on Ti implants. This work focuses on the mechanical durability of these esthetic ceramic based coating systems (with and without adhesion layers). The coating systems (Ti-ZrO2, Ti-Al-ZrO2, Ti-Ti-Al-ZrO2, Ti-Ag-ZrO2, Ti-Ti-Ag-ZrO2, Ti-Bragg and Ti-TiO2-Bragg) were subjected to nanoindentation experiments and examined using scanning electron microscopy and focused ion beam cross sectional analysis. Three coating systems contained adhesion layers (10nm of Ti or 60nm of TiO2 layers). The fracture toughness of selected samples was assessed applying two different models from literature, a classical for bulk materials and an energy-based model, which was further developed and adjusted. The ZrO2 based coating systems (total film thickness<200nm) followed a circumferential cracking behavior in contrast to Bragg coated samples (total film thickness around 1.5μm), which showed radial cracking emanating from the indent corners. For Ti-ZrO2 samples, a fracture toughness between 2.70 and 3.70MPam(1/2) was calculated using an energy-based model. The classical model was applied to Bragg coated samples and their fracture toughness ranged between 0.70 and 0.80MPam(1/2). Furthermore, coating systems containing an additional layer (Ti-Ti-Al-ZrO2, Ti-Ti-Ag-ZrO2 and Ti-TiO2-Bragg) showed an improved adhesion between the substrate and the coating. The addition of a Ti or TiO2 layer improved the adhesion between substrate and coating. The validity of the models for the assessment of the fracture toughness depended on the layer structure and fracture profile of the samples investigated here (classical model for thick coatings and energy-based model for thin coatings). Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Dependence of fracture toughness of molybdenum laser welds on dendritic spacing and in situ titanium additions

    International Nuclear Information System (INIS)

    Jellison, J.L.

    1979-01-01

    The fracture toughness of molybdenum welds has been improved by in situ gettering of oxygen by means of physically deposited titanium. The addition of titanium suppressed brittle intergranular fracture. Pulsed laser welds (both Nd:YAG and CO 2 ) exhibited superior toughness to that of continuous wave CO 2 laser welds. Also, welds of vacuum arc remelted grades were tougher than those of sintered molybdenum. However, weld toughness could not be correlated with either oxygen or carbon content

  15. Influence of crystallographic orientation on the fracture toughness of strongly textured Ti--6Al--4V

    International Nuclear Information System (INIS)

    Bowen, A.W.

    1978-01-01

    Fracture toughness values for six test piece orientations in a strongly textured 57-mm thick rolled and annealed Ti--6Al--4V bar have been related to their crystallographic orientations. The K/sub Ic/ values, ranging from 46.3 to 93.3 MPa/m, could be divided into two groups. High values (74.7 to 93.3 MPa/m) were obtained when a crystallographic deformation mode ([1010] or [1122] slip) was parallel to the planes of maximum shear stress for plane strain conditions, and the significant fractographic feature for this group was a clearly defined stretch zone. In the second group, where crystallographic deformation modes were not aligned with the planes of maximum shear stress, much lower K/sub Ic/ values were recorded (46.3 to 50.7 MPa/m). In this case there was no stretch zone and, in addition, some test pieces appeared, in effect, to have delaminated in the immediate vicinity of the crack tip. Similar trends were also indicated by the results of Charpy impact tests. The influence of in-plane elastic anisotropy on fracture toughness is discussed, and the importance of test piece geometry highlighted. From the results it could be inferred that high toughness in anisotropic materials is possible only in certain orientations; stretch zone formation and fatigue striation formation are by the same mechanical process; and there will be significantly different critical crack sizes in textured titanium alloy components

  16. Investigations into the influence of the tup velocity and the heat treatment on the dynamic fracture toughness of Inconel 625

    International Nuclear Information System (INIS)

    Krompholz, K.; Tipping, P.; Ullrich, G.

    1983-09-01

    Experiments were performed with an instrumented impact machine using different drop heights, on the nickel base alloy Inconel 625 in the as received state and after heat treatment for about 1000 h at 923 K. The absorbed impact energy can be obtained either by the direct dial reading, by the integration of the load versus load point displacement diagram or by the integration of the load versus time diagram, knowing the initial impact velocity of the tup. In all cases the agreement was excellent. It is shown that, (i) the dynamic fracture toughness is dependent on the tup velocity and as a consequence on the total energy of the hammer at the different drop heights; (ii) the embrittlement during heat treatment is not combined with a decrease in the fracture toughness although a strong decrease in the absorbed impact energy is observed; (iii) defining a dynamic stress from the velocity dependence of the fracture toughness, the stress is higher for the embrittled material - a tendency verified by tensile tests; (iv) the dynamic fracture toughness can be correlated with the absorbed impact energy up to the load maximum for the heat treated material while the as received material exhibits no such dependency. The change in the tup velocity during the impact process is only small for this type of material. (Auth.)

  17. Fracture toughness of irradiated wrought and cast austenitic stainless steels in BWR environment

    International Nuclear Information System (INIS)

    Chopra, O.K.; Gruber, E.E.; Shack, W.J.

    2007-01-01

    Experimental data are presented on the fracture toughness of wrought and cast austenitic stainless steels (SSs) that were irradiated to a fluence of ∼ 1.5 x 10 21 n/cm 2 (E > 1 MeV) * (∼ 2.3 dpa) at 296-305 o C. To evaluate the possible effects of test environment and crack morphology on the fracture toughness of these steels, all tests were conducted in normal-water-chemistry boiling water reactor (BWR) environments at ∼ 289 o C. Companion tests were also conducted in air on the same material for comparison. The fracture toughness J-R curves for SS weld heat-affected-zone materials in BWR water were found to be comparable to those in air. However, the results of tests on sensitized Type 304 SS and thermally aged cast CF-8M steel suggested a possible effect of water environment. The available fracture toughness data on irradiated austenitic SSs were reviewed to assess the potential for radiation embrittlement of reactor-core internal components. The synergistic effects of thermal and radiation embrittlement of cast austenitic SS internal components are also discussed. (author)

  18. Ductile fracture toughness of heavy section pressure vessel steel plate. A specimen-size study of ASTM A 533 steels

    International Nuclear Information System (INIS)

    Williams, J.A.

    1979-09-01

    The ductile fracture toughness, J/sub Ic/, of ASTM A 533, Grade B, Class 1 and ASTM A 533, heat treated to simulate irradiation, was determined for 10- to 100-mm thick compact specimens. The toughness at maximum specimen load was also measured to determine the conservatism of J/sub Ic/. The toughness of ASTM A 533, Grade B, Class 1 steel was 349 kJ/m 2 and at the equivalent upper shelf temperature, the heat treated material exhibited 87 kJ/m 2 . The maximum load fracture toughness was found to be linearly proportional to specimen size, and only specimens which failed to meet ASTM size criteria exhibited maximum load toughness less than J/sub Ic/

  19. Fracture toughness of A533B Part III - variability of A533B fracture toughness as determined from Charpy data

    International Nuclear Information System (INIS)

    Druce, S.G.; Eyre, B.L.

    1978-08-01

    This is the final part of a series of three reports examining the upper shelf fracture toughness of A533B Class 1 pressure vessel steel. Part I (AERE R 8968) critically reviews the current elasto plastic fracture mechanics methodologies employed to characterise toughness following extensive yielding and Part II (AERE R 8969) examines several sources of fracture mechanics data pertinent to A533B Class 1 in the longitudinal (RW) orientation. Part III is a review of the effects of (i) position and orientation within the plate (ii) welding processes and post weld heat treatment and (iii) neutron irradiation as measured by Charpy impact testing. It is concluded that the upper shelf factor energy is dependent on orientation and position and can be reduced by welding, extended post weld heat treatments and neutron irradiation. Neutron irradiation effects are known to be strongly dependent on composition and metallurgical conditions, but an explanation for the variability following extended post weld treatments has yet to be resolved. (author)

  20. Fracture toughness behaviour of carbon fibre epoxy composite with Kevlar reinforced interleave

    International Nuclear Information System (INIS)

    Yadav, S.N.; Kumar, Vijai; Verma, Sushil K.

    2006-01-01

    This work was to evaluate as to how mode II fracture toughness G II is affected by interleave having Kevlar fibre reinforcement in the fracture plane. Thermoset interleave and chopped Kevlar fibres were applied between the carbon/epoxy composite layers. An artificial crack starter was implanted in the mid-plane to initiate the fracture process. The following five different types of carbon fibre/epoxy composites were prepared and tested. (a) Base laminate without interleave (b) unreinforced interleave and (c) 0.5, 1.0 and 1.5 mg/cm 2 chopped Kevlar fibre reinforced interleave. Results obtained show that fracture toughness G IIC enhanced up to about two times in all the laminates. However, enhancement in fracture toughness G IIC was more effective in interleaved laminate than Kevlar reinforced interleaved because of large energy absorbing capabilities of interleaf. Mechanism of fracture and toughening were examined by using scanning electron microscope

  1. Fracture toughness of yttria-stabilized zirconia sintered in conventional and microwave ovens.

    Science.gov (United States)

    Marinis, Aristotelis; Aquilino, Steven A; Lund, Peter S; Gratton, David G; Stanford, Clark M; Diaz-Arnold, Ana M; Qian, Fang

    2013-03-01

    The fabrication of zirconium dioxide (ZrO2) dental prosthetic substructures requires an extended sintering process (8 to 10 hours) in a conventional oven. Microwave sintering is a shorter process (2 hours) than conventional sintering. The purpose of this study was to compare the fracture toughness of 3 mol % Y2O3-stabilized ZrO2 sintered in a conventional or microwave oven. Partially sintered ZrO2 specimens from 3 manufacturers, KaVo, Lava 3M, and Crystal HS were milled (KaVo Everest engine) and randomly divided into 2 groups: conventional sintering and microwave sintering (n=16 per group). The specimens were sintered according to the manufacturers' recommendations and stored in artificial saliva for 10 days. Fracture toughness was determined by using a 4-point bend test, and load to fracture was recorded. Mean fracture toughness for each material was calculated. A 2-way ANOVA followed by the Tukey HDS post hoc test was used to assess the significance of sintering and material effects on fracture toughness, including an interaction between the 2 factors (α=.05). The 2-way ANOVA suggested a significant main effect for ZrO2 manufacturer (P.05). The main effect of the sintering process (Conventional [5.30 MPa·m(1/2) ±1.00] or Microwave [5.36 MPa·m(1/2) ±0.92]) was not significant (P=.76), and there was no interaction between sintering and ZrO2 manufacturer (P=.91). Based on the results of this study, no statistically significant difference was observed in the fracture toughness of ZrO2 sintered in microwave or conventional ovens. Copyright © 2013 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

  2. Fracture toughness versus micro-tensile bond strength testing of adhesive-dentin interfaces.

    Science.gov (United States)

    De Munck, Jan; Luehrs, Anne-Katrin; Poitevin, André; Van Ende, Annelies; Van Meerbeek, Bart

    2013-06-01

    To assess interfacial fracture toughness of different adhesive approaches and compare to a standard micro-tensile bond-strength (μTBS) test. Chevron-notched beam fracture toughness (CNB) was measured following a modified ISO 24370 standard. Composite bars with dimensions of 3.0×4.0×25 mm were prepared, with the adhesive-dentin interface in the middle. At the adhesive-dentin interface, a chevron notch was prepared using a 0.15 mm thin diamond blade mounted in a water-cooled diamond saw. Each specimen was loaded until failure in a 4-point bend test setup and the fracture toughness was calculated according to the ISO specifications. Similarly, adhesive-dentin micro-specimens (1.0×1.0×8-10 mm) were stressed in tensile until failure to determine the μTBS. A positive correlation (r(2)=0.64) was observed between CNB and μTBS, which however was only nearly statistically significant, mainly due to the dissimilar outcome of Scotchbond Universal (3M ESPE). While few μTBS specimens failed at the adhesive-dentin interface, almost all CNB specimens failed interfacially at the notch tip. Weibull moduli for interfacial fracture toughness were much higher than for μTBS (3.8-11.5 versus 2.7-4.8, respectively), especially relevant with regard to early failures. Although the ranking of the adhesives on their bonding effectiveness tested using CNB and μTBS corresponded well, the outcome of CNB appeared more reliable and less variable. Fracture toughness measurement is however more laborious and requires specific equipment. The μTBS nevertheless appeared to remain a valid method to assess bonding effectiveness in a versatile way. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  3. In Situ Forming, Cytocompatible, and Self-Recoverable Tough Hydrogels Based on Dual Ionic and Click Cross-Linked Alginate.

    Science.gov (United States)

    Ghanian, Mohammad Hossein; Mirzadeh, Hamid; Baharvand, Hossein

    2018-05-14

    A dual cross-linking strategy was developed to answer the urgent need for fatigue-resistant, cytocompatible, and in situ forming tough hydrogels. Clickable, yet calcium-binding derivatives of alginate were synthesized by partial substitution of its carboxyl functionalities with furan, which could come into Diels-Alder click reaction with maleimide end groups of a four arm poly(ethylene glycol) cross-linker. Tuning the cooperative viscoelastic action of transient ionic and permanent click cross-links within the single network of alginate provided a soft tough hydrogel with a set of interesting features: (i) immediate self-recovery under cyclic loading, (ii) highly efficient and autonomous self-healing upon fracture, (iii) in situ forming ability for molding and minimally invasive injection, (iv) capability for viable cell encapsulation, and (v) reactivity for on-demand biomolecule conjugation. The facile strategy is applicable to a wide range of natural and synthetic polymers by introducing the calcium binding and click reacting functional groups and can broaden the use of tough hydrogels in load-bearing, cell-laden applications such as soft tissue engineering and bioactuators.

  4. Fracture toughness for materials of low ductility

    International Nuclear Information System (INIS)

    Barzilay, S.; Karp, B.; Perl, M.

    1998-05-01

    The results of a survey of methods for evaluating fracture toughness characteristics for semi-brittle and brittle materials are presented in this report. These methods differ considerably from those used for ductile materials by the specimen configurations, the methodology of the experiments and by the problems occurring while using these methods. The survey yields several important findings A. It is possible to create steady state crack growth by cyclic loading in several semi-brittle materials. B. The need for pre-cracking is not yet clear, nevertheless it is recommended to evaluate fracture toughens with pre-cracked specimen. C. As crack length and ligament size may effect fracture toughness results it is necessary to define minimum specimen dimensions to avoid this effect. D. The specimen thickness hardly affects the fracture toughens. E. Loading rate for the test is not well defined. It is commonly accepted to end the test in one minute. F. The main mechanism that causes inelastic deformation in semi-brittle materials is related to the generation of micro-cracks

  5. Biofuels: making tough choices

    Energy Technology Data Exchange (ETDEWEB)

    Vermeulen, Sonja; Dufey, Annie; Vorley, Bill

    2008-02-15

    The jury is still out on biofuels. But one thing at least is certain: serious trade-offs are involved in the production and use of these biomass-derived alternatives to fossil fuels. This has not been lost on the European Union. The year kicked off with an announcement from the EU environment commissioner that it may be better for the EU to miss its target of reaching 10 per cent biofuel content in road fuels by 2020 than to compromise the environment and human wellbeing. The 'decision tree' outlined here can guide the interdependent processes of deliberation and analysis needed for making tough choices in national biofuels development.

  6. Application of TOUGH to hydrologic problems related to the unsaturated zone site investigation at Yucca Mountain, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Kwicklis, E.M.; Healy, R.W. [Geological Survey, Lakewood, CO (United States); Bodvarsson, G.S. [Lawrence Berkeley Laboratory, CA (United States)] [and others

    1995-03-01

    To date, TOUGH and TOUGH2 have been the principal codes used by the U.S. Geological Survey in their investigation of the hydrology of the unsaturated zone at Yucca Mountain. Examples of some applications of the TOUGH and TOUGH2 codes to flow and transport problems related to the Yucca Mountain site investigation are presented, and the slight modifications made to the codes to implement them are discussed. These examples include: (1) The use of TOUGH in a simple fracture network model, with a discussion of an approach to calculate directional relative permeabilities at computational cells located at fracture intersections. These simulations illustrated that, under unsaturated conditions, the locations of dominant pathways for flow through fracture networks are sensitive to imposed boundary conditions; (2) The application of TOUGH to investigate the possible hydrothermal effects of waste-generated heat at Yucca Mountain using a dual-porosity, dual-permeability treatment to better characterize fracture-matrix interactions. Associated modifications to TOUGH for this application included implementation of a lookup table that can express relative permeabilities parallel and transverse to the fracture plane independently. These simulations support the continued use of an effective media approach in analyses of the hydrologic effects of waste-generated heat; and (3) An investigation of flow and tracer movement beneath a wash at Yucca Mountain in which a particle tracker was used as a post-processor. As part of this study, TOUGH2 was modified to calculate and output the x-,y- and z- sequence of tuffs overlying the potential repository site will result in the formation of capillary barriers that locally promote considerable lateral flow, thereby significantly decreasing the magnitude of fluxes form peak values at the ground surface and delaying the arrival of surface-derived moisture at the potential repository horizon.

  7. Scatter modelling of fracture toughness data for reactor pressure vessel structural integrity assessment

    International Nuclear Information System (INIS)

    Pesoz, M.

    1997-01-01

    In the last decade, there has been an increasing interest at EDF in developing and applying probabilistic methods for a variety of purposes. In the field of structural integrity and reliability they are used to evaluate the effect of deterioration due to ageing mechanisms, mainly on major passive structural components such as reactor pressure vessel, steam generator and piping in nuclear plants. Such approaches provide an attractive supplement to the more conventional deterministic method, based upon pessimistic assumptions, that give results too far from reality to support effective decisions. In addition to deterministic calculations, a Probabilistic Fracture Mechanics model has been developed in order to analyse the risk of brittle failure of the reactor pressure vessel and to perform sensitivity studies. The material fracture toughness (K IC ) uncertainty appears to be strongly influencing the probability of failure under accidental conditions. Up to now, this parameter is determined from the RCC-M code reference curve, which is the same as the ASME reference curve. But an important issue when performing probabilistic analysis is the correct statistical modelling of input parameters. That's why modelling works have been carried out using results of fracture toughness tests performed for demonstrating the validity of the reference curve. This paper presents the statistical treatments that have been performed to model the scatter of temperature dependent parameter (K IC (T). A specific data base containing a few hundreds of French and US results have been carried and Weibull models have been fitted, based on various master curve equations (K. Wallin (Senior Adviser at the Technical Research Centre of Finland) or RCC-M types). (author)

  8. On the proper fracture toughness properties to be used for pressurized thermal shock evaluations

    International Nuclear Information System (INIS)

    Server, W.L.

    1997-01-01

    The traditional approach in the U.S. for evaluating PTS has relied upon probabilistic studies in which the toughness has been based upon the data used to generated the lower bound ASME Code K IC and K IR curves. A mean curve through this data with a Gaussian statistical distribution assumed, except for a lower bound cutoff of somewhere between 2 and 3 standard deviations, has been used. The RT NDT normalizing concept has been maintained which then requires the measured shift in Charpy V-notch toughness at the 41 J (30 ft-lb) energy level be used to adjust the position of the Code curves. The Master Curve method provides a unique alternative in providing a much better measure of real fracture toughness, plus the opportunity to use a more refined statistical distribution using Weibull statistics. There are active moves in the U.S. to Standardize and Codify the Master Curve (also termed T 0 method). Benefits to both deterministic and probabilistic analyses will be realized since more realistic measures of toughness can be used

  9. On the proper fracture toughness properties to be used for pressurized thermal shock evaluations

    Energy Technology Data Exchange (ETDEWEB)

    Server, W L [ATI Consulting, Danville, CA (United States)

    1997-09-01

    The traditional approach in the U.S. for evaluating PTS has relied upon probabilistic studies in which the toughness has been based upon the data used to generated the lower bound ASME Code K{sub IC} and K{sub IR} curves. A mean curve through this data with a Gaussian statistical distribution assumed, except for a lower bound cutoff of somewhere between 2 and 3 standard deviations, has been used. The RT{sub NDT} normalizing concept has been maintained which then requires the measured shift in Charpy V-notch toughness at the 41 J (30 ft-lb) energy level be used to adjust the position of the Code curves. The Master Curve method provides a unique alternative in providing a much better measure of real fracture toughness, plus the opportunity to use a more refined statistical distribution using Weibull statistics. There are active moves in the U.S. to Standardize and Codify the Master Curve (also termed T{sub 0} method). Benefits to both deterministic and probabilistic analyses will be realized since more realistic measures of toughness can be used.

  10. Fracture toughness testing of core from the Cambro-Ordovician Section on the Oak Ridge Reservation

    International Nuclear Information System (INIS)

    Lemiszki, P.J.; Landes, J.D.

    1996-01-01

    The modified ring test was used to determine the mode I fracture toughness of bedrock cores from the DOE Oak Ridge Reservation in east Tennessee. Low porosity sandstones, limestones, and dolostones from the lower part of the Paleozoic section in Copper Creek and Whiteoak Mountain thrust sheets were sampled. In general, the average mode I fracture toughness decreases from sandstone, dolostone, and limestone. The fracture toughness of the limestones varies between rock units, which is related to different sedimentologic characteristics. Quality of results was evaluated by testing cores of Berea Sandstone and Indiana Limestone, which produced results similar to published results

  11. A Novel Methods for Fracture Toughness Evaluation of Tool Steels with Post-Tempering Cryogenic Treatment

    Directory of Open Access Journals (Sweden)

    Ramona Sola

    2017-02-01

    Full Text Available Cryogenic treatments are usually carried out immediately after quenching, but their use can be extended to post tempering in order to improve their fracture toughness. This research paper focuses on the influence of post-tempering cryogenic treatment on the microstructure and mechanical properties of tempered AISI M2, AISI D2, and X105CrCoMo18 steels. The aforementioned steels have been analysed after tempering and tempering + cryogenic treatment with scanning electron microscopy, X-ray diffraction for residual stress measurements, and micro- and nano-indentation to determine Young’s modulus and plasticity factor measurement. Besides the improvement of toughness, a further aim of the present work is the investigation of the pertinence of a novel technique for characterizing the fracture toughness via scratch experiments on cryogenically-treated steels. Results show that the application of post-tempering cryogenic treatment on AISI M2, AISI D2, and X105CrCoMo18 steels induce precipitation of fine and homogeneously dispersed sub-micrometric carbides which do not alter hardness and Young’s modulus values, but reduce residual stresses and increase fracture toughness. Finally, scratch test proved to be an alternative simple technique to determine the fracture toughness of cryogenically treated steels.