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Sample records for charpy impact toughness

  1. 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

    2017-02-02

    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.

  2. 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.

  3. Low blow Charpy impact of silicon carbides

    Science.gov (United States)

    Abe, H.; Chandan, H. C.; Bradt, R. C.

    1978-01-01

    The room-temperature impact resistance of several commercial silicon carbides was examined using an instrumented pendulum-type machine and Charpy-type specimens. Energy balance compliance methods and fracture toughness approaches, both applicable to other ceramics, were used for analysis. The results illustrate the importance of separating the machine and the specimen energy contributions and confirm the equivalence of KIc and KId. The material's impact energy was simply the specimen's stored elastic strain energy at fracture.

  4. Charpy Impact Test on Polymeric Molded Parts

    Directory of Open Access Journals (Sweden)

    Alexandra Raicu

    2012-09-01

    Full Text Available The paper presents the Charpy impact tests on the AcrylonitrileButadiene-Styrene (ABS polymeric material parts. The Charpy impact test, also known as the Charpy V-notch test, is a standardized strain rate test which determines the amount of energy absorbed by a material during fracture. This is a typical method described in ASTM Standard D 6110. We use for testing an Instron - Dynatup equipment which have a fully integrated hardware and software package that let us capture load information at very high speed from the impact tests.

  5. Degradation of mechanical properties of cast Cr-Mo-V and Cr-W-V steam turbine casings after long-term service at elevated temperatures: Pt. 2:; Fracture toughness, correlation of fracture toughness with Charpy V-notch toughness

    Energy Technology Data Exchange (ETDEWEB)

    Holzmann, M.; Man, J.; Vlach, B. (Ceskoslovenska Akademie Ved, Brno (Czech Republic). Ustav Fyzikalni Metalurgie); Krumpos, J. (Czechoslovak Academy of Sciences, Plzen (Czech Republic). Inst. of Technology and Reliability of Machine Structures)

    1994-01-01

    The effect of long-term exposure at elevated temperatures on the transition behaviour of the fracture toughness temperature curve of cast Cr-Mo-V and Cr-W-V steels has been studied. The fracture toughness versus temperature behaviour after any operational period seems to be controlled by the initial fracture properties. Relationships linking the fracture toughness to Charpy V-notch impact properties are reported. The validity of these relationships for cast steels was confirmed. (Author)

  6. Finite element analysis of unnotched charpy impact tests

    Science.gov (United States)

    2008-10-01

    This paper describes nonlinear finite element analysis (FEA) to examine the energy to : fracture unnotched Charpy specimens under pendulum impact loading. An oversized, : nonstandard pendulum impactor, called the Bulk Fracture Charpy Machine (BFCM), ...

  7. Characterization by notched and precracked Charpy tests of the in-service degradation of RPV steel fracture toughness

    Energy Technology Data Exchange (ETDEWEB)

    Fabry, A.

    1997-01-01

    The current engineering and regulatory practice to estimate fracture toughness safety margins for nuclear reactor pressure vessels (RPVs) relies heavily on the CVN impact test. Techniques to estimate in-service toughness degradation directly using a variety of precracked specimens are under development worldwide. Emphasis is on their miniaturization. In the nuclear context, it is essential to address many issues such as representativity of the surveillance programs with respect to the vessel in terms of materials and environment, transferability of test results to the structure (constraint and size effects), lower bound toughness certification, creadibility relative to trends of exising databases. An enhanced RPV surveillance strategy in under development in Belgium. It combines state-of-the-art micromechanical and damage modelling to the evaluation of CVN load-deflection signals, tensile stress-strain curves and slow-bend tests of reconstituted precracked Charpy specimens. A probabilistic micromechanical model has been established for static and dynamic transgranular cleavage initiation fracture toughness in the ductile-brittle transition temperature range. This model allows to project toughness bounds for any steel embrittlement condition from the corresponding CVN and static tensile properties, using a single scaling factor defined by imposing agreement with toughness tests in a single condition. The outstanding finding incorporated by this toughness transfer model is that the microcleavage fracture stress is affected by temperature in the ductile-brittle transition and that this influence is strongly correlated to the flow stress: this explains the shape of the K{sub Ic}n K{sub Id} temperature curves as well as the actual magnitude of the strain rate and irradiation effects. Furthermore, CVN crack arrest loads and fracture appearance are also taken advantage of in order to estimate K{sub Ia} degradation. Finally, the CVN-tensile load-temperature diagram

  8. Fracture Behavior and Delamination Toughening of Molybdenum in Charpy Impact Tests

    Science.gov (United States)

    Babinsky, K.; Primig, S.; Knabl, W.; Lorich, A.; Stickler, R.; Clemens, H.

    2016-11-01

    This study combines advanced characterization techniques with conventional Charpy impact tests to relate the mechanical properties to the microstructure of technically pure molybdenum, especially regarding its toughness. V-notched samples with different orientations were prepared from a rolled molybdenum plate in stress-relieved and recrystallized condition. The ductile-to-brittle transition-temperature was analyzed in terms of the delamination behavior influenced by the microstructure. A pronounced increase of toughness was found for specific oriented samples, which can be explained by macroscopic delamination. Elongated grains led to enhanced delamination in Charpy impact tests with variations for different orientations. In general, delamination occurs as a result of brittle fracture; however, an increase in toughness in the Charpy impact test can be provoked. This mechanism is called thin sheet toughening or delamination toughening. Electron backscatter diffraction measurements were performed to get a deeper knowledge about crack propagation and delamination behavior in the rolled plate. Recrystallization shifts the transition region to significantly higher temperatures, which is explained by the globular grain shape as well as grain boundary segregation. The occurrence of delamination is discussed, taking texture, grain shape and segregation effects into account.

  9. Tensile and charpy impact properties of irradiated reduced-activation ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L.; Alexander, D.J. [Oak Ridge National Lab., TN (United States)

    1996-10-01

    Tensile tests were conducted on eight reduced-activation Cr-W steels after irradiation to 15-17 and 26-29 dpa, and Charpy impact tests were conducted on the steels irradiated to 26-29 dpa. Irradiation was in the Fast Flux Test Facility at 365{degrees}C on steels containing 2.25-12% Cr, varying amounts of W, V, and Ta, and 0.1%C. Previously, tensile specimens were irradiated to 6-8 dpa and Charpy specimens to 6-8, 15-17, and 20-24 dpa. Tensile and Charpy specimens were also thermally aged to 20000 h at 365{degrees}C. Thermal aging had little effect on the tensile behavior or the ductile-brittle transition temperature (DBTT), but several steels showed a slight increase in the upper-shelf energy (USE). After {approx}7 dpa, the strength of the steels increased and then remained relatively unchanged through 26-29 dpa (i.e., the strength saturated with fluence). Post-irradiation Charpy impact tests after 26-29 dpa showed that the loss of impact toughness, as measured by an increase in DBTT and a decrease in the USE, remained relatively unchanged from the values after 20-24 dpa, which had been relatively unchanged from the earlier irradiations. As before, the two 9Cr steels were the most irradiation resistant.

  10. Tensile and Charpy impact properties of irradiated reduced-activation ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L.; Alexander, D.J.

    1996-10-01

    Tensile tests were conducted on 8 reduced-activation Cr-W steels after irradiation to 15-17 and 26-29 dpa, and Charpy impact tests were conducted on steels irradiated to 26-29 dpa. Irradiation was in Fast Flux Test Facility at 365 C on steels containing 2.25-12% Cr, varying amounts of W, V, and Ta, and 0.1%C. Previously, tensile specimens were irradiated to 6-8 dpa and Charpy specimens to 6-8, 15- 17, and 20-24 dpa. Tensile and Charpy specimens were also thermally aged to 20,000 h at 365 C. Thermal aging had little effect on tensile properties or ductile-brittle transition temperature (DBTT), but several steels showed a slight increase in upper-shelf energy (USE). After 7 dpa, strength increased (hardened) and then remained relatively unchanged through 26-29 dpa (ie, strength saturated with fluence). Post-irradiation Charpy impact tests after 26-29 dpa showed that the loss of impact toughness (increased DBTT, decreased USE) remained relatively unchanged from the values after 20-24 dpa, which had been relatively unchanged from the earlier irradiations. As before, the two 9Cr steels had the most irradiation resistance.

  11. Fracture Toughness and Charpy CVN Data for A36 Steel with Wet Welding

    Directory of Open Access Journals (Sweden)

    Gerardo Terán Méndez

    Full Text Available Abstract This study presents KIC data obtained from KIC-CVN correlations from Charpy CVN values. For this study, T-welded connections were manufactured from ASTM A36 and E6013 electrodes in dry conditions. Then, a rectangular grinding at the weld toe was carried out and filled with wet welding. Charpy specimens were extracted to obtain CVN values. An exhaustive search through the literature of several authors was performed to collect experimental CVN data about wet welding being applied to A36 steel for comparison with CVN data obtained in this study. By using Charpy impact energy (CVN, KIC values could be predicted by KIC-CVN correlations. In addition, correlations were presented to obtain KIC values in the lower shelf, transition temperature zones and different zones for the energy-temperature curve of A36 steel. Of these correlations, Barsom’s equation was adopted, because he applied the stress yield (σYS of the material and it can be applied in all zones for the energy-temperature curve. The results revealed that CVN values are proportionate to KIC, this data decreases as water depth increases. This took place because several discontinuities, such as, porosity, slag inclusion, non-metallic inclusion, cracking and microstructures are present in the wet welding.

  12. An automated data collection system for a Charpy impact tester

    Science.gov (United States)

    Weigman, Bernard J.; Spiegel, F. Xavier

    1993-01-01

    A method for automated data collection has been developed for a Charpy impact tester. A potentiometer is connected to the pivot point of the hammer and measures the angular displacement of the hammer. This data is collected with a computer and, through appropriate software, accurately records the energy absorbed by the specimen. The device can be easily calibrated with minimal effort.

  13. Charpy Impact Energy and Microindentation Hardness of 60-NITINOL

    Science.gov (United States)

    Stanford, Malcolm K.

    2012-01-01

    60-NITINOL (60 wt.% Ni 40 wt.% Ti) is being studied as a material for advanced aerospace components. The Charpy impact energy and microindentation hardness has been studied for this material, fabricated by vacuum induction skull melting (casting) and by hot isostatic pressing. Test specimens were prepared in various hardened and annealed heat treatment conditions. The average impact energy ranged from 0.33 to 0.49J for the hardened specimens while the annealed specimens had impact energies ranging from 0.89 to 1.18J. The average hardness values of the hardened specimens ranged from 590 to 676 HV while that of the annealed specimens ranged from 298 to 366 HV, suggesting an inverse relationship between impact energy and hardness. These results are expected to provide guidance in the selection of heat treatment processes for the design of mechanical components.

  14. Comparison of Impact Duration Between Experiment and Theory From Charpy Impact Test

    Directory of Open Access Journals (Sweden)

    Muhammad Said N.B.

    2016-01-01

    Full Text Available This study presents the comparison of impact duration between experiment and theory from impact signal through a Charpy test. Recently, the number of accidents on the highway has been increased and it depends on the impact duration of material that have the ability to provide adequate protection to passengers from harmful and improve occupant survivability during crash event. Charpy impact test was implemented on different material and thickness but at the same striker velocity. Impact signal is obtained through the strain gauge that has been installed to striker hammer and connected to frequency data acquisition system. Collected signal is then analysed to identify the time period during impact before fractured. Result from both experiment and theory shows an increment to the impact duration as thickness is increased. Charpy test shows that aluminium 6061-T6 has a higher impact duration compared to carbon steel 1050.

  15. 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 me...

  16. Charpy Impact Tests of Epoxy Composites Reinforced with Giant Bamboo Fibers

    OpenAIRE

    Glória,Gabriel Oliveira; Margem,Frederico Muylaert; Ribeiro,Carolina Gomes Dias; Moraes,Ygor Macabu de; Cruz,Renato Batista da; Silva,Flavio de Andrade; Monteiro,Sergio Neves

    2015-01-01

    The giant bamboo fiber is among the strongest in the Bambusa species with a potential for application as engineering material. Its properties have been evaluated but there is limited information on the impact resistance of epoxy composites incorporated with giant bamboo fibers. Therefore, this study evaluated the Charpy impact energy of epoxy matrix composites reinforced with up to 30 vol% of giant bamboo fibers. Specimens with Charpy configuration were press-molded with continuous and aligne...

  17. Miniature Precracked Charpy Specimens for Measuring the Master Curve Reference Temperature of RPV Steels at Impact Loading Rates

    Energy Technology Data Exchange (ETDEWEB)

    Lucon, E.; Scibetta, M.; Puzzolante, L.

    2008-10-15

    In the framework of the 2006 Convention, we investigated the applicability of fatigue precracked miniature Charpy specimens of KLST type (MPCC - B = 3 mm, W = 4 mm and L = 27 mm) for impact toughness measurements, using the well-characterized JRQ RPV steel. In the ductile to-brittle transition region, MPCC tests analyzed using the Master Curve approach and compared to data previously obtained from PCC specimens had shown a more ductile behavior and therefore un conservative results. In the investigation presented in this report, two additional RPV steels have been used to compare the performance of impact-tested MPCC and PCC specimens in the transition regime: the low-toughness JSPS steel and the high-toughness 20MnMoNi55 steel. The results obtained (excellent agreement for 20MnMoNi55 and considerable differences between T0 values for JSPS) are contradictory and do not presently allow qualifying the MPCC specimens as a reliable alternative to PCC samples for impact toughness measurements.

  18. Annealing for plant life management: hardness, tensile and Charpy toughness properties of irradiated, annealed and re-irradiated mock-up low alloy nuclear pressure vessel steel

    Energy Technology Data Exchange (ETDEWEB)

    Tipping, Philip; Cripps, Robin (Paul Scherrer Inst. (PSI), Villigen (Switzerland))

    1994-01-01

    Hardness, tensile and Charpy properties of an irradiated (I) and irradiated-annealed-reirradiated (IAR) mock-up pressure vessel steel are presented. Spectrum tailored pressurized light water reactor (PWR) irradiation at 290[sup o]C by fast neutrons up to nominal fluences of 5 x 10[sup 19]/cm[sup 2] (E [>=] 1 MeV) in a swimming pool type reactor caused the hardness, tensile yield stress and tensile strength to increase. Embrittlement also occurred as indicated by Charpy toughness tests. The optimum annealing heat treatment for the main program was determined using isochronal and isothermal runs on the material and measuring the Vickers microhardness. The response to an intermediate annealing treatment (460[sup o]C for 18 h), when 50% of the target fluence has been reached and then irradiating to the required end fluence (IAR condition) was then monitored further by Charpy and tensile mechanical properties. Annealing was beneficial in mitigating overall hardening or embrittlement effects. The rate of re-embrittlement after annealing and re-irradiating was no faster than when no annealing had been performed. Annealing temperatures below 440[sup o]C were indicated as requiring relatively long times, i.e. [>=] 168 h to achieve some reduction in radiation induced hardness for example. (Author).

  19. An automated digital data collection and analysis system for the Charpy Impact Tester

    Science.gov (United States)

    Kohne, Glenn S.; Spiegel, F. Xavier

    1994-01-01

    The standard Charpy Impact Tester has been modified by the addition of a system of hardware and software to improve the accuracy and consistency of measurements made during specimen fracturing experiments. An optical disc, light source, and detector generate signals that indicate the pendulum position as a function of time. These signals are used by a computer to calculate the velocity and kinetic energy of the pendulum as a function of its position.

  20. Effects of Microalloying on the Impact Toughness of Ultrahigh-Strength TRIP-Aided Martensitic Steels

    OpenAIRE

    Kobayashi, Junya; Ina, Daiki; Nakajima, Yuji; Sugimoto, Koh-Ichi

    2013-01-01

    The effects of the addition of Cr, Mo, and/or Ni on the Charpy impact toughness of a 0.2 pct C-1.5 pct Si-1.5 pct Mn-0.05 pct Nb transformation-induced plasticity (TRIP)-aided steel with a lath-martensite structure matrix (i.e., a TRIP-aided martensitic steel or TM steel) were investigated with the aim of using the steel in automotive applications. In addition, the relationship between the toughness of the various alloyed steels and their metallurgical characteristics was determined. When Cr,...

  1. Validation Study of Unnotched Charpy and Taylor-Anvil Impact Experiments using Kayenta

    Energy Technology Data Exchange (ETDEWEB)

    Kamojjala, Krishna [Idaho National Lab. (INL), Idaho Falls, ID (United States); Lacy, Jeffrey [Idaho National Lab. (INL), Idaho Falls, ID (United States); Chu, Henry S. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Brannon, Rebecca [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-03-01

    Validation of a single computational model with multiple available strain-to-failure fracture theories is presented through experimental tests and numerical simulations of the standardized unnotched Charpy and Taylor-anvil impact tests, both run using the same material model (Kayenta). Unnotched Charpy tests are performed on rolled homogeneous armor steel. The fracture patterns using Kayenta’s various failure options that include aleatory uncertainty and scale effects are compared against the experiments. Other quantities of interest include the average value of the absorbed energy and bend angle of the specimen. Taylor-anvil impact tests are performed on Ti6Al4V titanium alloy. The impact speeds of the specimen are 321 m/s and 393 m/s. The goal of the numerical work is to reproduce the damage patterns observed in the laboratory. For the numerical study, the Johnson-Cook failure model is used as the ductile fracture criterion, and aleatory uncertainty is applied to rate-dependence parameters to explore its effect on the fracture patterns.

  2. Room-Temperature Charpy Impact Property of 3D-Printed 15-5 Stainless Steel

    Science.gov (United States)

    Sagar, Sugrim; Zhang, Yi; Wu, Linmin; Park, Hye-Young; Lee, Je-Hyun; Jung, Yeon-Gil; Zhang, Jing

    2018-01-01

    In this study, the room-temperature Charpy impact property of 3D-printed 15-5 stainless steel was investigated by a combined experimental and finite element modeling approach. The experimentally measured impact energy is 10.85 ± 1.20 J/cm2, which is comparable to the conventionally wrought and non-heat treated 15-5 stainless steel. In parallel to the impact test experiment, a finite element model using the Johnson-Cook material model with damage parameters was developed to simulate the impact test. The simulated impact energy is 10.46 J/cm2, which is in good agreement with the experimental data. The fracture surface from the experimentally tested specimen suggests that the 3D-printed specimens undergo predominately brittle fracture.

  3. 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.

  4. Influence of Texture on Impact Toughness of Ferritic Fe-20Cr-5Al Oxide Dispersion Strengthened Steel.

    Science.gov (United States)

    Sánchez-Gutiérrez, Javier; Chao, Jesus; Vivas, Javier; Galvez, Francisco; Capdevila, Carlos

    2017-07-03

    Fe-based oxide dispersion strengthened (ODS) steels are oriented to applications where high operating temperatures and good corrosion resistance is paramount. However, their use is compromised by their fracture toughness, which is lower than other competing ferritic-martenstic steels. In addition, the route required in manufacturing these alloys generates texture in the material, which induces a strong anisotropy in properties. The V-notched Charpy tests carried out on these alloys, to evaluate their impact toughness, reveal that delaminations do not follow the path that would be expected. There are many hypotheses about what triggers these delaminations, but the most accepted is that the joint action of particles in the grain boundaries, texture induced in the manufacturing process, and the actual microstructure of these alloys are responsible. In this paper we focused on the actual role of crystallographic texture on impact toughness in these materials. A finite elements simulation is carried out to solely analyze the role of texture and eliminate other factors, such as grain boundaries and the dispersed particles. The work allows us to conclude that crystallographic texture plays an important role in the distribution of stresses in the Charpy specimens. The observed delaminations might be explained on the basis that the crack in the grain, causing the delamination, is directly related to the shear stresses τ12 on both sides of the grain boundary, while the main crack propagation is a consequence of the normal stress to the crack.

  5. Characteristic of retained austenite decomposition during tempering and its effect on impact toughness in SA508 Gr.3 steel

    Science.gov (United States)

    Yan, Guanghua; Han, Lizhan; Li, Chuanwei; Luo, Xiaomeng; Gu, Jianfeng

    2017-01-01

    Retained austenite(RA) usually presents in the quenched Nuclear Pressure-Vessel SA508 Gr.3 steel. In the present work, the characteristic of RA decomposition and its effect on the impact toughness were investigated by microstructure observation, dilatometric experiments and Charpy impact tests. The results show that the RA transformed into martensite and bainite during tempering at 230 °C and 400 °C respectively, while mixture of long rod carbides and ferrite formed at 650 °C. The long rod carbides formed from RA decomposition decrease the critical cleavage stress for initiation of micro-cracks, and deteriorate the impact toughness of the steel. Pre-tempering at a low temperature such as 230 °C or 400 °C leading to the decomposition of RA into martensite or baintie can eliminate the deterioration of the toughness caused by direct decomposition into long rod carbides. The absorbed energy indicate that pre-tempering at 400 °C can drive dramatically improvement in the toughness of the steel.

  6. Charpy impact test results for low activation ferritic alloys irradiated to 30 dpa

    Energy Technology Data Exchange (ETDEWEB)

    Schubert, L.E.; Hamilton, M.L.; Gelles, D.S. [Pacific Northwest National Laboratory, Richland, WA (United States)

    1996-04-01

    Miniature specimens of six low activation ferritic alloys have been impact field tested following irradiation at 370{degrees}C to 30 dpa. Comparison of the results with those of control specimens and specimens irradiated to 10 dpa indicates that degradation in the impact behavior appears to have saturated by {approx}10 dpa in at least four of these alloys. The 7.5Cr-2W alloy referred to as GA3X appears most promising for further consideration as a candidate structural material in fusion reactor applications, although the 9Cr-1V alloy may also warrant further investigation.

  7. Factors Affecting Impact Toughness in Stabilized Intermediate Purity 21Cr Ferritic Stainless Steels and Their Simulated Heat-Affected Zones

    Science.gov (United States)

    Anttila, Severi; Alatarvas, Tuomas; Porter, David A.

    2017-12-01

    The correlation between simulated weld heat-affected zone microstructures and toughness parameters has been investigated in four intermediate purity 21Cr ferritic stainless steels stabilized with titanium and niobium either separately or in combination. Extensive Charpy V impact toughness testing was carried out followed by metallography including particle analysis using electron microscopy. The results confirmed that the grain size and the number density of particle clusters rich in titanium nitride and carbide with an equivalent circular diameter of 2 µm or more are statistically the most critical factors influencing the ductile-to-brittle transition temperature. Other inclusions and particle clusters, as well as grain boundary precipitates, are shown to be relatively harmless. Stabilization with niobium avoids large titanium-rich inclusions and also suppresses excessive grain growth in the heat-affected zone when reasonable heat inputs are used. Thus, in order to maximize the limited heat-affected zone impact toughness of 21Cr ferritic stainless steels containing 380 to 450 mass ppm of interstitials, the stabilization should be either titanium free or the levels of titanium and nitrogen should be moderated.

  8. Influence of Heat Input on Martensite Formation and Impact Property of Ferritic-Austenitic Dissimilar Weld Metals

    National Research Council Canada - National Science Library

    M. Mukherjee T.K. Pal

    2012-01-01

    .... The welded joints were evaluated by microstructure and charpy impact toughness. The dependence of weld metal microstructure on heat input and filler wires were determined by dilution calculation, Creq/Nieq ratio, stacking fault energy (SFE...

  9. Effect of Heat Treatment on Microstructure and Impact Toughness of Ti-6Al-4V Manufactured by Selective Laser Melting Process

    Directory of Open Access Journals (Sweden)

    Lee K.-A.

    2017-06-01

    Full Text Available This study manufactured Ti-6Al-4V alloy using one of the powder bed fusion 3D-printing processes, selective laser melting, and investigated the effect of heat treatment (650°C/3hrs on microstructure and impact toughness of the material. Initial microstructural observation identified prior-β grain along the building direction before and after heat treatment. In addition, the material formed a fully martensite structure before heat treatment, and after heat treatment, α and β phase were formed simultaneously. Charpy impact tests were conducted. The average impact energy measured as 6.0 J before heat treatment, and after heat treatment, the average impact energy increased by approximately 20% to 7.3 J. Fracture surface observation after the impact test showed that both alloys had brittle characteristics on macro levels, but showed ductile fracture characteristics and dimples at micro levels.

  10. Impact toughness of laser surface alloyed Aluminium

    CSIR Research Space (South Africa)

    Mabhali, Luyolo AB

    2012-03-01

    Full Text Available ]. The impact test is a standardized strain-rate test which determines the amount of energy absorbed by a material during fracture. The tests were performed on a Tinius Olsen impact machine. The impact tester consists of a sample holder, a swinging pendulum.... The pendulum axe was raised to a latched position and locked before each test. The energy was set to the maximum position and the pendulum released. The pendulum axe strikes the specimen directly opposite the notch. The energy reading after fracturing...

  11. Correlation between standard Charpy and sub-size Charpy test results of selected steels in upper shelf region

    Science.gov (United States)

    Konopík, P.; Džugan, J.; Bucki, T.; Rzepa, S.; Rund, M.; Procházka, R.

    2017-02-01

    Absorbed energy obtained from impact Charpy tests is one of the most important values in many applications, for example in residual lifetime assessment of components in service. Minimal absorbed energy is often the value crucial for extending components service life, e.g. turbines, boilers and steam lines. Using a portable electric discharge sampling equipment (EDSE), it is possible to sample experimental material non-destructively and subsequently produce mini-Charpy specimens. This paper presents a new approach in correlation from sub-size to standard Charpy test results.

  12. Evaluation of dynamic fracture toughness for Yong Gwang unit 5 reactor pressure vessel materials (Baseline Tests)

    Energy Technology Data Exchange (ETDEWEB)

    Chi Se Hwan; Kim, Joo Hag; Hong, Jun Hwa; Kwon, Sun Chil; Lee, Bong Sang [Korea Atomic Energy Research Institute, Taejon (Korea)

    1999-10-01

    The dynamic fracture toughness (K{sub d}) of intermediate shell and its weld in SA 508 CI. 3 Yong Gwang 5 reactor pressure vessel was determined and evaluated. Precracked thirty six Charpy specimens were tested by using an instrumented impact tester. The purpose of present work is to evaluate and confirm the un-irradiated dynamic fracture toughness and to provide pre-irradiation baseline data for future evaluation on dynamic fracture toughness change during operation. 18 refs., 5 figs., 5 tabs. (Author)

  13. Impact toughness of high strength low alloy TMT reinforcement ...

    Indian Academy of Sciences (India)

    Unknown

    method requiring small investment, test specimens are of small size and simpler to machine (Wullaert 1970, 1974). The Charpy test data can be used to predict the perfor- mance of material in service condition. It reproduces the ductile to brittle transition of steel in about the same temperature range as it is actually observed ...

  14. Recent advances on Charpy specimen reconstitution techniques

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, Arnaldo H.P.; Lobo, Raquel M.; Miranda, Carlos Alexandre J., E-mail: aandrade@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2017-07-01

    Charpy specimen reconstitution is widely used around the world as a tool to enhance or supplement surveillance programs of nuclear reactor pressure vessels. The reconstitution technique consists in the incorporation of a small piece from a previously tested specimen into a compound specimen, allowing to increase the number of tests. This is especially important if the available materials is restricted and fracture mechanics parameter have to be determined. The reconstitution technique must fulfill some demands, among them tests results like the original standard specimens and the loaded material of the insert must not be influenced by the welding and machining procedure. It is known that reconstitution of Charpy specimens may affect the impact energy in a consequence of the constraint of plastic deformation by the hardened weldment and HAZ. This paper reviews some recent advances of the reconstitution technique and its applications. (author)

  15. ANALYSIS OF STRESS STATE AND INERTIAL PROPERTIES OF A PENDULUM USED FOR CHARPY IMPACT TEST ON PLASTICS

    Directory of Open Access Journals (Sweden)

    COJOCARU Vasile

    2016-11-01

    Full Text Available The laboratory equipment used for testing the impact behavior of plastics uses low impact energies. In the last years were developed constructive solutions of monobloc pendulums, in order to ensure design and manufacturing simplicity. The paper presents the possibilities of optimizing a 15 J pendulum using 3D CAD design and finite element analysis. It highlights the possibilities for quick determination of the pendulum inertial properties ensuring the correlation between the position of mass center and the position of impact center of pendulum. A finite element analysis of maximum stress and displacement was performed correlated with the study of inertial properties.

  16. Charpy impact test results of four low activation ferritic alloys irradiated at 370{degrees}C to 15 DPA

    Energy Technology Data Exchange (ETDEWEB)

    Schubert, L.E.; Hamilton, M.L.; Gelles, D.S. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-10-01

    Miniature CVN specimens of four low activation ferritic alloys have been impact tested following irradiation at 370{degrees}C to 15 dpa. Comparison of the results with those of control specimens indicates that degradation in the impact behavior occurs in each of these four alloys. The 9Cr-2W alloy referred to as GA3X and the similar alloy F82H with 7.8Cr-2W appear most promising for further consideration as candidate structural materials in fusion energy system applications. These two alloys exhibit a small DBTT shift to higher temperatures but show increased absorbed energy on the upper shelf.

  17. AN INVESTIGATION OF METALLURGICAL FACTORS WHICH AFFECT THE FRACTURE TOUGHNESS OF ULTRA HIGH STRENGTH STEELS

    Energy Technology Data Exchange (ETDEWEB)

    Wood, William E.; Parker, Earl R.; Zackay, Victor F.

    1973-05-01

    The relationship between microstructure, heat treatment and room temperature fracture toughness has been determined for the low alloy ultra-high strength steels 4130, 4330, 4340, 4140 and 300-M. Optical metallography, microprobe analysis, and scanning electron microscopy were used to characterize the structure and morphology, while both Charpy V-notch impact tests and plane strain fracture toughness tests were used to determine the fracture properties. The normal commercial heat treatment resulted in the formation of some bainite in all the alloys. MnS inclusions on prior austenite grain boundaries were found to initiate cracks during loading. By increasing the austenitizing temperature to l200 C, the fracture toughness could be increased by at least 60%. For some alloys increasing the severity of the quench in conjunction with the higher austenitizing temperatures resulted in further increases in the fracture toughness, and the elimination of any observable upper bainite. There was no correlation between the Charpy impact test results and the fracture toughness results. The alloys 4130, 4140, 4340 all showed a severe intergranular embrittlement when austenitized at high temperatures and tempered above 200 C, while the alloys 4330 and 300-M exhibited no drop in toughness for the same heat treatment conditions. The as-quenched tensile specimens had a very low 'micro' yield strength which rapidly increased to the level of the 'macro' yield strength when tempered.

  18. 46 CFR 154.605 - Toughness test.

    Science.gov (United States)

    2010-10-01

    ... of this chapter. (b) If subsize test specimens are used for the Charpy V-notch toughness test, the... 46 Shipping 5 2010-10-01 2010-10-01 false Toughness test. 154.605 Section 154.605 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SAFETY STANDARDS FOR...

  19. Fracture toughness of weld metal samples removed from a decommissioned Magnox reactor pressure vessel

    Energy Technology Data Exchange (ETDEWEB)

    Bolton, C.J.; Bischler, P.J.E.; Wootton, M.R.; Moskovic, R.; Morri, J.R.; Pegg, H.C.; Haines, A.B.; Smith, R.F.; Woodman, R

    2002-08-01

    Submerged-arc welds in Magnox RPVs are expected to show substantial shifts in ductile-to-brittle transition temperature (DBTT), due to their high copper content, and also because of a contribution from intergranular fracture. For structural integrity arguments, the fracture toughness of irradiated welds is predicted by applying an irradiation shift in DBTT to a start-of-life toughness curve. The shift is obtained from a trend curve derived from Charpy impact data. An uncertainty allowance is obtained by combining uncertainty contributions in start-of-life fracture toughness and shifts, including a contribution from uncertainties in neutron dose. Through-thickness samples were removed from four submerged-arc welds in a decommissioned Magnox RPV at Trawsfynydd. Fracture toughness tests were made on pre-cracked Charpy geometry specimens made from the samples, in order to compare the measured toughnesses with those predicted for irradiated material. Specimens were tested from several positions along the welds and also at four different through-thickness locations with dpa doses varying by a factor of more than 2. The paper presents the results of nearly 400 toughness measurements and demonstrates that the prediction methodology is sound.

  20. Impact Toughness of Steel WMD After TIG Welding

    Directory of Open Access Journals (Sweden)

    Węgrzyn T.

    2017-09-01

    Full Text Available The material selected for this investigation was low alloy weld metal deposit after TIG welding with various amount of oxygen in weld metal deposit (WMD. After TIG process it is difficult to get proper amount of oxygen in WMD on the level much lower than 350 ppm. The highest impact toughness of low alloy WMD corresponds with the amount of oxygen in WMD above 350 ppm. In the paper focuses on low alloy steel after innovate welding method with micro-jet cooling that could be treated as a chance on rising amount of oxygen in weld. Weld metal deposit (WMD was carried out for TIG welding with micro-jet cooling with various amount of oxygen in WMD. In that paper various gas mixtures (gas mixtures Ar-O2 and Ar-CO2 were tested for micro-jet cooling after TIG welding. An important role in the interpretation of the results can give methods of artificial intelligence.

  1. Grain size and temperature influence on the toughness of a CuAlBe shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Albuquerque, Victor Hugo C. de, E-mail: victor.albuquerque@fe.up.pt [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Laboratorio de Solidificacao Rapida LSR, Cidade Universitaria, S/N 58059-900 Joao Pessoa, PB (Brazil); Melo, Tadeu Antonio de A, E-mail: tadeu@lsr.ct.ufpb.br [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Laboratorio de Solidificacao Rapida LSR, Cidade Universitaria, S/N 58059-900 Joao Pessoa, PB (Brazil); Gomes, Rodinei M., E-mail: gomes@lsr.ct.ufpb.br [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Laboratorio de Solidificacao Rapida LSR, Cidade Universitaria, S/N 58059-900 Joao Pessoa, PB (Brazil); Lima, Severino Jackson G. de, E-mail: jackson@lsr.ct.ufpb.br [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Laboratorio de Solidificacao Rapida LSR, Cidade Universitaria, S/N 58059-900 Joao Pessoa, PB (Brazil); Tavares, Joao Manuel R.S., E-mail: tavares@fe.up.pt [Faculdade de Engenharia da Universidade do Porto (FEUP), Departamento de Engenharia Mecanica (DEMec)/Instituto de Engenharia Mecanica e Gestao Industrial INEGI, Rua Dr. Roberto Frias, S/N 4200-465 Porto (Portugal)

    2010-11-25

    Research highlights: {yields} This work evaluated the capacity of a CuAlBe alloy to absorb energy until rupture. {yields} The V-notch Charpy test was adopted at -150, -100, -50, 0, 50, 100 and 150 deg. C. {yields} Charpy tests were complemented by DSC, DSC with optical microscope and by SEM. {yields} First work to analyze the toughness of a CuAlBe alloy based on the Charpy test. {yields} The results are of relevant value to enhance the understanding of the CuAlBe alloy. - Abstract: This work is a study of the influence of grain size and temperature on the toughness of CuAlBe shape memory alloys with (CuAlBeNbNi) and without NbNi (CuAlBe) grain refiner elements. The toughness analysis was based on the V-notch Charpy impact test under temperatures of -150, -100, -50, 0, 50, 100 and 150 deg. C. A statistical analysis of the results led to the conclusion that the toughness of both alloys was influenced by temperature and grain size. The CuAlBeNbNi alloy absorbed higher impact energy than the CuAlBe alloy showing that the refining elements improved the toughness of the alloy. To confirm and complement these findings, the fracture surfaces were evaluated by stereomicroscopy. Smooth homogeneous surfaces and rough heterogonous surfaces were detected for the CuAlBeNbNi and CuAlBe alloys, respectively. Predominately brittle zones were confirmed by scanning electron microscopy in both alloys. Furthermore, to determine the phase transformation temperatures and the associated microstructures, the alloys were assessed by conventional differential scanning calorimetry (DSC) and DSC with optical microscopy.

  2. Evaluation of hydrogen embrittlement and temper embrittlement by key curve method in instrumented Charpy test

    Directory of Open Access Journals (Sweden)

    Makita A.

    2010-06-01

    Full Text Available Instrumented Charpy test was conducted on small sized specimen of 21/4Cr-1Mo steel. In the test the single specimen key curve method was applied to determine the value of fracture toughness for the initiation of crack extension with hydrogen free, KIC, and for hydrogen embrittlement cracking, KIH. Also the tearing modulus as a parameter for resistance to crack extension was determined. The role of these parameters was discussed at an upper shelf temperature and at a transition temperature. Then the key curve method combined with instrumented Charpy test was proven to be used to evaluate not only temper embrittlement but also hydrogen embrittlement.

  3. Impact toughness of high strength low alloy TMT reinforcement ...

    Indian Academy of Sciences (India)

    ... of copper–molybdenum and copper–chromium rebars was 52 J. The lower toughness of phosphorus steel is attributed to solid solution strengthening and segregation of phosphorus to grain boundaries. Due to superior corrosion resistance, copper–phosphorus TMT rebar is a candidate material in the construction sector.

  4. Degradation of mechanical properties of cast Cr-Mo-V and Cr-W-V steam turbine casings after long-term service at elevated temperatures: Pt. 1:; Tensile properties, brittle fracture strength and Charpy impact properties

    Energy Technology Data Exchange (ETDEWEB)

    Holzmann, M.; Man, J.; Vlach, B. (Ceskoslovenska Akademie Ved, Brno (Czech Republic). Ustav Fyzikalni Metalurgie); Krumpos, J. (Czechoslovak Academy of Sciences, Plzen (Czech Republic). Inst. of Technology and Reliability of Machine Structures)

    1994-01-01

    The effect of elevated service temperature on tensile properties, brittle fracture strength and on the Charpy V-notch transition curve of Cr-Mo-V and Cr-W-V cast steels is presented. A lowering of the yield stress and ultimate tensile stress (softening) was observed with both types of cast steels after long-term exposure at elevated temperatures. The brittle fracture strength of Cr-Mo-V steel established by testing both the smooth bars [sigma][sub BF] and notch specimens [sigma][sub BF][sup *] at low temperatures was not influenced during exposure at elevated temperatures. The fracture appearance transition temperature (FATT) of this steel determined by impact Charpy test was also not affected by long-term exposure. Thus, it could be concluded that this type of cast steel was not embrittled during operation. On the contrary, a decrease in brittle fracture strength [sigma][sub BF][sup *] (250 MPa) and an increase in FATT (50[sup o]C) were observed in the Cr-W-V steel after 2 x 10[sup 5] h of service. (Author)

  5. 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.

  6. Fracture toughness and the master curve for modified 9Cr-1Mo steel

    Science.gov (United States)

    Yoon, Ji-Hyun; Yoon, Eui-Pak

    2006-12-01

    Modified 9Cr-1Mo steel is a primary candidate material for the reactor pressure vessel of a Very High Temperature Gas-Cooled Reactor (VHTR) in the Korean Nuclear Hydrogen Development and Demonstration (NHDD) program. In this study, the T0 reference temperature, J-R fracture resistance and Charpy impact properties were evaluated for commercial Grade 91 steel as part of the preliminary testing for a selection of the RPV material for the VHTR. The fracture toughness of the modified 9Cr-1Mo steel was compared with that of SA508-Gr.3. The objective of this study was to obtain the pre-irradiation fracture toughness properties of the modified 9Cr-1Mo steel as reference data for an investigation of radiation effects. Charpy impact properties of the modified 9Cr-1Mo steel were similar to those of SA508-Gr.3. T0 reference temperatures were measured as -67.7 and -72.4°C from the tests with standard PCVN (pre-cracked Charpy V-notch) and half-sized PCVN specimens respectively, which were similar to the results for SA508-Gr.3. The KJc values of the modified 9Cr-1Mo steel with the test temperatures are successfully expressed by the Master Curve. The J-R fracture resistance of the modified 9Cr-1Mo steel at room temperature was nearly identical to that of SA508-Gr.3; in contrast, it was slightly higher at an elevated temperature.

  7. Impact toughness of EK-181 ferritic-martensitic chromium (12%) steel under loading by concentrated bending

    Science.gov (United States)

    Chernov, V. M.; Ermolaev, G. N.; Leont'eva-Smirnova, M. V.

    2010-07-01

    The low-temperature fracture of a high-temperature low-activated ferritic-martensitic EK-181 chromium (12%) steel (RUSFER-EK-181: Fe-12Cr-2W-V-Ta-B) is studied using impact and static concentrated bending tests as a function of the specimen dimensions (standard, small), the type of stress concentrator (V-shaped notch, fatigue crack), and the temperature (from -196 to +100°C). The ductile-brittle transition temperature falls in the range from -85 to +35°C. The temperature dependences of stress-intensity factor K Ic and fracture toughness J Ic are determined. The severest type of impact toughness tests is represented by tests of V-notched specimens with an additional fatigue crack and two lateral V-shaped notches (three-sided V-shaped notch with a central fatigue crack). The fracture energy of the steel depends on the type of stress concentrator and the specimen dimensions and is determined by the elastic energy and the plastic deformation conditions in the near-surface layers of a specimen, which are controlled by the lateral notches. At the same test temperature, the impact toughness and the fracture toughness are interrelated. Irrespective of the type of specimen (including notches and a fatigue crack), the ferritic-martensitic steel exhibits the same fracture mechanism.

  8. Visual analysis of ductility/brittleness of welding fracture points on charpy test specimens using graphical blocks on field programmable gate arrays

    Science.gov (United States)

    Tickle, Andrew J.; Camargo-Rodriguez, Anyela; Smith, Jeremy S.

    2008-09-01

    The charpy impact is a technique used to evaluate the toughness of an engineering material that determines the amount of energy absorbed by it during fracture. Initially, measurements were estimated manually and later replaced by a PC version. This study reports the development of the Field Programmable Gate Array (FPGA) portable version. The FPGA based version allows easy analysis of samples without the need of sending them to a lab for analysis. The process, presented here, as the original, is based on measuring the percent of crystal in the test sample after impact, to determine if the material is ductile or brittle. The FPGA version, adapted under the MATLAB Simulink environment, shows a graphical block representation of the charpy impact PC version. An important asset of the FPGA version is its portability, it has to be easily modified and downloaded onto a device to estimate the percent of brittle fracture of the broken Charpy surface. The beauty of the DSP Builder programme is that it allows the model to be compiled to various types of optimised code for any Altera FPGA device. To provide a firm basis for scientific comparison to the new FPGA system, images already analysed via the PC based Java system were also used for testing and comparison purposes. The FPGA system converts the image into an 8 bit grayscale image and analyses it in a 5x5 sampling window. This produces texture features that can be used in a comparison system, similar to the Support Vector Machine (SVM) used in the original. The output is a signal that states the material being tested is brittle or not via an output of '1' for brittle and a '0' for ductile. A detailed pixel by pixel analysis of the various output images is then investigated to state the percentage difference between the PC and FPGA based systems.

  9. Irradiation effects on fracture toughness of two high-copper submerged-arc welds, HSSI Series 5. Volume 1, Main report and Appendices A, B, C, and D

    Energy Technology Data Exchange (ETDEWEB)

    Nanstad, R.K.; Haggag, F.M.; McCabe, D.E.; Iskander, S.K.; Bowman, K.O. [Oak Ridge National Lab., TN (United States); Menke, B.H. [Materials Engineering Associates, Inc., Lanham, MD (United States)

    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{sub 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 {times} 10{sup 19} neutrons/cm{sup 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}{radical}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{sub min} parameter which affects the curve shape.

  10. Impact toughness of laser alloyed aluminium AA1200 alloys

    CSIR Research Space (South Africa)

    Mabhali, Luyolo AB

    2013-08-01

    Full Text Available Laser surface alloying of aluminium AA1200 was performed with a 4kW Nd:YAG laser and impact resistance of the alloys was investigated. The alloying powders were a mixture of Ni, Ti and SiC in different proportions. Surfaces reinforced...

  11. Martensitic stainless steel AISI 420—mechanical properties, creep and fracture toughness

    Science.gov (United States)

    Brnic, J.; Turkalj, G.; Canadija, M.; Lanc, D.; Krscanski, S.

    2011-11-01

    In this paper some experimental results and analyses regarding the behavior of AISI 420 martensitic stainless steel under different environmental conditions are presented. That way, mechanical properties like ultimate tensile strength and 0.2 percent offset yield strength at lowered and elevated temperatures as well as short-time creep behavior for selected stress levels at selected elevated temperatures of mentioned material are shown. The temperature effect on mentioned mechanical properties is also presented. Fracture toughness was calculated on the basis of Charpy impact energy. Experimentally obtained results can be of importance for structure designers.

  12. Investigation of temperature dependence of fracture toughness in high-dose HT9 steel using small-specimen reuse technique

    Science.gov (United States)

    Baek, Jong-Hyuk; Byun, Thak Sang; Maloy, Start A.; Toloczko, Mychailo B.

    2014-01-01

    The temperature dependence of fracture toughness in HT9 steel irradiated to 3-145 dpa at 380-503 °C was investigated using miniature three-point bend (TPB) fracture specimens. A miniature-specimen reuse technique has been established: the tested halves of subsize Charpy impact specimens with dimensions of 27 mm × 3 mm × 4 mm were reused for this fracture test campaign by cutting a notch with a diamond-saw in the middle of each half, and by fatigue-precracking to generate a sharp crack tip. It was confirmed that the fracture toughness of HT9 steel in the dose range depends more strongly on the irradiation temperature than the irradiation dose. At an irradiation temperature specimens with relatively lower irradiation and test temperatures. In this discussion, these TPB fracture toughness data are compared with previously published data from 12.7 mm diameter disc compact tension (DCT) specimens.

  13. A newly developed snow vehicle (SM100S) for Antarctica. Part 3: Low temperature toughness of the welded joints of the structural steel

    Science.gov (United States)

    Sakui, Shin; Nakajima, Masashi

    1992-11-01

    For the purpose of developing a new snow vehicle (common use at temperature about -50 C) for the deep ice coring project at Dome Fuji, East Antarctica, the low temperature toughness of the welded joints of structural steel was investigated. It is empirically well known that in case of vehicles employed in a cold air temperature of about -50 C, the low temperature brittle fracture of the structural members does not take place, if one uses semi-killed or killed steel, for which 50 percent FATT's (fracture appearance transition temperature) of the Charpy impact test is about -50 C and Charpy impact values at -50 C are 20 to 29 J/sq cm. In the present report, the Charpy impact test has been performed for both single pass SMAW (shield metal arc welding) and CO2 arc welded joints of JIS (Japan Industrial Standards) steels of SS400, SL2N255, STPL380, and STPL450. The test results show that the JIS steels of SL2N255 and STPL450 can be used for the new vehicle, considering their toughness.

  14. 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.

  15. Degradation of impact fracture during accelerated aging of weld metal on microalloyed steel; Degradacion de la tenacidad al impacto durante el envejecimiento acelerado de soldadura en acero microaleado

    Energy Technology Data Exchange (ETDEWEB)

    Vargas-Arista, B.; Hallen, J. M.; Albiter, A.; Angeles-Chavez, C.

    2008-07-01

    The effect of accelerated aging on the toughness and fracture of the longitudinal weld metal on an API5L-X52 line pipe steel was evaluated by Charpy V-notch impact test, fracture analysis and transmission electron microscopy. Aging was performed at 250 degree centigrade for 100 to 1000 h. The impact results indicated a significant reduction in the fracture energy and impact toughness as a function of aging time, which were achieved by the scanning electron microscope fractography that showed a decrease in the vol fraction of microvoids by Charpy ductile failure with the aging time, which favored the brittle fracture by transgranular cleavage. The minimum vol fraction of microvoids was reached at 500 h due to the peak aged. The microstructural analysis indicated the precipitation of transgranular iron nano carbides in the aged specimens, which was related to the deterioration of toughness and change in the ductile to brittle behavior. (Author) 15 refs.

  16. Influence of fast neutron irradiation on dynamic fracture toughness of Bainitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Bilek, Z.; Buchar, J.; Martinez Esnaola; Maria Bastero, J.

    1988-09-01

    This paper describes the results of an investigation of the influence of fast neutron irradiation on mechanical and fracture properties of a bainitic steel under impulsive loading produced by means of the Hopkinson split pressure bar (HSPB) method. The general analysis of the HSPB technique is outlined briefly and applications to the irradiated steel are considered in greater detail. The special crack tip elements suitable for accurate dynamic elastic finite element computations were used to calculate the dynamic fracture toughness K/sub Id/ from testing the wedge loaded compact specimens at very high strain rates over wide temperature range from -196/sup 0/C to 25/sup 0/C. The particular attention is paid to the comparison of the K/sub Id/ values and the K/sub Id/ values obtained by instrumented Charpy impact test at somewhat slower loading rates. It is shown that HSPB data for irradiated specimens represent the minimum fracture toughness for given steel.

  17. Effects of alloying element contents on the toughness and transition behavior in the SA508 Gr. 4N Ni-Mo-Cr low alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki Hyoung; Park, Sang Gyu; Wee, Dang Moon [KAIST, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2009-05-15

    Low alloy steels used as materials for reactor pressure vessels (RPVs) determine the safety and the life span of reactors. Currently, SA508 Gr.3 low alloy steel is generally used for RPV materials. But, for larger capacity and long-term durability of the next generation RPVs, materials that have much better properties are needed, such as strength, toughness and irradiation resistance. SA508 Gr.4N low alloy steel shows good mechanical properties due to high Ni and Cr contents in comparison with the currently used reactor pressure vessel steels. Materials for RPVs suffer a decrease of toughness due to an embrittlement of the materials by neutron irradiation, especially in ferritic steels. This toughness loss causes an increase in the transition temperature, and then a brittle fracture could occur. Therefore, for an integrity assessment of low alloy steels as RPVs, an accurate evaluation of the transition behavior is needed, such as fracture and impact toughness. In this study, the toughness and transition behavior of SA 508 Gr.4N low alloy steels, which have different Ni, Cr and Mo, were evaluated in the transition region. And the applicability of the test results for Master-Curve method was assessed. Additionally, differences between influences of alloying elements contents on Charpy impact toughness and fracture toughness were discussed in terms of microstructural features.

  18. Charpy V, an application in Mat lab; Charpy V, una aplicacion en Matlab

    Energy Technology Data Exchange (ETDEWEB)

    Castillo M, J.A.; Torres V, M. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)

    2003-07-01

    The obtained results with the system Charpy V{sub V}1 designed in Mat lab for the estimate of parameters of three mathematical models are shown. The adjustment of data is used to determine the fracture energy, the lateral expansion and the percentage of ductility of steels coming from the reactor vessels of Laguna Verde, Veracruz. The data come from test tubes type Charpy V of irradiated material and not irradiated. To verify our results they were compared with those obtained by General Electric of data coming from the Laguna Verde nuclear power plant. (Author)

  19. Impact Fracture Study of Filled Epoxy Resins

    OpenAIRE

    Pedro V. Vasconcelos; F. Jorge Lino; António Magalhães; Rui J. Neto

    2004-01-01

    Epoxy-based composites moulds are frequently used for wax and polymer materials injection.Tri-phase materials, composed by an epoxy resin, aluminium particles and milled glass orcarbon fibres were produced with better mechanical and thermal performances than the single materials,increasing the competitiveness of the epoxy rapid tooling processes. Charpy Impact testswere employed to obtain a qualitative indication of the composites toughness. The electronic instrumentationof these tests allows...

  20. On the Use of the Master Curve based on the Precracked Charpy Specimen

    Energy Technology Data Exchange (ETDEWEB)

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

    1999-08-01

    Recently, worldwide interest has been demonstrated in the evaluation of the use of the Master Curve approach to characterize fracture toughness of ferritic steels in the transition regime. This was acknowledged by the recent release of the ASTM Standard Test Method for Determination of Reference Temperature, T{sub 0}, for Ferritic Steels in the Transition Range (E1921). The present work aims to investigate the use of the Charpy specimen along with the Master Curve approach to derive the fracture toughness behaviour of reactor pressure vessel steels. Therefore, four well characterized and documented reactor pressure vessel steels were selected. A large experimental program to measure fracture toughness with Charpy size specimens was carried out. Four important aspects were investigated: (1) the T0 determination as a function of test temperature; (2) the E1921 specimen size requirement (factor M=30); (3) the censoring procedure for specimens not satisfying the E1921 size requirements; (4) the estimation of the fracture toughness lower bound, and its comparison to the ASME KIC curve. It is found that within the experimental and statistical uncertainties, the reference temperature T0 is not affected by the test temperature, even when data are not valid according to E1921 requirements. By application of the censoring procedure, the determination of the reference temperature may lead to non conservative results. Comparison to larger specimen size suggests the use of M=60 rather than 30 to limit the loss of constraint, in agreement with finite element calculations. Nevertheless, the differences are not large enough to be statistically significant. The lower bound based on the Master Curve is very close to the experimental lower bound, while the ASME K{sub IC} curve trends to be over conservative. Replacing RT{sub NDT} by the new index, RT{sub To}, in the ASME KIC equation reduces this over conservatism.

  1. Factors affecting miniature Izod impact strength of tungsten-fiber-metal-matrix

    Science.gov (United States)

    Winsa, E. A.; Petrasek, D. W.

    1973-01-01

    The miniature Izod and Charpy impact strengths of copper, copper-nickel, and nickel-base superalloy uniaxially reinforced with continuous tungsten fibers were studied. In most cases, impact strength was increased by increasing fiber or matrix toughness, decreasing fibermatrix reaction, increasing test temperature, hot working, or heat treating. Notch sensitivity was reduced by increasing fiber content or matrix toughness. An equation relating impact strength to fiber and matrix properties and fiber content was developed. Program results imply that tungsten alloy-fiber/superalloy matrix composites can be made with adequate impact resistance for turbine blade or vane applications.

  2. Impact toughness of cellulose-fiber reinforced polypropylene : influence of microstructure in laminates and injection molded composites

    Science.gov (United States)

    Craig Clemons; Daniel Caulfield; A. Jeffrey Giacomin

    2003-01-01

    Unlike their glass reinforced counterparts, microstructure and dynamic fracture behavior of natural fiber-reinforced thermoplastics have hardly been investigated. Here, we characterize the microstructure of cellulose fiber-reinforced polypropylene and determined its effect on impact toughness. Fiber lengths were reduced by one-half when compounded in a high-intensity...

  3. The effect of aging treatment on the fracture toughness and impact strength of injection molded Ni-625 superalloy parts

    Energy Technology Data Exchange (ETDEWEB)

    Özgün, Özgür, E-mail: oozgun@bingol.edu.tr [Bingol University, Faculty of Engineering and Architecture, Mechanical Eng. Dep., 12000 Bingol (Turkey); Yılmaz, Ramazan [Sakarya University, Technology Faculty, Metallurgy and Materials Eng. Dep., 54187 Sakarya (Turkey); Özkan Gülsoy, H. [Marmara University, Technology Faculty, Metallurgy and Materials Eng. Dep., 34722 Istanbul (Turkey); Marmara University, Nanotechnology & Biomaterials Applied and Research Centre, 34722 Istanbul (Turkey); Fındık, Fehim [Sakarya University, Technology Faculty, Metallurgy and Materials Eng. Dep., 54187 Sakarya (Turkey)

    2015-10-15

    In this study, the effect of aging heat treatment on fracture toughness and impact strength of Ni-625 superalloy fabricated by using powder injection molding (PIM) method was examined. After a feedstock was prepared by mixing the prealloyed Ni-625 superalloy powder, which was fabricated by gas atomisation, with a polymeric binder system and then it was granulated, it was shaped through the use of injection. The molded specimens were sintered at 1300 °C for 3 h after a two-stage debinding process. Once the sintered specimens were treated in the solution at 1150 °C for 2 h, they were quenched. Aging treatment was performed by keeping specimens at 745 °C for 22 h. Fracture toughness and impact tests were performed on sintered and aged specimens. Microstructure examinations were performed by using optical microscope, scanning electron microscope, and transmission electron microscope. The results revealed that aging heat treatment led to the formation of some carbides and intermetallic phases in the microstructure. While the hardness of the aged specimens increased due to these phases, their fracture toughness and impact strength values decreased. - Highlights: • Ni-625 superalloy components were produced by means of powder injection molding. • The produced components were subjected to aging treatment. • Aging process provided approximately 50% increase in the hardness of components. • Intermetallic precipitates, carbides and TCP phases occurred within the aged parts. • Fracture toughness and impact strength values decreased due to the hard phases.

  4. Fracture Toughness and Impact Strength of High-Volume Class-F Fly Ash Concrete Reinforced with Natural San Fibres

    Directory of Open Access Journals (Sweden)

    Rafat SIDDIQUE

    2008-06-01

    Full Text Available Results of experimental investigation carried out to study the effects of addition of natural san fibres on the fracture toughness and impact strength of high-volume fly ash concrete are presented in this paper. San fibres belong to the category of ‘Natural Bast Fibres’, also known as ‘Sunn Hemp’. Its scientific (botanical name is Crotalaria Juncea. It is mostly grown in the Indian Sub-Continent, Brazil, Eastern and Southern Africa, and in some parts of the U.S.A. Initially, a control mixture without fly ash was designed. Then, cement was replaced with three percentages (30, 40 and 50% of low-calcium (Class F fly ash. Three percentages of san fibres (0.30, 0.60 and 0.90%, having 25 mm length, were used. Tests were performed for compressive strength, fracture toughness, and impact strength at the ages of 28 and 91 days.The test results indicated that the replacement of cement with fly ash decreased the compressive strength and fracture toughness, and had no significant effect on the impact strength of plain (control concrete. Addition of san fibres did not affect significantly the compressive strength, increased the fracture toughness and impact strength of high-volume fly ash concrete as the percentage of fibres increased.

  5. Effect of Heat Treatment Technique on the Low Temperature Impact Toughness of Steel EQ70 for Offshore Structure

    Science.gov (United States)

    Tao, Su-Fen; Xia, Yun-Jin; Wang, Fu-Ming; Li, Jie; Fan, Ding-Dong

    2017-09-01

    Circle quenching and tempering (CQ&T), intercritical quenching and tempering (IQ&T) and regular quenching and tempering (Q&T) were used to study the influence of heat treatment techniques on the low temperature impact toughness of steel EQ70 for offshore structure. The steels with 2.10 wt. % Ni (steel A) and 1.47 wt. % Ni (steel B) were chosen to analyze the effect of Ni content on the low temperature impact toughness of steel EQ70 for offshore structure. The fracture morphologies were examined by using a scanning electron microscope (SEM, JSM-6480LV), and microstructures etched by 4 vol. % nitric acid were observed on a type 9XB-PC optical microscope. The results show that the impact toughness of steel A is higher than that of steel B at the same test temperature and heat treatment technique. For steel B, the energy absorbed is, in descending order, CQ&T, Q&T and IQ&T, while for steel A, that is CQ&T, IQ&T and Q&T. The effects of heat treatment on the low temperature impact toughness are different for steels A and B, the absorbed energy changes more obviously for steel A. The results can be significant references for actual heat treatment techniques in steel plant.

  6. Effects of Core-Shell Rubber (CSR) Nanoparticles on the Fracture Toughness of an Epoxy Resin at Cryogenic Temperatures

    Science.gov (United States)

    Wang, J.; Cannon, S. A.; Schneider, J. A.

    2008-01-01

    This study investigates the effects of core-shell rubber (CSR) nanoparticles on the fracture toughness of an epoxy resin at liquid nitrogen (LN2) temperatures. Varying amounts of Kane Ace (Registered TradeMark) MX130 toughening agent were added to a commercially available EPON 862/W epoxy resin. Resulting fracture toughness was evaluated by the use of Charpy impact tests conducted on an instrumented drop tower. The size and distribution of the CSR nanoparticles were characterized using Transmission Electric Microscopy (TEM) and Small Angle X-ray Scattering (SAXS). Up to nominal 4.6% addition of the CSR nanoparticles, resulted in a nearly 5 times increase in the measured breaking energy. However, further increases in the amount of CSR nanoparticles had no appreciable affect on the breaking energy.

  7. Development of a reconstitution system of Charpy probes for the surveillance of vessels in nucleo electric plants; Desarrollo del sistema de reconstitucion de probetas Charpy para la vigilancia de vasijas en nucleoelectricas

    Energy Technology Data Exchange (ETDEWEB)

    Romero C, J.; Hernandez, R.; Fernandez, F.; Gonzalez M, A. [ININ, Km. 36.5 Carretera Mexico-Toluca, AP.18-1027, 11801 Mexico D.F. (Mexico)]. e-mail: jrc@nuclear.inin.mx

    2007-07-01

    This work describes the development of a welding system, for the rebuilding of halves of Charpy test tubes, the rebuilding consists on welding two implants in those ends of these halves of test tubes, in these welding the main requirement is not to alter the mechanical properties in a minimum volume of 1 cm{sup 3}, the rebuilding is medullary in the surveillance programs of the reactor vessel. In these programs, the mechanical state of the vessel is evaluated, for it there are surveillance capsules with a Charpy witness test tubes series, subjected to a neutron flow similar or bigger to that of the vessel. The objective is to evaluate in advance on the vessel fragilization grade its life design. However the number of capsules with the witness test tubes it is only for the plant design life and at the moment the nucleo electric, negotiates an extension of life of these, until for 20 more years, of there the importance of this material witness's that stores the information of the damage accumulated by the neutron flow. This material requires to be taken advantage it after being rehearsed and the normative one settles down as obligatory to qualify the rebuilding process with all the requirements settled down in the ASTM Designation: E 1253-99 'Standard Guide for Reconstitution of irradiated Charpy-Sized Specimens', to obtain other reconstituted Charpy test tubes that are again introduced in the reactor. When being reconstituted the halves of the original test tubes it is obtained double reconstituted Charpy test tubes. Half of the test tubes they are used in the surveillance program of the vessel, with the surpluses test tubes, it can determine the fracture toughness, property of the material used in the extension methodology of life of vessel. (Author)

  8. Fracture Toughness of Z3CN20.09M Cast Stainless Steel with Long-Term Thermal Aging

    Science.gov (United States)

    Yu, Weiwei; Yu, Dunji; Gao, Hongbo; Xue, Fei; Chen, Xu

    2017-09-01

    Accelerated thermal aging tests were performed at 400 °C for nearly 18,000 h on Z3CN20.09M cast stainless steel which was used for primary coolant pipes of nuclear power plants. A series of Charpy impact tests were conducted on Z3CN20.09M after different long-term thermal aging time. The test results indicated that the Charpy impact energy of Z3CN20.09M cast stainless steel decreased rapidly at an early stage and then almost saturated after thermal aging of 10,000 h. Furthermore, J-resistance curves were measured for CT specimens of longitudinal and circumferential pipe orientations. It showed that there was no obvious difference in the fracture characteristics of Z3CN20.09M in different sampling directions. In addition, the observed stretch zone width (SZW) revealed that the value of initiation fracture toughness J SZW was significantly lower than that of fracture toughness J IC, indicating a low actual crack initiation energy due to long-term thermal aging.

  9. Large strain bulk deformation and brittle tough transitions in polyethylenes

    CERN Document Server

    Hillmansen, S

    2001-01-01

    Some tough, crystalline polymers can fail by fast brittle fracture. This thesis explores the role of ductile 'shear lips', which form at the fracture surface verges, in brittle-tough transitions. A new laboratory method was used to isolate this region, and to test its ability to draw rapidly, in polyethylenes. The test uses a conventional Charpy type specimen that is deeply notched and impact loaded in three-point bending by a single striker. The ligament, rapidly loaded in almost pure tension, first yields, and then necks down until failure. Initial results are encouraging and correlate well with the in-service performance. A fundamental study of large strain deformation, that avoids the complexity associated with impact tests, was then conducted with the aim of isolating the dominating influences that furnish a polymer with the ability to sustain rapid large strain deformation. True stress vs. true strain curves have been interpreted using the one dimensional spring dashpot model of Haward and Thackray (H-T...

  10. Determination of dynamic fracture toughness using a new experimental technique

    Directory of Open Access Journals (Sweden)

    Cady Carl M.

    2015-01-01

    Full Text Available In other studies dynamic fracture toughness has been measured using Charpy impact and modified Hopkinson Bar techniques. In this paper results will be shown for the measurement of fracture toughness using a new test geometry. The crack propagation velocities range from ∼0.15 mm/s to 2.5 m/s. Digital image correlation (DIC will be the technique used to measure both the strain and the crack growth rates. The boundary of the crack is determined using the correlation coefficient generated during image analysis and with interframe timing the crack growth rate and crack opening can be determined. A comparison of static and dynamic loading experiments will be made for brittle polymeric materials. The analysis technique presented by Sammis et al. [1] is a semi-empirical solution, however, additional Linear Elastic Fracture Mechanics analysis of the strain fields generated as part of the DIC analysis allow for the more commonly used method resembling the crack tip opening displacement (CTOD experiment. It should be noted that this technique was developed because limited amounts of material were available and crack growth rates were to fast for a standard CTOD method.

  11. Improvement of impact toughness of 5Mn-1Al-0.5Ti steel by intercritical annealing

    Science.gov (United States)

    Yi, Il-Cheol; Ha, Yumi; Lee, Hakcheol; Zargaran, A.; Kim, Nack J.

    2017-03-01

    The present study is aimed at improving the impact toughness of 5Mn-1Al-0.5Ti steel by incorporating ferrite-martensite dual phase microstructure by intercritical annealing. Although (8-12)Mn martensitic steels usually show very low impact toughness due to the occurrence of intergranular fracture, the martensitic structure of the present 5Mn-1Al-0.5Ti steel fails by transgranular cleavage fracture due to higher grain boundary strength than matrix strength incurred by reduced Mn content and segregation of Ti along grain boundaries. Nevertheless, it still shows very poor impact toughness at room temperature due to its coarse grain size. The application of intercritical annealing, i.e., formation of dual phase microstructure, is shown to significantly decrease ductile-to-brittle transition temperature (DBTT), with only a small degradation of tensile properties; however, microstructural examinations show that most of ferrite/martensite interfaces have a character of low angle boundaries and therefore such decrease in DBTT is not necessarily due to the formation of ferrite-martensite dual phase structure, but rather to the refinement of grain size by low temperature annealing.

  12. The Assessment and Validation of Mini-Compact Tension Test Specimen Geometry and Progress in Establishing Technique for Fracture Toughness Master Curves for Reactor Pressure Vessel Steels

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, Mikhail A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Nanstad, Randy K. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-09-01

    Small specimens are playing the key role in evaluating properties of irradiated materials. The use of small specimens provides several advantages. Typically, only a small volume of material can be irradiated in a reactor at desirable conditions in terms of temperature, neutron flux, and neutron dose. A small volume of irradiated material may also allow for easier handling of specimens. Smaller specimens reduce the amount of radioactive material, minimizing personnel exposures and waste disposal. However, use of small specimens imposes a variety of challenges as well. These challenges are associated with proper accounting for size effects and transferability of small specimen data to the real structures of interest. Any fracture toughness specimen that can be made out of the broken halves of standard Charpy specimens may have exceptional utility for evaluation of reactor pressure vessels (RPVs) since it would allow one to determine and monitor directly actual fracture toughness instead of requiring indirect predictions using correlations established with impact data. The Charpy V-notch specimen is the most commonly used specimen geometry in surveillance programs. Assessment and validation of mini-CT specimen geometry has been performed on previously well characterized HSST Plate 13B, an A533B class 1 steel. It was shown that the fracture toughness transition temperature measured by these Mini-CT specimens is within the range of To values that were derived from various large fracture toughness specimens. Moreover, the scatter of the fracture toughness values measured by Mini-CT specimens perfectly follows the Weibull distribution function providing additional proof for validation of this geometry for the Master Curve evaluation of rector pressure vessel steels. Moreover, the International collaborative program has been developed to extend the assessment and validation efforts to irradiated weld metal. The program is underway and involves ORNL, CRIEPI, and EPRI.

  13. Study on the Toughness of X100 Pipeline Steel Heat Affected Zone

    Science.gov (United States)

    Li, Xueda; Shang, Chengjia; Ma, Xiaoping; Subramanian, S. V.

    Microstructure-property correlation of heat affected zone (HAZ) in X100 longitudinal submerged arc welding (LSAW) real weld joint was studied in this paper. Coarse grained (CG) HAZ and intercritically reheated coarse grained (ICCG) HAZ were characterized by optical microscope (OM), electron backscattered diffraction (EBSD). The microstructure of CGHAZ is mostly composed of granular bainite with low density of high angle boundaries (HAB). Prior austenite grain size is 80μm. In ICCGHAZ, coarse prior austenite grains were decorated by coarse necklacing martensite-austenite (M-A) constituents. Different layers were observed within M-A constituent, which may be martensite and austenite layers. Charpy absorbed energy of two different HAZ regions (ICCGHAZ containing and non-containing regions) was recorded using instrumental Charpy impact test machine. The results showed that the existence of ICCGHAZ resulted in the sharp drop of Charpy absorbed energy from 180J to 50J, while the existence of only CGHAZ could still lead to good toughness. The fracture surface was 60% brittle in the absence of ICCGHAZ, and 100% brittle in the presence of ICCGHAZ in the impact tested samples. The underlying reason is the microstructure of ICCGHAZ consisted of granular bainite and upper bainite with necklace-type M-A constituent along the grain boundaries. Cleavage fracture initiated from M-A constituent, either through cracking of M-A or debonding from the matrix, was observed at the fracture surface of ICCGHAZ. The presence of necklace type M-A constituent in ICCGHAZ notably increases the susceptibility of cleavage microcrack nucleation. Furthermore, the study of secondary microcracks beneath the CGHAZ and the ICCGHAZ through EBSD suggested that the fracture mechanism changes from nucleation-controlled in the CGHAZ to propagation-controlled in the ICCGHAZ because of the presence of necklace-type M-A constituent in the ICCGHAZ region. Both fracture mechanism contribute to the poor

  14. Mechanical Behavior and Fracture Toughness Evaluation of Multiphase Polymer Nanocomposites Using Impact and J-Integral via Locus Method

    Directory of Open Access Journals (Sweden)

    Bishnu P. Panda

    2013-01-01

    Full Text Available Fracture behaviors of fibrillar silicate clay (MMT filled thermoplastic polyolefin (TPO containing polypropylene (PP blended with ethylene-propylene-diene monomer (EPDM were systematically investigated using impact test method and J-integral by locus method. Drastic increase in impact strength is observed for all developed compositions and generally shows higher value for the selected phases containing dispersed nanoclay in PP matrix. A fracture mechanics approach has been adopted by mode I test, and the effects of specimen geometry have been investigated. Increase in interlaminar fracture energy value, Gc, and J-integral value, Jc, is marked as the crack propagated through the composite; that is, a rising “R-curve” is observed. Toughness measurements revealed that the fracture toughness increased with increasing clay content reaching maximum at 3 wt% of clay than pure PP. Moreover, enhancement of fracture toughness was more remarkable than that of stiffness. The fracture surfaces taken from different specimens were observed for exploring the fracture mechanisms using transmission electron microscopy (TEM revealed a strong particle-matrix adhesion.

  15. 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.

  16. Analysis of the master curve approach on the fracture toughness properties of SA508 Gr.4N Ni-Mo-Cr low alloy steels for reactor pressure vessels

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki-Hyoung, E-mail: shirimp@kaist.ac.kr [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)

    2010-06-15

    This study aims at assessing the fracture toughness behavior of tempered martensitic Ni-Mo-Cr low alloy steels for reactor pressure vessels in a transition temperature region using a master curve approach. The fracture toughness tests for model alloys with various chemical compositions were carried out following ASTM E1921-08. The microstructures, tensile properties, and Charpy impact toughness were also evaluated. Alloying elements such as Ni, Cr, and Mo affected the mechanical properties of alloys from changes in the phase fraction and precipitation behavior. In the fracture toughness test results, the data sets showed a deviation from the median curve and a smaller scatter than that of the prediction of the ASTM standard, especially in the lower transition region. The exponential parameter of the master curve equation was adjusted by an exponential fitting to data sets for expressing well the temperature dependency of the fracture toughness. The adjusted parameter provided good agreement for data distribution and the independence of T{sub 0} from test temperatures through an overall temperature range in contrast with the results from the standard master curve.

  17. Numerical modelling of Charpy-V notch test by local approach to fracture. Application to an A508 steel in the ductile-brittle transition range; Modelisation de l'essai Charpy par l'approche locale de la rupture. Application au cas de l'acier 16MND5 dans le domaine de transition

    Energy Technology Data Exchange (ETDEWEB)

    Tanguy, B

    2001-07-15

    Ferritic steels present a transition of the rupture mode which goes progressively of a brittle rupture (cleavage) to a ductile rupture when the temperature increases. The following of the difference of the transition temperature of the PWR vessel steel by the establishment of toughness curves makes of the Charpy test an integrating part of the monitoring of the French PWR reactors. In spite of the advantages which are adapted to it in particular its cost, the Charpy test does not allow to obtain directly a variable which characterizes a crack propagation resistance as for instance the toughness used for qualifying the mechanical integrity of a structure. This work deals with the establishment of the through impact strength-toughness in the transition range of the vessel steel: 16MND5 from a non-empirical approach based on the local approach of the rupture. The brittle rupture is described by the Beremin model (1983), which allows to describe the dispersion inherent in this rupture mode. The description of the brittle fissure is carried out by the GTN model (1984) and by the Rousselier model (1986). This last model has been modified in order to obtain a realistic description of the brittle damage in the case of fast solicitations and of local heating. The method proposed to determine the parameters of the damage models depends only of tests on notched specimens and of the inclusion data of the material. The behaviour is described by an original formulation parametrized in temperature which allows to describe all the tests carried out in this study. Before using this methodology, an experimental study of the behaviour and of the rupture modes of the steel 16MND5 has been carried out. From the toughness tests carried out in quasi-static and dynamical conditions, it has been revealed that this steel does not present important unwedging of its toughness curve due to the velocity effect. In the transition range, local heating of about 150 C have been measured in the root

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

    Energy Technology Data Exchange (ETDEWEB)

    Nanstad, R.K.; Iskander, S.K.; Sokolov, M.A. [Oak Ridge National Lab., TN (United States)] [and others

    1997-02-01

    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.

  19. Effects of Cryogenic Temperature on Fracture Toughness of Core-Shell Rubber (CSR) Toughened Epoxy Nanocomposites

    Science.gov (United States)

    Wang, J.; Cannon, S. A.; Magee, D.; Schneider, J. A.

    2008-01-01

    This study investigated the effects of core-shell rubber (CSR) nanoparticles on the mechanical properties and fracture toughness of an epoxy resin at ambient and liquid nitrogen (LN2) temperatures. Varying amounts of Kane Ace MX130 toughening agent were added to a commercially available EPON 862/Epikure W epoxy resin. Elastic modulus was calculated using quasi-static tensile data. Fracture toughness was evaluated by the resulting breaking energy measured in Charpy impact tests conducted on an instrumented drop tower. The size and distribution of the CSR nanoparticles were characterized using Transmission Electron Microscopy (TEM) and Small Angle X-ray Scattering (SAXS). Scanning Electron Microscopy (SEM) was used to study the fracture surface morphology. The addition of the CSR nanoparticles increased the breaking energy with negligible change in elastic modulus and ultimate tensile stress (UTS). At ambient temperature the breaking energy increased with increasing additions of the CSR nanoparticles, while at LN2 temperatures, it reached a maximum at 5 wt% CSR concentration. KEY WORDS: liquid nitrogen (LN2) properties, fracture toughness, core-shell rubber (CSR).

  20. Development of Mini-Compact Tension Test Method for Determining Fracture Toughness Master Curves for Reactor Pressure Vessel Steels

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, Mikhail A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-05-01

    Small specimens are playing the key role in evaluating properties of irradiated materials. The use of small specimens provides several advantages. Typically, only a small volume of material can be irradiated in a reactor at desirable conditions in terms of temperature, neutron flux, and neutron dose. A small volume of irradiated material may also allow for easier handling of specimens. Smaller specimens reduce the amount of radioactive material, minimizing personnel exposures and waste disposal. However, use of small specimens imposes a variety of challenges as well. These challenges are associated with proper accounting for size effects and transferability of small specimen data to the real structures of interest. Any fracture toughness specimen that can be made out of the broken halves of standard Charpy specimens may have exceptional utility for evaluation of reactor pressure vessels (RPVs) since it would allow one to determine and monitor directly actual fracture toughness instead of requiring indirect predictions using correlations established with impact data. The Charpy V-notch specimen is the most commonly used specimen geometry in surveillance programs. Validation of the mini compact tension specimen (mini-CT) geometry has been performed on previously well characterized Midland beltline Linde 80 (WF-70) weld in the unirradiated condition. It was shown that the fracture toughness transition temperature, To, measured by these Mini-CT specimens is almost the same as To value that was derived from various larger fracture toughness specimens. Moreover, an International collaborative program has been established to extend the assessment and validation efforts to irradiated Linde 80 weld metal. The program is underway and involves the Oak Ridge National Laboratory (ORNL), Central Research Institute for Electrical Power Industry (CRIEPI), and Electric Power Research Institute (EPRI). The irradiated Mini-CT specimens from broken halves of previously tested Charpy

  1. On the Effectiveness of the Dynamic Force Adjustment for Reducing the Scatter of Instrumented Charpy Results

    Energy Technology Data Exchange (ETDEWEB)

    Lucon, E.

    2008-09-15

    One of the key factors for obtaining reliable instrumented Charpy results is the calibration of the instrumented striker. An interesting alternative to the conventional static calibration recommended by the standards is the Dynamic Force Adjustment (DFA), in which forces and displacements are iteratively adjusted until equality is achieved between absorbed energies calculated under the test record (Wt) and measured by the machine encoder (KV). In this study, this procedure has been applied to the instrumented data obtained by 10 international laboratories using notched and precracked Charpy specimens, in the framework of a Coordinated Research Project (CRP8) of IAEA. DFA is extremely effective in reducing the between-laboratory scatter for both general yield and maximum forces. The effect is less significant for dynamic reference temperatures measured from precracked Charpy specimens using the Master Curve procedure, but a moderate reduction of the standard deviation is anyway observed. It is shown that striker calibration is a prominent contribution to the interlaboratory variability of instrumented impact forces, particularly in the case of maximum forces.

  2. Correlations between Standard and Miniaturised Charpy-V Specimens

    Energy Technology Data Exchange (ETDEWEB)

    Lucon, E.; Van Walle, E.; Fabry, A.; Puzzolante, J.-L.; Verstrepen, A.; Vosch, R.; Van de Velde, L

    1998-12-01

    A total of 565 instrumented impact tests (232 performed on full-size and 333 on sub-size Charpy-V specimens) have been analysed in order to derive meaningful assumptions on the correlations existing between test results obtained on specimens of different size. Nine materials (pressure vessel steels) have been considered, in both as-received and irradiated state, for a total of 19 conditions examined. For the analysis of data, conventional as well novel approaches have been investigated; former ones, based on a review of the existing literature, include predictions of USE values by the use of normalization factors (NF), shifts of index temperatures related to energy/lateral expansion/shear fracture levels, and a combination of both approaches (scaling and shifting of energy curves). More original and recent proposals have also been verified, available in the literature but also proposed by SCK-CEN in the frame of enhanced surveillance of nuclear reactor pressure vessels. Conclusions have been drawn regarding the applicability and reliability of these methodologies, and recommendations have been given for future developments of the activities on this topic.

  3. Correction of constraint loss in fracture toughness measurement of PCVN specimens based on fracture toughness diagram

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Shin Beom; Kim, Young Jin [Sungkyunkwan University, Suwon (Korea, Republic of); Chang, Yoon-Suk [Kyung Hee University, Yongin (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Reserch Institute, Daejeon (Korea, Republic of)

    2010-03-15

    The aim of this paper is to suggest an approach to generate master curves by using miniature specimens, especially pre-cracked Charpy V-notched (PCVN) specimen, made of SA508 carbon steel. Firstly, fracture toughness diagram is derived from comparing finite element analyses results with the fixed mesh size at crack tip between standard compact tension and PCVN specimens. To compensate the constraint effects from different geometry, further examination based on the fracture toughness diagram was performed. In this context, a scale factor to deal with specimen size effects is proposed by statistically manipulating the numerical analysis data. Finally, the proposed scale factor is applied to calculate reference temperature which affects on the master curve. We expect that the approach can be applicable to compensate the geometrical constraint effects on fracture toughness of SA508 carbon steel when the PCVN specimen is used

  4. 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.

  5. Temperature dependence of fracture toughness in HT9 steel neutron-irradiated up to 145 dpa

    Energy Technology Data Exchange (ETDEWEB)

    Baek, Jong-Hyuk [KAERI; Byun, Thak Sang [ORNL; Maloy, S [Los Alamos National Laboratory (LANL); Toloczko, M [Pacific Northwest National Laboratory (PNNL)

    2014-01-01

    The temperature dependence of fracture toughness in HT9 steel irradiated to high doses was investigated using miniature three-point bend (TPB) fracture specimens. These specimens were from the ACO-3 fuel duct wall of the Fast Flux Test Facility (FFTF), in which irradiation doses were in the range of 3.2 144.8 dpa and irradiation temperatures in the range of 380.4 502.6 oC. A miniature specimen reuse technique has been established for this investigation: the specimens used were the tested halves of miniature Charpy impact specimens (~13 3 4 mm) with diamond-saw cut in the middle. The fatigue precracking for specimens and fracture resistance (J-R) tests were carried out in a MTS servo-hydraulic testing machine with a vacuum furnace following the standard procedure described in the ASTM Standard E 1820-09. For each of five irradiated and one archive conditions, 7 to 9 J-R tests were performed at selected temperatures ranging from 22 C to 600 C. The fracture toughness of the irradiated HT9 steel was strongly dependent on irradiation temperatures rather than irradiation dose. When the irradiation temperature was below about 430 C, the fracture toughness of irradiated HT9 increased with test temperature, reached an upper shelf of 180 200 MPa m at 350 450 C and then decreased with test temperature. When the irradiation temperature 430 C, the fracture toughness was nearly unchanged until about 450 C and decreased with test temperature in higher temperature range. Similar test temperature dependence was observed for the archive material although the highest toughness values are lower after irradiation. Ductile stable crack growth occurred except for a few cases where both the irradiation temperature and test temperature are relatively low.

  6. 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.

  7. Mental Toughness

    Science.gov (United States)

    Quinn, Tori; Cavanaugh, Lauren

    2017-01-01

    Mental toughness (MT) is defined as a set of attributes that allow an individual to persevere through difficult circumstances that ultimately can lead to successful outcomes. It is also a critical component of maximizing the performance of an athlete. These attributes assist with and promote a state of mind that enhances performance. A negative…

  8. Short review: Potential impact of delamination cracks on fracture toughness of structural materials

    Directory of Open Access Journals (Sweden)

    X.C. Arnoult

    2016-02-01

    Full Text Available The current energy policy envisages extended lifetime for the current nuclear power plants (GEN II NPP. This policy imposes a large research effort to understand the ageing of power plant components. In this goal, it is necessary to improve knowledge about safety, reliability and components’ integrity for more than forty years of operation. In Central and Eastern Europe, the majority of NPPs are VVER types, where some of the components are produced from austenitic steel 08Ch18N10T. Irradiated 08Ch18N10T may exhibit brittle behavior, namely delamination cracks are found in some cases on the fracture surface of irradiated 08Ch18N10T with elongated δ-ferrite. Delamination cracks have also been observed on the fracture surface of high-strength steels or aluminum-lithium alloys. This article presents a state-of-the art review to provide a detailed analysis of the influence of delamination cracks on the toughness of metal alloys. In general, the delamination cracks are present in metal alloys having a high texture and microstructure anisotropy. Three types of delamination cracks have been observed and are classified as crack arrester delamination, crack divider delamination and crack splitting delamination. The microscopy characterization, 3D fracture theories and computational studies explaining possible causes and effects of delamination cracks on the mechanical properties of metal alloys are presented.

  9. Tough Love in Tough Times

    Directory of Open Access Journals (Sweden)

    Tracey Jensen

    2012-07-01

    Full Text Available This paper examines the cultural politics of 'thrift' and 'tough love'. It reflects upon the significance of notions of 'good parenting' in policy and popular debates around social mobility and aspiration. In particular, it reviews the profound importance of notions of 'poor parenting' in the culturalisation of poverty, whereby poverty is seen to be a symptom of 'poor' conduct and behaviour, rather than of deeply entrenched systemic inequalities. This paper considers how the recent 'austerity' agenda has been taken up as a cultural annotation in the politicisation of parenting, (reproducing nostalgic fantasies of post-war spirit, national resilience and individual family responsibility. This article attends to how discourses of thrift and tough love are stitched together in the current cultural climate of austerity, and tracks these fantasies across a range of policy, media and cultural sites. It argues that these discourses locate the causes of the current financial crisis in spendthrift habits, consumer incompetence, over-consumption and wastefulness. It argues that thrift fantasies generate and circulate powerful cultural figurations of happy gendered restraint, such as the 'happy housewife', which serve as ideological signs of an imagined capacity for families to thrive through times of hardship. This paper maps the emerging affective incitements around austerity, gender, family and the future, in order to question the romances of austerity, and specifically of austerity parenting, and explore how austerity is being incorporated into cruelly optimistic visions of the future, which both deny existing social inequality and promise future happiness through the embrace of thrift.

  10. Assessment of Ductile-to-Brittle Transition Behavior of Localized Microstructural Regions in a Friction-Stir Welded X80 Pipeline Steel with Miniaturized Charpy V-Notch Testing

    Science.gov (United States)

    Avila, Julian A.; Lucon, Enrico; Sowards, Jeffrey; Mei, Paulo Roberto; Ramirez, Antonio J.

    2016-06-01

    Friction-stir welding (FSW) is an alternative welding process for pipelines. This technology offers sound welds, good repeatability, and excellent mechanical properties. However, it is of paramount importance to determine the toughness of the welds at low temperatures in order to establish the limits of this technology. Ductile-to-brittle transition curves were generated in the present study by using a small-scale instrumented Charpy machine and miniaturized V-notch specimens (Kleinstprobe, KLST); notches were located in base metal, heat-affected, stirred, and hard zones within a FSW joint of API-5L X80 Pipeline Steel. Specimens were tested at temperatures between 77 K (-196 °C) and 298 K (25 °C). Based on the results obtained, the transition temperatures for the base material and heat-affected zone were below 173 K (-100 °C); conversely, for the stirred and hard zones, it was located around 213 K (-60 °C). Fracture surfaces were characterized and showed a ductile fracture mechanism at high impact energies and a mixture of ductile and brittle mechanisms at low impact energies.

  11. Effect of Reheating Temperature and Cooling Treatment on the Microstructure, Texture, and Impact Transition Behavior of Heat-Treated Naval Grade HSLA Steel

    Science.gov (United States)

    Sk, Md. Basiruddin; Ghosh, A.; Rarhi, N.; Balamuralikrishnan, R.; Chakrabarti, D.

    2017-07-01

    In order to achieve the desired mechanical properties [YS > 390 MPa, total elongation >16 pct and Charpy impact toughness of 78 J at 213 K (-60 °C)] for naval application, samples from a low-carbon microalloyed steel have been subjected to different austenitization (1223 K to 1523 K) (950 °C to 1250 °C) and cooling treatments (furnace, air, or water cooling). The as-rolled steel and the sample air cooled from 1223 K (950 °C) could only achieve the required tensile properties, while the sample furnace cooled from 1223 K (950 °C) showed the best Charpy impact properties. Water quenching from 1223 K (950 °C) certainly contributed to the strength but affected the impact toughness. Overall, predominantly ferrite matrix with fine effective grain size and intense gamma-fiber texture was found to be beneficial for impact toughness as well as impact transition behavior. Small size and fraction of precipitates (like TiN, Nb, and V carbonitrides) eliminated the possibility of particle-controlled crack propagation and grain size-controlled crack propagation led to cleavage fracture. A simplified analytical approach has been used to explain the difference in impact transition behavior of the investigated samples.

  12. Continuous cooling transformation behavior and impact toughness in heat-affected zone of Nb-containing fire-resistant steel

    Science.gov (United States)

    Wang, Hong Hong; Qin, Zhan Peng; Wan, Xiang Liang; Wei, Ran; Wu, Kai Ming; Misra, Devesh

    2017-09-01

    Simulated heat-affected zone continuous cooling transformation diagram was developed for advanced fireresistant steel. Over a wide range of cooling rates, corresponding to t8/5 from 6 s to 150 s, granular bainite was the dominant transformation constituent, while the morphology of less dominant martensite-austenite (M-A) constituent changed from film-like to block-type constituent; but the hardness remained similar to the average value of 190-205 HV (0.2). The start and finish transformation temperature was high at 700 °C and 500 °C, and is different from the conventional high strength low alloy steels. It is believed that the high-content (0.09 wt%) of Nb may promote bainite transformation at relatively high temperatures. Martenistic matrix was not observed at high cooling rate and the film-like M-A constituent and blocky M-A constituent with thin film of retained austenite and lath martensite were observed on slow cooling. Excellent impact toughness was obtained in the heat-affected zone with 15-75 kJ/cm welding heat input.

  13. Effect of Heat Treatment on Low Temperature Toughness of Reduced Pressure Electron Beam Weld Metal of Type 316L Stainless Steel

    Science.gov (United States)

    Nakagawa, H.; Fujii, H.; Tamura, M.

    2006-03-01

    Austenitic stainless steels are considered to be the candidate materials for liquid hydrogen vessels and the related equipments, and those welding parts that require high toughness at cryogenic temperature. The authors have found that the weld metal of Type 316L stainless steel processed by reduced pressure electron beam (RPEB) welding has high toughness at cryogenic temperature, which is considered to be due to the single-pass welding process without reheating effect accompanied by multi-pass welding process. In this work, the effect of heat treatment on low temperature toughness of the RPEB weld metal of Type 316L was investigated by Charpy impact test at 77K. The absorbed energy decreased with higher temperature and longer holding time of heat treatment. The remarkable drop in the absorbed energy was found with heat treatment at 1073K for 2 hours, which is as low as that of conventional multi-pass weld metal such as tungsten inert gas welding. The observations of fracture surface and microstructure revealed that the decrease in the absorbed energy with heat treatment resulted from the precipitation of intermetallic compounds near delta-ferrite phase.

  14. Effects of Core-Shell Rubber (CSR) Nanoparticles on the Cryogenic Fracture Toughness of CSR Modified Epoxy

    Science.gov (United States)

    Wang, Jun; Magee, Daniel; Schneider, Judy; Cannon, Seth

    2009-01-01

    This study investigated the effects of core-shell rubber (CSR) nanoparticles on the mechanical properties and fracture toughness of an epoxy resin at ambient and liquid nitrogen (LN2) temperatures. Varying amounts of Kane Ace(Registered TradeMark) MX130 and Kane Ace(Registered TradeMark) MX960 toughening agent were added to a commercially available EPON 862/Epikure W epoxy resin. Elastic modulus was calculated using quasi-static tensile data. Fracture toughness was evaluated by the resulting breaking energy measured in Charpy impact tests conducted on an instrumented drop tower. The size and distribution of the CSR nanoparticles were characterized using Transmission Electron Microscopy (TEM) and Small Angle X-ray Scattering (SAXS). Scanning Electron Microscopy (SEM) was used to study the fracture surface morphology. The addition of the CSR nanoparticles increased the breaking energy with negligible change in elastic modulus and ultimate tensile stress (UTS). At ambient temperature the breaking energy increased with increasing additions of the CSR nanoparticles up to 13.8wt%, while at LN2 temperatures, it reached a plateau at much lower CSR concentration.

  15. Effect of composition and processing on the thermal fatigue and toughness of high performance die steels. Year 1 report

    Energy Technology Data Exchange (ETDEWEB)

    Wallace, J.F.; Wang, Yumin; Schwam, D.

    1996-06-01

    The goal of this project is to extend the lifetime of dies for die casting by 20%. Since the die contributes about 10% to the cost of die cast parts, such an improvement in lifetime would result in annual savings of over $200 Million dollars. This is based on the estimated annual die production of one Billion dollars in the US. The major tasks of this two year project are: (1) Evaluate NEW DIE STEEL COMPOSITIONS that have been developed for demanding applications and compare them to Premium Grade H-13 die steel. (2) Optimize the AUSTENITIZING TREATMENT of the new composition. Assess the effects of fast, medium and slow COOLING RATES DURING HEAT TREATMENT, on the thermal fatigue resistance and toughness of the die steel. (3) Determine the effect of ELECTRO-DISCHARGE MACHINING (EDM) on the thermal fatigue resistance and impact properties of the steel. (4) Select demanding components and conduct IN-PLANT TESTING by using the new steel. Compare the performance of the new steel with identical components made of Premium Grade H-13. The immersion thermal fatigue specimen developed at CWRU is being used to determine resistance to heat checking, and the Charpy V-notch test for evaluating the toughness. The overall result of this project will be identification of the best steel available on the market and the best processing methods for aluminum die casting dies. This is an interim report for year 1 of the project.

  16. 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.

  17. Evaluating Strengthening and Impact Toughness Mechanisms for Ferritic and Bainitic Microstructures in Nb, Nb-Mo and Ti-Mo Microalloyed Steels

    Directory of Open Access Journals (Sweden)

    Gorka Larzabal

    2017-02-01

    Full Text Available Low carbon microalloyed steels show interesting commercial possibilities by combining different “micro”-alloying elements when high strength and low temperature toughness properties are required. Depending on the elements chosen for the chemistry design, the mechanisms controlling the strengths and toughness may differ. In this paper, a detailed characterization of the microstructural features of three different microalloyed steels, Nb, Nb-Mo and Ti-Mo, is described using mainly the electron backscattered diffraction technique (EBSD as well as transmission electron microscopy (TEM. The contribution of different strengthening mechanisms to yield strength and impact toughness is evaluated, and its relative weight is computed for different coiling temperatures. Grain refinement is shown to be the most effective mechanism for controlling both mechanical properties. As yield strength increases, the relative contribution of precipitation strengthening increases, and this factor is especially important in the Ti-Mo microalloyed steel where different combinations of interphase and random precipitation are detected depending on the coiling temperature. In addition to average grain size values, microstructural heterogeneity is considered in order to propose a new equation for predicting ductile–brittle transition temperature (DBTT. This equation considers the wide range of microstructures analyzed as well as the increase in the transition temperature related to precipitation strengthening.

  18. Experimental Investigation of Charpy Impact Tests on Metallic SLM parts

    OpenAIRE

    Yasa, Evren; Deckers, Jan; Kruth, Jean-Pierre; Rombouts, Marleen; Luyten, Jan

    2009-01-01

    Selective laser melting (SLM) is a layer-additive manufacturing technology making it possible to create fully functional parts directly from standard metal powders without using any intermediate binders or any additional post-processing steps. During the process, a laser source selectively scans a powder bed according to the CAD data of the part to be produced and powder particles are completely molten by a high intensity laser beam. SLM is capable of producing near full density metallic part...

  19. Fractographic examination of reduced activation ferritic/martensitic steel charpy specimens irradiated to 30 dpa at 370{degrees}C

    Energy Technology Data Exchange (ETDEWEB)

    Gelles, D.S.; Hamilton, M.L. [Pacific Northwest National Lab., Richland, WA (United States); Schubert, L.E. [Univ. of Missouri, Rolla, MO (United States)

    1996-10-01

    Fractographic examinations are reported for a series of reduced activation ferritic/Martensitic steel Charpy impact specimens tested following irradiation to 30 dpa at 370{degrees}C in FFTF. One-third size specimens of six low activation steels developed for potential application as structural materials in fusion reactors were examined. A shift in brittle fracture appearance from cleavage to grain boundary failure was noted with increasing manganese content. The results are interpreted in light of transmutation induced composition changes in a fusion environment.

  20. Mental toughness in soccer

    DEFF Research Database (Denmark)

    Diment, Gregory Michael

    2014-01-01

    In the past decade mental toughness has been discussed as a significant factor in performance in elite sport. Few studies have explored mental toughness from a behavioral perspective, and no comprehensive lists of mental toughness behaviors have been developed. The aim of the study was to produce...... 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...

  1. Statistical analyses of fracture toughness results for two irradiated high-copper welds

    Energy Technology Data Exchange (ETDEWEB)

    Nanstad, R.K.; McCabe, D.E.; Haggag, F.M.; Bowman, K.O.; Downing, D.J.

    1990-01-01

    The objectives of the Heavy-Section Steel Irradiation Program Fifth Irradiation Series were to determine the effects of neutron irradiation on the transition temperature shift and the shape of the K{sub Ic} curve described in Sect. 6 of the ASME Boiler and Pressure Vessel Code. Two submerged-arc welds with copper contents of 0.23 and 0.31% were commercially fabricated in 215-mm-thick plates. Charpy V-notch (CVN) impact, tensile, drop-weight, and compact specimens up to 203.2 mm thick (1T, 2T, 4T, 6T, and 8T C(T)) were tested to provide a large data base for unirradiated material. Similar specimens with compacts up to 4T were irradiated at about 288{degrees}C to a mean fluence of about 1.5 {times} 10{sup 19} neutrons/cm{sup 2} (>1 MeV) in the Oak Ridge Research Reactor. Both linear-elastic and elastic-plastic fracture mechanics methods were used to analyze all cleavage fracture results and local cleavage instabilities (pop-ins). Evaluation of the results showed that the cleavage fracture toughness values determined at initial pop-ins fall within the same scatter band as the values from failed specimens; thus, they were included in the data base for analysis (all data are designated K{sub Jc}).

  2. Standard Guide for Reconstitution of Irradiated Charpy-Sized Specimens

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2007-01-01

    1.1 This guide covers procedures for the reconstitution of ferritic pressure boundary steels used in nuclear power plant applications, Type A Charpy (Test Methods E 23) specimens and specimens suitable for testing in three point bending in accordance with Test Methods E 1921 or E 1820. Materials from irradiation programs (principally broken specimens) are reconstituted by welding end tabs of similar material onto remachined specimen sections that were unaffected by the initial test. Guidelines are given for the selection of suitable specimen halves and end tab materials, for dimensional control, and for avoidance of overheating the notch area. A comprehensive overview of the reconstitution methodologies can be found in Ref (1). 1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard...

  3. Volume Fraction Effect of V8C7 Particulates on Impact Toughness and Wear Performance of V8C7/Fe Monolithic Composites

    Science.gov (United States)

    Ye, Fangxia; Hojamberdiev, Mirabbos; Xu, Yunhua; Zhong, Lisheng; Yan, Honghua; Chen, Zhe

    2014-04-01

    The V8C7 particulates-reinforced iron-based metal matrix composite with 8-33 vol.% V8C7 was produced by infiltration casting process with subsequent heat treatment at 1164 °C for 3 h. With increasing the volume fraction of V8C7 in the composite, microhardness of the composite increases, while its impact toughness decreases. Relative wear resistance of the composite with different volume fractions of V8C7 was also investigated in this study. The composite with 24 vol.% V8C7 shows the highest relative wear resistance, which is much higher than that of gray cast iron. Microcracking, microploughing, and the fragmentation of particulates are found to be the dominant wear mechanisms.

  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. Visual interface for the automation of the instrumented pendulum of Charpy tests used in the surveillance program of reactors vessel of nuclear power plants; Interfase visual para la automatizacion del pendulo instrumentado de pruebas Charpy utilizado en el programa de vigilancia de la vasija de reactores de centrales nucleares

    Energy Technology Data Exchange (ETDEWEB)

    Rojas S, A.S.; Sainz M, E.; Ruiz E, J.A. [ININ, Carretera Mexico-Toluca Km.36.5, Mpio. de Ocoyoacac, Estado de Mexico (Mexico)]. E-mail: asrs@nuclear.inin.mx; esm@nuclear.inin.mx; jare@nuclear.inin.mx

    2004-07-01

    Inside the Programs of Surveillance of the nuclear power stations periodic information is required on the state that keep the materials with those that builds the vessel of the reactor. This information is obtained through some samples or test tubes that are introduced inside the core of the reactor and it is observed if its physical characteristics remain after having been subjected to the radiation changes and temperature. The rehearsal with the instrumented Charpy pendulum offers information on the behavior of fracture dynamics of a material. In the National Institute of Nuclear Research (ININ) it has an instrumented Charpy pendulum. The operation of this instrument is manual, having inconveniences to carry out rehearsals with radioactive material, handling of high and low temperatures, to fulfill the normative ones for the realization of the rehearsals, etc. In this work the development of a computational program is presented (virtual instrument), for the automation of the instrumented pendulum. The system has modules like: Card of data acquisition, signal processing, positioning system, tempered system, pneumatic system, compute programs like it is the visual interface for the operation of the instrumented Charpy pendulum and the acquisition of impact signals. This system shows that given the characteristics of the nuclear industry with radioactive environments, the virtual instrumentation and the automation of processes can contribute to diminish the risks to the personnel occupationally exposed. (Author)

  6. Influence of crystallographic texture in X70 pipeline steels on toughness anisotropy and delamination

    Science.gov (United States)

    Al-Jabr, Haytham M.

    The effects of microstructure and crystallographic texture in four commercially-produced API X70 pipeline steels and their relation to planar anisotropy of toughness and delamination were evaluated. The experimental steels were processed through either a hot strip mill, a Steckel mill, or a compact strip mill. Different processing routes were selected to obtain plates with potential variations in the microstructure and anisotropic characteristics. Tensile and Charpy impact testing were used to evaluate the mechanical properties in three orientations: longitudinal (L), transverse (T) and diagonal (D) with respect to the rolling direction to evaluate mechanical property anisotropy. The yield and tensile strengths were higher in the T orientation and toughness was lower in the D orientation for all plates. Delamination was observed in some of the ductile fracture surfaces of the impact samples. To further study the splitting behavior and effects on impact toughness, a modified impact test (MCVN) specimen with side grooves was designed to intensify induced stresses parallel to the notch root and thus facilitate evaluation of delamination. Scanning electron microscopy combined with electron backscattered diffraction (EBSD) were used to evaluate the grain size, microstructural constituents, and crystallographic texture to determine the factors leading to delamination and the anisotropy in toughness. The ferrite grain size is mainly responsible for the differences in DBTTs between the L and T orientations. The higher DBTT in the D orientation observed in pipeline steels is attributed to crystallographic texture. The higher DBTT in the D direction is due to the higher volume fraction of grains having their {100} planes parallel or close to the primary fracture plane for the D orientation. An equation based on a new "brittleness parameter," based on an assessment of grain orientations based on EBSD data, was developed to predict the changes in DBTTs with respect to sample

  7. Extension of TOUGH-FLAC to the finite strain framework

    Science.gov (United States)

    Blanco-Martín, Laura; Rutqvist, Jonny; Birkholzer, Jens T.

    2017-11-01

    The TOUGH-FLAC simulator for coupled thermal-hydraulic-mechanical processes modeling has been extended to the finite strain framework. In the approach selected, this extension has required modifications to the flow simulator (TOUGH2) and to the coupling scheme between the geomechanics and the flow sub-problems. In TOUGH2, the mass and energy balance equations have been extended to account for volume changes. Additionally, as large deformations are computed by FLAC3D, the geometry is updated in the flow sub-problem. The Voronoi partition needed in TOUGH2 is computed using an external open source library (Voro++) that uses the centroids of the deformed geomechanics mesh as generators of the Voronoi diagram. TOUGH-FLAC in infinitesimal and finite strain frameworks is verified against analytical solutions and other approaches to couple flow and geomechanics. Within the finite strain framework, TOUGH-FLAC is also successfully applied to a large-scale case. The extension of TOUGH-FLAC to the finite strain framework has little impact to the user as only one additional executable is needed (for Voro++), and the input files and the workflow of a simulation are the same as in standard TOUGH-FLAC. With this new provision for finite strains, TOUGH-FLAC can be used in the analysis of a wider range of engineering problems, and the areas of application of this simulator are therefore broadened.

  8. Master curve characterization of the fracture toughness behavior in SA508 Gr.4N low alloy steels

    Science.gov (United States)

    Lee, Ki-Hyoung; Kim, Min-Chul; Lee, Bong-Sang; Wee, Dang-Moon

    2010-08-01

    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 T0 determination for the tempered martensitic SA508 Gr.4N steels.

  9. 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.

  10. SISTEMA DE AQUISIÇÃO DE DADOS PARA A MÁQUINA DE IMPACTO CHARPY

    Directory of Open Access Journals (Sweden)

    Jermana Lopes Moraes

    2014-08-01

    Full Text Available Este trabalho tem o objetivo de implementar e desenvolver um sistema de aquisição de dados para a máquina de impacto Charpy. Assim, é realizado um estudo da máquina de impacto Charpy, do ensaio de impacto e das ferramentas necessárias para desenvolvimento do projeto. Utiliza-se um acelerômetro para determinar a aceleração nos eixos x e y do pêndulo Charpy durante a realização do ensaio. Para leitura e interpretação dos dados enviados pelo acelerômetro utiliza-se a plataforma de hardware Arduino UNO com software específico. Os dados enviados ao Arduino são apresentados em uma interface gráfica desenvolvida no Matlab. Nesta interface é possível inserir os dados iniciais de ensaio Charpy e apresentar ao usuário final os resultados finais de ensaio, como a energia de impacto, a resistência de impacto e a força necessária para romper o corpo de prova. Além disso, é apresentado ao usuário um gráfico da aceleração ao longo da realização do ensaio e o gráfico de força ao longo do tempo. Desta forma, registram-se os dados em um arquivo específico para análise e estudo posterior. A porcentagem de erro entre o valor medidor no mostrador da máquina e o resultado automatizado não ultrapassa o limite de 8 %.

  11. Tailor-Made Dispersion and Distribution of Stereocomplex Crystallites in Poly(l-lactide)/Elastomer Blends toward Largely Enhanced Crystallization Rate and Impact Toughness.

    Science.gov (United States)

    Luo, Yuanlin; Ju, Yilong; Bai, Hongwei; Liu, Zhenwei; Zhang, Qin; Fu, Qiang

    2017-06-29

    Stereocomplex (SC) crystallites, formed between poly(l-lactide) (PLLA) and poly(d-lactide), exhibit great potential to substantially enhance crystallization rate of PLLA-based materials as an eco-friendly nucleating agent. However, the nucleation efficiency of the SC crystallites is still far below an expected level, mostly on account of their strong aggregation tendency in PLLA/PDLA melts. Herein, taking PLLA/poly(ethylene-methyl acrylate-glycidyl methacrylate) (E-MA-GMA) blends as an example, we report a unique and facile strategy to control the dispersion and distribution of SC crystallites within the PLLA matrix by using elastomeric E-MA-GMA as carrier for the incorporation of PDLA. To do this, PDLA was first blended with E-MA-GMA or chemically grafted onto the E-MA-GMA. During subsequent melt-blending of PLLA and the E-MA-GMA/PDLA master batch, the PDLA chain clusters predispersed in the E-MA-GMA phase can gradually migrate into PLLA matrix and then collaborate with the matrix chains to form large amounts of tiny and well-dispersed SC crystallites. Compared with the SC-crystallite agglomerates formed by the direct melt-blending of PLLA and PDLA components, such tiny SC crystallites are much more effective in accelerating PLLA matrix crystallization. More interestingly, when PDLA chains are grafted onto the EMA-GMA, the formed SC crystallites tend to preferentially distribute at the blend interface and thus induce not only optimal nucleation efficiency but also superior impact toughness because these interface-localized SC crystallites can also serve as bridges to enhance interface adhesion. This work could open a new avenue in designing heat-resistant and supertough PLLA blends via controllable construction of SC crystallites.

  12. Required grades of hull steel plates in consideration of fracture toughness; Hakai jinsei wo koryoshita sentaiyo koban shiyo kubun ni kansuru ichikosatsu

    Energy Technology Data Exchange (ETDEWEB)

    Yajima, H.; Yamamoto, M.; Ogaki, Y. [Hiroshima University, Hiroshima (Japan). Faculty of Engineering

    1997-10-01

    This paper discusses the required grades of hull steel plates based on the steel ship rule of Nippon Kaiji Kyokai (NK). The minimum value of the allowable crack length in NK rule (critical safety crack length at 0degC just before brittle unstable crack causing fatal fracture) was estimated. In the case where the estimated crack tip exists in a matrix, the crack length was a minimum of 200-210mm, while nearly 60mm in a fusion line at high-heat-input welded joint. The allowable crack lengths estimated from a specified value in the NK rule were fairly different. The allowable crack length at 0degC was also estimated from the minimum value in V-notch Charpy impact test. The private proposal on the required grades of hull steel plates in consideration of fracture toughness was discussed. Thirty-five percent of crack lengths found in real ships is 100mm or less, however, cracks of 250-400mm long are frequently found suggesting the allowable crack length of 400mm. The required grade integrally considering required values and design conditions is demanded to secure the reliability of hull strength. 5 refs., 5 figs., 2 tabs.

  13. Effect of Boron on the Strength and Toughness of Direct-Quenched Low-Carbon Niobium Bearing Ultra-High-Strength Martensitic Steel

    Science.gov (United States)

    Hannula, Jaakko; Kömi, Jukka; Porter, David A.; Somani, Mahesh C.; Kaijalainen, Antti; Suikkanen, Pasi; Yang, Jer-Ren; Tsai, Shao-Pu

    2017-11-01

    The effect of boron on the microstructures and mechanical properties of laboratory-control-rolled and direct-quenched 6-mm-thick steels containing 0.08 wt pct C and 0.02 wt pct Nb were studied. The boron contents were 24 ppm and a residual amount of 4 ppm. Two different finish rolling temperatures (FRTs) of 1093 K and 1193 K (820 °C and 920 °C) were used in the hot rolling trials to obtain different levels of pancaked austenite prior to DQ. Continuous cooling transformation (CCT) diagrams were constructed to reveal the effect of boron on the transformation behavior of these steels. Microstructural characterization was carried out using various microscopy techniques, such as light optical microscopy (LOM) and scanning electron microscopy-electron backscatter diffraction (SEM-EBSD). The resultant microstructures after hot rolling were mixtures of autotempered martensite and lower bainite (LB), having yield strengths in the range 918 to 1067 MPa with total elongations to fracture higher than 10 pct. The lower FRT of 1093 K (820 °C) produced better combinations of strength and toughness as a consequence of a higher degree of pancaking in the austenite. Removal of boron lowered the 34 J/cm2 Charpy-V impact toughness transition temperature from 206 K to 158 K (-67 °C to -115 °C) when the finishing rolling temperature of 1093 K (820 °C) was used without any loss in the strength values compared to the boron-bearing steel. This was due to the finer and more uniform grain structure in the boron-free steel. Contrary to expectations, the difference was not caused by the formation of borocarbide precipitates, as verified by transmission electron microscopy (TEM) investigations, but through the grain coarsening effect of boron.

  14. 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.

  15. Inverse of Wallin's relation for the effect of strain rate on the ASTM E-1921 reference temperature and its application to reference temperature estimation from Charpy tests

    Energy Technology Data Exchange (ETDEWEB)

    Sreenivasan, P.R., E-mail: sreeprs@yahoo.co.i [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)

    2011-01-15

    Research highlights: An inverse relation for the Wallin strain rate equation (WSRE), that is, IWSRE, has been derived for predicting the static reference temperature from dynamic results. Using the IWSRE and some other correlations, a procedure, called IGCAR-procedure, has been developed for conservative estimation of the ASTM E-1921 reference temperature, T{sub 0-est}, from Charpy V-notch ductile-brittle transition tests alone. The T{sub 0-est} by the IGCAR-procedure is termed T{sub q-IGC} to distinguish it from other estimates. {yields}T{sub q-IGC} is neither too conservative nor unacceptably non-conservative. The T{sub q-IGC} along with the conservative Master Curve procedure helps provide assuredly conservative lower-bound fracture toughness curve. - Abstract: An inverse relation to that of Wallin's strain rate equation has been obtained for predicting the static reference temperature from dynamic results. Wallin strain rate equation (WSRE) predicts the reference temperature at faster loading rates (expressed as stress intensity factor - SIF-rates) from room temperature yield strength (RT-YS) and quasi-static reference temperature, T{sub 0}. The inverse WSRE (IWSRE) predicts T{sub 0} from T{sub 0}{sup dy}, that is, T{sub 0} at dynamic loading rates as obtained in impact and other dynamic tests. For this purpose, the same dataset that was used by Wallin for deriving the original WSRE has been used. It has also been found that the dynamic reference temperature obtained by applying the modified Schindler procedure (MSP) to Charpy V-notch (CVN) impact tests, that is, T{sub QSch}{sup dy}, provides a conservative or close estimate of reference temperature corresponding to a loading rate of {approx}10{sup 6} MPa {radical}m s{sup -1}. Then using the T{sub QSch}{sup dy} in the IWSRE along with RT-YS and SIF rate of 10{sup 6} MPa {radical}m s{sup -1}, results in an estimate of quasi-static T{sub 0}, namely, T{sub QMSP-IW}, the subscript indicating use of both the

  16. On "Tough" Movement in Spanish.

    Science.gov (United States)

    Reider, Michael

    1993-01-01

    A survey of native Spanish speakers from both Spain and Latin America found that the choice of predicate adjectives governing "tough" constructions in Spanish (e.g., "el libro es facil de leer") varies by individual, but some patterns did emerge that suggest "tough" constructions and "it is" constructions…

  17. Effect of post-weld heat treatment on microstructure, hardness and low-temperature impact toughness of electron beam welds of NIFS-HEAT-2 and CEA-J57 heats of V–4Ti–4Cr alloy

    Directory of Open Access Journals (Sweden)

    V. Tsisar

    2016-12-01

    Full Text Available Bead-on-plate electron beam welding in high vacuum atmosphere was applied to the plates of NIFS-HEAT-2 and CEA-J57 heats of V–4Ti–4Cr alloy. Effect of post-weld heat treatment (PWHT in the temperature range 673–1273K on the hardness, impact toughness at 77K and microstructure of weld metal was investigated. After PWHT at 773K, hardness of weld metal slightly decreases from 180HV100 (as-welded state to ∼170HV100 while absorbed energy increases up to ∼10J showing ductile fracture mode. PWHT at 973K results in re-hardening of weld metal up to ∼180HV100 caused by re-precipitation of Ti–C,O,N precipitates and corresponding decreasing absorbed energy to ∼2J with brittle fracture mode. PWHT in-between 1073–1273K results in gradual recovery of hardness towards values comparable with those of base metal. Impact toughness (77 K of weld metal after PWHT at 1073K is not recovered nether to the value in as-welded state nor to that one of base metal.

  18. Pre-dispersed organo-montmorillonite (organo-MMT) nanofiller: Morphology, cytocompatibility and impact on flexibility, toughness and biostability of biomedical ethyl vinyl acetate (EVA) copolymer.

    Science.gov (United States)

    Osman, Azlin F; M Fitri, Tuty Fareyhynn; Rakibuddin, Md; Hashim, Fatimah; Tuan Johari, Syed Ahmad Tajudin; Ananthakrishnan, Rajakumar; Ramli, Rafiza

    2017-05-01

    Polymer-clay based nanocomposites are among the attractive materials to be applied for various applications, including biomedical. The incorporation of the nano sized clay (nanoclay) into polymer matrices can result in their remarkable improvement in mechanical, thermal and barrier properties as long as the nanofillers are well exfoliated and dispersed throughout the matrix. In this work, exfoliation strategy through pre-dispersing process of the organically modified montmorillonite (organo-MMT) nanofiller was done to obtain ethyl vinyl acetate (EVA) nanocomposite with improved flexibility, toughness, thermal stability and biostability. Our results indicated that the degree of organo-MMT exfoliation affects its cytotoxicity level and the properties of the resulting EVA nanocomposite. The pre-dispersed organo-MMT by ultrasonication in water possesses higher degree of exfoliation as compared to its origin condition and significantly performed reduced cytotoxicity level. Beneficially, this nanofiller also enhanced the EVA flexibility, thermal stability and biostability upon the in vitro exposure. We postulated that these were due to plasticizing effect and enhanced EVA-nanofiller interactions contributing to more stable chemical bonds in the main copolymer chains. Improvement in copolymer flexibility is beneficial for close contact with human soft tissue, while enhancement in toughness and biostability is crucial to extend its life expectancy as insulation material for implantable device. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. SCK-CEN Contribution to the''Relation between different measures of exposure-induced shifts in ductile-brittle transition temperatures'' (REFEREE). Progress Report

    Energy Technology Data Exchange (ETDEWEB)

    Chaouadi, R.; Van Walle, E.; Fabry, A.; Puzzolante, J.L

    1998-08-01

    The relationship between Charpy-V (CVN) impact, fracture toughness and tensile properties for selected reactor pressure -vessel steels in the transition temperature range are investigated. Data on the testing of unirradiated material are reported. The applied methods include chemical analysis, Charpy-V impact testing, tensile testing and fracture toughness determination.

  20. Dynamic fracture toughness of ceramic composites

    Science.gov (United States)

    Yang, K. H.; Kobayashi, A. S.; Emery, A. F.

    1988-01-01

    The dynamic fracture toughness vs crack velocity relationships of TiB2 particulate-reinforced SiC-matrix and SiC whisker-reinforced Al2O3-matrix composites were determined at both room temperature and 1200 C with impacted, single-edge notched three-point bend specimens. Rapid crack initiation and propagation were monitored by a laser interferometric-displacement gage system. A FEM model that transmitted the measured outside-impact load to the specimen within the furnace was used to characterize the entire loading system-specimen unit. Small differences were measured between the room temperature and 1200 C dynamic responses.

  1. 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.

  2. Effects of nitrogen and strain age embrittlement on toughness of MMA welds. A final report on the joint reserach project - GKSS Research Centre, Geesthacht, Germany, and Oerlikon Welding Ltd., Zurich, Switzerland

    Energy Technology Data Exchange (ETDEWEB)

    Kocak, M. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Materialforschung; Achar, D.R.G.; Evans, G.M. [OERLIKON Welding Ltd., Zurich (Switzerland)

    1998-12-31

    A detailed literature review has been carried out on the topic to identify the areas requiring further investigations. Based on this investigations have been carried out to evaluate the influence of dissolved nitrogen in weld metals on their toughness and strain aging behaviour through fracture mechanics as well as conventional impact testing approaches. MMA C-Mn steel weld metals bearing nitrogen between 80 to 210 ppm were investigated under four different post-weld conditions, namely: 1. as welded, 2. stress relieved, 3. artificially strain aged and 4. artificially strain aged and stress relieved. Quantitative metallography and low load microhardness studies of microphases were integral part of these investigations. The results demonstrate the highly detrimental effect of nitrogen on the toughness behaviour of C-Mn steel weld metal particularly under strain aging conditions. This is substantiated through decrease of acicular ferrite with the accompanying increase in primary ferrite and ferrite with second phases in the microstructures. Also, there is a distinctive increase in acicular ferrite microhardness. Post-weld stress relieving heat treatment under these conditions effects only marginal improvement in toughness and shifts the fracture behaviour from brittle to ductile or quasi-ductile only in the case of low nitrogen weld metals. Comparing the results of the CTOD and Charpy tests, it is observed that both methods measure the influence of nitrogen on toughness behaviour in the same trend but the magnitudes of the effect measured are different whereby the fracture mechanics method appears very conservative. (orig.) [Deutsch] Untersucht werden der Einfluss von Stickstoff im Bereich von 80-120 ppm auf die Zaehigkeit und Reckalterungsversproedungs-Verhaeltnisse des C-Mn-Strahlschweissgutes. Die Pruefungen erfolgen mit technologischen Kerbschlagbiege- und CTOD-Versuchen an Schweissguetern, die durch mehrlagiges Lichtbogenschweissen hergestellt wurden, unter vier

  3. 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.

  4. Tough2{_}MP: A parallel version of TOUGH2

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Keni; Wu, Yu-Shu; Ding, Chris; Pruess, Karsten

    2003-04-09

    TOUGH2{_}MP is a massively parallel version of TOUGH2. It was developed for running on distributed-memory parallel computers to simulate large simulation problems that may not be solved by the standard, single-CPU TOUGH2 code. The new code implements an efficient massively parallel scheme, while preserving the full capacity and flexibility of the original TOUGH2 code. The new software uses the METIS software package for grid partitioning and AZTEC software package for linear-equation solving. The standard message-passing interface is adopted for communication among processors. Numerical performance of the current version code has been tested on CRAY-T3E and IBM RS/6000 SP platforms. In addition, the parallel code has been successfully applied to real field problems of multi-million-cell simulations for three-dimensional multiphase and multicomponent fluid and heat flow, as well as solute transport. In this paper, we will review the development of the TOUGH2{_}MP, and discuss the basic features, modules, and their applications.

  5. Fracture toughness of graphite composites

    Energy Technology Data Exchange (ETDEWEB)

    Blikstad, M.

    1985-01-01

    The first two papers in the thesis deal with moisture absorption in graphite/epoxy materials. Both one- and three-dimensional moisture absoption were studied. The diffusion along the fiber direction was measured. A great difference was found between the diffusion along the fiber direction and the diffusion perpendicular to the fiber direction. The experimental results were compared with three-dimensional calculations based on Fick's second law of diffusion. Edge delamination is the main subject of the next two papers. Angle-ply specimens with standard and toughened resin were loaded in tension before and after moisture absorption to obtain the fracture toughness for edge delamination. The mode of loading for inherent cracks along the edge in these types of specimens is essentially a combination of mode I and Mode III. The delamination fracture surfaces were studied in a scanning electron microscope (SEM). They exhibited hackle formation and the tilt of the hackles was found to be characteristic of the state of stress in the interlaminar region. The obtained fracture toughnesses were analyzed according to the geometrical fracture criterion. Change to a more ductile epoxy resin increased the fracture toughness. In the fifth paper the fracture toughness of ply cracking was measured in unidirectional off-axis and rail shear test specimens. By varying the off-axis angle the mode of loading was varied from pure mode I to nearly mode II. The rail shear test gave pure mode II loading. The fracture surfaces were investigated in a SEM. The obtained fracture toughness was analyzed according to the quadratic mixed mode fracture criterion. Moisturizatio of the standard resin laminate and change to a more ductile epoxy resin increased the fracture toughness. However, when the toughened resin laminate had absorbed moisture, its toughness decreased substantially.

  6. Mental toughness: progress and prospects.

    Science.gov (United States)

    Gucciardi, Daniel F

    2017-08-01

    Mental toughness (MT) has become a popular area of investigation and practice within sport and exercise psychology over the past two decades. Since the turn of the twenty first century, there have been hundreds of studies published on mental toughness, yet concerns remain about the conceptualisation and measurement of mental toughness. In this paper, I take stock of past work with the goal of clarifying and elaborating the most fundamental and common aspects of MT. I also look to the future and outline key substantive and methodological issues that may offer the greatest potential for refining the conceptualisation of MT and contributing to theory building on this concept. My hope is that this information will provide a platform from which to foster coherent and systematic scholarly work on MT. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Study on impact properties of creep-resistant steel thermally simulated heat affected zone

    Directory of Open Access Journals (Sweden)

    Mitrović Radivoje M.

    2012-01-01

    Full Text Available The steam pipe line (SPL and steam line material, along with its welded joints, subject to damage that accumulates during operation in coal power plants. As a result of thermal fatigue, dilatation of SPL at an operating temperature may lead to cracks initiation at the critical zones within heat affected zone (HAZ of steam pipe line welded joints. By registration of thermal cycle during welding and subsequent HAZ simulation is possible to obtain target microstructure. For the simulation is chosen heat resisting steel, 12H1MF (designation 13CrMo44 according to DIN standard. From the viewpoint of mechanical properties, special attention is on impact toughness mostly because very small number of available references. After simulation of single run and multi run welding test on instrumented Charpy pendulum. Metallographic and fractographic analysis is also performed, on simulated 12H1MF steel from service and new, unused steel. The results and correlation between microstructure and impact toughness is discussed, too.

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

    African Journals Online (AJOL)

    , scant attention has been paid to the psychological processes that underpin mental toughness. Objectives: To explore the relationship between mindfulness and mental toughness among provincial adolescent female hockey players.

  9. iTOUGH2 Command Reference

    Energy Technology Data Exchange (ETDEWEB)

    Finsterle, Stefan

    2002-06-18

    iTOUGH2 is a program for parameter estimation, sensitivity analysis, and uncertainty propagation analysis. It is based on the TOUGH2 simulator for non-isothermal multiphase flow in fractured and porous media. This report contains a detailed description of all iTOUGH2 commands.

  10. iTOUGH2 Sample Problems

    Energy Technology Data Exchange (ETDEWEB)

    Finsterle, Stefan

    2002-06-18

    iTOUGH2 is a program for parameter estimation, sensitivity analysis, and uncertainty propagation analysis. It is based on the TOUGH2 simulator for non-isothermal multiphase flow in fractured and porous media. This report contains a collection of iTOUGH2 sample problems.

  11. Improving the toughness of ultrahigh strength steel

    Energy Technology Data Exchange (ETDEWEB)

    Soto, Koji [Univ. of California, Berkeley, CA (United States)

    2002-01-01

    The ideal structural steel combines high strength with high fracture toughness. This dissertation discusses the toughening mechanism of the Fe/Co/Ni/Cr/Mo/C steel, AerMet 100, which has the highest toughness/strength combination among all commercial ultrahigh strength steels. The possibility of improving the toughness of this steel was examined by considering several relevant factors.

  12. Influence of tungsten, carbon and nitrogen on toughness and weldability of low activation austenitic high manganese stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Hosoi, H.; Abraham, M.; Kutsuna, M.; Miyahara, K. (Nagoya Univ., Dept. of Materials Science and Engineering, Chikusa (Japan)); Shimoide, Y. (Daido Inst. of Technology, Dept. of Mechanical Engineering, Nagoya (Japan))

    1992-09-01

    The effect of alloying elements of tungsten, carbon and nitrogen on high temperature strength, toughness and weldability of Fe-12Cr-15Mn alloy has been investigated. The high temperature strength of Fe-12Cr-15Mn-0.2C-0.1N at 873 K increases with the addition of 2-300W without affecting ductility. The toughness as estimated by Charpy tests, is also not influenced by the addition of 2-3%W, while the increase of carbon content decreases the absorbed energy. The transition temperature shifts to higher temperature by aging at 873 K for 3600 ks, but it is still lower than room temperature. The degradation of toughness after aging is considered to be related to the precipitation of M[sub 23]C[sub 6] on grain boundaries. The weldability evaluated by hot cracking susceptibility is not affected by alloying of tungsten and carbon in this alloy system. It is noted that the alloys studied show less hot cracking susceptibility than commercial AISI 316L stainless steel. (orig.).

  13. 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

  14. Ductile fracture toughness of modified A 302 Grade B Plate materials, data analysis. Volume 1

    Energy Technology Data Exchange (ETDEWEB)

    McCabe, D.E.; Manneschmidt, E.T.; Swain, R.L.

    1997-01-01

    The goal of this work was to develop ductile fracture toughness data in the form of J-R curves for modified A302 grade B plate materials typical of those used in reactor pressure vessels. A previous experimental study on one heat of A302 grade B plate showed decreasing J-R curves with increased specimen thickness. This characteristic has not been observed in tests made on recent production materials of A533 grade B and A508 class 2 pressure vessel steels. It was unknown if the departure from norm for the material was a generic characteristic for all heats of A302 grade B steels or unique to that particular plate. Seven heats of modified A302 grade B steel and one heat of vintage A533 grade B steel were tested for chemical content, tensile properties, Charpy transition temperature curves, drop-weight nil-ductility transition (NDT) temperature, and J-R curves. Tensile tests were made in the three principal orientations and at four temperatures, ranging from room temperature to 550F. Charpy V-notch transition temperature curves were obtained in longitudinal, transverse, and short transverse orientations. J-R curves were made using four specimen sizes (1/2T, 1T, 2T, and 4T). The fracture mechanics-based evaluation method covered three test orientations and three test temperatures (80, 400, and 550F). However, the coverage of these variables was contingent upon the amount of material provided. Drop-weight NDT temperature was determined for the T-L orientation only. None of the heats of modified A302 grade B showed size effects of any consequence on the J-R curve behavior. Crack orientation effects were present, but none were severe enough to be reported as atypical. A test temperature increase from 180 to 550F produced the usual loss in J-R curve fracture toughness. Generic J-R curves and curve fits were generated to represent each heat of material. This volume deals with the evaluation of data and the discussion of technical findings. 8 refs., 18 figs., 8 tabs.

  15. Ductile fracture toughness of modified A 302 grade B plate materials. Volume 2

    Energy Technology Data Exchange (ETDEWEB)

    McCabe, D.E.; Manneschmidt, E.T.; Swain, R.L.

    1997-02-01

    The objective of this work was to develop ductile fracture toughness data in the form of J-R curves for modified A 302 grade B plate materials typical of those used in fabricating reactor pressure vessels. A previous experimental study at Materials Engineering Associates (MEA) on one particular heat of A 302 grade B plate showed decreasing J-R curves with increased specimen thickness. This characteristic has not been observed in numerous tests made on the more recent production materials of A 533 grade B and A 508 class 2 pressure vessel steels. It was unknown if the departure from norm for the MEA material was a generic characteristic for all heats of A 302 grade B steels or just unique to that one particular plate. Seven heats of modified A 302 grade B steel and one heat of vintage A 533 grade B steel were provided to this project by the General Electric Company of San Jose, California. All plates were tested for chemical content, tensile properties, Charpy transition temperature curves, drop-weight nil-ductility transition (NDT) temperature, and J-R curves. Tensile tests were made in the three principal orientations and at four temperatures, ranging from room temperature to 550{degrees}F (288{degrees}C). Charpy V-notch transition temperature curves were obtained in longitudinal, transverse, and short transverse orientations. J-R curves were made using four specimen sizes (1/2T, IT, 2T, and 4T). None of the seven heats of modified A 302 grade showed size effects of any consequence on the J-R curve behavior. Crack orientation effects were present, but none were severe enough to be reported as atypical. A test temperature increase from 180 to 550{degrees}F (82 to 288{degrees}C) produced the usual loss in J-R curve fracture toughness. Generic J-R curves and mathematical curve fits to the same were generated to represent each heat of material. This volume is a compilation of all data developed.

  16. Effects of Thermal Aging on Material Properties, Stress Corrosion Cracking, and Fracture Toughness of AISI 316L Weld Metal

    Science.gov (United States)

    Lucas, Timothy; Forsström, Antti; Saukkonen, Tapio; Ballinger, Ronald; Hänninen, Hannu

    2016-08-01

    Thermal aging and consequent embrittlement of materials are ongoing issues in cast stainless steels, as well as duplex, and high-Cr ferritic stainless steels. Spinodal decomposition is largely responsible for the well-known "748 K (475 °C) embrittlement" that results in drastic reductions in ductility and toughness in these materials. This process is also operative in welds of either cast or wrought stainless steels where δ-ferrite is present. While the embrittlement can occur after several hundred hours of aging at 748 K (475 °C), the process is also operative at lower temperatures, at the 561 K (288 °C) operating temperature of a boiling water reactor (BWR), for example, where ductility reductions have been observed after several tens of thousands of hours of exposure. An experimental program was carried out in order to understand how spinodal decomposition may affect changes in material properties in Type 316L BWR piping weld metals. The study included material characterization, nanoindentation hardness, double-loop electrochemical potentiokinetic reactivation (DL-EPR), Charpy-V, tensile, SCC crack growth, and in situ fracture toughness testing as a function of δ-ferrite content, aging time, and temperature. SCC crack growth rates of Type 316L stainless steel weld metal under simulated BWR conditions showed an approximate 2 times increase in crack growth rate over that of the unaged as-welded material. In situ fracture toughness measurements indicate that environmental exposure can result in a reduction of toughness by up to 40 pct over the corresponding at-temperature air-tested values. Material characterization results suggest that spinodal decomposition is responsible for the degradation of material properties measured in air, and that degradation of the in situ properties may be a result of hydrogen absorbed during exposure to the high-temperature water environment.

  17. Influence of process parameters on torsional strength, impact toughness and hardness of dissimilar AISI 304 and AISI 1021 friction welded steels

    Directory of Open Access Journals (Sweden)

    Amit Handa

    2014-06-01

    Full Text Available In this present study an attempt was made to join austenitic stainless steel (AISI 304 with low alloy steel (AISI 1021 at different rotational speeds and at different axial pressures and then determining the strength of the joint by means of mechanical properties such as torsional strength, impact strength and micro hardness. The experimental results indicate that the rotational speed and the axial pressure have a significant effect on the mechanical properties of the joint and it is possible to improve the quality of the joint by selecting the optimum parameters.

  18. TOUGH3: A new efficient version of the TOUGH suite of multiphase flow and transport simulators

    Science.gov (United States)

    Jung, Yoojin; Pau, George Shu Heng; Finsterle, Stefan; Pollyea, Ryan M.

    2017-11-01

    The TOUGH suite of nonisothermal multiphase flow and transport simulators has been updated by various developers over many years to address a vast range of challenging subsurface problems. The increasing complexity of the simulated processes as well as the growing size of model domains that need to be handled call for an improvement in the simulator's computational robustness and efficiency. Moreover, modifications have been frequently introduced independently, resulting in multiple versions of TOUGH that (1) led to inconsistencies in feature implementation and usage, (2) made code maintenance and development inefficient, and (3) caused confusion to users and developers. TOUGH3-a new base version of TOUGH-addresses these issues. It consolidates both the serial (TOUGH2 V2.1) and parallel (TOUGH2-MP V2.0) implementations, enabling simulations to be performed on desktop computers and supercomputers using a single code. New PETSc parallel linear solvers are added to the existing serial solvers of TOUGH2 and the Aztec solver used in TOUGH2-MP. The PETSc solvers generally perform better than the Aztec solvers in parallel and the internal TOUGH3 linear solver in serial. TOUGH3 also incorporates many new features, addresses bugs, and improves the flexibility of data handling. Due to the improved capabilities and usability, TOUGH3 is more robust and efficient for solving tough and computationally demanding problems in diverse scientific and practical applications related to subsurface flow modeling.

  19. 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.

  20. The year of tough decisions

    Directory of Open Access Journals (Sweden)

    Vladimir Aleksandrovich Ilyin

    2015-01-01

    Full Text Available The third year of V.V. Putin’s Presidency, his current third political cycle, is coming to an end. It was a year of tough decisions, and this was what the President pointed out in his annual Address to the Federal Assembly of the Russian Federation on December 4. Delivering his Address, V.V. Putin noted that in 2014 Russia faced trials that only a mature and united nation and a truly sovereign and strong state can withstand

  1. 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.

  2. Computational evaluation of the constraint loss on the fracture toughness of reactor pressure vessel steels; Evaluacion computacional del efecto de la perdida de constriccion en la tenacidad de fractura de la vasija de reactores nucleares

    Energy Technology Data Exchange (ETDEWEB)

    Serrano Garcia, M.

    2007-07-01

    The Master Curve approach is included on the ASME Code through some Code Cases to assess the reactor pressure vessel integrity. However, the margin definition to be added is not defined as is the margin to be added when the Master Curve reference temperature T{sub 0} is obtained by testing pre-cracked Charpy specimens. The reason is that the T{sub 0} value obtained with this specimen geometry is less conservative than the value obtained by testing compact tension specimens possible due to a loss of constraint. The two parameter fracture mechanics, considered as an extension of the classical fracture mechanics, coupled to a micromechanical fracture models is a valuable tool to assess the effect of constraint loss on fracture toughness. The definition of a parameter able to connect the fracture toughens value to the constraint level on the crack tip will allow to quantify margin to be added to the T{sub 0} value when this value is obtained testing the pre-cracked Charpy specimens included in the surveillance capsule of the reactor pressure vessel. The Nuclear Regulatory Commission (NRC) define on the To value obtained by testing compact tension specimens and ben specimens (as pre-cracked Charpy are) bias. the NRC do not approved any of the direct applications of the Master Curve the reactor pressure vessel integrity assessment until this bias will be quantified in a reliable way. the inclusion of the bias on the integrity assessment is done through a margin to be added. In this thesis the bias is demonstrated an quantified empirical and numerically and a generic value is suggested for reactor pressure vessel materials, so that it can be used as a margin to be added to the T{sub 0} value obtained by testing the Charpy specimens included in the surveillance capsules. (Author) 111 ref.

  3. Elaboración de procedimientos de ensayo de flexión por choque y de verificación de péndulo Charpy

    OpenAIRE

    Bayona Revilla, Lucía

    2017-01-01

    En el presente trabajo se han elaborado dos tipos de procedimientos de ensayo: . Procedimiento de ensayo de flexión por choque con péndulo Charpy. . Procedimiento de verificación de las máquinas de ensayo. El ensayo de flexión con péndulo Charpy permite determinar la energía absorbida por un determinado material en el instante del impacto. Mediante la utilización de probetas de dimensiones normalizadas con entalla en V, dicho ensayo determina además la temperatura de transición dúcti...

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

    African Journals Online (AJOL)

    Kathryn van Boom

    intervention might be indicated within the areas of sport and performance psychology in ... with 6% having previously been selected for national teams. Measures .... CAMM = Child and Adolescent Mindfulness Measure; SMTQ Tot = Sport Mental Toughness Questionnaire Total Score; SMTQ Cnf = Sport Mental Toughness.

  5. 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.

  6. Low-impact, high toughness transportation barriers.

    Science.gov (United States)

    2012-10-01

    Alternatives to existing transportation truck escape ramps and crash barriers are examined using arrays of : wood, bamboo, and fiberglass structural elements that act as energy absorbers as they deform. The : behaviors of each material type are analy...

  7. 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

  8. Tough, bio-inspired hybrid materials

    Energy Technology Data Exchange (ETDEWEB)

    Munch, Etienne; Launey, Maximimilan E.; Alsem, Daan H.; Saiz, Eduardo; Tomsia, Antoni P.; Ritchie, Robert O.

    2008-10-06

    The notion of mimicking natural structures in the synthesis of new structural materials has generated enormous interest but has yielded few practical advances. Natural composites achieve strength and toughness through complex hierarchical designs extremely difficult to replicate synthetically. Here we emulate Nature's toughening mechanisms through the combination of two ordinary compounds, aluminum oxide and polymethylmethacrylate, into ice-templated structures whose toughness can be over 300 times (in energy terms) that of their constituents. The final product is a bulk hybrid ceramic material whose high yield strength and fracture toughness ({approx}200 MPa and {approx}30 MPa{radical}m) provide specific properties comparable to aluminum alloys. These model materials can be used to identify the key microstructural features that should guide the synthesis of bio-inspired ceramic-based composites with unique strength and toughness.

  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. On the fracture toughness of advanced materials

    Energy Technology Data Exchange (ETDEWEB)

    Launey, Maximilien E.; Ritchie, Robert O.

    2008-11-24

    Few engineering materials are limited by their strength; rather they are limited by their resistance to fracture or fracture toughness. It is not by accident that most critical structures, such as bridges, ships, nuclear pressure vessels and so forth, are manufactured from materials that are comparatively low in strength but high in toughness. Indeed, in many classes of materials, strength and toughness are almost mutually exclusive. In the first instance, such resistance to fracture is a function of bonding and crystal structure (or lack thereof), but can be developed through the design of appropriate nano/microstructures. However, the creation of tough microstructures in structural materials, i.e., metals, polymers, ceramics and their composites, is invariably a compromise between resistance to intrinsic damage mechanisms ahead of the tip of a crack (intrinsic toughening) and the formation of crack-tip shielding mechanisms which principally act behind the tip to reduce the effective 'crack-driving force' (extrinsic toughening). Intrinsic toughening is essentially an inherent property of a specific microstructure; it is the dominant form of toughening in ductile (e.g., metallic) materials. However, for most brittle (e.g., ceramic) solids, and this includes many biological materials, it is largely ineffective and toughening conversely must be developed extrinsically, by such shielding mechanisms as crack bridging. From a fracture mechanics perspective, this results in toughening in the form of rising resistance-curve behavior where the fracture resistance actually increases with crack extension. The implication of this is that in many biological and high-strength advanced materials, toughness is developed primarily during crack growth and not for crack initiation. This is an important realization yet is still rarely reflected in the way that toughness is measured, which is invariably involves the use of single-value (crack-initiation) parameters such as

  11. Effect of Normalizing Temperature on Fracture Characteristic of Tensile and Impact Tested Creep Strength-Enhanced Ferritic P92 Steel

    Science.gov (United States)

    Saini, N.; Pandey, C.; Mahapatra, M. M.

    2017-11-01

    The high-temperature Cr-Mo creep strength-enhanced ferritic (CSEF) steels are mainly used in nuclear and thermal power plants. In the present investigation, a systematic study on fracture surface morphologies of tensile and impact tested specimens and mechanical properties of cast and forged (C&F) P92 steel was performed for various heat treatment conditions. The heat treatment was carried out in normalizing temperature range of 950-1150 °C and then tempered to a fixed tempering temperature of 760 °C. The effect of varying normalizing temperatures before and after tempering on microstructure evolution, tensile properties, Vicker's hardness and Charpy toughness was studied. The normalizing temperature before and after tempering was having a noticeable effect on mechanical properties of as-received P92 steel. The fracture surface of impact and tensile tested samples was also studied for various normalizing temperatures with or without tempering. Fracture surface morphology was affected by the presence of secondary phase carbide particles. The fraction area of cleavage facets on the tensile fracture surface was found to be increased with an increase in the normalizing temperature. The fractured tensile specimens were characterized by transgranular ductile dimples, tear ridges and transgranular cleavage facets for various heat treatments. The fracture mode of impact tested samples was more complex. It showed both quasi-cleavage facets and ductile dimple tearing for various normalizing temperatures.

  12. Effect of Normalizing Temperature on Fracture Characteristic of Tensile and Impact Tested Creep Strength-Enhanced Ferritic P92 Steel

    Science.gov (United States)

    Saini, N.; Pandey, C.; Mahapatra, M. M.

    2017-10-01

    The high-temperature Cr-Mo creep strength-enhanced ferritic (CSEF) steels are mainly used in nuclear and thermal power plants. In the present investigation, a systematic study on fracture surface morphologies of tensile and impact tested specimens and mechanical properties of cast and forged (C&F) P92 steel was performed for various heat treatment conditions. The heat treatment was carried out in normalizing temperature range of 950-1150 °C and then tempered to a fixed tempering temperature of 760 °C. The effect of varying normalizing temperatures before and after tempering on microstructure evolution, tensile properties, Vicker's hardness and Charpy toughness was studied. The normalizing temperature before and after tempering was having a noticeable effect on mechanical properties of as-received P92 steel. The fracture surface of impact and tensile tested samples was also studied for various normalizing temperatures with or without tempering. Fracture surface morphology was affected by the presence of secondary phase carbide particles. The fraction area of cleavage facets on the tensile fracture surface was found to be increased with an increase in the normalizing temperature. The fractured tensile specimens were characterized by transgranular ductile dimples, tear ridges and transgranular cleavage facets for various heat treatments. The fracture mode of impact tested samples was more complex. It showed both quasi-cleavage facets and ductile dimple tearing for various normalizing temperatures.

  13. 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.

  14. 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)

  15. The conflicts between strength and toughness

    Science.gov (United States)

    Ritchie, Robert O.

    2011-11-01

    The attainment of both strength and toughness is a vital requirement for most structural materials; unfortunately these properties are generally mutually exclusive. Although the quest continues for stronger and harder materials, these have little to no use as bulk structural materials without appropriate fracture resistance. It is the lower-strength, and hence higher-toughness, materials that find use for most safety-critical applications where premature or, worse still, catastrophic fracture is unacceptable. For these reasons, the development of strong and tough (damage-tolerant) materials has traditionally been an exercise in compromise between hardness versus ductility. Drawing examples from metallic glasses, natural and biological materials, and structural and biomimetic ceramics, we examine some of the newer strategies in dealing with this conflict. Specifically, we focus on the interplay between the mechanisms that individually contribute to strength and toughness, noting that these phenomena can originate from very different lengthscales in a material's structural architecture. We show how these new and natural materials can defeat the conflict of strength versus toughness and achieve unprecedented levels of damage tolerance within their respective material classes.

  16. Proposed mixed-mode dynamic fracture toughness testing method using a new specimen

    Energy Technology Data Exchange (ETDEWEB)

    Wada, H.; Hinoshita, A. [Daido Institute of Technology, Nagoya (Japan); Calder, C.A.; Kennedy, T.C. [Oregon State Univ., Corvallis, OR (United States)

    1996-12-31

    To find a simple and highly accurate testing method for determining the mixed-mode dynamic fracture toughness in a wide range of ratio of opening and sliding modes, the authors applied a combination technique using an electrical resistance strain gage method and a dynamic finite element method (FEM) to determine the mixed-mode dynamic fracture toughness. They used measuring and recording devices associated with an impact fracture apparatus based on an air gun. The impact fracture test was conducted to assess the mixed-mode dynamic fracture toughness testing method under single-point bending for three specimens of polymethyl methacrylate (PMMA). The ratio of the opening mode deformation to the sliding mode can be changed by adjusting the hitting point. To measure a dynamic stress intensity factors (SIF) K{sub 1}(t) and a crack initiation time, a single axis strain gage was mounted in the vicinity of the crack tip.

  17. 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).

  18. Heavy-section fracture toughness screening specimen

    Science.gov (United States)

    Shannon, J. L., Jr.; Brown, W. F., Jr.; Donald, J. K.

    1977-01-01

    The reported study has the objective to fix the proportions and limits of application of a double-edge-notch specimen with one of the notches tipped with a fatigue crack (DENC). Details regarding the DENC specimen are discussed, taking into account specimen length, notch length, specimen width and thickness, and the loading pins. The influence of specimen width and thickness on the crack strenght and apparent plane-strain fracture toughness of the specimen has been determined for eight alloys. It is concluded that the DENC specimen shows promise for screening alloys with reference to their plane-strain fracture toughness in sections up to 1 in.

  19. 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.

  20. Low temperature impact testing of welded structural wrought iron

    Science.gov (United States)

    Rogers, Zachary

    During the second half of the 19th century, structural wrought iron was commonly used in construction of bridges and other structures. Today, these remaining structures are still actively in use and may fall under the protection of historic preservation agencies. Continued use and protection leads to the need for inspection, maintenance, and repair of the wrought iron within these structures. Welding can be useful to achieve the appropriate repair, rehabilitation, or replacement of wrought iron members. There is currently very little published on modern welding techniques for historic wrought iron. There is also no pre-qualified method for this welding. The demand for welding in the repair of historic structural wrought iron has led to a line of research investigating shielded metal arc welding (SMAW) of historic wrought iron at the University of Colorado Denver. This prior research selected the weld type and other weld specifications to try and achieve a recognized specific welding procedure using modern SMAW technology and techniques. This thesis continues investigating SMAW of historic wrought iron. Specifically, this thesis addresses the toughness of these welds from analysis of the data collected from performing Charpy V-Notch (CVN) Impact Tests. Temperature was varied to observe the material response of the welds at low temperature. The wrought iron used in testing was from a historic vehicle bridge in Minnesota, USA. This area, and many other areas with wrought iron structures, can experience sustained or fluctuating temperatures far below freezing. Investigating the toughness of welds in historic wrought iron at these temperatures is necessary to fully understand material responses of the existing structures in need of maintenance and repair. It was shown that welded wrought iron is tougher and more ductile than non-welded wrought iron. In regards to toughness, welding is an acceptable repair method. Information on wrought iron, low temperature failure

  1. 46 CFR 54.05-6 - Toughness test temperatures.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Toughness test temperatures. 54.05-6 Section 54.05-6... Toughness Tests § 54.05-6 Toughness test temperatures. Each toughness test must be conducted at temperatures not warmer than −20 °F or 10 °F below the minimum service temperature, whichever is lower, except that...

  2. Efeito da temperatura interpasse na microestrutura, tenacidade ao impacto e propagação de trinca por fadiga de uniões soldadas por GTAW do aço ASTM A743-CA6NM Interpass temperature influence on the microstructure, impact toughness and fatigue crack propagation in ASTM A743-CA6NM GTAW welded joints

    Directory of Open Access Journals (Sweden)

    Ruimar Rubens de Gouveia

    2013-06-01

    in welding procedures development that promotes a better toughness, without post welding heat treatment (PWHT. The mainly objective of this paper is analyze the influence of interpass temperature on the microstructure, impact toughness and fatigue crack propagation in CA6NM martensitic stainless steel multipass welded joints, with AWS410NiMo filler metal, with GTAW (gas tungsten arc welding. It was observed the interpass temperature influence on ferrite δ formation, observing intergranular ferrite d formation on the d+g field in 80 ºC interpass temperature, while the sample welded at 150 ºC the formation of ferrite d occurs mainly in the δ monophase field. Ferrite d formation with the lowest temperature interpass promoted an increase in impact toughness and a decrease in the fatigue crack propagation when compared with 150ºC interpass temperature sample. It was observed that GTAW process can be an excellent alternative for CA6NM hydraulic turbine repair, it was also observed a significant interpass temperature influence.

  3. Impact behavior of reduced-activation steels irradiated to 24 dpa

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L.; Alexander, D.J. [Oak Ridge National Laboratory, TN (United States)

    1996-04-01

    Charpy impact properties of eight reduced-activation Cr-W ferritic steels were determined after irradiation to {approx}21-24 dpa in the Fast Flux Test Facility (FFTF) at 365{degree}C. Chromium concentrations in the eight steels ranged from 2.25 to 12wt% Cr (steels contained {approx}0.1%C). the 2 1/4Cr steels contained variations of tungsten and vanadium, and the steels with 5, 9, and 12% Cr, contained a combination of 2% W and 0.25% V. A 9Cr in FFTF to {approx}6-8 and {approx}15-17 dpa. Irradiation caused an increase in the DBTT and decrease in the USE, but there was little further change in the DBTT from that observed after the 15-17 dpa irradiation, indicating that the shift had essentially saturated with fluence. The results are encouraging because they indicate that the effect of irradiation on toughness can be faorably affected by changing composition and microstructure.

  4. Characterization on strength and toughness of welded joint for Q550 ...

    Indian Academy of Sciences (India)

    Abstract. Q550 high strength steel was welded using gas shielded arc welding and three different welding wires without pre- or post-heat treatments. The paper investigates the influence of welding wire on the microstructure, tensile strength and impact toughness of Q550 steel weld joints. Results showed that the ...

  5. Characterization on strength and toughness of welded joint for Q550 ...

    Indian Academy of Sciences (India)

    Q550 high strength steel was welded using gas shielded arc welding and three different welding wires without pre- or post-heat treatments. The paper investigates the influence of welding wire on the microstructure, tensile strength and impact toughness of Q550 steel weld joints. Results showed that the microstructure of ...

  6. Effect of weld heat input on toughness and structure of HAZ of a new ...

    Indian Academy of Sciences (India)

    Unknown

    lysed by using H-800 transmission electron microscope and electron diffraction technique. 3. Results and analysis. 3.1 Toughness and fracture morphology in the heat-affected zone. Effect of the weld heat input (E) on the impact energy in the HAZ of HQ130 super-high strength steel is shown in. *Author for correspondence ...

  7. Effects of Ultra-Fast Cooling After Hot Rolling and Intercritical Treatment on Microstructure and Cryogenic Toughness of 3.5%Ni Steel

    Science.gov (United States)

    Wang, Meng; Liu, Zhenyu

    2017-07-01

    A novel process comprised of ultra-fast cooling after control rolling, intercritical quenching and tempering (UFC-LT) was applied to 3.5%Ni steel. In addition, quenching and tempering (QT) treatment was conducted in comparison. The present study focuses on the relationship between the microstructure and cryogenic toughness of 3.5%Ni steel. Results show that the microstructure of steel treated by UFC-LT consisted of tempered martensite, intercritical ferrite and two types of reversed austenite (RA) (needle shape and blocky). Compared to the QT sample, the UFC-LT sample's ultimate tensile strength decreased slightly, while its elongation increased from 32.3 to 35.7%, and its Charpy absorption energy at -135 °C increased from 112 to 237 J. The ductile-brittle transition temperature of UFC-LT sample was lower than that of the QT sample by 18 °C. The superior cryogenic toughness after UFC-LT compared to QT treatment can be attributed to the dissolution of cementite, approximately 3.0% increase in RA and the decrease in effective grain size.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Toughness of polymers under various fracture conditions

    Science.gov (United States)

    Kwon, Hyock-Ju

    Fracture toughness and deformation behaviour of ductile polymers were investigated under various conditions and fracture modes. New methodologies to encourage the fracture modes that are hard to be generated in the past have been developed. The thesis proposes test methodology to evaluate the fracture toughness of highly ductile polymers such as high-density polyethylene (HDPE). The first method is based on essential work of fracture (EWF) concept to measure toughness in plane-strain condition, which is about one order of magnitude smaller than the plane-stress counterpart. A new work-partitioning principle was developed to generate thickness-independent EWF values. The thesis also discusses deformation and fracture of polymers involving stable necking. The study shows that crack growth of double-edge-notched tensile (DENT) test on HDPE can be divided into 2 stages. The EWF values for each stage were determined. The study concludes that the EWF value for stable necking varies with the deformation behaviour. Another new method developed is to evaluate the toughness of polymers in shear fracture. The method was firstly applied to poly(acrylonitrile-butadiene-styrene) (ABS). The measured shear fracture toughness was then compared with that in the tensile mode. The results suggest that the ratio of shear to tensile fracture toughness is about 2.5. Validity of the new shear test was further evaluated using HDPE. For HDPE, shear fracture toughness could be determined by double extrapolation of specific work of fracture to zero ligament length and zero ligament thickness. The last part of the thesis explores the yielding behaviour of HDPE using FEM. The study shows that the traditional way to determine the yield stress is not appropriate for the stable necking. Instead, an iterative process is proposed to determine the effective yield stress, based on which the loading level and the deformation behaviour can be simulated accurately. The simulation also considered

  15. Dynamic crack initiation toughness : experiments and peridynamic modeling.

    Energy Technology Data Exchange (ETDEWEB)

    Foster, John T.

    2009-10-01

    This is a dissertation on research conducted studying the dynamic crack initiation toughness of a 4340 steel. Researchers have been conducting experimental testing of dynamic crack initiation toughness, K{sub Ic}, for many years, using many experimental techniques with vastly different trends in the results when reporting K{sub Ic} as a function of loading rate. The dissertation describes a novel experimental technique for measuring K{sub Ic} in metals using the Kolsky bar. The method borrows from improvements made in recent years in traditional Kolsky bar testing by using pulse shaping techniques to ensure a constant loading rate applied to the sample before crack initiation. Dynamic crack initiation measurements were reported on a 4340 steel at two different loading rates. The steel was shown to exhibit a rate dependence, with the recorded values of K{sub Ic} being much higher at the higher loading rate. Using the knowledge of this rate dependence as a motivation in attempting to model the fracture events, a viscoplastic constitutive model was implemented into a peridynamic computational mechanics code. Peridynamics is a newly developed theory in solid mechanics that replaces the classical partial differential equations of motion with integral-differential equations which do not require the existence of spatial derivatives in the displacement field. This allows for the straightforward modeling of unguided crack initiation and growth. To date, peridynamic implementations have used severely restricted constitutive models. This research represents the first implementation of a complex material model and its validation. After showing results comparing deformations to experimental Taylor anvil impact for the viscoplastic material model, a novel failure criterion is introduced to model the dynamic crack initiation toughness experiments. The failure model is based on an energy criterion and uses the K{sub Ic} values recorded experimentally as an input. The failure model

  16. Electron beam weldability of off-shore structural steels: Hardness, impact toughness and CTOD of Creusot Loire steel sample. Report n. 6; Saldabilita` di strutture offshore a fascio elettronico: Resilienza, tenacita` dinamica e CTOD di un acciaio di produzione `Creusot Loire`; Rapporto n. 6

    Energy Technology Data Exchange (ETDEWEB)

    Bigagli, F.; Bosi, R.; Festa, R.; Masperoni, A.; Nenci, F.; Traficante, M. [ENEA, Casaccia (Italy). Area Energia e Innovazione; Savino, G. [Belleli Ricerche, Taranto (Italy)

    1992-12-31

    Hardness and resiliency test data for an electron beam welded Creusot Loire structural steel sample (37 mm thick plate of A633 grade C type 2 steel - consisting of highly pure Fe 500 with a 0.055% Mo addition) were verified through tests conducted in ENEA (Italian Agency for New Technology, Energy and the Environment) and Belleli (Italy) labs. The microstructure of the welded joints was analyzed through non-destructive metallographic techniques. The tenacity of the joints was evaluated through tests establishing hardness, impact toughness and CTOD (Crack Tip Opening Displacement), as well as, through comparative analyses with specified requirements. Overall results indicated mechanical characteristics which were inferior to those reported in previous works and suggested the need for a reconsideration of the steel`s chemical composition.

  17. Thin films and coatings toughening and toughness characterization

    CERN Document Server

    Zhang, Sam

    2015-01-01

    Thin Films and Coatings: Toughening and Toughness Characterization captures the latest developments in the toughening of hard coatings and in the measurement of the toughness of thin films and coatings. Featuring chapters contributed by experts from Australia, China, Czech Republic, Poland, Singapore, Spain, and the United Kingdom, this first-of-its-kind book:Presents the current status of hard-yet-tough ceramic coatingsReviews various toughness evaluation methods for films and hard coatingsExplores the toughness and toughening mechanisms of porous thin films and laser-treated surfacesExamines

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-05-27

    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

  19. Delamination toughness of ultra high molecular weight polyethylene (UHMWPE composites

    Directory of Open Access Journals (Sweden)

    Casas-Rodriguez J.P.

    2012-08-01

    Full Text Available Ultra high molecular weight polyethylene (UHMWPE fibre reinforced composites are an important group of material for armours solutions, where their unique combination of properties could be utilized. A commonly observed failure mode in this kind of unidirectional laminated composites under impact ballistic is delamination between the composite layers. In the present study, an investigation on the delamination toughness behaviour exhibited by UHMWPE composites laminated was made. The interlaminar Mode II critical strain energy release rates of (UHMWPE fibre reinforced composites were characterized using the End Notch Flexural (ENF test. Critical strain energy release rate was obtained from the load – deflection test data using the beam theory expression. It was found that the energy release rate of the composite exhibited a very low value of around 60J/m2 using a moulding pressure of approximately 1200 psi. In order to analyse the delamination resistance of composite, the effects of changing the manufacture process variables and the use of a thermoplastic adhesive film in the composites were investigated. The composite laminates were produced by hot compressing moulding using a film-stacking procedure. It was found that the damage resistance of the UHMWPE composite was influenced by the manufacture method, which affects the Mode II interlaminar fracture toughness and the ballistic response of composites.

  20. Tough photoluminescent hydrogels doped with lanthanide.

    Science.gov (United States)

    Wang, Mei Xiang; Yang, Can Hui; Liu, Zhen Qi; Zhou, Jinxiong; Xu, Feng; Suo, Zhigang; Yang, Jian Hai; Chen, Yong Mei

    2015-03-01

    Photoluminescent hydrogels have emerged as novel soft materials with potential applications in many fields. Although many photoluminescent hydrogels have been fabricated, their scope of usage has been severely limited by their poor mechanical performance. Here, a facile strategy is reported for preparing lanthanide (Ln)-alginate/polyacrylamide (PAAm) hydrogels with both high toughness and photoluminescence, which has been achieved by doping Ln(3+) ions (Ln = Eu, Tb, Eu/Tb) into alginate/PAAm hydrogel networks, where Ln(3+) ions serve as both photoluminescent emitters and physical cross-linkers. The resulting hydrogels exhibit versatile advantages including excellent mechanical properties (∼ MPa strength, ≈ 20 tensile strains, ≈ 10(4) kJ m(-3) energy dissipation), good photoluminescent performance, tunable emission color, excellent processability, and cytocompatibility. The developed tough photoluminescent hydrogels hold great promises for expanding the usage scope of hydrogels. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. 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.

  2. 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

  3. Super-tough carbon-nanotube fibres

    Science.gov (United States)

    Dalton, Alan B.; Collins, Steve; Muñoz, Edgar; Razal, Joselito M.; Ebron, Von Howard; Ferraris, John P.; Coleman, Jonathan N.; Kim, Bog G.; Baughman, Ray H.

    2003-06-01

    The energy needed to rupture a fibre (its toughness) is five times higher for spider silk than for the same mass of steel wire, which has inspired efforts to produce spider silk commercially. Here we spin 100-metre-long carbon-nanotube composite fibres that are tougher than any natural or synthetic organic fibre described so far, and use these to make fibre supercapacitors that are suitable for weaving into textiles.

  4. 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

  5. Measuring fracture toughness in biological materials.

    Science.gov (United States)

    Taylor, David

    2018-01-01

    Many biological materials fail by cracking. Examples are bone fractures, contact damage in eggs, splits in bamboo culm and defects in cartilage. The mechanical property that best describes failure by cracking is fracture toughness, which quantifies the ease with which cracks propagate and defines a material's tolerance for pre-existing cracks and other stress concentrating features. The measurement of fracture toughness presents some challenges, especially for biological materials. To obtain valid results requires care and, in many cases, considerable ingenuity to design an appropriate specimen and test protocol. Common mistakes include incorrect interpretation of the mechanics of loading in unusual specimen designs, and failures occurring at the material's ultimate tensile strength as a result of specimens or cracks being too small. Interpretation of the resulting toughness data may also present challenges, for example when R-curve behaviour is present. In this article, examples of good and bad practice are described, and some recommendations made. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. iTOUGH2 Universal Optimization Using the PEST Protocol

    Energy Technology Data Exchange (ETDEWEB)

    Finsterle, S.A.

    2010-07-01

    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

  7. Marine Structural Steel Toughness Data Bank. Volume 4

    Science.gov (United States)

    1990-08-31

    Break? Did specimen fracture completely? CODIc Critical COD CODi Initial COD CVN Energy Charpy V Energy Crack lgth Crack Length Curve Curve Shape DT...Onien Test Temp COIi CODIc i1 imax Tear Mod degF in In in-lb/in**2 in-lb/in**2 in-lb/in**2 L-T 72 0.0236 0.0380 4346 4315 260.2 L-T 72

  8. Development of High Strength and High Toughness Steels for Reactor Vessel and Surgeline Pipe

    Energy Technology Data Exchange (ETDEWEB)

    Lee, B. S.; Kim, M. C.; Yoon, J. H.; Kim, K. B.; Choi, K. J.; Cho, H. D.

    2010-07-15

    In addition to evaluating the effects of alloying elements, heat treatment conditions, weldability and neutron irradiation behavior were evaluated with 15 types of SA508 Gr.4N model alloys for reactor pressure vessel. The maximum yield strength of 630MPa were obtained by controlling chemical compositions and heat treatment conditions. Model alloys also showed excellent impact toughness and fracture toughness. The microstructure and mechanical properties of weld heat affected zone were evaluated by using simulated specimens and the effects of post weld heat treatment conditions were also investigated. Neutron irradiation behavior at high fluence level were characterized and then compared with commercial reactor pressure vessel steel. The value of transition temperature shift(TTS) was 22 .deg. C at 6.4x10{sup 19} n/cm{sup 2} which is similar to commercial RPV steel. However, its toughness after irradiation is much better than that of unirradiated commercial RPV steel due to the superior initial toughness. Leak-before-break(LBB) properties of type 316 stainless steel model alloys and their welds for surge line were evaluated as well as microstructure and mechanical properties. Tensile tests and J-R fracture resistance tests were carried out at RT and 316 .deg. C. The model alloys showed good tensile strength over standard value, except type 316L which has lower C/N. In the LBB safety analysis result, all of type 316 model alloys have higher allowable load than that of OPR1000 surge line

  9. Mesh Size Effects on Fracture Toughness Estimation by Damage Model

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Shin Beom; Chang, Yoon Suk; Kim, Young Jin [School of Mechanical Engineering, Sungkyunkwan Univ., Suwon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2009-05-15

    The objective of this paper is to investigate mesh size effects on fracture toughness of SA508 carbon steel by damage model. To achieve this goal, a series of finite element analyses are carried out for CT (compact tension) and PCVN (pre-cracked V-notch) specimens. And Weibull stress model are adopted to derive toughness scale diagram. Finally, toughness scale diagram, which considered crack-tip mesh size effects, is derived from comparing estimated fracture toughness data between CT and PCVN specimens under -60 .deg. C and -80 .deg. C.

  10. A study on rate sensitivity of elasto-plastic fracture toughness of TRIP steel evaluated by a small punch test

    Directory of Open Access Journals (Sweden)

    Shi L.

    2012-08-01

    Full Text Available TRIP steel indicates an excellent characteristic in energy absorption because of its high ductility and strength by strain-induced martensitic transformation (SIMT. Recently, some shock absorption members are being used for automotive industries. For good fuel consumption of the automobile, it would realize the weight reduction without decaying performance if TRIP steel can be applied to those members. It can be considered that the fracture toughness is an important factor to evaluate the performance. To evaluate fracture toughness locally at any point of a product of those members, small punch testing method is quite effective. In the present study, first, an impact small punch testing apparatus is established. In addition, elasto-plastic fracture toughness of TRIP steel under impact loading and its rate sensitivity tested at various deflection rates are challenged to evaluate.

  11. Numerical study of the Notch Location of the Impact Test Specimens on the HAZ of SA516 Steels

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Yun Chan; Kim, Dong Wook; Lee, Young Seog [Chungang Univ., Seoul (Korea, Republic of); Hong, Jae Keun; Park, Ji Hong [Korea Institute of Machinery and Materials, Daejeon (Korea, Republic of)

    2007-07-01

    Experimental and numerical studies were performed to examine the effects of notch position on the failure behavior and energy absorption when the Charpy V-notch impact test is made at 1 .deg. C. For this purpose, carbon steel plate (SA-516 Gr. 70) with thickness of 25mm usually used for pressure vessel was welded by SMAW (Shielded Metal-Arc Welding) method and specimens were fabricated from the welded plate. The Charpy impact tests were then performed with specimens having different notch positions varying within HAZ. A series of three-dimensional FE analysis which simulates the Charpy test and crack propagation are carried out as well to examine the reproducibility of test results. The FE analysis takes into account the heterogeneous mechanical properties with complex microstructures in HAZ. Results reveal that the absorbed energies during impact test depend significantly on the notch position.

  12. Effect of Silicon Content on Carbide Precipitation and Low-Temperature Toughness of Pressure Vessel Steels

    Science.gov (United States)

    Ruan, L. H.; Wu, K. M.; Qiu, J. A.; Shirzadi, A. A.; Rodionova, I. G.

    2017-05-01

    Cr - Mn - Mo - Ni pressure vessel steels containing 0.54 and 1.55% Si are studied. Metallographic and fractographic analyses of the steels after tempering at 650 and 700°C are performed. The impact toughness at - 30°C and the hardness of the steels are determined. The mass fraction of the carbide phase in the steels is computed with the help of the J-MatPro 4.0 software.

  13. Cumulative Effect of Crumb Rubber and Steel Fiber on the Flexural Toughness of Concrete

    OpenAIRE

    B.H. Abu Bakar; Noaman, A. T.; Md. Akil, H.

    2017-01-01

    Concrete properties, such as toughness and ductility, are enhanced to resist different impacts or blast loads. Rubberized concrete, which could be considered a green material, is produced from recycled waste tires grinded into different crumb rubber particle sizes and mixed with concrete. In this study, the behavior of rubberized steel fiber-reinforced concrete is investigated. Flexural performance of concrete beams (400×100×100 mm) manufactured from plain, steel fiber, crumb rubber and combi...

  14. 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.

  15. The nature of mental toughness in sport | Fourie | South African ...

    African Journals Online (AJOL)

    This study investigated the components of mental toughness as reported by 131 expert coaches and 160 elite athletes from 31 sport codes. The written statements of coaches and athletes were analysed by means of an inductive content analysis. This resulted in the identification of 12 components of mental toughness.

  16. 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...

  17. 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.

  18. Definition of the minimum longitude of insert in the rebuilding of Charpy test tubes for surveillance and life extension of vessels in Mexico; Definicion de la longitud minima de inserto en la reconstitucion de probetas Charpy para vigilancia y extension de vida de vasijas en Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Romero C, J.; Hernandez C, R.; Rocamontes A, M., E-mail: jesus.romero@inin.gob.mx [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

    2011-11-15

    In the National Institute of Nuclear Research (Mexico) a welding system for the rebuilding of Charpy test tubes has been developed, automated, qualified and used for the surveillance of the mechanical properties (mainly embrittlement) of the vessel. This system uses the halves of the rehearsed Charpy test tubes of the surveillance capsules extracted of the reactors, to obtain, of a rehearsed test tube, two reconstituted test tubes. This rebuilding process is used so much in the surveillance program like in the potential extension of the operation license of the vessel. To the halves of Charpy test tubes that have been removed the deformed part by machine are called -insert- and in a very general way the rebuilding consists in weld with the welding process -Stud Welding- two metallic implants in the ends of the insert, to obtain a reconstituted test tube. The main characteristic of this welding are the achieved small dimensions, so much of the areas welded as of the areas affected by the heat. The applicable normative settles down that the minim longitude of the insert for the welding process by Stud Welding it should be of 18 mm, however according to the same normative this longitude can diminish if is demonstrated analytic or experimentally that the central volume of 1 cm{sup 3} in the insert is not affected. In this work the measurement of the temperature profiles to different distances of the welding interface is presented, defining an equation for the maximum temperatures reached in function of the distance, on the other hand the real longitude affected in the test tube by means of metallography is determined and this way the minimum longitude of the insert for this developed rebuilding system was determined. (Author)

  19. Influence of Anisotropic Microcracking Due to Swelling on the Fracture Toughness of a Clay-Bearing Sandstone

    Science.gov (United States)

    Tiennot, M.; Mertz, J.-D.; Bourgès, A.

    2017-11-01

    Flaking is a well-known pattern on rich clay stone. As swelling of clay minerals may induce crack propagation under fatigue, a fracture mechanics approach is proposed to investigate its impact on such decay pattern. A clay-bearing sandstone from the Thüringen region is studied because of the scaling effect observed at its surface when exposed to environmental conditions. Semi-circular bending specimens adapted to stone heritage studies are prepared and three configurations are tested, in order to measure toughness with respect to the bedding of this sandstone. Deformations are measured during relative humidity variations. They are measured anisotropic due to position and orientation of the clay phases within the stone. The influence of such natural dimensional variations on Young modulus and fracture toughness is studied. It appears that the induced damage is oriented and is the consequence of opening of the initial microcracks in the direction perpendicular to the maximum swelling. This damage induces an evolution of the fracture properties and behaviour. Toughness decreases as relative humidity increases depending on the orientation of the microcracking. Moreover, the toughness anisotropy of this sandstone appears during humidification. After several cycles of swelling, the microcracking induces an increase in toughness when notch is perpendicular to them. This may explain some stone deterioration patterns, as flakes subparallel to the stone surface.

  20. Acoustic emission for interlaminar toughness testing of CFRP: Evaluation of the crack growth due to burst analysis

    Czech Academy of Sciences Publication Activity Database

    Lissek, F.; Haegerb, A.; Knoblauch, V.; Hloch, Sergej; Pude, F.; Kaufeld, M.

    2018-01-01

    Roč. 136, č. 1 (2018), s. 55-62 ISSN 1359-8368 Institutional support: RVO:68145535 Keywords : DCB * interlaminar toughness testing * acoustic emission * CFRP * burst analysis Subject RIV: JQ - Machines ; Tools Impact factor: 4.727, year: 2016 http://www.sciencedirect.com/science/article/pii/S1359836817313720

  1. 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.

  2. Marine Structural Steel Toughness Data Bank. Volume 3

    Science.gov (United States)

    1991-08-28

    Headings: Break? Did specimen fracture completely? CODIc Critical COD CODi Initial COD CVN Energy Charpy V Energy Crack lgth Crack Length Curve Curve...BS5762 -Standard Year Test Temp CODIc degC mm -30 0.57 -30 0.68 -30 . 1.26 not rporw(continued) Main Stutua To n ssDta:an Material BS4360 Gr50D Page...Initial JI. . . .. ._I. . . Maximum 1, ]max * Tearing Modulus ......... Standard Method ~P S5762 -Standard Year_______________ Test Tcmp CODIc degC mm

  3. Marine Structural Steel Toughness Data Bank. Volume 2

    Science.gov (United States)

    1991-01-01

    CODIc Critical COD CODi Initial COD CVN Energy Charpy V Energy Crack lgth Crack Length Curve Curve Shape DT Energy Dynamic Tear Energy E Tensile...1987 Orten Test Temp CODi CODIc JI Jmax Tear Mod degF in in in-lb/in2 in-lb/n2 in-lb/in**2 L-T 72 0.0237 0.0361 3908 3895 L-T 72 0.0256 0.0329...Shape ............................ * Standard Method ...................... E813 Standard Y ........ ....... *Orten Test Temp CODi CODIc Ji Jmax Tear

  4. Marine Structural Steel Toughness Data Bank (Abridged Edition)

    Science.gov (United States)

    1990-08-31

    for Table Column Headings: Break? Did specimen fracture completely? CODIc Critical COD CODi Initial COD CVN Energy Charpy V Energy Crack lgth Crack...Standard Y ear ........ .................. * Onen Test Temp KQ CODi CODIc Curve 3l degF ksi*in**0.5 mils mils in-lb/in2 L-T -166...Standard Method .... BS5762 -Standard Year . Test Temp CODIc degC mm -30 0.57 -30 0.68 -30 11.26 (continued) -not reported

  5. Cumulative Effect of Crumb Rubber and Steel Fiber on the Flexural Toughness of Concrete

    Directory of Open Access Journals (Sweden)

    B. H. Abu Bakar

    2017-02-01

    Full Text Available Concrete properties, such as toughness and ductility, are enhanced to resist different impacts or blast loads. Rubberized concrete, which could be considered a green material, is produced from recycled waste tires grinded into different crumb rubber particle sizes and mixed with concrete. In this study, the behavior of rubberized steel fiber-reinforced concrete is investigated. Flexural performance of concrete beams (400×100×100 mm manufactured from plain, steel fiber, crumb rubber and combination crumb rubber and steel fiber are also evaluated. Similarly, concrete slabs (500×500×50 mm are also tested under flexural loading. Flexural performance of the SFRRC mixtures was significantly enhanced. The toughness and maximum deflection of specimens with rubber were considerably improved. Steel fiber/crumb rubber-reinforced concrete can be used for practical application, which requires further studies.

  6. The Use of Doublers in Delamination Toughness Testing

    Science.gov (United States)

    Reeder, James R.; Demarco, Kevin; Whitley, Karen S.

    2002-01-01

    In this paper, the data reduction equations for common delamination toughness tests are rederived for use with specimens which have bonded doublers. The common toughness tests considered here are the double cantilever beam (DCB) for mode I toughness; the end notch flexure (3ENF) and 4 point ENF (4ENF) for mode II toughness; and the mixed mode bending (MMB) test for testing under combined mode I and mode II loading. Because the addition of the doublers changes the bending stiffness of the specimens, these data reduction equations may need to be corrected. Doublers were added to the delamination test specimens to solve a premature failure problem. Delamination toughness is normally tested using a beam with an imbedded insert so that one end of the specimen is split into two arms. If the specimen is too thin, or if the toughness of the material is too high, an arm of the specimen may fail in bending before the delamination grows. When this occurs, the toughness of the material cannot be determined. To delay the bending failure so that delamination growth occurs, doubler plates were bonded to both top and bottom surfaces of the specimen. A doubler parameter, beta, which describes how much the use of doubler plates changed the ratio of full thickness to delaminated bending stiffnesses, was defined. When changes to the data reduction equations were required, the changes were minor when written in terms of the beta parameter. The doubler plate technique was demonstrated by measuring the mixed-mode fracture toughness of a carbon-carbon composite using test specimens which would otherwise have failed before delamination growth occurred. The doubler plate technique may solve several problems that can be encountered when testing delamination fracture toughness.

  7. 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).

  8. An overview of TOUGH-based geomechanics models

    Science.gov (United States)

    Rutqvist, Jonny

    2017-11-01

    After the initial development of the first TOUGH-based geomechanics model 15 years ago based on linking TOUGH2 multiphase flow simulator to the FLAC3D geomechanics simulator, at least 15 additional TOUGH-based geomechanics models have appeared in the literature. This development has been fueled by a growing demand and interest for modeling coupled multiphase flow and geomechanical processes related to a number of geoengineering applications, such as in geologic CO2 sequestration, enhanced geothermal systems, unconventional hydrocarbon production, and most recently, related to reservoir stimulation and injection-induced seismicity. This paper provides a brief overview of these TOUGH-based geomechanics models, focusing on some of the most frequently applied to a diverse set of problems associated with geomechanics and its couplings to hydraulic, thermal and chemical processes.

  9. Instant tough bonding of hydrogels for soft machines and electronics

    Science.gov (United States)

    Wirthl, Daniela; Pichler, Robert; Drack, Michael; Kettlguber, Gerald; Moser, Richard; Gerstmayr, Robert; Hartmann, Florian; Bradt, Elke; Kaltseis, Rainer; Siket, Christian M.; Schausberger, Stefan E.; Hild, Sabine; Bauer, Siegfried; Kaltenbrunner, Martin

    2017-01-01

    Introducing methods for instant tough bonding between hydrogels and antagonistic materials—from soft to hard—allows us to demonstrate elastic yet tough biomimetic devices and machines with a high level of complexity. Tough hydrogels strongly attach, within seconds, to plastics, elastomers, leather, bone, and metals, reaching unprecedented interfacial toughness exceeding 2000 J/m2. Healing of severed ionic hydrogel conductors becomes feasible and restores function instantly. Soft, transparent multilayered hybrids of elastomers and ionic hydrogels endure biaxial strain with more than 2000% increase in area, facilitating soft transducers, generators, and adaptive lenses. We demonstrate soft electronic devices, from stretchable batteries, self-powered compliant circuits, and autonomous electronic skin for triggered drug delivery. Our approach is applicable in rapid prototyping and in delicate environments inaccessible for extended curing and cross-linking. PMID:28691092

  10. Med Switch Not Always Best Choice with Tough Depression

    Science.gov (United States)

    ... Med Switch Not Always Best Choice With Tough Depression Adding an antipsychotic or a second antidepressant may ... may not be the best way to help depression patients who don't respond to the first ...

  11. Engineering of High-Toughness Carbon Nanotubes Hierarchically Laminated Composites

    Science.gov (United States)

    2012-01-27

    the design and manufacturing of high-toughness materials quite challenging. Review of the current achievements and failures in this field give strongest...reaching high values of strain, Young’s modulus, and ultimate strength, simultaneously, which makes the design and manufacturing of high-toughness...Sapelkin, A.V.; Shim, B. S.; Khomutov, G. B.; Kotov, N. A.; Sukhorukov, G. B.; Moehwald, H.; Skirtach, A. G. Carbon Nanotubes on Polymeric Microcapsules

  12. Fracture toughness of advanced ceramics at room temperature

    Science.gov (United States)

    Quinn, George D.; Salem, Jonathan; Bar-On, Isa; Cho, Kyu; Foley, Michael; Fang, HO

    1992-01-01

    Results of round-robin fracture toughness tests on advanced ceramics are reported. A gas-pressure silicon nitride and a zirconia-toughened alumina were tested using three test methods: indentation fracture, indentation strength, and single-edge precracked beam. The latter two methods have produced consistent results. The interpretation of fracture toughness test results for the zirconia alumina composite is shown to be complicated by R-curve and environmentally assisted crack growth phenomena.

  13. Residual stress state in pipe cut ring specimens for fracture toughness testing

    Energy Technology Data Exchange (ETDEWEB)

    Damjanovic, Darko [J.J. Strossmayer Univ. of Osijek, Slavonski Brod (Croatia). Mechanical Engineering Faculty; Kozak, Drazan [Zagreb Univ. (Croatia). Dept. for Mechanical Design; Marsoner, Stefan [Materials Center, Leoben (Austria).; Gubeljak, Nenad [Maribor Univ. (Slovenia). Chair of Mechanics

    2017-07-01

    Thin-walled pipes are not suitable for measuring fracture toughness parameters of vital importance because longitudinal crack failure is the most common failure mode in pipes. This is due to the impossibility to manufacture standard specimens for measuring fracture toughness, such as SENB or CT specimens, from the thin wall of the pipe. Previous works noticed this problem, but until now, a good and convenient solution has not been found or developed. To overcome this problem, very good alternative solution was proposed, the so-called pipe ring notched bend specimen (PRNB) [1-5]. Until now, only the idealized geometry PRNB specimen is analyzed, i. e., a specimen which is not cut out from an actual pipe but produced from steel plate. Based on that, residual stresses are neglected along with the imperfections in geometry (elliptical and eccentricity). The aim of this research is to estimate the residual stress state(s) in real pipes used in the boiler industry produced by hot rolling technique. These types of pipes are delivered only in normalized condition, but not stress relieved. Therefore, there are residual stresses present due to the manufacturing technique, but also due to uneven cooling after the production process. Within this paper, residual stresses are estimated by three methods: the incremental hole drilling method (IHMD), X-ray diffraction (XRD) and the splitting method (SM). Knowing the residual stress state in the ring specimen, it is possible to assess their impact on fracture toughness measured on the corresponding PRNB specimen(s).

  14. Interfacial toughening and consequent improvement in fracture toughness of carbon fiber reinforced epoxy resin composites: induced by diblock copolymers

    Directory of Open Access Journals (Sweden)

    X. D. Zhou

    2013-11-01

    Full Text Available Carbon fibers chemically grafted with hydroxyl-terminated diblock copolymer poly (n-butylacrylate-b-poly (glycidyl methacrylate (OH-PnBA-b-PGMA, were used as the reinforcement for epoxy composites. The multi-filament composite specimens were prepared and measured by dynamic mechanical analysis (DMA, to study the interfacial toughness of carbon fiber reinforced epoxy composites with the diblock copolymers. The loss modulus and loss factor peaks of β-relaxation indicated that composites with diblock copolymers could dissipate more energy at small strain and possess better interfacial toughness, whereas composites without the ductile block PnBA having the worse interfacial toughness. The glass transition temperature and the apparent activation energy calculated from the glass transition showed that the strong interfacial adhesion existed in the composites with diblock copolymers, corresponding with the value of interfacial shear strength. Therefore, a strengthening and toughening interfacial structure in carbon fiber/epoxy composites was achieved by introducing the diblock copolymer OH-PnBA-b-PGMA. The resulting impact toughness, characterized with an Izod impact tester, was better than that of composite without the ductile block PnBA.

  15. Studies on fracture toughness of dental ceramics.

    Science.gov (United States)

    Taira, M; Nomura, Y; Wakasa, K; Yamaki, M; Matsui, A

    1990-11-01

    One important mechanical property of dental ceramics is fracture toughness, KIC, which represents the serviceability in the oral cavity, such as the resistance to marginal fracture. KIC values of several dental ceramics, natural tooth enamel and industrial ceramics were examined by use of the indentation microfracture (IM) method. This technique was based on the series of radial cracks emanating from the corners of the Vickers indentation. It was observed that appropriate load levels should be selected on each specimen to induce radial/median cracks. For feldspatic dental porcelains, larger loads of 10, 20 and 30 kg were needed to determine their KIC values in the range 1.5-2.1 MN.m-3/2. For natural tooth enamel and a new apatite-based castable glass-ceramic, a smaller force of 1 kg was sufficient to decide the respective KIC values of about 0.9 and 1.8 MN.m-3/2. The KIC values of most dental ceramics examined were slightly higher than that of soda lime glass, but less than one-third that of zirconia. It was confirmed that the IM method is simple and cost-effective for evaluation of KIC of dental ceramics.

  16. Time-dependent fracture toughness of cornea.

    Science.gov (United States)

    Tonsomboon, Khaow; Koh, Ching Theng; Oyen, Michelle L

    2014-06-01

    The fracture and time-dependent properties of cornea are very important for the development of corneal scaffolds and prostheses. However, there has been no systematic study of cornea fracture; time-dependent behavior of cornea has never been investigated in a fracture context. In this work, fracture toughness of cornea was characterized by trouser tear tests, and time-dependent properties of cornea were examined by stress-relaxation and uniaxial tensile tests. Control experiments were performed on a photoelastic rubber sheet. Corneal fracture resistance was found to be strain-rate dependent, with values ranging from 3.39±0.57 to 5.40±0.48kJm(-2) over strain rates from 3 to 300mmmin(-1). Results from stress-relaxation tests confirmed that cornea is a nonlinear viscoelastic material. The cornea behaved closer to a viscous fluid at small strain but became relatively more elastic at larger strain. Although cornea properties are greatly dependent on time, the stress-strain responses of cornea were found to be insensitive to the strain rate when subjected to tensile loading. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. 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.

  18. 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.

  19. Motivational correlates of mentally tough behaviours in tennis.

    Science.gov (United States)

    Gucciardi, Daniel F; Jackson, Ben; Hanton, Sheldon; Reid, Machar

    2015-01-01

    The purpose of this study was to examine motivational correlates of mentally tough behaviours among adolescent tennis players. Two-phase study, involving the development of an informant-rated measure of mentally tough behaviours, followed by a cross-sectional survey including athlete and parent assessments of study variables. In Phase One, 17 adult, high-performance tennis coaches and 20 athletes participated in focus group interviews. Four scholars with expertise in performance psychology also completed a short, online survey. In Phase Two, a total of 347 adolescent tennis players (nmales=184; nfemales=163) aged 12-18 years (M=13.93, SD=1.47) and one respective parent took part in this study. An online multisection survey containing dimensions of passion, inspiration, fear of failure, and mentally tough behaviours was completed. Athletes self-reported all motivational variables, whereas parents rated their child solely on mentally tough behaviours. Structural equation modelling revealed that harmonious passion (β=.26, pintensity was not significantly associated with mentally tough behaviour (β=.13, p=.21). Motivational variables that are dispositional in nature, contextualised and contingent upon features of the environment, and concern one's identity are important considerations for understanding mentally tough behaviours. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

  20. Comparison of Heat Treatments on the Toughness of 1.7Ni-1.5Cu-0.5Mo Pre-alloyed P/M Steels

    Science.gov (United States)

    Güral, Ahmet; Türkan, Mustafa

    2015-05-01

    Effects of quenching plus tempering and intercritical annealing plus quenching heat treatments on the impact toughness properties of 1.7Ni-1.5Cu-0.5Mo pre-alloyed powder metallurgy steels with 0.2 (in mass%) graphite were investigated. Specimens were prepared by pressing at 670 MPa and sintering at 1250 °C. Different heat treatments, namely quenching and tempering, directly intercritically annealing and fully austenization plus intercritically annealing were carried out on the sintered specimens. The results showed that the impact toughness decreased with increasing intercritical annealing temperature in ferrite plus martensite dual phase powder metallurgy steels and with increasing tempering temperature in the quenched plus tempered specimens. Besides, impact toughness of fully austenizated plus intercritically annealed specimens was higher than those of quenched plus tempered and directly intercritically annealed specimens at the same hardness levels.

  1. Fracture toughness of two dentin adhesives.

    Science.gov (United States)

    Howard, Kimberly; Söderholm, Karl-Johan M

    2010-12-01

    Test the hypothesis that a self-etching adhesive is more likely to fail at the dentin-adhesive interface than an etch-and-rinse adhesive. Forty-eight composite-dentin short rod chevron-notched specimens were prepared. XP Bond and G Bond were used as adhesives. After 7 days in distilled water at 37°C, each specimen was tested (cross-head speed=0.05 mm/min). Fractured surfaces were inspected and characterized as interfacial failures, composite failures or a combination of interfacial and composite failures. The fracture toughness values (K(IC)) of the two adhesives were compared (Student's t-test and Weibull statistics). Of the specimens bonded with XP Bond, 50% failed at the dentin-adhesive interface, 42% at both the dentin-adhesive and composite interface and 8% in the composite alone. Of the specimens bonded with G Bond, 41% failed at the dentin-adhesive interface, 53% at both the dentin-adhesive and composite interface and 6% in the composite alone. The K(IC) values of the two adhesives differed significantly (pBond had a K(IC) of 0.77±0.11 MNm(-3/2) (n=17), while G Bond a K(IC) of 0.62±0.21 MNm(-3/2) (n=12). The high percentage of mixed failures did not support the hypothesis that the dentin-adhesive interface is clearly less resistant to fracture than the adhesive-composite interface. The finding that cracks occurred in 6-8% in the composite suggests that defects within the composite or at the adhesive-composite interface are important variables to consider in adhesion testing. Copyright © 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  2. Applicability of the Modified Ritchie-Knott-Rice Failure Criterion to Examine the Feasibility of Miniaturized Charpy Type SE(B Specimens

    Directory of Open Access Journals (Sweden)

    Toshiyuki Meshii

    2016-01-01

    Full Text Available This paper examined whether the modified Ritchie-Knott-Rice (RKR failure criterion can be applied to examine the feasibility of miniaturized Charpy type SE(B specimens of thickness-to-width ratio B/W=1. The modified RKR failure criterion considered in this paper is the (4δt,σ22c criterion which predicts the onset of cleavage fracture when the midplane crack-opening stress measured at a distance equal to four times the crack-tip opening displacement, denoted as σ22d, exceeds a critical stress σ22c. Specimens with B values of 25, 10, 3, and 2 mm (denoted as 25t, 10t, 3t, and 2t specimens, resp. manufactured with 0.55% carbon steel were tested at 20°C. The results showed that the modified RKR criterion could appropriately predict the occurrence of cleavage fracture accompanied by negligibly small stable crack extension (denoted as KJc fracture naturally for the 25t and 10t specimens. The modified RKR criterion could also predict that KJc fracture does not occur for the 2t specimen. The σ22c obtained from specimens for the 25t and 10t specimens exhibited only a small difference, indicating that the Jc obtained from the 10t specimens can be used to predict the Jc that will be obtained with the 25t specimens.

  3. 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.

  4. 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

  5. Pengaruh Penggunaan Serat Baja Terhadap Flexural Toughness Reactive Powder Concrete

    Directory of Open Access Journals (Sweden)

    Widodo Kushartomo

    2016-08-01

    Full Text Available This research present flexural toughness behavior of local steel fiber reinforced reactive powder concrete produced with different steel fibers volume fraction and aspect ratio. Prismatic concrete specimens of 100 x 100 x 350 mm were prepared with and without steel fiber. Steel fiber was used of 0% (control, 1,0%, 1,5%, and 2,0% by volume and 75, 100 and 125 as aspect ratio. Specimens were de-molded after 24 hours and cured in water until 3 days, after that the speciments were cure by steam curing for 8 hours at 90°C. Flexural toughness of the prisms has been defined at 28 day old. The result show that the effects of fibre volume and aspec ratio on flexural toughness of reactive powder concrete are very significant.

  6. 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.

  7. Effect of nanoscale patterned interfacial roughness on interfacial toughness.

    Energy Technology Data Exchange (ETDEWEB)

    Zimmerman, Jonathan A.; Moody, Neville Reid; Mook, William M. (University of Minnesota, Minneapolis, MN); Kennedy, Marian S. (Clemson University, Clemson, SC); Bahr, David F. (Washington State University, Pullman, WA); Zhou, Xiao Wang; Reedy, Earl David, Jr.

    2007-09-01

    The performance and the reliability of many devices are controlled by interfaces between thin films. In this study we investigated the use of patterned, nanoscale interfacial roughness as a way to increase the apparent interfacial toughness of brittle, thin-film material systems. The experimental portion of the study measured the interfacial toughness of a number of interfaces with nanoscale roughness. This included a silicon interface with a rectangular-toothed pattern of 60-nm wide by 90-nm deep channels fabricated using nanoimprint lithography techniques. Detailed finite element simulations were used to investigate the nature of interfacial crack growth when the interface is patterned. These simulations examined how geometric and material parameter choices affect the apparent toughness. Atomistic simulations were also performed with the aim of identifying possible modifications to the interfacial separation models currently used in nanoscale, finite element fracture analyses. The fundamental nature of atomistic traction separation for mixed mode loadings was investigated.

  8. 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.

  9. 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

  10. Tough love or bullying? New nurse transitional experiences.

    Science.gov (United States)

    Leong, Yee Mun Jessica; Crossman, Joanna

    2016-05-01

    This qualitative paper reports on the transition experiences of new nurses and preceptors in Singapore, focussing on the construction of a supervisor strategy termed 'tough love'. The authors discuss the concept of tough love, as a metaphorical euphemism for workplace bullying and interrogate rationales from the data that behaviours associated with tough love, prepare nurses for independence and competence in their new responsibilities. Successful transition of new nurses to professional practice is dependent on the transition challenges they face at work. When new nurses are well supported in the clinical environment, retention occurs. However, when workplace adversity intensifies, nurse turnover rates increase. This qualitative study was conducted using a constructivist grounded theory approach. New nurses (n = 26) and preceptors (n = 5) from five different hospitals participated in the study. Data were collected from semi-structured interviews and reflective journal entries and analysed using the constant comparative method. Data analysis gave rise to the generation of a definition of tough love, not otherwise identified in the literature, as the negative behaviours of senior nurses towards new nurses, that is rationalised as a well-intentioned but nevertheless abusive strategy, used to condition targets into conforming to expected professional or organisational behaviour. The authors conclude that tough love behaviour damages the transition experience of new nurses and has the potential to influence decisions on whether to remain in a health organisation and indeed the profession. Given nursing shortages in Singapore and internationally and that the retention of new nurses appears to be part of the problem, tough love behaviours and cultures clearly need to be addressed if investment into training and recruitment are to be realised. © 2016 John Wiley & Sons Ltd.

  11. 75 FR 72653 - Alternate Fracture Toughness Requirements for Protection Against Pressurized Thermal Shock Events...

    Science.gov (United States)

    2010-11-26

    ... RIN 3150-AI01 Alternate Fracture Toughness Requirements for Protection Against Pressurized Thermal... Regulations (10 CFR) part 50, section 61a to provide alternate fracture toughness requirements for protection...

  12. TAX-REFORM - DREAMING ABOUT TOUGH REALITIES

    NARCIS (Netherlands)

    DEKAM, F

    1992-01-01

    This paper discusses four papers concerned with tax reform. It is concluded that tax reform has had a rather limited impact on behaviour so far but that governments should press ahead with gradual improvement and not expect dramatic results.

  13. Theoretical and Experimental Investigation of Matrix Inclusions on the Fracture Toughness of Composite Material

    Science.gov (United States)

    Al Wakeel, Shahlaa A.

    This dissertation studies the impact of microstructure on macro-scale fracture parameters. Experimental and theoretical investigations of fracture toughness are carried out on a representative particulate composite material and reconciled by explicitly considering inclusions within the matrix. The reliability of any structure is a function of its resistance to fracture. Cracks resulting from stress concentrations are the major sources of fracture whether the material is classified as ductile, brittle, or quasi-brittle. The spatial distribution of inclusions in particulate composite materials, such as concrete and other heterogeneous materials, plays an important role in determining material fracture behavior due to the localized stress generated by the inclusion arrangement when cracks open. By controlling the spatial statistics of the inclusion microstructure in the matrix of a composite material, it is possible to control the amount or direction of crack development and may be possible to improve the material's reliability. As steps towards this goal this dissertation investigates the discrepancy between the micro-scratch and macro-scale three-point bending test methods due to the presence of matrix inclusions, applies the theoretical equations for fracture toughness which consider inclusions in the case of micro-particles in cement, and investigates how spatial statistic descriptions may be used to capture the impact of inclusions in a simple closed-form approach. The results of this work allow us to move towards a forward design method to design particulate composite micro-structures for improved resilience to local damage without fracturing.

  14. Characterization of the Multi-Pass Weld Metal and the Effect of Post-Weld Heat Treatment on Its Microstructure and Toughness

    Science.gov (United States)

    Wang, Xuelin; Shang, Chengjia; Wang, Xuemin

    In multi-pass welding process, various thermal cycle of both weld metal (WM) and heat affected zone (HAZ) will be subjected several times. This will make the initial microstructure occur an irreversible transformation. As the transformed microstructure become extremely complex, the mechanical properties, especially the low temperature toughness are very much fluctuant. In this research, the microstructure and low temperature toughness of WM obtained from a real multi-pass weld joint (up to 55 mm) by submerged arc welding have been elaborated. The results indicated that the necklace-type coarse martensite-austenite (M-A) constituent formed in interlayer heat affected zone (IHAZ) of WM and the impact energy of WM at -40 °C was only 39 J. Furthermore, by conventional tempering with holding time of 30 min, the toughness of WM can't be effectively improved. However, by a new developed heat treatment process, the toughness of WM could be significantly improved, and it is believed to be caused by the composition of weld metal and the post-welding heat treatment process. It also shows that the decomposition of M-A constituent and formation of the retained austenite are the mechanism of the improvement of low temperature toughness.

  15. 75 FR 10410 - Alternate Fracture Toughness Requirements for Protection Against Pressurized Thermal Shock Events...

    Science.gov (United States)

    2010-03-08

    ... COMMISSION 10 CFR Part 50 RIN 3150-AI01 Alternate Fracture Toughness Requirements for Protection Against... (75 FR 13), that amends the NRC's regulations to provide alternate fracture toughness requirements for... adding Table 7 directly after Table 6 to read as follows: Sec. 50.61a Alternate fracture toughness...

  16. Tough, semiconducting polyethylene-poly(3-hexylthiophene) diblock copolymers

    DEFF Research Database (Denmark)

    Müller, C.; Goffri, S.; Breiby, Dag Werner

    2007-01-01

    10(-2) cm(2)V(-1)s(-1) and ON-OFF ratios, I-on/I-off similar to 10(5) at contents of the insulating PE moiety as high as 90 wt %. In addition, the diblock copolymers display outstanding flexibility and toughness with elongations at break exceeding 600 % and true tensile strengths around 70 MPa...

  17. Correcting for nonlinear effects in fracture toughness testing.

    Science.gov (United States)

    Liebowitz, H.; Eftis, J.

    1972-01-01

    Expressions for fracture toughness, which include nonlinear effects due to crack front plastic yield and possible small crack extension prior to fracture instability, are obtained for several test specimen configurations. Inclusion of such effects is based on a simple compliance type determination of the total energy rate at onset of fast fracture.

  18. Tough and tunable adhesion of hydrogels: experiments and models

    Science.gov (United States)

    Zhang, Teng; Yuk, Hyunwoo; Lin, Shaoting; Parada, German A.; Zhao, Xuanhe

    2017-06-01

    As polymer networks infiltrated with water, hydrogels are major constituents of animal and plant bodies and have diverse engineering applications. While natural hydrogels can robustly adhere to other biological materials, such as bonding of tendons and cartilage on bones and adhesive plaques of mussels, it is challenging to achieve such tough adhesions between synthetic hydrogels and engineering materials. Recent experiments show that chemically anchoring long-chain polymer networks of tough synthetic hydrogels on solid surfaces create adhesions tougher than their natural counterparts, but the underlying mechanism has not been well understood. It is also challenging to tune systematically the adhesion of hydrogels on solids. Here, we provide a quantitative understanding of the mechanism for tough adhesions of hydrogels on solid materials via a combination of experiments, theory, and numerical simulations. Using a coupled cohesive-zone and Mullins-effect model validated by experiments, we reveal the interplays of intrinsic work of adhesion, interfacial strength, and energy dissipation in bulk hydrogels in order to achieve tough adhesions. We further show that hydrogel adhesion can be systematically tuned by tailoring the hydrogel geometry and silanization time of solid substrates, corresponding to the control of energy dissipation zone and intrinsic work of adhesion, respectively. The current work further provides a theoretical foundation for rational design of future biocompatible and underwater adhesives.

  19. On Measurement and Interpretation of Toughness Behaviour of Carbide Tools

    NARCIS (Netherlands)

    Kals, H.J.J.

    1981-01-01

    The actual significance of any definition of toughness behaviour of carbide tools depends on the existence of an interrelation between the quality as defined and the occurrence of chipping and premature failure in cutting. While at present there is no adequate analysis available and the existing

  20. Measuring the Real Fracture Toughness of Ceramics: ASTM C 1421

    Science.gov (United States)

    Salem, Jonathan; Quinn, George; Jenkins, Michael

    ASTM C 1421 "Standard Test Methods for Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperature" is a high-quality, technicallyrigorous, full-consensus standard that may have finally answered the question, "What is the 'real' fracture toughness of ceramics?" This document was eight years in the actual standardization process (although an estimated two decades of preparation work may have preceded the actual standardization process). Three different types of notch/crack geometries are employed in flexure beams: single edge precracked beam (SEPB); chevron-notched beam (CNB), and surface crack in flexure (SCF). Extensive experimental, analytical, and numerical evaluations were conducted in order to mitigate interferences that frequently lower the accuracy of fracture toughness test results. Several round robins (e.g. Versailles Advanced Materials and Standards {VAMAS}) verified and validated the choice of dimensions and test parameters included in the standard. In addition, the standard reference material NIST SRM 2100 was developed and can be used in concert with ASTM C 1421 to validate a fracture toughness test setup or test protocol.

  1. Bipartite Toughness and k-Factors in Bipartite Graphs

    Directory of Open Access Journals (Sweden)

    Guizhen Liu

    2008-01-01

    Full Text Available We define a new invariant tB(G in bipartite graphs that is analogous to the toughness t(G and we give sufficient conditions in term of tB(G for the existence of k-factors in bipartite graphs. We also show that these results are sharp.

  2. 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.

  3. Fracture toughness and reliability in high-temperature structural ...

    Indian Academy of Sciences (India)

    Unknown

    National Aeronautics and Space Administration, John Glenn Research Centre, Cleveland, Ohio 44135, USA. Abstract. 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.

  4. Photonics and fracture toughness of heterogeneous composite materials.

    Science.gov (United States)

    Antony, S Joseph; Okeke, George; Tokgoz, D Deniz; Ozerkan, N Gozde

    2017-07-03

    Fracture toughness measures the resistance of a material to fracture. This fundamental property is used in diverse engineering designs including mechanical, civil, materials, electronics and chemical engineering applications. In spite of the advancements made in the past 40 years, the evaluation of this remains challenging for extremely heterogeneous materials such as composite concretes. By taking advantage of the optical properties of a thin birefringent coating on the surface of opaque, notched composite concrete beams, here we sense the evolution of the maximum shear stress distribution on the beams under loading. The location of the maximum deviator stress is tracked ahead of the crack tip on the experimental concrete samples under the ultimate load, and hence the effective crack length is characterised. Using this, the fracture toughness of a number of heterogeneous composite beams is evaluated and the results compare favourably well with other conventional methods using combined experimental and numerical/analytical approaches. Finally a new model, correlating the optically measured shear stress concentration factor and flexural strength with the fracture toughness of concretes is proposed. The current photonics-based study could be vital in evaluating the fracture toughness of even opaque and complex heterogeneous materials more effectively in future.

  5. Fracture toughness and reliability in high-temperature structural ...

    Indian Academy of Sciences (India)

    The potential of these ceramics and ceramic matrix composites for high temperature applications in defence 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 ...

  6. On the in vitro fracture toughness of human dentin

    Energy Technology Data Exchange (ETDEWEB)

    Imbeni, V.; Nalla, R.K.; Bosi, C.; Kinney, J.H.; Ritchie, R.O.

    2002-02-05

    The in vitro fracture toughness of human dention has been reported to be of the order of 3 MPa sqrt m. This result, however is based on a single study for a single orientation, and furthermore involves notched, rather than fatigue precracked, test samples.

  7. Tough Times: Strategic Planning as a War Canoe

    Science.gov (United States)

    Seymour, Daniel

    2011-01-01

    In this article, the author discusses how to make strategic planning a more valuable tool for higher education in today's tough times. Strategic planning is really the answer to five straightforward questions. The first three represent the plan itself, while the last two are what makes the plan vital and dynamic: (1) Why do we exist?; (2) What do…

  8. 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.

  9. Raising Resilient Children during Tough Economic Times

    Science.gov (United States)

    Tom, A.; Yuen, S.; Fong, G.; Nemoto, M.; Hisatake, T.; Choy, A.; Chang, W.

    2009-01-01

    Financial hardship can result from many different circumstances--a poor economy, the loss of a job, underemployment, the prolonged illness of a family member, divorce, poor money management, or a combination of several factors. Whatever the cause, the resulting impact on a family can be stressful for all members, including children. Stress from…

  10. Control of Microstructures and the Practical Properties of API X80 Grade Heavy-Wall High-Frequency Electric Resistance-Welded Pipe with Excellent Low-Temperature Toughness

    Science.gov (United States)

    Goto, Sota; Nakata, Hiroshi; Toyoda, Shunsuke; Okabe, Takatoshi; Inoue, Tomohiro

    2017-10-01

    This paper describes development of heavy-walled API X80 grade high-frequency electric resistance-welded (HFW) line pipes and conductor-casing pipes with wall thicknesses up to 20.6 mm. A fine bainitic-ferrite microstructure, which is preferable for low-temperature toughness, was obtained by optimizing the carbon content and applying the thermomechanical controlled hot-rolling process. As a result, the Charpy ductile-brittle transition temperature (DBTT) was well below 227 K (-46 °C) in the base metal of the HFW line pipe. When the controlled hot-rolling ratio (CR) was increased from 23 to 48 pct, the area average grain size decreased from 15 to 8 μm. The dependence of CTOD properties on CR was caused by the largest grain which is represented by the area average grain size. No texture development due to the increase of CR from 23 to 48 pct was observed. In addition, because controlled in-line heat treatment of the longitudinal weld seam also produced the fine bainitic-ferrite microstructure at the weld seam, DBTT was lower than 227 K (-46 °C) at the weld portion. The developed pipes showed good girth weldability without preheat treatment, and fracture in the tensile test initiated from the base metal in all cases.

  11. AN INNOVATIVE TECHNIQUE FOR THIN FILM INTERFACE TOUGHNESS RESEARCH

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J.J.

    2004-11-01

    A material configuration of central importance in microelectronics, optoelectronics, and thermal barrier coating technology is a thin or thick film of one material deposited onto a substrate of a different material. Fabrication of such a structure inevitably gives rise to stress in the film due to lattice mismatch, differing coefficients of thermal expansion, chemical reactions, or other physical effects. Therefore, in general, the weakest link in this composite system often resides at the interface between the film and substrate. In order to make multi-layered electronic devices and structural composites with long-term reliability, the fracture behavior of the material interfaces must be known. Unfortunately, none of the state-of-the-art testing methods for evaluating interface fracture toughness is fully conformed to fracture mechanics theory, as is evident from the severe scatter in the existing data and the procedure dependence in film/coating evaluation methods. This project is intended to address the problems associated with this deficiency and offers an innovative testing procedure for the determination of interface fracture toughness applicable to coating materials in general. This new approach and the associated bi-material fracture mechanics development proposed for evaluating interface fracture toughness are described herein. The effort includes development of specimen configuration and related instrumentation set-up, testing procedures, postmortem examination, and analytical evaluation. A spiral notch torsion fracture toughness test system was utilized. The objective of the testing procedure described is to enable the development of new coating materials by providing a reliable method for use in assessing their performance. This innovative technology for measuring interface toughness was demonstrated for oxide scales formed on high-temperature alloys of MA956. The estimated energy release rate (in terms of J-integral) at the interface of the alumina

  12. Flexural Toughness of Ring-Shaped Waste Bottle Fiber Concrete

    Directory of Open Access Journals (Sweden)

    Faisal S. K.

    2016-01-01

    Full Text Available Polyethylene terephthalate (PET bottles are plastic containers that are typically discarded, and thus, cause environmental pollution. To solve this problem, PET bottles are recycled incorporating with concrete. A ring-shaped PET (RPET fiber are introduced in this study and designed with a special shape to mobilize fiber yielding rather than fiber pullout. Therefore, aim of this paper is to investigate the influence of RPET bottles fibre in terms of toughness strength. The width of RPET fibers is fixed at 5 and 10 mm and the loads were applied to the third points of the specimen. The experiment indicates that RPET-5 and RPET-10 FC presented an increase in the toughness index of I20 on averages of 23.1% and 39.9% respectively, compared to normal specimens. It can conclude that incorporating RPET fiber in concrete presents significant improved of concrete properties.

  13. 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.

  14. A portable fracture toughness tester for biological materials

    Science.gov (United States)

    Darvell, B. W.; Lee, P. K. D.; Yuen, T. D. B.; Lucas, P. W.

    1996-06-01

    A portable mechanical tester is described which is both lightweight and cheap to produce. The machine is simple and convenient to operate and requires only a minimum of personnel training. It can be used to measure the fundamental mechanical properties of pliant solids, particularly toughness (in the sense of `work of fracture') using either scissors or wedge tests. This is achieved through a novel hardware integration technique. The circuits are described. The use of the machine does not require a chart recorder but it can be linked to a personal computer, either to show force - displacement relationships or for data storage. The design allows the use of any relatively `soft' mechanical test, i.e. tests in which the deformability of the frame of the machine and its load cell do not introduce significant errors into the results. Examples of its use in measuring the toughness of biomaterials by scissors (paper, wood) and wedges (mung bean starch gels) are given.

  15. Cryogenic properties of a new tough-strong iron alloy

    Science.gov (United States)

    Stephens, J. R.; Witzke, W. R.

    1977-01-01

    A program was undertaken to develop an iron-base alloy having a fracture toughness of 220 MPa-sq root meters with a corresponding yield stress of 1.4 GPa (200 ksi) at -196 C. An Fe-12Ni alloy was selected as the base alloy. Factors considered include reactive metal additions, effects of interstitial impurities, strengthening mechanisms, and weldability. The goals of this program were met in an Fe-12Ni-0.5Al alloy strengthened by thermomechanical processing or by precipitate strengthening with 2 percent Cu. The alloy is weldable with the weld metal and heat affected zone in the post-weld annealed condition having toughness equivalent to the base alloy.

  16. Mental Toughness in Competitive Tennis: Relationships with Resilience and Stress

    Directory of Open Access Journals (Sweden)

    Richard Gregory Cowden

    2016-03-01

    Full Text Available The present study investigated the relationships between mental toughness (MT, resilience, and stress among competitive South African tennis players. A total of 351 tennis players participating at various competitive standards completed the Sport Mental Toughness Questionnaire, the Resilience Scale for Adults, and a modified version of the Recovery-Stress Questionnaire for Athletes. The results indicated that total MT was positively associated with total resilience (r = .59, but negatively associated with total stress (r = -.44. The resilience subscales of perception of self, perception of future, social competence, and social resources, but not family cohesion, significantly predicted total MT (R2 = .35. Both total resilience and total MT significantly predicted total stress (R2 = .21. Based on the findings, interrelations between MT and resilience are explored, implications outlined, and additional research is suggested to ascertain the contextual relevance and outcomes associated with each construct in sport.

  17. Study of fracture toughness of ZrO2 ceramics

    Science.gov (United States)

    Deryugin, Yevgeny; Narkevich, Natalya; Vlasov, Ilya; Panin, Victor; Danilenko, Igor; Schmauder, Siegfried

    2017-12-01

    The fracture toughness characteristics of ZrO2ceramics were determined experimentally using an original technique of wedging small-sized chevron notch specimens developed at the Institute of Strength Physics and Materials Science SB RAS (Russia) in the laboratory of physical mesomechanics of materials and non-destructive testing. Measurements have shown that inelastic displacements can be more than 22% of the total displacement of the consoles by the time of the specimen failure. The effect of the Y2O3 stabilizer on the critical stress intensity factor KIc was verified. It was shown that an increase in the Y2O3 stabilizer content from 3 to 8% significantly decreases the fracture toughness. The stress intensity factor KIc falls within the range from 5.7 to 2.35 MPa m1/2.

  18. Non-local plasticity effects on fracture toughness

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof

    2002-01-01

    of the effective plastic strain. Fracture is modelled by a cohesive zone criterion. Results on the numerically obtained stress fields are presented, as well as results on the steady-state fracture toughness. It is shown that the nonlocal theory predicts lower steady-state fracture toughness compared to predictions...... by conventional J2-flow theory, since higher normal stresses in front of the crack tip are predicted. Furthermore, the nonlocal material description increases the range of applicability of the cohesive zone model, since steady-state crack growth is possible for significantly larger values of the maximum stress......The Mode I fracture strength in a nonlocal elastic-plastic material is analyzed under quasi-static steady crack growth. The plastic deformations are modelled using a constitutive model, where nonlocal plasticity effects are included in the instantaneous hardening moduli through a gradient measure...

  19. Enhancements in Magnesium Die Casting Impact Properties

    Energy Technology Data Exchange (ETDEWEB)

    David Schwam; John F. Wallace; Yulong Zhu; Srinath Viswanathan; Shafik Iskander

    2000-06-30

    The need to produce lighter components in transportation equipment is the main driver in the increasing demand for magnesium castings. In many automotive applications, components can be made of magnesium or aluminum. While being lighter, often times the magnesium parts have lower impact and fatigue properties than the aluminum. The main objective of this study was to identify potential improvements in the impact resistance of magnesium alloys. The most common magnesium alloys in automotive applications are AZ91D, AM50 and AM60. Accordingly, these alloys were selected as the main candidates for the study. Experimental quantities of these alloys were melted in an electrical furnace under a protective atmosphere comprising sulfur hexafluoride, carbon dioxide and dry air. The alloys were cast both in a permanent mold and in a UBE 315 Ton squeeze caster. Extensive evaluation of tensile, impact and fatigue properties was conducted at CWRU on permanent mold and squeeze cast test bars of AZ91, AM60 and AM50. Ultimate tensile strength values between 20ksi and 30ksi were obtained. The respective elongations varied between 25 and 115. the Charpy V-notch impact strength varied between 1.6 ft-lb and 5 ft-lb depending on the alloy and processing conditions. Preliminary bending fatigue evaluation indicates a fatigue limit of 11-12 ksi for AM50 and AM60. This is about 0.4 of the UTS, typical for these alloys. The microstructures of the cast specimens were investigated with optical and scanning electron microscopy. Concomitantly, a study of the fracture toughness in AM60 was conducted at ORNL as part of the study. The results are in line with values published in the literature and are representative of current state of the art in casting magnesium alloys. The experimental results confirm the strong relationship between aluminum content of the alloys and the mechanical properties, in particular the impact strength and the elongation. As the aluminum content increases from about 5

  20. Flexural Toughness of Ring-Shaped Waste Bottle Fiber Concrete

    OpenAIRE

    Faisal S. K.; Irwan J.M; Othman N.; Wan Ibrahim M. H.

    2016-01-01

    Polyethylene terephthalate (PET) bottles are plastic containers that are typically discarded, and thus, cause environmental pollution. To solve this problem, PET bottles are recycled incorporating with concrete. A ring-shaped PET (RPET) fiber are introduced in this study and designed with a special shape to mobilize fiber yielding rather than fiber pullout. Therefore, aim of this paper is to investigate the influence of RPET bottles fibre in terms of toughness strength. The width of RPET fibe...

  1. Mental Health staff views on improving burnout and mental toughness

    OpenAIRE

    Posner, Zoe; Janssen, Jessica; Roddam, Hazel

    2017-01-01

    Purpose- Burnout in mental health staff is acknowledged as a major problem. The purpose of this paper is to gain an understanding of mental health staff views on improving burnout and mental toughness in mental health staff.\\ud Design/methodology/approach-Ten participants from two mental health rehabilitation units across the North West of England took part in a Nominal Group Technique (NGT). Participants consisted of mental health workers from varied roles in order to\\ud capture views from a...

  2. Strength and toughness of structural fibres for composite material reinforcement.

    Science.gov (United States)

    Herráez, M; Fernández, A; Lopes, C S; González, C

    2016-07-13

    The characterization of the strength and fracture toughness of three common structural fibres, E-glass, AS4 carbon and Kevlar KM2, is presented in this work. The notched specimens were prepared by means of selective carving of individual fibres by means of the focused ion beam. A straight-fronted edge notch was introduced in a plane perpendicular to the fibre axis, with the relative notch depth being a0/D≈0.1 and the notch radius at the tip approximately 50 nm. The selection of the appropriate beam current during milling operations was performed to avoid to as much as possible any microstructural changes owing to ion impingement. Both notched and un-notched fibres were submitted to uniaxial tensile tests up to failure. The strength of the un-notched fibres was characterized in terms of the Weibull statistics, whereas the residual strength of the notched fibres was used to determine their apparent toughness. To this end, the stress intensity factor of a fronted edge crack was computed by means of the finite-element method for different crack lengths. The experimental results agreed with those reported in the literature for polyacrylonitrile-based carbon fibres obtained by using similar techniques. After mechanical testing, the fracture surface of the fibres was analysed to ascertain the failure mechanisms. It was found that AS4 carbon and E-glass fibres presented the lower toughness with fracture surfaces perpendicular to the fibre axis, emanating from the notch tip. The fractured region of Kevlar KM2 fibres extended along the fibre and showed large permanent deformation, which explains their higher degree of toughness when compared with carbon and glass fibres. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'. © 2016 The Author(s).

  3. Enzymatic mineralization generates ultrastiff and tough hydrogels with tunable mechanics

    Science.gov (United States)

    Rauner, Nicolas; Meuris, Monika; Zoric, Mirjana; Tiller, Joerg C.

    2017-03-01

    The cartilage and skin of animals, which are made up of more than fifty per cent water, are rather stiff (having elastic moduli of up to 100 megapascals) as well as tough and hard to break (with fracture energies of up to 9,000 joules per square metre). Such features make these biological materials mechanically superior to existing synthetic hydrogels. Lately, progress has been made in synthesizing tough hydrogels, with double-network hydrogels achieving the toughness of skin and inorganic-organic composites showing even better performance. However, these materials owe their toughness to high stretchability; in terms of stiffness, synthetic hydrogels cannot compete with their natural counterparts, with the best examples having elastic moduli of just 10 megapascals or less. Previously, we described the enzyme-induced precipitation and crystallization of hydrogels containing calcium carbonate, but the resulting materials were brittle. Here we report the enzyme-induced formation of amorphous calcium phosphate nanostructures that are homogenously distributed within polymer hydrogels. Our best materials have fracture energies of 1,300 joules per square metre even in their fully water-swollen state—a value superior to that of most known water-swollen synthetic materials. We are also able to modulate their stiffness up to 440 megapascals, well beyond that of cartilage and skin. Furthermore, the highly filled composite materials can be designed to be optically transparent and to retain most of their stretchability even when notched. We show that percolation drives the mechanical properties, particularly the high stiffness, of our uniformly mineralized hydrogels.

  4. Enzymatic mineralization generates ultrastiff and tough hydrogels with tunable mechanics.

    Science.gov (United States)

    Rauner, Nicolas; Meuris, Monika; Zoric, Mirjana; Tiller, Joerg C

    2017-03-16

    The cartilage and skin of animals, which are made up of more than fifty per cent water, are rather stiff (having elastic moduli of up to 100 megapascals) as well as tough and hard to break (with fracture energies of up to 9,000 joules per square metre). Such features make these biological materials mechanically superior to existing synthetic hydrogels. Lately, progress has been made in synthesizing tough hydrogels, with double-network hydrogels achieving the toughness of skin and inorganic-organic composites showing even better performance. However, these materials owe their toughness to high stretchability; in terms of stiffness, synthetic hydrogels cannot compete with their natural counterparts, with the best examples having elastic moduli of just 10 megapascals or less. Previously, we described the enzyme-induced precipitation and crystallization of hydrogels containing calcium carbonate, but the resulting materials were brittle. Here we report the enzyme-induced formation of amorphous calcium phosphate nanostructures that are homogenously distributed within polymer hydrogels. Our best materials have fracture energies of 1,300 joules per square metre even in their fully water-swollen state-a value superior to that of most known water-swollen synthetic materials. We are also able to modulate their stiffness up to 440 megapascals, well beyond that of cartilage and skin. Furthermore, the highly filled composite materials can be designed to be optically transparent and to retain most of their stretchability even when notched. We show that percolation drives the mechanical properties, particularly the high stiffness, of our uniformly mineralized hydrogels.

  5. Novel PM Tool Steel with improved hardness and toughness

    OpenAIRE

    Deirmina, Faraz

    2017-01-01

    Ultrafine grained (~ 1μm) steels have been the subject of extensive research work during the past years. These steels generally offer interesting perspectives looking for improved mechanical properties. UFG Powder Metallurgy hot work tool steels (HWTS) can be fabricated by high energy mechanical milling (MM) followed by spark plasma sintering (SPS). However, similarly to most UFG and Nano-Crystalline (NC) metals, reduced ductility and toughness result from the early plastic instabilities in t...

  6. Effects of spatial heterogeneity and material anisotropy on the fracture pattern and macroscopic effective toughness of Mancos Shale in Brazilian tests

    Science.gov (United States)

    Na, SeonHong; Sun, WaiChing; Ingraham, Mathew D.; Yoon, Hongkyu

    2017-08-01

    For assessing energy-related activities in the subsurface, it is important to investigate the impact of the spatial variability and anisotropy on the geomechanical behavior of shale. The Brazilian test, an indirect tensile-splitting method, is performed in this work, and the evolution of strain field is obtained using digital image correlation. Experimental results show the significant impact of local heterogeneity and lamination on the crack pattern characteristics. For numerical simulations, a phase field method is used to simulate the brittle fracture behavior under various Brazilian test conditions. In this study, shale is assumed to consist of two constituents including the stiff and soft layers to which the same toughness but different elastic moduli are assigned. Microstructural heterogeneity is simplified to represent mesoscale (e.g., millimeter scale) features such as layer orientation, thickness, volume fraction, and defects. The effect of these structural attributes on the onset, propagation, and coalescence of cracks is explored. The simulation results show that spatial heterogeneity and material anisotropy highly affect crack patterns and effective fracture toughness, and the elastic contrast of two constituents significantly alters the effective toughness. However, the complex crack patterns observed in the experiments cannot completely be accounted for by either an isotropic or transversely isotropic effective medium approach. This implies that cracks developed in the layered system may coalesce in complicated ways depending on the local heterogeneity, and the interaction mechanisms between the cracks using two-constituent systems may explain the wide range of effective toughness of shale reported in the literature.

  7. 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.

  8. 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.

  9. 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.

  10. Stainless steel submerged arc weld fusion line toughness

    Energy Technology Data Exchange (ETDEWEB)

    Rosenfield, A.R.; Held, P.R.; Wilkowski, G.M. [Battelle, Columbus, OH (United States)

    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.

  11. Characterization of fracture toughness of epoxy resin after hygrothermal aging

    KAUST Repository

    Quispe, Gustavo Q.

    2013-07-01

    Characterization of fracture toughness of epoxy resin after hygrothermal ageing Gustavo Quino Quispe The aim of this work is to characterize the e ects of hygrothermal aging in the plain strain fracture toughness of the epoxy system composed by cycloaliphatic epoxy resin and diglycidyl ether of bisphenol-A (DGEBA). For this, after having been under hygrothermal aging in a climatic chamber, epoxy samples were studied using ASTM D5045 fracture toughness test, and micrography and roughness measurements of the fracture surface. It is reported a rapid decrease of GIc and KIc during the rst 2 days. Moreover, a numerical model [13] was used to simulate and see with more detail the water absorption in the aged samples. From that, it was observed the heterogeneous distribution of water. Accordingly, it was proposed that the results should be correlated with the water content at the vicinity of the crack tip. Consequently, it was possible to obtain, by quasi-static simulations, the ideal load-displacement curves of crack propagation in the heterogeneous samples. Finally, another contribution of this work is the study of the fracture surface, that gives a clue of the relationship among the fracture energy, the appearance of microcracks in the fracture surface, and the roughness (Ra).

  12. Immunosuppression – tough ally in torrid time

    Directory of Open Access Journals (Sweden)

    Elżbieta Ograczyk

    2015-12-01

    Full Text Available Immunosuppression is a condition characterized by weakened or inhibited immune response. It occurred both in humoral and cellular response. This is related to the variable levels of deficiency for each antibody class (IgG, IgM, IgA and a decrease in the number and function of immune cells, mainly T cells which results in the inhibition of cytokine production, signaling transduction and clonal expansion. Immunosuppressive therapy is used in many fields of medicine, such as transplantology, oncology, autoimmune disorders. Immunosuppression can be induced in several ways, by the surgical resection of the organs of the immune system, physical methods using X-rays or chemical methods using pharmacological agents. The most common way to induce immunosuppression is the administration of immunosuppressive drugs, amongst others: glucocorticoids, cytostatic drugs, immunophilin-binding agents, monoclonal antibodies. Unfortunately, the desired therapeutic effects of immunosuppression may be accompanied by a number of side effects associated with both impaired immunity (susceptibility to infections, including those caused by opportunistic microorganisms, toxic effects on the tissues (nephrotoxicity, neurotoxicity, or with a direct impact on the processes of malignancy. This harmful influence can be limited by the modification of the existing drugs, looking for new ones or developing new methods for the controlled kinetics of releasing the immunosuppressive pharmaceuticals. The personalization of immunosuppressant treatment according to genetic/genomic characteristics of individual patient represents the quite innovative look into the issue of immunosuppression.

  13. 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

  14. Mechanisms of Strength and Toughness in a Microalloyed, Precipitation Hardened Steel

    Science.gov (United States)

    1989-04-01

    interactions were studied using transmission electron microscopy of thin films made from the ends of Charpy V-notch specimens. Figures 81 and 82 show...aluminum and vanadium, which form nitrides of limited solubility, niobium, which forms a carbonitride , and titanium which forms both a carbide and a...high 16 carbon content or the carbon can be replaced by the sum of the carbon and nitrogen contents C10]. Silicon and phosphorous have been found to

  15. Mechanical Behavior of Tough Hydrogels for Structural Applications

    Science.gov (United States)

    Illeperuma, Widusha Ruwangi Kaushalya

    Hydrogels are widely used in many commercial products including Jell-O, contact lenses, and superabsorbent diapers. In recent decades, hydrogels have been under intense development for biomedical applications, such as scaffolds in tissue engineering, carriers for drug delivery, and valves in microfluidic systems. But the scope is severely limited as conventional hydrogels are weak and brittle and are not very stretchable. This thesis investigates the approaches that enhance the mechanical properties of hydrogels and their structural applications. We discov¬ered a class of exceptionally stretchable and tough hydrogels made from poly-mers that form networks via ionic and covalent crosslinks. Although such a hydrogel contains ~90% water, it can be stretched beyond 20 times its initial length, and has a fracture energy of ~9000 J/m2. The combination of large stretchability, remarkable toughness, and recoverability of stiffness and toughness, along with easy synthesis makes this material much superior over existing hydrogels. Extreme stretchability and blunted crack tips of these hydrogels question the validity of traditional fracture testing methods. We re-examine a widely used pure shear test method to measure the fracture energy. With the experimental and simulation results, we conclude that the pure shear test method can be used to measure fracture energy of extremely stretchable materials. Even though polyacrylamide-alginate hydrogels have an extremely high toughness, it has a relatively low stiffness and strength. We improved the stiffness and strength by embedding fibers. Most hydrogels are brittle, allowing the fibers to cut through the hydrogel when the composite is loaded. But tough hydrogel composites do not fail by the fibers cutting the hydrogel; instead, it undergoes large deforming by fibers sliding through the matrix. Hydrogels were not considered as materials for structural applications. But with enhanced mechanical properties, they have opened up

  16. Standard test methods for notched bar impact testing of metallic materials

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2007-01-01

    1.1 These test methods describe notched-bar impact testing of metallic materials by the Charpy (simple-beam) test and the Izod (cantilever-beam) test. They give the requirements for: test specimens, test procedures, test reports, test machines (see Annex A1) verifying Charpy impact machines (see Annex A2), optional test specimen configurations (see Annex A3), precracking Charpy V-notch specimens (see Annex A4), designation of test specimen orientation (see Annex A5), and determining the percent of shear fracture on the surface of broken impact specimens (see Annex A6). In addition, information is provided on the significance of notched-bar impact testing (see Appendix X2), methods of measuring the center of strike (see Appendix X2). 1.2 These test methods do not address the problems associated with impact testing at temperatures below -196 C (-320 F, 77 K). 1.3 The values stated in SI units are to be regarded as the standard. Inch-pound units are provided for information only. This standard does not purpor...

  17. Optimum Design and Development of High Strength and Toughness Welding Wire for Pipeline Steel

    Science.gov (United States)

    Chen, Cuixin; Xue, Haitao; Yin, Fuxing; Peng, Huifen; Zhi, Lei; Wang, Sixu

    Pipeline steel with higher strength(>800MPa) has been gradually used in recent years, so how to achieve good match of base metal and weld deposit is very important for its practical application. Based on the alloy system of 0.02-0.04%C, 2.0%Mn and 0.5%Si, four different kinds of welding wires were designed and produced. The effects of alloy elements on phase transformation and mechanical properties were analyzed. Experimental results show that the designed steels with the addition of 2-4% Ni+Cr+Mo and 800MPa) and good elongation (>15%). The microstructure of deposits metal is mainly composed of granular bainite and M-A constituents with the mean size of 0.2-07μm are dispersed on ferritic matrix. The deposited metals have good match of strength (>800MPa) and impact toughness (>130J) which well meet the requirement of pipeline welding.

  18. 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.

  19. Fracture toughness and leaching behavior of ion bombarded waste glasses

    Science.gov (United States)

    Matzke, Hj.; Linker, G.

    1984-02-01

    Fracture toughness Klc and fracture surface energy γ were measured on borosilicate waste glasses containing simulated fission products produced in the Institut für Nukleare Entsorgung, KFK. The Hertzian indentation technique with spherical indenters was shown to be a very powerful means with which to study mechanical and fracture properties of small highly radioactive samples. It was tested with Pu-ceramics as well as with Cm-doped glass ceramics. Radiation damage was produced by ion bombardment with Pb or Xe ions of energies up to 300 keV or with He 2+-ions (α-particles) of the cyclotron (KFK) with energies up to 77 MeV. The glasses were used either as-received or else following high-temperature, high-pressure autoclave leaching. The as-bombarded and the leached glasses were analyzed for surface composition and changes by Rutherford backscattering, RBS, with He-ions. In many cases, radiation damage caused an increase in fracture toughness, a very beneficial effect. The leached glasses that were investigated contained surface layers with thicknesses of up to ˜2 μm. RBS showed these layers to be similar in composition to thick layers analyzed by electron microprobe analysis (empa). There was no drastic influence of ion bombardment on the composition or thickness of these layers. The layers themselves caused changes of about ± 10% in the apparent fracture toughness, possibly by absorbing part of the applied energy by plastic deformation or by preventing pre-existing flaws from initiating crack formation.

  20. Effects of the phase fractions on the carbide morphologies, Charpy and tensile properties in SA508 Gr.4N High Strength Low Alloy RPV Steel

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang Gyu; Wee, Dang Moon [KAIST, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2011-05-15

    To improve the strength and toughness of RPV (reactor pressure vessel) steels for nuclear power plants, an effective way is the change of material specification from tempered bainitic SA508 Gr.3 Mn-Mo-Ni low alloy steel into tempered martensitic/bainitic SA508 Gr.4N Ni-Cr-Mo low alloy steel. It is known that the phase fractions of martensitic/bainitic steels are very sensitive to the austenitizing cooling rates. Kim reported that there are large differences of austenitizing cooling rates between the surface and the center locations in RPV due to its thickness of 250mm. Hence, the martensite/bainite fractions would be changed in different locations, and it would affect the microstructure and mechanical properties in Ni-Cr-Mo low alloy steel. These results may lead to inhomogeneous characteristics after austenitizing. Therefore, it is necessary to evaluate the changes of microstructure and mechanical properties with varying phase fractions in Ni-Cr-Mo low alloy steel. In this study, the effects of martensite/bainite fractions on microstructure and mechanical properties in Ni-Cr-Mo low alloy steel were examined. The changes in phase fractions of Ni-Cr-Mo low alloy steel with different cooling rates were analyzed, and then the phase fractions were correlated with its microstructural observation and mechanical properties

  1. How libraries make tough choices in difficult times purposeful abandonment

    CERN Document Server

    Stern, David

    2013-01-01

    Contemporary library managers face the need to make difficult choices regarding resource allocation in the modern business environment. How Libraries Make Tough Choices in Difficult Times is a practical guide for library managers, offering techniques to analyze existing and potential services, implement best practices for maximizing existing resources, and utilize pressing financial scenarios in order to justify making difficult reallocation decisions. The book begins by asking the fundamental questions of why, what, and how, moving on to look at how to manage expectations and report to both a

  2. Improvement of toughness and water resistance of bioplastic based on wheat gluten using epoxidized natural rubber

    Science.gov (United States)

    Hemsri, S.; Thongpin, C.; Somkid, P.; Sae-arma, S.; Paiykaew, A.

    2015-07-01

    Novel blends based on wheat gluten (WG) and epoxidized natural rubber (ENR) were fabricated with different ENR contents of 10, 20 and 30 wt% in an internal mixer. Sulfur vulcanization was used to crosslink the ENR phase in the blends. Comparatively, blends of WG and natural rubber (WG/NR) were prepared in the same condition as the WG/ENR blends. Tensile mechanical properties and impact strength of the WG/ENR blends were investigated and compared with the WG/NR blends as well as pure WG. Moreover, water absorption of pure WG and the WG/ENR blends was also tested. As investigated by scanning electron microscopy (SEM), the results revealed more compatibility between WG and ENR compared with NR. The elongation at break, impact strength and water resistance of the WG/ENR blends were found to remarkably increase with respect to the pure WG. Thus, incorporation of ENR into WG could improve toughness and water resistance of WG. Furthermore, the effect of adding glycerol acting as a plasticizer on the mechanical properties and impact strength of the WG/ENR blends was also studied. The blends with glycerol-plasticized WG (WG-Gly/ENR) showed more homogeneous morphologies and superior results in the mechanical properties and impact strength compared with the WG/ENR blends.

  3. Failure Behaviors Depending on the Notch Location of the Impact Test Specimens on the HAZ

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Yun Chan; Kim, Dong Wook; Lee, Young Suk [Chungang Univ., Seoul (Korea, Republic of); Hong, Jae Keun; Park, Ji Hong [Korea Institute of Machinery and Materials, Daejeon (Korea, Republic of)

    2007-07-01

    Numerical studies were performed to examine the effects of notch location of impact specimens on the failure behavior of HAZ (Heat Affected Zone) when Charpy V-notch impact test were made at a low temperature (1 .deg. C). Carbon steel plate (SA-516 Gr. 70) with thickness of 25mm for pressure vessel was welded by SMAW (Shielded Metal-Arc Welding) and specimens were fabricated from the welded plate. Charpy tests were then performed with specimens having different notch positions of specimens varying from the fusion line through HAZ to base metal. A series of finite element analysis which simulates the Charpy test and crack propagation initiating at the tip of V-notch was carried out as well. The finite element analysis takes into account the irregular fusion line and non-homogenous material properties due to the notch location of the specimen in HAZ. Results reveals that the energies absorbed during impact test depend significantly on the notch location and direction of specimen. Finite element analysis also demonstrates that the notch location of specimens, to a great extent, influences the reliability and consistency of the test.

  4. Fracture toughness estimation of ballast stone used in Iranian railway

    Directory of Open Access Journals (Sweden)

    I. Ferestade

    2017-10-01

    Full Text Available Ballast is a layer composed of crushed stone basically with diameters of 20–60 mm, on which sleepers and rails are set. Ballast is used to withstand vertical, horizontal and lateral forces applied on sleepers and to hold the line in operative conditions. Ballast deterioration induced by crashed stones is a major issue of track instability as the ballast layer quality depending on the materials used and their densities should be focused on. Therefore, ballast should be resistant against loads applied, and the fracture toughness of ballast stone is of great importance. For this purpose, the fracture toughness of two kinds of ballast stones used in Iranian railway, i.e. Gaduk (limestone and Anjylavnd (andesite, is investigated experimentally in this paper. The quality of ballast stone is evaluated in different weather conditions. Numerical results shown that the Anjylavnd stone is more appropriate for rainy and cold weather when there is a probability of fracturing due to frozen water captured in ballast.

  5. Microscopic assessment of bone toughness using scratch tests

    Directory of Open Access Journals (Sweden)

    Amrita Kataruka

    2017-06-01

    Full Text Available Bone is a composite material with five distinct structural levels: collagen molecules, mineralized collagen fibrils, lamellae, osteon and whole bone. However, most fracture testing methods have been limited to the macroscopic scale and there is a need for advanced characterization methods to assess toughness at the osteon level and below. The goal of this investigation is to present a novel framework to measure the fracture properties of bone at the microscopic scale using scratch testing. A rigorous experimental protocol is articulated and applied to examine cortical bone specimens from porcine femurs. The observed fracture behavior is very complex: we observe a strong anisotropy of the response with toughening mechanisms and a competition between plastic flow and brittle fracture. The challenge consists then in applying nonlinear fracture mechanics methods such as the J-integral or the energetic Size Effect Law to quantify the fracture toughness in a rigorous fashion. Our result suggests that mixed-mode fracture is instrumental in determining the fracture resistance. There is also a pronounced coupling between fracture and elasticity. Our methodology opens the door to fracture assessment at multiple structural levels, microscopic and potentially nanometer length scale, due to the scalability of scratch tests.

  6. Robust Bonding of Tough Double Network Hydrogel to Bone

    Science.gov (United States)

    Nonoyama, Takayuki; Wada, Susumu; Kiyama, Ryuji; Kitamura, Nobuto; Kurokawa, Takayuki; Nakajima, Tasuku; Yasuda, Kazunori; Gong, Jian Ping

    Tough Double Network (DN) hydrogels are one of candidates as next-generation artificial cartilage from the viewpoints of low friction, water storage capability and toughness. For practical use, the hydrogel must be strongly fixed at the joint. However, strong fixation of such hydrogel to other materials (tissues) has not been achieved yet because the surface property of hydrogel is almost equal to water due to its high water content. Therefore, robust adhesion for fixation and low friction for lithe motion are trade-off relation. Here, we report robust fixation of hydroxyapatite (HAp) mineralized DN hydrogel to the bone without any toxicity. HAp is main inorganic component of bone tissues and has osteoconductive capability. After 4 weeks implantation of HAp/DN gel into rabbit femoral groove, The robust fixation between bone and HAp/DN gel, more than strength of gel matrix, was achieved. The methodology is universal for new biomaterials, which should be fixed on bone, such as ligament and tendon systems.

  7. Understanding the Interdependencies Between Composition, Microstructure, and Continuum Variables and Their Influence on the Fracture Toughness of α/β-Processed Ti-6Al-4V

    Science.gov (United States)

    Collins, P. C.; Koduri, S.; Dixit, V.; Fraser, H. L.

    2018-01-01

    The fracture toughness of a material depends upon the material's composition and microstructure, as well as other material properties operating at the continuum level. The interrelationships between these variables are complex, and thus difficult to interpret, especially in multi-component, multi-phase ductile engineering alloys such as α/β-processed Ti-6Al-4V (nominal composition, wt pct). Neural networks have been used to elucidate how variables such as composition and microstructure influence the fracture toughness directly (i.e., via a crack initiation or propagation mechanism)—and independent of the influence of the same variables influence on the yield strength and plasticity of the material. The variables included in the models and analysis include (i) alloy composition, specifically, Al, V, O, and Fe; (ii) materials microstructure, including phase fractions and average sizes of key microstructural features; (iii) the yield strength and reduction in area obtained from uniaxial tensile tests; and (iv) an assessment of the degree to which plane strain conditions were satisfied by including a factor related to the plane strain thickness. Once trained, virtual experiments have been conducted which permit the determination of each variable's functional dependency on the resulting fracture toughness. Given that the database includes both K 1 C and K Q values, as well as the in-plane component of the stress state of the crack tip, it is possible to quantitatively assess the effect of sample thickness on K Q and the degree to which the K Q and K 1 C values may vary. These interpretations drawn by comparing multiple neural networks have a significant impact on the general understanding of how the microstructure influences the fracture toughness in ductile materials, as well as an ability to predict the fracture toughness of α/β-processed Ti-6Al-4V.

  8. The Origins of Mental Toughness - Prosocial Behavior and Low Internalizing and Externalizing Problems at Age 5 Predict Higher Mental Toughness Scores at Age 14

    National Research Council Canada - National Science Library

    Sadeghi Bahmani, Dena; Hatzinger, Martin; Gerber, Markus; Lemola, Sakari; Clough, Peter J; Perren, Sonja; von Klitzing, Kay; von Wyl, Agnes; Holsboer-Trachsler, Edith; Brand, Serge

    2016-01-01

    The concept of mental toughness (MT) 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...

  9. Further Validation of the Inventory of Mental Toughness Factors in Sport (IMTF-S)

    Science.gov (United States)

    Stonkus, Mark A.; Royal, Kenneth D.

    2015-01-01

    The purpose of this study was to provide further validation a new measure of mental toughness in sport. The Inventory of Mental Toughness Factors in Sport (IMTF-S) was originally developed and validated using principal component analysis. For the present study, the psychometric properties of the IMTF-S were again evaluated, but by way of the Rasch…

  10. Some considerations on the toughness properties of ferritic stainless steels - A brief review

    CSIR Research Space (South Africa)

    Van Zwieten, ACTM

    1993-02-01

    Full Text Available particles on the toughness aspects. Generally the presence of second phases such as carbides, nitrides and oxides, as well as the chromium-rich ferrite, precipitates and sigma-phase, sigma, can cause a significant decrease in the toughness of ferritic...

  11. Evaluation of Sport Mental Toughness and Psychological Wellbeing in Undergraduate Student Athletes

    Science.gov (United States)

    Micoogullari, Bulent Okan; Odek, Ugur; Beyaz, Ozkan

    2017-01-01

    This study aims to evaluate the relationships between sport mental toughness (SMT) and psychological wellbeing (PWB) of undergraduate student athletes. Mental toughness represents the ability of a person to cope with the demands of training and competition, increased determination, focus, confidence, and maintain control under pressure. Mental…

  12. The relationship between developmental experiences and mental toughness in adolescent cricketers.

    Science.gov (United States)

    Gucciardi, Daniel F

    2011-06-01

    The present study investigated the contribution of positive and negative youth sport experiences (i.e., processes or experiences that occur in a particular activity or setting) to self-reported mental toughness among youth-aged cricketers. A sample of 308 male cricketers aged between 13 and 18 years self-reported mental toughness using the Cricket Mental Toughness Inventory (CMTI; Gucciardi & Gordon, 2009), with 187 of these cricketers also documenting their exposure to a variety of positive and negative developmental experiences. Confirmatory factor and internal reliability analyses supported the hypothesized mental toughness measurement model. Structural equation modeling analyses indicated that a variety of developmental experiences were related to various mental toughness components, with initiative experiences evidencing the strongest overall relationship with mental toughness followed by negative peer influences. The number of years playing experience and hours per week training evidenced largely insignificant relationships with the exception of desire to achieve and attentional control components of mental toughness, as well as its global factor. Collectively, these findings lend support for the validity of the CMTI as a valid measure among adolescent cricketers, and highlight the importance of initiative and interpersonal experiences for mental toughness in cricket.

  13. 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.

  14. TRITIUM AGING EFFECTS ON THE FRACTURE TOUGHNESS PROPERTIES OF FORGED STAINLESS STEEL

    Energy Technology Data Exchange (ETDEWEB)

    Morgan, M

    2008-04-14

    The fracture toughness properties of Type 21-6-9 stainless steel were measured for forgings in the unexposed, hydrogen-exposed, and tritium-exposed-and-aged conditions. Fracture toughness samples were cut from conventionally-forged and high-energy-rate-forged forward-extruded cylinders and mechanically tested at room temperature using ASTM fracture-toughness testing procedures. Some of the samples were exposed to either hydrogen or tritium gas (340 MPa, 623 K) prior to testing. Tritium-exposed samples were aged for up to seven years and tested periodically in order to measure the effect on fracture toughness of {sup 3}He from radioactive tritium decay. The results show that hydrogen-exposed and tritium-exposed samples had lower fracture- toughness values than unexposed samples and that fracture toughness decreased with increasing decay {sup 3}He content. Forged steels were more resistant to the embrittling effects of tritium and decay {sup 3}He than annealed steels, although their fracture-toughness properties depended on the degree of sensitization that occurred during processing. The fracture process was dominated by microvoid nucleation, growth and coalescence; however, the size and spacing of microvoids on the fracture surfaces were affected by hydrogen and tritium with the lowest-toughness samples having the smallest microvoids and finest spacing.

  15. Mental Toughness and Transitions to High School and to Undergraduate Study

    Science.gov (United States)

    St Clair-Thompson, Helen; Giles, Rebecca; McGeown, Sarah P.; Putwain, David; Clough, Peter; Perry, John

    2017-01-01

    Mental toughness can be conceptualised as a set of attributes that allow people to deal effectively with challenges, stressors and pressure. Recent work has suggested that it may be a valuable construct to consider within educational settings. The current studies explored the associations between mental toughness and educational transitions. Study…

  16. 75 FR 5495 - Alternate Fracture Toughness Requirements for Protection Against Pressurized Thermal Shock Events...

    Science.gov (United States)

    2010-02-03

    ... From the Federal Register Online via the Government Publishing Office NUCLEAR REGULATORY COMMISSION 10 CFR Part 50 RIN 3150-AI01 Alternate Fracture Toughness Requirements for Protection Against... (75 FR 13), that amends the NRC's regulations to provide alternate fracture toughness requirements for...

  17. 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…

  18. Failure Analysis of the Main Rotor Retention Nut from AH-64 Helicopter

    Science.gov (United States)

    1992-06-01

    1202 and the MTL indepen- dently supplied material. Fracture toughness and Charpy impact tests demonstrated no significant difference between all the...MECHANICAL PROPERTIES Charpy Impact KIc Hardness Specimen (fi-lb) (ksi vrin.) Rockwell C MDHC. Spec. - 48-53 *0257-Al 9.0 - 51.7 *0223-BI 17.0 - 49.9...Hamburg 1 Mr. A. Wilson Republic Steel Corporation, 410 Oberlin Avenue SW, Massillon, OH 44646 1 ATTN: Mr. R. Sweeney 1 Mr. W. H. Brechtel 1 Mr. T. M

  19. Microstructural and Fractographic Characterization of a Thermally Embrittled Nuclear Grade Steel: Part I - Annealing

    Directory of Open Access Journals (Sweden)

    Tarpani José R.

    2002-01-01

    Full Text Available A nuclear reactor pressure vessel steel was submitted to different annealing heat treatments aimed at simulating neutron irradiation damage. The obtained microstructures were mechanically tested with subsequent metallographic and fractographic characterization. The relevant microstructural and fractographic aspects were employed in the interpretation of the mechanical behavior of the microstructures in both quasi-static (J-R curve and dynamic (Charpy impact loading regimes. A well defined relationship was determined between the elastic-plastic fracture toughness parameter J-integral and the Charpy impact energy for very most of the microstructures.

  20. Multi-scale Multi-mechanism Design of Tough Hydrogels: Building Dissipation into Stretchy Networks

    Science.gov (United States)

    Zhao, Xuanhe

    2014-01-01

    As swollen polymer networks in water, hydrogels are usually brittle. However, hydrogels with high toughness play critical roles in many plant and animal tissues as well as in diverse engineering applications. Here we review the intrinsic mechanisms of a wide variety of tough hydrogels developed over past few decades. We show that tough hydrogels generally possess mechanisms to dissipate substantial mechanical energy but still maintain high elasticity under deformation. The integrations and interactions of different mechanisms for dissipating energy and maintaining elasticity are essential to the design of tough hydrogels. A matrix that combines various mechanisms is constructed for the first time to guide the design of next-generation tough hydrogels. We further highlight that a particularly promising strategy for the design is to implement multiple mechanisms across multiple length scales into nano-, micro-, meso-, and macro-structures of hydrogels. PMID:24834901

  1. 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.

  2. Mental toughness of mixed martial arts athletes at different levels of competition.

    Science.gov (United States)

    Chen, Mark A; Cheesman, David J

    2013-06-01

    This study investigated whether mental toughness distinguishes mixed martial arts (MMA) athletes competing at different levels. It was theorized that higher mental toughness would separate those competing at the professional level compared to lower levels. Male MMA competitors (N = 136, M age = 27.1 yr., SD = 4.8) were categorized as amateur, semi-professional, or professional and assessed by questionnaire using the Psychological Performance Inventory-A and the Sports Mental Toughness Questionnaire. There were statistically significant differences between the three groups on mental toughness. The professional group had higher scores compared to semi-professional and amateur groups with regard to confidence, positive cognition, and determination. The findings supported previous work that athletes performing at higher levels have superior mental toughness.

  3. The development of in situ fracture toughness evaluation techniques in hydrogen environment

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jy-An John [ORNL; Ren, Fei [ORNL; Tan, Ting [ORNL; Liu, Ken C [ORNL

    2014-01-01

    Fracture behavior and fracture toughness are of great interest regarding reliability of hydrogen pipelines and storage tanks, however, many conventional fracture testing techniques are difficult to be realized under the presence of hydrogen, in addition to the inherited specimen size effect. Thus it is desired to develop novel in situ fracture toughness evaluation techniques to study the fracture behavior of structural materials in hydrogen environments. In this study, a torsional fixture was developed to utilize an emerging fracture testing technique, Spiral Notch Torsion Test (SNTT). The in situ testing results indicated that the exposure to H2 significantly reduces the fracture toughness of 4340 high strength steels by up to 50 percent. Furthermore, SNTT tests conducted in air demonstrated a significant fracture toughness reduction in samples subject to simulated welding heat treatment using Gleeble, which illustrated the effect of welding on the fracture toughness of this material.

  4. Fracture toughness of irradiated candidate materials for ITER first wall/blanket structures: Summary report

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, D.J.; Pawel, J.E.; Grossbeck, M.L.; Rowcliffe, A.F. [Oak Ridge National Lab., TN (United States)] [and others

    1996-04-01

    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 90 250{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 austenic stainless steels, but the toughness remains quite high. The toughness decreases as the temperature increases. Irradiation at 250{degrees}C is more damaging that at 90{degrees}C, causing larger decreases in the fracture toughness. The ferritic-martensitic steels HT-9 and F82H show significantly greater reductions in fracture toughness that the austenitic stainless steels.

  5. Dynamic Fracture Initiation Toughness of ASTM A533, Grade B Steel Plate

    Energy Technology Data Exchange (ETDEWEB)

    Graham, S.M.; Link, R.E.

    1999-05-01

    The dynamic fracture toughness of an ASTM A533, Grade B steel plate was determined at several temperatures in the ductile-brittle transition region. Crack-tip loading rates ranged from approximately 10(sup3) to 10(sup5) MPa m/s. The fracture toughness was shown to decrease with increased loading rate. The dynamic fracture toughness was compared with results from previous investigations, and it was shown that the decrease in toughness due to increased loading rate at the highest test temperature was not as severe as reported in previous investigations. It was also shown that the reference temperature. T(sub0) was better index of the fracture toughness vs. temperature relationship than the nil-ductility temperature, RT(subNDT), for this material.

  6. iTOUGH2: A multiphysics simulation-optimization framework for analyzing subsurface systems

    Science.gov (United States)

    Finsterle, S.; Commer, M.; Edmiston, J. K.; Jung, Y.; Kowalsky, M. B.; Pau, G. S. H.; Wainwright, H. M.; Zhang, Y.

    2017-11-01

    iTOUGH2 is a simulation-optimization framework for the TOUGH suite of nonisothermal multiphase flow models and related simulators of geophysical, geochemical, and geomechanical processes. After appropriate parameterization of subsurface structures and their properties, iTOUGH2 runs simulations for multiple parameter sets and analyzes the resulting output for parameter estimation through automatic model calibration, local and global sensitivity analyses, data-worth analyses, and uncertainty propagation analyses. Development of iTOUGH2 is driven by scientific challenges and user needs, with new capabilities continually added to both the forward simulator and the optimization framework. This review article provides a summary description of methods and features implemented in iTOUGH2, and discusses the usefulness and limitations of an integrated simulation-optimization workflow in support of the characterization and analysis of complex multiphysics subsurface systems.

  7. On the mechanistic origins of toughness in bone

    Energy Technology Data Exchange (ETDEWEB)

    Launey, Maximilien E.; Buehler, Markus J.; Ritchie, Robert O.

    2009-10-07

    One of the most intriguing protein materials found in Nature is bone, a material composed out of assemblies of tropocollagen molecules and tiny hydroxyapatite mineral crystals, forming an extremely tough, yet lightweight, adaptive and multi-functional material. Bone has evolved to provide structural support to organisms, and therefore, its mechanical properties are of great physiological relevance. In this article, we review the structure and properties of bone, focusing on mechanical deformation and fracture behavior from the perspective of the multi-dimensional hierarchical nature of its structure. In fact, bone derives its resistance to fracture with a multitude of deformation and toughening mechanisms at many of these size-scales, ranging from the nanoscale structure of its protein molecules to its macroscopic physiological scale.

  8. Tensile and fracture toughness test results of neutron irradiated beryllium

    Energy Technology Data Exchange (ETDEWEB)

    Chaouadi, R.; Moons, F.; Puzzolante, J.L. [Centre d`Etude de l`Energie Nucleaire, Mol (Belgium)

    1998-01-01

    Tensile and fracture toughness test results of four Beryllium grades are reported here. The flow and fracture properties are investigated by using small size tensile and round compact tension specimens. Irradiation was performed at the BR2 material testing reactor which allows various temperature and irradiation conditions. The fast neutron fluence (>1 MeV) ranges between 0.65 and 2.45 10{sup 21} n/cm{sup 2}. In the meantime, un-irradiated specimens were aged at the irradiation temperatures to separate if any the effect of temperature from irradiation damage. Test results are analyzed and discussed, in particular in terms of the effects of material grade, test temperature, thermal ageing and neutron irradiation. (author)

  9. Tough ceramic coatings: Carbon nanotube reinforced silica sol-gel

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, A.J., E-mail: antoniojulio.lopez@urjc.es [Dept. de Ciencia e Ingenieria de Materiales, ESCET, Universidad Rey Juan Carlos, C/Tulipan s/n, Mostoles 28933, Madrid (Spain); Rico, A.; Rodriguez, J.; Rams, J. [Dept. de Ciencia e Ingenieria de Materiales, ESCET, Universidad Rey Juan Carlos, C/Tulipan s/n, Mostoles 28933, Madrid (Spain)

    2010-08-15

    Silica coatings reinforced with carbon nanotubes were produced via sol-gel route using two mixing techniques of the sol-gel precursors, mechanical and ultrasonic mixing, and dip-coating as deposition process on magnesium alloy substrates. Effective incorporation and distribution of 0.1 wt.% of carbon nanotubes in the amorphous silica matrix of the coatings were achieved using both techniques. Fabrication procedure determines the morphological aspects of the coating. Only mechanical mixing process produced coatings dense and free of defects. Nanoindentation technique was used to examine the influence of the fabrication process in the mechanical features of the final coatings, i.e. indentation fracture toughness, Young's modulus and hardness. A maximum toughening effect of about 24% was achieved in silica coatings reinforced with carbon nanotubes produced by the mechanical mixing route. Scanning electron microscopy investigation revealed that the toughening of these reinforced coatings was mainly due to bridging effect of the reinforcement.

  10. Growth and regrowth of tough lovegrass (Eragrostis plana Nees

    Directory of Open Access Journals (Sweden)

    Simone Meredith Scheffer-Basso

    2012-02-01

    Full Text Available This study evaluated the morphological development of two populations of tough lovegrass during 120 days of continuous growth (Experiment I, and the regrowth of one population under the combination of cutting height (5 cm and 10 cm and phenological stage at the first cutting (vegetative and beginning of flowering; Experiment II. In Experiment I, plants were harvested at 30, 60, 90 and 120 days of growth; in Experiment II, three cuttings were carried out at every 30 days, and the plants were harvested four weeks after the previous one. In Experiment I, the populations did not differ for morphological development, showing a linear increase in height and tiller number, and a quadratic trend for root and shoot dry matter (DM. At 120 days of growth, plants presented 10 basal tillers and 80 leaves, strongly compressed at the base and no sign of senescence. In Experiment II, there was no significant cutting height × phenological stage interaction, but cuttings at 5 cm reduced plant size and yield. Cuttings started at the vegetative stage decreased the root (3.06 g DM/plant and stubble dry matter (1.17 g DM/plant, compared with 6.84 g and 3.99 g DM/plant, respectively, with cuttings started at the flowering stage. Tough lovegrass shows basal architecture, basal bud renovation, leaves densely compressed in the tiller base, high belowground allocation, and elongation of internodes only in reproductive stage. Mechanical control is an alternative method to minimize its growth, especially if it is carried out early in the growing season and at low cutting height.

  11. A master curve-mechanism based approach to modeling the effects of constraint, loading rate and irradiation on the toughness-temperature behavior of a V-4Cr-4Ti alloy

    Energy Technology Data Exchange (ETDEWEB)

    Odette, G.R.; Donahue, E.; Lucas, G.E.; Sheckherd, J.W. [Univ. of California, Santa Barbara, CA (United States)

    1996-10-01

    The influence of loading rate and constraint on the effective fracture toughness as a function of temperature [K{sub e}(T)] of the fusion program heat of V-4Cr-4Ti was measured using subsized, three point bend specimens. The constitutive behavior was characterized as a function of temperature and strain rate using small tensile specimens. Data in the literature on this alloy was also analysed to determine the effect of irradiation on K{sub e}(T) and the energy temperature (E-T) curves measured in subsized Charpy V-notch tests. It was found that V-4Cr-4Ti undergoes {open_quotes}normal{close_quotes} stress-controlled cleavage fracture below a temperature marking a sharp ductile-to-brittle transition. The transition temperature is increased by higher loading rates, irradiation hardening and triaxial constraint. Shifts in a reference transition temperature due to higher loading rates and irradiation can be reasonably predicted by a simple equivalent yield stress model. These results also suggest that size and geometry effects, which mediate constraint, can be modeled by combining local critical stressed area {sigma}*/A* fracture criteria with finite element method simulations of crack tip stress fields. The fundamental understanding reflected in these models will be needed to develop K{sub e}(T) curves for a range of loading rates, irradiation conditions, structural size scales and geometries relying (in large part) on small specimen tests. Indeed, it may be possible to develop a master K{sub e}(T) curve-shift method to account for these variables. Such reliable and flexible failure assessment methods are critical to the design and safe operation of defect tolerant vanadium structures.

  12. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1993-12-01

    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.

  14. Survival of the scheming: a genetically informed link between the dark triad and mental toughness.

    Science.gov (United States)

    Onley, Michael; Veselka, Livia; Schermer, Julie Aitken; Vernon, Philip A

    2013-12-01

    The present study is the first behavioral genetic investigation of the Dark Triad traits of personality, consisting of Machiavellianism, narcissism, and psychopathy, and the variable of mental toughness, reflecting individual differences in the ability to cope when under pressure. The purpose of this investigation was to explore a potential explanation for the success of individuals exhibiting the Dark Triad traits in workplace and social settings. Participants were adult twins who completed the MACH-IV, the Narcissistic Personality Inventory, and the Self-Report Psychopathy Scale assessing Machiavellianism, narcissism, and psychopathy, respectively, as well as the MT48, measuring mental toughness. Correlational analyses of the data revealed significant positive phenotypic associations between mental toughness and narcissism. Psychopathy and Machiavellianism, however, both showed some significant negative phenotypic correlations with mental toughness. Bivariate behavioral genetic analyses of the data were conducted to assess the extent to which these significant phenotypic correlations were attributable to common genetic and/or common environmental factors. Results indicate that correlations between narcissism and mental toughness were attributable primarily to common non-shared environmental factors, correlations between Machiavellianism and mental toughness were influenced by both common genetic and common non-shared environmental factors, and the correlations between psychopathy and mental toughness were attributable entirely to correlated genetic factors. Implications of these findings in the context of etiology and organizational adaptation are discussed.

  15. The Influence of Temperature on Mode I Fracture Toughness and Fracture Characteristics of Sandstone

    Science.gov (United States)

    Feng, Gan; Kang, Yong; Meng, Tao; Hu, Yao-qing; Li, Xiao-hong

    2017-08-01

    This study investigated the influence of temperature on the mode I fracture toughness of sandstone using semicircular bend specimens. Fracture characteristics were studied using scanning electron microscopy and other means. The results showed that temperature influenced fracturing in three stages along a temperature gradient. In the low-temperature stage (20-100 °C), fracture toughness increases slowly, with a total increase of approximately 11%. At the medium-temperature stage (100-500 °C), fracture toughness decreases slowly, at a rate of approximately 18%. During the high-temperature stage (500-800 °C), fracture toughness was reduced by approximately 44%. The mode I fracture toughness has a clear temperature threshold (500-600 °C). Below this threshold, the fracture toughness decreases slowly. When the temperature threshold is reached, the fracture toughness decreases sharply. The sharp decrease is mainly caused by the creation of a fragmentation structure. The sandstone experiences more transgranular fracture mechanics in the low-temperature stage compared to the high-temperature stage. Above 100 °C, the mechanisms include transgranular fracturing, intergranular fracturing, thermal cracking, and mutual coupling fracturing. When the temperature exceeds 500 °C, several different fragmentation structures are seen. This research study provides significant data to evaluate fracture characteristics and rock safety and stability after heat treatment.

  16. Tensile and impact properties of vanadium-base alloys irradiated at low temperatures in the ATR-A1 experiment

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, H.; Nowicki, L.J.; Billone, M.C.; Chung, H.M.; Smith, D.L. [Argonne National Lab., IL (United States)

    1998-03-01

    Subsize tensile and Charpy specimens made from several V-(4-5)Cr-(4-5)Ti alloys were irradiated in the ATR-A1 experiment to study the effects of low-temperature irradiation on mechanical properties. These specimens were contained in lithium-bonded subcapsules and irradiated at temperatures between {approx}200 and 300 C. Peak neutron damage was {approx}4.7 dpa. Postirradiation testing of these specimens has begun. Preliminary results from a limited number of specimens indicate a significant loss of work-hardening capability and dynamic toughness due to the irradiation. These results are consistent with data from previous low-temperature neutron irradiation experiments on these alloys.

  17. Bone fracture toughness and strength correlate with collagen cross-link maturity in a dose-controlled lathyrism mouse model.

    Science.gov (United States)

    McNerny, Erin M B; Gong, Bo; Morris, Michael D; Kohn, David H

    2015-03-01

    Collagen cross-linking is altered in many diseases of bone, and enzymatic collagen cross-links are important to bone quality, as evidenced by losses of strength after lysyl oxidase inhibition (lathyrism). We hypothesized that cross-links also contribute directly to bone fracture toughness. A mouse model of lathyrism using subcutaneous injection of up to 500 mg/kg β-aminopropionitrile (BAPN) was developed and characterized (60 animals across 4 dosage groups). Three weeks of 150 or 350 mg/kg BAPN treatment in young, growing mice significantly reduced cortical bone fracture toughness, strength, and pyridinoline cross-link content. Ratios reflecting relative cross-link maturity were positive regressors of fracture toughness (HP/[DHLNL + HLNL] r(2)  = 0.208, p cross-links were significant positive regressors of tissue strength (lysyl pyridinoline r(2)  = 0.159, p = 0.014; hydroxylysyl pyridinoline r(2)  = 0.112, p cross-links, which were not significantly reduced by BAPN, did not correlate with mechanical properties. The effect of BAPN treatment on mechanical properties was dose specific, with the greatest impact found at the intermediate (350 mg/kg) dose. Calcein labeling was used to define locations of new bone formation, allowing for the identification of regions of normally cross-linked (preexisting) and BAPN-treated (newly formed, cross-link-deficient) bone. Raman spectroscopy revealed spatial differences attributable to relative tissue age and effects of cross-link inhibition. Newly deposited tissues had lower mineral/matrix, carbonate/phosphate, and Amide I cross-link (matrix maturity) ratios compared with preexisting tissues. BAPN treatment did not affect mineral measures but significantly increased the cross-link (matrix maturity) ratio compared with newly formed control tissue. Our study reveals that spatially localized effects of short-term BAPN cross-link inhibition can alter the whole-bone collagen cross-link profile to a

  18. Effects of irradiation to 4 dpa at 390 C on the fracture toughness of vanadium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gruber, E.E.; Galvin, T.M.; Chopra, O.K. [Argonne National Lab., IL (United States)

    1998-09-01

    Fracture toughness J-R curve tests were conducted at room temperature on disk-shaped compact-tension DC(T) specimens of three vanadium alloys having a nominal composition of V-4Cr-4Ti. The alloys in the nonirradiated condition showed high fracture toughness; J{sub IC} could not be determined but is expected to be above 600 kJ/m{sup 2}. The alloys showed very poor fracture toughness after irradiation to 4 dpa at 390 C, e.g., J{sub IC} values of {approx}10 kJ/m{sup 2} or lower.

  19. 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.

  20. Fracture toughness of glass sealants for solid oxide fuel cell application

    DEFF Research Database (Denmark)

    Abdoli, Hamid; Alizadeh, Parvin; Boccaccini, Dino

    2014-01-01

    Glass and glass-ceramics are versatile materials and have been widely used for sealing in the ongoing development of intermediate temperature solid oxide fuel cell (SOFC) technology where its integrity is crucial for reliable operation of the stack. The fracture toughness is a key parameter...... required for the prediction of the mechanical performance of a seal glass. A comparative indentation study on two RE-glasses (RE=La and Y) was performed to evaluate their fracture toughness. Indentation toughness was calculated both through measurements of the indentation crack lengths and of crack......-opening displacements in the near regions of a crack tip. Both approaches exhibited good agreement. La-containing glass showed higher stiffness, hardness and fracture toughness, which has been related to the in-situ toughening mechanism caused by devitrification and formation of crystalline phases. © 2013 Elsevier B.V....

  1. 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.

  2. Atomistic simulations on intergranular fracture toughness of copper bicrystals with symmetric tilt grain boundaries

    Science.gov (United States)

    Cui, Cheng Bin; Beom, Hyeon Gyu

    2018-01-01

    The intergranular fracture toughness of Cu bicrystals with symmetric tilt grain boundaries was investigated using atomistic simulations. Mode I fracture of Cu bicrystals with an intergranular crack was considered. The boundary conditions were specified by the near-tip displacement fields obtained based on linear elastic fracture mechanics (LEFM). Based on the energy interpretation of the energy release rate, a two-specimen method was adopted to determine the fracture toughness. The simulation results of the fracture toughness matched well with those determined using LEFM. In contrast to the toughness obtained using the Griffith energy criterion, the atomistic simulation results for the same bicrystal were not constants, but dependent on the crack-tip circumstances. This behavior was mainly associated with the different local stress conditions and fracture patterns observed for the different models.

  3. 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.

  4. Microstructure and fracture toughness of hot pressed zirconia-toughened sialon

    Energy Technology Data Exchange (ETDEWEB)

    Cain, M.G.; Lewis, M.H. (Univ. of Warwick, Coventry (United Kingdom))

    1993-06-01

    Zirconia-toughened sialon composites have been fabricated using conventional hot-pressing techniques. The fracture toughness and microstructure were determined for CeO[sub 2]- and Y[sub 2]O[sub 3]-stabilized ZrO[sub 2] additives and also as a function of volume percent ZrO[sub 2]. The Yttria system showed a linear increase in fracture toughness with increasing volume fraction zirconia content while the ceria-stabilized system exhibited a peak in fracture toughness at 20 vol% ZrO[sub 2] content. The fracture toughness at 800 C was measured and correlated with the microstructure. High-temperature stability was determined and it was found that the deleterious nitride phases of zirconium could be precluded from the microstructure.

  5. Size dependence of the fracture toughness of copper nanostrips under tension

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Gi Hun; Kim, Jang Hyun; Beom, Hyeon Gyu [Inha University, Incheon (Korea, Republic of)

    2016-06-15

    This paper investigates the size dependence of the fracture toughness of single-crystal copper nanostrips. Atomistic simulations are conducted on center-cracked nanostrips under tension, and atomic interactions are described by the embedded atom method potential. Fracture toughness is measured as the critical value of the strain energy release rate, and fracture toughness based on the Griffith fracture criterion is obtained by calculating crack-surface formation energy. To verify linear elastic fracture mechanics at the nanoscale, the J integral is evaluated using the finite-element method. The results show the value of fracture toughness obtained from atomistic simulations and the finite-element method to be influenced by the width.

  6. Interfacial fracture toughness of different resin cements bonded to a lithium disilicate glass ceramic

    National Research Council Canada - National Science Library

    Hooshmand, Tabassom; Rostami, Golriz; Behroozibakhsh, Marjan; Fatemi, Mostafa; Keshvad, Alireza; van Noort, Richard

    2012-01-01

    To evaluate the effect of HF acid etching and silane treatment on the interfacial fracture toughness of a self-adhesive and two conventional resin-based cements bonded to a lithium disilicate glass ceramic...

  7. Initial evaluation of ultrasonic attenuation measurements for estimating fracture toughness of RPV steels

    Energy Technology Data Exchange (ETDEWEB)

    Hiser, A.L. Jr.; Green, R.E. Jr. [Johns Hopkins Univ., Baltimore, MD (United States). Center for Nondestructive Evaluation

    1999-08-01

    Neutron bombardment of reactor pressure vessel (RPV) steels causes reductions in fracture toughness in these steels, termed neutron irradiation embrittlement. Currently, there are no accepted methods for nondestructive determination of the extent of the irradiation embrittlement nor the actual fracture toughness of the reactor pressure vessel. This paper provides initial results of an effort addressing the use of ultrasonic attenuation as a suitable parameter for nondestructive determination of irradiation embrittlement in RPV steels. (orig.)

  8. [Fracture toughness of zirconia ceramic crowns made by feather-edge tooth preparation design].

    Science.gov (United States)

    Mirković, Nemanja; Gostović, Aleksandra Spadijer; Lazić, Zoran; Trifković, Branka

    2012-07-01

    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. 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 mmn 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. 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 2000 N, what was double beyond a recommended value. The mean value of fracture toughness in the feather-edge group was 2090 N, and in shoulder group it was 2214 N. 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 gingival inflammatory response.

  9. The effect of plasticity to interlaminar fracture toughness of adhesive bond of composite

    Science.gov (United States)

    Pavelko, V.; Lapsa, K.; Pavlovskis, P.

    2017-10-01

    In this paper the effect of plasticity of an adhesive to interlaminar fracture toughness of adhesive bond of thin-walled layered composite is investigated. The characteristics of failure of low toughness adhesive layer were obtained using the double cantilever beam (DCB) sample. The main features of plasticity effect are obtained. The procedure of results use for strength analysis of structure with the plasticity affected adhesive joint is proposed.

  10. 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

  11. Novel in Vitro Modification of Bone for an Allograft with Improved Toughness Osteoconductivity

    Science.gov (United States)

    2015-06-01

    Yeni, and T.L. Norman, Fracture toughness is dependent on bone location--a study of the femoral neck , femoral shaft, and the tibial shaft. J Biomed...711 (4,5-Dimethyl-3-(2-oxo-2-phenylethyl)-thiazolium chloride) in improving both mechanical and biological quality of femoral cortical bone for the...division, apoptosis and mineralization as well as the R-curve parameters including crack propagation, fracture toughness and critical crack length were

  12. Maximising the Interfacial Fracture Toughness of Thin Coatings and Substrate through Optimisation of Defined Parameters

    OpenAIRE

    Khan, Zulfiqar Ahmad; Nazir, M.H.

    2015-01-01

    The influence of three parameters i.e. interfacial roughness, coating thickness and the size of impurity at the interface on interfacial fracture toughness has been investigated within the framework of two approaches i.e. thermodynamics and fracture mechanics. Mathematical relationship for both the approaches have been designed independently and then fused to form a governing law for evaluating the interfacial toughness. Simulation techniques founded on the experimental studies, have been dev...

  13. A phenomenological exploration of exercise mental toughness: perceptions of exercise leaders and regular exercisers

    OpenAIRE

    Crust, Lee; Swann, Christian; Allen-Collinson, Jacquelyn; Breckon, Jeff; Weinberg, Robert

    2014-01-01

    Although elite sport has provided an ideal context for exploring mental toughness (MT), currently, there is scant research examining how this construct might be equally applicable in exercise settings, where high rates of attrition have been reported. The present research, therefore, aimed to address this gap, and to understand and conceptualise exercise mental toughness (EMT) through in-depth phenomenological interviews with a range of exercise leaders and exercise participants. Seven qualif...

  14. 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…

  15. Supercomputing with TOUGH2 family codes for coupled multi-physics simulations of geologic carbon sequestration

    Science.gov (United States)

    Yamamoto, H.; Nakajima, K.; Zhang, K.; Nanai, S.

    2015-12-01

    Powerful numerical codes that are capable of modeling complex coupled processes of physics and chemistry have been developed for predicting the fate of CO2 in reservoirs as well as its potential impacts on groundwater and subsurface environments. However, they are often computationally demanding for solving highly non-linear models in sufficient spatial and temporal resolutions. Geological heterogeneity and uncertainties further increase the challenges in modeling works. Two-phase flow simulations in heterogeneous media usually require much longer computational time than that in homogeneous media. Uncertainties in reservoir properties may necessitate stochastic simulations with multiple realizations. Recently, massively parallel supercomputers with more than thousands of processors become available in scientific and engineering communities. Such supercomputers may attract attentions from geoscientist and reservoir engineers for solving the large and non-linear models in higher resolutions within a reasonable time. However, for making it a useful tool, it is essential to tackle several practical obstacles to utilize large number of processors effectively for general-purpose reservoir simulators. We have implemented massively-parallel versions of two TOUGH2 family codes (a multi-phase flow simulator TOUGH2 and a chemically reactive transport simulator TOUGHREACT) on two different types (vector- and scalar-type) of supercomputers with a thousand to tens of thousands of processors. After completing implementation and extensive tune-up on the supercomputers, the computational performance was measured for three simulations with multi-million grid models, including a simulation of the dissolution-diffusion-convection process that requires high spatial and temporal resolutions to simulate the growth of small convective fingers of CO2-dissolved water to larger ones in a reservoir scale. The performance measurement confirmed that the both simulators exhibit excellent

  16. Effect of Graphene Nanosheets on the Morphology, Crystallinity, and Thermal and Electrical Properties of Super Tough Polyamide 6 Using SEBS Compounds

    Directory of Open Access Journals (Sweden)

    Farzaneh Alirezaei Hoor

    2015-01-01

    Full Text Available Super tough polyamide 6 was prepared by using SEBS and effect of SEBS-g-MA as a compatibilizer of PA6/SEBS matrix on mechanical properties was investigated. Thus super tough polyamide 6/graphene nanocomposites were produced using graphene nanosheets (GNs through the melt compounding method. To compare the effectiveness of graphene, effects of graphite and carbon black (the other carbon structures are also studied on the same matrix. The effects of graphene on crystallinity, improvements of morphology, and thermal and electrical properties of the nanocomposites were researched and compared with similar samples of graphite and carbon black. Due to the reaction between the maleic anhydride groups of SEBS and amine groups of nylon chains during the melt mixing process, super tough polyamide 6 was produced with high impact and tensile strength. The most important results of this study can be noted as an increase in the electrical conductivity and thermal stability by adding graphene to PA6/SEBS blend. Also the effect of graphene compatibility on PA6/SEBS/SEBS-g-MA blend was investigated with studying morphology.

  17. Effects of substrate preheating during direct energy deposition on microstructure, hardness, tensile strength, and notch toughness

    Science.gov (United States)

    Baek, Gyeong Yun; Lee, Ki Yong; Park, Sang Hu; Shim, Do Sik

    2017-11-01

    This study examined the effects of substrate preheating for the hardfacing of cold-press dies using the high-speed tool steel AISI M4. The preheating of the substrate is a widely used technique for reducing the degree of thermal deformation and preventing crack formation. We investigated the changes in the metallurgical and mechanical properties of the high-speed tool steel M4 deposited on an AISI D2 substrate with changes in the substrate preheating temperature. Five preheating temperatures (100-500 °C; interval of 100 °C) were selected, and the changes in the temperature of the substrate during deposition were observed. As the preheating temperature of the substrate was increased, the temperature gradient between the melting layer and the substrate decreased; this prevented the formation of internal cracks, owing to thermal stress relief. Field-emission scanning electron microscopy showed that a dendritic structure was formed at the interface between the deposited layer and the substrate while a cellular microstructure was formed in the deposited layer. As the preheating temperature was increased, the sizes of the cells and precipitated carbides also increased. Furthermore, the hardness increased slightly while the strength and toughness decreased. Moreover, the tensile and impact properties deteriorated rapidly at excessively high preheating temperatures (greater than 500 °C). The results of this study can be used as preheating criteria for achieving the desired mechanical properties during the hardfacing of dies and molds.

  18. Correlating mode-I fracture toughness and mechanical properties of heat-treated crystalline rocks

    Directory of Open Access Journals (Sweden)

    Mayukh Talukdar

    2018-02-01

    Full Text Available For the effect of thermal treatment on the mode-I fracture toughness (FT, three crystalline rocks (two basalts and one tonalite were experimentally investigated. Semi-circular bend specimens of the rocks were prepared following the method suggested by the International Society for Rock Mechanics (ISRM and were treated at various temperatures ranging from room temperature (25 °C to 600 °C. Mode-I FT was correlated with tensile strength (TS, ultrasonic velocities, and Young's modulus (YM. Additionally, petrographic and X-ray diffraction analyses were carried out to find the chemical changes resulting from the heat treatment. Further, scanning electron microscopy (SEM was conducted to observe the micro structural changes when subjected to high temperatures. These experiments demonstrate that heat treatment has a strong negative impact on the FT and mechanical properties of the rocks. From room temperature to 600 °C, mode-I FT values of massive basalt, giant plagioclase basalt, and tonalite were reduced by nearly 52%, 68%, and 64%, respectively. Also, at all temperature levels, FT and mechanical properties are found to be exponentially correlated. However, the exact nature of the relationship mainly depends on rock type. Besides, TS was found to be a better indicator of degradation degree than the mode-I FT. SEM images show that micro crack density and structural disintegration of the mineral grains increase with temperature. These physical changes confirm the observed reduction in the stiffness of heat-treated crystalline rocks.

  19. Toughness enhancement of powder metallurgy zirconium containing aluminum-lithium alloys through degassing

    Energy Technology Data Exchange (ETDEWEB)

    LaSalle, J.C.; Raybould, D.; Das, S.K.; Limoncelli, E.V.

    1993-07-06

    In a method for producing a consolidated article from a rapidly solidified, zirconium containing aluminum lithium alloy powder, the improvement is described comprising the step of: degassing said powder in a vacuum at a temperature of at least about 450 C, said powder consisting essentially of the formula Al[sub bal]Li[sub a]Cu[sub b]Mg[sub c]Zr[sub d], where a' ranges from about 2.4 to 2.8 wt%, b' ranges from about 0.5 to 2.0 wt%, c' ranges from 0.2 to 2.0 wt% and d' ranges from greater than about 0.8 to 1.0 wt%, the balance being aluminum and said article having an ultimate tensile strength ranging from 75 to 80 ksi, a tensile elongation ranging from about 5 to 8% and a T-L notched impact toughness ranging from about 100 to 150 in-lb/in[sup 2].

  20. Effects of substrate preheating during direct energy deposition on microstructure, hardness, tensile strength, and notch toughness

    Science.gov (United States)

    Baek, Gyeong Yun; Lee, Ki Yong; Park, Sang Hu; Shim, Do Sik

    2017-10-01

    This study examined the effects of substrate preheating for the hardfacing of cold-press dies using the high-speed tool steel AISI M4. The preheating of the substrate is a widely used technique for reducing the degree of thermal deformation and preventing crack formation. We investigated the changes in the metallurgical and mechanical properties of the high-speed tool steel M4 deposited on an AISI D2 substrate with changes in the substrate preheating temperature. Five preheating temperatures (100-500 °C; interval of 100 °C) were selected, and the changes in the temperature of the substrate during deposition were observed. As the preheating temperature of the substrate was increased, the temperature gradient between the melting layer and the substrate decreased; this prevented the formation of internal cracks, owing to thermal stress relief. Field-emission scanning electron microscopy showed that a dendritic structure was formed at the interface between the deposited layer and the substrate while a cellular microstructure was formed in the deposited layer. As the preheating temperature was increased, the sizes of the cells and precipitated carbides also increased. Furthermore, the hardness increased slightly while the strength and toughness decreased. Moreover, the tensile and impact properties deteriorated rapidly at excessively high preheating temperatures (greater than 500 °C). The results of this study can be used as preheating criteria for achieving the desired mechanical properties during the hardfacing of dies and molds.

  1. Tough and highly stretchable polyacrylamide nanocomposite hydrogels with chitin nanocrystals.

    Science.gov (United States)

    Liu, Mingxian; Huang, Jiandong; Luo, Binghong; Zhou, Changren

    2015-01-01

    Chitin nanocrystals (CNCs) that were 10-20 nm wide and 100-500 nm long were synthetized via acidolysis and characterized with various methods. To avoid the flocculation of CNCs in the initiator solution during acrylamide polymerization, chitosan was selected as a surface modifier. The chitosan-modified CNCs were employed as multifunctional crosslinkers for the polyacrylamide (PAAm) nanocomposite (NC) hydrogels. The NC gels were tough and stretchable; for example, the maximum tensile strength and the elongation at break of the NC gels were 90 kPa and 3070%, respectively. The dynamic shear modulus of the NC gels was also significantly higher than that of the PAAm. The NC gels were nearly free of residual strain after 2000% elongation. The microstructures of all NC gels were porous, with a pore size of 20-100 μm. The maximum equilibrium swelling degree of the NC gels was 3800%. The improvement in the properties of the NC gels is attributed to the good dispersion of CNCs and the interfacial interactions in the composites. This work developed PAAm NC hydrogels with CNCs for application as absorbent or biomedical material due to the high mechanical properties, high absorb ability and good biocompatibility of CNCs and explored new applications for CNCs as well. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. TOUGH2 model of the G-tunnel heater test

    Energy Technology Data Exchange (ETDEWEB)

    Ho, C.K.; Eaton, R.R. [Sandia National Lab., Albuquerque, NM (United States)

    1995-12-01

    An experiment designed to observe water migration under non-isothermal conditions in welded tuff was performed in 1980 in the welded portion of the Grouse Canyon Member in the U12g tunnel (G-tunnel) at Rainier Mesa. Significant amounts of water were observed to migrate towards a heated hole bored into the welded tuff. The water migration was attributed to vapor phase diffusion, but other processes such as gravity driven flow were not considered and may have contributed significantly to the observed water migration. The modeling studies presented here address processes of water migration near heated regions in partially saturated tuff. The multiphase, non-isothermal numerical code TOUGH2 was used to model the G-Tunnel heater experiment. The numerical simulation consisted of 10 days of heating at 1000 W. Temperatures, liquid saturations, gas pressures, gas and liquid velocities, and vapor mass fractions were recorded to determine the processes affecting water migration. Results of the simulation indicated that water migration near heated tuffaceous rock involves a combination of processes. Gas-phase advection and diffusion transported water vapor that was evaporated near the heater toward outer regions. Water vapor condensed in cooler regions away from the heater, increasing the saturations. As liquid water accumulated in the heater borehole, capillary suction pulled some of the liquid toward the drier heated region while gravity drained some of the liquid away from the heater. In natural systems, high permeability fractures could mimic the role of the heater hole.

  3. Fracture toughness (K{sub IC}) data reduction program

    Energy Technology Data Exchange (ETDEWEB)

    Heiman, M.R.

    1998-09-01

    This report documents the development, verification, and use instructions for an automated K{sub IC} data reduction program written in the Hewlett Packard Visual Engineering Environment (HP VEE) programming language. Currently, when the standard test method Plane-Strain Fracture Toughness of Metallic materials (K{sub IC}), is performed, the data is reduced manually. Date reduction includes 15 detailed calculations required by the American Society for Testing and Materials (ASTM) E399 to determine the validity of the computed K{sub IC} value. Manual data reduction is both time consuming, tedious, and prone to errors. Since all K{sub IC} tests are completed using a data acquisition system to digitally record time, load, and crack opening displacement (COD); automation of K{sub IC} data reduction using a computer program to perform all calculations rapidly, enables processing of a large amount of data. The K{sub IC} data reduction program reduces any computer American Standard Code for Information Interchange (ASCII) data file. Thus, the K{sub IC} data reduction program is also used to over check tests performed at other facilities. The program was qualified based on mechanical properties of commercial alloy specimens.

  4. Effect of Aging on the Toughness of Human Cortical Bone: Evaluation by R-Curves

    Energy Technology Data Exchange (ETDEWEB)

    Kinney, J

    2004-10-08

    Age-related deterioration of the fracture properties of bone, coupled with increased life expectancy, are responsible for increasing incidence of bone fracture in the elderly, and hence, an understanding of how its fracture properties degrade with age is essential. The present study describes ex vivo fracture experiments to quantitatively assess the effect of aging on the fracture toughness properties of human cortical bone in the longitudinal direction. Because cortical bone exhibits rising crack-growth resistance with crack extension, unlike most previous studies the toughness is evaluated in terms of resistance-curve (R-curve) behavior, measured for bone taken from wide range of age groups (34-99 years). Using this approach, both the ex vivo crack-initiation and crack-growth toughness are determined and are found to deteriorate with age; the initiation toughness decreases some 40% over six decades from 40 to 100 years, while the growth toughness is effectively eliminated over the same age range. The reduction in crack-growth toughness is considered to be associated primarily with a degradation in the degree of extrinsic toughening, in particular involving crack bridging in the wake of the crack.

  5. 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.

  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. 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.

  8. Changes in bone microstructure and toughness during the healing process of long bones

    Science.gov (United States)

    Ishimoto, T.; Nakano, T.; Umakoshi, Y.; Tabata, Y.

    2009-05-01

    It is of great importance to understand how bone defects regain the microstructure and mechanical function of bone and how the microstructure affects the mechanical function during the bone healing process. In the present study on long bone defects, we investigated the relationship between the recovery process of fracture toughness and biological apatite (BAp)/collagen (Col) alignment as an index of the bone microstructure to clarify the bone toughening mechanisms. A 5-mm defect introduced in the rabbit ulna was allowed to heal naturally and a three-point bending test was conducted on the regenerated site to assess bone toughness. The bone toughness was quite low at the early stage of bone regeneration but increased during the postoperative period. The change in toughness agreed well with the characteristics of the fracture surface morphology, which reflected the history of the crack propagation. SEM and microbeam X-ray diffraction analyses indicated that the toughness was dominated by the degree and orientation of the preferred BAp/Col alignment, i.e. bundles aligned perpendicular to the crack propagation clearly contributed to the bone toughening owing to extra energy consumption for resistance to crack propagation. In conclusion, regenerated bone improves fracture toughness by reconstructing the preferred BAp/Col alignment along the bone longitudinal axis during the healing process of long bones.

  9. 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.

  10. Mental toughness profiles and their relations with achievement goals and sport motivation in adolescent Australian footballers.

    Science.gov (United States)

    Gucciardi, Daniel F

    2010-04-01

    The aims of this study were to identify the mental toughness profiles of adolescent Australian footballers and to explore the relations between the mental toughness clusters and achievement goals and sport motivation. A total of 214 non-elite, male Australian footballers aged 16-18 years (mean = 16.8, s = 0.7) provided self-reports of mental toughness, achievement goals, and sport motivation. Cluster analysis supported the presence of two-groups in which players evidenced moderate and high levels of all four mental toughness subscales. Significant multivariate effects were observed for achievement goals and sport motivation with the high mental toughness group favouring both mastery- and performance-approach goals and self-determined as well as extrinsic motivational tendencies. The results suggest that adolescent Australian footballers' self-perceptions of mental toughness fall within two clusters involving high and moderate forms of all four components, and that these profiles show varying relations with achievement goals (particularly mastery-approach) and sport motivation.

  11. 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.

  12. That tough guy from Nazareth: A psychological assessment of Jesus

    Directory of Open Access Journals (Sweden)

    J. Harold Ellens

    2014-03-01

    Full Text Available Christmas gives us that ’sweet little Jesus Boy’ and Lent follows that with the ‘gentle Jesus, meek and mild.’ He was neither of those. In point of fact, he was the ‘tough guy from Nazareth.’ He was consistently abrasive, if not abusive, to his mother (Lk 2:49; Jn 2:4; Mt 12:48 and aggressively hard on males, particularly those in authority. In Mark 8 he cursed and damned Peter for failing to get Jesus’ esoteric definition of Messiah correct. Nobody else understood it either. Jesus had made it up himself and not adequately explained it to anybody until then. He called the religious authorities snakes, corrupt tombs, filthy chinaware, fakes, and Mosaic legalists who had forgotten God’s real revelation of universal grace and salvation in the Abraham Covenant. He tore up the temple in the middle of a worship service and cursed those present for turning God’s house of prayer into a den of thieves, when actually they were kind, helping out-of-town tourists obtain the proper sacrifices for the liturgical rituals. Jesus was persistently aggressive, often angry and not infrequently irrational, killing an innocent fig tree with his curse, for example. He constantly attacked the Pharisees and their proposals for renewing the spiritual vitality of the Jewish Community. He abused numerous people by healing them on the Sabbath just to make his political point against the religious leaders. He could just as well have healed them on Tuesday, if he really wanted to heal them. By healing the blind man in John 9 on the Sabbath, for example, he caused the man to be driven out of his synagogue, his family, and his community of faith; isolated and abandoned as if he were a leper. Even when he said surprising things about children, his focus was not on the children but on his disciples, using the children as tools for making an assertive teaching point. Jesus’ life was one of perpetually aggressive claims for his vision of God’s reign. He

  13. Evaluation of the cleavage fracture toughness of SA508 Gr. 4N low alloy steels in the transition region

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min-Chul; Lee, Bong-Sang (Nuclear Material Research Div., Korea Atomic Energy Research Inst., Daejeon (Korea)), e-mail: mckim@kaeri.re.kr; Lee, Ki-Hyoung (Dept. of Materials Science and Engineering, Daejeon (Korea))

    2009-07-01

    In this study, fracture toughness properties of several SA508 Gr.4N model alloys with different alloying elements contents were evaluated in the transition region. Moreover, effects of alloying elements and impurities on the transition properties of SA508 Gr.4N low alloy steels were investigated based on fractographs and micrographs. Fracture toughness tests were conducted following the ASTM standard E1921-05. All toughness data were size-corrected corresponding to those of 1T specimens

  14. Characterization of transition behavior in SA508 Gr.4N Ni-Cr-Mo low alloy steels with microstructural alteration by Ni and Cr contents

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki-Hyoung; Park, Sang-gyu [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of); Nuclear Materials Research Division, KAERI, Daejeon 305-353 (Korea, Republic of); Kim, Min-Chul, E-mail: mckim@kaeri.re.kr [Nuclear Materials Research Division, KAERI, Daejeon 305-353 (Korea, Republic of); 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)

    2011-11-25

    Highlights: {yields} We offer information for determining optimum alloying contents of SA508 Gr.4N steel. {yields} This study shows improvement of toughness with increasing Ni and Cr contents. {yields} Ni content is more effective on the impact toughness than on the fracture toughness. {yields} Cr content is more effective on the fracture toughness. {yields} We offer detailed information on relationship between toughness and microstructure. - Abstract: SA508 Gr.4N Ni-Cr-Mo low alloy steel, in which Ni and Cr contents are higher than in commercial reactor pressure vessel (RPV) steels, may be a candidate RPV material with the improved strength and toughness due to its tempered martensitic microstructure. This study aims at assessing the effects of microstructural factors with alloying element contents on the transition properties of Ni-Cr-Mo low alloy steels. Model alloys with different Ni and Cr contents were fabricated and their Charpy impact toughness and fracture toughness were examined in the transition region according to ASTM E23 and E1921 standard procedures, respectively. The test results showed extensive improvements of both impact toughness and fracture toughness with increasing Ni and Cr contents. However, Ni content was more effective on the impact toughness than on the fracture toughness, while Cr content was more effective on the fracture toughness. In order to identify a difference in effects of alloying elements contents on the fracture toughness and impact toughness, the relations between the transition properties and the scale of the microstructural features such as packets and carbides are discussed in detail.

  15. Effect of matrix toughness on fatigue life of plain woven carbon fabric composites

    Science.gov (United States)

    Nishikawa, Yasuhiro; Okubo, Kazuya; Fujii, Toru; Uenoya, Toshiyuki

    2001-08-01

    The effect of matrix toughness on the fatigue life of polymer matrix composites using plain woven carbon fabrics (pw-CFC) was studied. In order to vary the matrix toughness without changing the inherent cohesion properties such as adhesive strength between matrix and fibers, two different curing agents (acid anhydride and amine types) were used. Static tensile and tension/tension fatigue cyclic loads were applied to pw-CFC specimens. It was observed that the fatigue life was significantly affected by matrix toughness. During the fatigue tests, damage progression was observed intermittently by using a thermo-elastic stress analyzer (TSA). The stress re-distribution occurs due to fatigue damage progression. TSA can identify such stress re- distribution by means of detecting surface temperature amplitude. Highly fatigue-damaged area of pw-CFC was localized if the matrix toughness was high, although moderately damaged area grew all over the specimen. The experimental results indicate that the fatigue life and damage of pw-CFC are strongly governed by matrix toughness.

  16. Adhesive Through-Reinforcement Improves the Fracture Toughness of a Laminated Birch Wood Composite

    Directory of Open Access Journals (Sweden)

    Wenchang He

    2017-01-01

    Full Text Available In this paper we test the hypothesis that adhesive through-reinforcement in combination with glass-fibre reinforcement of adhesive bond lines will significantly improve the fracture toughness of a laminated birch wood composite. We test this hypothesis using a model composite consisting of perforated veneer that allowed a polyurethane adhesive to penetrate and reinforce veneers within the composite. Model composite specimens were tested for mode I fracture properties, and scanning electron microscopy was used to examine the microstructure of fracture surfaces. Our results clearly show that through-reinforcement, and also reinforcing adhesive bond lines with glass-fibre, significantly improved fracture toughness of the birch wood composite. Our results also indicate that improvements in fracture toughness depended on the level of reinforcement. Improvements in fracture toughness were related to the ability of the reinforcement to arrest crack development during fracture testing and the fibre bridging effect of glass-fibre in adhesive bond lines. We conclude that through-reinforcement is an effective way of improving the fracture toughness of laminated wood composites, but further research is needed to develop practical ways of creating such reinforcement in composites that more closely resemble commercial products.

  17. 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.

  18. The small punch assessment of toughness losses in low alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Bulloch, J.H. [ESB, Power Generation, Dublin (Ireland)

    1998-12-31

    The presentation deals at length with the relationship between the Small Punch, SP, test transition temperature Tsp, behaviour and those displayed by the conventional Charpy Fracture Appearance Transition Temperature, FATT, obtained from large test specimens. Essentially it was demonstrated that the total test temperature range trends could reasonably be described by a non-linear expression such as FATT varied inversely with the square of the Tsp. Finally when the Tsp against FATT trends were separated into different steel classes an encouraging picture emerged inasmuch that a reasonable amount of data exhibited good agreement with the predicted effects of grain size. Fractographic details were also discussed and strong effects of strain or loading rates were identified. (orig.) 19 refs.

  19. 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.

  20. Refinements to the Mixed-Mode Bending Test for Delamination Toughness

    Science.gov (United States)

    Reeder, James R.

    2000-01-01

    The mixed-mode bending (MMB) test for delamination toughness was first introduced in 1988. This simple test is a combination of the standard Mode I (opening) test and a Mode II (sliding) test. This MMB test has become widely used in the United States and around the world for mixed-mode toughness measurements. Because of the widespread use of this test method, it is being considered for standardization by ASTM Committee D30. This paper discusses several improvements to the original test method. The improvements to the MMB test procedure include an improved method for calculating toughness from the measured test quantities, a more accurate way of setting the mixed-mode ratio to be tested, and the inclusion of a new alignment criterion for improved consistency in measured values.

  1. 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.

  2. Using Small Punch tests in environment under static load for fracture toughness estimation in hydrogen embrittlement

    Science.gov (United States)

    Arroyo, B.; Álvarez, J. A.; Lacalle, R.; González, P.; Gutiérrez-Solana, F.

    2017-12-01

    In this paper, the response of three medium and high-strength steels to hydrogen embrittlement is analyzed by means of the quasi-non-destructive test known as the Small Punch Test (SPT). SPT tests on notched specimens under static load are carried out, applying Lacaclle’s methodology to estimate the fracture toughness for crack initiation, comparing the results to KIEAC fracture toughness obtained from C(T) precracked specimens tested in the same environment; SPT showed good correlation to standard tests. A novel expression was proposed to define the parameter KIEAC-SP as the suitable one to estimate the fracture toughness for crack initiation in hydrogen embrittlement conditions by Small Punch means, obtaining good accuracy in its estimations. Finally, Slow Rate Small Punch Tests (SRSPT) are proposed as a more efficient alternative, introducing an order of magnitude for the adequate rate to be employed.

  3. Practical and theoretical considerations on the fracture toughness testing of dental restorative materials.

    Science.gov (United States)

    Belli, Renan; Wendler, Michael; Zorzin, José I; Lohbauer, Ulrich

    2018-01-01

    An important tool in materials research, development and characterization regarding mechanical performance is the testing of fracture toughness. A high level of accuracy in executing this sort of test is necessary, with strict requirements given in extensive testing standard documents. Proficiency in quality specimen fabrication and test requires practice and a solid theoretical background, oftentimes overlooked in the dental community. In this review we go through some fundamentals of the fracture mechanics concepts that are relevant to the understanding of fracture toughness testing, and draw attention to critical aspects of practical nature that must be fulfilled for validity and accuracy in results. We describe our experience with some testing methodologies for CAD/CAM materials and discuss advantages and shortcomings of different tests in terms of errors in testing the applicability of the concept of fracture toughness as a single-value material-specific property. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  4. 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.

  5. Study on the microstructure and toughness of RPV SA508 class 3 steel weldments

    Energy Technology Data Exchange (ETDEWEB)

    Ko, J. H. [Korea Univesity of Technology and Education, Cheonan (Korea, Republic of); Gang, Y. H.; Joo, K. N.; Hwang, Y. H. [KAERI, Taejon (Korea, Republic of); Kim, J. T.; Kwon, H. K. [Doosan Heavy Industries and Construction Company, Chanwon (Korea, Republic of)

    2003-10-01

    The microstructures of RPV SA508 class 3 steel multipass weld metals with submerged arc welding process by varying the heat inputs of 2.4 and 3.6kJ/mm were investigated by optical and scanning electron microscopes. The microstructures were also compared between as-welded and postweld heat treatment conditions. The relationship between weld microstructures and toughness as well as hardness of weld metals was evaluated. The toughness was enhanced a little in the lower heat input of 2.4kJ/mm but the hardness of welds was decreased. The microstructures of welds made at the lower heat input used in this study consisted of a little higher proportion of acicular ferrite than those of welds made at the higher heat input(3.6kJ/mm), in which unfavorable microstructure to toughness such as grain boundary ferrite and banitic structure were increased.

  6. Controls on sill and dyke-sill hybrid geometry and propagation in the crust: The role of fracture toughness

    Science.gov (United States)

    Kavanagh, J. L.; Rogers, B. D.; Boutelier, D.; Cruden, A. R.

    2017-02-01

    Analogue experiments using gelatine were carried out to investigate the role of the mechanical properties of rock layers and their bonded interfaces on the formation and propagation of magma-filled fractures in the crust. Water was injected at controlled flux through the base of a clear-Perspex tank into superposed and variably bonded layers of solidified gelatine. Experimental dykes and sills were formed, as well as dyke-sill hybrid structures where the ascending dyke crosses the interface between layers but also intrudes it to form a sill. Stress evolution in the gelatine was visualised using polarised light as the intrusions grew, and its evolving strain was measured using digital image correlation (DIC). During the formation of dyke-sill hybrids there are notable decreases in stress and strain near the dyke as sills form, which is attributed to a pressure decrease within the intrusive network. Additional fluid is extracted from the open dykes to help grow the sills, causing the dyke protrusion in the overlying layer to be almost completely drained. Scaling laws and the geometry of the propagating sill suggest sill growth into the interface was toughness-dominated rather than viscosity-dominated. We define KIc* as the fracture toughness of the interface between layers relative to the lower gelatine layer KIcInt / KIcG. Our results show that KIc* influences the type of intrusion formed (dyke, sill or hybrid), and the magnitude of KIcInt impacted the growth rate of the sills. KIcInt was determined during setup of the experiment by controlling the temperature of the upper layer Tm when it was poured into place, with Tm intermediate hybrid structures.

  7. Effect of dentine depth on the fracture toughness of dentine-composite adhesive interfaces.

    Science.gov (United States)

    Tam, L E; Yim, D

    1997-01-01

    The fracture toughness test was recently introduced as a clinically relevant method for assessing the fracture resistance of the dentine-composite interface. The objective of this study was to evaluate the effect of dentine depth on the interfacial fracture toughness test of several dentine-composite interfaces using some new proprietary dentine bonding agents. Miniature short rod fracture toughness specimens containing a chevron-shaped dentine-composite-bonded interface were prepared for each group (n = 12). Six different dentine bonding agents and two dentine depths were the variables assessed at the dentine-composite interfaces. After 24 h at 37 degrees C in water, the specimens were tested by loading at 0.5 mm/min in the Instron Universal Testing Machine. The interfacial KIC results were analysed by ANOVA, unpaired Student's t-tests and Fisher's LSD test (P dentine, respectively, were: All-Bond 2, 0.80 (0.21), 0.44 (0.13); Bond-lt, 0.75 (0.20), 0.38 (0.19); Prime and Bond, 0.56 (0.11), 0.28 (0.10); Scotchbond Multi-Purpose, 0.45 (0.23), 0.26 (0.15); One-Step and OptiBond, insufficient results due to premature specimen failures. The results from this study should contribute to the development of the fracture toughness test as a method for assessing the integrity of the dentine-composite interface. The interfacial fracture toughness test determined significant differences among the different dentine bonding agents and between the superficial and deep dentine substrates. The dentine bonding agents showed significantly reduced interfacial fracture toughness results when bonding to deep versus superficial dentine.

  8. 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.

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

    Science.gov (United States)

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

    2014-06-01

    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 (KJQ) 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.

  10. Determination of interlaminar fracture toughness and fracture mode dependence of composites using the edge delamination test

    Science.gov (United States)

    Obrien, T. K.; Johnston, N. J.; Morris, D. H.; Simonds, R. A.

    1983-01-01

    Edge delamination testing has been conducted in order to determine the mixed mode interlaminar fracture toughness of unnotched (+, -35/0/90)s and (0/+, -35/90)s laminates with graphite fibers and epoxy matrices, with or without elastomer additives. Although the two stacking sequences were chosen so that the total strain energy release rates were equal, the percentages of crack opening and shear mode energy release rates were found to vary widely between the layups. Plots of interlaminar fracture toughness as a function of crack opening energy release rate percentage have been drawn to generate delamination failure criteria which reflect the observed fracture mode dependence.

  11. A new set of direct and iterative solvers for the TOUGH2 family of codes

    Energy Technology Data Exchange (ETDEWEB)

    Moridis, G.J. [Lawrence Berkeley Lab., CA (United States). Earth Sciences Div.

    1995-04-01

    Two new solvers are discussed. LUBAND, the first routine is a direct solver for banded systems and is based on a LU decomposition with partial pivoting and row interchange. BCGSTB, the second routine, is a Preconditioned Conjugate Gradient (PCG) solver with improved speed and convergence characteristics. Bandwidth minimization and gridblock ordering schemes are also introduced into TOUGH2 to improve speed and accuracy. TOUGH2 simulates fluid and heat flows in permeable media and is used for the evaluation of WIPP and TEVES (Thermal Enhanced Vapor Extraction System) that will be used to extract solvents from the Chemical Waste Landfill at Sandia National Laboratories.

  12. 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.

  13. 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

  14. Atomic and vibrational origins of mechanical toughness in bioactive cement during setting

    DEFF Research Database (Denmark)

    Tian, Kun V.; Yang, Bin; Yue, Yuanzheng

    2015-01-01

    testing, which is necessarily retrospective. Here we show quantitatively, through the novel use of calorimetry, terahertz (THz) spectroscopy and neutron scattering, how GIC’s developing fracture toughness during setting is related to interfacial THz dynamics, changing atomic cohesion and fluctuating...... interfacial configurations. Contrary to convention, we find setting is non-monotonic, characterized by abrupt features not previously detected, including a glass–polymer coupling point, an early setting point, where decreasing toughness unexpectedly recovers, followed by stress-induced weakening of interfaces...

  15. Fracture toughness of TiAl-Cr-Nb-Mo alloys produced via centrifugal casting

    Directory of Open Access Journals (Sweden)

    A. Brotzu

    2012-10-01

    Full Text Available Fracture toughness of a TiAl base intermetallic alloy has been investigated at room temperature. The Ti-48Al-2.5Cr-0.5Nb-2Mo (at. % alloy produced via centrifugal casting exhibits fine nearly lamellar microstructures, consisting mainly of fine lamellar grains, together with a very small quantity of residual β phases along lamellar colony boundaries. In order to determine the alloy fracture toughness compact tension specimens were tested and the results were compared with those available in literature.

  16. Recommendations for the shallow-crack fracture toughness testing task within the HSST (Heavy-Section Steel Technology) Program

    Energy Technology Data Exchange (ETDEWEB)

    Theiss, T.J. (Oak Ridge National Lab., TN (USA))

    1990-09-01

    Recommendations for Heavy-Section Steel Technology Program's investigation into the influence of crack depth on the fracture toughness of a steel prototypic of those in a reactor pressure vessel are included in this report. The motivation for this investigation lies in the fact that probabilistic fracture mechanics evaluations show that shallow flaws play a dominant role in the likelihood of vessel failure, and shallow-flaw specimens have exhibited an elevated toughness compared with conventional deep-notch fracture toughness specimens. Accordingly, the actual margin of safety of vessels may be greater than that predicted using existing deep-notch fracture-toughness results. The primary goal of the shallow-crack project is to investigate the influence of crack depth on fracture toughness under conditions prototypic of a reactor vessel. A limited data base of fracture toughness values will be assembled using a beam specimen of prototypic reactor vessel material and with a depth of 100 mm (4 in.). This will permit comparison of fracture-toughness data from deep-cracked and shallow-crack specimens, and this will be done for several test temperatures. Fracture-toughness data will be expressed in terms of the stress-intensity factor and crack-tip-opening displacement. Results of this investigation are expected to improve the understanding of shallow-flaw behavior in pressure vessels, thereby providing more realistic information for application to the pressurized-thermal shock issues. 33 refs., 17 figs.

  17. Effect of phase separation on the fracture toughness of SiO2–B2O3 ...

    Indian Academy of Sciences (India)

    –B2O3–Na2O system. The interface between the glass in glass separation enhances the fracture toughness. The increase in the connectivity of phase separated regions causes increase of fracture toughness from 0.98 through 1.43 to 1.54 ...

  18. Tissue-level leaf toughness, but not lamina thickness, predicts sapling leaf lifespan and shade tolerance of tropical tree species

    NARCIS (Netherlands)

    Kitajima, K.; Poorter, L.

    2010-01-01

    Leaf toughness is thought to enhance physical defense and leaf lifespan. Here, we evaluated the relative importance of tissue-level leaf traits vs lamina thickness, as well as their ontogenetic changes, for structure-level leaf toughness and regeneration ecology of 19 tropical tree species. We

  19. 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.

  20. Mental Toughness in Talented Youth Tennis Players : A Comparison Between on-Court Observations and a Self-Reported Measure

    NARCIS (Netherlands)

    Houwer, Ruben; Kramer, Tamara; den Hartigh, Ruud; Kolman, Nikki; Elferink-Gemser, Marije; Huijgen, Barbara

    In tennis, mental toughness is often considered highly important in achieving the elite level. The current study is the first to examine behavioural expressions of mental toughness on the court and their relationships with selfreported measures. Based on the input of five experienced tennis coaches

  1. An Improved Approach to Fracture Toughness Assessment of Brittle Coating on Ductile Substrate Systems under Indentation

    Science.gov (United States)

    Demidova, Natalia V.

    Fracture toughness is an important material property that determines the structural integrity of a component with pre-existing or service-generated flaws. In the present research, an indentation-based method and the associated fracture mechanics model are proposed for fracture toughness assessment of brittle coating/ductile substrate systems. The proposed models consider well-developed radial/median cracks generated under sharp indentation, despite that the crack formation process may have gone through crack initiation and propagation phases. For generality, the geometry of a well-developed crack is assumed to be semi-elliptical in shape. The driving force of the crack is considered to stem from the residual plastic zone expansion under the indenter, as well as the far-field Boussinesq (elastic) stress. Three well-defined configurations are studied. For the first configuration, a crack with a depth of less than 7% of the coating thickness is considered. In this case, the problem is treated as the one for the monolithic material with the coating material properties. For the second configuration, a crack that runs deeper than 7% of the coating thickness but is still within the coating layer is analyzed. In this case, the composite hardness is introduced into the analysis to account for the influence of the substrate material properties; and furthermore, an interface correction factor is proposed to take into account the presence of the coating/substrate interface and its influence on the stress intensity factor of the well-developed elliptical cracks. For the third configuration, a crack penetrating into the substrate is considered. In this case, based on the condition of deformation compatibility across the coating/substrate interface, the bulk modulus for the coating/substrate system is introduced into the analysis. A series of indentation tests are conducted on a WC/10Co/4Cr coating/1080 low carbon steel substrate specimen, which is a brittle coating on a ductile

  2. Performance enhancement of nylon/kevlar fiber composites through viscoelastically generated pre-stress

    OpenAIRE

    Fazal, A.; Fancey, K.S.

    2014-01-01

    Kevlar-29 fibers have high strength and stiffness but nylon 6,6 fibers have greater ductility. Thus by commingling these fibers prior to molding in a resin, the resulting hybrid composite may be mechanically superior to the corresponding single fiber-type composites. The contribution made by viscoelastically generated pre-stress, via the commingled nylon fibers, should add further performance enhancement. This paper reports on an initial study into the Charpy impact toughness and flexural sti...

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

    DEFF Research Database (Denmark)

    Dominy, N.J.; Grubb, P.J.; Jackson, R.V.

    2008-01-01

    Background and Aims: 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...... and Panama, fracture toughness was determined with an automated scissors apparatus using fully toughened leaves only. Key Results: 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, 13x 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...

  4. Lessons from Cacti: How to Survive the Prickles of Life during Tough Times

    Science.gov (United States)

    Bigger, Alan S.; Bigger, Linda B.

    2009-01-01

    The saguaro cactus looked a little like humans, in different shapes and sizes. How on earth do they survive in a climate that seems so inhospitable? It is possible to learn lessons for life from a cactus, if one can only get beyond the thorns, and that these lessons will assist one to survive during tough or prickly times. These plants survive…

  5. Toughness of natural rubber composites reinforced with hydrolyzed and modified wheat gluten aggregates

    Science.gov (United States)

    The toughness of natural rubber can be improved by using fillers for various rubber applications. Dry wheat gluten is a protein from wheat flour and is sufficiently rigid for rubber reinforcement. The wheat gluten was hydrolyzed to reduce its particle size and microfluidized to reduce and homogenize...

  6. Demonstration of the Trauma Nurses Talk Tough seat belt diversion program in North Carolina.

    Science.gov (United States)

    2014-03-01

    Trauma Nurses Talk Tough is a seat belt diversion program originally developed at the Legacy Emanuel Hospital in Portland, Oregon, in 1988. Attendance at the course is a condition for a one-time dismissal of a seat belt citation without fine or court...

  7. Advances in the TOUGH2 family of general-purpose reservoir simulators

    Energy Technology Data Exchange (ETDEWEB)

    Pruess, K.; Finsterle, S.; Moridis, G.; Oldenburg, C.; Antunez, E.; Wu, Y.S. [Lawrence Berkeley National Lab., CA (United States). Earth Sciences Div.

    1996-04-01

    TOUGH2 is a general-purpose fluid and heat flow simulators, with applications in geothermal reservoir engineering, nuclear waste disposal, and environmental contamination problems. This report summarizes recent developments which enhance the usability of the code, and provide a more accurate and comprehensive description of reservoir processes.

  8. Fracture Toughness of Thick Boride Layers Estimated by the Cross-Sectioned Scratch Test

    Science.gov (United States)

    Campos-Silva, I.; Flores-Jiménez, M.; Bravo-Bárcenas, D.; Rodríguez-Castro, G.; Martínez-Trinidad, J.; Meneses-Amador, A.

    2018-01-01

    New results about the fracture toughness (K c) of thick boride layers estimated by the cross-sectioned scratch test are presented in this study. The FeB-Fe2B layers developed at the surface of borided AISI 1018 and AISI 1045 steels and the Fe2B layer formed on the borided AISI 1045 steel exposed to a diffusion annealing process (DAP) were used for this purpose. The cross-sectioned scratch tests were performed with a Vickers diamond stylus drawn across the thick boride layer under a constant load to produce a half-cone-shaped fracture near to the top surface of the borided steels. The height of the half-cone-shaped fracture as a function of the cross-sectioned scratch loads was used to determine the fracture toughness of the FeB and Fe2B layers. The results showed a fracture resistance of ˜2.8 {MPa}√ m for the FeB layer formed at the surface of borided AISI 1045 steel. Likewise, the effect of the DAP on the surface of the borided AISI 1045 steel promoted the formation of an exclusively Fe2B layer, with an increase in the fracture toughness of the whole boride layer around 5 {MPa}√ m . Finally, the principle of the technique can be used to minimize the influence of the anisotropic properties on the fracture toughness along the depth of boride layers.

  9. New results on the relationship between hardness and fracture toughness of WC-Co hardmetal

    CSIR Research Space (South Africa)

    O'Quigley, DGF

    1996-05-01

    Full Text Available for the sake of comparison. If extrapolated, the two lines in Fig. 1 intersect the axes at different points. They intersect each other at Hv ~- 1300 kg mm and Klc ~ - 14.3 MPax/m. 4. Discussion Fig. 1 shows that the relationship between fracture toughness...

  10. The effects of aluminum or scandium on the toughness, density and ...

    African Journals Online (AJOL)

    The effects of the substitution of aluminum or scandium on the density, toughness as well as the stability of the phases formed by such an addition on platinum, iridium, rhodium and palladium metals were evaluated with the density functional quantum mechanical calculation methods. All the metals had four atoms per ...

  11. Generalized Fracture Toughness and Compressive Strength of Sustainable Concrete Including Low Calcium Fly Ash.

    Science.gov (United States)

    Golewski, Grzegorz Ludwik

    2017-12-06

    The paper presents the results of tests on the effect of the low calcium fly ash (LCFA) addition, in the amounts of: 0% (LCFA-00), 20% (LCFA-20) and 30% (LCFA-30) by weight of cement, on fracture processes in structural concretes. In the course of the experiments, compressive strength of concrete and fracture toughness for: I (tensile), II (in-plane shear) and III (anti-plane shear) models of cracking were measured. The tests determined the effect of age of concretes modified with LCFA on the analyzed parameters. The experiments were carried out after: 3, 7, 28, 90, 180 and 365 days of curing. Fracture toughness of concretes was determined in terms of the critical stress intensity factors: K I c S , K I I c , K I I I c and then a generalized fracture toughness K c was specified. The obtained results are significant for the analysis of concrete structures subjected to complex loading. The properties of composites with the additive of LCFA depend on the age of the concrete tested. Mature concretes exhibit high fracture toughness at 20% additive of LCFA, while the additive of LCFA in the amount of 30% weight of cement has a beneficial effect on the parameters of concrete only after half a year of curing.

  12. 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.

  13. The Influence of Specimen Type on Tensile Fracture Toughness of Rock Materials

    Science.gov (United States)

    Aliha, Mohammad Reza Mohammad; Mahdavi, Eqlima; Ayatollahi, Majid Reza

    2017-03-01

    Up to now, several methods have been proposed to determine the mode I fracture toughness of rocks. In this research, different cylindrical and disc shape samples, namely: chevron bend (CB), short rod (SR), cracked chevron notched Brazilian disc (CCNBD), and semi-circular bend (SCB) specimens were considered for investigating mode I fracture behavior of a marble rock. It is shown experimentally that the fracture toughness values of the tested rock material obtained from different test specimens are not consistent. Indeed, depending on the geometry and loading type of the specimen, noticeable discrepancies can be observed for the fracture toughness of a same rock material. The difference between the experimental mode I fracture resistance results is related to the magnitude and sign of T-stress that is dependent on the geometry and loading configuration of the specimen. For the chevron-notched samples, the critical value of T-stress corresponding to the critical crack length was determined using the finite element method. The CCNBD and SR specimens had the most negative and positive T-stress values, respectively. The dependency of mode I fracture resistance to the T-stress was shown using the extended maximum tangential strain (EMTSN) criterion and the obtained experimental rock fracture toughness data were predicted successfully with this criterion.

  14. 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)

  15. Generalized Fracture Toughness and Compressive Strength of Sustainable Concrete Including Low Calcium Fly Ash

    Directory of Open Access Journals (Sweden)

    Grzegorz Ludwik Golewski

    2017-12-01

    Full Text Available The paper presents the results of tests on the effect of the low calcium fly ash (LCFA addition, in the amounts of: 0% (LCFA-00, 20% (LCFA-20 and 30% (LCFA-30 by weight of cement, on fracture processes in structural concretes. In the course of the experiments, compressive strength of concrete and fracture toughness for: I (tensile, II (in-plane shear and III (anti-plane shear models of cracking were measured. The tests determined the effect of age of concretes modified with LCFA on the analyzed parameters. The experiments were carried out after: 3, 7, 28, 90, 180 and 365 days of curing. Fracture toughness of concretes was determined in terms of the critical stress intensity factors: K I c S , K I I c , K I I I c and then a generalized fracture toughness K c was specified. The obtained results are significant for the analysis of concrete structures subjected to complex loading. The properties of composites with the additive of LCFA depend on the age of the concrete tested. Mature concretes exhibit high fracture toughness at 20% additive of LCFA, while the additive of LCFA in the amount of 30% weight of cement has a beneficial effect on the parameters of concrete only after half a year of curing.

  16. Fracture toughness and fatigue crack growth of oxide dispersion strengthened copper

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, D.J.; Gieseke, B.G. [Oak Ridge National Laboratory, TN (United States)

    1996-04-01

    The fracture toughness and fatigue crack growth behavior of copper dispersion strengthened with aluminum oxide (0.15 wt % Al) was examined. In the unirradiated condition, the fracture toughness was about 45 kJ/m{sup 2} (73 MPa{radical}m) at room temperature, but decreased significantly to only 3 Kj/m{sup 2} (20 MPa{radical}m), at 250{degrees}C. After irradiation at approximately 250{degrees}C to about 2.5 displacements per atom (dpa), the toughness was very low, about 1 kJ/m{sup 2} (48 MOa{radical}m), and at 250{degrees}C the toughness was very low, about 1kJ/m{sup 2} (12 mPa{radical}m). The fatigue crack growth rate of unirradiated material at room temperature is similiar to other candidate structural alloys such as V-4Cr-4Ti and 316L stainless steel. The fracture properties of this material at higher temperatures and in controlled environments need further investigation, in both irradiated and unirradiated conditions.

  17. How Tough is Human Cortical Bone? In-Situ Measurements on Realistically Short Cracks

    Energy Technology Data Exchange (ETDEWEB)

    Ritchie, Robert O; Koester, K. J.; Ager III, J. W.; Ritchie, R.O.

    2008-05-10

    Bone is more difficult to break than to split. Although this is well known, and many studies exist on the behavior of long cracks in bone, there is a need for data on the orientation-dependent crack-growth resistance behavior of human cortical bone which accurately assesses its toughness at appropriate size-scales. Here we use in-situ mechanical testing in the scanning electron microscope and x-ray computed tomography to examine how physiologically-pertinent short (<600 mu m) cracks propagate in both the transverse and longitudinal orientations in cortical bone, using both crack-deflection/twist mechanics and nonlinear-elastic fracture mechanics to determine crack-resistance curves. We find that after only 500 mu m of cracking, the driving force for crack propagation was more than five times higher in the transverse (breaking) direction than in the longitudinal (splitting) direction due to major crack deflections/twists principally at cement sheathes. Indeed, our results show that the true transverse toughness of cortical bone is far higher than previously reported. However, the toughness in the longitudinal orientation, where cracks tend to follow the cement lines, is quite low at these small crack sizes; it is only when cracks become several millimeters in length that bridging mechanisms can develop leading to the (larger-crack) toughnesses generally quoted for bone.

  18. Fracture toughness of irradiated wrought and cast austenitic stainless steels in BWR environment

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O.K.; Gruber, E.E.; Shack, W.J. [Argonne National Lab., Nuclear Engineering Div., Argonne, Illinois (United States)

    2007-07-01

    Experimental data are presented on the fracture toughness of wrought and cast austenitic stainless steels (SSs) that were irradiated to a fluence of {approx} 1.5 x 10{sup 21} n/cm{sup 2} (E > 1 MeV){sup *} ({approx} 2.3 dpa) at 296-305{sup 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 {approx} 289{sup 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)

  19. Face/core mixed mode debond fracture toughness characterization using the modified TSD test method

    DEFF Research Database (Denmark)

    Berggreen, Christian; Quispitupa, Amilcar; Costache, Andrei

    2014-01-01

    The modified tilted sandwich debond (TSD) test method is used to examine face/core debond fracture toughness of sandwich specimens with glass/polyester face sheets and PVC H45 and H100 foam cores over a large range of mode-mixities. The modification was achieved by reinforcing the loaded face she...

  20. Evaluation of Fracture Toughness of Tantalum Carbide Ceramic Layer: A Vickers Indentation Method

    Science.gov (United States)

    Song, Ke; Xu, Yunhua; Zhao, Nana; Zhong, Lisheng; Shang, Zhao; Shen, Liuliu; Wang, Juan

    2016-07-01

    A tantalum carbide (TaC) ceramic layer was produced on gray cast iron matrix by in situ technique comprising a casting process and a subsequent heat treatment at 1135 °C for 45 min. Indentation fracture toughness in TaC ceramic layer was determined by the Vickers indentation test for various loads. A Niihara approach was chosen to assess the fracture toughness of TaC ceramic layer under condition of the Palmqvist mode in the experiment. The results reveal that K IC evaluation of TaC ceramic layer by the Vickers indentation method strongly depends on the selection of crack system and K IC equations. The critical indentation load for Vickers crack initiation in TaC ceramic layer lies between 1 and 2 N and the cracks show typical intergranular fracture characteristics. Indentation fracture toughness calculated by the indentation method is independent of the indentation load on the specimen. The fracture toughness of TaC ceramic layer is 6.63 ± 0.34 MPa m1/2, and the toughening mechanism is mainly crack deflection.

  1. Comparison of Mental Toughness and Power Test Performances in High-Level Kickboxers by Competitive Success

    National Research Council Canada - National Science Library

    Slimani, Maamer; Miarka, Bianca; Briki, Walid; Cheour, Foued

    2016-01-01

    .... Thirty two high-level male kickboxers (winner = 16 and loser = 16: 21.2 ± 3.1 years, 1.73 ± 0.07 m, and 70.2 ± 9.4 kg) were analyzed using the CMJ, MBT tests and sports mental toughness questionnaire...

  2. Roughness effects on the critical fracture toughness of materials under uniaxial stress

    NARCIS (Netherlands)

    Palasantzas, George

    1998-01-01

    The Griffith criterion is applied for the calculation of the critical fracture toughness upon which the formation of a rough self-affine crack (which is characterized by the rms roughness amplitude σ, the correlation length ξ, and the roughness exponent H) commences. For large crack sizes R»ξ, the

  3. The concept of fatigue fracture toughness in fatigue delamination growth behavior

    NARCIS (Netherlands)

    Yao, L.; Alderliesten, R.C.; Benedictus, R.

    2015-01-01

    This paper provides a study on mode I fatigue delamination growth in composite laminates using energy principles. Experimental data has been obtained from fatigue tests conducted on Double Cantilever Beam (DCB) specimens at various stress ratios. A concept of fatigue fracture toughness is proposed

  4. Crack growth rates and fracture toughness of irradiated austenitic stainless steels in BWR environments.

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O. K.; Shack, W. J.

    2008-01-21

    In light water reactors, austenitic stainless steels (SSs) are used extensively as structural alloys in reactor core internal components because of their high strength, ductility, and fracture toughness. However, exposure to high levels of neutron irradiation for extended periods degrades the fracture properties of these steels by changing the material microstructure (e.g., radiation hardening) and microchemistry (e.g., radiation-induced segregation). Experimental data are presented on the fracture toughness and crack growth rates (CGRs) of wrought and cast austenitic SSs, including weld heat-affected-zone materials, that were irradiated to fluence levels as high as {approx} 2x 10{sup 21} n/cm{sup 2} (E > 1 MeV) ({approx} 3 dpa) in a light water reactor at 288-300 C. The results are compared with the data available in the literature. The effects of material composition, irradiation dose, and water chemistry on CGRs under cyclic and stress corrosion cracking conditions were determined. A superposition model was used to represent the cyclic CGRs of austenitic SSs. The effects of neutron irradiation on the fracture toughness of these steels, as well as the effects of material and irradiation conditions and test temperature, have been evaluated. A fracture toughness trend curve that bounds the existing data has been defined. The synergistic effects of thermal and radiation embrittlement of cast austenitic SS internal components have also been evaluated.

  5. Tough Supramolecular Hydrogel Based on Strong Hydrophobic Interactions in a Multiblock Segmented Copolymer

    Science.gov (United States)

    2017-01-01

    We report the preparation and structural and mechanical characterization of a tough supramolecular hydrogel, based exclusively on hydrophobic association. The system consists of a multiblock, segmented copolymer of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic dimer fatty acid (DFA) building blocks. A series of copolymers containing 2K, 4K, and 8K PEG were prepared. Upon swelling in water, a network is formed by self-assembly of hydrophobic DFA units in micellar domains, which act as stable physical cross-link points. The resulting hydrogels are noneroding and contain 75–92 wt % of water at swelling equilibrium. Small-angle neutron scattering (SANS) measurements showed that the aggregation number of micelles ranges from 2 × 102 to 6 × 102 DFA units, increasing with PEG molecular weight. Mechanical characterization indicated that the hydrogel containing PEG 2000 is mechanically very stable and tough, possessing a tensile toughness of 4.12 MJ/m3. The high toughness, processability, and ease of preparation make these hydrogels very attractive for applications where mechanical stability and load bearing features of soft materials are required. PMID:28469284

  6. Enhancing Scalability and Efficiency of the TOUGH2_MP for LinuxClusters

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Keni; Wu, Yu-Shu

    2006-04-17

    TOUGH2{_}MP, the parallel version TOUGH2 code, has been enhanced by implementing more efficient communication schemes. This enhancement is achieved through reducing the amount of small-size messages and the volume of large messages. The message exchange speed is further improved by using non-blocking communications for both linear and nonlinear iterations. In addition, we have modified the AZTEC parallel linear-equation solver to nonblocking communication. Through the improvement of code structuring and bug fixing, the new version code is now more stable, while demonstrating similar or even better nonlinear iteration converging speed than the original TOUGH2 code. As a result, the new version of TOUGH2{_}MP is improved significantly in its efficiency. In this paper, the scalability and efficiency of the parallel code are demonstrated by solving two large-scale problems. The testing results indicate that speedup of the code may depend on both problem size and complexity. In general, the code has excellent scalability in memory requirement as well as computing time.

  7. Apical bud toughness tests and tree sway movements to examine crown abrasion: preliminary results

    Science.gov (United States)

    Tyler Brannon; Wayne Clatterbuck

    2012-01-01

    Apical bud toughness differences were examined for several species to determine if crown abrasion affects shoot growth of determinate and indeterminate species during stand development. Determinate buds will set and harden after initial shoot elongation in the spring, while the indeterminate shoots form leaves from the apical meristem continuously based on the...

  8. A study on electrochemical evaluation method of toughness degradation for 12%Cr steel (II)

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Chang Hui; Yoon, Kee Bong [Chungang Univ., Seoul (Korea, Republic of); Seo, Hyun Uk [Hyosung Power and Industrial, Seoul (Korea, Republic of); Park, Ki Sung; Kim, Seoung Tae [Korea Plant Service and Engineering Co., Ltd., Seongnam (Korea, Republic of)

    2001-07-01

    Fossil power plants operated in high temperature condition are composed of components such as turbine, boiler, and piping system. Among these components, turbine blades made with 12%Cr steel operate at a temperature above 500 .deg. C. Due to the long term service, turbine blades experience material degradation manifested by change in mechanical and microstructural properties. The need to make life assessment and to evaluate material degradation of turbine blade is strongly required but in reality, there is a lack of knowledge in defining failure mechanism and fundamental data for this component. Therefore, in making life assessment of turbine blade, evaluation of material degradation must be a priority. For this purpose, evaluation of toughness degradation is very important. The major cause of toughness degradation in 12Cr turbine blade is reported to be critical corrosion pitting induced by segregation of impurity elements(P etc.), coarsening of carbide, and corrosion, but the of materials for in-service application. in this study, the purpose of research is focused on evaluating toughness degradation with respect to operation time for 12%Cr steel turbine blade under high temperature steam environment and quantitatively detecting the degradation properties which is the cause of toughness degradation by means of non-destructive method, electrochemical polarization.

  9. User's Guide for Hysteretic Capillary Pressure and Relative Permeability Functions in TOUGH2

    Energy Technology Data Exchange (ETDEWEB)

    Doughty, C. A.

    2013-03-01

    This document provides a user’s guide for the most recent version of the hysteretic code, which runs within iTOUGH2 (Finsterle, 1999a,b,c) or TOUGH2 V2.1 (Pruess et al., 2012). The usage of the hysteretic module is the same in both codes, which for brevity here are both referred to simply as TOUGH2. The current code differs only slightly from what was presented in Doughty (2007), hence that document provides the basic information on the processes being modeled and how they are conceptualized. This document focuses on a description of the user-specified parameters required to run hysteretic TOUGH2. In the few instances where the conceptualization differs from that of Doughty (2007), the features described here are the current ones. Sample problems presented in this user’s guide use the equation-of-state module ECO2N (Pruess, 2005). The components present in ECO2N are H{sub 2}O, NaCl, and CO{sub 2}. Two fluid phases and one solid phase are considered: an aqueous phase, which primarily consists of liquid H{sub 2}O and may contain dissolved NaCl and CO{sub 2}; a supercritical phase which primarily consists of CO{sub 2}, but also includes a small amount of gaseous H{sub 2}O; and a solid phase consisting of precipitated NaCl. Details of the ECO2N formulation may be found in Pruess (2005). The aqueous phase is the wetting phase and is denoted ‘liquid’, whereas the supercritical phase is the non-wetting phase and is denoted ‘gas’. The hysteretic formalism may be applied to other TOUGH2 equation-of-state modules that consider two fluid phases, as long as the liquid phase is the wetting phase and the gas phase is the non-wetting phase.

  10. 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.

  11. Degradation of Polymeric Material used for Osteosynthesis and Comparison of Fracture Toughness Between Test and FEA

    Directory of Open Access Journals (Sweden)

    Bijoy Paul

    2017-08-01

    Full Text Available Biodegradable polymers such as PLA, PGA, PLGA etc., inside the human body often pose a tough challenge for the orthopedic doctors and material scientists. Unlike metallic or ceramic implants, where deterioration of the mechanical properties has never been an issue, biodegradable polymeric implants, used for Osteosynthesis, deteriorate while the fractured bone is subjected to kinesiological stress during healing process. To understand how biodegradable materials lose its mechanical properties, an investigation into the influence of degradation process on Mode-I fracture toughness of poly (lactide-co-glycolide, PLGA 85:15 material was initiated. The objective of this study was to build an improved understanding of the deterioration of biodegradable polymers mechanical properties during in-vitro degradation and how this change may affect long term in-vivo performance of the implants. A simple mathematical relationship was established to understand the change in the Young’s modulus during the degradation process. Compact tension specimens were designed and molded for mode-I fracture criterion and then put in 3% concentrated Hydrogen peroxide (H2O2 to study the degradation process. FEA (Finite Element Analysis was used to study the change in mechanical properties and then the results were compared with the physical test. Mode-I fracture toughness, KIC was measured and the behavior of the polymer was also identified. It was seen that the fracture toughness, KIC of PLGA 85:15 decreased with the progression of degradation. Finally, it was concluded that an increase in the Young’s modulus made PLGA 85:15 very brittle and hence resulted in reduced fracture toughness.

  12. Fracture Toughness of Nanohybrid and Hybrid Composites Stored Wet and Dry up to 60 Days

    Directory of Open Access Journals (Sweden)

    Sookhakiyan M

    2017-03-01

    Full Text Available Statement of Problem: Patients’ demand for tooth-colored restoratives in the posterior region is increasing. Clinicians use universal nanohybrid resin composites for both anterior and posterior regions. There are few published reports comparing fracture toughness of nonohybrids and that of hybrid composite stored wet and dry. Objectives: To investigate the fracture toughness of three nanohybrids compared to that of a hybrid resin composite stored dry or wet up to 60 days, using four- point bending test. Materials and Methods: Four resin composites were used: three nanohybrids; Filtek Supreme (3M, Ice (SDI, TPH3 (Dentsply and one hybrid Filtek P60 (3M. For each material, 40 rectangular notched beam specimens were prepared with dimensions of 30 mm × 5mm × 2mm. The specimens were randomly divided into 4 groups (n = 10 and stored at 37ºC either in distilled water or dry for 1 and 60 days. The specimens were placed on the four-point test jig and subjected to force (N using universal testing machine loaded at a crosshead speed of 0.5mm/min and maximum load at specimen failure was recorded and KIc was calculated. Results: Three-way ANOVA showed a significant interaction between all the factors (all p < .0001. Except for TPH3, all tested materials showed significantly higher KIc when stored dry than stored wet (p < 0.05. After 1 day of dry storage, Ice showed the highest KIc (2.04 ± 0.32 followed by Filtek P60 and the lowest was for Filtek Supreme (1.39 ± 0.13. The effect of time on fracture toughness was material dependent. Conclusions: Wet storage adversely affected the fracture toughness of almost all materials. Keeping the restoration dry in the mouth may increase their fracture toughness. Therefore, using a coating agent on the surface of restoration may protect them from early water uptake and increase their strength during a time period.

  13. Reference point indentation is not indicative of whole mouse bone measures of stress intensity fracture toughness.

    Science.gov (United States)

    Carriero, Alessandra; Bruse, Jan L; Oldknow, Karla J; Millán, José Luis; Farquharson, Colin; Shefelbine, Sandra J

    2014-12-01

    Bone fragility is a concern for aged and diseased bone. Measuring bone toughness and understanding fracture properties of the bone are critical for predicting fracture risk associated with age and disease and for preclinical testing of therapies. A reference point indentation technique (BioDent) has recently been developed to determine bone's resistance to fracture in a minimally invasive way by measuring the indentation distance increase (IDI) between the first and last indentations over cyclic indentations in the same position. In this study, we investigate the relationship between fracture toughness KC and reference point indentation parameters (i.e. IDI, total indentation distance (TID) and creep indentation distance (CID)) in bones from 38 mice from six types (C57Bl/6, Balb, oim/oim, oim/+, Phospho1(-/-) and Phospho1 wild type counterpart). These mice bone are models of healthy and diseased bone spanning a range of fracture toughness from very brittle (oim/oim) to ductile (Phospho1(-/-)). Left femora were dissected, notched and tested in 3-point bending until complete failure. Contralateral femora were dissected and indented in 10 sites of their anterior and posterior shaft surface over 10 indentation cycles. IDI, TID and CID were measured. Results from this study suggest that reference point indentation parameters are not indicative of stress intensity fracture toughness in mouse bone. In particular, the IDI values at the anterior mid-diaphysis across mouse types overlapped, making it difficult to discern differences between mouse types, despite having extreme differences in stress intensity based toughness measures. When more locations of indentation were considered, the normalised IDIs could distinguish between mouse types. Future studies should investigate the relationship of the reference point indentation parameters for mouse bone in other material properties of the bone tissue in order to determine their use for measuring bone quality. Copyright © 2014

  14. 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.

  15. Interfacial fracture toughness of different resin cements bonded to a lithium disilicate glass ceramic.

    Science.gov (United States)

    Hooshmand, Tabassom; Rostami, Golriz; Behroozibakhsh, Marjan; Fatemi, Mostafa; Keshvad, Alireza; van Noort, Richard

    2012-02-01

    To evaluate the effect of HF acid etching and silane treatment on the interfacial fracture toughness of a self-adhesive and two conventional resin-based cements bonded to a lithium disilicate glass ceramic. Lithium disilicate glass ceramic discs were prepared with two different surface preparations consisting of gritblasted with aluminium oxide, and gritblasted and etched with hydrofluoric acid. Ceramic surfaces with a chevron shaped circular hole were treated by an optimized silane treatment followed by an unfilled resin and then three different resin cements (Variolink II, Panavia F2, and Multilink Sprint). Specimens were kept in distilled water at 37°C for 24h and then subjected to thermocycling. The interfacial fracture toughness was measured and mode of failures was also examined. Data were analysed using analysis of variance followed by T-test analysis. No statistically significant difference in the mean fracture toughness values between the gritblasted and gritblasted and etched surfaces for Variolink II resin cement was found (P>0.05). For the gritblasted ceramic surfaces, no significant difference in the mean fracture toughness values between Panavia F2 and Variolink II was observed (P>0.05). For the gritblasted and etched ceramic surfaces, a significantly higher fracture toughness for Panavia F2 than the other cements was found (Pcements demonstrated a better bonding efficacy to the lithium disilicate glass ceramic compared to the self-adhesive resin cement. The lithium disilicate glass ceramic surfaces should be gritblasted and etched to get the best bond when used with Panavia F2 and Multilink Sprint resin cements, whereas for the Variolink II only gritblasting is required. The best bond overall is achieved with Panavia F2. Copyright © 2011 Elsevier Ltd. All rights reserved.

  16. Interfacial toughness of bilayer dental ceramics based on a short-bar, chevron-notch test.

    Science.gov (United States)

    Anunmana, Chuchai; Anusavice, Kenneth J; Mecholsky, John J

    2010-02-01

    The objective of this study was to test the null hypothesis that the interfacial toughness of each of two types of bonded core-veneer bilayer ceramics is not significantly different from the apparent fracture toughness of the control monolithic glass veneer. T-shaped short-bars of a lithia-disilicate glass-ceramic core (LC) and yttria-stabilized polycrystalline zirconia core ceramic (ZC) were prepared according to the manufacturer's recommendations. V-shaped notches were prepared by using 25-mum-thick palladium foil, leaving the chevron-notch area exposed, and the bars were veneered with a thermally compatible glass veneer (LC/GV and ZC/GV). Additionally, we also bonded the glass veneer to itself as a control group (GV/GV). Specimens were kept in distilled water for 30 days before testing in tension. Eight glass veneer bars were prepared for the analysis of fracture toughness test using the indentation-strength technique. The mean interfacial toughness of the LC/GV group was 0.69 MPam(1/2) (0.11), and did not significantly differ from that of the GV/GV control group, 0.74 MPam(1/2) (0.17) (p>0.05). However, the difference between the mean interfacial toughness of the ZC/GV group, 0.13 MPam(1/2) (0.07), and the LC/GV and the GV/GV groups was statistically significant (pveneering ceramics are the weakest link in the design of the structure. Since all-ceramic restorations often fail from chipping of veneer layers or crack initiation at the interface, the protective effects of thermal mismatch stresses oral prosthesis design should be investigated. Copyright 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  17. A fast and robust TOUGH2 module to simulate geological CO2 storage in saline aquifers

    Science.gov (United States)

    Shabani, Babak; Vilcáez, Javier

    2018-02-01

    A new TOUGH2 module to simulate geological CO2 storage (GCS) in saline aquifers is developed based on the widely employed ECO2N module of TOUGH2. The newly developed TOUGH2 module uses a new non-iterative fugacity-activity thermodynamic model to obtain the partitioning of CO2 and H2O between the aqueous and gas phases. Simple but robust thermophysical correlations are used to obtain density, viscosity, and enthalpy of the gas phase. The implementation and accuracy of the employed thermophysical correlations are verified by comparisons against the national institute of standards and technology (NIST) online thermophysical database. To assess the computation accuracy and efficiency, simulation results obtained with the new TOUGH2 module for a one-dimensional non-isothermal radial and a three-dimensional isothermal system are compared against the simulation results obtained with the ECO2N module. Treating salt mass fraction in the aqueous phase as a constant, along with the inclusion of a non-iterative fugacity-activity thermodynamic model, and simple thermophysical correlations, resulted in simulations much faster than simulations with ECO2N module, without losing numerical accuracy. Both modules yield virtually identical results. Additional field-scale simulations of CO2 injection into an actual non-isothermal and heterogeneous geological formation confirmed that the new module is much faster than the ECO2N module in simulating complex field-scale conditions. Owing to its capability to handle CO2-CH4-H2S-N2 gas mixtures and its compatibility with TOUGHREACT, this new TOUGH2 module offers the possibility of developing a fast and robust TOUGHREACT module to predict the fate of CO2 in GCS sites under biotic conditions where CO2, CH4, H2S, and N2 gases can be formed.

  18. Impact strength of Luehea divaricata wood on different moisture conditions

    Directory of Open Access Journals (Sweden)

    Clovis Roberto Haselein

    2010-12-01

    Full Text Available This study aimed to compare the impact strength of Luehea divaricata wood tested under conditions of equilibrium at 12% and saturated moisture content. Trees from two different physiographic regions of Rio Grande do Sul state were used. The specimens were submitted to the impact using a pendulum of Charpy and evaluated with relationship to the resistance offered to the application of the load in the radial and tangential plans and with the positions in the log (pith - bark for the two physiographic regions at each moisture condition. Also the specific gravity at 12% moisture content and in saturated conditions, the moisture content, the work absorbed, the impact strength, coefficient of resilience and dynamic quota were determined. The results showed that the Luehea divaricata in saturated wood, presented greater strength, indicating that the specie is more resistant to the impact when it is green than when it is at 12% moisture content.

  19. Effect of Zr Addition on the Microstructure and Toughness of Coarse-Grained Heat-Affected Zone with High-Heat Input Welding Thermal Cycle in Low-Carbon Steel

    Science.gov (United States)

    Shi, Ming-hao; Yuan, Xiao-guang; Huang, Hong-jun; Zhang, Si

    2017-07-01

    Microstructures and toughness of coarse-grained heat-affected zone (CGHAZ) with high-heat input welding thermal cycle in Zr-containing and Zr-free low-carbon steel were investigated by means of welding thermal cycle simulation. The specimens were subjected to a welding thermal cycle with heat inputs of 100, 400, and 800 kJ cm-1 at peak temperature of 1673 K (1400 °C) using a thermal simulator. The results indicate that excellent impact toughness at the CGHAZ was obtained in Zr-containing steel. The Zr oxide is responsible for AF transformation, providing the nucleation site for the formation AF, promoting the nucleation of AF on the multi-component inclusions. High fraction of acicular ferrite (AF) appears in Zr-containing steel, acting as an obstacle to cleavage propagation due to its high-angle grain boundary. The morphology of M-A constituents plays a key role in impact toughness of CGHAZ. Large M-A constituents with lath form can assist the micro-crack initiation and seriously decrease the crack initiation energy. The relationship of AF transformation and M-A constituents was discussed in detail.

  20. 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%.

  1. Flexural Toughness of Steel Fiber Reinforced High Performance Concrete Containing Nano-SiO2 and Fly Ash

    Science.gov (United States)

    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%. PMID:24883395

  2. Results of irradiated cladding tests and clad plate experiments

    Energy Technology Data Exchange (ETDEWEB)

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

    1988-01-01

    Two aspects critical to the fracture behavior of three-wire stainless steel cladding were investigated by the Heavy-Section Steel Technology (HSST) Program: (1) radiation effects on cladding strength and toughness, and (2) the response of mechanically loaded, flawed structures in the presence of cladding (clad plate experiments). Postirradiation testing results show that, in the test temperature range from /minus/125 to 288/degree/C, the yield strength increased, and ductility insignificantly increased, while there was almost no change in ultimate tensile strength. All cladding exhibited ductile-to-brittle transition behavior during Charpy impact testing. Radiation damage decreased the Charpy upper-shelf energy by 15 to 20% and resulted in up to 28/degree/C shifts of the Charpy impact transition temperature. Results of irradiated 12.5-mm-thick compact specimens (0.5TCS) show consistent decreases in the ductile fracture toughness, J/sub Ic/, and the tearing modulus. Results from clad plate tests have shown that (1) a tough surface layer composed of cladding and/or heat-affected zone has arrested running flaws under conditions where unclad plates have ruptured, and (2) the residual load-bearing capacity of clad plates with large subclad flaws significantly exceeded that of an unclad plate. 13 figs., 1 tab.

  3. A study on the evaluation of the fracture toughness for the narrow gap welding part of nuclear piping

    Energy Technology Data Exchange (ETDEWEB)

    Huh, Yong; Shin, In Hwan; Seok, Chang Sung [Sungkyunkwan University, Suwon (Korea, Republic of); Yang, Jun Seog [Korea Electric Power Research Institute, Daejeon (Korea, Republic of)

    2009-07-01

    The fracture toughness for the LBB analysis of the piping is generally determined by the J-integral according to ASTM E1820. However, since this evaluates a base metal, the fracture toughness for narrow gap welding can be lower than the real value. In this study, we evaluated the plastic {eta}-factor of the narrow gap welding part of a nuclear piping with SA508 Cl.la and SA312 TP316. Also, we have performed the fracture toughness test for the narrow gap welding part and applied the new plastic {eta}-factor equation by Huh, et al. and then compared the results with those according to ASTM standard.

  4. A Study on the Evaluation of the Fracture Toughness for the Narrow Gap Welding Part of Nuclear Piping

    Energy Technology Data Exchange (ETDEWEB)

    Huh, Yong; Park, Soo; Shin, In Hwan; Seok, Chang Sung [Sungkyunkwan University, Seoul (Korea, Republic of); Yang, Jun Seog [KEPRI, Daejeon (Korea, Republic of)

    2010-01-15

    The fracture toughness for the LBB analysis of piping is generally determined by the J-integral according to ASTM E1820. However, since this evaluates a base metal, the fracture toughness for narrow gap welding can be differently than the real value. This study evaluated the plastic {eta} factor of the narrow gap welding part of a nuclear piping with SA508 Cl.1a and SA312 TP316. Also, it performed the fracture toughness test for the narrow gap welding part and applied the new plastic {eta} factor equation by Huh, et al. and then compared the results with those according with the ASTM standard.

  5. 'When the going gets tough, the tough get going': social indetification and individual effort in group competition

    NARCIS (Netherlands)

    Ouwerkerk, J.W.; de Gilder, T.C.; de Vries, N.K.

    2000-01-01

    Based on social identity theory, the authors predicted that in ongoing intergroup competition, people’s strength of social identification will have a positive impact on their behavioral efforts on behalf of an ingroup when its current status is low, whereas this will not be the case when its current

  6. When the going gets tough, the tough get going: Social identification and individual effort in intergroup competition.

    NARCIS (Netherlands)

    Ouwerkerk, J.W.; de Gilder, T.C.; de Vries, N.K.

    2000-01-01

    Based on social identity theory, the authors predicted that in ongoing intergroup competition, people’s strength of social identification will have a positive impact on their behavioral efforts on behalf of an ingroup when its current status is low, whereas this will not be the case when its current

  7. Instrumented Impact Testing: Influence of Machine Variables and Specimen Position

    Energy Technology Data Exchange (ETDEWEB)

    Lucon, E.; McCowan, C. N.; Santoyo, R. A.

    2008-09-15

    An investigation has been conducted on the influence of impact machine variables and specimen positioning on characteristic forces and absorbed energies from instrumented Charpy tests. Brittle and ductile fracture behavior has been investigated by testing NIST reference samples of low, high and super-high energy levels. Test machine variables included tightness of foundation, anvil and striker bolts, and the position of the center of percussion with respect to the center of strike. For specimen positioning, we tested samples which had been moved away or sideways with respect to the anvils. In order to assess the influence of the various factors, we compared mean values in the reference (unaltered) and altered conditions; for machine variables, t-test analyses were also performed in order to evaluate the statistical significance of the observed differences. Our results indicate that the only circumstance which resulted in variations larger than 5 percent for both brittle and ductile specimens is when the sample is not in contact with the anvils. These findings should be taken into account in future revisions of instrumented Charpy test standards.

  8. The radiation swelling effect on fracture properties and fracture mechanisms of irradiated austenitic steels. Part I. Ductility and fracture toughness

    Energy Technology Data Exchange (ETDEWEB)

    Margolin, B., E-mail: mail@crism.ru; Sorokin, A.; Shvetsova, V.; Minkin, A.; Potapova, V.; Smirnov, V.

    2016-11-15

    The radiation swelling effect on the fracture properties of irradiated austenitic steels under static loading has been studied and analyzed from the mechanical and physical viewpoints. Experimental data on the stress-strain curves, fracture strain, fracture toughness and fracture mechanisms have been represented for austenitic steel of 18Cr-10Ni-Ti grade (Russian analog of AISI 321 steel) irradiated up to neutron dose of 150 dpa with various swelling. Some phenomena in mechanical behaviour of irradiated austenitic steels have been revealed and explained as follows: a sharp decrease of fracture toughness with swelling growth; untypical large increase of fracture toughness with decrease of the test temperature; some increase of fracture toughness after preliminary cyclic loading. Role of channel deformation and channel fracture has been clarified in the properties of irradiated austenitic steel and different tendencies to channel deformation have been shown and explained for the same austenitic steel irradiated at different temperatures and neutron doses.

  9. Dual-Physical Cross-Linked Tough and Photoluminescent Hydrogels with Good Biocompatibility and Antibacterial Activity.

    Science.gov (United States)

    Hu, Chen; Wang, Mei Xiang; Sun, Lei; Yang, Jian Hai; Zrínyi, Miklós; Chen, Yong Mei

    2017-05-01

    Development of novel photoluminescent hydrogels with toughness, biocompatibility, and antibiosis is important for the applications in biomedical field. Herein, novel tough photoluminescent lanthanide (Ln)-alginate/poly(vinyl alcohol) (PVA) hydrogels with the properties of biocompatibility and antibiosis have been facilely synthesized by introducing hydrogen bonds and coordination bonds into the interpenetrating networks of Na-alginate and PVA, via approaches of frozen-thawing and ion-exchanging. The resultant hydrogels exhibit high mechanical strength (0.6 MPa tensile strength, 5.0 tensile strain, 6.0 MPa compressive strength, and 900 kJ m-3 energy dissipation under 400% stretch), good photoluminescence as well as biocompatibility and antibacterial activity. The design strategy provides a new avenue for the fabrication of multifunctional photoluminescent hydrogels based on biocompatible polymers. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Improvement of Fracture Toughness in Epoxy Nanocomposites through Chemical Hybridization of Carbon Nanotubes and Alumina

    Science.gov (United States)

    Zakaria, Muhammad Razlan; Abdul Kudus, Muhammad Helmi; Md. Akil, Hazizan; Zamri, Mohd Hafiz

    2017-01-01

    The current study investigated the effect of adding a carbon nanotube–alumina (CNT–Al2O3) hybrid on the fracture toughness of epoxy nanocomposites. The CNT–Al2O3 hybrid was synthesised by growing CNTs on Al2O3 particles via the chemical vapour deposition method. The CNTs were strongly attached onto the Al2O3 particles, which served to transport and disperse the CNTs homogenously, and to prevent agglomeration in the CNTs. The experimental results demonstrated that the CNT–Al2O3 hybrid-filled epoxy nanocomposites showed improvement in terms of the fracture toughness, as indicated by an increase of up to 26% in the critical stress intensity factor, K1C, compared to neat epoxy. PMID:28772663

  11. Effect of particle size on fracture toughness of SiC/Al composite material

    Science.gov (United States)

    Flom, Y.; Arsenault, R. J.

    1989-01-01

    Discontinuous SiC/Al composites with SiC particles of different sizes were fabricated in order to study the role of particle size on the fracture process. The fracture process is confined to a very narrow band and takes place within the matrix in composites containing small SiC particle sizes. In the composite reinforced with SiC particles of 20 microns and above fracture of SiC begins to dominate. The matrix is influenced by the high density of dislocations generated at SiC/Al interfaces due to the difference in coefficient of thermal expansion between SiC and the Al matrix. Crack initiation fracture toughness does not depend on SiC particle size. Crack growth fracture toughness increases as the size of the SiC particle increase.

  12. Translaminar Fracture Toughness of a Composite Wing Skin Made of Stitched Warp-knit Fabric

    Science.gov (United States)

    Masters, John E.

    1997-01-01

    A series of tests were conducted to measure the fracture toughness of carbon/epoxy composites. The composites were made from warp-knit carbon fabric and infiltrated with epoxy using a resin-film-infusion process. The fabric, which was designed by McDonnell Douglas for the skin of an all-composite subsonic transport wing, contained fibers in the 0 deg, +/-45 deg, and 90 deg directions. Layers of fabric were stacked and stitched together with Kevlar yarn to form a 3-dimensional preform. Three types of test specimens were evaluated: compact tension, center notch tension, and edge notch tension. The effects of specimen size and crack length on fracture toughness were measured for each specimen type. These data provide information on the effectiveness of the test methods and on general trends in the material response. The scope of the investigation was limited by the material that was available.

  13. Development of High Toughness Sheet and Extruded Products for Airplane Fuselage Structures

    Science.gov (United States)

    Magnusen, P. E.; Mooy, D. C.; Yocum, L. A.; Rioja, R. J.

    High specific ultimate strength and high plane stress fracture toughness are primary requirements of aircraft fuselage skins. The performance of alloys/products used in high performance fuselage applications is first reviewed. The specific fracture toughness for products such as 2017-T3, 2024-T3, 2524-T3 and 6013-T6, is discussed as a function of their composition and microstructure. Then the performance of modern Al-Li alloys/products such as 2199 and 2060 sheet and 2099 and 2055 extrusions is examined. It is concluded that the performance of Li containing alloys/products offer significant improvements over non-Li containing conventional fuselage products because of the optimization of strengthening precipitates and grain microstructures. The role of chemical composition on resulting microstructures is discussed.

  14. Standard test method for linear-elastic plane-strain fracture toughness KIc of metallic materials

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2013-01-01

    1.1 This test method covers the determination of fracture toughness (KIc) of metallic materials under predominantly linear-elastic, plane-strain conditions using fatigue precracked specimens having a thickness of 1.6 mm (0.063 in.) or greater subjected to slowly, or in special (elective) cases rapidly, increasing crack-displacement force. Details of test apparatus, specimen configuration, and experimental procedure are given in the Annexes. Note 1—Plane-strain fracture toughness tests of thinner materials that are sufficiently brittle (see 7.1) can be made using other types of specimens (1). There is no standard test method for such thin materials. 1.2 This test method is divided into two parts. The first part gives general recommendations and requirements for KIc testing. The second part consists of Annexes that give specific information on displacement gage and loading fixture design, special requirements for individual specimen configurations, and detailed procedures for fatigue precracking. Additional a...

  15. Standard test method for linear-elastic plane-strain fracture toughness KIc of metallic materials

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2009-01-01

    1.1 This test method covers the determination of fracture toughness (KIc) of metallic materials under predominantly linear-elastic, plane-strain conditions using fatigue precracked specimens having a thickness of 1.6 mm (0.063 in.) or greater subjected to slowly, or in special (elective) cases rapidly, increasing crack-displacement force. Details of test apparatus, specimen configuration, and experimental procedure are given in the Annexes. Note 1—Plane-strain fracture toughness tests of thinner materials that are sufficiently brittle (see 7.1) can be made using other types of specimens (1). There is no standard test method for such thin materials. 1.2 This test method is divided into two parts. The first part gives general recommendations and requirements for KIc testing. The second part consists of Annexes that give specific information on displacement gage and loading fixture design, special requirements for individual specimen configurations, and detailed procedures for fatigue precracking. Additional a...

  16. Rock Fracture Toughness Under Mode II Loading: A Theoretical Model Based on Local Strain Energy Density

    Science.gov (United States)

    Rashidi Moghaddam, M.; Ayatollahi, M. R.; Berto, F.

    2018-01-01

    The values of mode II fracture toughness reported in the literature for several rocks are studied theoretically by using a modified criterion based on strain energy density averaged over a control volume around the crack tip. The modified criterion takes into account the effect of T-stress in addition to the singular terms of stresses/strains. The experimental results are related to mode II fracture tests performed on the semicircular bend and Brazilian disk specimens. There are good agreements between theoretical predictions using the generalized averaged strain energy density criterion and the experimental results. The theoretical results reveal that the value of mode II fracture toughness is affected by the size of control volume around the crack tip and also the magnitude and sign of T-stress.

  17. Two-dimensional magnesium oxide nanosheets reinforced epoxy nanocomposites for enhanced fracture toughness

    Science.gov (United States)

    Balguri, Praveen Kumar; Harris Samuel, D. G.; Guruvishnu, T.; Aditya, D. B.; Mahadevan, S. M.; Thumu, Udayabhaskararao

    2018-01-01

    Metal oxide nanoparticles have been used as excellent reinforcements to enhance mechanical properties of polymers, natural composites, and ceramics. To date, a major portion of metal oxides used as nanofillers is three dimensional spherical nanoparticles. In the last decade, two-dimensional (2D) materials such as graphene have been widely investigated to improve the mechanical and electrical properties of polymer materials. In this paper, 2D Magnesium oxide (MgO) nanosheets reinforced epoxy composites (0.1, 0.2 and 0.4 wt%) are fabricated and studied for their ability to resist the propagation of preexisting flaw by conducting fracture toughness test for K IC, critical stress intensity factor. This property is an important mechanical property for designing applications in various engineering technologies. Our results show that the MgO with 0.2 wt% is the optimized level to improve the fracture toughness of the epoxy polymer by 47%.

  18. 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.

  19. Fracture Toughness of Veneering Ceramics for Fused to Metal (PFM) and Zirconia Dental Restorative Materials

    Science.gov (United States)

    Quinn, Janet B.; Quinn, George D.; Sundar, Veeraraghaven

    2010-01-01

    Veneering ceramics designed to be used with modern zirconia framework restorations have been reported to fracture occasionally in vivo. The fracture toughness of such veneering ceramics was measured and compared to that of conventional feldspathic porcelain veneering ceramics for metal framework restorations. The fracture toughness of the leucite free veneer was measured to be 0.73 MPa m ± 0.02 MPa m, which is less than that for the porcelain fused to metal (PFM) veneering ceramic: 1.10 MPa ± 0.2 MPa. (Uncertainties are one standard deviation unless otherwise noted.) The surface crack in flexure (SCF) method was suitable for both materials, but precrack identification was difficult for the leucite containing feldspathic porcelain PFM veneer. PMID:21833158

  20. Fracture toughness and the effects of stress state on fracture of nickel aluminides

    Science.gov (United States)

    Lewandowski, John J.; Michal, Gary M.; Locci, Ivan; Rigney, Joseph D.

    1991-01-01

    The effects of stress state on the fracture behavior of Ni3Al, Ni3Al + B, and NiAl were determined using either notched or fatigue-precracked bend bars tested to failure at room temperature, in addition to testing specimens in tension under superposed hydrostatic pressure. Although Ni3Al is observed to fail in a macroscopically brittle intergranular manner in tension tests conducted at room temperature, the fracture toughnesses presently obtained on Ni3Al exceeded 20 MPam, and R-curve behavior was exhibited. In situ monitoring of the fracture experiments was utilized to aid in interpreting the source(s) of the high toughness in Ni3Al, while SEM fractography was utilized to determine the operative fracture modes. The superposition by hydrostatic pressure during tensile testing of NiAl specimens was observed to produce increased ductility without changing the fracture mode.

  1. Tough Textiles Protect Payloads and Public Safety Officers

    Science.gov (United States)

    2009-01-01

    In order to create the Mars Pathfinder s mission-critical airbags in the 1990s, NASA s Jet Propulsion Laboratory collaborated with New Ipswich, New Hampshire s Warwick Mills Inc. to weave multi-layer textiles for the airbags for both Pathfinder and the Mars Exploration Rovers. Warwick Mills applied techniques from the collaboration to its puncture- and impact-resistant TurtleSkin product line. The company's metal flex armor (MFA) vests offer stab protection comparable with rigid steel plates and over 50,000 of the vests have sold. The SoftPlate body armor offers protection from handgun bullets, and like the MFA, is designed to be more comfortable than rigid vests. International public safety and military customers are now benefiting from the TurtleSkin products.

  2. Static and dynamic crack toughness of brazed joints of Inconel 718 nickel-base alloy

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, B.Z. (Technion-Israel Inst. of Tech., Haifa); Steffens, H.D.; Englehart, A.H.; Wielage, B.

    1979-10-01

    The crack toughness of brazed joints of Inconel 718 nickel-base alloy was investigated at different strain rates. The brazing filler metal used was BNi5. The results were compared with those obtained on specimens made of the base material. The brazed joints were heat-treated after the brazing process in order to achieve a desirable distribution of the brittle phases in the joint.

  3. Fracture Toughness and Strength in a New Class of Bainitic Chromium-Tungsten Steels

    Energy Technology Data Exchange (ETDEWEB)

    Mao, S. X.; Sikka, V. K.

    2006-06-01

    This project dealt with developing an understanding of the toughening and stengthening mechanisms for a new class of Fe-3Cr-W(V) steels developed at Oak Ridge National Laboratory (ORNL) in collaboration with Nooter Corporation and other industrial partners. The new steele had 50% higher tensile strength up to 650 degrees Celsius than currently used steels and the potential for not requiring any postweld heat treatment (PWHT) and for reducing equipment weight by 25%. This project was closely related to the Nooter project described in the report Development of a New Class of Fe-3Cr-W(V) Ferritic steels for Industrial Process Applications (ORNL/TM-2005/82). The project was carried out jointly by the University of Pittsburgh and ORNL. The University of Pittsburgh carried out fracture toughness measurements and microstructural analysis on base metal and welded plates prepared at ORNL. The project focused on three areas. The first dealt with detailed microstructural analysis of base compositions of 3Cr-3WV and 3Cr-3WBV(Ta) in both normalized (N) and normalized and tempered (NT) conditions. The second aspect of the prject dealt with determining tensile properties and fracture toughness values of K{subIC} at room temperature for both 3Cr-3Wv and 3Cr-3WV(Ta) compositions. The third focus of the project was to measure the fracture toughness values of the base metal and the heat-affectged zone (HAZ) of a plate of Fe-3Cr-W(Mo)V steel plate welded by the gas tungsten are (GTA) process. The HAZ toughness was measured in both the as-welded and the PWHT condition.

  4. USE OF ROUND BAR SPECIMEN IN FRACTURE TOUGHNESS TEST OF METALLIC MATERIALS

    OpenAIRE

    NEELAKANTHA V LONDE,; DR. T.JAYARAJU; DR. P.R.SADANANDA RAO

    2010-01-01

    The fracture toughness of high strength metallic materials is determined by standard test methods like ASTM E 399, ASTM E-1820 using standard specimen geometries such as Compact tension (CT) or Single edge notched bend (SENB) specimens. This paper explains a simple test methodology based on fracture mechanics approach usingcircumferentially cracked round bar (CCRB) specimen. Specimen preparation and fatigue precracking is quite simple, consuming less material and machining time. This CCRB, be...

  5. The relationship between mental toughness and psychological wellbeing in undergraduate students

    OpenAIRE

    Stamp, Elizabeth; Crust, Lee; Swann, Christian; Perry, John; Clough, Peter; Marchant, David

    2014-01-01

    Recent research has highlighted concerns over the mental health of university students. All three years of standard undergraduate study has been identified as challenging and accompanied by multiple potential stressors. Nevertheless, individual differences can function as resistance resources and help buffer the potentially harmful effects of stress. One relevant individual difference is mental toughness (MT) which has emerged from sport research, but more recently has been found to be import...

  6. Antifouling properties of tough gels against barnacles in a long-term marine environment experiment

    OpenAIRE

    Murosaki, T.; Noguchi, T.; Hashimoto, K.; Kakugo, A.; Kurokawa, T.; Saito, J.; Chen, Y. M.; Furukawa, H.; Gong, J. P.

    2009-01-01

    In marine environment, the antifouling properties against marine sessile organisms (algae, sea squirts, barnacles, etc.) were tested on various kinds of hydrogels in a long term. The results demonstrate that most hydrogels can ensure at least 2 months in marine environment. In particular, mechanically tough PAMPS/PAAm DN and PVA gels exhibited amazing antifouling activity against marine sessile organisms, especially barnacles as long as 330 days. The antifouling ability of hydrogels to barnac...

  7. Mixed mode fracture toughness characterization of sandwich interfaces using the modified TSD specimen

    DEFF Research Database (Denmark)

    Berggreen, Christian; Andreasen, J.H.; Carlsson, L.A.

    2009-01-01

    An extensive parametric analysis shows that the modified Tilted Sandwich Debond (TSD) specimen provides a methodology for characterization of the face/core fracture resistance over a range of mode-mixities. A pilot experimental mixed mode characterization of the fracture toughness of sandwich spe...... specimens, with composite faces and various PVC foam cores spanning a range of phase angles, has been achieved by specific steel bar reinforcements and testing over a range of tilt angles....

  8. Reference point indentation is not indicative of whole mouse bone measures of stress intensity fracture toughness

    OpenAIRE

    Carriero, Alessandra; Bruse, Jan L.; Oldknow, Karla J.; Millán, José Luis; Farquharson, Colin; Shefelbine, Sandra J.

    2014-01-01

    Bone fragility is a concern for aged and diseased bone. Measuring bone toughness and understanding fracture properties of the bone are critical for predicting fracture risk associated with age and disease and for preclinical testing of therapies. A reference point indentation technique (BioDent) has recently been developed to determine bone's resistance to fracture in a minimally invasive way by measuring the indentation distance increase (IDI) between the first and last indentations over cyc...

  9. Microneedle-based minimally-invasive measurement of puncture resistance and fracture toughness of sclera.

    Science.gov (United States)

    Park, Seung Hyun; Lee, Kang Ju; Lee, JiYong; Yoon, Jae Hyoung; Jo, Dong Hyun; Kim, Jeong Hun; Kang, Keonwook; Ryu, WonHyoung

    2016-10-15

    The sclera provides the structural support of the eye and protects the intraocular contents. Since it covers a large portion of the eye surface and has relatively high permeability for most drugs, the sclera has been used as a major pathway for drug administration. Recently, microneedle (MN) technology has shown the possibility of highly local and minimally-invasive drug delivery to the eye by MN insertion through the sclera or the suprachoroidal space. Although ocular MN needs to be inserted through the sclera, there has been no systematic study to understand the mechanical properties of the sclera, which are important to design ocular MNs. In this study, we investigated a MN-based method to measure the puncture resistance and fracture toughness of the sclera. To reflect the conditions of MN insertion into the sclera, force-displacement curves obtained from MN-insertion tests were used to estimate the puncture resistance and fracture toughness of sclera tissue. To understand the effect of the insertion conditions, dependency of the mechanical properties on insertion speeds, pre-strain of the sclera, and MN sizes were analyzed and discussed. Measurement of mechanical property of soft biological tissue is challenging due to variations between tissue samples or lack of well-defined measurement techniques. Although non-invasive measurement techniques such as nano/micro indentation were employed to locally measure the elastic modulus of soft biological materials, mechanical properties such as puncture resistance or fracture toughness, which requires "invasive" measurement and is important for the application of "microneedles or hypodermic needles", has not been well studied. In this work, we report minimally-invasive measurement of puncture resistance and fracture toughness of sclera using a double MN insertion method. Parametric studies showed that use of MN proved to be advantageous because of minimally-invasive insertion into tissue as well as higher sensitivity to

  10. Microscale resolution fracture toughness profiling at the zirconia-porcelain interface in dental prostheses

    Science.gov (United States)

    Lunt, Alexander J. G.; Mohanty, Gaurav; Neo, Tee K.; Michler, Johann; Korsunsky, Alexander M.

    2015-12-01

    The high failure rate of the Yttria Partially Stabilized Zirconia (YPSZ)-porcelain interface in dental prostheses is influenced by the micro-scale mechanical property variation in this region. To improve the understanding of this behavior, micro-scale fracture toughness profiling by nanoindentation micropillar splitting is reported for the first time. Sixty 5 μm diameter micropillars were machined within the first 100 μm of the interface. Berkovich nanoindentation provided estimates of the bulk fracture toughness of YPSZ and porcelain that matched the literature values closely. However, the large included tip angle prevented precise alignment of indenter with the pillar center. Cube corner indentation was performed on the remainder of the pillars and calibration between nanoindentation using different tip shapes was used to determine the associated conversion factors. YPSZ micropillars failed by gradual crack propagation and bulk values persisted to within 15 μm from the interface, beyond which scatter increased and a 10% increase in fracture toughness was observed that may be associated with grain size variation at this location. Micropillars straddling the interface displayed preferential fracture within porcelain parallel to the interface at a location where nano-voiding has previously been observed and reported. Pure porcelain micropillars exhibited highly brittle failure and a large reduction of fracture toughness (by up to ~90%) within the first 50 μm of the interface. These new insights constitute a major advance in understanding the structure-property relationship of this important bi-material interface at the micro-scale, and will improve micromechanical modelling needed to optimize current manufacturing routes and reduce failure.

  11. Correlations between leaf toughness and phenolics among species in contrasting environments of Australia and New Caledonia

    Science.gov (United States)

    Read, Jennifer; Sanson, Gordon D.; Caldwell, Elizabeth; Clissold, Fiona J.; Chatain, Alex; Peeters, Paula; Lamont, Byron B.; De Garine-Wichatitsky, Michel; Jaffré, Tanguy; Kerr, Stuart

    2009-01-01

    Background and Aims Plants are likely to invest in multiple defences, given the variety of sources of biotic and abiotic damage to which they are exposed. However, little is known about syndromes of defence across plant species and how these differ in contrasting environments. Here an investigation is made into the association between carbon-based chemical and mechanical defences, predicting that species that invest heavily in mechanical defence of leaves will invest less in chemical defence. Methods A combination of published and unpublished data is used to test whether species with tougher leaves have lower concentrations of phenolics, using 125 species from four regions of Australia and the Pacific island of New Caledonia, in evergreen vegetation ranging from temperate shrubland and woodland to tropical shrubland and rainforest. Foliar toughness was measured as work-to-shear and specific work-to-shear (work-to-shear per unit leaf thickness). Phenolics were measured as ‘total phenolics’ and by protein precipitation (an estimate of tannin activity) per leaf dry mass. Key Results Contrary to prediction, phenolic concentrations were not negatively correlated with either measure of leaf toughness when examined across all species, within regions or within any plant community. Instead, measures of toughness (particularly work-to-shear) and phenolics were often positively correlated in shrubland and rainforest (but not dry forest) in New Caledonia, with a similar trend suggested for shrubland in south-western Australia. The common feature of these sites was low concentrations of soil nutrients, with evidence of P limitation. Conclusions Positive correlations between toughness and phenolics in vegetation on infertile soils suggest that additive investment in carbon-based mechanical and chemical defences is advantageous and cost-effective in these nutrient-deficient environments where carbohydrate may be in surplus. PMID:19098067

  12. 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

  13. Mental Toughness in Talented Youth Tennis Players: A Comparison Between on-Court Observations and a Self-Reported Measure

    Directory of Open Access Journals (Sweden)

    Houwer Ruben

    2017-01-01

    Full Text Available In tennis, mental toughness is often considered highly important in achieving the elite level. The current study is the first to examine behavioural expressions of mental toughness on the court and their relationships with self-reported measures. Based on the input of five experienced tennis coaches of junior tennis players and behaviours used in previous studies, we developed a taxonomy consisting of six positive behaviours and ten negative ones. To investigate the relationship between these on-court behaviours of mental toughness and how the players rated their own mental toughness, emotional control in particular, six talented tennis players (aged 10-13 were recorded during tennis matches and filled out the self-reported measure of mental toughness (MTQ48. The intra- and inter-rater reliability of the taxonomy was high. With regard to the relationships between on-court behaviours and self-reported mental toughness (total score and subscale emotional control, results revealed no significant correlations between the ratios of positive and negative behaviours (range r = -0.49 - 0.11, p > 0.05 or between the variability of negative behaviours (r = 0.54 & r = 0.10, p > 0.05 and the self-reported measure. However, interestingly, we found negative correlations between the variability of positive behaviours and self-reported mental toughness (r = -0.93 & r = -0.84, ρ < 0.05. These results indicate that variability in on-court behaviours provides interesting information about tennis players’ mental toughness, more specifically on the (instability of their psychological state during a match.

  14. Mental Toughness in Talented Youth Tennis Players: A Comparison Between on-Court Observations and a Self-Reported Measure

    Science.gov (United States)

    Houwer, Ruben; Kramer, Tamara; den Hartigh, Ruud; Kolman, Nikki; Elferink-Gemser, Marije

    2017-01-01

    Abstract In tennis, mental toughness is often considered highly important in achieving the elite level. The current study is the first to examine behavioural expressions of mental toughness on the court and their relationships with self-reported measures. Based on the input of five experienced tennis coaches of junior tennis players and behaviours used in previous studies, we developed a taxonomy consisting of six positive behaviours and ten negative ones. To investigate the relationship between these on-court behaviours of mental toughness and how the players rated their own mental toughness, emotional control in particular, six talented tennis players (aged 10-13) were recorded during tennis matches and filled out the self-reported measure of mental toughness (MTQ48). The intra- and inter-rater reliability of the taxonomy was high. With regard to the relationships between on-court behaviours and self-reported mental toughness (total score and subscale emotional control), results revealed no significant correlations between the ratios of positive and negative behaviours (range r = -0.49 - 0.11, p > 0.05) or between the variability of negative behaviours (r = 0.54 & r = 0.10, p > 0.05) and the self-reported measure. However, interestingly, we found negative correlations between the variability of positive behaviours and self-reported mental toughness (r = -0.93 & r = -0.84, ρ < 0.05). These results indicate that variability in on-court behaviours provides interesting information about tennis players’ mental toughness, more specifically on the (in)stability of their psychological state during a match. PMID:28210346

  15. Impact toughness of ternary Al–Zn–Mg alloys in as cast and ...

    Indian Academy of Sciences (India)

    Unknown

    present work. The alloys were used in as cast and homogenized condition purely on the basis of theoretical and academic interest. 2. Experimental. Al–Zn–Mg alloys were obtained by melt casting and air ... six ternary alloys of different compositions were obtained. ... the ratio of shear stress to normal stress (it is equal to 1.

  16. Static and dynamic fracture toughness of 25mm thick single edge notch bend (SENB) specimen of C-Mn pressure vessel submerged arc weld metal and flaw assessment under dynamic loading

    Science.gov (United States)

    Xu, W.; Wiesner, C. S.

    2003-09-01

    Although there are well established procedures for assessing the significance of defects in welded structures in a number of countries, such as BS7910 and R6 procedures in the UK, the Japanese WES 2807 procedure, the API and MPC procedures in the USA and the recently completed SINT AP procedure resulting from European collaboration, there are no clear guidelines for assessment of the effects of dynamic loading. In principle, the standard procedure can be applied for any rate of loading but there is little or no experience of how to allow for the effects of dynamic loading on load magnitude and material properties. Submerge arc weldments of 100mm thick have been manufactured. The effect of loading rate was investigated by testing 25mm thick SENB specimens. The fracture toughness of the weld metal exhibited marked loading rate sensitivity; shift in fracture toughness transition temperature for high loading rate tests of up to 115^{circ}C for 25mm specimens. Finite element (FE) analyses have been carried out to obtain plastic collapse load solutions for SENB fracture mechanics test piece. A simple equation for estimate of dynamic plastic yielding load has been suggested. Flaw assessment under dynamic loading has been demonstrated using the results of dynamic fracture toughness and plastic yiending load. The general methods of assessment of the significance of defects in BS7910 is shown to be applicable to assessments under dynamic loading up to impact.

  17. Fracture Toughness of Carbon Fiber Composites Containing Various Fiber Sizings and a Puncture Self-Healing Thermoplastic Matrix

    Science.gov (United States)

    Cano, Roberto J.; Grimsley, Brian W.; Ratcliffe, James G.; Gordon, Keith L.; Smith, Joseph G.; Siochi, Emilie J.

    2015-01-01

    Ongoing efforts at NASA Langley Research Center (LaRC) have resulted in the identification of several commercially available thermoplastic resin systems which self-heal after ballistic impact and through penetration. One of these resins, polybutylene graft copolymer (PBg), was selected as a matrix for processing with unsized carbon fibers to fabricate reinforced composites for further evaluation. During process development, data from thermo-physical analyses was utilized to determine a processing cycle to fabricate laminate panels, which were analyzed by photo microscopy and acid digestion. The process cycle was further optimized based on these results to fabricate panels for mechanical property characterization. The results of the processing development effort of this composite material, as well as the results of the mechanical property characterization, indicated that bonding between the fiber and PBg was not adequate. Therefore, three sizings were investigated in this work to assess their potential to improve fiber/matrix bonding compared to previously tested unsized IM7 fiber. Unidirectional prepreg was made at NASA LaRC from three sized carbon fibers and utilized to fabricate test coupons that were tested in double cantilever beam configurations to determine GIc fracture toughness.

  18. 'Tough love': The experiences of midwives giving women sterile water injections for the relief of back pain in labour.

    Science.gov (United States)

    Lee, Nigel; Kildea, Sue; Stapleton, Helen

    2017-10-01

    To explore midwives' experiences of administering sterile water injections (SWI) to labouring women as analgesia for back pain in labour. A qualitative study, which generated data through semi-structured focus group interviews with midwives. Data were analysed thematically. Two metropolitan maternity units in Queensland, Australia. Eleven midwives who had administered SWI for back pain in labour in a randomised controlled trial. Three major themes were identified including: i. SWI, is it an intervention?; ii. Tough love, causing pain to relieve pain; iii. The analgesic effect of SWI and impact on midwifery practice. Whilst acknowledging the potential benefits of SWI as an analgesic the midwives in this study described a dilemma between inflicting pain to relieve pain and the challenges encountered in their discussions with women when offering SWI. Midwives also faced conflict when women requested SWI in the face of institutional resistance to its use. The procedural pain associated with SWI may discourage some midwives from offering women the procedure, providing women with accurate information regarding the intensity and the brevity of the injection pain and the expected degree of analgesic would assist in discussion about SWI with women. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. A new integration of hot pressing and carbon partition process to produce high strength steel components with better toughness

    Directory of Open Access Journals (Sweden)

    Zhang Shi-hong

    2015-01-01

    Full Text Available A novel one step method for hot pressing and quench & partition (Q&P integration – hot Pressing-dynamic partitioning (HP-DP process is presented, which can be processed by regular hot pressing equipment and process. The HP-DP formed steel is an upgrade of the existing hot pressed steel especially suitable for making high strength components with superior crashworthiness due to better toughness. Corresponding steel sheet based on conventional 22MnB5 is designed and prepared. After that, the physical simulation experiments for HP-DP are carried out on thermal-mechanical simulator. Microstructure of the steel subjected to HP-DP treatment, with a typical Q&P treated feature, is mainly composed of initial quenched martensite phase, final quenched martensite phase and retained austenite phase, which indicate the occurrence of carbon diffusion concomitantly with martensite transformation. Compared with conventional hot pressed samples, the HP-DP samples show both better tensile property especially elongation and impact energy absorption ability. The effect of HP-DP parameters on the stability of retained austenite and mechanical property is also discussed. The paper illustrates the promising application potential of the HP-DP process.

  20. Forced Protein Unfolding Leads to Highly Elastic and Tough Protein Hydrogels

    Science.gov (United States)

    Fang, Jie; Mehlich, Alexander; Koga, Nobuyasu; Huang, Jiqing; Koga, Rie; Gao, Xiaoye; Hu, Chunguang; Jin, Chi; Rief, Matthias; Kast, Juergen; Baker, David; Li, Hongbin

    2014-01-01

    Protein-based hydrogels usually do not exhibit high stretchability or toughness, significantly limiting the scope of their potential biomedical applications. Here we report the engineering of a chemically crosslinked, highly elastic and tough protein hydrogel using a mechanically extremely labile, de novo designed protein that assumes the classical ferredoxin-like fold structure. Due to the low mechanical stability of the ferredoxin-like fold structure, swelling of hydrogels causes a significant fraction of the fold structure domains to unfold. Subsequent collapse and aggregation of unfolded ferredoxin-like fold structure domains leads to intertwining of physically and chemically crosslinked networks, entailing hydrogels with unusual physical and mechanical properties: a negative swelling ratio, high stretchability and toughness. These hydrogels can withstand an average strain of 450% before breaking and show massive energy dissipation. Upon relaxation, refolding of the ferredoxin-like fold structure domains enables the hydrogel to recover its massive hysteresis. This novel biomaterial may expand the scope of hydrogel applications in tissue engineering. PMID:24352111

  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. Comparisons of various configurations of the edge delamination test for interlaminar fracture toughness

    Science.gov (United States)

    Obrien, T. K.; Johnston, N. J.; Raju, I. S.; Morris, D. H.; Simonds, R. A.

    1985-01-01

    Various configurations of Edge Delamination Tension (EDT) test specimens, of both brittle (T300/5208) and toughened-matrix (T300/BP907) graphite reinforced composite laminates, were manufactured and tested. The mixed-mode interlaminar fracture toughness, G sub C, was measured using (30/30 sub 2/30/90 sub N)sub s, n=1 or 2, (35/-35/0/90) sub s and (35/0/-35/90) sub s layups designed to delaminate at low tensile strains. Laminates were made without inserts so that delaminations would form naturally between the central 90 deg plies and the adjacent angle plies. Laminates were also made with Teflon inserts implanted between the 90 deg plies and the adjacent angle (theta) plies at the straight edge to obtain a planar fracture surface. In addition, interlaminar tension fracture toughness, GIc, was measured from laminates with the same layup but with inserts in the midplane, between the central 90 deg plies, at the straight edge. All of the EDT configurations were useful for ranking the delamination resistance of composites with different matrix resins. Furthermore, the variety of layups and configurations available yield interlaminar fracture toughness measurements needed to generate delamination failure criteria. The influence of insert thickness and location, and coupon size on G sub c values were evaluated.

  3. The Effect of Curing Temperature on the Fracture Toughness of Fiberglass Epoxy Composites

    Science.gov (United States)

    Ryan, Thomas J.

    The curing reaction in a thermoset polymer matrix composite is often accelerated by the addition of heat in an oven or autoclave. The heat added increases the rate of the polymerization reaction and cross-linking in the material. The cure cycle used (temperature, pressure and time) can therefore alter the final material properties. This research focuses on how the curing temperature (250, 275, 300 °F) affects the yield strength and the mode I interlaminar fracture toughness, GI, of a unidirectional S-2 glass epoxy composite. The test method that was used for the tension test was ASTM D3039 and the test method for the mode I interlaminar fracture toughness, the double cantilever beam (DCB) test, was ASTM D5528. The DCB specimens were fabricated with a non-adhesive insert at the midplane of the composite that serves as the initiatior of the delamination. Opening forces were then applied to the specimen, causing the crack propagation. The results show that increasing the cure temperature by 50 °F increased the tensile strength by 10% (86.54 - 94.73 ksi) and decreased the fracture toughness 20% (506.23 - 381.31 J/m 2). Thus, the curing temperature can cause a trade-off between these two properties, which means that the curing cycle will need to be altered based on the intended use and the required material properties.

  4. 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...

  5. Initiation fracture toughness of HSLA steel through automatic measurement of stretch zone

    Energy Technology Data Exchange (ETDEWEB)

    Tarafder, M.; Swati Dey; Dash, B.; Sivaprasad, S.; Tarafder, S. [National Metallurgical Laboratory, Jamshedpur (India)

    2004-12-15

    Stretch zones are formed due to crack tip blunting in ductile materials before the initiation of a crack. Using special edge detection filters, an automatic measurement procedure based on image analysis (IA) for estimating stretch zone dimensions has been proposed. The in house developed software based on the proposed technique requires only fractographic images to automatically define stretch zone boundaries. Employing the proposed technique, stretch zone measurements were carried out on a high strength low alloy (HSLA) steel. The initiation fracture toughness of this HSLA steel has been estimated using these stretch zone dimensions. A comparison of measured stretch zone dimensions with the crack tip blunting region of the fracture resistance curve revealed that the blunting behaviour is non-linear and the data range normally considered for constructing the blunting line is inadequate to represent this non-linearity for these steels. Prediction of initiation fracture toughness (J{sub i}) in high strength, high toughness materials therefore requires blunting line estimation from a modified data range. An upper bound blunting line data range is proposed for accurate prediction of {delta}a{sub cr} (SZW) and J{sub i}. The results of this study indicate that the IA technique can be used effectively for accurate determination of SZW, SZD, J{sub i}, and J{sub Q}. It is also noted that for materials with non-linear blunting behaviour, SZW is a better parameter than SZD for predicting J{sub i} and J{sub Q}. (author)

  6. Enhancement of Fracture Toughness of Epoxy Nanocomposites by Combining Nanotubes and Nanosheets as Fillers

    Directory of Open Access Journals (Sweden)

    Nadiim Domun

    2017-10-01

    Full Text Available In this work the fracture toughness of epoxy resin has been improved through the addition of low loading of single part and hybrid nanofiller materials. Functionalised multi-walled carbon nanotubes (f-MWCNTs was used as single filler, increased the critical strain energy release rate, GIC, by 57% compared to the neat epoxy, at only 0.1 wt% filler content. Importantly, no degradation in the tensile or thermal properties of the nanocomposite was observed compared to the neat epoxy. When two-dimensional boron nitride nanosheets (BNNS were added along with the one-dimensional f-MWCNTs, the fracture toughness increased further to 71.6% higher than that of the neat epoxy. Interestingly, when functionalised graphene nanoplatelets (f-GNPs and boron nitride nanotubes (BNNTs were used as hybrid filler, the fracture toughness of neat epoxy is improved by 91.9%. In neither of these hybrid filler systems the tensile properties were degraded, but the thermal properties of the nanocomposites containing boron nitride materials deteriorated slightly.

  7. Evaluation by Vickers indentation of fracture toughness of a phosphate biodegradable glass.

    Science.gov (United States)

    Clément, J; Torres, P; Gil, F J; Planell, J A; Terradas, R; Martinez, S

    1999-07-01

    Indentation tests are commonly used for the evaluation of fracture toughness of brittle materials, particularly glasses and ceramics, because this technique requires only a small polished area on the specimen surface from which a large number of data points can be generated rapidly. However, a wide variety of equations for the calculation of fracture toughness of ceramic materials by means of Vickers indentation are available. Such equations are obtained phenomenologically and their parameters adjusted in such a way that the KIC values obtained are in good agreement with those obtained by conventional methods. This is the reason why it is necessary to check which type of equation reproduces more accurately the results obtained by means of conventional methods for the material which is going to be investigated. In the present work seven different fracture toughness equations widely used in glass and ceramic studies are considered and the results are compared with those obtained by conventional methods, such as single-edge notch beam (SENB) specimens tested in three-point bending. The role played by the applied indentation load is considered. Copyright 1999 Kluwer Academic Publishers

  8. Use of a compact sandwich specimen to evaluate fracture toughness and interfacial bonding of bone.

    Science.gov (United States)

    Wang, X; Lankford, J; Agrawal, C M

    1994-01-01

    The objective of the present study was to develop a reliable and statistically valid test to measure the fracture toughness of small specimens of bone, and by extension, prosthetic materials, using a compact sandwich specimen. Samples of bone were sandwiched between holders of a different material and using this specimen configuration a new technique was developed to test the fracture toughness of the bone interlayer. The effects of different specimens sizes and holder materials were investigated empirically. Using finite element analysis a correction factor was determined to account for the finite thickness of the interlayer and the analytical solutions governing the test specimen were accordingly modified. Bulk compact tension specimens of bone were tested for comparison. Both wet and dry bone were evaluated and the fracture surface morphology characterized using scanning electron microscopy. The results indicate no statistically significant differences between the fracture toughness values obtained from the compact tension and sandwich specimens. The application of this technique to the testing of interfacial bonding between bone and biomaterials is discussed.

  9. Toughness of 2,25Cr-1Mo steel and weld metal

    Science.gov (United States)

    Acarer, Mustafa; Arici, Gökhan; Acar, Filiz Kumdali; Keskinkilic, Selcuk; Kabakci, Fikret

    2017-09-01

    2,25Cr-1Mo steel is extensively used at elevated temperature structural applications in fossil fire power plants for steam pipes, nozzle chambers and petrochemical industry for hydrocracking unit due to its excellent creep resistance and good redundant to oxidation. Also they should have acceptable weldability and toughness. The steels are supplied in quenched and tempered condition and their welded components are subjected to post-weld heat treatment (PWHT). Tempering process is carried out at 690-710°C to improve toughness properties. However they are sensitive to reheat cracking and temper embrittlement. To measure temper embrittlement of the steels and their weld metal, temper embrittlement factor and formula (J factor - Watanabe and X formula- Bruscato) are used. Step cooling heat treatment is also applied to determine temper embrittlement. In this study, toughness properties of Cr Mo (W) steels were reviewed. Also transition temperature curves of 2,25Cr-1Mo steel and its weld metal were constructed before and after step cool heat treatment as experimental study. While 2,25Cr-1Mo steel as base metal was supplied, all weld metal samples were produced in Gedik Welding Company. Hardness measurements and microstructure evaluation were also carried out.

  10. Influence of second phase particles on fracture toughness in AZ31 magnesium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, T.; Somekawa, H. [Dept. of Metallurgy and Materials Science, Osaka Prefecture Univ., Sakai (Japan); Takara, A.; Nishikawa, Y. [Matsushita Electric Industrial Co., Ltd., Osaka (Japan); Higashi, K. [Dept. of Metallurgy and Materials Science, Osaka Prefecture Univ., Sakai (Japan)

    2004-07-01

    Three kinds of thin AZ31 wrought magnesium alloys sheets were used in order to investigate the influence of the second phase particles on fracture toughness. From the theoretical model, the ratio of {lambda}{sub p}/d{sub p} would be estimated 5 {proportional_to} 6. On the other hand, from the microstructural observation, average particle spacing on each material was sample A: 13.1 {mu}m, sample B: 14.1, and sample C: 12 {mu}. In addition, average particle size on each sample was sample A: 2.1, sample B: 1.9, and sample C: 2.3 {mu}m. Therefore, the ratio of {lambda}{sub p}/d{sub p} calculated from fracture surface observation would be predicted 6 {proportional_to} 7. In comparison with the result of the prediction by theoretical analysis was in good agreement with the result of fracture toughness observation. It was found that the variation in plane-strain fracture toughness on AZ31 were affected by both of particle spacing and particle size. (orig.)

  11. "Reasonable suspicion" about tough immigration legislation: enforcing laws or ethnocentric exclusion?

    Science.gov (United States)

    Mukherjee, Sahana; Molina, Ludwin E; Adams, Glenn

    2013-07-01

    We examined whether support for tough immigration legislation reflects identity-neutral enforcement of law or identity-relevant defense of privilege. Participants read a fabricated news story in which law-enforcement personnel detained a person due to "reasonable suspicion" that he was an undocumented immigrant. We manipulated descriptions of the detainee so that he was either (a) an undocumented immigrant (both studies), (b) a documented immigrant (Study 1), or (c) a U.S. citizen (Study 2) of either Mexican or Canadian origin. Participants in both studies endorsed tougher punishment of an undocumented detainee and rated tough treatment as more fair when the detainee was of Mexican than Canadian origin (regardless of documentation status). Across both studies, the patterns of ethnocentric exclusion-harsher treatment toward Mexican immigrants than Canadian immigrants-were particularly pronounced among participants who defined American identity in terms of assimilation to Anglocentric cultural values (e.g., being able to speak English). Overall, results suggest that people may support tough measures to restrict immigration to defend against symbolic threats-especially threats that cultural "others" pose to Anglocentric understandings of American identity. PsycINFO Database Record (c) 2013 APA, all rights reserved.

  12. Structure-Property Relationships in Tough, Superabsorbent Thermoplastic Elastomers for Hemorrhage Control

    Science.gov (United States)

    Beyer, Frederick; Bain, Erich; Long, Tyler; Mrozek, Randy; Savage, Alice; Martin, Halie; Dadmun, Mark; Lenhart, Joseph

    Between 2001 and 2009, uncontrolled hemorrhaging from major trauma accounted for the deaths of roughly 80% of wounded soldiers with potentially survivable injuries. Modern hemostatic materials are limited in their ability to deliver therapeutic agents, causing tissue damage themselves, or being difficult to remove intact. The goal of this study is to create a mechanically robust polymer that takes up as much as 1000 wt% water in seconds while maintaining sufficient toughness to be removed intact from the wound intact. A thermoplastic elastomer scaffold in which physical crosslinks provide mechanical toughness might provide an appropriate combination of fast swelling and excellent toughness if the matrix material can be engineered to be strongly hydrophilic and swell rapidly. In this work, a commercial SBS triblock copolymer has been modified with poly(acrylic acid) side chains, resulting in materials that are superabsorbent but retain good mechanical properties when saturated. Although SAXS experiments failed to show any significant changes in morphology, even with 800 wt% water uptake, preliminary SANS experiments using selectively deuterated materials and swelling with D2O show significant changes in morphology. Our most recent findings will be presented.

  13. Fracture toughness of Alloy 690 and EN52 weld in air and water

    Energy Technology Data Exchange (ETDEWEB)

    Brown, C.M.; Mills, W.J.

    1999-06-01

    The effect of low and high temperature water with high hydrogen on the fracture toughness of Alloy 690 and its weld, EN52, was characterized using elastic-plastic J{sub IC} methodology. While both materials display excellent fracture resistance in air and elevated temperature (>93 C) water, a dramatic degradation in toughness is observed in 54 C water. The loss of toughness is associated with a hydrogen-induced intergranular cracking mechanism where hydrogen is picked up from the water. Comparison of the cracking behavior in low temperature water with that for hydrogen-precharged specimens tested in air indicates that the critical local hydrogen content required to cause low temperature embrittlement is on the order of 120 to 160 ppm. Loading rate studies show that the cracking resistance is significantly improved at rates above ca. 1000 MPa{radical}m/h because there is insufficient time to produce grain boundary embrittlement. Electron fractographic examinations were performed to correlate cracking behavior with microstructural features and operative fracture mechanics.

  14. A two-dimensional dispersion module for the TOUGH2 simulator

    Energy Technology Data Exchange (ETDEWEB)

    Oldenburg, C.M.; Pruess, K.

    1993-09-01

    A standard model for hydrodynamic dispersion has been added to TOUGH2- The dispersion model, intended for use with the EOS7 fluid properties module, accounts for the effects of hydrodynamic dispersion and molecular diffusion in two-dimensional rectangular domains. Because the model.requires Darcy velocity and species concentration gradient vectors at all connections, known vector components (perpendicular to the grid block interfaces) from neighboring connections are interpolated to form the unknown components (parallel to the grid block interfaces) at each connection. Thus the dispersive fluxes depend not only on the primary variables of the two connected grid blocks but on all p variables of the six neighbor grid blocks of each interface. This gives rise to added terms in the Jacobian matrix relative to standard TOUGH2 where fluxes depend only on primary variables in the two connected grid blocks. For flexibility in implementing boundary conditions, the model allows the user to define a flow domain that is a subset of the calculation domain. The PARAM and SELEC blocks of the TOUGH2 input file are used to specify parameters and boundary condition options for the dispersion module. The dispersion module has been verified by comparing computed results to analytical solutions. As an introduction to applications, we demonstrate the solution of a difficult twodimensional flow problem with variable salinity and strong coupling between dispersive and advective flow.

  15. Measurement of the fracture toughness of polycrystalline bubbly ice from an Antarctic ice core

    Directory of Open Access Journals (Sweden)

    J. Christmann

    2015-05-01

    Full Text Available The critical fracture toughness is a material parameter describing the resistance of a cracked body to further crack extension. It is an important parameter for simulating and predicting the breakup behavior of ice shelves from the calving of single icebergs to the disintegration of entire ice shelves over a wide range of length scales. The fracture toughness values are calculated with equations that are derived from an elastic stress analysis. Additionally, an X-ray computer tomography (CT scanner was used to identify the density as a function of depth. The critical fracture toughness of 91 Antarctic bubbly ice samples with densities between 840 and 870 kg m−3 has been determined by applying a four-point bending technique on single-edge v-notched beam samples. The examined ice core was drilled 70 m north of Kohnen Station, Dronnning Maud Land (75°00' S, 00°04' E; 2882 m. Supplementary data are available at doi:10.1594/PANGAEA.835321.

  16. An investigation on directionally dependent fracture toughness behavior of monolithic nickel gradient material synthesized from electroplating

    Science.gov (United States)

    Farooq, Ahmad; El-Aty, Ali Abd; Ahmed, Tauseef; Tai-Chi, Chang

    2017-07-01

    Bulk sized continuous and monolithic pure Nickel gradient material is successfully developed using electroplating method. Great emphasis is given on controlling the direction of the gradient for the samples. The gradient belt for each Nickel gradient material consisted of grain size from maximum 4 µm to minimum 20nm, with the belt transcending from coarse towards ultrafine to finally nano-grain structure. Crack is propagated from Coarse to Nano-grain gradient Nickel and vice versa in order to procure the J-integral (Jic) for each sample according to ASTM standard E-1820 and deduce the fracture properties under each condition. Under such conditions when crack propagated from coarse to nano direction, Jmax is found to be 215kJ/m2 while crack propagating from Nano to Coarse direction, Jmax is found to be 62kJ/m2. Such dual polarized Jic within a single material is unique, especially for nickel whose Jicin literature for coarse grain (95 µm) was around 225kJ/m2 and ultrafine grain (300nm) was 100 kJ/m2, meaning the nickel gradient material consisting the grain gradient belt between 4 µm-20nm exhibits similar fracture toughness as pure coarse grain almost 20 times larger. Such gradient material exhibiting directionally dependent fracture toughness behavior can most certainly be much stronger under tensile conditions while keeping high fracture toughness.

  17. Characterizing the toughness of an epoxy resin after wet aging using compact tension specimens with non-uniform moisture content

    KAUST Repository

    Quino, Gustavo

    2014-11-01

    Characterizing the change in toughness of polymers subjected to wet aging is challenging because of the heterogeneity of the testing samples. Indeed, as wet aging is guided by a diffusion/reaction process, compact tension samples (defined by the ASTM D5045 standard), which are relevant for toughness characterization but are somewhat thick, display a non-uniform moisture content over the bulk material. We define here a rigorous procedure to extract meaningful data from such tests. Our results showed that the relation between the moisture uptake of the whole sample and the measured toughness was not a meaningful material property. In fact, we found that the measured toughness depended on the locally varying moisture uptake over the cracking path. Here, we propose a post-processing technique that relies on a validated reaction/diffusion model to predict the three-dimensional moisture state of the epoxy. This makes identification of the variation in toughness with respect to the local moisture content possible. In addition, we analyze the fracture surface using micrography and roughness measurements. The observed variations in toughness are correlated with the roughness in the vicinity of the crack tip. © 2014 Elsevier Ltd. All rights rese.

  18. Influence of solution annealing on microstructure and mechanical properties of Maraging 300 steel

    Energy Technology Data Exchange (ETDEWEB)

    Lima Filho, Venceslau Xavier; Barros, Isabel Ferreira; Abreu, Hamilton Ferreira Gomes de, E-mail: venceslau@ifce.edu.br [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil). Departamento de Engenharia Metalurgica e Materiais. Laboratorio de Caracterizacao de Materiais, Metalurgia Fisica e Grupo de Pesquisa de Transformacao de Fase

    2017-01-15

    Maraging 300 belongs to a family of metallic materials with extremely high mechanical strength and good toughness. Some works have been published about aging temperatures that improve ultimate strength resistance with acceptable toughness levels in this steel family, where the prior austenite grain size obtained by different solution annealing temperature influence in the final mechanical properties. Solution annealing temperatures ranging from 860 °C to 1150 deg C and were kept constant until the aging temperature. These treatments were used in order to investigate their influence on the microstructure and mechanical properties of maraging steel 300, especially with regard to toughness. The characterization of the microstructure was performed by optical microscopy, scanning electron microscope (SEM) and X-ray diffraction (XRD). Mechanical properties were evaluated by Rockwell C hardness and Charpy impact tests. The results showed that there is a temperature range where one can get some improvement in toughness without a large loss of mechanical strength. (author)

  19. Unstructured grids for numerical reservoir simulation. Using TOUGH2 for gas storage

    Energy Technology Data Exchange (ETDEWEB)

    Littmann, Wolfgang; Littmann, Kristof [Consulting Reservoir Engineering, Wunstorf (Germany)

    2012-12-15

    For numerical reservoir simulation structured grids are commonly used. These grids are following the geological structure and are bound to the layering of the reservoir. In principal these grids should be regular for the task to solve the differential equations describing the flow of fluids in a reservoir in space and time. For the means of a better adaptation of the grid to the geological structure so called corner point grids have been introduced, which strictly follow the reservoir layering. At faults these corner point grids encounter the problem that grid blocks belonging to different layers should communicate with each other. Formally these non neighbor connections do not comply with the mathematical scheme of the finite difference solution approach. Another approach for the simulation of fluid and heat flow in reservoirs is the unstructured gridding as it is e.g. used in the TOUGH2 simulator. Grid cells of any geometry can be defined. The location in space of a grid cell is not used in the simulation. Only the volume of a grid cell and the relation to its neighboring cells has to be defined. For each cell the net flow of mass and heat is calculated during the simulation. The flow equations are then represented as Taylor series of the primary variables like temperature or pressure. The Taylor series is truncated after the first term and the resulting system of linear equations for the residuals can be solved using standard algorithms. Typically the system is solved implicitly in a few iteration steps. The TOUGH2 simulator has been developed by K. Pruess at the University of California in Berkeley. It is written in Fortran and the source code can be obtained under a license. The way the software is designed makes it very flexible but this concept also makes it difficult to use. The typical reservoir modeling tools applicable in the oil and gas industry cannot be directly used to create a simulation model with TOUGH2. This paper describes how input data from a

  20. Design of 3D scaffolds for tissue engineering testing a tough polylactide-based graft copolymer

    Energy Technology Data Exchange (ETDEWEB)

    Dorati, R., E-mail: rossella.dorati@unipv.it [Department of Drug Sciences, University of Pavia, V.le Taramelli 12, 27100 Pavia (Italy); Center for Tissue Engineering (CIT), University of Pavia, Via Ferrata 1, 27100 Pavia (Italy); Colonna, C. [Department of Drug Sciences, University of Pavia, V.le Taramelli 12, 27100 Pavia (Italy); Center for Tissue Engineering (CIT), University of Pavia, Via Ferrata 1, 27100 Pavia (Italy); Tomasi, C. [C.S.G.I., Department of Chemistry, Division of Physical Chemistry, University of Pavia, V.le Taramelli 16 I, 27100 Pavia (Italy); Genta, I. [Department of Drug Sciences, University of Pavia, V.le Taramelli 12, 27100 Pavia (Italy); Center for Tissue Engineering (CIT), University of Pavia, Via Ferrata 1, 27100 Pavia (Italy); Bruni, G. [C.S.G.I., Department of Chemistry, Division of Physical Chemistry, University of Pavia, V.le Taramelli 16 I, 27100 Pavia (Italy); Conti, B. [Department of Drug Sciences, University of Pavia, V.le Taramelli 12, 27100 Pavia (Italy); Center for Tissue Engineering (CIT), University of Pavia, Via Ferrata 1, 27100 Pavia (Italy)

    2014-01-01

    The aim of this research was to investigate a tough polymer to develop 3D scaffolds and 2D films for tissue engineering applications, in particular to repair urethral strictures or defects. The polymer tested was a graft copolymer of polylactic acid (PLA) synthesized with the rationale to improve the toughness of the related PLA homopolymer. The LMP-3055 graft copolymer (in bulk) demonstrated to have negligible cytotoxicity (bioavailability > 85%, MTT test). Moreover, the LMP-3055 sterilized through gamma rays resulted to be cytocompatible and non-toxic, and it has a positive effect on cell biofunctionality, promoting the cell growth. 3D scaffolds and 2D film were prepared using different LMP-3055 polymer concentrations (7.5, 10, 12.5 and 15%, w/v), and the effect of polymer concentration on pore size, porosity and interconnectivity of the 3D scaffolds and 2D film was investigated. 3D scaffolds got better results for fulfilling structural and biofunctional requirements: porosity, pore size and interconnectivity, cell attachment and proliferation. 3D scaffolds obtained with 10 and 12.5% polymer solutions (3D-2 and 3D-3, respectively) were identified as the most suitable construct for the cell attachment and proliferation presenting pore size ranged between 100 and 400 μm, high porosity (77–78%) and well interconnected pores. In vitro cell studies demonstrated that all the selected scaffolds were able to support the cell proliferation, the cell attachment and growth resulting to their dependency on the polymer concentration and structural features. The degradation test revealed that the degradation of polymer matrix (ΔMw) and water uptake of 3D scaffolds exceed those of 2D film and raw polymer (used as control reference), while the mass loss of samples (3D scaffold and 2D film) resulted to be controlled, they showed good stability and capacity to maintain the physical integrity during the incubation time. - Highlights: • Tough PLA graft copolymer was proposed

  1. 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

  2. Effect of Welding Heat Input on the Microstructure and Toughness in Simulated CGHAZ of 800 MPa-Grade Steel for Hydropower Penstocks

    Directory of Open Access Journals (Sweden)

    Qingfeng Ding

    2017-03-01

    Full Text Available To determine the appropriate welding heat input for simulated coarse grained heat affected zone (CGHAZ of 800 MPa-grade steel used in hydropower penstocks, the microstructural evolution, hardness, and 50% fraction appearance transition temperature (50% FATT were investigated. The results indicated that when the cooling rate (heat input is reduced (increased, the impact toughness at −20 °C and hardness of the simulated CGHAZ decreased. When the heat input increased from 18 to 81 kJ/cm, the 50% FATT increased from −80 °C to −11 °C. At 18 kJ/cm, the microstructures consisted of lath bainite and granular bainite, but lath bainite decreased with increasing heat input. The increase in the 50% FATT was attributed mainly to an increase in the austenite grain size and effective grain size, and a decrease in lath bainite and the fraction of HAGBs (misorientation: ≥15°.

  3. An experimental study on fracture toughness of resistance spot welded galvanized and ungalvanized DP 450 steel sheets used in automotive body

    Energy Technology Data Exchange (ETDEWEB)

    Sevim, I.

    2016-07-01

    The purpose of this study is to determine fracture toughness of Resistance Spot Welded (RSW) Dual Phase (DP) steels. RSW of galvanized and ungalvanized DP 450 steel sheets was carried out on spot welding machine. Fracture toughness of RSW joints of galvanized and ungalvanized DP 450 steel sheets was calculated from tensile-shear tests. New empirical equations were developed using Least Squares Method (LSM) between energy release rate, fracture toughness and critical crack size depending on the relationship between hardness and fracture toughness values. Results indicated that fracture toughness of joints welded by using RSW increased exponentially while the hardness decreased. In addition, fracture toughness and energy release rate of RSW galvanized DP 450 steel sheets were lower compared to RSW ungalvanized DP 450 steel sheets which had approximately the same hardness. (Author)

  4. Impacts

    NARCIS (Netherlands)

    Hellmuth, M.; Kabat, P.

    2003-01-01

    Even without the impacts of climate change, water managers face prodigious challenges in meeting sustainable development goals. Growing populations need affordable food, water and energy. Industrial development demands a growing share of water resources and contaminates those same resources with its

  5. Role of the gender-linked norm of toughness in the decision to engage in treatment for depression.

    Science.gov (United States)

    O'Loughlin, Ryan E; Duberstein, Paul R; Veazie, Peter J; Bell, Robert A; Rochlen, Aaron B; Fernandez y Garcia, Erik; Kravitz, Richard L

    2011-07-01

    Given their prevalence and persuasive power in our culture, gender norms--commonly described as socially reinforced, learned expectations of what it means to be a man or a woman--likely contribute to sex differences in service utilization for depression. This study investigated whether sex differences in toughness, a gender-linked norm characterized by a desire to hide pain and maintain independence, were associated with a preference to wait for depression to resolve on its own without active professional treatment ("wait-and-see" approach). Participants (N=1,051) in the California Behavioral Risk Factor Surveillance System (BRFSS) survey were contacted in a follow-on survey to assess toughness, the kind of treatment they would prefer were they to receive a diagnosis of depression, and current symptoms of depression. Participants who reported ever having been diagnosed as having a depressive disorder on the BRFSS were oversampled threefold. Analyses were conducted using linear and logistic regressions. Men and women who scored higher on toughness had a greater preference for the wait-and-see approach (OR=1.14, p<.01). Women were less likely to prefer the wait-and-see approach (OR=.58, p<.04) and scored lower on toughness (B=-.70, p<.01). Men's greater levels of toughness partially mediated the sex difference in treatment preferences (OR=.91, p<.03). Men's greater adherence to the toughness norm explained part of the sex difference observed in treatment-seeking preferences, but toughness undermined women's treatment seeking as well. Findings could be used to inform novel public health communications intended to attract both men and women to psychiatric services.

  6. IMPACTS !

    CERN Multimedia

    2008-01-01

    (Photo courtesy of Don Davis / NASA)The University of Geneva (UNIGE) and the Ecole Polytechnique Fédérale of Lausanne (EPFL) are organising the 4th series of public lectures on astronomy, on the theme of "Impacts". The schedule is as follows: Il y a 100 ans : une explosion dans la Tunguska – Dr. Frédéric COURBIN, EPFL Les impacts sur Terre – Prof. Didier Queloz, UNIGE La fin des dinosaures – Dr. Stéphane Paltani, UNIGE Wednesday 7 May 2008, from 7.00 p.m. to 9.00 p.m. Auditoire CO1, EPFL, Ecublens Thursday 08 May 2008, from 7.00 p.m. to 9.00 p.m. Auditoire Rouiller, Uni-Dufour, Genève All 3 lectures will be givent each evening! Admission free Information: 022 379 22 00

  7. User's Guide for Hysteretic Capillary Pressure and Relative Permeability Functions in iTOUGH2

    Energy Technology Data Exchange (ETDEWEB)

    Doughty, C.A.

    2009-08-01

    The precursor of TOUGH2, TOUGH, was originally developed with non-hysteretic characteristic curves. Hysteretic capillary pressure functions were implemented in TOUGH in the late 1980s by Niemi and Bodvarsson (1988), and hysteretic capillary pressure and relative permeability functions were added to iTOUGH2 about ten years later by Finsterle et al. (1998). Recently, modifications were made to the iTOUGH2 hysteretic formulation to make it more robust and efficient (Doughty, 2007). Code development is still underway, with the ultimate goal being a hysteretic module that fits into the standard TOUGH2 (Pruess et al., 1991) framework. This document provides a user's guide for the most recent version of the hysteretic code, which runs within iTOUGH2 (Finsterle, 1999a,b,c). The current code differs only slightly from what was presented in Doughty (2007), hence that document provides the basic information on the processes being modeled and how they are conceptualized. This document focuses on a description of the user-specified parameters required to run hysteretic iTOUGH2. In the few instances where the conceptualization differs from that of Doughty (2007), the features described here are the current ones. Sample problems presented in this user's guide use the equation-of-state module ECO2N (Pruess, 2005). The components present in ECO2N are H{sub 2}O, NaCl, and CO{sub 2}. Two fluid phases and one solid phase are considered: an aqueous phase, which primarily consists of liquid H2O and may contain dissolved NaCl and CO{sub 2}; a supercritical phase which primarily consists of CO{sub 2}, but also includes a small amount of gaseous H{sub 2}O; and a solid phase consisting of precipitated NaCl. Details of the ECO2N formulation may be found in Pruess (2005). The aqueous phase is the wetting phase and is denoted ''liquid'', whereas the supercritical phase is the non-wetting phase and is denoted ''gas''. The hysteretic formalism

  8. Controlling toughness and dynamics of polymer networks via mussel-inspired dynamical bonds

    Science.gov (United States)

    Filippidi, Emmanouela

    For dry, thermoset, polymer systems increasing the degree of cross-linking increases the elastic modulus. However, it simultaneously compromises the elongation under tension, usually reducing the overall total energy dissipated before fracture (toughness). Dynamic reformable bonds and complex network topologies have been used to circumnavigate this issue with moderate success, mainly in hydrated network systems. Hydration, however, which swells these networks limits how far one could increase the modulus, while their chemistry prevents improvement of the mechanics upon drying. Employing the mussel byssus-inspired strategy of iron-catechol coordination bonds, we have synthesized and studied epoxy networks comprising covalently attached catechol moieties capable of forming additional iron-catechol complex cross-links that still function in dry conditions. In such a fashion, we create a high modulus, high elongation, high toughness material. The iron-catechol coordination bonds play multiple roles that enhance the mechanical performance of the system: at low strain and fast strain rates, they act like permanent cross-links with bonding strength similar to covalent bonds, but start disassociating at high elongation. They are also reformable, enabling material self-healing in a matter of minutes in the absence of load. Finally, the dissociative crosslink cleavage alters the local chain topology, creating length scales that unfold upon elongation. The elegance of this system lies on its general versatility. Both the polymer and metal ion can be used as control parameters to study the interplay of covalent and dynamical bonds as well as explore the limits of the design of elastomers with enhanced toughness. MRSEC of NSF Award No. DMR-1121053.

  9. A turbulent transport network model in MULTIFLUX coupled with TOUGH2

    Energy Technology Data Exchange (ETDEWEB)

    Danko, G.; Bahrami, D.; Birkholzer, J.T.

    2011-02-15

    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.

  10. 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.

  11. Experimental investigation of effect of specimen thickness on fracture toughness of Al-TiC composites

    Directory of Open Access Journals (Sweden)

    M. S. Raviraj

    2016-07-01

    Full Text Available In this paper, the macro and micro-mechanical fracture behavior was studied for aluminum (Al6061 alloy matrix, reinforced with various proportions of TiC particles such as 3wt%, 5wt% and 7wt%. The Al6061-TiC metal matrix composites were produced by stir casting method to ensure uniform distribution of the TiC particulates in the Al matrix. The compact tension (CT specimens were machined according to ASTM E399 specifications to evaluate the fracture toughness for Al6061-TiC metal matrix composites. The CT specimens were machined for crack to width (a/W ratio of 0.5 and thickness to width (B/W ratios of 0.2 to 0.7 with an increment of 0.1. Load versus crack mouth opening displacement (CMOD data was plotted to estimate stress intensity factor KQ for various thicknesses of the specimen. The fracture toughness KIC was obtained by plotting stress intensity factor versus thickness to width ratios of specimen data. The fracture toughness of these composites varied between 16.4-19.2 MPa√m. Scanning Electron Microscope (SEM studies was made on the fractured surface of the specimens to understand the micro-mechanisms of failure involved in these composites. Void initiation is more significant in the matrix near the interface. The micro-cracks grow from these micro-voids and crack propagates by linking these micro cracks locating the crack path preferentially in the matrix adjacent to the interface indicating ductile fracture.

  12. Sub-10-micrometer toughening and crack tip toughness of dental enamel.

    Science.gov (United States)

    Ang, Siang Fung; Schulz, Anja; Pacher Fernandes, Rodrigo; Schneider, Gerold A

    2011-04-01

    In previous studies, enamel showed indications to occlude small cracks in-vivo and exhibited R-curve behaviors for bigger cracks ex-vivo. This study quantifies the crack tip's toughness (K(I0),K(III0)), the crack's closure stress and the cohesive zone size at the crack tip of enamel and investigates the toughening mechanisms near the crack tip down to the length scale of a single enamel crystallite. The crack-opening-displacement (COD) profile of cracks induced by Vickers indents on mature bovine enamel was studied using atomic force microscopy (AFM). The mode I crack tip toughness K(I0) of cracks along enamel rod boundaries and across enamel rods exhibit a similar range of values: K(I0,Ir)=0.5-1.6MPa m(0.5) (based on Irwin's 'near-field' solution) and K(I0,cz)=0.8-1.5MPa m(0.5) (based on the cohesive zone solution of the Dugdale-Muskhelishvili (DM) crack model). The mode III crack tip toughness K(III0,Ir) was computed as 0.02-0.15MPa m(0.5). The crack-closure stress at the crack tip was computed as 163-770 MPa with a cohesive zone length and width 1.6-10.1μm and 24-44 nm utilizing the cohesive zone solution. Toughening elements were observed under AFM and SEM: crack bridging due to protein ligament and hydroxyapatite fibres (micro- and nanometer scale) as well as microcracks were identified. Crown Copyright © 2010. Published by Elsevier Ltd. All rights reserved.

  13. Tough Supramolecular Polymer Networks with Extreme Stretchability and Fast Room-Temperature Self-Healing.

    Science.gov (United States)

    Liu, Ji; Tan, Cindy Soo Yun; Yu, Ziyi; Li, Nan; Abell, Chris; Scherman, Oren A

    2017-06-01

    Recent progress on highly tough and stretchable polymer networks has highlighted the potential of wearable electronic devices and structural biomaterials such as cartilage. For some given applications, a combination of desirable mechanical properties including stiffness, strength, toughness, damping, fatigue resistance, and self-healing ability is required. However, integrating such a rigorous set of requirements imposes substantial complexity and difficulty in the design and fabrication of these polymer networks, and has rarely been realized. Here, we describe the construction of supramolecular polymer networks through an in situ copolymerization of acrylamide and functional monomers, which are dynamically complexed with the host molecule cucurbit[8]uril (CB[8]). High molecular weight, thus sufficient chain entanglement, combined with a small-amount dynamic CB[8]-mediated non-covalent crosslinking (2.5 mol%), yields extremely stretchable and tough supramolecular polymer networks, exhibiting remarkable self-healing capability at room temperature. These supramolecular polymer networks can be stretched more than 100× their original length and are able to lift objects 2000× their weight. The reversible association/dissociation of the host-guest complexes bestows the networks with remarkable energy dissipation capability, but also facile complete self-healing at room temperature. In addition to their outstanding mechanical properties, the networks are ionically conductive and transparent. The CB[8]-based supramolecular networks are synthetically accessible in large scale and exhibit outstanding mechanical properties. They could readily lead to the promising use as wearable and self-healable electronic devices, sensors and structural biomaterials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Mussel-Inspired Adhesive and Tough Hydrogel Based on Nanoclay Confined Dopamine Polymerization.

    Science.gov (United States)

    Han, Lu; Lu, Xiong; Liu, Kezhi; Wang, Kefeng; Fang, Liming; Weng, Lu-Tao; Zhang, Hongping; Tang, Youhong; Ren, Fuzeng; Zhao, Cancan; Sun, Guoxing; Liang, Rui; Li, Zongjin

    2017-03-28

    Adhesive hydrogels are attractive biomaterials for various applications, such as electronic skin, wound dressing, and wearable devices. However, fabricating a hydrogel with both adequate adhesiveness and excellent mechanical properties remains a challenge. Inspired by the adhesion mechanism of mussels, we used a two-step process to develop an adhesive and tough polydopamine-clay-polyacrylamide (PDA-clay-PAM) hydrogel. Dopamine was intercalated into clay nanosheets and limitedly oxidized between the layers, resulting in PDA-intercalated clay nanosheets containing free catechol groups. Acrylamide monomers were then added and in situ polymerized to form the hydrogel. Unlike previous single-use adhesive hydrogels, our hydrogel showed repeatable and durable adhesiveness. It adhered directly on human skin without causing an inflammatory response and was easily removed without causing damage. The adhesiveness of this hydrogel was attributed to the presence of enough free catechol groups in the hydrogel, which were created by controlling the oxidation process of the PDA in the confined nanolayers of clay. This mimicked the adhesion mechanism of the mussels, which maintain a high concentration of catechol groups in the confined nanospace of their byssal plaque. The hydrogel also displayed superior toughness, which resulted from nanoreinforcement by clay and PDA-induced cooperative interactions with the hydrogel networks. Moreover, the hydrogel favored cell attachment and proliferation, owning to the high cell affinity of PDA. Rat full-thickness skin defect experiments demonstrated that the hydrogel was an excellent dressing. This free-standing, adhesive, tough, and biocompatible hydrogel may be more convenient for surgical applications than adhesives that involve in situ gelation and extra agents.

  15. Examining Dark Triad traits in relation to mental toughness and physical activity in young adults

    Directory of Open Access Journals (Sweden)

    Sabouri S

    2016-01-01

    Full Text Available Sarah Sabouri,1 Markus Gerber,2 Dena Sadeghi Bahmani,3 Sakari Lemola,4 Peter J Clough,5 Nadeem Kalak,3 Mahin Shamsi,1 Edith Holsboer-Trachsler,3 Serge Brand2,3 1Faculty of Educational Sciences and Psychology, AllamehTabataba’i University, Tehran, Iran; 2Department of Sport, Exercise and Health, Sport Science Section, University of Basel, 3Center for Affective, Stress and Sleep Disorders, Psychiatric Clinics of the University of Basel, 4Faculty of Psychology, University of Basel, Basel, Switzerland; 5Department of Psychology, Manchester Metropolitan University, Manchester, UK Objective: The Dark Triad (DT describes a set of three closely related personality traits: Machiavellianism, narcissism, and psychopathy. Mental toughness (MT refers to a psychological construct combining confidence, commitment, control, and challenge. High MT is related to greater physical activity (PA and, relative to men, women have lower MT scores. The aims of the present study were 1 to investigate the association between DT, MT, and PA, and 2 to compare the DT, MT, and PA scores of men and women.Methods: A total of 341 adults (M=29 years; 51.6% women; range: 18–37 years took part in the study. Participants completed a series of questionnaires assessing DT, MT, and PA.Results: Machiavellianism, narcissism, and psychopathy were all significantly associated with higher MT scores (rs =0.45, 0.50, and 0.20, respectively. DT traits and MT were associated with more vigorous PA. Compared to men, women participants had lower scores for DT traits (overall score and psychopathy, while no differences were found for MT or PA in both sexes.Conclusion: DT traits, high MT, and vigorous PA are interrelated. This pattern of results might explain why, for instance, successful professional athletes can at the same time be tough and ruthless. Keywords: dark triad, mental toughness, physical activity, young adults, sex

  16. 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.

  17. Microstructure-dependent fracture toughness (JIC) variations in dissimilar pipe welds for pressure vessel system of nuclear plants

    Science.gov (United States)

    Rathod, Dinesh W.; Pandey, Sunil; Singh, P. K.; Kumar, Suranjit

    2017-09-01

    In present study, dissimilar metal weld (DMW) joints between SA508Gr.3cl.1 ferritic steel and SS304LN pipes were prepared using Inconel 82/182, and Inconel 52/152 consumables. Metallurgical properties and their influence on fracture toughness of weldment regions and interfacial regions could play a significant role in integrity assessment of these joints. Ni-based consumables exhibit complex metallurgical properties at interfacial regions. The metallurgical characterization and fracture toughness studies of Inconel 82/182 and Inconel 52/152 joints have been carried out for determining the optimum consumable for DMW joint requirements and the effect of microstructure on fracture toughness in weldment regions. The present codes and procedures for integrity assessment of DMW joints have not given due considerations of metallurgical properties. The requirements for metallurgical properties by considering their effect on fracture toughness properties in integrity assessment have been discussed for reliable analysis. Inconel 82/182 is preferred over Inconel 52/152 joints owing to favorable metallurgical and fracture toughness properties across the interfacial and weldment regions.

  18. Transition Fracture Toughness Characterization of Eurofer 97 Steel using Pre-Cracked Miniature Multi-notch Bend Bar Specimens

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xiang [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Sokolov, Mikhail A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Linton, Kory D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Clowers, Logan N. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Katoh, Yutai [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-11-01

    In this report, we present the feasibility study of using pre-cracked miniature multi-notch bend bar specimens (M4CVN) with a dimension of 45mm (length) x 3.3mm (width) x 1.65mm (thickness) to characterize the transition fracture toughness of Eurofer97 based on the ASTM E1921 Master Curve method. From literature survey results, we did not find any obvious specimen size effects on the measured fracture toughness of unirradiated Eurofer97. Nonetheless, in order to exclude the specimen size effect on the measured fracture toughness of neutron irradiated Eurofer97, comparison of results obtained from larger size specimens with those from smaller size specimens after neutron irradiation is necessary, which is not practical and can be formidably expensive. However, limited literature results indicate that the transition fracture toughness of Eurofer97 obtained from different specimen sizes and geometries followed the similar irradiation embrittlement trend. We then described the newly designed experimental setup to be used for testing neutron irradiated Eurofer97 pre-cracked M4CVN bend bars in the hot cell. We recently used the same setup for testing neutron irradiated F82H pre-cracked miniature multi-notch bend bars with great success. Considering the similarity in materials, specimen types, and the nature of tests between Eurofer97 and F82H, we believe the newly designed experimental setup can be used successfully in fracture toughness testing of Eurofer97 pre-cracked M4CVN specimens.

  19. A study on the fracture behavior in tensile and fracture toughness tests of CFRP by acoustic emission

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang Guk; Oh, Sae Kyoo; Nam, Ki Woo; Kim, Og Gyun [Bukyung National University, Pusan (Korea, Republic of)

    1994-05-15

    This study was carried out to analyze the fracture behavior and the acoustic emission(AE) characteristics, and to find relationship between tensile strength, fracture toughness and cure pressure in cure process of the carbon fiber reinforced composites of two types, [0 degree/90 degree]{sub 2s} and [0 degree{sub 2}/90 degree{sub 2}]{sub s}. AE signals were detected during the curing process, tensile tests and fracture toughness tests by acoustic emission(AE) measurements, respectively. Tensile strengths showed that the less cure pressurizing steps and the side of [0 degree/90 degree]{sub 2s} specimens had the higher strengths than those of the others. Fracture toughness showed nearly same values in the same temperature region, but the higher test temperature had the lower fracture toughness values. In order to examine between fracture behavior of tensile and fracture toughness test and post processing for AE parameters of AE data and observations of microscopy, SEM are carried out respectively.

  20. A study on the fracture behavior of CFRP in tensile and fracture toughness tests by acoustic emission

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang Guk; Oh, Sae Kyoo; Nam, Ki Woo; Kim, Og Gyun [National Fishery University of Pusan, Pusan (Korea, Republic of)

    1995-01-01

    The Study was carried out to analyze the fracture behavior and the acoustic emission(AE) characteristics and to find the relationship among tensile strength, fracture toughness and cure pressure in cure process of the carbon fiber reinforced composites of two types, [0 deg/90 deg]{sub 2s} and [0 deg{sub 2}/90 deg{sub 2}]{sub s}. AE signals were detected during the curing process, tensile tests and fracture toughness tests by acoustic emission(AE) measurements, respectively. Tensile strengths showed that the less cure pressurizing steps and the side of [0 deg/90 deg]{sub 2s} specimens had the higher strengths than those of the others. Fracture toughness by the change of test temperature showed nearly same values in the same temperature region, but the higher test temperature had the lower fracture toughness values. In order to examine the relationship between fracture behavior of CFRP in tensile and fracture toughness tests and AE signals, the post processing for AE parameters of AE data and the observations of microscope and SEM have been carried out respectively. (author)