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Sample records for tough hypereutectic high

  1. Microstructure Evaluation and Wear-Resistant Properties of Ti-alloyed Hypereutectic High Chromium Cast Iron

    OpenAIRE

    Liu, Qiang

    2013-01-01

    High chromium cast iron (HCCI) is considered as one of the most useful wear resistance materials and their usage are widely spread in industry. The mechanical properties of HCCI mainly depend on type, size, number, morphology of hard carbides and the matrix structure (γ or α). The hypereutectic HCCI with large volume fractions of hard carbides is preferred to apply in wear applications. However, the coarser and larger primary M7C3 carbides will be precipitated during the solidification of the...

  2. Study on fragmentation and dissolution behavior of carbide in a hot-rolled hypereutectic high chromium cast iron

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fei; Jiang, Yehua, E-mail: jiangyehua@kmust.edu.cn; Xiao, Han; Tan, Jun

    2015-01-05

    Highlights: • The method to prepare Carbon steel/High chromium iron is totally new. • High chromium iron can achieve small plastic deformation during hot rolling process. • Carbides in high chromium irons are crushed, refined obviously and becoming isolated, which is benefit to improve the impact toughness. • The carbide fragmentation and dissolution behavior of the hot-rolled HCCI were analyzed. - Abstract: A sandwich-structured composite containing a hypereutectic high chromium cast iron (HCCI) and low carbon steel (LCS) claddings was newly fabricated by centrifugal casting, then the blank was hot-rolled into composite plate. The carbide fragmentation and dissolution behavior of the hot-rolled HCCI were analyzed. During hot rolling, significant refinement of carbides was discovered in hot-rolled HCCI specimens. The carbides were broken and partly dissolved into the austenite matrix. The results show that carbides are firstly dissolved under the action of stress. There are grooves appeared at the boundaries of the carbides. The grooves reduce the cross section of the carbide. When the cross section of the carbide reaches to the required minimum critical cross section, the carbide breaks through the tensile force. After break, carbides continue to dissolve since more interfaces between the matrix and carbides are generated. The secondary carbides precipitated due to the dissolution are index as fcc and stacking faults parallel to the {1 1 1} are observed.

  3. Morphology transition of the primary silicon particles in a hypereutectic A390 alloy in high pressure die casting.

    Science.gov (United States)

    Wang, J; Guo, Z; Song, J L; Hu, W X; Li, J C; Xiong, S M

    2017-11-03

    The microstructure of a high-pressure die-cast hypereutectic A390 alloy, including PSPs, pores, α-Al grains and Cu-rich phases, was characterized using synchrotron X-ray tomography, together with SEM, TEM and EBSD. The Cu-rich phases exhibited a net morphology and distributed at the boundaries of the α-Al grains, which in turn surrounded the PSPs. Statistical analysis of the reconstructed 1000 PSPs showed that both equivalent diameter and shape factor of the PSPs exhibited a unimodal distribution with peaks corresponding to 25 μm and 0.78, respectively.) PSPs morphology with multiple twinning were observed and morphological or growth transition of the PSPs from regular octahedral shape (with a shape factor of 0.85 was mainly caused by the constraint of the Cu-rich phases. In particular, the presence of the Cu-rich phases restricted the growth of the α-Al grains, inducing stress on the internal silicon particles, which caused multiple twinning occurrence with higher growth potential and consequently led to growth transitions of the PSPs.

  4. Study on the nanostructure formation mechanism of hypereutectic Al–17.5Si alloy induced by high current pulsed electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Bo, E-mail: gaob@smm.neu.edu.cn [School of Materials and Metallurgy, Northeastern University, Shenyang 110004 (China); Hu, Liang [School of Materials and Metallurgy, Northeastern University, Shenyang 110004 (China); Li, Shi-wei [School of Materials and Metallurgy, Northeastern University, Shenyang 110004 (China); Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093 (China); Hao, Yi [School of Materials and Metallurgy, Northeastern University, Shenyang 110004 (China); Zhang, Yu-dong [Laboratoire d’Etude des Textures et Applications aux Matériaux (LETAM, UMR-CNRS 7078), Université Paul Verlaine de Metz, Ile du Saulcy, Metz 57012 (France); Tu, Gan-feng [School of Materials and Metallurgy, Northeastern University, Shenyang 110004 (China); Grosdidier, Thierry [Laboratoire d’Etude des Textures et Applications aux Matériaux (LETAM, UMR-CNRS 7078), Université Paul Verlaine de Metz, Ile du Saulcy, Metz 57012 (France)

    2015-08-15

    This work investigates the nanostructure forming mechanism of hypereutectic Al–17.5Si alloy associated with the high current pulsed electron beam (HCPEB) treatment with increasing number of pulses by electron backscatter diffraction (EBSD) and SEM. The surface layers were melted and resolidified rapidly. The treated surfaces show different structural characteristics in different compositions and distribution zones. The top melted-layer zone can be divided into three zones: Si-rich, Ai-rich, and intermediate zone. The Al-rich zone has a nano-cellular microstructure with a diameter of ∼100 nm. The microstructure in the Si-rich zone consists of fine, dispersive, and spherical nano-sized Si crystals surrounded by α(Al) cells. Some superfine eutectic structures form in the boundary of the two zones. With the increase of number of pulses, the proportion of Si-rich zone to the whole top surface increases, and more cellular substructures are transformed to fine equiaxed grain. In other words, with increasing number of pulses, more Si elements diffuse to the Al-rich zone and provide heterogeneous nucleation sites, and Al grains are refined dramatically. Moreover, the relationship between the substrate Si phase and crystalline phase is determined by EBSD; that is, (1 1 1){sub Al}//(0 0 1){sub Si} with a value of disregistry δ at approximately 5%. The HCPEB technique is a versatile technique for refining the surface microstructure of hypereutectic Al–Si alloys.

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

    Indian Academy of Sciences (India)

    Unknown

    to formulate a test procedure for Charpy testing of TMT rebar. In this paper the CVN impact toughness of some. 600 MPa yield stress TMT rebars has been discussed with particular reference to the effects of phosphorus, molybdenum and chromium on toughness. 2. Materials and test procedures. Steel for high strength TMT ...

  6. 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

  7. Development of a high strength high toughness ausferritic steel

    Energy Technology Data Exchange (ETDEWEB)

    Putatunda, Susil K., E-mail: sputa@eng.wayne.edu [Department of Chemical Engineering and Material Science, Wayne State University, 5050 Anthony Wayne Dr., Detroit, MI 48202 (United States); Singar, Arjun V. [Department of Chemical Engineering and Material Science, Wayne State University, 5050 Anthony Wayne Dr., Detroit, MI 48202 (United States); Tackett, Ronald; Lawes, Gavin [Department of Physics and Astronomy, Wayne State University, Detroit, MI 48201 (United States)

    2009-07-15

    A new ausferritic steel with high strength and exceptionally high fracture toughness has been developed. This steel has been synthesized integrating concepts from Austempered Ductile Cast Iron (ADI) technology. The influence of the austempering temperature on the microstructure and mechanical properties of this steel at room temperature and ambient atmosphere has been examined. The effect of microstructure on the plane strain fracture toughness and on the magnetic, electrical, and thermal properties was also investigated. Compact tension and cylindrical tensile specimens prepared from the low alloy medium carbon steel with high silicon content were initially austenitized at 927 deg. C for 2 h and then subsequently austempered at several temperatures between 260 deg. C (500 F) and 400 deg. C (750 F) to produce different microstructures. The microstructures were characterized by X-ray diffraction, scanning electron microscopy and optical metallography. A combination of exceptionally high yield strength (1336 MPa) and a high fracture of toughness of 116 MPa{radical}m (a value comparable to maraging steel) was obtained in this steel after austempering at 316 deg. C (600 F) for 2 h. Potential applications of this steel include the inexpensive fabrication of armored plates and components requiring high reliability and durability.

  8. Inoculated Slightly Hypereutectic Gray Cast Irons

    Science.gov (United States)

    Chisamera, Mihai; Riposan, Iulian; Stan, Stelian; Militaru, Cristina; Anton, Irina; Barstow, Michael

    2012-03-01

    The current experimental investigation in this article was designed to characterize the structure of mold (M) and ladle (L) inoculated, low-S (0.025 wt.% S), low-Al (0.003 wt.% Al), slightly hypereutectic (CE = 4.4-4.5 wt.%) electric melted gray irons, typical for high performance thin-wall castings. It describes the effect of a Ca, Al, Zr-FeSi inoculant addition of 0-0.25 wt.% on structure characteristics, and compares to similar treatments with hypoeutectic irons (3.5-3.6 wt.% CE, 0.025 wt.% S, and 0.003 wt.% Al). A complex structure including primary graphite, austenite dendrites, and eutectic cells is obtained in hypereutectic irons, as the result of nonequilibrium solidification following the concept of a coexisting region. Dendrites appear to be distributed between eutectic cells at higher eutectic undercooling, while in inoculated irons and for lower undercooling, the eutectic cells are "reinforced" by eutectic austenite dendrites. A Zr, Ca, Al-FeSi alloy appears to be an effective inoculant in low S, low Al, gray cast irons, especially for a late inoculation technique, with beneficial effects on both graphite and austenite phases. First, inoculation influenced the nucleation of graphite/eutectic cell, and then their characteristics. A further role of these active elements directly contributed to form nucleation sites for austenite, as complex (Mn,X)S particles.

  9. Microstructure and property of directionally solidified Ni-Si hypereutectic alloy

    Science.gov (United States)

    Cui, Chunjuan; Tian, Lulu; Zhang, Jun; Yu, Shengnan; Liu, Lin; Fu, Hengzhi

    2016-03-01

    This paper investigates the influence of the solidification rate on the microstructure, solid/liquid interface, and micro-hardness of the directionally solidified Ni-Si hypereutectic alloy. Microstructure of the Ni-Si hypereutectic alloy is refined with the increase of the solidification rate. The Ni-Si hypereutectic composite is mainly composed of α-Ni matrix, Ni-Ni3Si eutectic phase, and metastable Ni31Si12 phase. The solid/liquid interface always keeps planar interface no matter how high the solidification rate is increased. This is proved by the calculation in terms of M-S interface stability criterion. Moreover, the Ni-Si hypereutectic composites present higher micro-hardness as compared with that of the pure Ni3Si compound. This is caused by the formation of the metastable Ni31Si12 phase and NiSi phase during the directional solidification process.

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

    Indian Academy of Sciences (India)

    Unknown

    fabrication of high strength ceramics. Also, it was felt that the high initial strength is not a solution if the material is readily degraded as a result of service conditions. Further, eliminating flaws did marginal to enhance the reliability or toughness of the ceramic throughout the duration of its operational lifetime. Subsequently, the ...

  11. Biomimetic polysaccharide nanocomposites of high cellulose content and high toughness.

    Science.gov (United States)

    Svagan, Anna J; Samir, My A S Azizi; Berglund, Lars A

    2007-08-01

    Plant cell walls combine mechanical stiffness, strength and toughness despite a highly hydrated state. Inspired by this, a nanostructured cellulose network is combined with an almost viscous polysaccharide matrix in the form of a 50/50 amylopectin-glycerol blend. Homogeneous films with a microfibrillated cellulose (MFC) nanofiber content in the range of 10-70 wt % are successfully cast. Characterization is carried out by dynamic mechanical analysis, field-emission scanning electron microscopy, X-ray diffraction, and mercury density measurements. The MFC is well dispersed and predominantly oriented random-in-the-plane. High tensile strength is combined with high modulus and very high work of fracture in the nanocomposite with 70 wt % MFC. The reasons for this interesting combination of properties include nanofiber and matrix properties, favorable nanofiber-matrix interaction, good dispersion, and the ability of the MFC network to maintain its integrity to a strain of at least 8%.

  12. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-07-01

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

  14. Halo Evolution of Hypereutectic Al-17.5Si Alloy Treated with High-Current Pulsed Electron Beam

    Directory of Open Access Journals (Sweden)

    L. Hu

    2015-01-01

    Full Text Available Halo evolution of an Al-17.5Si alloy surface after treatment with increasing pulse numbers of a high-current pulsed electron beam (HCPEB was investigated. A halo is a ring microstructure resembling a bull’s eye. SEM results indicate that the nanocrystallization of halo induced by HCPEB treatment leads to gradual diffusion of the Si phase. Multiple pulses numbers cause the Si phase to be significantly refined and uniformly distributed. In addition, nanosilicon particles with a grain size of 30~100 nm were formed after HCPEB treatment, as shown by TEM observation. XRD results indicate that Si diffraction peaks broadened after HCPEB treatment. The microhardness tests demonstrate that the microhardness at the midpoint from the halo edge to center decreased sharply from 9770.7 MPa at 5 pulses to 2664.14 MPa at 25 pulses. The relative wear resistance of a 15-pulse sample is effectively improved by a factor of 6.5, exhibiting optimal wear resistance.

  15. Microstructural evolution and mechanical properties of hypereutectic ...

    Indian Academy of Sciences (India)

    Administrator

    F F WU*, S T LI, G A ZHANG and F JIANG. School of Materials Science and Engineering, Liaoning University of Technology, Jinzhou 121001, China. MS received 6 July 2013; revised 7 October 2013. Abstract. The microstructural evolution and mechanical properties of a hypereutectic Al–Si alloy processed by liquid die ...

  16. Grain refinement of high strength steels to improve cryogenic toughness

    Science.gov (United States)

    Rush, H. F.

    1985-01-01

    Grain-refining techniques using multistep heat treatments to reduce the grain size of five commercial high-strength steels were investigated. The goal of this investigation was to improve the low-temperature toughness as measured by Charpy V-notch impact test without a significant loss in tensile strength. The grain size of four of five alloys investigated was successfully reduced up to 1/10 of original size or smaller with increases in Charpy impact energy of 50 to 180 percent at -320 F. Tensile properties were reduced from 0 to 25 percent for the various alloys tested. An unexpected but highly beneficial side effect from grain refining was improved machinability.

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

    International Nuclear Information System (INIS)

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

    1985-10-01

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

  18. Are adolescents with high mental toughness levels more resilient against stress?

    Science.gov (United States)

    Gerber, Markus; Kalak, Nadeem; Lemola, Sakari; Clough, Peter J; Perry, John L; Pühse, Uwe; Elliot, Catherine; Holsboer-Trachsler, Edith; Brand, Serge

    2013-04-01

    Mental toughness has been explored predominantly within sport contexts. Nevertheless, it is difficult to conceive mental toughness as only applicable to athletes. This study examines whether mentally tough participants exhibit resilience against stress. This is a cross-sectional study based on two different samples: Sample 1 consisted of 284 high school students (99 males, 185 females, M = 18.3 years). Sample 2 consisted of 140 first through fifth semester undergraduate students (53 males, 87 females, M = 20.0 years). Participants provided information about their level of perceived stress (10-item Perceived Stress Scale), mental toughness (48-item Mental Toughness Questionnaire) and depressive symptoms (Beck Depression Inventory). Consistent across the two samples, mental toughness mitigated the relationship between high stress and depressive symptoms. The interaction between stress and mental toughness explained 2% of variance in the adolescent sample and 10% of variance among young adults. The promotion of protective factors that foster resilient adaptation is a relevant issue. Mental toughness may appeal to individuals that are typically difficult to be reached with health interventions. Because mental toughness is part of young people's daily speech, it may serve as a less academic resource than other health psychology concepts. Copyright © 2012 John Wiley & Sons, Ltd.

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

    International Nuclear Information System (INIS)

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

    1991-01-01

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

  20. Design of a low-alloy high-strength and high-toughness martensitic steel

    Science.gov (United States)

    Zhao, Yan-jun; Ren, Xue-ping; Yang, Wen-chao; Zang, Yue

    2013-08-01

    To develop a high strength low alloy (HSLA) steel with high strength and high toughness, a series of martensitic steels were studied through alloying with various elements and thermodynamic simulation. The microstructure and mechanical properties of the designed steel were investigated by optical microscopy, scanning electron microscopy, tensile testing and Charpy impact test. The results show that cementite exists between 500°C and 700°C, M7C3 exits below 720°C, and they are much lower than the austenitizing temperature of the designed steel. Furthermore, the Ti(C,N) precipitate exists until 1280°C, which refines the microstructure and increases the strength and toughness. The optimal alloying components are 0.19% C, 1.19% Si, 2.83% Mn, 1.24% Ni, and 0.049% Ti; the tensile strength and the V notch impact toughness of the designed steel are more than 1500 MPa and 100 J, respectively.

  1. Tough hybrid ceramic-based material with high strength

    International Nuclear Information System (INIS)

    Guo, Shuqi; Kagawa, Yutaka; Nishimura, Toshiyuki

    2012-01-01

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

  2. Development of high strength high toughness third generation advanced high strength steels

    Science.gov (United States)

    Martis, Codrick John

    Third generation advanced high strength steels (AHSS's) are emerging as very important engineering materials for structural applications. These steels have high specific strength and thus will contribute significantly to weight reduction in automotive and other structural component. In this investigation two such low carbon low alloy steels (LCLA) with high silicon content (1.6-2wt %) has been developed. These two steel alloys were subjected to single step and two step austempering in the temperature range of 260-399°C to obtain desired microstructures and mechanical properties. Austempering heat treatment was carried out for 2 hours in a molten salt bath. The microstructures were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and optical metallography. Quantitative analysis was carried out by image analysis technique. The effect of austempering temperature on the mechanical properties of these two alloys was examined. The influence of microstructures on the mechanical properties of alloys was also studied. Austempering heat treatment resulted in fine carbide free bainitic ferrite and high carbon austenite microstructure in the samples austempered above Ms temperature, whereas tempered martensite and austenite microstructure was obtained in samples austempered below Ms temperature. Yield strength, tensile strength and fracture toughness were found to increase as the austempering temperature decreases, whereas ductility increases as the austempering temperature increases. Tensile strength in the range of 1276MPa -1658 MPa and the fracture toughness in the range of 80-141MPa√m were obtained in these two steels. Volume fractions of different phases present and their lath sizes are related to the mechanical properties. Austempered samples consisting of mixed microstructure of bainitic ferrite and tempered martensite phases resulted in the exceptional combination of strength and toughness.

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

    International Nuclear Information System (INIS)

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

    1999-01-01

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

  4. Effect of load on the tribological properties of hypereutectic Al-Si alloy under boundary lubrication conditions

    Science.gov (United States)

    Kumar, Parveen; Wani, M. F.

    2017-11-01

    Researchers reported that the IC engine components (piston, cylinder liner etc) fail due to the friction losses (~45%) and wear losses (~25-40%). So the demand of light weight, low friction and wear resistance alloys increases day by day, which reduces the emission and increases the efficiency of the IC engine. In this connection, tribological tests on hypereutectic Al-25Si alloy were performed using a ball-on-disk configuration under dry and lubricated sliding conditions. Hypereutectic Al-25Si alloy was prepared by rapid solidification process with T6 condition. T6 condition improves the friction, wear and mechanical properties of the alloy. Friction coefficient and wear rate of the alloy was measured under high loads ranging from 100 to 300 N. It was found that the friction coefficient (COF) and wear rate of hypereutectic Al-25Si alloy/steel tribo pair increased with increase in load. Significant reduction in COF and wear rate was accomplished with SAE20W50 engine oil and Si particles act as solid lubricant. Optical microscope, 3D surface profilometer and scanning electron microscope (SEM) coupled with an energy dispersive spectrometer (EDS) were used for characterization the worn surface morphologies. The morphology, size and distribution of high Si particles due to its fabrication process caused the improvements in COF and wear rate under lubricated conditions. Adhesive wear, abrasive wear and plastic deformation acted as the dominant wear mechanism for hypereutectic Al-25Si alloy.

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

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Devender [Mechanical Engineering Department, Thapar University, Patiala, Punjab (India); Singh, K., E-mail: kusingh@thapar.edu [School of Physics and Materials Science, Thapar University, Patiala, Punjab (India)

    2016-04-29

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

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  7. Engineering tough, highly compressible, biodegradable hydrogels by tuning the network architecture.

    Science.gov (United States)

    Gu, Dunyin; Tan, Shereen; Xu, Chenglong; O'Connor, Andrea J; Qiao, Greg G

    2017-06-20

    By precisely tuning the network architecture, tough, highly compressible hydrogels were engineered. The hydrogels were made by interconnecting high-functionality hydrophobic domains through linear tri-block chains, consisting of soft hydrophilic middle blocks, flanked with flexible hydrophobic blocks. In showing their applicability, the efficient encapsulation and prolonged release of hydrophobic drugs were achieved.

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

    International Nuclear Information System (INIS)

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

    1999-01-01

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

  9. Determination of melting and solidification enthalpy of hypereutectic silumins

    Directory of Open Access Journals (Sweden)

    J. Piątkowski

    2008-04-01

    Full Text Available The study was related with determination of the values of enthalpy of melting and solidification of hypereutectic AlSi18, AlSi21 and AlSi24 silumins modified with phosphorus in the form of Cu-P. The calorimetry, preceded by thermal analysis and derivative thermal analysis (TA and DTA, respectively was carried out on a high-temperature scanning calorimeter, model MHTC-96, made by SETARAM, applying the method of direct determination of parameters of the high-temperature process, and in particular of the enthalpy of phase transformations. Modern control and measuring instruments coupled with PC computer provide a very precise tool for determination of these transformations. An additional advantage was development of appropriate software called „SETSOFT”, owing to which it was possible to determine in an easy way the enthalpy of the investigated phase transformations. Moreover, an additional thermal effect, related most probably with pre-eutectic crystallization of primary silicon, was observed and confirmed by calorimetric examinations.

  10. 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.

  11. Fracture toughness improvement of austempered high silicon steel by titanium, vanadium and rare earth elements modification

    International Nuclear Information System (INIS)

    Chen Xiang; Li Yanxiang

    2007-01-01

    The microstructure of austempered high silicon (AHS) steel before and after treating with a modifier containing titanium, vanadium and rare earth elements (so-called Ti-V-RE modifier) and austempered at different temperatures has been investigated. The plane strain fracture toughness of the steel in room temperature and ambient atmosphere has been examined. The microstructure was characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and optical metallography and correlated to the fracture toughness of the steel. The results show that the primary austenite grains are refined, the dendritic austempered structure is eliminated, and the volume of blocky shaped retained austenite is reduced by the addition of Ti-V-RE modifier. Modification with Ti-V-RE modifier can prompt the bainitic ferrite transformation and reduce the volume fraction of retained austenite. High fracture toughness is obtained for AHS steel with the addition of Ti-V-RE modifier when austempered between 350 and 385 deg. C with a retained austenite of 30-35% and the carbon content in the austenite is about 1.9-2%. The fracture toughness of AHS steel by the modification treatment can increase 10-40% than that of unmodified, an optimum value of 85 MPa m 1/2 was obtained when austempered at 385 deg. C

  12. Fracture toughness improvement of austempered high silicon steel by titanium, vanadium and rare earth elements modification

    Energy Technology Data Exchange (ETDEWEB)

    Chen Xiang [Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Li Yanxiang [Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China)]. E-mail: yanxiang@tsinghua.edu.cn

    2007-01-25

    The microstructure of austempered high silicon (AHS) steel before and after treating with a modifier containing titanium, vanadium and rare earth elements (so-called Ti-V-RE modifier) and austempered at different temperatures has been investigated. The plane strain fracture toughness of the steel in room temperature and ambient atmosphere has been examined. The microstructure was characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and optical metallography and correlated to the fracture toughness of the steel. The results show that the primary austenite grains are refined, the dendritic austempered structure is eliminated, and the volume of blocky shaped retained austenite is reduced by the addition of Ti-V-RE modifier. Modification with Ti-V-RE modifier can prompt the bainitic ferrite transformation and reduce the volume fraction of retained austenite. High fracture toughness is obtained for AHS steel with the addition of Ti-V-RE modifier when austempered between 350 and 385 deg. C with a retained austenite of 30-35% and the carbon content in the austenite is about 1.9-2%. The fracture toughness of AHS steel by the modification treatment can increase 10-40% than that of unmodified, an optimum value of 85 MPa m{sup 1/2} was obtained when austempered at 385 deg. C.

  13. 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

    2017-01-01

    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. PMID:28150692

  14. 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.

  15. Solidification of Hypereutectic Thin Wall Ductile Cast Iron

    DEFF Research Database (Denmark)

    Pedersen, Karl Martin; Tiedje, Niels Skat

    2006-01-01

    Hypereutectic ductile iron was cast in green sand moulds with four plates with thickness of 1.5, 2, 3 and 4 mm in each mould. Temperatures were measured in the 3 and 4 mm plate. The temperature curves showed that eutectic solidification was divided into two stages: primary and secondary eutectic...

  16. Compression specific toughness of normal strength steel fiber reinforced concrete (NSSFRC and high strength steel fiber reinforced concrete (HSSFRC

    Directory of Open Access Journals (Sweden)

    Khaled Marara

    2011-01-01

    Full Text Available Compression toughness tests were carried out on concrete cylinders reinforced with three different aspect ratios of hooked-end steel fibers 60, 75, and 83 and six different percentages of steel fibers 0.5, 1.0, 1.25, 1.5, 1.75, and 2.0% by volume of concrete. The w/c ratio used for the normal strength steel fiber reinforced concrete mixes (NSSFRC was 0.55, and the water-cementitious ratio (w/c+s for the high strength fiber reinforced concrete mixes (HSSFRC was 0.31. For each mix, three test cylinders were tested for compression specific toughness. The effect of fiber reinforcement index: volume of fibers × length/diameter ratio on compression specific toughness and also on the relationship between these two properties is presented in this paper. As a result, (a equations are proposed to quantify the effect of fibers on compression toughness ratio of concrete in terms of FRI, (b equations obtained in terms of FRI and compression specific toughness of plain concrete to estimate both compression specific toughness of NSSFRC and HSSFRC (N.m, (c equations obtained which represent the relationship between compression toughness index and FRI for NSSFRC and HSSFRC, respectively, and (d equations obtained to quantify the relationship between compression specific toughness index and fiber reinforcement index for NSSFRC and HSSFRC, respectively. The proposed equations give good correlation with the experimental values.

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

    International Nuclear Information System (INIS)

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

    1996-01-01

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

  18. 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

    2013-12-01

    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 cross-linked, 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 folded domains to unfold. Subsequent collapse and aggregation of unfolded ferredoxin-like domains leads to intertwining of physically and chemically cross-linked 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 domains enables the hydrogel to recover its massive hysteresis. This novel biomaterial may expand the scope of hydrogel applications in tissue engineering.

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

    Indian Academy of Sciences (India)

    Unknown

    However, the ceramic fibres should display sufficient high temperature strength and creep resistance at service temperatures above 1000°C. The ... of covalent and ionic bonding that is characteristic of this class of material. No or very .... 1000°C. Although many commercial carbon and graphite fibres can satisfy most of the ...

  20. Highly Flexible, Multipixelated Thermosensitive Smart Windows Made of Tough Hydrogels.

    Science.gov (United States)

    La, Thanh-Giang; Li, Xinda; Kumar, Amit; Fu, Yiyang; Yang, Shu; Chung, Hyun-Joong

    2017-09-27

    In a cold night, a clear window that will become opaque while retaining the indoor heat is highly desirable for both privacy and energy efficiency. A thermally responsive material that controls both the transmittance of solar radiance (predominantly in the visible and near-infrared wavelengths) and blackbody radiation (mainly in the mid-infrared) can realize such windows with minimal energy consumption. Here, we report a smart coating made from polyampholyte hydrogel (PAH) that transforms from a transparency state to opacity to visible radiation and strengthens opacity to mid-infrared when lowering the temperature as a result of phase separation between the water-rich and polymer-rich phases. To match a typical temperature fluctuation during the day, we fine-tune the phase transition temperature between 25 and 55 °C by introducing a small amount of relatively hydrophobic monomers (0.1 to 0.5 wt % to PAH). To further demonstrate an actively controlled, highly flexible, and high-contrast smart window, we build in an array of electric heaters made of printed elastomeric composite. The multipixelated window offers rapid switching, ∼70 s per cycle, whereas the device can withstand high strain (up to 80%) during operations.

  1. 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.

  2. 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%.

  3. Effect of Different Inoculants on Impact Toughness in High Chromium Cast Iron

    Directory of Open Access Journals (Sweden)

    Siekaniec D.

    2017-06-01

    Full Text Available The present work, presented the study of effect of different inoculants on impact toughness in High Chromium Cast Iron. The molds were pouring in industrial conditions and samples were tested in laboratory in Faculty of Foundry Engineering at AGH. Seven samples were tested - one reference sample, three with different addition of Fe-Ti, and three with different addition of Al. The samples were subjected to impact toughness on Charpy hammer and the hardness test. The presented investigations indicate that for the each inoculant there is an optimal addition at which the sample obtained the highest value of impact toughness. For the Fe-Ti it is 0.66% and for Al is 0.17%. Of all the examined inoculants best results were obtained at a dose of 0.66% Fe-Ti. Titanium is a well-known as a good modifier but very interesting results gives the aluminum. Comparing the results obtained for the Fe-Ti and Al can be seen that in the case of aluminum hardness is more stable. The hardness of all samples is around 40-45 HRC, which is not high for this type of cast iron. Therefore, in future studies it is planned to carry out the heat treatment procedure that may improves hardness.

  4. Stereology of carbide phase in modified hypereutectic chromium cast iron

    Directory of Open Access Journals (Sweden)

    J. Suchoń

    2010-04-01

    Full Text Available In paper are presented results of studies of carbide phase stereology modified hypereutectic wear resistance chromium cast iron which contains carbon about 3,5% and chromium about 25%. Three substances were applied to the modification: boron carbide (B4C, ferroniobium (FeNb and mixture of ferroniobium and rare-earth (RE. The measurements of geometrical features of carbides were conducted on microsection taken from castings wich were cooled with various velocities.

  5. 14. New Impact Test and Arrestability of High-toughness 9% Ni Steel

    OpenAIRE

    Akio, DEGUCHI; Masuo, TADA; Hiroshi, YAJIMA; Mitsubishi Heavy Industries, Ltd.; Mitsubishi Heavy Industries, Ltd.; Mitsubishi Heavy Industries, Ltd.

    1991-01-01

    Recent steel manufacturing produces 9% Ni steels with high toughness through minimizing impurities in steel and improving heat treatment. These 9% Ni steels show ductile fracture and absorbed energy more than 20 kgf min V-Charpy impact test at -196℃, which indicates V-Charpy impact test to be insufficient for the material selection. It is difficult to know the arrestability of these 9% Ni steels through the "surface-notched double tension test" using liquid nitrogen (-196℃) as refrigerant, th...

  6. Thermal annealing recovery of fracture toughness in HT9 steel after irradiation to high doses

    Energy Technology Data Exchange (ETDEWEB)

    Byun, Thak Sang, E-mail: byunts@ornl.gov [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Baek, Jong-Hyuk [Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Anderoglu, Osman; Maloy, Stuart A. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Toloczko, Mychailo B. [Pacific Northwest National Laboratory, Richland, WA 99352 (United States)

    2014-06-01

    The HT9 ferritic/martensitic steel with a nominal chemistry of Fe(bal.)12%Cr1%MoVW has been used as a primary core material for fast fission reactors such as FFTF because of its high resistance to radiation-induced swelling and embrittlement. Both static and dynamic fracture test results have shown that the HT9 steel can become brittle when it is exposed to high dose irradiation at a relatively low temperature (<430 °C). This article aims at a comprehensive discussion on the thermal annealing recovery of fracture toughness in the HT9 steel after irradiation up to 3148 dpa at 378504 °C. A specimen reuse technique has been established and applied to this study: the fracture specimens were tested Charpy specimens or broken halves of Charpy bars (13 × 3 × 4 mm). The post-anneal fracture test results indicated that much of the radiation-induced damage can be recovered by a simple thermal annealing schedule: the fracture toughness was incompletely recovered by 550 °C annealing, while nearly complete or complete recovery occurred after 650 °C annealing. This indicates that thermal annealing is a feasible damage mitigation technique for the reactor components made of HT9 steel. The partial recovery is probably due to the non-removable microstructural damages such as void or gas bubble formation, elemental segregation and precipitation.

  7. Impact Toughness Properties of Nickel- and Manganese-Free High Nitrogen Austenitic Stainless Steels

    Science.gov (United States)

    Mohammadzadeh, Roghayeh; Akbari, Alireza; Mohammadzadeh, Mina

    2016-12-01

    A large amount of manganese (>10 wt pct) in nickel-free high nitrogen austenitic stainless steels (Ni-free HNASSs) can induce toxicity. In order to develop Ni-free HNASSs with low or no manganese, it is necessary to investigate their mechanical properties for biomedical applications. This work aims to study the Charpy V-notch (CVN) impact toughness properties of a Ni- and Mn-free Fe-22.7Cr-2.4Mo-1.2N HNASS plate in the temperature range of 103 K to 423 K (-170 °C to 150 °C). The results show that unlike conventional AISI 316L austenitic stainless steel, the Ni- and Mn-free HNASS exhibits a sharp ductile-to-brittle transition (DBT). The intergranular brittle fracture associated with some plasticity and deformation bands is observed on the fracture surface at 298 K (25 °C). Electron backscattered diffraction (EBSD) analysis of the impact-tested sample in the longitudinal direction indicates that deformation bands are parallel to {111} slip planes. By decreasing the temperature to 273 K, 263 K, and 103 K (0 °C, -10 °C, and -70 °C), entirely intergranular brittle fracture occurs on the fracture surface. The fracture mode changes from brittle fracture to ductile as the temperature increases to 423 K (150 °C). The decrease in impact toughness is discussed on the basis of temperature sensitivity of plastic flow and planarity of deformation mechanism.

  8. Mental toughness and transitions to high school and to undergraduate study

    OpenAIRE

    St Clair-Thompson, Helen; Giles, Rebecca; McGeown, Sarah P.; Putwain, David; Clough, Peter J.; 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 1 examined the relationships between mental toughness and concerns about moving to a new school in 105 children aged 12–13 years of age. The result...

  9. Wear behavior and microstructure of hypereutectic Al-Si alloys prepared by selective laser melting

    Science.gov (United States)

    Kang, Nan; Coddet, Pierre; Liao, Hanlin; Baur, Tiphaine; Coddet, Christian

    2016-08-01

    This work investigates the microstructure and wear behavior of hypereutectic Al-Si alloys, in-situ fabricated using selective laser melting of a mixture of eutectic Al-12Si (wt.%) and pure Si powders. The first observation was that the size and morphology of the Si phase are strongly influenced by the laser power. In addition, it was also observed that a high laser power causes serious evaporation of aluminum during the remelting process. Dry sliding wear test and Vickers microhardness measurements were employed to characterize the mechanical properties of the material. The lowest wear rate of about 7.0 × 10-4 mm3 N-1 m-1 was observed for samples having the highest value of relative density (96%) and microhardness (105 Hv0.3).

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

    Science.gov (United States)

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

    2016-06-01

    Kickboxing is a high-intensity intermittent striking combat sport, which is characterized by complex skills and tactical key actions with short duration. The present study compared and verified the relationship between mental toughness (MT), countermovement jump (CMJ) and medicine ball throw (MBT) power tests by outcomes of high-level kickboxers during National Championship. 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 (SMTQ; based in confidence, constancy and control subscales), before the fights of the 2015 national championship (16 bouts). In statistical analysis, Mann-Withney test and a multiple linear regression were used to compare groups and to observe relationships, respectively, P ≤ 0.05. The present results showed significant differences between losers vs. winners, respectively, of total MT (7(7;8) vs. 11(10.2;11), confidence (3(3;3) vs. 4(4;4)), constancy (2(2;2) vs. 3(3;3)), control (2(2;3) vs. 4(4;4)) subscales and MBT (4.1(4;4.3) vs. 4.6(4.4;4.8)). The multiple linear regression showed a strong associations between MT results and outcome (r = 0.89), MBT (r = 0.84) and CMJ (r = 0.73). The findings suggest that MT will be more predictive of performance in those sports and in the outcome of competition.

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

    Science.gov (United States)

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

    2016-01-01

    Background Kickboxing is a high-intensity intermittent striking combat sport, which is characterized by complex skills and tactical key actions with short duration. Objectives The present study compared and verified the relationship between mental toughness (MT), countermovement jump (CMJ) and medicine ball throw (MBT) power tests by outcomes of high-level kickboxers during National Championship. Materials and Methods 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 (SMTQ; based in confidence, constancy and control subscales), before the fights of the 2015 national championship (16 bouts). In statistical analysis, Mann-Withney test and a multiple linear regression were used to compare groups and to observe relationships, respectively, P ≤ 0.05. Results The present results showed significant differences between losers vs. winners, respectively, of total MT (7(7;8) vs. 11(10.2;11), confidence (3(3;3) vs. 4(4;4)), constancy (2(2;2) vs. 3(3;3)), control (2(2;3) vs. 4(4;4)) subscales and MBT (4.1(4;4.3) vs. 4.6(4.4;4.8)). The multiple linear regression showed a strong associations between MT results and outcome (r = 0.89), MBT (r = 0.84) and CMJ (r = 0.73). Conclusions The findings suggest that MT will be more predictive of performance in those sports and in the outcome of competition. PMID:27625755

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

    Science.gov (United States)

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

    2013-12-01

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

  13. 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…

  14. An Investigation of Metallurgical Factors Which Affect Fracture Toughness of Ultra-High Strength Steels

    Science.gov (United States)

    electron microscopy were used to characterize the structure and morphology, while both Charpy V-notch impact tests and plane strain fracture toughness...correlation between the Charpy impact test results and the fracture toughness results.... tests were used to determine the fracture properties. The normal commercial heat treatment resulted in the formation of some bainite in all the alloys

  15. The Thin Line: A Phenomenological Study of Mental Toughness and Decision Making in Elite High-Altitude Mountaineers.

    Science.gov (United States)

    Crust, Lee; Swann, Christian; Allen-Collinson, Jacquelyn

    2016-12-01

    Mental toughness (MT) is a key psychological variable related to achievement in performance domains and perseverance in challenging circumstances. We sought to understand the lived experiences of mentally tough high-altitude mountaineers, focusing primarily upon decisions to persevere or abort summit attempts. Phenomenological interviews were conducted with 14 mountaineers including guides, expedition leaders, and doctors (M age = 44 years). A content analysis was employed to identify key themes in the data. Participants emphasized the importance of MT in extreme environments and described rational, flexible, and vigilant decision-making. Turning around without summiting was the toughest decision reported, with recognition of the thin line between persevering and overstretching. In contrast to much MT literature, mountaineers accepted limits, demonstrated restraint, and sacrificed personal goals to aid others. Costly perseverance was also reported with some mountaineers described as "too tough": overcompetitive, goal-obsessed, and biased decision-makers. These findings revealed both benefits and dangers of MT in mountaineering.

  16. Evaluation of a high fracture toughness composite ceramic for dental applications.

    Science.gov (United States)

    Aboushelib, Moustafa N; Kleverlaan, Cornelis J; Feilzer, Albert J

    2008-10-01

    The introduction of yttrium partially stabilized zirconia polycrystals (Y-TZP) has pushed the application limits of all-ceramic restorations. The mechanical properties of these materials can be further improved by the addition of a secondary dopant phase. The aim of this work was to evaluate the properties of a new nano-composite ceramic used as a dental framework material. The properties of a new ceria-stabilized tetragonal zirconia polycrystal co-doped with alumina (Ce-TZP-Al) were investigated. Y-TZP was used as control. Sixty bars (20 x 2.5 x 1.5 mm(3)) from each material were prepared by cutting CAD/CAM milling blocks. Twenty specimens were used to measure the 4-point flexural strength and the modulus of elasticity of the tested materials. The remaining specimens were used to measure the fracture toughness using indentation strength (IS), single edge notched beam (SENB), and fractography (FR). The thermal expansion coefficient (TEC) was measured using temperature expansion diagrams. The bond strength of the two framework materials to two esthetic veneer ceramics was tested using the microtensile bond strength test (MTBS). Finally, scanning electron microscopy (SEM) and energy dispersive X-ray microanalysis (EDX) were used to analyze the internal structure of the materials. One- and two-way analysis of variance (ANOVA) and Bonferroni post hoc tests were used to analyze the data (alpha= 0.5). The flexural strength and modulus of elasticity of Ce-TZP-Al (856 MPa, 170 GPa) were significantly weaker (p TEC for the two materials was relatively similar, 10.1 microm/ degrees C and 10.4 mum/ degrees C, respectively. Regarding MTBS values, Ce-TZP-Al had significantly lower bond strength values (p nano-composite ceramic, its very low bond strength to esthetic veneers leaves such layered restorations highly susceptible to delamination and chipping under function. Further studies are needed to enhance the surface stability of this high fracture toughness ceramic.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-01-01

    The temperature dependence of fracture toughness in HT9 steel irradiated to 3–145 dpa at 380–503 degrees*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 *3mm* 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 <430 *degreesC, the fracture toughness of irradiated HT9 increased with the test temperature, reached an upper shelf of 180—200 MPa*m^.5 at 350–450 degrees*C, and then decreased with the test temperature. At an irradiation temperature >430 degrees*C, the fracture toughness was nearly unchanged up to about 450 *degreesC and decreased slowly with test temperatures in a higher temperature range. Such a rather monotonic test temperature dependence after high-temperature irradiation is similar to that observed for an archive material generally showing a higher degree of toughness. A brittle fracture without stable crack growth occurred in only a few 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.

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

    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 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 3mm 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 <430 C, the fracture toughness of irradiated HT9 increased with the test temperature, reached an upper shelf of 180 200 MPa ffiffiffiffiffi m p at 350 450 C, and then decreased with the test temperature. At an irradiation temperatureP430 C, the fracture toughness was nearly unchanged up to about 450 C and decreased slowly with test temperatures in a higher temperature range. Such a rather monotonic test temperature dependence after high-temperature irradiation is similar to that observed for an archive material generally showing a higher degree of toughness. A brittle fracture without stable crack growth occurred in only a few 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Baek, Jong-Hyuk, E-mail: jhbaek@kaeri.re.kr [Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Byun, Thak Sang [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Maloy, Start A. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Toloczko, Mychailo B. [Pacific Northwest National Laboratory, Richland, WA 99352 (United States)

    2014-01-15

    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 <430 °C, the fracture toughness of irradiated HT9 increased with the test temperature, reached an upper shelf of 180–200MPa√(m) at 350–450 °C, and then decreased with the test temperature. At an irradiation temperature ⩾430 °C, the fracture toughness was nearly unchanged up to about 450 °C and decreased slowly with test temperatures in a higher temperature range. Such a rather monotonic test temperature dependence after high-temperature irradiation is similar to that observed for an archive material generally showing a higher degree of toughness. A brittle fracture without stable crack growth occurred in only a few 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.

  20. 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.

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

    Science.gov (United States)

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

    2016-05-11

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

  2. Thermal annealing recovery of fracture toughness in HT9 steel after irradiation to high doses

    Science.gov (United States)

    Byun, Thak Sang; Baek, Jong-Hyuk; Anderoglu, Osman; Maloy, Stuart A.; Toloczko, Mychailo B.

    2014-06-01

    The HT9 ferritic/martensitic steel with a nominal chemistry of Fe(bal.)12%Cr1%MoVW has been used as a primary core material for fast fission reactors such as FFTF because of its high resistance to radiation-induced swelling and embrittlement. Both static and dynamic fracture test results have shown that the HT9 steel can become brittle when it is exposed to high dose irradiation at a relatively low temperature (steel after irradiation up to 3148 dpa at 378504 °C. A specimen reuse technique has been established and applied to this study: the fracture specimens were tested Charpy specimens or broken halves of Charpy bars (13 × 3 × 4 mm). The post-anneal fracture test results indicated that much of the radiation-induced damage can be recovered by a simple thermal annealing schedule: the fracture toughness was incompletely recovered by 550 °C annealing, while nearly complete or complete recovery occurred after 650 °C annealing. This indicates that thermal annealing is a feasible damage mitigation technique for the reactor components made of HT9 steel. The partial recovery is probably due to the non-removable microstructural damages such as void or gas bubble formation, elemental segregation and precipitation.

  3. Solvent-free preparation of high-toughness epoxy--SWNT composite materials.

    Science.gov (United States)

    González-Domínguez, Jose M; Ansón-Casaos, Alejandro; Díez-Pascual, Ana M; Ashrafi, Behnam; Naffakh, Mohammed; Backman, David; Stadler, Hartmut; Johnston, Andrew; Gómez, Marian; Martínez, M Teresa

    2011-05-01

    Multicomponent nanocomposite materials based on a high-performance epoxy system and single-walled carbon nanotubes (SWNTs) have been prepared. The noncovalent wrapping of nitric acid-treated SWNTs with a PEO-based amphiphilic block copolymer leads to a highly disaggregated filler with a boosted miscibility in the epoxy matrix, allowing its dispersion without organic solvents. Although direct dispersion of acid-treated SWNTs results in modestly improved epoxy matrix mechanical properties, the incorporation of wrapped SWNTs produces a huge increase in toughness (276% improvement at 0.5 wt % loading) and impact strength (193% at 0.5 wt % loading) with no detrimental effect on the elastic properties. A synergistic effect between SWNTs and the block copolymer is revealed on the basis of tensile and impact strength results. Atomic force microscopy has been applied, obtaining stiffness mappings that identify nanostructure features responsible of the dynamic mechanical behavior. The electrical percolation threshold is greatly reduced, from 0.31 to 0.03 wt % SWNTs when block copolymer-wrapped SWNTs are used, and all the measured conductivity values increased up to a maximum of 7 orders of magnitude with respect to the baseline matrix (1 wt % wrapped-SWNTs loading). This approach provides an efficient way to disperse barely dispersible SWNTs without solvents into an epoxy matrix, and to generate substantial improvements with small amounts of SWNTs.

  4. TOUGH2 software qualification

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-02-01

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

  5. TOUGH2 software qualification

    International Nuclear Information System (INIS)

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

    1996-02-01

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

  6. 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 test temperature, reached an upper shelf of 180-200 MPa √{m} at 350-450 °C, and then decreased with the test temperature. At an irradiation temperature ⩾430 °C, the fracture toughness was nearly unchanged up to about 450 °C and decreased slowly with test temperatures in a higher temperature range. Such a rather monotonic test temperature dependence after high-temperature irradiation is similar to that observed for an archive material generally showing a higher degree of toughness. A brittle fracture without stable crack growth occurred in only a few 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.

  7. Low-birefringent and highly tough nanocellulose-reinforced cellulose triacetate.

    Science.gov (United States)

    Soeta, Hiroto; Fujisawa, Shuji; Saito, Tsuguyuki; Berglund, Lars; Isogai, Akira

    2015-05-27

    Improvement of the mechanical and thermal properties of cellulose triacetate (CTA) films is required without sacrificing their optical properties. Here, poly(ethylene glycol) (PEG)-grafted cellulose nanofibril/CTA nanocomposite films were fabricated by casting and drying methods. The cellulose nanofibrils were prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, and amine-terminated PEG chains were grafted onto the surfaces of the TEMPO-oxidized cellulose nanofibrils (TOCNs) by ionic bonds. Because of the nanosize effect of TOCNs with a uniform width of ∼3 nm, the PEG-TOCN/CTA nanocomposite films had high transparency and low birefringence. The grafted PEG chains enhanced the filler-matrix interactions and crystallization of matrix CTA molecules, resulting in the Young's modulus and toughness of CTA film being significantly improved by PEG-grafted TOCN addition. The coefficient of thermal expansion of the original CTA film was mostly preserved even with the addition of PEG-grafted TOCNs. These results suggest that PEG-TOCNs are applicable to the reinforcement for transparent optical films.

  8. A new method of determining the J-integral fracture toughness of very tough polymers: application to ultra high molecular weight polyethylene.

    Science.gov (United States)

    Lewis, G; Nyman, J S

    1999-01-01

    The thrust of the present work was the development of a new modification to the ASTM E813-89 method for determining the J-integral fracture toughness, JIc, of ductile polymers. The advantages and limitations of the modification, vis a vis the ASTM E813-89 and the hysteresis methods, are presented. The modification was then applied to investigate the effect of sterilization method on the JIc of ultra-high-molecular-weight polyethylene (UHMWPE) specimens that were subsequently aged (heated, in a cylindrical pressure vessel, in oxygen gas at 507 kPa and 70 degrees C for 14 d). Relative to the unsterilized material, it was found that gamma-irradiating the polymer leads to a significant drop in its JIc, while sterilization using either ethylene oxide or gas plasma produced no effect on its JIc. The clinical implications of the present results for the in vivo performance of UHMWPE counterfaces, and, hence, hip and knee arthroplasties, are fully discussed.

  9. Effect of Heat Treatment on the Impact Toughness of `High-Chromium Cast Iron - Low Alloy Steel' Bimetal Components

    Science.gov (United States)

    Özdemir, Z.

    2017-03-01

    A bimetallic `low-alloy steel - high-chromium cast iron' composite obtained by successive sand casting is studied and shown to have good cohesion on the interface and no casting defects. The hardness and the impact toughness of the bimetal increase simultaneously. The microstructure is more homogeneous after diffusion annealing at 1040°C, rapid cooling, and 3-h tempering at 270°C.

  10. Fracture strength of the particulate-reinforced ultra-high temperature ceramics based on a temperature dependent fracture toughness model

    Science.gov (United States)

    Wang, Ruzhuan; Li, Weiguo; Ji, Baohua; Fang, Daining

    2017-10-01

    The particulate-reinforced ultra-high temperature ceramics (pUHTCs) have been particularly developed for fabricating the leading edge and nose cap of hypersonic vehicles. They have drawn intensive attention of scientific community for their superior fracture strength at high temperatures. However, there is no proper model for predicting the fracture strength of the ceramic composites and its dependency on temperature. In order to account for the effect of temperature on the fracture strength, we proposed a concept called energy storage capacity, by which we derived a new model for depicting the temperature dependent fracture toughness of the composites. This model gives a quantitative relationship between the fracture toughness and temperature. Based on this temperature dependent fracture toughness model and Griffith criterion, we developed a new fracture strength model for predicting the temperature dependent fracture strength of pUHTCs at different temperatures. The model takes into account the effects of temperature, flaw size and residual stress without any fitting parameters. The predictions of the fracture strength of pUHTCs in argon or air agreed well with the experimental measurements. Additionally, our model offers a mechanism of monitoring the strength of materials at different temperatures by testing the change of flaw size. This study provides a quantitative tool for design, evaluation and monitoring of the fracture properties of pUHTCs at high temperatures.

  11. Preparation and characterization of poly(vinyl alcohol)/sodium alginate hydrogel with high toughness and electric conductivity.

    Science.gov (United States)

    Jiang, Xiancai; Xiang, Nanping; Zhang, Hongxiang; Sun, Yujun; Lin, Zhen; Hou, Linxi

    2018-04-15

    Development of bio-based hydrogels with good mechanical properties and high electrical conductivity is of great importance for their excellent biocompatibility and biodegradability. Novel electrically conducive and tough poly(vinyl alcohol)/sodium alginate (PVA/SA) composite hydrogel was obtained by a simple method in this paper. PVA and SA were firstly dissolved in distilled water to form the composite solution and the pure PVA/SA hydrogel was obtained through the freezing/thawing process. The pure PVA/SA hydrogels were subsequently immersed into the saturated NaCl aqueous solution to increase the gel strength and conductivity. The effect of the immersing time on the thermal and mechanical properties of PVA/SA hydrogel was studied. The swelling properties and the antiseptic properties of the obtained PVA/SA hydrogel were also studied. This paper provided a novel way for the preparation of tough hydrogel electrolyte. Copyright © 2018. Published by Elsevier Ltd.

  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. 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…

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

    International Nuclear Information System (INIS)

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

    1992-10-01

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

  15. Mental Toughness, Emotional Intelligence, and Coping Effectiveness: An Analysis of Construct Interrelatedness Among High-Performing Adolescent Male Athletes.

    Science.gov (United States)

    Cowden, Richard G

    2016-12-01

    The purpose of this study was to examine the interrelationships between mental toughness (MT) and two constructs also linked to athletic performance, emotional intelligence (EI) and coping effectiveness. A sample of 151 male adolescent athletes (M age = 15.4 years, SD = 1.3) completed the Sports Mental Toughness Questionnaire, the Self-Rated Emotional Intelligence Scale, and an adapted version of the Coping Effectiveness Scale. The regression and mediation analysis results supported both hypotheses in that (a) EI was a significant predictor of MT and (b) the relationship between EI and coping effectiveness was fully mediated by MT. The findings suggest that EI may be an important mechanism through which mentally tough responses and outcomes are generated. Furthermore, although EI is associated with coping effectiveness, it is the attributes of MT that account for the superior coping effectiveness reported among athletes high in EI. Future research could explore whether MT may be developed through intervention programs that target EI, along with the influence of such programs on athletes' coping effectiveness. © The Author(s) 2016.

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

    Directory of Open Access Journals (Sweden)

    Gutiérrez, Isabel

    2014-12-01

    Full Text Available One of the major challenges in the development of new steel grades is to get increasingly high strength combined with a low ductile brittle transition temperature and a high upper shelf energy. This requires the appropriate microstructural design. Toughness in steels is controlled by different microstructural constituents. Some of them, like inclusions, are intrinsic while others happening at different microstructural scales relate to processing conditions. A series of empirical equations express the transition temperature as a sum of contributions from substitutional solutes, free nitrogen, carbides, pearlite, grain size and eventually precipitation strengthening. Aimed at developing a methodology that could be applied to high strength steels, microstructures with a selected degree of complexity were produced at laboratory in a Nb-microalloyed steel. As a result a model has been developed that consistently predicts the Charpy curves for ferrite-pearlite, bainitic and quenched and tempered microstructures using as input data microstructural parameters. This model becomes a good tool for microstructural design.El desarrollo de nuevos grados de acero se tropieza con frecuencia con la necesidad de incrementar la resistencia mecánica al mismo tiempo que se reduce la temperatura de transición dúctil-frágil y se eleva la energía del palier dúctil. Hacer frente a este reto requiere un diseño microestructural. La tenacidad en aceros está controlada por diferentes constituyentes microestructurales. Algunos de ellos, como las inclusiones son intrínsecos, pero otros que se manifiestan a diferentes escalas microestructurales dependen de las condiciones de proceso. Existen algunas ecuaciones empíricas que permiten calcular para ferrita-perlita en aceros de bajo carbono la temperatura de transición como suma de contribuciones de elementos en solución sólida, nitrógeno libre, carburos, fracción de perlita, tamaño de grano y, eventualmente

  17. 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.

  18. Effect of Casting Die Cooling on Solidification Process and Microstructure of Hypereutectic Al-Si Alloy

    Directory of Open Access Journals (Sweden)

    Władysiak R.

    2016-12-01

    Full Text Available The work is a continuation of research concerning the influence of intensive cooling of permanent mold in order to increase the casting efficiency of aluminium alloys using the multipoint water mist cooling system. The paper presents results of investigation of crystallization process and microstructure of synthetic hypereutectic alloys: AlSi15 and AlSi19. Casts were made in permanent mold cooled with water mist stream. The study was conducted for unmodified silumins on the research station allowing the cooling of the special permanent probe using a program of computer control. Furthermore the study used a thermal imaging camera to analyze the solidification process of hypereutectic silumins. The study demonstrated that the use of mold cooled with water mist stream allows in wide range the formation of the microstructure of hypereutectic silumins. It leads to higher homogeneity of microstructure and refinement of crystallizing phases and also it increases subsequently the mechanical properties of casting.

  19. Thixoforming of an automotive part in A390 hypereutectic Al-Si alloy

    DEFF Research Database (Denmark)

    Kapranos, P.; Kirkwood, D.H.; Atkinson, H.V.

    2003-01-01

    Hypereutectic aluminium–silicon alloys offer the possibility of an in situ natural composite (the silicon acting as the reinforcing phase) with properties that make them attractive for a number of automotive applications. However, conventional casting techniques result in excessive growth...... of a series of hypereutectic alloys based on the A390 composition (17%Si, 5%Cu, 0.5%Mg), their thixoforming, their resulting microstructures and mechanical properties. Finally the thixoforming of an automotive component using an A390 alloy is also described....

  20. Crystallographic orientation-spray formed hypereutectic aluminium-silicon alloys

    Directory of Open Access Journals (Sweden)

    Hamilta de Oliveira Santos

    2005-06-01

    Full Text Available Aluminium-silicon alloys have been wide accepted in the automotive, electric and aerospace industries. Preferred orientation is a very common condition for metals and alloys. Particularly, aluminium induces texture during the forming process. The preparation of an aggregate with completely random crystal orientation is a difficult task. The present work was undertaken to analyse the texture by X-ray diffraction techniques, of three spray formed hypereutectic Al-Si alloys. Samples were taken from a billet of an experimental alloy (alloy 1 and were subsequently hot-rolled and cold-rolled (height reduction, 72% and 70%, respectively. The other used samples, alloys 2 and 3, were taken from cylinders liners. The results from the Laue camera showed texture just in the axial direction of alloy 3. The pole figures also indicated the presence of a typical low intensity deformation texture, especially for alloy 3. The spray formed microstructure, which is very fine, hinders the Al-Si texture formation during mechanical work.

  1. Compression specific toughness of normal strength steel fiber reinforced concrete (NSSFRC) and high strength steel fiber reinforced concrete (HSSFRC)

    OpenAIRE

    Marara,Khaled; Erenb,Özgür; Yitmena,İbrahim

    2011-01-01

    Compression toughness tests were carried out on concrete cylinders reinforced with three different aspect ratios of hooked-end steel fibers 60, 75, and 83 and six different percentages of steel fibers 0.5, 1.0, 1.25, 1.5, 1.75, and 2.0% by volume of concrete. The w/c ratio used for the normal strength steel fiber reinforced concrete mixes (NSSFRC) was 0.55, and the water-cementitious ratio (w/c+s) for the high strength fiber reinforced concrete mixes (HSSFRC) was 0.31. For each mix, three tes...

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

    Science.gov (United States)

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

    1976-01-01

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

  3. Numerical modelling of thin-walled hypereutectic ductile cast iron parts

    DEFF Research Database (Denmark)

    Pedersen, Karl Martin; Hattel, Jesper Henri; Tiedje, Niels Skat

    2006-01-01

    Solidification of hypereutectic thin-walled ductile cast iron has been modelled in one dimension taking into account the precipitation of off-eutectic austenite dendrites during solidification. The simulations have been compared with casting experiments on plate geometries with plate thicknesses...

  4. 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.

  5. High-toughness silk produced by a transgenic silkworm expressing spider (Araneus ventricosus dragline silk protein.

    Directory of Open Access Journals (Sweden)

    Yoshihiko Kuwana

    Full Text Available Spider dragline silk is a natural fiber that has excellent tensile properties; however, it is difficult to produce artificially as a long, strong fiber. Here, the spider (Araneus ventricosus dragline protein gene was cloned and a transgenic silkworm was generated, that expressed the fusion protein of the fibroin heavy chain and spider dragline protein in cocoon silk. The spider silk protein content ranged from 0.37 to 0.61% w/w (1.4-2.4 mol% native silkworm fibroin. Using a good silk-producing strain, C515, as the transgenic silkworm can make the raw silk from its cocoons for the first time. The tensile characteristics (toughness of the raw silk improved by 53% after the introduction of spider dragline silk protein; the improvement depended on the quantity of the expressed spider dragline protein. To demonstrate the commercial feasibility for machine reeling, weaving, and sewing, we used the transgenic spider silk to weave a vest and scarf; this was the first application of spider silk fibers from transgenic silkworms.

  6. Effects of irradiation on crack-arrest toughness of two high-copper welds

    International Nuclear Information System (INIS)

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

    1990-01-01

    The objective of this study is to determine the effect of neutron irradiation on the shift and shape of the lower-bound curve to crack-arrest data. Two submerged-arc welds with copper contents of 0.23 and 0.31 wt % were commercially fabricated in 220-mm-thick plate. Crack-arrest specimens fabricated from these welds were irradiated at a nominal temperature of 288 degree C to an average fluence of 1.9 x 10 19 neutrons/cm 2 (>1 MeV). A preliminary evaluation of the results shows that the neutron-irradiation induced crack-arrest toughness temperature shift is about the same as the Charpy V-notch impact temperature shift at the 41-J energy level. The shape of the lower-bound curves, (for the range of test temperatures covered), compared to those of the ASME K Ia -curve did not seem to have been altered by irradiation. 10 refs., 9 figs., 7 tabs

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

    International Nuclear Information System (INIS)

    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 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 x 10 19 neutrons/cm 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 Jc )

  8. High Ductility and Toughness of a Micro-duplex Medium-Mn Steel in a Large Temperature Range from -196 °C to 200 °C

    DEFF Research Database (Denmark)

    Chen, Si-lian; Hu, Jun; Zhang, Xiaodan

    2015-01-01

    intercritical annealing after forging and hot rolling. Ultrahigh ductility with a total elongation higher than 30% was achieved in the temperature range from - 196 degrees C to 200 degrees C and high impact toughness no less than 200 J at - 40 degrees C was obtained. Based on the analysis of microstructure...

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

    International Nuclear Information System (INIS)

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

    2004-01-01

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

  10. The fracture toughness of eggshell.

    Science.gov (United States)

    Taylor, David; Walsh, Megan; Cullen, Alexandra; O'Reilly, Peter

    2016-06-01

    The shells of avian eggs are very brittle, but how brittle? Fracture toughness, Kc is a standard measure used widely to characterise engineering materials. We devised a novel way to measure Kc and applied it to commercial hens' eggs, obtaining a value of 0.3MPa√m. This value is much lower than previous published values, which we argue are incorrect and misleading. We discuss how this exceptionally low toughness value (in comparison to that of other natural materials made from calcium carbonate) has been achieved by prevention of toughening mechanisms. Eggshell has an unusual combination of mechanical properties (low fracture toughness combined with high Young's modulus), making it ideally suited as a container for the developing chick, which must be stiff and rigid but also brittle enough to be broken when required. Further testing and analysis using the Theory of Critical Distances and Weibull probability theory allowed us to describe the effects of defects of various types: cracks, holes and notches, on the strength of whole eggs. These results are of commercial importance because many eggs break prematurely as a result of microscopic defects. This paper presents the first accurate measurements of the fracture toughness of eggshell. These results are important because eggshell is a brittle material which fails from microscopic defects, so knowledge of the fracture toughness is essential to understand its mechanical performance. The toughness value obtained is discussed in the context of other mechanical properties, of eggshell and other natural materials. This is useful for understanding how eggshell's stiffness and toughness make it ideally suited to its purpose, and the mechanisms by which toughness is achieved. The paper also contains analysis of the effect of defect type, including cracks, notches and holes, to provide a fuller picture of defect tolerance which will be useful in the egg producing industry. Copyright © 2016 Acta Materialia Inc. Published by

  11. 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.

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

    Science.gov (United States)

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

    2013-12-01

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

  13. 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.

  14. Mental toughness latent profiles in endurance athletes.

    Science.gov (United States)

    Zeiger, Joanna S; Zeiger, Robert S

    2018-01-01

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

  15. Mental toughness latent profiles in endurance athletes

    Science.gov (United States)

    Zeiger, Robert S.

    2018-01-01

    Mental toughness in endurance athletes, while an important factor for success, has been scarcely studied. An online survey was used to examine eight mental toughness factors in endurance athletes. The study aim was to determine mental toughness profiles via latent profile analysis in endurance athletes and whether associations exist between the latent profiles and demographics and sports characteristics. Endurance athletes >18 years of age were recruited via social media outlets (n = 1245, 53% female). Mental toughness was measured using the Sports Mental Toughness Questionnaire (SMTQ), Psychological Performance Inventory-Alternative (PPI-A), and self-esteem was measured using the Rosenberg Self-Esteem Scale (RSE). A three-class solution emerged, designated as high mental toughness (High MT), moderate mental toughness (Moderate MT) and low mental toughness (Low MT). ANOVA tests showed significant differences between all three classes on all 8 factors derived from the SMTQ, PPI-A and the RSE. There was an increased odds of being in the High MT class compared to the Low MT class for males (OR = 1.99; 95% CI, 1.39, 2.83; Pathletes who were over 55 compared to those who were 18–34 (OR = 2.52; 95% CI, 1.37, 4.62; Pathletes. High MT is associated with demographics and sports characteristics. Mental toughness screening in athletes may help direct practitioners with mental skills training. PMID:29474398

  16. Enhancement of Impact Toughness by Delamination Fracture in a Low-Alloy High-Strength Steel with Al Alloying

    Science.gov (United States)

    Sun, Junjie; Jiang, Tao; Liu, Hongji; Guo, Shengwu; Liu, Yongning

    2016-12-01

    The effect of delamination toughening of martensitic steel was investigated both at room and low temperatures [253 K and 233 K (-20 °C and -40 °C)]. Two low-alloy martensitic steels with and without Al alloying were both prepared. Layered structure with white band and black matrix was observed in Al alloyed steel, while a homogeneous microstructure was displayed in the steel without Al. Both steels achieved high strength (tensile strength over 1600 MPa) and good ductility (elongation over 11 pct), but they displayed stark contrasts on impact fracture mode and Charpy impact energy. Delamination fracture occurred in Al alloyed steel and the impact energies were significantly increased both at room temperature (from 75 to 138 J, i.e., nearly improved up to 2 times) and low temperatures [from 47.9 to 71.3 J at 233 K (-40 °C)] compared with the one without Al. Alloying with Al promotes the segregation of Cr, Mn, Si and C elements to form a network structure, which is martensite with higher carbon content and higher hardness than that of the matrix. And this network structure evolved into a band structure during the hot rolling process. The difference of yield stress between the band structure and the matrix gives rise to a delamination fracture during the impact test, which increases the toughness greatly.

  17. 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...

  18. An electrochemical investigation of the corrosion behavior of Al-Si-Cu hypereutectic alloys in alcoholic environments

    International Nuclear Information System (INIS)

    Traldi, S. M.; Rossi, J. L.; Costa, I.

    2003-01-01

    Al-Si-Cu hypereutectic alloys produced by spray forming are mostly used in the automotive industry, especially for cylinder liners. they the advantage of low weight associated with low coefficient of thermal expansion and excellent mechanical properties- mainly wear resistance at high temperatures. The corrosion s resistance of these alloys in fuels, particularly alcoholic media, however is not yet known. In this investigation, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation hove been used to evaluate the corrosion resistance of a hyper eutectic Al-Si-Cu alloy in alcoholic environments. the EIS tests carried out in pure ethanol, and ethanol with small additions (1 mM) of acid an chloride to investigate the effect of these contaminants on corrosion resistance. The corrosion resistance of a grey cast iron has also been evaluated in pure ethanol for comparison. The Al-Si-Cu alloy showed high corrosion resistance in pure ethanol, far superior to that of grey cast iron in the same medium. (Author) 13 refs

  19. 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.

  20. Material investigation of strength, deformation and toughness under high rates of loading

    International Nuclear Information System (INIS)

    Meyer, L.W.

    1988-01-01

    This paper reports analyses of inertial and other disturbing effects, in order to determine improvements of the testing methods for materials analysis under high rates of loading. Typical, misleading data in load-time diagrams of strength tests of materials under dynamic loads have been taken as a basis for the study which investigated the yield points, strength and deformation behaviour of four steels (the hot working steel X 45 CrSi 9 3; the low-alloy, high-strength, tempered steel 35 NiCrMo 12 5 as a typical specimen of the tempered steels; a carbon steel 46 Mn 7; and a high-strength austenitic steel X 3 CrNiMoNbN 23 17) in the load range of ε ≅ 10 -4 (quasi static) up to ε = 4x10 3 1/s. (orig./HP) [de

  1. Testing Your Mettle: Tough Problems and Real-World Solutions for Middle and High School Teachers.

    Science.gov (United States)

    Alexandrowicz, Harry J.

    This guide presents a series of scenarios that encapsulate the legal, philosophical, and common sense challenges faced by middle and high school teachers every day. Each scenario includes the vignette, the topical problem areas into which it falls, four possible solutions, space for the readers to state what they would do in each situation, and…

  2. Strong and tough cellulose nanopaper with high specific surface area and porosity.

    Science.gov (United States)

    Sehaqui, Houssine; Zhou, Qi; Ikkala, Olli; Berglund, Lars A

    2011-10-10

    In order to better understand nanostructured fiber networks, effects from high specific surface area of nanofibers are important to explore. For cellulose networks, this has so far only been achieved in nonfibrous regenerated cellulose aerogels. Here, nanofibrillated cellulose (NFC) is used to prepare high surface area nanopaper structures, and the mechanical properties are measured in tensile tests. The water in NFC hydrogels is exchanged to liquid CO2, supercritical CO2, and tert-butanol, followed by evaporation, supercritical drying, and sublimation, respectively. The porosity range is 40-86%. The nanofiber network structure in nanopaper is characterized by FE-SEM and nitrogen adsorption, and specific surface area is determined. High-porosity TEMPO-oxidized NFC nanopaper (56% porosity) prepared by critical point drying has a specific surface area as high as 482 m(2) g(-1). The mechanical properties of this nanopaper structure are better than for many thermoplastics, but at a significantly lower density of only 640 kg m(-3). The modulus is 1.4 GPa, tensile strength 84 MPa, and strain-to-failure 17%. Compared with water-dried nanopaper, the material is softer with substantiallly different deformation behavior.

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

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, L W; Schoenherr, R; Hockauf, M, E-mail: robert.schoenherr@mb.tu-chemnitz.d [Chemnitz University of Technology, Materials and Impact Engineering, D-09107 Chemnitz (Germany)

    2010-07-01

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

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

    Science.gov (United States)

    Meyer, L. W.; Schönherr, R.; Hockauf, M.

    2010-07-01

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

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

    International Nuclear Information System (INIS)

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

    2010-01-01

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

  6. Assessment of circumferential cracks in hypereutectic Al-Si clutch housings

    Directory of Open Access Journals (Sweden)

    M. Haghshenas

    2017-04-01

    Full Text Available As in situ natural composites with silicon phase acting as the reinforcing phase, Al-Si alloys are among most commonly used aluminum alloys in automotive applications (i.e. engine component. Silicon contributes to the strength of Al-Si alloys through load transfer from the Al matrix to the hard (rigid Si phase in the microstructure (load-carrying capacity. Casting parameters (i.e. solidification rate, elemental segregation, secondary dendrite spacing… as well as the size and distribution of the microstructural constituents in Al-Si alloys (i.e. morphology of Si particles, intermetallic compounds, secondary dendrite spacing contribute directly to the mechanical response and failure (or fracture behavior of the alloy within the service. In hyper-eutectic Al-Si alloys (i.e. B390.0, distribution of coarse pre-eutectic Si particle mainly contribute to stress concentration, crack initiation and propagation during the actual service condition. In the present paper, the parameters contribution to the formation of the circumferential cracks in clutch housings made of die cast hyper-eutectics B390.0 Al-Si alloys are assessed through optical microscopy and scanning electron microscopy. Casting variable, cooling rate, their effect on the cracks as well some of the possible causes are also discussed in detail.

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

    International Nuclear Information System (INIS)

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

    1990-01-01

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

  8. Toughness in Integrative Bargaining.

    Science.gov (United States)

    Tutzauer, Frank

    1993-01-01

    Introduces a new measure of bargaining toughness based on dynamical information that can easily be used in integrative bargaining scenarios. Develops a mathematical measure of bargaining toughness that takes into account not only how much the bargainer has conceded but how fast he or she has done so. (RS)

  9. Low expansion superalloy with improved toughness

    Science.gov (United States)

    Smith, Darrell F.; Stein, Larry I.; Hwang, Il S.

    1995-01-01

    A high strength, low coefficient of thermal expansion superalloy exhibiting improved toughness over a broad temperature range down to about 4.degree. K. The composition is adapted for use with wrought superconducting sheathing.

  10. Irradiation effects on fracture toughness of two high-copper submerged-arc welds, HSSI series 5. Volume 2, Appendices E and F

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

  11. Influence of Heat Input on Microstructure and Toughness Properties in Simulated CGHAZ of X80 Steel Manufactured Using High-Temperature Processing

    Science.gov (United States)

    Zhu, Zhixiong; Han, Jian; Li, Huijun

    2015-11-01

    To determine and demonstrate the weldability of high-Nb high-temperature processed (HTP) steels and provide extremely valuable information for future line pipe steel design and general steel manufacture, in the current study the toughness in simulated coarse-grained heat-affected zone (CGHAZ) of an X80 grade steel manufactured using HTP was evaluated. The simulated CGHAZs subjected to thermal cycles with various heat inputs (HIs) (0.8 to 5.0 kJ/mm) were produced using a Gleeble 3500 simulator. The microstructures and corresponding mechanical properties were investigated by means of optical microscopy, scanning electron microscopy, electron backscatter diffraction, hardness testing, and Charpy V-notch (CVN) testing. The microstructural examination shows that the simulated CGHAZs consisted of a bainite-dominant microstructure and relatively low amount (<2 pct) of martensite-austenite (M-A) constituent. The prior austenite grain size was controlled to be 45 to 55 µm at HIs of 0.8 to 3.5 kJ/mm, and remarkably increased to 85 µm at an HI of 5 kJ/mm. The results of CVN testing suggest that superior toughness can be achieved in the studied range of HIs (0.8 to 5 kJ/mm). This is thought to be associated with the combined effects of bainitic microstructure and low M-A fraction as well as comparatively fine austenite grain size in the studied CGHAZs.

  12. Dynamic fracture toughness

    Science.gov (United States)

    Kobayashi, A. S.; Ramulu, M.; Dadkhah, M. S.; Yang, K.-H.; Kang, B. S. J.

    1986-01-01

    Dynamic fracture toughness versus crack velocity relations of Homalite-100, polycarbonate, hardened 4340 steel and reaction bonded silicon nitride are reviewed and discrepancies with published data and their probable causes are discussed. Data scatter in published data are attributed in part to the observed fluctuations in crack velocities. The results reaffirmed our previous conclusion that the dynamic fracture toughness versus crack velocity relation is specimen dependent and that the dynamic arrest stress intensity factor is not a unique material property.

  13. Numerical modelling of solidification of thin walled hypereutectic ductile cast iron

    DEFF Research Database (Denmark)

    Pedersen, Karl Martin; Hattel, Jesper; Tiedje, Niels

    2006-01-01

    Numerical simulation of solidification of ductile cast iron is normally based on a model where graphite nodules are surrounded by an austenite shell. The two phases are then growing as two concentric spheres governed by diffusion of carbon through the austenite shell. Experiments have however shown...... simulation of thin-walled ductile iron castings. Simulations have been performed with a 1-D numerical solidi¬fication model that includes the precipitation of non-eutectic austenite during the eutectic stage. Results from the simulations have been compared with experimental castings with wall thick...... the presence of austenite dendrites even in hypereutectic castings. In thin-walled castings the presence of austenite dendrites is even more pronounced, which increases the risk of shrinkage porosities. This off-eutectic austenite is therefore an important part that should be taken into account during...

  14. Determination of Weibull Analysis of the Hypereutectic Silumins Reliability in Failure Time Respect

    Directory of Open Access Journals (Sweden)

    J. Szymszal

    2009-07-01

    Full Text Available The results of dynamic evaluation of the reliability of hypereutectic AlSi17Cu3NiMg silumin under the effect of symmetrical cyclic tensile-compressive stresses were presented. Studies were carried out on a normal-running fatigue testing machine, which was the mechanically driven resonant pulsator. For the needs of quantitative reliability evaluation and the time-to-failure evaluation, the procedures used in survival analysis, adapted to the analysis of failure-free operation with two- and three-parametric Weibull distributions, were applied. The values of the parameters were estimated using the method of maximum reliability and a rank-based non-parametric method. The results of the evaluation of the reliability and damage intensity are an important element in the determination of casting quality and enable a reliable estimation of the operational suitability time.

  15. Effects of Laser Quenching on Impact Toughness and Fracture Morphologies of 40CrNiMo High Strength Steel

    Science.gov (United States)

    Dejun, Kong; Lei, Zhang

    2014-10-01

    The surface of 40CrNiMo steel was quenched with a CO2 laser, Charpy impact test was conducted at temperatures of 20, 0, and -20 °C, and the impact absorption energies were measured. The fracture morphologies were observed with SEM, and the influence of microhardness, residual stress, and retained austenite on mechanical behavior of impact fracture after laser quenching was discussed. The results show that the hardened layer depth is more than 1 mm after laser quenching, and hardness is about 480-500 HV. The fracture morphology of the sample is dimple rupture at a temperature of 20 °C; with the lower temperature the fracture dimples become smaller. At a temperature of -20 °C, the fracture morphologies change from ductile to brittle, which is mainly cleavage fracture. The increase in surface hardness, production of compressive residual stress, and existence of retained austenite after laser quenching are the main mechanisms of increasing impact toughness.

  16. Impact of Reversed Austenite on the Impact Toughness of the High-Strength Steel of Low Carbon Medium Manganese

    Science.gov (United States)

    Su, Guanqiao; Gao, Xiuhua; Zhang, Dazheng; Du, Linxiu; Hu, Jun; Liu, Zhenguang

    2018-01-01

    We elucidate the relationship between the volume fraction of austenite and the Charpy impact toughness in a medium-Mn steel in terms of microstructural evolution with impact temperature. Different from retained austenite in the matrix after direct quenching, sub-micron lath-shaped morphology-reversed austenite in medium-Mn steel was produced by intercritical annealing. We found that reversed austenite steadily affected the fracture mode; only ductile fractures and dimples decreased with decreasing impact temperature. After the impact fracture test, the content of reversed austenite in the matrix increased slightly with a decreasing impact temperature due to the stability of the austenite grains caused by recrystallization of α' martensite. Reversed austenite slightly decreased during the impact process with a decreasing impact temperature.

  17. Toughness and strength of nanocrystalline graphene

    Science.gov (United States)

    Shekhawat, Ashivni; Ritchie, Robert O.

    2016-01-01

    Pristine monocrystalline graphene is claimed to be the strongest material known with remarkable mechanical and electrical properties. However, graphene made with scalable fabrication techniques is polycrystalline and contains inherent nanoscale line and point defects—grain boundaries and grain-boundary triple junctions—that lead to significant statistical fluctuations in toughness and strength. These fluctuations become particularly pronounced for nanocrystalline graphene where the density of defects is high. Here we use large-scale simulation and continuum modelling to show that the statistical variation in toughness and strength can be understood with ‘weakest-link' statistics. We develop the first statistical theory of toughness in polycrystalline graphene, and elucidate the nanoscale origins of the grain-size dependence of its strength and toughness. Our results should lead to more reliable graphene device design, and provide a framework to interpret experimental results in a broad class of two-dimensional materials. PMID:26817712

  18. 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.

  19. Determination of slip systems and their relation to the high ductility and fracture toughness of the B2 DyCu intermetallic compound

    International Nuclear Information System (INIS)

    Cao, G.H.; Shechtman, D.; Wu, D.M.; Becker, A.T.; Chumbley, L.S.; Lograsso, T.A.; Russell, A.M.; Gschneidner, K.A.

    2007-01-01

    DyCu single crystals with CsCl-type B2 structure were tensile tested at room temperature. Slip trace analysis shows that the primary slip system in DyCu with a tensile axis orientation of is {1 1 0} and the critical resolved shear stress for {1 1 0} slip is 18 MPa. Slip traces were also observed from a secondary slip system, {1 1 0} , and this slip system appears to be a key contributor to the previously reported high ductility and high fracture toughness of polycrystalline DyCu. Transmission electron microscopy determinations of the Burgers vectors of dislocations in tensile tested specimens revealed and dislocations, with -type dislocations being more abundant. The implications of these findings for the understanding of the mechanical properties of DyCu and the large family of ductile rare earth B2 intermetallics are discussed

  20. Fracture Toughness Of Zircaloy Claddings

    International Nuclear Information System (INIS)

    Bertsch, J.; Hoffelner, W

    2003-01-01

    Zirconium-based alloys (Zircaloy) have been used as cladding material in Light Water Reactors for many years. During fabrication, or in in-reactor service, crack-type defects can be formed, posing questions regarding mechanical integrity. As claddings change their mechanical properties (mainly toughness) during service as a result of irradiation-induced degradation, oxidation and hydride formation, it is essential for integrity considerations to provide parameters for the assessment of the influence of flaws on rupture behaviour. Usually, fracture-mechanics parameters are employed such as the fracture toughness, K IC , or, for high plastic strains, the J-integral, JIC. The applicability of these parameters is, however, limited by the dimensions of the samples (e.g. thickness). In claddings with a wall thickness of below 1 mm, determination of toughness necessitates an extension of the J-integral concept. A method based on the traditional J-approach, but applicable to thin-walled structures, is presented in this paper. (author)

  1. 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.

  2. Transforming Anaerobic Adhesives into Highly Durable and Abrasion Resistant Superhydrophobic Organoclay Nanocomposite Films: A New Hybrid Spray Adhesive for Tough Superhydrophobicity

    Science.gov (United States)

    Bayer, Ilker S.; Brown, Andrea; Steele, Adam; Loth, Eric

    2009-12-01

    The authors report fabrication of tough nanostructured self-cleaning superhydrophobic polymer-organoclay films from anaerobic acrylic adhesives displaying strong adhesion to metal surfaces. Both industrial and bio-grade anaerobic adhesives such as bone cements could be used. Montmorillonite clay filled anaerobic adhesives were modified by blending with a water dispersed fluoro-methacrylic latex in solution to form abrasion resistant interpenetrating polymer network films upon spray casting. The adhesive films could cure by thermosetting in oxygen-rich environments. Very high contact angles with low hysteresis were also measured for acidic (pH 2) and basic (pH 11) aqueous buffer solutions indicating resistance to acidic and basic media.

  3. Influence of microstructure on fracture toughness of austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Rao, P.P.; Putatunda, S.K. [Wayne State Univ., Detroit, MI (United States). Dept. of Chemical Engineering and Materials Science

    1997-07-01

    An investigation was carried out to examine the influence of microstructure on the plane strain fracture toughness of austempered ductile iron. Austempered ductile iron (ADI) alloyed with nickel, copper, and molybdenum was austenitized and subsequently austempered over a range of temperatures to produce different microstructures. The microstructures were characterized through optical microscopy and X-ray diffraction. Plane strain fracture toughness of all these materials was determined and was correlated with the microstructure. The results of the present investigation indicate that the lower bainitic microstructure results in higher fracture toughness than upper bainitic microstructure. Both volume fraction of retained austenite and its carbon content influence the fracture toughness. The retained austenite content of 25 vol pct was found to provide the optimum fracture toughness. It was further concluded that the carbon content of the retained austenite should be as high as possible to improve fracture toughness.

  4. 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.

  5. 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

  6. Fracture Toughness of Vocal Fold Tissue: A Preliminary Study.

    Science.gov (United States)

    Miri, Amir K; Chen, Lei Xi; Mongrain, Rosaire; Mongeau, Luc

    2016-05-01

    A customized mechanical tester that slices thin, soft samples was used to measure the fracture toughness of vocal fold tissue. Porcine vocal fold lamina propria was subjected to quasi-static, guillotine-like tests at three equally distanced regions along the anterior-posterior direction. The central one-third where high-velocity collisions between vocal folds occur was found to have the maximum fracture toughness. In contrast, the anterior one-third featured a lower toughness. Fracture toughness can be indicative of the risk of benign and malignant lesions in vocal fold tissue. Copyright © 2016 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

  7. Evaluations of thermal shock resistance and fracture toughness of SiC as a gas turbine blade at high temperatures. Gas turbine yo SiC yokuzai no koon ni okeru tainetsu shogekisei no hyoka

    Energy Technology Data Exchange (ETDEWEB)

    Sato, S.; Kurumada, A.; Kudo, Y.; Chikahata, H.; Shibano, M.; Miyata, H. (Ibaraki Univ., Ibaraki (Japan). Faculty of Engineering Hitachi Ltd., Tokyo (Japan))

    1989-12-20

    This paper shows the results of the experiments on the thermal shock resistance and the thermal shock fracture toughness of ceramic blade used for high quality high temperature gas turbines. Using disk specimens of alpha SiC blade, the thermal shock resistance and the thermal shock fracture toughness are determined by means of Joule {prime} s heating at a central area of disk specimens at 1000 {degree} C (4.3 sec.) and at 1200 {degree} C, 1300 {degree} C, and 1600 {degree} C (4.5 sec.) . Both of the thermal shock resistance and fracture toughness decreases as the temperature increases until 1300 {degree} C, and then increases from 1300 to 1600 {degree} C. Both show maximum values at 1600 {degree} C. The writers consider that this is due to the stress release by the increase of ductility at high temperature. The experiments were also performed for SC-101 which is used for semiconductor base as reference material. The thermal shock resistance and fracture toughness of SC-101 at 1200 {degree} C is three times and 1.4 times larger respectively than SiC. The writers considered that it is caused by the high thermal conductivity three times larger than alpha SiC. 11 refs., 12 figs.

  8. A Neuropsychological Model of Mentally Tough Behavior.

    Science.gov (United States)

    Hardy, Lew; Bell, James; Beattie, Stuart

    2014-02-01

    Four studies were conducted with two primary objectives: (a) to conceptualize and measure mental toughness from a behavioral perspective and (b) to apply relevant personality theory to the examination of between-person differences in mentally tough behavior. Studies 1 (N = 305 participants from a range of different sports) and 2 (N = 110 high-level cricketers) focused on the development of an informant-rated mental toughness questionnaire that assessed individual differences in ability to maintain or enhance performance under pressure from a wide range of stressors. Studies 3 (N = 214) and 4 (N = 196) examined the relationship between reinforcement sensitivities and mentally tough behavior in high-level cricketers. The highest levels of mental toughness reported by coaches occurred when cricketers were sensitive to punishment and insensitive to reward. Study 4 suggested that such players are predisposed to identify threatening stimuli early, which gives them the best possible opportunity to prepare an effective response to the pressurized environments they encounter. The findings show that high-level cricketers who are punishment sensitive, but not reward sensitive, detect threat early and can maintain goal-directed behavior under pressure from a range of different stressors. © 2013 Wiley Periodicals, Inc.

  9. An electrochemical investigation of the corrosion behavior of Al-Si-Cu hypereutectic alloys in alcoholic environments

    Directory of Open Access Journals (Sweden)

    Traldi, S. M.

    2003-12-01

    Full Text Available Al-Si-Cu hypereutetic alloys produced by spray forming are mostly used in the automotive industry, especially for cylinder liners. They have the advantage of low weight associated with low coefficient of thermal expansion and excellent mechanical properties - mainly wear resistance at high temperatures. The corrosion resistance of these alloys in fuels, particularly alcoholic media, however is not yet known. In this investigation, electrochemical impedance spectroscopy (EIS and potentiodynamic polarisation have been used to evaluate the corrosion resistance of a hypereutectic Al-Si-Cu alloy in alcoholic environments. The EIS tests were carried out in pure ethanol, and ethanol with small additions (1 mM of acid and chloride, to investigate the effect of these contaminants on corrosion resistance. The corrosion resistance of a grey cast iron has also been evaluated in pure ethanol for comparison. The Al-Si-Cu alloy showed high corrosion resistance in pure ethanol, far superior to that of grey cast iron in the same medium.

    Aleaciones hipereutécticas producidas por conformación por spray son muy empleadas en la industria automovilística, especialmente en los revestimientos de los cilindros. Tienen la ventaja de añadir menos peso con bajo coeficiente de expansión térmica y excelentes propiedades mecánicas, sobre todo resistencia al desgaste en altas temperaturas. Todavía, la resistencia a la corrosión de estas aleaciones en combustibles no es conocida. En este estudio fueron utilizadas las técnicas de espectroscopia de impedancia electroquímica y polarización potenciodinámica, para evaluar la resistencia a la corrosión de una aleación hipereutéctica Al-Si-Cu en medio alcohólico. Las pruebas fueron conducidas en etanol puro y etanol con pequeñas adiciones (1 mM de ácido y cloruro, con la finalidad de investigar el efecto de estos contaminantes en la resistencia a la corrosión. Hierro fundido gris, también fue

  10. Tough by name, tough by nature.

    Science.gov (United States)

    Baillie, Jonathan

    2015-04-01

    Few beds, one would imagine, could withstand three-quarters of a ton landing on them, but this was the challenge successfully met by a box bed from a furniture manufacturer for challenging behaviour environments, Tough Furniture, when, to reassure a customer that the bed could accommodate 30-stone patients, 13 of the company's staff jumped repeatedly on it to ensure that it would survive intact in a real-world setting. Such testing may seem extreme, but is vital, since much of the company's furniture is destined for environments where patients will abuse, and indeed attempt to destroy, components. As MD David Vesty explained to HEJ editor, Jonathan Baillie, when he visited the company's Shropshire headquarters, it is through manufacturing premium quality cabinet furniture that is both attractive and distinctly non-institutional, but will equally withstand the harshest use, that the company has ensured that its products can live up to the brand name.

  11. Investigations of linear contraction and shrinkage stresses development in hypereutectic al-si binary alloys

    Directory of Open Access Journals (Sweden)

    J. Mutwil

    2009-07-01

    Full Text Available Shrinkage phenomena during solidification and cooling of hypereutectic aluminium-silicon alloys (AlSi18, AlSi21 have been examined. A vertical shrinkage rod casting with circular cross-section (constant or fixed: tapered has been used as a test sample. Two type of experiments have been conducted: 1 on development of the test sample linear dimension changes (linear expansion/contraction, 2 on development of shrinkage stresses in the test sample. By the linear contraction experiments the linear dimension changes of the test sample and the metal test mould as well a temperature in six points of the test sample have been registered. By shrinkage stresses examination a shrinkage tension force and linear dimension changes of the test sample as well a temperature in three points of the test sample have been registered. Registered time dependences of the test bar and the test mould linear dimension changes have shown, that so-called pre-shrinkage extension has been mainly by mould thermal extension caused. The investigation results have shown that both: the linear contraction as well as the shrinkage stresses development are evident dependent on metal temperature in a warmest region the sample (thermal centre.

  12. Corrosion performance of Al-Si-Cu hypereutectic alloys in a synthetic condensed automotive solution

    Directory of Open Access Journals (Sweden)

    Hamilta de Oliveira Santos

    2005-06-01

    Full Text Available In this investigation the corrosion resistance of four Al-Si hypereutectic alloys in a solution typical of condensate from automotive fuel combustion products, and referred to here as synthetic condensed automotive solution, has been studied. Three commercial alloys that are used for cylinder liners, and a laboratory made alloy, were studied by electrochemical impedance spectroscopy and measurements were taken after increasing times of immersion in this solution. Comparison of the electrochemical response of the four alloys in the corrosive solution was carried out. Although the mechanisms by which the four alloys corroded were similar, the results indicated differences in corrosion resistances of these alloys, and these differences could be related to their microstructures. The laboratory prepared alloy showed increased susceptibility to pitting corrosion compared to the commercial alloys. The surfaces of the alloys were examined, before and after the corrosion test, by scanning electron microscopy and analyzed by energy dispersive spectroscopy. The results indicated preferential attack of the aluminium matrix phase in all the alloys. The alloy with higher copper content and prepared by spray forming was more susceptible to pitting compared to the other alloys. The EIS response at low frequencies indicated a diffusion-controlled process, probably that of oxygen to the alloy interface.

  13. 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)

  14. 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.

  15. A new high-strength iron base austenitic alloy with good toughness and corrosion resistance (GE-EPRI alloy-TTL)

    International Nuclear Information System (INIS)

    Ganesh, S.

    1989-01-01

    A new high strength, iron based, austenitic alloy has been successfully developed by GE-EPRI to satisfy the strength and corrosion resistance requirements of large retaining rings for high capacity generators (>840Mw). This new alloy is a modified version of the EPRI alloy-T developed by the University of California, Berkeley, in an earlier EPRI program. It is age hardenable and has the nominal composition (weight %): 34.5 Ni, 5Cr, 3Ti, 1Nb, 1Ta, 1Mo, .5Al, .3V, .01B. This composition was selected based on detailed metallurgical and processing studies on modified versions of alloy-T. These studies helped establish the optimum processing conditions for the new alloy and enabled the successful scale-up production of three large (50-52 inch dia) test rings from a 5,000 lb VIM-VAR billet. The rings were metallurgically sound and exhibited yield strength capabilities in the range 145 to 220 ksi depending on the extent of hot/cold work induced. The test rings met or exceeded all the property goals. The above alloy can provide a good combination of strength, toughness and corrosion resistance and, through an suitable modification of chemistry or processing conditions, could be a viable candidate for high strength LWR internal applications. 3 figs

  16. Modification and aging precipitation behavior of hypereutectic Al-21wt.%Si alloy treated by P+Ce combination

    Directory of Open Access Journals (Sweden)

    Liu Pei

    2014-11-01

    Full Text Available In the present study, the tested hypereutectic Al-21wt.%Si alloys were prepared by modifying the melt using different proportions of P and Ce, and then applying T6 heat treatment. The modification effects and mechanism of P+Ce complex modifier on the Si phase of hypereutectic Al-21wt.%Si alloy were studied, and the aging precipitation behavior after modification was characterized by means of tensile strength measurement, OM, SEM and TEM analysis. The results show that the massive primary silicon phase particles are significantly refined after modification, while the needle-like eutectic silicon crystals become fibrous and short. It was found that the mechanism of phosphorus modification on the primary silicon can be attributed to heterogeneous nucleation of AlP, while the modification mechanism of Ce can be explained by adsorbing-twinning theory. In the aged microstructure of the modified hypereutectic Al-21wt.%Si alloy, there existed some strengthening phases such as Al4Cu9, Al2Cu, AlCu3, and Al57Mn12. The P+Ce complex modifier not only affected the size of primary silicon and eutectic silicon, but also the aging behavior of alloys under the heat treatment process. When Al-21wt.%Si alloy was modified using 0.08%wt.P + 0.6wt.% Ce, the aging precipitates were dispersed uniformly in the alloy, and its mechanical properties at room and elevated temperatures are optimized (Rm = 287.6 MPa at RT, Rm = 210 MPa at 300 ℃.

  17. Impact toughness and fracture toughness of austempered ductile iron

    Directory of Open Access Journals (Sweden)

    Jingcheng LIU

    2004-11-01

    Full Text Available The impact toughness and fracture toughness ofaustermpered ductile iron (ADI are described. The notched and un-notched charpy impact toughness of ADI at room temperature are somewhat lower than that of steel castings or forged steel pieces, however, they are approximately three times higher than that of mormal pearlitic ductile iron. The impact toughness of ADI decreases with decreasing temperature; but at -40 ℃ it still maintains about 70% of the value at room temperature. The properties of fracture toughness are important in safety design and failure analysis. In this study all fracture toughness data of ADI are higher than that of conventional ductile iron, and are equivalent to or better than that of steel castings o forged steel pieces with the tensile strength equivalent to ADI.

  18. Preliminary science report on the directional solidification of hypereutectic cast iron during KC-135 low-G maneuvers

    Science.gov (United States)

    Curreri, P. A.; Stefanescu, D. M.; Hendrix, J. C.

    1983-01-01

    An ADSS-P directional solidification furnace was reconfigured for operation on the KC-135 low-g aircraft. The system offers many advantages over quench ingot methods for study of the effects of sedimentation and convection on alloy formation. The directional sodification furnace system was first flown during the September 1982 series of flights. The microstructure of the hypereutectic cast iron sample solidified on one of these flights suggests a low-g effect on graphite morphology. Further experiments are needed to ascertain that this effect is due to low-gravity and to deduce which of the possible mechanisms is responsible for it.

  19. Fracture toughness of manet II steel

    International Nuclear Information System (INIS)

    Gboneim, M.M.; Munz, D.

    1997-01-01

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

  20. Comparison of fracture toughness values of normal and high strength concrete determined by three point bend and modified disk-shaped compact tension specimens

    Directory of Open Access Journals (Sweden)

    S. Seitl

    2017-10-01

    Full Text Available The modified disk shaped compact tension test is a configuration derived from standard compact tension test that is used for measuring fracture mechanical properties of primarily metallic materials. The compact tension configuration is commonly used for measurement fracture mechanical properties as e.g. fracture toughness, Young�s modulus, work of fracture etc. The modified compact tension tests imply significant modifications of the specimen morphology in order to avoid premature failure. The modified compact tension test is not proper for quasi-brittle materials due to its complicated shape (steel-concrete interface, but it is easily extracted from drill core and we do not need large amount of material for obtaining fracture properties as we need for e.g. three- or four- point bend test. Since it is a new test method, a wide range of tests is needed to be done before it can be applied. In the paper the selected outputs of the experiments performed on normal and high strength concrete will be processed and the values of fracture mechanical parameters will be discussed

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

    Science.gov (United States)

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

    2018-04-01

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

  2. 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

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

    International Nuclear Information System (INIS)

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

    2008-01-01

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

  4. Effect of Withdrawal Rate and Gd on the Microstructures of Directionally Solidified NiAl-Cr(Mo) Hypereutectic Alloy

    Science.gov (United States)

    Wang, Lei; Shen, Jun; Zhang, Yun-Peng; Guo, Lan-Lan

    2016-03-01

    The microstructures of Ni-31Al-32Cr-6Mo- xGd hypereutectic alloy were investigated at the withdrawal rates of 10 μm/s, 30 μm/s, and 90 μm/s. For the Gd-free hypereutectic alloy, the Cr(Mo) primary dendrites appear at the beginning of solidification when the withdrawal rate is 10 μm/s. As the solidification proceeds, the Cr(Mo) primary dendrite is eliminated, and the fully eutectic structure can be obtained in the steady-state zone. With increasing the withdrawal rate, the Cr(Mo) primary dendrites decrease gradually, and vanish at 90 μm/s. In addition, at a moderate withdrawal rate (30 μm/s), an optimum addition of Gd content (0.1 wt.%) results in the refinement of the microstructure, including the refinement of the eutectic cells and the intercellular region. Meanwhile, the new white phase ((Al x Gd1- x )2O3) appears in the boundary of the eutectic cells when the Gd content is not less than 0.1 wt.%.

  5. Characterising the fracture toughness of polymers at moderately high rates of loading with the use of instrumented tensile impact testing

    NARCIS (Netherlands)

    Visser, Roy; Caimmi, F.; Pavan, A.

    2013-01-01

    The more common use of instrumentation in impact testing opened up the possibility to apply fracture mechanics testing methods to polymers at moderately high impact rates. Tensile impact testing offers some advantages over the more common three-point bending and compact tension geometries. Most

  6. 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.

  7. Veins Improve Fracture Toughness of Insect Wings

    Science.gov (United States)

    Dirks, Jan-Henning; Taylor, David

    2012-01-01

    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. PMID:22927966

  8. Fracture toughness of stainless steel welds

    International Nuclear Information System (INIS)

    Mills, W.J.

    1985-11-01

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

  9. Relationship between mental toughness and physical endurance.

    Science.gov (United States)

    Crust, Lee; Clough, Peter J

    2005-02-01

    This study tested the criterion validity of the inventory, Mental Toughness 48, by assessing the correlation between mental toughness and physical endurance for 41 male undergraduate sports students. A significant correlation of .34 was found between scores for overall mental toughness and the time a relative weight could be held suspended. Results support the criterion-related validity of the Mental Toughness 48.

  10. Comparison of fracture toughness values of normal and high strength concrete determined by three point bend and modified disk-shaped compact tension specimens

    Czech Academy of Sciences Publication Activity Database

    Seitl, Stanislav; Ríjos, J. D.; Cifuentes, H.

    2017-01-01

    Roč. 11, č. 42 (2017), s. 56-65 ISSN 1971-8993 R&D Projects: GA ČR(CZ) GA16-18702S; GA MŠk LM2015069 Institutional support: RVO:68081723 Keywords : Concrete * Stress intensity factors * T-stress * Compact tension test * Fracture behavior * Fracture toughness Subject RIV: JL - Materials Fatigue, Friction Mechanics OBOR OECD: Audio engineering, reliability analysis

  11. 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

  12. HAZ toughness of multipass welded joints: influence of brittle zones

    Energy Technology Data Exchange (ETDEWEB)

    Loureiro, A. [Dept. de Engenharia Mecanica, Polo II, Pinhal de Marrocos, Coimbra (Portugal)

    2002-07-01

    The aim of this work is to study the influence of the weld metal properties on the heat-affected zone toughness of welds in high strength steel. Welds were produced with the same heat input, by submerged arc welding, using three couples flux-wire with increasing content of chromium and nickel. The increase of alloying elements induces the decrease of primary ferrite formation and the increase of toughness in the weld metal. All the HAZs show similar CTOD toughness in the same range of temperatures, which is compatible with the same type of structures obtained in the HAZ. The scatter obtained in CTOD test results does not allow the establishment of a reliable correlation between HAZ toughness and the proportion of the several zones sampled by the COD crack tip. (orig.)

  13. Fracture toughness determination in steam generator tubes

    International Nuclear Information System (INIS)

    Bergant M; Yawny, A; Perez Ipina, J

    2012-01-01

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

  14. 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

  15. 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

  16. Revealing the extra-high ductility and toughness of micro+duplex medium+Mn steel in a large temperature range from 200 ℃ to -196 ℃

    DEFF Research Database (Denmark)

    Cao, Wenquan; Hu, Jun; Dong, Han

    2014-01-01

    A medium-Mn steel (0.2C5Mn) was processed by intercritical annealing at different temperature (625℃ and 650℃) after forging and hot rolling. The microstructures were characterized by transmission electron microscopy and the mechanical properties were measured by tensile tests and impact tests...... be obtained in the temperature range from 200℃ to -196℃. And significantly delayed transition from ductile to brittle and no less than 200J impact toughness at -40℃ could be obtained in the ART-annealed medium-Mn steel. Based on the analysis of microstructure and mechanical properties, the enhanced ductility...

  17. 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.

  18. Anomalous scaling law of strength and toughness of cellulose nanopaper.

    Science.gov (United States)

    Zhu, Hongli; Zhu, Shuze; Jia, Zheng; Parvinian, Sepideh; Li, Yuanyuan; Vaaland, Oeyvind; Hu, Liangbing; Li, Teng

    2015-07-21

    The quest for both strength and toughness is perpetual in advanced material design; unfortunately, these two mechanical properties are generally mutually exclusive. So far there exists only limited success of attaining both strength and toughness, which often needs material-specific, complicated, or expensive synthesis processes and thus can hardly be applicable to other materials. A general mechanism to address the conflict between strength and toughness still remains elusive. Here we report a first-of-its-kind study of the dependence of strength and toughness of cellulose nanopaper on the size of the constituent cellulose fibers. Surprisingly, we find that both the strength and toughness of cellulose nanopaper increase simultaneously (40 and 130 times, respectively) as the size of the constituent cellulose fibers decreases (from a mean diameter of 27 μm to 11 nm), revealing an anomalous but highly desirable scaling law of the mechanical properties of cellulose nanopaper: the smaller, the stronger and the tougher. Further fundamental mechanistic studies reveal that reduced intrinsic defect size and facile (re)formation of strong hydrogen bonding among cellulose molecular chains is the underlying key to this new scaling law of mechanical properties. These mechanistic findings are generally applicable to other material building blocks, and therefore open up abundant opportunities to use the fundamental bottom-up strategy to design a new class of functional materials that are both strong and tough.

  19. Fracture toughness of irradiated beryllium

    International Nuclear Information System (INIS)

    Beeston, J.M.

    1978-01-01

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

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

    International Nuclear Information System (INIS)

    Haggag, F.M.

    1985-01-01

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

  1. 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.

  2. Advanced characterization techniques in understanding the roles of nickel in enhancing strength and toughness of submerged arc welding high strength low alloy steel multiple pass welds in the as-welded condition

    Science.gov (United States)

    Sham, Kin-Ling

    Striving for higher strength along with higher toughness is a constant goal in material properties. Even though nickel is known as an effective alloying element in improving the resistance of a steel to impact fracture, it is not fully understood how nickel enhances toughness. It was the goal of this work to assist and further the understanding of how nickel enhanced toughness and maintained strength in particular for high strength low alloy (HSLA) steel submerged arc welding multiple pass welds in the as-welded condition. Using advanced analytical techniques such as electron backscatter diffraction, x-ray diffraction, electron microprobe, differential scanning calorimetry, and thermodynamic modeling software, the effect of nickel was studied with nickel varying from one to five wt. pct. in increments of one wt. pct. in a specific HSLA steel submerged arc welding multiple pass weldment. The test matrix of five different nickel compositions in the as-welded and stress-relieved condition was to meet the targeted mechanical properties with a yield strength greater than or equal to 85 ksi, a ultimate tensile strength greater than or equal to 105 ksi, and a nil ductility temperature less than or equal to -140 degrees F. Mechanical testing demonstrated that nickel content of three wt. pct and greater in the as-welded condition fulfilled the targeted mechanical properties. Therefore, one, three, and five wt. pct. nickel in the as-welded condition was further studied to determine the effect of nickel on primary solidification mode, nickel solute segregation, dendrite thickness, phase transformation temperatures, effective ferrite grain size, dislocation density and strain, grain misorientation distribution, and precipitates. From one to five wt. pct nickel content in the as-welded condition, the primary solidification was shown to change from primary delta-ferrite to primary austenite. The nickel partitioning coefficient increased and dendrite/cellular thickness was

  3. 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.

  4. Applying the Theory of Planned Behavior to Physical Activity: The Moderating Role of Mental Toughness.

    Science.gov (United States)

    Hannan, Thomas E; Moffitt, Robyn L; Neumann, David L; Thomas, Patrick R

    2015-10-01

    This study explored whether mental toughness, the capacity to maintain performance under pressure, moderated the relation between physical activity intentions and subsequent behavior. Participants (N = 117) completed the Mental Toughness Index and a theory of planned behavior questionnaire. Seven days later, physical activity was assessed using the International Physical Activity Questionnaire. Attitudes, subjective norms, and perceived behavioral control explained substantial variance (63.1%) in physical activity intentions. Intentions also significantly predicted physical activity behavior. The simple slopes analyses for the moderation effect revealed a nonsignificant intention-behavior relation at low levels of mental toughness. However, intentions were significantly and positively related to physical activity when mental toughness was moderate or high, suggesting that the development of a mentally tough mindset may reduce the gap between behavior and physical activity intention. Future research is needed to confirm these findings and apply them in the design of mental toughness interventions to facilitate physical activity engagement.

  5. Mental Toughness in the Classical Martial Arts

    OpenAIRE

    Minnix, Douglas Wayne

    2010-01-01

    Mental Toughness in the Classical Martial Arts Douglas Wayne Minnix ABSTRACT The construct of mental toughness is in a state of evolution and refinement. The current study proposed to investigate; (1) the importance of mental toughness attributes from a Classical Martial Arts context, (2) the trainability of the mental toughness attributes from a Classical Martial Arts context, (3) and the extent to which classical martial artists perceive that attributes converge under broader...

  6. 46 CFR 154.605 - Toughness test.

    Science.gov (United States)

    2010-10-01

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

  7. 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.

  8. 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.

  9. Toughness and hamiltonicity in k-trees

    NARCIS (Netherlands)

    Broersma, Haitze J.; Xiong, L.; Yoshimoto, K.

    2007-01-01

    We consider toughness conditions that guarantee the existence of a hamiltonian cycle in $k$-trees, a subclass of the class of chordal graphs. By a result of Chen et al. 18-tough chordal graphs are hamiltonian, and by a result of Bauer et al. there exist nontraceable chordal graphs with toughness

  10. Toughness and hamiltonicity in $k$-trees

    NARCIS (Netherlands)

    Broersma, H.J.; Xiong, L.; Yoshimoto, K.

    2001-01-01

    We consider toughness conditions that guarantee the existence of a hamiltonian cycle in $k$-trees, a subclass of the class of chordal graphs. By a result of Chen et al.\\ 18-tough chordal graphs are hamiltonian, and by a result of Bauer et al.\\ there exist nontraceable chordal graphs with toughness

  11. Toughness in graphs - A survey

    NARCIS (Netherlands)

    Bauer, Douglas; Broersma, Haitze J.; Schmeichel, Edward

    In this survey we have attempted to bring together most of the results and papers that deal with toughness related to cycle structure. We begin with a brief introduction and a section on terminology and notation, and then try to organize the work into a few self explanatory categories. These

  12. Hard-yet-tough high-vanadium high-speed steel composite coating in-situ alloyed on ductile iron by atmospheric plasma arc

    NARCIS (Netherlands)

    Cao, Huatang; Dong, Xuanpu; Pei, Yutao T.

    2018-01-01

    A graded high-vanadium alloy composite coating was synthesized from premixed powders (V, Cr, Ti, Mo, Nb) on ductile iron (DI) substrate via atmospheric plasma arc surface alloying process. The resulted cross-section microstructure is divided into three distinct zones: upper alloyed zone (AZ) rich

  13. A viscoplastic model with application to LiF-22 percent CaF2 hypereutectic salt

    Science.gov (United States)

    Freed, A. D.; Walker, K. P.

    1990-01-01

    A viscoplastic model for class M (metal-like behavior) materials is presented. One novel feature is its use of internal variables to change the stress exponent of creep (where n is approximately = 5) to that of natural creep (where n = 3), in accordance with experimental observations. Another feature is the introduction of a coupling in the evolution equations of the kinematic and isotropic internal variables, making thermal recovery of the kinematic variable implicit. These features enable the viscoplastic model to reduce to that of steady-state creep in closed form. In addition, the hardening parameters associated with the two internal state variables (one scalar-valued, the other tensor-valued) are considered to be functions of state, instead of being taken as constant-valued. This feature enables each internal variable to represent a much wider spectrum of internal states for the material. The model is applied to a LiF-22 percent CaF2 hypereutectic salt, which is being considered as a thermal energy storage material for space-based solar dynamic power systems.

  14. Study on Microstructure and Mechanical Properties of Hypereutectic Al-18Si Alloy Modified with Al-3B.

    Science.gov (United States)

    Gong, Chunjie; Tu, Hao; Wu, Changjun; Wang, Jianhua; Su, Xuping

    2018-03-20

    An hypereutectic Al-18Si alloy was modified via an Al-3B master alloy. The effect of the added Al-3B and the modification temperature on the microstructure, tensile fracture morphologies, and mechanical properties of the alloy were investigated using an optical microscope, Image-Pro Plus 6.0, a scanning electron microscope, and a universal testing machine. The results show that the size of the primary Si and its fraction decreased at first, and then increased as an additional amount of Al-3B was added. When the added Al-3B reached 0.2 wt %, the fraction of the primary Si in the Al-18Si alloy decreased with an increase in temperature. Compared with the unmodified Al-18Si alloy, the tensile strength and elongation of the alloy modified at 850 °C with 0.2 wt % Al-3B increased by 25% and 81%, respectively. The tensile fracture of the modified Al-18Si alloy exhibited partial ductile fracture characteristics, but there were more areas with ductile characteristics compared with that of the unmodified Al-18Si alloy.

  15. The role of the bimodal distribution of ultra-fine silicon phase and nano-scale V-phase (AlSi2Sc2) on spark plasma sintered hypereutectic Al–Si–Sc alloys

    International Nuclear Information System (INIS)

    Raghukiran, Nadimpalli; Kumar, Ravi

    2016-01-01

    Hypereutectic Al–Si and Al–Si–Sc alloys were spark plasma sintered from corresponding gas-atomized powders. The microstructures of the Al–Si and Al–Si–Sc alloys possessed remarkably refined silicon particles in the size range of 0.38–3.5 µm and 0.35–1.16 µm respectively in contrast to the silicon particles of size greater than 100 µm typically found in conventionally cast alloys. All the sintered alloys exhibited significant ductility of as high as 85% compressive strain without failure even with the presence of relatively higher weight fraction of the brittle silicon phase. Moreover, the Al–Si–Sc alloys have shown appreciable improvement in the compressive strength over their binary counterparts due to the presence of intermetallic compound AlSi 2 Sc 2 of size 10–20 nm distributed uniformly in the matrix of those alloys. The dry sliding pin-on-disc wear tests showed improvement in the wear performance of the sintered alloys with increase in silicon content in the alloys. Further, the Al–Si–Sc ternary alloys with relatively lesser silicon content exhibited appreciable improvement in the wear resistance over their binary counterparts. The Al–Si–Sc alloys with bimodal distribution of the strengthening phases consisting of ultra-fine (sub-micron size) silicon particles and the nano-scale AlSi 2 Sc 2 improved the strength and wear properties of the alloys while retaining significant amount of ductility.

  16. Ultrasonic ranking of toughness of tungsten carbide

    Science.gov (United States)

    Vary, A.; Hull, D. R.

    1983-01-01

    The feasibility of using ultrasonic attenuation measurements to rank tungsten carbide alloys according to their fracture toughness was demonstrated. Six samples of cobalt-cemented tungsten carbide (WC-Co) were examined. These varied in cobalt content from approximately 2 to 16 weight percent. The toughness generally increased with increasing cobalt content. Toughness was first determined by the Palmqvist and short rod fracture toughness tests. Subsequently, ultrasonic attenuation measurements were correlated with both these mechanical test methods. It is shown that there is a strong increase in ultrasonic attenuation corresponding to increased toughness of the WC-Co alloys. A correlation between attenuation and toughness exists for a wide range of ultrasonic frequencies. However, the best correlation for the WC-Co alloys occurs when the attenuation coefficient measured in the vicinity of 100 megahertz is compared with toughness as determined by the Palmqvist technique.

  17. Observations in Fracture Toughness Testing of Glasses and Optical Ceramics

    Science.gov (United States)

    Salem, Jon

    2017-01-01

    Fracture toughness is a critical structural design parameter and an excellent metrics to rank materials. Itdetermines fracture strength by way of the flaws, both inherent and induced, and defines the endpoint of the slow crackgrowth curve. The fracture toughness of structural and optical ceramics, and glasses as measured by several techniques is compared. When good metrology is employed, the results are very comparable with two exceptions: materials exhibiting crack growth resistance and those with a low SCG exponents. For materials with R-curves, the result is a function of extension and can be minimized with short cracks. For materials with low SCG exponents, such as glasses, elimination of the corrosive media andor increasing the stress intensity rate minimizes effects. A summary of values is given, and it appears that highly modified glasses exhibit lower fracture toughness and slow crack growth exponent than high purity glasses such as fused silica.

  18. Effect of Y2O3-Al2O3 ratio on inter-granular phases and films in tape-casting α-SiC with high toughness

    International Nuclear Information System (INIS)

    Huang Rong; Gu Hui; Zhang Jingxian; Jiang Dongliang

    2005-01-01

    Silicon carbide (SiC) ceramics prepared from liquid phase sintering after aqueous-tape-casting can yield high toughness when appropriate amount of Y 2 O 3 -Al 2 O 3 are added, even though no elongated grains are present. Grain boundaries (GB), second-phases and hetero-phase boundaries (HB) in 2 samples with additive mole ratios of 3:5 and 3:7 are investigated using high-resolution and analytical electron microscopy (HREM and AEM). The meta-stable YAlO 3 (YAP) was nucleated from SiC surfaces in the sample with Y/Al = 3:5 as revealed by crystallographic relations across the HB, whilst relatively thick amorphous films were found at GB. In contrary, the higher level of Al 2 O 3 additives decreases the GB film thickness in the sample with Y/Al = 3:7, and the homogeneous nucleation of Y 3 Al 5 O 12 (YAG) occurs at triple pockets accompanying with thick HB films. The strong variation of GB widths is a result of GB wetting in the sample with Y/Al = 3:5 and HB wetting in the sample of Y/Al = 3:7, both by liquid Al 2 O 3 . The energy of GB in the former sample is higher than the energy of HB as exhibited by the preferential nucleation of meta-stable YAP on SiC surfaces, which results in wetting of GB by the liquid; the situation is opposite in the latter sample as the wetting of HB occurs, leading to de-wetting of GB. The thermal mismatch between SiC and YAP or YAG as well as the presence of amorphous films facilitate the creation of micro-crack to promote inter-granular fracture and result in high toughness in both SiC ceramics

  19. Test-Free Fracture Toughness

    Science.gov (United States)

    Minnetyan, Levon; Chamis, Christos C. (Technical Monitor)

    2003-01-01

    Computational simulation results can give the prediction of damage growth and progression and fracture toughness of composite structures. The experimental data from literature provide environmental effects on the fracture behavior of metallic or fiber composite structures. However, the traditional experimental methods to analyze the influence of the imposed conditions are expensive and time consuming. This research used the CODSTRAN code to model the temperature effects, scaling effects and the loading effects of fiber/braided composite specimens with and without fiber-optic sensors on the damage initiation and energy release rates. The load-displacement relationship and fracture toughness assessment approach is compared with the test results from literature and it is verified that the computational simulation, with the use of established material modeling and finite element modules, adequately tracks the changes of fracture toughness and subsequent fracture propagation for any fiber/braided composite structure due to the change of fiber orientations, presence of large diameter optical fibers, and any loading conditions.

  20. Fracture Behavior of Silica- and Rubber-Nanoparticle-Toughed Epoxies

    Science.gov (United States)

    Labak, Amelia K.

    Particle-toughened crosslinked epoxies are popular materials for a variety of applications, including the microelectronics industry. For this application, the properties of these materials, such as a high fracture toughness and a low coefficient of thermal expansion, are highly appealing. In order to achieve these properties, inorganic particles are often added into the matrix. For this study, both inorganic and organic particles-toughened epoxies are investigated in the hopes of finding an optimized system. In particular, in this study, micron-sized silica and nano-sized rubbery block copolymers are added to an amine-cured epoxy matrix. A series of rubber-only and silica-only systems are investigated for their contribution to the fracture toughness. Then, a series of hybrid systems are investigated. The hypothesis is that the rubber will contribute toughness through rubber particle cavitation and matrix void growth and the silica will contribute toughness through crack pinning and bridging and particle debonding. In the hybrid systems, these mechanisms will take place at a different scale. Therefore, the nanoscale mechanisms of the rubber will be able to function at the same time as the micron sized mechanisms of the silica and the resultant toughness will be synergistically higher. The results from this study show an interesting contribution from the rubber particles both in the rubber-only systems and the hybrid system. Ultimately, there was a marked increase in the fracture toughness of the hybrid systems, although not synergistic. This increase indicates that it would be possible to create an optimized hybrid system from the combined addition of these particles.

  1. 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

  2. Beyond optimal performance: mental toughness profiles and developmental success in adolescent cricketers.

    Science.gov (United States)

    Gucciardi, Daniel F; Jones, Martin Ian

    2012-02-01

    The purposes of the current study were to identify mental toughness profiles in adolescent cricketers and examine differences between these profiles on developmental assets and negative emotional states. A sample of 226 community cricketers (125 New Zealanders and 101 Australians; male n = 210) aged between 10 and 18 years (M(age) = 14.41 years; SD = 2.11) completed a multisection, online survey containing measures of mental toughness, developmental assets, and negative emotional states. The results of hierarchical (Ward's method) and nonhierarchical (k means) cluster analyses revealed three mental toughness profiles characterized by low, moderate, and high levels of all five mental toughness assets (i.e., affective intelligence, desire to achieve, self-belief, attentional control, resilience). Those cricketers with high levels of mental toughness reported possession of more developmental assets and lower levels of negative emotional states when compared with cricketers with the moderate levels of mental toughness. No statistically significant differences existed between the moderate and low levels of mental toughness profiles. These findings provided preliminary evidence to suggest that mental toughness might be viewed not only from the traditional view of optimal performance but also from a stance that may represent a contextually salient representation of thriving in youth sport settings.

  3. EOS7Cm: An improved TOUGH2 module for simulating non-isothermal multiphase and multicomponent flow in CO2-H2S-CH4-brine systems with high pressure, temperature and salinity

    Science.gov (United States)

    Lei, Hongwu; Li, Jun; Li, Xiaochun; Jiang, Zhenjiao

    2016-09-01

    Understanding the non-isothermal multiphase and multicomponent flow in a CO2-H2S-CH4-brine system is of critical importance in projects such as CO2 storage in deep saline aquifers, natural gas extraction using CO2 as the displacement fluid, and heat extraction from hot dry rocks using CO2 as the working fluid. Numerical simulation is a necessary tool to evaluate the chemical evolution in these systems. However, an accurate thermodynamic model for CO2-H2S-CH4-brine systems appropriate for high pressure, temperature, and salinity is still lacking. This study establishes the mutual solubility model for CO2-H2S-CH4-brine systems based on the fugacity-activity method for phase equilibrium. The model can predict mutual solubilities for pressure up to 1000 bar for CO2 and CH4, and 200 bar for H2S, for temperature up to 200 °C, and for salinity up to 6 mol/kg water. We incorporated the new model into TOUGH2/EOS7C, forming a new improved module we call EOS7Cm. Compared to the original EOS7C, EOS7Cm considers the effects of H2S and covers a larger range of temperature and salinity. EOS7Cm is employed in five examples, including CO2 injection with and without impurities (CH4 and/or H2S) into deep aquifers, CH4 extraction from aquifers by CO2 injection, and heat extraction from hot dry rock. The results are compared to those from TOUGH2/ECO2N, EOS7C and CMG, agreement among which serves to verify EOS7Cm.

  4. 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

  5. Various results on the toughness of graphs

    NARCIS (Netherlands)

    Broersma, Haitze J.; Engbers, E.A.; Trommel, H.

    1997-01-01

    Let G be a graph, and let t 0 be a real number. Then G is t-tough if t!(G − S) jSj for all S V (G) with !(G − S) > 1, where !(G − S) denotes the number of components of G − S. The toughness of G, denoted by (G), is the maximum value of t for which G is t-tough (taking (Kn) = 1 for all n 1). G is

  6. 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.

  7. 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.

  8. Proceedings of the TOUGH workshop

    International Nuclear Information System (INIS)

    Pruess, K.

    1990-09-01

    A workshop on applications and enhancements of the TOUGH/MULKOM family of multiphase fluid and heat flow simulation programs was held at Lawrence Berkeley Laboratory on September 13--14, 1990. The workshop was attended by 62 scientists from seven countries with interests in geothermal reservoir engineering, nuclear waste isolation, unsaturated zone hydrology, environmental problems, and laboratory and field experimentation. The meeting featured 21 technical presentations, extended abstracts of which are reproduced in the present volume in unedited form. Simulator applications included processes on a broad range of space scales, from centimeters to kilometers, with transient times from seconds to geologic time scales. A number of code enhancements were reported that increased execution speeds for large 3-D problems by factors of order 20, reduced memory requirements, and improved user-friendliness. The workshop closed with an open discussion session that focussed on future needs and means for interaction in the TOUGH user community. Input from participants was gathered by means of a questionnaire that is reproduced in the appendix. 171 refs., 91 figs., 16 tabs

  9. 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.

  10. Toughness and Triangle-Free Graphs

    NARCIS (Netherlands)

    Bauer, D.; van den Heuvel, J.; Schmeichel, E.

    1995-01-01

    In this paper, we prove that there exist triangle-free graphs with arbitrarily large toughness, thereby settling a longstanding open question. We also explore the problem of whether there exists a t-tough, n/(t + 1)-regular, triangle-free graph on n vertices for various values of t, and provide a

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

    African Journals Online (AJOL)

    Kathryn van Boom

    The results of the current study indicate that mindfulness is significantly and positively correlated with not only global mental toughness, but also with confidence, constancy and control. This suggests that as mindfulness increases among provincial female hockey players, so does their general level of mental toughness.

  12. Double-network gels and the toughness of terrestrial slug glue.

    Science.gov (United States)

    Wilks, Alex M; Rabice, Sarah R; Garbacz, Holland S; Harro, Cailin C; Smith, Andrew M

    2015-10-01

    The terrestrial slug Arion subfuscus produces a defensive secretion that is sticky and tough, despite being a dilute gel. It is unusual in having high stiffness for a gel, yet retaining the high extensibility typical of mucus. In tensile tests, it sustains an average peak stress of 101 kPa, and fails at an average strain of 9.5. This gives the gel toughness; it requires much greater strain energy to fracture than most gels. This toughness may arise from a double-network type mechanism. In this mechanism, two separate, interpenetrating networks of polymers with different properties combine to give toughness that can be several orders of magnitude greater than either network individually. Native gel electrophoresis suggests that A. subfuscus glue consists of two networks: a network of negatively charged proteins ranging in Mr from 40×10(3) to 220×10(3) that can be dissociated by hydroxylamine and a network of heparan sulfate-like proteoglycans. The two networks are not tightly linked, though proteins of Mr 40×10(3) and 165×10(3) may associate with the carbohydrates. Targeted disruption of either network separately, using enzymatic hydrolysis, disulfide bond breakage or imine bond disruption completely disrupted the glue, resulting in no measurable toughness. Thus, the two networks separately provide little toughness, but together they work synergistically to create a tough material, as predicted in the double-network mechanism. © 2015. Published by The Company of Biologists Ltd.

  13. 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.

  14. 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.

  15. In vitro fracture toughness of commercial Y-TZP ceramics: a systematic review.

    Science.gov (United States)

    Passos, Sheila Pestana; Nychka, John A; Major, Paul; Linke, Bernie; Flores-Mir, Carlos

    2015-01-01

    The aim of this review was to assess research methods used to determine the fracture toughness of Y-TZP ceramics in order to systematically evaluate the accuracy of each method with regard to potential influencing factors. Six databases were searched for studies up to April 2013. The terms "tough*," "critical stress intensity factor," "zirconi*," "yttri*," "dent*," "zirconia," "zirconium," and "stress" were searched. Titles and abstracts were screened, and literature that fulfilled the inclusion criteria was selected for a full-text reading. Test conditions with potential influence on fracture toughness were extracted from each study. Ten laboratory studies met the inclusion criteria. There was a significant variation in relation to test method, ambient conditions, applied/indentation load, number of specimens, and geometry and dimension of the specimen. The results were incomparable due to high variability and missing information. Therefore, 10 parameters were listed to be followed to standardize future studies. A wide variation in research methods affected the fracture toughness reported for Y-TZP ceramics among the selected studies; single-edge-precracked beam and chevron-notched-beam seem to be the most recommended methods to determine Y-TZP fracture toughness; the indentation methods have several limitations. The accurate calculation of toughness values is fundamental because overestimating toughness data in a clinical situation can negatively affect the lifetime of the restoration. © 2014 by the American College of Prosthodontists.

  16. Slip knots and unfastening topologies enhance toughness without reducing strength of silk fibroin fibres.

    Science.gov (United States)

    Berardo, Alice; Pantano, Maria F; Pugno, Nicola M

    2016-02-06

    The combination of high strength and high toughness is a desirable feature that structural materials should display. However, while in the past, engineers had to compromise on either strength or toughness depending on the requested application, nowadays, new toughening strategies are available to provide strong materials with high toughness. In this paper, we focus on one of such strategy, which requires no chemical treatment, but the implementation of slip knots with optimized shape and size in the involved material, which is silkworm silk in this case. In particular, a variety of slip knot topologies with different unfastening mechanisms are investigated, including even complex knots usually used in the textile industry, and their efficiency in enhancing toughness of silk fibres is discussed.

  17. TOUGH Short Course for Scientists and Engineers

    International Nuclear Information System (INIS)

    Kowalsky, Michael B.; Finsterle, Stefan

    2006-01-01

    The TOUGH family of codes is a suite of computer programs for the simulation of multiphase fluid and heat flows in porous and fractured media with applications to geothermal reservoir engineering, nuclear waste disposal in geologic formations, geologic carbon sequestration, gas hydrate research, vadose zone hydrology, environmental remediation, oil and gas reservoir engineering, and other mass transport and energy transfer problems in complex geologic settings. TOUGH has been developed in the Earth Sciences Division of the Lawrence Berkeley National Laboratory (LBNL). Many modifications and enhancements have been made to TOUGH (at LBNL and elsewhere) from the time it was first released in 1987. TOUGH and its various descendants (such as iTOUGH2, T2VOC, TMVOC, EWASG, TOUGHREACT, TOUGH+ and many more) are currently in use in approximately 300 research laboratories, private companies, and universities in 33 countries. The LBNL group, headed by Karsten Pruess, serves as custodian of the code. The TOUGH simulators were developed for problems involving strongly heat-driven flow. To describe these phenomena a multi-phase approach to fluid and heat flow is used, which fully accounts for the movement of gaseous and liquid phases, their transport of latent and sensible heat, and phase transitions between liquid and vapor. TOUGH takes account of fluid flow in both liquid and gaseous phases--and, in certain modules, a non-aqueous phase liquid (NAPL)--occurring under pressure, viscous, and gravity forces according to Darcy's law. Interference between the phases is represented by means of relative permeability functions. The code includes Klinkenberg effects and binary diffusion in the gas phase, and capillary and phase adsorption effects for the liquid phase. Heat transport occurs by means of conduction (with thermal conductivity dependent on water saturation), convection, and binary diffusion, which includes both sensible and latent heat. The goal of this training course is to

  18. 46 CFR 54.05-16 - Production toughness testing.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Production toughness testing. 54.05-16 Section 54.05-16... Toughness Tests § 54.05-16 Production toughness testing. (a) For vessels of welded construction, production... steels, weld production toughness tests may be limited to weld metal only if this is all that is required...

  19. 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 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PRESSURE VESSELS Toughness Tests § 54.05-6 Toughness test temperatures. Each toughness test must be conducted at temperatures...

  20. 10 CFR Appendix G to Part 50 - Fracture Toughness Requirements

    Science.gov (United States)

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Fracture Toughness Requirements G Appendix G to Part 50..., App. G Appendix G to Part 50—Fracture Toughness Requirements I. Introduction and scope. II. Definitions. III. Fracture toughness tests. IV. Fracture toughness requirements. I. Introduction and Scope...

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

    International Nuclear Information System (INIS)

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

    2002-01-01

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

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

    Science.gov (United States)

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

    2002-12-01

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

  3. 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

  4. 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...

  5. 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

  6. Fracture toughness of reactor grade graphites, 3

    International Nuclear Information System (INIS)

    Sato, Sennosuke; Awaji, Hideo; Akuzawa, Hironobu; Kon, Junichi.

    1979-01-01

    In our recent papers, we presented a new technique for determining the thermal shock fracture toughness, using a disk specimen with an edge crack. The thermal shock fracture toughness is defined as K sub( ic)k/Eα(K sub( ic) standing for fracture toughness; k for thermal conductivity; E for Young's modulus; α for thermal expansion coefficient) and it can be determined en bloc by measuring the threshold electric power of the arc discharge heating produced when an edge crack propagates in the disk. The value obtained is the fracture toughness corresponding to the thermal shock resistance defined as σk/Eα (σ standing for tensile strength). The experimental data shown in the following discussion concern themselves with four kinds of reactor grade graphite and some varieties of electrode graphite. (author)

  7. 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.

  8. Comparing two measures of mental toughness

    OpenAIRE

    Crust, Lee; Swann, Christian

    2011-01-01

    This paper tested relations between two measures of mental toughness. A sample of 110 male athletes (M age = 20.81 years; SD = 2.76), derived from University sports teams and local sports clubs, gave informed consent before completing two questionnaires to assess mental toughness. It was hypothesized that scales and subscales from the two different instruments, which purported to measure the same or substantially overlapping scales, would be strongly correlated. Predictions concerning the ...

  9. Fracture toughness evaluation of circumferentially-cracked round bars

    International Nuclear Information System (INIS)

    Scibetta, M.

    1996-05-01

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

  10. Fabrication of transparent, tough, and conductive shape-memory polyurethane films by incorporating a small amount of high-quality graphene.

    Science.gov (United States)

    Jung, Yong Chae; Kim, Jin Hee; Hayashi, Takuya; Kim, Yoong Ahm; Endo, Morinobu; Terrones, Mauricio; Dresselhaus, Mildred S

    2012-04-23

    We report a mechanically strong, electrically and thermally conductive, and optically transparent shape-memory polyurethane composite which was fabricated by introducing a small amount (0.1 wt%) of high-quality graphene as a filler. Geometrically large (≈4.6 μm(2)), but highly crystallized few-layer graphenes, verified by Raman spectroscopy and transmission electron microscopy, were prepared by the sonication of expandable graphite in an organic solvent. Oxygen- containing functional groups at the edge plane of graphene were crucial for an effective stress transfer from the graphene to polyurethane. Homogeneously dispersed few-layered graphene enabled polyurethane to have a high shape recovery force of 1.8 MPa cm(-3). Graphene, which is intrinsically stretchable up to 10%, will enable high-performance composites to be fabricated at relatively low cost and we thus envisage that such composites may replace carbon nanotubes for various applications in the near future. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Thermodynamic Alloy Design of High Strength and Toughness in 300 mm Thick Pressure Vessel Wall of 1.25Cr-0.5Mo Steel

    Directory of Open Access Journals (Sweden)

    Hye-sung Na

    2018-01-01

    Full Text Available In the 21st century, there is an increasing need for high-capacity, high-efficiency, and environmentally friendly power generation systems. The environmentally friendly integrated gasification combined-cycle (IGCC technology has received particular attention. IGCC pressure vessels require a high-temperature strength and creep strength exceeding those of existing pressure vessels because the operating temperature of the reactor is increased for improved capacity and efficiency. Therefore, high-pressure vessels with thicker walls than those in existing pressure vessels (≤200 mm must be designed. The primary focus of this research is the development of an IGCC pressure vessel with a fully bainitic structure in the middle portion of the 300 mm thick Cr-Mo steel walls. For this purpose, the effects of the alloy content and cooling rates on the ferrite precipitation and phase transformation behaviors were investigated using JMatPro modeling and thermodynamic calculation; the results were then optimized. Candidate alloys from the simulated results were tested experimentally.

  12. Injectable, Tough Alginate Cryogels as Cancer Vaccines.

    Science.gov (United States)

    Shih, Ting-Yu; Blacklow, Serena O; Li, Aileen W; Freedman, Benjamin R; Bencherif, Sidi; Koshy, Sandeep T; Darnell, Max C; Mooney, David J

    2018-02-14

    A covalently crosslinked methacrylated (MA)-alginate cryogel vaccine has been previously shown to generate a potent response against murine melanoma, but is not mechanically robust and requires a large 16G needle for delivery. Here, covalent and ionic crosslinking of cryogels are combined with the hypothesis that this will result in a tough MA-alginate cryogel with improved injectability. All tough cryogels can be injected through a smaller, 18G needle without sustaining any damage, while covalently crosslinked-only cryogels break after injection. Cytosine-phosphodiester-guanine (CpG)-delivering tough cryogels effectively activate dendritic cells (DCs). Granulocyte macrophage colony-stimulating factor releasing tough cryogels recruit four times more DCs than blank gels by day 7 in vivo. The tough cryogel vaccine induces strong antigen-specific cytotoxic T-lymphocyte and humoral responses. These vaccines prevent tumor formation in 80% of mice inoculated with HER2/neu-overexpressing DD breast cancer cells. The MA-alginate tough cryogels provide a promising minimally invasive delivery platform for cancer vaccinations. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Adhesion toughness of multilayer graphene films.

    Science.gov (United States)

    Wood, Joseph D; Harvey, Christopher M; Wang, Simon

    2017-12-05

    Interface adhesion toughness between multilayer graphene films and substrates is a major concern for their integration into functional devices. Results from the circular blister test, however, display seemingly anomalous behaviour as adhesion toughness depends on number of graphene layers. Here we show that interlayer shearing and sliding near the blister crack tip, caused by the transition from membrane stretching to combined bending, stretching and through-thickness shearing, decreases fracture mode mixity G II /G I , leading to lower adhesion toughness. For silicon oxide substrate and pressure loading, mode mixity decreases from 232% for monolayer films to 130% for multilayer films, causing the adhesion toughness G c to decrease from 0.424 J m -2 to 0.365 J m -2 . The mode I and II adhesion toughnesses are found to be G Ic  = 0.230 J m -2 and G IIc  = 0.666 J m -2 , respectively. With point loading, mode mixity decreases from 741% for monolayer films to 262% for multilayer films, while the adhesion toughness G c decreases from 0.543 J m -2 to 0.438 J m -2 .

  14. Fracture toughness of hydrogels: measurement and interpretation.

    Science.gov (United States)

    Long, Rong; Hui, Chung-Yuen

    2016-10-04

    The fracture mechanics of hydrogels, especially those with significantly enhanced toughness, has attracted extensive research interests. In this article we discuss the experimental measurement and theoretical interpretation of the fracture toughness for soft hydrogels. We first review the definition of fracture toughness for elastic materials, and the commonly used experimental configurations to measure it. In reality most gels are inelastic. For gels that are rate insensitive, we discuss how to interpret the fracture toughness associated with two distinct scenarios: crack initiation and steady-state crack propagation. A formulation to estimate energy dissipation during steady-state crack propagation is developed, and connections to previous models in the literature are made. For gels with rate-dependent behaviors, we review the physical mechanisms responsible for the rate-dependence, and outline the difficulties to rigorously define the fracture toughness for both crack initiation and propagation. We conclude by discussing a few fundamental questions on the fracture of tough gels that are yet to be answered.

  15. Microstructure and mechanical properties of hypereutectic Al-Fe alloys prepared by semi-solid formation

    Directory of Open Access Journals (Sweden)

    Liu Bo

    2011-11-01

    Full Text Available The effects of alloying elements, electromagnetic stirring, reheating and semi-solid formation on the microstructure and mechanical properties of Al-Fe alloys prepared by semi-solid formation were studied. It was found that alloying elements and electromagnetic stirring can alter the morphology and growth mode of the iron-rich phase in Al-Fe alloys; and effectively refine the primary Al3Fe phase. In contrast to the microstructure obtained in conventional casting, the Al3Fe phase becomes thin short rod-like instead of thick needle-like; and the dendritic grain structure almost disappears in the semi-solid formation. The Al3Fe phase can be further refined through being dissolved or fused during subsequent reheating. It was also found that the larger extrusion ratio of semi-solid formation causes a greater crushing effect and therefore the Al3Fe phase is more refined and has more uniform distribution. Moreover, Al-Fe alloys prepared by semi-solid formation exhibit excellent mechanical properties at both room and high temperatures.

  16. 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.

  17. 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.

  18. 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

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

    Science.gov (United States)

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

    2018-01-01

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

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

    Science.gov (United States)

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

    2011-03-01

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

  1. 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; Huijgen, Barbara

    2017-01-01

    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 mental toughness, more specifically on the (in)stability of their psychological state during a match.

  2. 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.

  3. Fracture toughness measurements on zirconia toughened ceramics

    International Nuclear Information System (INIS)

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

    1986-12-01

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

  4. Experiences of older people with dementia participating in a high-intensity functional exercise program in nursing homes: "While it's tough, it's useful".

    Directory of Open Access Journals (Sweden)

    Nina Lindelöf

    Full Text Available The objective of the study was to describe the views and experiences of participation in a high-intensity functional exercise (HIFE program among older people with dementia in nursing homes. The study design was a qualitative interview study with 21 participants (15 women, aged 74-96, and with a Mini-Mental State Examination score of 10-23 at study start. The HIFE-program comprises exercises performed in functional weight-bearing positions and including movements used in everyday tasks. The exercise was individually designed, supervised in small groups in the nursing homes and performed during four months. Interviews were performed directly after exercise sessions and field notes about the sessions were recorded. Qualitative content analysis was used for analyses. The analysis revealed four themes: Exercise is challenging but achievable; Exercise gives pleasure and strength; Exercise evokes body memories; and Togetherness gives comfort, joy, and encouragement. The intense and tailored exercise, adapted to each participant, was perceived as challenging but achievable, and gave pleasure and improvements in mental and bodily strength. Memories of previous physical activities aroused and participants rediscovered bodily capabilities. Importance of individualized and supervised exercise in small groups was emphasized and created feelings of encouragement, safety, and coherence. The findings from the interviews reinforces the positive meaning of intense exercise to older people with moderate to severe dementia in nursing homes. The participants were able to safely adhere to and understand the necessity of the exercise. Providers of exercise should consider the aspects valued by participants, e.g. supervision, individualization, small groups, encouragement, and that exercise involved joy and rediscovery of body competencies.

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

    International Nuclear Information System (INIS)

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

    2003-01-01

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

  6. 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.

  7. 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

  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. Strength and fracture toughness of zirconia dental ceramics.

    Science.gov (United States)

    Turon-Vinas, Miquel; Anglada, Marc

    2018-03-01

    The aim of the paper is to determine and discuss the correlation between the fracture toughness and the fracture stress in zirconia transforming ceramics with a small artificial crack. As an R-curve behaviour is usually present in transforming ceramics for both small and long cracks, predictions of the fracture stress can only be done with an accurate knowledge of the R-curve and crack dimensions. First, basic concepts of fracture mechanics, strength and testing of ceramic materials are introduced. This is followed by a very brief introduction to zirconia dental ceramics and to strength degradation by hydrothermal ageing of 3Y-TZP. Fracture toughness of 3Y-TZP and 12Ce-TZP are then determined for a short (∼50μm) sharp edge crack produced by ultra short pulsed laser ablation on prismatic bending bars in four point bending. The crack size is small but large enough for controlling fracture and for applying elastic fracture mechanics. In both materials the determined fracture toughness is similar, in spite of their difference R-curves. The results of fracture toughness and fracture stress are analysed by using a simple function to represent the R-curve, but which contains the main ingredients of experimental R-curves extracted from the literature either for short or long cracks in 12Ce-TZP. It is concluded that the high R-curves reported in the literature for long and short cracks in 12Ce-TZP and 3Y-TZP might have only a marginal influence on the fracture resistance with cracks of the size studied. This effect is of more significance in 12Ce-TZP. The use of an ideal and simple model of R-curve is presented as a useful guide to predict whether the fracture stress will be enhanced by an existent R-curve. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  10. Solidification structure and abrasion resistance of high chromium white irons

    Science.gov (United States)

    Doğan, Ö. N.; Hawk, J. A.; Laird, G.

    1997-06-01

    Superior abrasive wear resistance, combined with relatively low production costs, makes high Cr white cast irons (WCIs) particularly attractive for applications in the grinding, milling, and pumping apparatus used to process hard materials. Hypoeutectic, eutectic, and hypereutectic cast iron compositions, containing either 15 or 26 wt pct chromium, were studied with respect to the macrostructural transitions of the castings, solidification paths, and resulting microstructures when poured with varying superheats. Completely equiaxed macrostructures were produced in thick section castings with slightly hypereutectic compositions. High-stress abrasive wear tests were then performed on the various alloys to examine the influence of both macrostructure and microstructure on wear resistance. Results indicated that the alloys with a primarily austenitic matrix had a higher abrasion resistance than similar alloys with a pearlitic/bainitic matrix. Improvement in abrasion resistance was partially attributed to the ability of the austenite to transform to martensite at the wear surface during the abrasion process.

  11. Evaluation of WWER-1000 vessel materials fracture toughness

    International Nuclear Information System (INIS)

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

    2007-01-01

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

  12. Development of the mental, emotional, and bodily toughness inventory in collegiate athletes and nonathletes.

    Science.gov (United States)

    Mack, Mick G; Ragan, Brian G

    2008-01-01

    The assessment of an individual's mental toughness would assist clinicians in enhancing an individual's performance, improving compliance with the rehabilitation program, and improving the individual treatment program. However, no sound measure of mental toughness exists. To develop a new measure of mental toughness, the Mental, Emotional, and Bodily Toughness Inventory (MeBTough). Participants were invited to complete a 45-item questionnaire. University research laboratory. A total of 261 undergraduate students were recruited to complete the questionnaire. The Rasch-calibrated item difficulties, fit statistics, and persons' mental toughness ability estimates were examined for model-data fit of the MeBTough. Forty-three of the 45 items had good model-data fit with acceptable fit statistics. Results indicated that the distribution of items was fittingly targeted to the people and the collapsed rating scale functioned well. The item separation index (6.31) and separation reliability statistic (.98) provided evidence that the items had good variability with a high degree of confidence in replicating placement of the items from another sample. Results provided support for using the new measure of mental, emotional, and bodily toughness.

  13. Mental Toughness in South African Youth.

    Science.gov (United States)

    Cowden, Richard G; Clough, Peter J; Oppong Asante, Kwaku

    2017-04-01

    Young people are particularly vulnerable to health risk behaviors and interpersonal violence, stimulating scholars' attention towards identifying factors that may reduce the likelihood that these actions will occur. Associated with positive outcomes in a variety of domains, mental toughness in young people might protect them from engaging in potentially deleterious interpersonal or health-risk behaviors, while potentially promoting positive psychological behaviors. Within this framework, the present study investigated the relationships between mental toughness, attitudes towards physical and psychological risk-taking, and trait forgiveness in a sample of 123 (males = 54, females = 69) South African youth ( M age = 23.97 years, SD = 4.46). Univariate and multivariate analyses indicated higher levels of mental toughness were associated with being more forgiving, ([Formula: see text] = .036), perceiving physical risk-taking more positively ([Formula: see text] = .062), but having more negative attitudes towards psychological risk-taking ([Formula: see text] = .036). These findings give credence to mental toughness as a psychological characteristic involved in youth risk-taking perceptions and interpersonal functioning. Future research might explore the integration of mental toughness into the development of future youth risk behavior interventions.

  14. Rapid Thermal Processing to Enhance Steel Toughness.

    Science.gov (United States)

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

    2018-01-11

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

  15. Software qualification of selected TOUGH2 modules

    International Nuclear Information System (INIS)

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

    1996-10-01

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

  16. 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...

  17. Fracture toughness of heat-pressed and layered ceramics.

    Science.gov (United States)

    Ansong, Richard; Flinn, Brian; Chung, Kwok-Hung; Mancl, Lloyd; Ishibe, Motoaki; Raigrodski, Ariel J

    2013-04-01

    Veneering ceramic materials designed to be used with high noble alloy and zirconia-based restorations have been reported to be susceptible to chipping in vivo. The purpose of this study was to evaluate and compare the fracture toughness of heat-pressed and layered ceramics intended for zirconia and high-noble alloy substrates. Bar specimens were fabricated from 8 different ceramics (Ivoclar-Vivadent [I] and Noritake [N]) intended for pressing (P) and layering (L) to high noble alloy (M) and zirconia (Z) substrates, following the ISO 6872 protocol. The single edge notch beam test method was used to create a notch in the center of each specimen, which was then tested with a universal testing machine (n=6, cross-head speed=0.5 mm/min) and the fracture force values recorded. These values were used to calculate the fracture toughness (K1c) for each specimen. Fracture surfaces were examined with a scanning electron microscope, and the basic components of the tested ceramics were determined by using energy dispersive x-ray (EDX) spectroscopy. Data were analyzed with 3-way ANOVA, followed by multiple comparisons using the Holm method (α=.05). The mean (SD) of the calculated fracture toughness values obtained ranged from 1.20 (0.04) MPa·m(1/2) (group NZL) to 1.74 (0.04) MPa·m(1/2) (group IZL). Fracture toughness was significantly higher in group IZL (1.74) than group IZP (1.41), but lower in group NZL (1.20) than group NZP (1.36) (Pceramics used with a metal substrate showed a crystalline structure mixed with a glassy phase pattern on the fracture surface. The results of EDX analysis on the fracture surfaces indicated that the tested ceramics were composed of Si, Al, K, Na, Mg, and oxygen elements. Ceramics used for veneering zirconia substrate may have various fracture toughness values that relate primarily to the processing technique. Copyright © 2013 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

  18. 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).

  19. TOUGH2 User's Guide Version 2

    International Nuclear Information System (INIS)

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

    1999-01-01

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

  20. 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.

  1. Separations and Their Contribution into the Impact Toughness of Steels of Strength Class K65 (X80)

    Science.gov (United States)

    Farber, V. M.; Khotinov, V. A.; Morozova, A. N.; Martin, T.

    2015-11-01

    The contribution of separations into the impact toughness of steels of strength class X80 is studied. Tests for impact bending are preformed in the range from +20 to -90°C, and analysis of fracture surfaces of Charpy specimens is performed. It is shown that the length L h of the high-energy zone of homogeneous ductile fracture is directly correlated with the level of the impact toughness KCV. The evolution of the form and number of separations upon lowering of the test temperature is considered. The conditions of attainment of a high level of impact toughness ( KCV - 60 ≥ 250 J/cm2) are determined.

  2. Mental toughness and burnout in junior athletes: A longitudinal investigation

    OpenAIRE

    Madigan, Daniel J.; Nicholls, Adam R.

    2017-01-01

    Objectives: Mental toughness correlated negatively with burnout in several cross-sectional studies. It is unclear, however, whether mental toughness predicts changes in athlete burnout over time.\\ud Design: Two-wave longitudinal design.\\ud Method: We examined mental toughness and burnout in 93 junior athletes (mean age 17.7 years) across a three-month period of active training.\\ud Results: Regression analyses revealed that mental toughness predicted residual decreases in total burnout, reduce...

  3. Comparative Study of Sport Mental Toughness between Soccer Officials

    Science.gov (United States)

    Miçoogullari, Bülent Okan; Gümüsdag, Hayrettin; Ödek, Ugur; Beyaz, Özkan

    2017-01-01

    Gucciardi et al. (2009) suggest that mental toughness is more a function of environment than domains, and as such, mental toughness is potentially important in any environment that requires performance setting, challenges, and adversities. Due to vital importance of mental toughness in sports and particularly in soccer, this paper focused on the…

  4. On toughness and hamiltonicity of 2K2-free graphs

    NARCIS (Netherlands)

    Broersma, Haitze J.; Patel, Viresh; Pyatkin, Artem

    The toughness of a (noncomplete) graph G is the minimum value of t for which there is a vertex cut A whose removal yields |A|/t components. Determining toughness is an NP-hard problem for general input graphs. The toughness conjecture of Chvátal, which states that there exists a constant t such that

  5. Effects of Withdrawal Rate and Temperature Gradient on the Microstructure Evolution in Directionally Solidified NiAl-36Cr-6Mo Hypereutectic Alloy

    Science.gov (United States)

    Shang, Zhao; Shen, Jun; Zhang, Jian-Fei; Wang, Lei; Qin, Ling; Fu, Heng-Zhi

    2014-09-01

    The effects of withdrawal rate and temperature gradient on the microstructure and growth interface morphology in directionally solidified Ni-29Al-36Cr-6Mo(at.%) hypereutectic alloy were investigated. Under the temperature gradient of 250 K/cm, well-aligned eutectic microstructure with lamellar morphology was obtained at the withdrawal rate of 6 μm/s. When the withdrawal rate was 10 μm/s, the microstructure changed to Cr(Mo) dendrites + eutectic lamellae. With the increasing withdrawal rate, the interdendritic eutectic growth interface changed from planar to cellular, the number of primary Cr(Mo) dendrites became greater, and the microstructure was refined. When the temperature gradient increased to 600 K/cm, the coupled eutectic growth zone of NiAl-Cr(Mo) alloy was expanded; a well-aligned eutectic microstructure could be obtained at higher rate of 10 μm/s. Furthermore, the planar/cellular transition rate of the interdendritic eutectic growth interface increased. Even at the same withdrawal rate, the number of primary Cr(Mo) dendrites was less and the microstructure was finer under the temperature gradient of 600 K/cm.

  6. Fracture toughness of austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Srinivasan, M.N. [Texas A and M Univ., College Station, TX (United States). Dept. of Mechanical Engineering; Komatsu, S. [Kinki Univ., Higashihiroshima (Japan). Dept. of Mechanical Systems Engineering

    1995-12-01

    The effect of austenitizing temperature, austempering temperature and austempering time on the fracture toughness of austempered ductile iron have been presented and discussed in this paper. Statistical design of experiments with a 2{sup 3} matrix was used to determine the effect of the individual variables and their interactions. The desirable combination of the three variables is suggested based on the analysis.

  7. 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.

  8. The importance of fracture toughness in ultrafine and nanocrystalline bulk materials.

    Science.gov (United States)

    Pippan, R; Hohenwarter, A

    2016-07-02

    The suitability of high-strength ultrafine and nanocrystalline materials processed by severe plastic deformation methods and aimed to be used for structural applications will strongly depend on their resistance against crack growth. In this contribution some general available findings on the damage tolerance of this material class will be summarized. Particularly, the occurrence of a pronounced fracture anisotropy will be in the center of discussion. In addition, the great potential of this generated anisotropy to obtain high-strength materials with exceptionally high fracture toughness in specific loading and crack growth directions will be enlightened. IMPACT STATEMENT Severely plastically deformed materials are reviewed in light of their damage tolerance. The frequently observed toughness anisotropy allows unprecedented fracture toughness - strength combinations.

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

    Science.gov (United States)

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

    2008-06-01

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

  10. Statistical analysis of the behavior of fracture toughness of compound bioceramic artificial bone.

    Science.gov (United States)

    Xu, Shilian; Xu, Renping; Li, Ruoqi

    2011-12-01

    We show the manufacturing procedure of the test specimen of the compound bioceramic artificial bone, conduct experiments to measure its fracture toughness, and conclude that the experiment data conform to the two-parameter Weibull distribution with scale parameter β = 0.527369 and form parameter α = 5.24317. Furthermore, compound bioceramic artificial bone is of a high level of crack sensitivity and its data for the fracture toughness is has a high dispersion. We also analyze the evolution of the confidence level of the reliability of its fracture toughness. With the increase of the confidence level γ, the crack sensitivity increases, but the median, the discreteness, and the confidence intervals decrease. The size of the test specimen influences the experiment for the fracture toughness, the measured values and their dispersion, and there exists the conversion between size of the test specimen and that of the real device. We extend the results to introduce the statistic model of the size effect of the fracture toughness. © 2011, Copyright the Authors. Artificial Organs © 2011, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

  11. Mental toughness as a moderator of the intention-behaviour gap in the rehabilitation of knee pain.

    Science.gov (United States)

    Gucciardi, Daniel F

    2016-06-01

    The purpose of this study was to investigate the role of mental toughness in maximising the effect of intentions to perform rehabilitative exercises on behaviour among a sample of people with knee pain. Cross-sectional survey, with a 2-week time-lagged assessment of exercise behaviour. In total, 193 individuals (nfemale=107, nmale=84) aged between 18 and 69 years (M=30.79, SD=9.39) participated, with 136 (70.5%) retained at both assessment points. At time 1, participants completed an online, multisection survey that encompassed measures of demographic details, severity of problems associated with the knee (e.g., pain, symptoms), past behaviour, mental toughness, and the theory of planned behaviour constructs (TPB; attitudes, subjective norms, perceived behavioural, intentions). Two weeks later, participants retrospectively reported their exercise behaviour for the past 14 days using an online survey. Moderated regression analyses indicated that mental toughness and its interaction with intention accounted for an additional 3% and 4% of the variance in exercise behaviour, respectively. Past behaviour, attitudes, and mental toughness all had direct effects on behaviour, alongside a meaningful interaction between intentions and mental toughness. Specifically, intentions had a stronger effect on exercise behaviour among those individuals high in mental toughness compared to those low in this personal resource. The results of this study shed new light on the intention-behaviour gap by indicating that mental toughness increases the likelihood that intention is translated into action. Copyright © 2015 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  12. Effects of Zr, Ti, and Al Additions on Nonmetallic Inclusions and Impact Toughness of Cast Low-Alloy Steel

    Science.gov (United States)

    Bizyukov, Pavel V.; Giese, Scott R.

    2017-04-01

    A microalloying of the low-carbon and low-alloy cast steel was conducted with Zr, Ti, and Al that were added to the steel in four combinations. After heat treatment, the samples were tested for impact toughness at room temperature using the Charpy method. The highest values of impact toughness were obtained in the group treated with Zr, while Zr-Ti and Zr-Ti-Al groups showed moderate toughness values; the lowest values were observed in the Zr-Al group. Difference among the treatment groups was observed in the fracture mechanisms, morphology, and area distribution of the inclusions. High toughness values achieved in the trials treated with zirconium corresponded with smooth ductile fracture. The metal treated with a combination of zirconium and titanium had a relatively small area occupied by inclusions, but its toughness was also moderate. Lowest impact toughness values corresponded with the larger area occupied by the inclusions in the trials treated with aluminum. Also, a connection between the solubility product [Al][N] and impact toughness was established. The study also provides a qualitative description and quantitative analysis of the nonmetallic inclusions formation as a result of microalloying treatment. The precipitation sequence of the inclusions was described based on the thermochemical calculations for the nonmetallic compounds discovered in the experimental steel. A description of the size distribution, morphology, and composition was conducted for the oxides, nitrides, sulfides, and multiphase particles.

  13. 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

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

    Science.gov (United States)

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

    2015-10-27

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

  15. TOUGH, Unsaturated Groundwater Transport and Heat Transport Simulation

    International Nuclear Information System (INIS)

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

    1992-01-01

    1 - Description of program or function: A successor to the TOUGH program, TOUGH2 offers added capabilities and user features, including the flexibility to handle different fluid mixtures (water, water with tracer; water, CO 2 ; water, air; water, air with vapour pressure lowering, and water, hydrogen), facilities for processing of geometric data (computational grids), and an internal version control system to ensure referenceability of code applications. TOUGH (Transport of Unsaturated Groundwater and Heat) is a multi-dimensional numerical model for simulating the coupled transport of water, vapor, air, and heat in porous and fractured media. The program provides options for specifying injection or withdrawal of heat and fluids. Although primarily designed for studies of high-level nuclear waste isolation in partially saturated geological media, it should also be useful for a wider range of problems in heat and moisture transfer, and in the drying of porous materials. For example, geothermal reservoir simulation problems can be handled simply by setting the air mass function equal to zero on input. The TOUGH simulator was developed for problems involving strongly heat-driven flow. To describe these phenomena a multi-phase approach to fluid and heat flow is used, which fully accounts for the movement of gaseous and liquid phases, their transport of latent transitions between liquid and vapor. TOUGH takes account of fluid flow in both liquid and gaseous phases occurring under pressure, viscous, and gravity forces according to Darcy's law. Interference between the phases is represented by means of relative permeability functions. The code handles binary, but not Knudsen, diffusion in the gas phase and capillary and phase absorption effects for the liquid phase. Heat transport occurs by means of conduction with thermal conductivity dependent on water saturation, convection, and binary diffusion, which includes both sensible and latent heat. 2 - Method of solution: All

  16. On crystallisation and fracture toughness of poly(phenylene sulphide) under tape placement conditions

    NARCIS (Netherlands)

    Grouve, Wouter Johannes Bernardus; Vanden Poel, G.; Warnet, Laurent; Akkerman, Remko

    2013-01-01

    Fibre reinforced thermoplastic tapes are subjected to high heating and cooling rates during the tape placement process. Such high cooling rates can significantly inhibit the crystallisation of the thermoplastic polymer and thereby affect its mechanical properties, such as strength or toughness. In

  17. 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.

  18. Flexibility of feeding movements in pigs: effects of changes in food toughness and stiffness on the timing of jaw movements.

    Science.gov (United States)

    Montuelle, Stéphane J; Olson, Rachel; Curtis, Hannah; Sidote, JoAnna; Williams, Susan H

    2018-01-29

    In mammals, chewing movements can be modified, or flexible, in response to changes in food properties. Variability between and within food in the temporal characteristics of chewing movements can impact chewing frequency and rhythmicity, which in turn may affect food breakdown, energy expenditure and tooth wear. Here, we compared total chewing cycle duration and intra-cycle phase durations in pigs chewing on three foods varying in toughness and stiffness: apples (low toughness, low stiffness), carrots (high toughness, low stiffness), and almonds (high toughness, high stiffness). We also determined whether within-food variability in timing parameters is modified in response to changes in food properties. X-ray Reconstruction Of Moving Morphology (XROMM) demonstrates that the timing of jaw movements are flexible in response to changes in food properties. Within each food, pigs also exhibited flexibility in their ability to vary cycle parameters. The timing of jaw movements during processing of high-toughness foods is more variable, potentially decreasing chewing rhythmicity. In contrast, low-toughness foods result in jaw movements that are more stereotyped in their timing parameters. In addition, the duration of tooth-food-tooth contact is more variable during the processing of low-stiffness foods compared with tough or stiff foods. Increased toughness is suggested to alter the timing of the movements impacting food fracture whereas increased stiffness may require a more cautious control of jaw movements. This study emphasizes that flexibility in biological movements in response to changes in conditions may not only be observed in timing but also in the variability of their timing within each condition. © 2018. Published by The Company of Biologists Ltd.

  19. Resin selection criteria for tough composite structures

    Science.gov (United States)

    Chamis, C. C.; Smith, G. T.

    1983-01-01

    Resin selection criteria are derived using a structured methodology consisting of an upward integrated mechanistic theory and its inverse (top-down structured theory). These criteria are expressed in a "criteria selection space" which are used to identify resin bulk properties for improved composite "toughness". The resin selection criteria correlate with a variety of experimental data including laminate strength, elevated temperature effects and impact resistance.

  20. Fracture-toughness variations in Alloy 718

    International Nuclear Information System (INIS)

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

    1983-04-01

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

  1. 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.

  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. Microstructure, tensile and toughness properties after quenching and partitioning treatments of a medium-carbon steel

    International Nuclear Information System (INIS)

    Paravicini Bagliani, E.; Santofimia, M.J.; Zhao, L.; Sietsma, J.; Anelli, E.

    2013-01-01

    The effect of different microstructures on the tensile and toughness properties of a low alloy medium carbon steel (0.28C–1.4Si–0.67Mn–1.49Cr–0.56Mo wt%) was investigated, comparing the properties obtained after the application of selected quenching and partitioning (Q and P) and quenching and tempering (Q and T) treatments. After Q and T the strength–toughness combination was the lowest, whereas the best combination was achieved by Q and P, as a result of the carbon depletion of the martensite and the high stabilization of the austenite. Nonetheless, the presence of islands of martensite/austenite (MA) constituents after Q and P treatments prevented the achievement of toughness levels comparable to the ones currently obtainable with other steels and heat treatments.

  4. 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.

  5. Use of Circumferentially Cracked Bar sample for CTOD fracture toughness determination in the upper shelf regime

    Directory of Open Access Journals (Sweden)

    D. Gentile

    2014-10-01

    Full Text Available In this work, the use of circumferentially cracked bar (CCB sample to determine material fracture toughness in the upper shelf regime for carbon steels has been investigated. Since high fracture toughness materials are known to exhibit extensive crack tip blunting before ductile crack initiation, accurate specimen design is required to provide realistic fracture toughness measurement. Here, a CCB was designed to have similar loss of constraint as for SENT sample. Continuum damage mechanics was used to predict the occurrence of ductile crack initiation and propagation. Finite element analysis was performed to predict specimen response and to compare computed J-integral crack driving force with measured CTOD. Finally, experimental tests were performed on X65 carbon steel and the measured critical CTOD was compared with available fracture data obtained with SENT.

  6. 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.

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

    Science.gov (United States)

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

    2017-11-10

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

  8. 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.

  9. 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.

  10. Mental toughness in sport questionnaire – MTSQ

    Directory of Open Access Journals (Sweden)

    Jacek Przybylski

    2017-12-01

    Full Text Available Background Stress resistance is very substantial and interesting for scientists, competitors, coaches, and psychologists. The main aim of the article was the psychometric examination of mental toughness in the sport questionnaire (MTSQ. Participants and procedure The group of participants consisted of athletes presenting different levels of experience: Olympians, first-league, national team: N = 421 athletes, including 190 women and 231 men, age M = 20.40, SD = 5.30. Test procedure: 124 statements were selected for exploratory factor analysis with the method of main components with rotation of intercorrelational orthogonal factors. It was used in order to check the factor structure of the tool and for the clear interpretation of isolated factors. As a result of the validation, 42 statements were finally selected measuring three dimensions of mental toughness. Each subscale consisted of 14 items. Next the reliability and the validity of the questionnaire were analysed. Results The three-factor structure of the measured model of stress resistance accurately reflects the relation among stress resistances factors. Individual scales, at least mutually correlated, present accurate and reliable operationalisation of dimensions of the stress resistance. Conclusions The mental toughness in sport questionnaire (MTSQ presents accurate and reliable operationalisation of stress resistance dimensions.

  11. Tough Blends of Polylactide and Castor Oil

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-10-10

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

  12. Tough blends of polylactide and castor oil.

    Science.gov (United States)

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

    2011-09-01

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

  13. 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.

  14. Characterization of cylinder liners produced with hypereutectic Al-Si alloys and investigation of corrosion behaviour in synthetic automotive condensed solution

    International Nuclear Information System (INIS)

    Santos, Hamilta de Oliveira

    2006-01-01

    In the present study four hypereutectic Al-Si alloys, three produced by spray forming and one by casting, were characterized for microhardness, roughness, microstructure, texture and corrosion resistance in a synthetic automotive condensed solution (SACS). Two of the spray formed alloys tested were obtained from cylinder liners and the other was laboratory made. Spray forming involves alloy atomization and droplets deposition on a substrate, previous to the solidification of all of the droplets. This process favours the production of materials with a fine microstructure free of macrosegregation that is related to improved hot workability. The microstructure characterization of the four alloys revealed the presence of porosities in the laboratory made alloy. All the three alloys produced by spray forming showed a homogeneous distribution of primary precipitates. The microstructure of one of the alloys showed eutectic microstructure, indicating that this alloy was fabricated by casting. In the cylinder liners, the surface roughness was measured and the microhardness of all the alloys was also evaluated. Furthermore, the laboratory made alloy was hot and cold rolled. Texture determinations were carried out to investigate the correlation between the alloy type and their fabrication process. The texture investigation indicated that the fine distribution of primary silicon phase in the alloy hindered the development of texture typical of aluminium alloys deformation, even after severe mechanical work, such as those used in the conversion of pre-formed in cylinder liners. The surface roughness results indicated typical characteristics of the surface finishing used, honing or chemical etching. The microhardness results were dependent on the fabrication process used, with higher microhardness associated to the eutectic alloy comparatively to the spray formed ones. All hypereutectic alloys were tested for corrosion resistance using electrochemical impedance spectroscopy in

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

    International Nuclear Information System (INIS)

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

    2012-01-01

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

  16. The dislocation crack model, as applied to determining the crack toughness of metals

    International Nuclear Information System (INIS)

    Pfuff, M.

    1982-01-01

    The representation of cracks by dislocations, which will be introduced and briefly applied to classical crack problems, reduces the calculation of the fracture toughness of plastically deformable solids to the calculation of the energy of continuous distributions of dislocations. The crack model introduced by Bilby, Cottrell and Swinden will be modified in order to take the conditions into account which are necessary to activate the dislocation sources at the crack tip. This leads to a fracture criterion which can be used to explain the high values of the fracture toughness measured for metalls and the characteristic brittle-to-ductile transition. (orig.) [de

  17. A comparative study on wear behavior of TiN and diamond coated WC-Co substrates against hypereutectic Al-Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Chakravarthy, G.V. [Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Madras 600036 (India); Chandran, Maneesh, E-mail: maneesh@physics.iitm.ac.in [Nano Functional Materials Technology Centre, Department of Physics, Indian Institute of Technology, Madras 600036 (India); Bhattacharya, S.S. [Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Madras 600036 (India); Rao, M.S. Ramachandra [Nano Functional Materials Technology Centre, Department of Physics, Indian Institute of Technology, Madras 600036 (India); Kamaraj, M., E-mail: kamaraj@iitm.ac.in [Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Madras 600036 (India)

    2012-11-15

    Highlights: Black-Right-Pointing-Pointer Wear behaviors of diamond/WC-Co, TiN/WC-Co and WC-Co against Al-Si were studied. Black-Right-Pointing-Pointer Both TiN and diamond coatings were done using chemical vapor deposition technique. Black-Right-Pointing-Pointer Friction and sliding wear properties were characterized using a pin-on-disc method. Black-Right-Pointing-Pointer Diamond coated WC-Co pins showed one order less wear loss than bare WC-Co pins. Black-Right-Pointing-Pointer A weight gain was observed for the TiN coated WC-Co pins. Black-Right-Pointing-Pointer Average coefficient of friction was lowest for the diamond coated WC-Co pins. - Abstract: The demand for better tools for machining hypereutectic aluminum-silicon (Al-Si) alloys are increasing day by day since the extensive use of these alloys in internal combustion engines. In addition to the lifetime of the machining tool, surface finish of the machined piece is also equally important, as it directly affects the performance of the engine. In this paper, we compared the wear behavior of bare tungsten carbide (WC-Co), titanium nitride (TiN) coated WC-Co and diamond coated WC-Co substrates against Al-Si alloys using pin-on-disc method. Both TiN and diamond coatings were done using chemical vapor deposition technique. Diamond coated WC-Co substrates show one order less wear loss compared to the bare WC-Co substrates. Instead of weight loss, a weight gain was observed for the TiN coated WC-Co substrates. Average coefficient of friction was lowest for the diamond coated WC-Co substrates due to the different wear behavior of diamond coated tribological system, which is explained in detail.

  18. THE EFFECT OF STRAIN RATE ON FRACTURE TOUGHNESS OF HUMAN CORTICAL BONE: A FINITE ELEMENT STUDY

    Science.gov (United States)

    Ural, Ani; Zioupos, Peter; Buchanan, Drew; Vashishth, Deepak

    2011-01-01

    Evaluating the mechanical response of bone under high loading rates is crucial to understanding fractures in traumatic accidents or falls. In the current study, a computational approach based on cohesive finite element modeling was employed to evaluate the effect of strain rate on fracture toughness of human cortical bone. Two-dimensional compact tension specimen models were simulated to evaluate the change in initiation and propagation fracture toughness with increasing strain rate (range: 0.08 to 18 s−1). In addition, the effect of porosity in combination with strain rate was assessed using three-dimensional models of microcomputed tomography-based compact tension specimens. The simulation results showed that bone’s resistance against the propagation of fracture decreased sharply with increase in strain rates up to 1 s−1 and attained an almost constant value for strain rates larger than 1 s−1. On the other hand, initiation fracture toughness exhibited a more gradual decrease throughout the strain rates. There was a significant positive correlation between the experimentally measured number of microcracks and the fracture toughness found in the simulations. Furthermore, the simulation results showed that the amount of porosity did not affect the way initiation fracture toughness decreased with increasing strain rates, whereas it exacerbated the same strain rate effect when propagation fracture toughness was considered. These results suggest that strain rates associated with falls lead to a dramatic reduction in bone’s resistance against crack propagation. The compromised fracture resistance of bone at loads exceeding normal activities indicates a sharp reduction and/or absence of toughening mechanisms in bone during high strain conditions associated with traumatic fracture. PMID:21783112

  19. iTOUGH2 Universal Optimization Using the PEST Protocol

    International Nuclear Information System (INIS)

    Finsterle, S.A.

    2010-01-01

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

  20. 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

  1. Tenacidade à fratura translaminar dinâmica de um laminado híbrido metal-fibra para uso em elevadas temperaturas Translaminar dynamic fracture toughness of a hybrid fiber-metal laminate devised to high-temperature applications

    Directory of Open Access Journals (Sweden)

    José R. Tarpani

    2010-01-01

    Full Text Available A tenacidade à fratura translaminar dinâmica do laminado híbrido metal-fibra titânio-grafite com matriz termoplástica foi determinada sob as velocidades de impacto de 2,25 e 5,52 m/s, no intervalo de temperaturas de -196 a +180 °C, e comparada à de laminados compósitos convencionais de fibras de carbono e resina epóxi. Constatou-se que o laminado híbrido exibe uma tenacidade à iniciação da fratura inferior à dos compósitos tradicionais com fibras na forma de fita unidirecional, porém superior à dos laminados convencionais com fibras na forma de tecido bidirecional. Os ensaios de impacto revelaram que, comparativamente ao desempenho mecânico dos laminados carbono-epóxi, o emprego do laminado híbrido metal-fibra se justifica mais pela sua resistência à propagação do que à iniciação da fratura dinâmica.The translaminar dynamic fracture toughness of titanium-graphite hybrid fiber-metal laminate with thermoplastic matrix has been determined at the impact velocities of 2.25 and 5.52 m/s, within the temperature range from -196 to +180 ºC, and compared to that of conventional carbon-epoxy composite laminates. The hybrid laminate exhibits lower initiation fracture toughness than traditional unidirectional tape composites though it is tougher than conventional woven fabric laminates. Impact tests revealed that, if compared to the mechanical performance of conventional carbon-epoxy laminates, the fiber-metal laminate application must rely on its resistance to dynamic fracture propagation rather than on fracture initiation.

  2. 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.

  3. Effect of holding time in the ({alpha} + {gamma}) temperature range on toughness of specially austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, T.; Yamada, S. [Toyohashi Univ. of Technology (Japan). Dept. of Production Systems Engineering

    1996-07-01

    Austempered ductile iron (ADI) finds wide application in the industry because of its high strength and toughness. The QB{prime} process has been developed to produce a fine microstructure with high fracture toughness in ADI. This process involves reaustenitizing a prequenched ductile iron in the ({alpha} + {gamma}) temperature range followed by an isothermal treatment in the bainitic transformation temperature range. In the present work, the effect of holding time in the ({alpha} + {gamma}) temperature range on the structure and un-notched toughness of ADI has been studied. Prior to the austempering treatment, the as-cast ductile iron was heat treated to obtain martensitic, ferritic, and pearlitic matrix structures. In the case of prequenched material (martensitic matrix), the un-notched impact toughness increased as a function of holding time in the ({alpha} + {gamma}) temperature range. The reaustenitization heat treatment also resulted in the precipitation of fine carbide particles, identified as (Fe,Cr,Mn){sub 3}C. It was shown that the increase in holding time in the ({alpha} + {gamma}) temperature range leads to a reduction in the number of carbide particles. In the case of a ferritic prior structure, a long duration hold in the ({alpha} + {gamma}) temperature range resulted in the coarsening of the structure with a marginal increase in the toughness. In the case of a pearlitic prior structure, the toughness increased with holding time. This was attributed to the decomposition of the relatively stable carbide around the eutectic cell boundary with longer holding times.

  4. The mediating role of mental toughness in sport.

    Science.gov (United States)

    Nicholls, A R; Perry, J L; Jones, L; Sanctuary, C; Carson, F; Clough, P J

    2015-01-01

    We conducted two studies that examined different models, which included mental toughness and psychological constructs that are thought to be related to this construct. In Study 1, 531 athletes completed measures of mental toughness, resilience, and emotional intelligence. In Study 2, 522 athletes completed measures of mental toughness, sport motivation, and self-efficacy. There were positive paths between the constructs in the model, which were mediated by mental toughness in Study 1. Further, there was a positive path between mental toughness and self-efficacy, but negative paths with introjected regulation and amotivation in Study 2. This two study paper suggests that it might also be the presence of constructs such as resilience, emotional intelligence, motivation, and/or self-efficacy that enable mentally tough individuals to excel under stressful circumstances rather than just coping.

  5. Coupling Effect of Water and Proteoglycans on the In Situ Toughness of Bone.

    Science.gov (United States)

    Wang, Xiaodu; Xu, Haoran; Huang, Yehong; Gu, Sumin; Jiang, Jean X

    2016-05-01

    Proteoglycans (PGs) are one type of noncollagenous proteins in the extracellular matrix of bone that primarily contain a core protein and glycosaminoglycans (GAGs). GAGs are highly polar and negatively charged, thus have a strong tendency to attract water molecules into the matrix. We hypothesized in this study that PGs in bone play a pivotal role in sustaining the toughness of the tissue only when water is present. To test the hypothesis, we used a novel nanoscratch test to measure the in situ toughness of human cadaveric bone treated with and without peptide-N-glycosidase F (PNGase F), an enzyme that specifically removes the N-linked oligosaccharides of GAGs from core proteins. Cortical bone specimens were prepared from the posterior aspect of mid-diaphyseal femurs of six (n = 6) male human donors between 51.5 ± 5.17 years old. Biochemical and histochemical assays were used to verify whether N-linked oligosaccharides were removed from bone matrix by PNGase F. By testing wet and dehydrated bone specimens, the coupling effect between water and PGs on the in situ toughness of bone was investigated. The two-way ANOVA analyses showed that removal of GAGs had significant effects on the in situ toughness of wet bone samples. In contrast, the removal of GAGs did not show significant effects on the toughness of dry bone. The results of this study, for the first time, suggest that GAGs play a pivotal role in the in situ toughness of bone only when water is present, and vice versa, water functions as a plasticizer in bone only when GAGs are present. © 2015 American Society for Bone and Mineral Research. © 2015 American Society for Bone and Mineral Research.

  6. 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 ...

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

    Indian Academy of Sciences (India)

    Unknown

    *Also at National Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, ... By controlling weld heat input (E ≤ 20 kJ/cm), the impact toughness in the HAZ can be assured. Keywords. Super-high strength steel; heat-affected zone; ... (SEM) and transmission electron microscope (TEM). It.

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

    Indian Academy of Sciences (India)

    sonable economy and high allowable design stresses, they are widely used in the construction of engineering machi- nery, bridges, buildings, ships, pipeline, etc (Fukumoto 1996;. Zhao et al 2002). TMCP technology makes it possible to obtain excellent combination of strength and toughness with the microstructure of low ...

  9. 46 CFR 57.06-5 - Production toughness testing.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Production toughness testing. 57.06-5 Section 57.06-5... Production Tests § 57.06-5 Production toughness testing. (a) In addition to the test specimens required by § 57.06-4(a), production toughness test plates shall be prepared for Classes I-L and II-L pressure...

  10. A tough truck for ATLAS

    CERN Multimedia

    2003-01-01

    One of the mobile support structures that will be used to manoeuvre and assemble components of the ATLAS detector in its cavern was put through its paces at the end of July and passed its load tests with flying colours. The tests, which involved the surveyors taking measurements to detect any load-induced mechanical deformations, were carried out in Building 191. "The "truck" has been subjected to static tests with loads of up to 1250 tonnes and can carry and transport on air cushions a nominal load of up to 1000 tonnes at a top speed of 30 cm per minute," explains project leader Tommi Nyman. "It took two weeks to assemble the truck's components, the last of which arrived at CERN on 24 June. It then took a further 20 days to load the truck up for the test." The 8.5 metre-high truck will be used for final assembly of some of the ATLAS components, including the calorimeters, in cavern UX15. This powerful device is the result of a collaboration between CERN and the Henryk Niewodniczanski Institute of Nuclear ...

  11. 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.

  12. Modifications and additions to selected TOUGH2 modules

    International Nuclear Information System (INIS)

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

    1998-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Rutqvist, J.

    2010-06-01

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

  15. 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.

  16. When the going gets tough: Mental toughness and its relationship with behavioural perseverance.

    Science.gov (United States)

    Gucciardi, Daniel F; Peeling, Peter; Ducker, Kagan J; Dawson, Brian

    2016-01-01

    This study examined the association between self-reported mental toughness and behavioural perseverance among a sample of male Australian footballers in a naturalistic context. Cross-sectional field study, with the multistage 20m shuttle run test (MST) employed as a proxy for behavioural perseverance. 330 male Australian footballers aged between 15 and 18 years (M=16.86; SD=.71) with between 2 and 14 years playing experience (M=9.32; SD=2.51) participated. Initially, footballers completed a mental toughness questionnaire, before having their height and body mass measurements taken. Subsequently, a performance testing session was completed, which included the 20m sprint, Australian football-specific agility run, vertical jump, and the MST. Bayesian estimation was employed to allow for the simultaneous examination of existing findings with our new data in a way that provides an automatic meta-analysis of evidence in this area. The analysis indicated a 95% probability that the association between mental toughness and behavioural perseverance lies between .14 and .34, even when controlling for other factors known to influence MST performance, including age, height, body mass, and years playing experience. Taken together with previous research, these findings support the theoretical proposition that persistence, effort or perseverance represents a behavioural signature of mental toughness. Copyright © 2014 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  17. Mental toughness in elite football officiating

    OpenAIRE

    Slack, Liam A.

    2013-01-01

    The overall purpose of this Ph.D. thesis was to identify factors underpinning football\\ud officiating excellence. As a result, this thesis provided an in-depth study into\\ud understanding Mental Toughness (MT) and its development within elite football\\ud referees. A secondary purpose was to use the findings of the series of studies contained\\ud herein, to bridge the gap between theory and applied practice by providing\\ud recommendations for football officiating National Governing Bodies (NGBs...

  18. 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.

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

    Science.gov (United States)

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

    2016-07-11

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

  20. Investigation on fracture toughness of laser beam welded steels

    Energy Technology Data Exchange (ETDEWEB)

    Riekehr, S.; Cam, G.; Santos, J.F. dos; Kocak, M. [GKSS-Forschungszentrum Geesthacht GmbH (Germany); Klein, R.M.; Fischer, R. [Thyssen Laser-Technik GmbH, Aachen (Germany)

    1999-11-01

    Laser beam welding is currently used in the welding of a variety of structural materials including hot and cold rolled steels, high strength low alloy and stainless steels, aluminium and titanium alloys, refractory and high temperature alloys and dissimilar materials. This high power density welding process has unique advantages of cost effectiveness, low distortion, high welding speed, easy automation, deep penetration, narrow bead width, and narrow HAZ compared to the conventional fusion welding processes. However, there is a need to understand the deformation and fracture properties of laser beam weld joints in order to use this cost effective process for fabrication of structural components fully. In the present study, an austenitic stainless steel, X5CrNi18 10 (1.4301) and a ferritic structural steel, RSt37-2 (1.0038), with a thickness of 4 mm were welded by 5 kW CO{sub 2} laser process. Microhardness measurements were conducted to determine the hardness profiles of the joints. Flat microtensile specimens were extracted from the base metal, fusion zone, and heat affected zone of ferritic joint to determine the mechanical property variation across the joint and the strength mismatch ratio between the base metal and the fusion zone. Moreover, fracture mechanics specimens were extracted from the joints and tested at room temperature to determine fracture toughness, Crack Tip Opening Displacement (CTOD), of the laser beam welded specimens. The effect of the weld region strenght mis-matching on the fracture toughness of the joints have been evaluated. Crack initiation, crack growth and crack deviation processes have also been examined. These results were used to explain the influence of mechanical heterogeneity of the weld region on fracture behaviour. This work is a part of the ongoing Brite-Euram project Assessment of Quality of Power Beam Weld Joints (ASPOW). (orig.)

  1. Effect of Thermal Aging on SCC, Material Properties and Fracture Toughness of Stainless Steel Weld Metals

    Science.gov (United States)

    Lucas, T.; Ballinger, R. G.; Hanninen, H.; Saukkonen, T.

    An experimental program has been conducted in order to understand how the spinodal decomposition may affect material properties changes in Type 316L BWR pipe weld metals. The program includeed Charpy-V, tensile, SCC crack growth and in-situ fracture toughness testing as a function of aging time and temperature. In this paper we report results of fracture toughness, SCC crack growth rate and fracture morphology studies of Type 316L stainless steel weld metals under simulated BWR conditions, consisting of 288°C, high purity water containing 300 ppb dissolved oxygen (defined for purposes of this paper as "In-Situ"). SCC crack growth results show an approximately 2X increase in crack growth rate over that of the unaged material. In-situ fracture toughness measurements indicate that environmental exposure can result in a reduction of toughness by up to 40% over the corresponding at-temperature air values. Detailed analysis of the results strongly suggest that spinodal decomposition is responsible for the degradation in properties measured ex-environment. Analysis of the results also strongly suggests that the in-situ properties degradation is the result of hydrogen absorbed by the material during exposure to the high temperature aqueous environment.

  2. Effect of mixing rate and temperature on primary Si phase of hypereutectic Al-20Si alloy during controlled diffusion solidification (CDS process

    Directory of Open Access Journals (Sweden)

    Yuan-dong Li

    2015-05-01

    Full Text Available Controlled Diffusion Solidification (CDS is a promising process relied on mixing two liquid alloys of precisely controlled chemistry and temperature in order to produce a predetermined alloy composition. In this study, the CDS was employed to prepare hypereutectic Al-20%Si (mass fraction alloy using Al-30%Si and pure Al of different temperatures. The mixing rate was controlled using three small crucibles with a hole of different diameters in their bottom. The effect of mixing rate and temperature on the microstructure of the primary Si-phase during the mixing of molten Al and Al-30%Si was studied. The results showed that when the diameter of the small crucible bottom hole is 16 mm, a higher mass mixing rate 0.217 kg·s-1 would results in a lower stream velocity 0.414 m·s-1. Conversely a lower mass mixing rate 0.114 kg·s-1 (the diameter of the small crucible bottom hole is 8 mm would result in a higher fluid stream velocity 0.879 m·s-1. A lower mass mixing rate would be better to refine the primary Si than a higher mass mixing rate. Meanwhile, the morphology and distribution of primary Si could also be improved. Especially, when Al-30%Si alloy at 820 °C was mixed with pure Al at 670 °C in the case of a mass mixing rate of 0.114 kg·s-1 and a pouring temperature of 680 °C, the average size of the primary Si phase would be only 18.2 μm. Its morphology would mostly be octahedral and the primary Si would distribute uniformly in the matrix microstructure. The lower mass mixing rate (0.114 kg·s-1 will enhance the broken tendency of Al-30%Si steam and the mixing agitation of resultant melt, so the primary Si phase can be better refined.

  3. Independent Tuning Stiffness and Toughness of Polymer Metal Composites: Modeling, Validation, and Design

    Science.gov (United States)

    Nasr Esfahani, Sajedeh

    Titanium (Ti) alloys are one of the most used metals for biomedical applications, specifically in making implants. The stiffness of the dense Ti is 80-110 GPa, while the stiffness of the compact bone is 12-20 GPa. This high difference between the stiffness of the Ti alloys and compact bone results in stress shielding of the bone and stress concentration at the implant, both of which are undesirable and could result in implant failure. An alternative method to reduce the stiffness of a dense implant and avoid the stress shielding is adding porosity to the structure. This however results in considerable reduction in the toughness of the structure, which is also undesirable for the long-term success of implants. Also, implants such as knee and spine should have high fracture toughness, which is not achievable with porous structures. In this work, we study a new method for independently tuning the stiffness and toughness of the material by adding various polymers to the additively manufactured Ti structures with engineered porosity. Porous Ti samples with different levels of porosity are fabricated using selective laser melting. Various types of thermoplastic polymers including High Density Polyethylene (HDPE), Polyethylene Terephthalate (PET), and Nylon (MXD6) are used to fill the pores to make the titanium-polymer composite parts. Compression simulations and tests are performed on both porous and composite specimens to compare the mechanical behavior of these structures. A set of finite element simulations is conducted on different structures, and the results are verified with experiments. Simulation results and experimental findings indicate that filling porous Ti with thermoplastic polymers leads to an increase in the toughness of the structure. The percentage increase of the toughness depends on several parameters such as the geometry of the porosity, the percentage of the porosity, and the type of the polymer. Also, a design algorithm is developed based on the

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

    International Nuclear Information System (INIS)

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

    1992-01-01

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

  5. 46 CFR 54.05-5 - Toughness test specimens.

    Science.gov (United States)

    2010-10-01

    ... Toughness Tests § 54.05-5 Toughness test specimens. (a) Charpy V-notch impact tests. Where required, Charpy... used to qualify materials within the scope of this subpart. Each set of Charpy impact tests shall... correlate with the nil-ductility transition temperature determined by the drop-weight tests for the steels...

  6. 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.

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

    DEFF Research Database (Denmark)

    Poulsen, Anders

    2003-01-01

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

  8. 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...

  9. 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.

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

    International Nuclear Information System (INIS)

    Picker, C.

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

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

    International Nuclear Information System (INIS)

    Moskovic, R.

    1988-01-01

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

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

    International Nuclear Information System (INIS)

    Capeletti, T.L.

    1976-01-01

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

  13. The effect of electric discharge machined notches on the fracture toughness of several structural alloys

    International Nuclear Information System (INIS)

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

    1993-09-01

    Recent computational studies of the stress and strain fields at the tip of very sharp notches have shown that the stress and strain fields are very weakly dependent on the initial geometry of the notch once the notch has been blunted to a radius that is 6 to 10 times the initial root radius. It follows that if the fracture toughness of a material is sufficiently high so that fracture initiation does not occur in a specimen until the crack-tip opening displacement (CTOD) reaches a value from 6 to 10 times the size of the initial notch tip diameter, then the fracture toughness will be independent of whether a fatigue crack or a machined notch served as the initial crack. In this experimental program the fracture toughness (J Ic and J resistance (J-R) curve, and CTOD) for several structure alloys was measured using specimens with conventional fatigue cracks and with EDM machined notches. The results of this program have shown, in fact, that most structural materials do not achieve initiation CTOD values on the order of 6 to 10 times the radius of even the smallest EDM notch tip presently achievable. It is found furthermore that tougher materials do not seem to be less dependent on the type of notch tip present. Some materials are shown to be much more dependent on the type of notch tip used, but no simple pattern is found that relates this observed dependence to the material strength toughness, or strain hardening rate

  14. Irradiation effects on thermal shock resistance and its fracture toughness of HTGR graphites

    International Nuclear Information System (INIS)

    Sato, Sennosuke; Imamura, Yoshio; Kawamata, Kiyohiro; Awaji, Hideo; Oku, Tatsuo.

    1979-01-01

    This paper describes changes in the thermal shock resistance delta = σsub(t)k / E alpha (σsub(t): tensile strength, k: thermal conductivity, E: Young's modulus, alpha : coefficient of thermal expansion) and the thermal shock fracture toughness delta = K sub( ic)k / E alpha (K sub( ic): fracture toughness value of the mode I) in addition to usual mechanical properties including the diametral compressive strength and fracture toughness of four varieties of graphite (IM2-24, 7477, H327 and SMG) for the high temperature gas-cooled reactor due to neutron irradiations of (1.6 -- 2.3) x 10 21 n/cm 2 ( gt 0.18 MeV) at 600 -- 850 0 C. These experiments are carried out by means of our recently developed techniques using small disk type specimens which are very effective for a capsule irradiation in the JMTR. Both the thermal shock resistance and the thermal shock fracture toughness of graphites after irradiation are expressed to decrease remarkably in contrast with the increase of the usual mechanical strength. (author)

  15. Shape effect of ultrafine-grained structure on static fracture toughness in low-alloy steel

    Science.gov (United States)

    Inoue, Tadanobu; Kimura, Yuuji; Ochiai, Shojiro

    2012-01-01

    A 0.4C-2Si-1Cr-1Mo steel with an ultrafine elongated grain (UFEG) structure and an ultrafine equiaxed grain (UFG) structure was fabricated by multipass caliber rolling at 773 K and subsequent annealing at 973 K. A static three-point bending test was conducted at ambient temperature and at 77 K. The strength–toughness balance of the developed steels was markedly better than that of conventionally quenched and tempered steel with a martensitic structure. In particular, the static fracture toughness of the UFEG steel, having a yield strength of 1.86 GPa at ambient temperature, was improved by more than 40 times compared with conventional steel having a yield strength of 1.51 GPa. Furthermore, even at 77 K, the fracture toughness of the UFEG steel was about eight times higher than that of the conventional and UFG steels, despite the high strength of the UFEG steel (2.26 GPa). The UFG steel exhibited brittle fracture behavior at 77 K, as did the conventional steel, and no dimple structure was observed on the fracture surface. Therefore, it is difficult to improve the low-temperature toughness of the UFG steel by grain refinement only. The shape of crystal grains plays an important role in delamination toughening, as do their refinement and orientation. PMID:27877493

  16. 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.

  17. 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.

  18. Heat treatment effect on fracture toughness of F82H irradiated in HFIR

    Science.gov (United States)

    Okubo, N.; Sokolov, M. A.; Tanigawa, H.; Hirose, T.; Jitsukawa, S.; Sawai, T.; Odette, G. R.; Stoller, R. E.

    2011-10-01

    Irradiation hardening and fracture toughness of reduced-activation ferritic/martensitic steel F82H after irradiation were investigated with a focus on changing the fracture toughness transition temperature as a result of several heat treatments. The specimens were standard F82H-IEA (IEA), F82H-IEA with several heat treatments (Mod1 series) and a heat of F82H (Mod3) containing 0.1% tantalum. The specimens were irradiated up to 20 dpa at 300 °C in the High Flux Isotope Reactor under a collaborative research program between JAEA/US-DOE. The results of hardness tests showed that irradiation hardening of IEA was comparable with that of Mod3. However, the fracture toughness-transition temperature of Mod3 was lower than that of IEA. The transition temperature of Mod1 was also lower than that of the IEA heat. These results suggest that optimization of specifications on the heat treatment condition and modification of the minor alloying elements seem to be effective to reduce the fracture toughness-transition temperature after irradiation.

  19. On the performance of a novel grain refiner in hyper-eutectic Al-Si cast alloys

    OpenAIRE

    Bolzoni, L; Nowak, M; Hari Babu, N

    2014-01-01

    The stringent requirements for pollution reduction are pushing the automotive industry towards the employment of lightweight structures and, therefore, aluminium and its alloys play a remarkable role. Al-Si casting alloy with eutectic or hyper- eutectic compositions are, normally, employed for the production of high performance automotive products such as pistons and engine blocks which have to withstand critical loading conditions (i.e. high temperature, high pressure and corrosive exhaust g...

  20. Identifying Novel Clinical Surrogates to Assess Human Bone Fracture Toughness.

    Science.gov (United States)

    Granke, Mathilde; Makowski, Alexander J; Uppuganti, Sasidhar; Does, Mark D; Nyman, Jeffry S

    2015-07-01

    Fracture risk does not solely depend on strength but also on fracture toughness; ie, the ability of bone material to resist crack initiation and propagation. Because resistance to crack growth largely depends on bone properties at the tissue level, including collagen characteristics, current X-ray based assessment tools may not be suitable to identify age-related, disease-related, or treatment-related changes in fracture toughness. To identify useful clinical surrogates that could improve the assessment of fracture resistance, we investigated the potential of (1)H nuclear magnetic resonance spectroscopy (NMR) and reference point indentation (RPI) to explain age-related variance in fracture toughness. Harvested from cadaveric femurs (62 human donors), single-edge notched beam (SENB) specimens of cortical bone underwent fracture toughness testing (R-curve method). NMR-derived bound water showed the strongest correlation with fracture toughness properties (r = 0.63 for crack initiation, r = 0.35 for crack growth, and r = 0.45 for overall fracture toughness; p toughness properties were best explained by a combination of NMR properties including pore water and RPI-derived tissue stiffness with age as a significant covariate (adjusted R(2)  = 53.3%, 23.9%, and 35.2% for crack initiation, crack growth, and overall toughness, respectively; p toughness and emphasize the utility of a multimodal assessment of fracture resistance. Exploring the mechanistic origin of fracture toughness, glycation-mediated nonenzymatic collagen crosslinks and intracortical porosity are possible determinants of bone fracture toughness and could explain the sensitivity of NMR to changes in fracture toughness. Assuming fracture toughness is clinically important to the ability of bone to resist fracture, our results suggest that improvements in fracture risk assessment could potentially be achieved by accounting for water distribution (quantitative ultrashort echo time magnetic

  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. Fracture toughness for copper oxide superconductors

    Science.gov (United States)

    Goretta, Kenneth C.; Kullberg, Marc L.

    1993-01-01

    An oxide-based strengthening and toughening agent, such as tetragonal Zro.sub.2 particles, has been added to copper oxide superconductors, such as superconducting YBa.sub.2 Cu.sub.3 O.sub.x (123) to improve its fracture toughness (K.sub.IC). A sol-gel coating which is non-reactive with the superconductor, such as Y.sub.2 BaCuO.sub.5 (211) on the ZrO.sub.2 particles minimized the deleterious reactions between the superconductor and the toughening agent dispersed therethrough. Addition of 20 mole percent ZrO.sub.2 coated with 211 yielded a 123 composite with a K.sub.IC of 4.5 MPa(m).sup.0.5.

  3. 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.

  4. Toughness and Embrittlement of RPV Steels Using Ultrasonic Measurements

    International Nuclear Information System (INIS)

    Hiser, Allen L. Jr.

    2004-01-01

    This paper summarizes the findings from an effort addressing the use of ultrasonic attenuation as a suitable parameter for nondestructive determination of irradiation embrittlement in reactor pressure vessel (RPV) steels. The materials examined in this study include one heat of RPV steel that was heat treated to induce changes in its fracture toughness, several heats of RPV steel irradiated to assess neutron embrittlement changes in fracture toughness, and a matrix of RPV steels (in the unirradiated condition) with a range of as-fabricated fracture toughness levels. The following observations can be made. -) The results indicate that ultrasonic attenuation is generally able to identify differences in responses for samples with different toughness levels, although in some cases the differences in ultrasonic responses are small. -) Plate and weld materials provide different trends of attenuation changes with changes in material toughness. -) For the single forging studied in 2 irradiated conditions, the attenuation measurements provided mixed results. -) Differences in fracture toughness that arise from damage of a microstructure result in more different responses in ultrasonic attenuation than differences in fracture toughness that arise from as-fabricated differences in microstructure

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

    Science.gov (United States)

    Elgart-Berry, Alison

    2004-04-01

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

  6. 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).

  7. 46 CFR 54.05-10 - Certification of material toughness tests.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Certification of material toughness tests. 54.05-10... PRESSURE VESSELS Toughness Tests § 54.05-10 Certification of material toughness tests. (a) Plate material..., toughness qualifications shall be determined by the Commandant based on material, chemical, and mechanical...

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

    Science.gov (United States)

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

    2015-05-06

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

  9. 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.

  10. Suturing property of tough double network hydrogels for bio-repair materials

    Science.gov (United States)

    Na, Yang Ho; Oh, Hwa Yeon; Ahn, Young Ju; Han, Youngbae

    2015-02-01

    Cartilage and meniscal lesions have limited potential for spontaneous repair. Consequently, much effort has been made to develop methods for repairing such lesions. Double-network (DN) gels are new candidate-materials for repairing such lesions. They exhibit exceptional mechanical strength and toughness in spite of their high water content. In this study, we prepared highly tough DN hydrogels and investigated the mechanical properties related to clinical implant use. The mechanical properties such as Young's modulus and suture tear-out strength were measured for the artificial replacement. The results suggest that the suture property of DN hydrogels can be adjusted by controlling the crosslinking density and monomer concentration. Finite element method was also applied to these DN hydrogels in order to check whether the fracture strength of the material is enough to meet a medical purpose.

  11. Duration-dependent effects of clinically relevant oral alendronate doses on cortical bone toughness in beagle dogs.

    Science.gov (United States)

    Burr, David B; Liu, Ziyue; Allen, Matthew R

    2015-02-01

    Bisphosphonates (BPs) have been shown to significantly reduce bone toughness in vertebrae within one year when given at clinical doses to dogs. Although BPs also reduce toughness in the cortical bone when given at high doses, their effect on cortical bone material properties when given at clinical doses is less clear. In part, this may be due to the use of small sample sizes that were powered to demonstrate differences in bone mineral density rather than the bone's material properties. Our lab has conducted several studies in which dogs were treated with alendronate at a clinically relevant dose. The goal of this study was to examine these published and unpublished data collectively to determine whether there is a significant time-dependent effect of alendronate on toughness of the cortical bone. This analysis seemed particularly relevant given the recent occurrence of atypical femoral fractures in humans. Differences in the toughness of ribs taken from dogs derived from five separate experiments were measured. The dogs were orally administered saline (CON, 1ml/kg/day) or alendronate (ALN) at a clinical dose (0.2mg/kg/day). Treatment duration ranged from 3months to 3years. Groups were compared using ANOVA, and time trends analyzed with linear regression analysis. Linear regressions of the percent difference in toughness between CON and ALN at each time point revealed a significant reduction in toughness with longer exposure to ALN. The downward trend was primarily driven by a downward trend in post-yield toughness, whereas toughness in the pre-yield region was not changed relative to CON. These data suggest that a longer duration of treatment with clinical doses of ALN results in deterioration of cortical bone toughness in a time-dependent manner. As the duration of treatment is lengthened, the cortical bone exhibits increasingly brittle behavior. This may be important in assessing the role that long-term BP treatments play in the risk of atypical fractures of the

  12. Structural Approaches on the Toughness in Double Network Hydrogels

    Science.gov (United States)

    Tominaga, Taiki; Osada, Yoshihito; Gong, Jian Ping

    Most hydrogels are mechanically too weak to be used as any load bearing devices. We have overcome this problem by synthesizing hydrogels with a double network (DN) structure. Despite the presence of 90% water in their composition, these tough gels exhibit a fracture stress of 170 kg/cm2, similar to that of cartilage. The relation between their mechanical strength and structure for a wide range of conditions should be analyzed to apprehend the origin of the toughness of the DN-gels. We recently reported some experi- mental results obtained by dynamic light scattering and small angle neutron scattering. Some new experimental results obtained by neutron scattering in both deformed and undeformed conditions provided for a new under- standing of the origin of toughness. We review the studies on the structure of DN-gels towards understanding of the toughness origin. Studies on DN-gels for biomedical applications are also described.

  13. 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.

  14. Specimen size effects on the tensile strength and fracture toughness

    International Nuclear Information System (INIS)

    Teran, J.; Gonzalez, J. L.; Hallen, J. M.; Martinez, M.

    2007-01-01

    In this work, an experimental research was conducted to determine size and orientation effects on tension and toughness properties through CTOD-R curves, using standard and miniature specimens taken from a structural steel plate.Compliance function estimation for the miniature size sample through load-displacement curves was considered. Experimental and statistical results showed that size and orientation affect tensioned toughness properties. The miniature tension test specimens showed strength values slightly greater than the standard ones but with less ductility. Miniature specimen CTOD-R curves showed sensibility to load changes and measurement method of crack aperture and crack length. Inconsistency in fracture toughness for specimen orientation longitudinal circumferential (LC) regarding size effect was also observed. Short orientations showed less strength and toughness than the other directions. (Author) 27 refs

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

    OpenAIRE

    MOHAMMED HAMDAN; SANDHYA TIWARI; SANDEEP TIWARI; RAKESH TOMAR

    2012-01-01

    AbstractMental toughness is an attribute that is often associated with successful performance in competitions. Mental toughness and its importance in competitive Sports have been documented in literature (A.S. Goldberg, 1998; K. Hodge, 1994; J. Tunney, 1987; R.M. Williams, 1988). In sports, many things are left to chance as, sports are predictably unpredictable. Sports persons who enter the competitive arena soon realize that there is more to competition than simply learning the physical skil...

  16. Characterization of fracture toughness exhaustion in pig aorta.

    Science.gov (United States)

    Chu, Boby; Gaillard, Emmanuel; Mongrain, Rosaire; Reiter, Steven; Tardif, Jean-Claude

    2013-01-01

    Spontaneous rupture of the aorta (SRA) without aneurysm, dissection, inflammation or infection of the aortic wall can be of two types: traumatic and non-traumatic. SRA is most of the time a fatal event. Consequently, it is important to understand the conditions which lead to the aortic rupture, and, in the case of non-traumatic SRA, to predict the temporal likelihood of rupture. The present work incorporates the temporal aspect by examining the effects of fatigue on aortic wall properties, and adopts an energy approach, based on fracture toughness, to evaluate the aorta's resistance to rupture. Fracture toughness characterization is a destructive testing process and as a consequence cannot be implemented as a clinical tool. However, using concepts in damage mechanics, in theory, it should be possible to indirectly assess fracture toughness from other mechanical properties, such as aortic wall stiffness. Tissue samples from non-aneurysmal porcine aortas were fatigued and were subjected to both biaxial and guillotine tests to assess wall stiffness variations and fracture toughness exhaustion, respectively. The experiments reveal that aortic wall stiffness variations and fracture toughness exhaustion decreased as a function of loading cycles and can be modeled with exponential functions. After one million loading cycles, the stiffness ratio between the non-fatigued sample and the fatigued sample, dropped to about 0.85, while the fracture toughness ratio counterpart fell to about 0.80. Consequently, the changes in both stiffness and fracture toughness as a function of applied fatigue cycles can be measured in aortic tissues. Moreover, these results suggest the possibility to use fracture toughness exhaustion curves as a fatigue criterion. Copyright © 2012 Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

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

    2018-03-07

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

  18. 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.

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

    International Nuclear Information System (INIS)

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

    1994-01-01

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

  20. Fracture toughness of steel--aluminum deformation welds

    International Nuclear Information System (INIS)

    Albright, C.E.

    1978-11-01

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

  1. On the possibility of estimating the fracture toughness of enamel.

    Science.gov (United States)

    Garrido, Miguel Ángel; Giráldez, Isabel; Ceballos, Laura; Rodríguez, Jesús

    2014-11-01

    There are many works that have attempted to estimate the fracture toughness of enamel by indentation techniques using equations whose success in determining the actual value of fracture toughness, rely on a particular three-dimensional pattern consisting of cracks growing from the edges of the indentation. Recently, an alternative methodology based on an energetic approach has been developed to estimate the fracture toughness of coatings by depth sensing indentation that is not less affected by the cracks pattern generated. In this work, the energetic approach to indentation fracture toughness of bovine enamel is presented and compared with those toughness values obtained using the traditional expressions reported in the literature. Indentation tests were carried out using a diamond Berkovich indenter onto the enamel surface of eight incisors from bovines of two years old. A continuous stiffness measurement methodology was used with a frequency of 45 Hz and displacement amplitude of 2 nm up to a maximum penetration depth of 2000 nm. The results showed that some modifications in the energetic methodology should be performed in order to apply it successfully. The fracture toughness values obtained using the traditional equation and applying the energetic methodology, were significantly different, although the values were within the range obtained by other authors. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  2. 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.

  3. The fracture toughness and DBTT of MoB particle-reinforced MoSi2 composites

    International Nuclear Information System (INIS)

    Xiong Zhi; Wang Gang; Jiang Wan

    2005-01-01

    The room temperature fracture toughness and the high temperature DBTT of MoB particle-reinforced MoSi 2 composites were investigated using Vickers indentation technique and MSP testing method, respectively. Modified small punch (MSP) test is a method for evaluation of mechanical properties using very small specimens, and it's appropriate for the determination of strength and DBTT. It was found that the approximate fracture toughness of the composite is 1.3 times that of monolithic MoSi 2 , and its DBTT is 100 C higher than that of monolithic MoSi 2 materials. Cracks deflection is a probable mechanism responsible for this behavior. (orig.)

  4. 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.

  5. 2016 Accomplishments. Tritium aging studies on stainless steel. Forging process effects on the fracture toughness properties of tritium-precharged stainless steel

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-01-01

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

  6. Flexural Toughness Properties of Reinforced Steel Fibre Incorporated Alkali Activated Slag Concrete

    Directory of Open Access Journals (Sweden)

    Srinivasan Karunanithi

    2014-01-01

    Full Text Available The influence of steel fibre addition on the flexural properties of geopolymer based cementitious matrix was investigated in the present study. Slag based geopolymer mixtures were prepared with different binder and aggregate combinations. Strength gain and hardened properties of different geopolymer concrete mixtures were evaluated using accelerated curing techniques subjected to hot air oven and steam curing. Further, the steel fibre additions on the mechanical strength properties of a high strength geopolymer mixture were studied. A comprehensive evaluation on the post-crack toughness properties was assessed using four-point bend test. Test results exhibited that a geopolymer concrete of maximum compressive strength of 56.6 MPa can be achieved with steam curing. Experimental observations also demonstrated that the steel fibre inclusions in geopolymer concrete provided adequate improvement on post-crack toughness properties and showed higher composite performance with increased volume fraction of steel fibres.

  7. 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.

  8. 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.

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

    Science.gov (United States)

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

    2018-03-01

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

  10. 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

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

    Science.gov (United States)

    Byun, Thak Sang; Hoelzer, David T.; Kim, Jeoung Han; Maloy, Stuart A.

    2017-02-01

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

  12. 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...

  13. Goal Profiles, Mental Toughness and its Influence on Performance Outcomes among Wushu Athletes.

    Science.gov (United States)

    Kuan, Garry; Roy, Jolly

    2007-01-01

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

  14. Strain rate influence on human cortical bone toughness: A comparative study of four paired anatomical sites.

    Science.gov (United States)

    Gauthier, Rémy; Follet, Hélène; Langer, Max; Meille, Sylvain; Chevalier, Jérôme; Rongiéras, Frédéric; Peyrin, Françoise; Mitton, David

    2017-07-01

    Bone fracture is a major health issue worldwide and consequently there have been extensive investigations into the fracture behavior of human cortical bone. However, the fracture properties of human cortical bone under fall-like loading conditions remains poorly documented. Further, most published research has been performed on femoral diaphyseal bone, whereas it is known that the femoral neck and the radius are the most vulnerable sites to fracture. Hence, the aim of this study is to provide information on human cortical bone fracture behavior by comparing different anatomical sites including the radius and the femoral neck acquired from 32 elderly subjects (50 - 98 y.o.). In order to investigate the intrinsic fracture behavior of human cortical bone, toughness experiments were performed at two different strain rates: standard quasi-static conditions, and a higher strain rate representative of a fall from a standing position. The tests were performed on paired femoral neck, femoral, tibial and radius diaphyseal samples. Linear elastic fracture toughness and the non-linear J-integral method were used to take into account both the elastic and non-elastic behavior of cortical bone. Under quasi-static conditions, the radius presents a significantly higher toughness than the other sites. At the higher strain rate, all sites showed a significantly lower toughness. Also, at the high strain rate, there is no significant difference in fracture properties between the four anatomical sites. These results suggest that regardless of the anatomical site (femur, femoral neck, tibia and radius), the bone has the same fracture properties under fall loading conditions. This should be considered in biomechanical models under fall-like loading conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Modification of TOUGH2 to Include the Dusty Gas Model for Gas Diffusion; TOPICAL

    International Nuclear Information System (INIS)

    WEBB, STEPHEN W.

    2001-01-01

    The GEO-SEQ Project is investigating methods for geological sequestration of CO(sub 2). This project, which is directed by LBNL and includes a number of other industrial, university, and national laboratory partners, is evaluating computer simulation methods including TOUGH2 for this problem. The TOUGH2 code, which is a widely used code for flow and transport in porous and fractured media, includes simplified methods for gas diffusion based on a direct application of Fick's law. As shown by Webb (1998) and others, the Dusty Gas Model (DGM) is better than Fick's Law for modeling gas-phase diffusion in porous media. In order to improve gas-phase diffusion modeling for the GEO-SEQ Project, the EOS7R module in the TOUGH2 code has been modified to include the Dusty Gas Model as documented in this report. In addition, the liquid diffusion model has been changed from a mass-based formulation to a mole-based model. Modifications for separate and coupled diffusion in the gas and liquid phases have also been completed. The results from the DGM are compared to the Fick's law behavior for TCE and PCE diffusion across a capillary fringe. The differences are small due to the relatively high permeability (k= 10(sup -11) m(sup 2)) of the problem and the small mole fraction of the gases. Additional comparisons for lower permeabilities and higher mole fractions may be useful

  16. Response of mode II interlaminar fracture toughness of composite laminates with carbon nanotubes interlayer

    Science.gov (United States)

    Liu, L.; Liang, Y. M.; Xu, G. Y.

    2007-07-01

    Aggregation is usually unavoidable for the carbon nanotubes due to the high surface free energy. In this paper, an attempt was carried out to investigate the effects of the nanotube's films as ply interfaces on the mode II interlaminar fracture toughness. The nanotubes were distributed into absolute ethyl alcohol solvent and acted as core solutions. A polymer, Poly(methylmethacrylate)(PMMA), was dissolved in solvent and acted as shell solutions. Then, the core and shell solutions were electrospun into compound nanofibers by use of a co-axial electrospinning to obtain a second distribution for the carbon nanotubes. The compound nanofibers were collected as thin films in a reasonable thickness and were inserted into the middle interface of a composite laminate. For comparison, the core solutions were sprayed directly onto the surface of the middle ply of the preformed laminates. End notched flexure (ENF) test was applied to investigate the effect of the nanotubes in different forms on the interlaminar fracture toughness of the cured laminates. Scanning electronic microscope (SEM) was used to analyze the fracture mechanics of the ENF specimens. Testing results have shown that the nanotubes have significant reinforcement effect on the interlaminar fracture toughness for those studied cases in this research. SEM analysis of the fracture surface of the ENF specimens has indicated that the polymer nanofibers and nanotubes have a good consistency with the matrix resin of the laminates.

  17. 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...

  18. WinGridder - An interactive grid generator for TOUGH - A user's manual (Version 1.0)

    International Nuclear Information System (INIS)

    Pan, Lehua; Hinds, Jennifer; Haukwa, Charles; Wu, Yu-Shu; Bodvarsson, Gudmundur

    2001-01-01

    WinGridder is a Windows-based software package for designing, generating, and visualizing at various spatial scales numerical grids used in reservoir simulations and groundwater modeling studies. Development of this software was motivated by the requirements of the TOUGH (Transport of Unsaturated Groundwater and Heat) family of codes (Pruess 1987, 1991) for simulating subsurface processes related to high-level nuclear waste isolation in partially saturated geological media. Although the TOUGH family of codes has great flexibility in handling the variety of grid information required to describe complex objects, designing and generating a suitable irregular grid can be a tedious and error-prone process, even with the help of existing grid generating programs. This is especially true when the number of cells and connections is very large. The processes of inspecting the quality of the grid or extracting sub-grids or other specific grid information are also complex. The mesh maker embedded within TOUGH2 generates only uniform numerical grids and handles only one set of uniform fracture and matrix properties throughout the model domain. This is not suitable for grid generation in complex flow and transport simulations (such as those of Yucca Mountain, which have heterogeneity in both fracture and matrix media). As a result, the software program Amesh (Haukwa 2000) was developed to generate irregular, effective-continuum (ECM) grids

  19. 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

  20. 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.

  1. An evaluation of fracture toughness of bituminous coal

    International Nuclear Information System (INIS)

    Pathan, A.G.

    2005-01-01

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

  2. Interfacial fracture toughness of aged adhesive-dentin interfaces.

    Science.gov (United States)

    De Munck, Jan; Poitevin, André; Lührs, Anne-Katrin; Pongprueksa, Pong; Van Ende, Annelies; Van Landuyt, Kirsten L; Van Meerbeek, Bart

    2015-04-01

    To assess interfacial fracture toughness of different adhesive approaches and compare to a standard micro-tensile bond-strength (μTBS) test after 6 months water storage. Chevron-notched beam fracture toughness (CNB) was determined using a modified ISO 24370:2005 standard. Adhesive-dentin micro-specimens (1.0 mm × 1.0 mm × 8-10 mm) were stressed in tensile until failure to determine the micro-tensile bond strength (μTBS). The highest mean μTBS and interfacial fracture toughness were measured for the multi-step adhesives Clearfil SE Bond (Kuraray Noritake) and OptiBond FL (Kerr). While large differences were observed in the bond strength values (from 7.4 to 27.2 MPa) of the one-step self-etch adhesives tested, interfacial fracture toughness was less different (from 0.7 to 1.0 MPam(1/2)). The adhesive with the lowest mean toughness (All-bond Universal, Bisco) had however the highest Weibull reliability, which might be a better parameter in regard to more consistent clinical performance. The self-adhesive composite Vertise Flow (Kerr) scored significantly lower at all levels. Although the ranking of the adhesives tested using CNB and μTBS corresponded well, the outcome of CNB appeared more reliable and less variable. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  3. Adolescents with greater mental toughness show higher sleep efficiency, more deep sleep and fewer awakenings after sleep onset.

    Science.gov (United States)

    Brand, Serge; Gerber, Markus; Kalak, Nadeem; Kirov, Roumen; Lemola, Sakari; Clough, Peter J; Pühse, Uwe; Holsboer-Trachsler, Edith

    2014-01-01

    Mental toughness (MT) is understood as the display of confidence, commitment, challenge, and control. Mental toughness is associated with resilience against stress. However, research has not yet focused on the relation between MT and objective sleep. The aim of the present study was therefore to explore the extent to which greater MT is associated with objectively assessed sleep among adolescents. A total of 92 adolescents (35% females; mean age, 18.92 years) completed the Mental Toughness Questionnaire. Participants were split into groups of high and low mental toughness. Objective sleep was recorded via sleep electroencephalograms and subjective sleep was assessed via a questionnaire. Compared with participants with low MT, participants with high MT had higher sleep efficiency, a lower number of awakenings after sleep onset, less light sleep, and more deep sleep. They also reported lower daytime sleepiness. Adolescents reporting higher MT also had objectively better sleep, as recorded via sleep electroencephalograms. A bidirectional association between MT and sleep seems likely; therefore, among adolescence, improving sleep should increase MT, and improving MT should increase sleep. Copyright © 2014 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.

  4. Fracture-tough, corrosion-resistant bearing steels

    Science.gov (United States)

    Olson, Gregory B.

    1990-01-01

    The fundamental principles allowing design of stainless bearing steels with enhanced toughness and stress corrosion resistance has involved both investigation of basic phenomena in model alloys and evaluation of a prototype bearing steel based on a conceptual design exercise. Progress in model studies has included a scanning Auger microprobe (SAM) study of the kinetics of interfacial segregation of embrittling impurities which compete with the kinetics of alloy carbide precipitation in secondary hardening steels. These results can define minimum allowable carbide precipitation rates and/or maximum allowable free impurity contents in these ultrahigh strength steels. Characterization of the prototype bearing steel designed to combine precipitated austenite transformation toughening with secondary hardening shows good agreement between predicted and observed solution treatment response including the nature of the high temperature carbides. An approximate equilibrium constraint applied in the preliminary design calculations to maintain a high martensitic temperature proved inadequate, and the solution treated alloy remained fully austenitic down to liquid nitrogen temperature rather than transforming above 200 C. The alloy can be martensitically transformed by cryogenic deformation, and material so processed will be studied further to test predicted carbide and austenite precipitation behavior. A mechanistically-based martensitic kinetic model was developed and parameters are being evaluated from available kinetic data to allow precise control of martensitic temperatures of high alloy steels in future designs. Preliminary calculations incorporating the prototype stability results suggest that the transformation-toughened secondary-hardening martensitic-stainless design concept is still viable, but may require lowering Cr content to 9 wt. pct. and adding 0.5 to 1.0 wt. pct. Al. An alternative design approach based on strain-induced martensitic transformation during

  5. Influence of texture on fracture toughness of zircaloy cladding

    International Nuclear Information System (INIS)

    Grigoriev, V.; Andersson, Stefan

    1997-06-01

    The correlation between texture and fracture toughness of Zircaloy 2 cladding has been investigated in connection with axial cracks in fuel rods. The texture of the cladding determines the anisotropy of plasticity of the cladding which, in turn, should influence the strain conditions at the crack-tip. Plastic strains in the cladding under uniaxial tension were characterised by means of the anisotropy constants F, G and H calculated according to Hill's theory. Test temperatures between 20 and 300 deg C do not influence the F, G and H values. Any significant effect of hydrogen (about 500 wtppm) on the anisotropy constants F, G and H has not been revealed at a test temperature of 300 deg C. The results, obtained for stress-relieved and recrystallized cladding with different texture, show an obvious influence of texture on the fracture toughness of Zircaloy cladding. A higher fracture toughness has been found for cladding with more radial texture

  6. Fracture toughness of borides formed on boronized ductile iron

    International Nuclear Information System (INIS)

    Sen, Ugur; Sen, Saduman; Koksal, Sakip; Yilmaz, Fevzi

    2005-01-01

    In this study, fracture toughness properties of boronized ductile iron were investigated. Boronizing was realized in a salt bath consisting of borax, boric acid and ferro-silicon. Boronizing heat treatment was carried out between 850 and 950 deg. C under the atmospheric pressure for 2-8 h. Borides e.g. FeB, Fe 2 B formed on ductile iron was verified by X-ray diffraction (XRD) analysis, SEM and optical microscope. Experimental results revealed that longer boronizing time resulted in thicker boride layers. Optical microscope cross-sectional observation of borided layers showed dentricular morphology. Both microhardness and fracture toughness of borided surfaces were measured via Vickers indenter. The harnesses of borides formed on the ductile iron were in the range of 1160-2140 HV 0.1 and fracture toughness were in the range of 2.19-4.47 MPa m 1/2 depending on boronizing time and temperature

  7. 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.

  8. The crack layer approach to toughness characterization in steel

    Science.gov (United States)

    Bessendorff, M.; Chudnovsky, A.

    1986-01-01

    In a study of the laws of crack propagation and toughness characterization, it is feasible to employ two alternative approaches, including the fracture mechanics approach and the material science approach. The crack layer (CL) theory discussed by Khandogin and Chudnovsky (1978) and Chudnovsky (1980) considers the crack together with the surrounding defects as one system which has several degrees of freedom. It is pointed out that the CL theory defines the relationship between the parameters of fracture mechanics and the characteristics of microstructural changes which are the subject of material science. Experiments are described, taking into account a toughness characterization test and microscopic studies. Attention is given to a phenomenological study of toughness characterization, the morphology of crack layer, and the evaluation of energy stored in the dislocation network.

  9. Crack arrest toughness measurements with A533B steel

    International Nuclear Information System (INIS)

    Salonen, Seppo.

    1979-11-01

    This work covers crack arrest toughness measurements on A533B steel done at the Technical Research Centre of Finland. These measurements are one part of a multinational effort, involving 30 laboratories. The aim of the cooperative test program is to examine two test procedures for measuring the crack arrest toughness, to give information about their reproducibility, and to identify the factors affecting the interpretation. The principles given for the testing were easy to apply in general and the results were satisfactory. Some factors in the test runs and in the specimen's behaviour are indicated which can cause error in the results or make implementation of the test more difficult. By comparing the results from our laboratory with average values from the test program a good agreement can be seen. Crack arrest toughness values derived from the compared procedures with a static analysis agree closely, but values calculated using a dynamic analysis differ considerably. (author)

  10. 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.

  11. 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

  12. Mental toughness and behavioural perseverance: A conceptual replication and extension.

    Science.gov (United States)

    Giles, Brandon; Goods, Paul S R; Warner, Dylan R; Quain, Dale; Peeling, Peter; Ducker, Kagan J; Dawson, Brian; Gucciardi, Daniel F

    2017-11-08

    The purpose of this study was to conduct a conceptual replication of the proposition that mental toughness is associated positively with behavioural perseverance. Repeated-measures design. In total, 38 male Australian rules footballers took part in this study (age, 21±3 y; mass, 82.7±11.0kg; height, 1.84±.07m; football experience, 13±4 y). Participants self-reported mental toughness approximately one week prior to their first testing session where we assessed their aerobic capacity via the measurement of peak oxygen consumption (V˙O 2peak ). Approximately one week later, participants completed a 20m shuttle run test (MST). The final testing session took place approximately one week later, where participants completed a simulated team game circuit (STGC; 60min) to simulate game-relevant level of fatigue, which was followed immediately by a 20m MST. Mental toughness was a salient determinant of the variation in behavioural perseverance under typical circumstances, when prior knowledge from past research was incorporated directly into the estimation process. However, the positive association between mental toughness and behavioural perseverance did not generalise to a performance context in which participants were fatigued. The results of the current study suggest that mental toughness represents a salient psychological correlate of behavioural perseverance in a discrete physical task that taxes the aerobic energy system in some but not all situations. When fatigued, the effect of mental toughness is outweighed by greater underlying fitness. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  13. 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.

  14. High-Strength Ultra-Fine-Grained Hypereutectic Al-Si-Fe-X (X = Cr, Mn) Alloys Prepared by Short-Term Mechanical Alloying and Spark Plasma Sintering.

    Science.gov (United States)

    Průša, Filip; Bláhová, Markéta; Vojtěch, Dalibor; Kučera, Vojtěch; Bernatiková, Adriana; Kubatík, Tomáš František; Michalcová, Alena

    2016-11-30

    In this work, Al-20Si-10Fe-6Cr and Al-20Si-10Fe-6Mn (wt %) alloys were prepared by a combination of short-term mechanical alloying and spark plasma sintering. The microstructure was composed of homogeneously dispersed intermetallic particles forming composite-like structures. X-ray diffraction analysis and TEM + EDS analysis determined that the α-Al along with α-Al 15 (Fe,Cr)₃Si₂ or α-Al 15 (Fe,Mn)₃Si₂ phases were present, with dimensions below 130 nm. The highest hardness of 380 ± 7 HV5 was observed for the Al-20Si-10Fe-6Mn alloy, exceeding the hardness of the reference as-cast Al-12Si-1Cu-1 Mg-1Ni alloy (121 ± 2 HV5) by nearly a factor of three. Both of the prepared alloys showed exceptional thermal stability with the hardness remaining almost the same even after 100 h of annealing at 400 °C. Additionally, the compressive strengths of the Al-20Si-10Fe-6Cr and Al-20Si-10Fe-6Mn alloys reached 869 MPa and 887 MPa, respectively, and had virtually the same values of 870 MPa and 865 MPa, respectively, even after 100 h of annealing. More importantly, the alloys showed an increase in ductility at 400 °C, reaching several tens of percent. Thus, both of the investigated alloys showed better mechanical properties, including superior hardness, compressive strength and thermal stability, as compared to the reference Al-10Si-1Cu-1Mg-1Ni alloy, which softened remarkably, reducing its hardness by almost 50% to 63 ± 8 HV5.

  15. 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...

  16. Design of 3D scaffolds for tissue engineering testing a tough polylactide-based graft copolymer

    International Nuclear Information System (INIS)

    Dorati, R.; Colonna, C.; Tomasi, C.; Genta, I.; Bruni, G.; Conti, B.

    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

  17. 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

  18. Influence of Ultrasonic Melt Treatment and Cooling Rates on the Microstructural Development and Elevated Temperature Mechanical Properties of a Hypereutectic Al-18Si-4Cu-3Ni Piston Alloy

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Jea-Hee; Cho, Young-Hee; Jung, Jae-Gil; Lee, Jung-Moo [Korea Institute of Materials Science (KIMS), Changwon (Korea, Republic of); Park, Ik Min [Pusan National University, Busan (Korea, Republic of)

    2017-06-15

    The influence of ultrasonic melt treatment (UST) combined with a change in cooling rates on the microstructure and elevated temperature mechanical properties of a hypereutectic Al-18Si-4Cu-3Ni piston alloy was investigated. Microstructural observation confirmed that UST effectively refined the sizes of primary Si and intermetallic compounds (e.g. ε-Al{sub 3}Ni) while promoting their homogeneous distribution. Besides the refinement of the constituent phases, the size of the dendrite arm spacing (DAS), which was hardly affected by UST, significantly deceased with increasing cooling rates. The refinement of the solidification structure in the alloy achieved through both UST and increased cooling rates resulted in an improvement in tensile properties, ultimate tensile strength and elongation in particular, after T5 heat treatment followed by overaging at 350 ℃. However, the elevated temperature yield strength of the alloy was not associated with the refinement, but was rather correlated with the 3-D interconnectivity, morphology and volume fraction of the primary Si.

  19. Tough Times Ahead for Government Labs

    International Nuclear Information System (INIS)

    Ban, Stephen; Buchanan, Michelle V.; Cheeks, Nona; Funsten, Herbert; Hawsey, Robert; Lane, Monya; Whitlow, Woodrow Jr.; Studt, Tim

    2008-01-01

    Many government R and D laboratory executives face a tough couple of months ahead. These anxieties are fueled by (1) possible management, technical direction, and budgetary changes in their agencies due to changes in the federal administration; (2) frozen operating budgets until March 2009 due to the Continuing Resolution (CR) attachment to the recent banking bailout bill; and (3) the financial fallout from the economic downturn. These and other pertinent questions regarding their R and D operations were addressed in R and D Magazine's 9th Annual Government R and D Executive Roundtable held on Oct. 16, 2008, in conjunction with the 46th Annual R and D 100 Awards at Chicago's Navy Pier. Most members of this year's government executive panel were hesitant to speculate on the changes that might occur in their labs as a result of the new administration. The exception to this stand was the National Renewable Energy Laboratory's (NREL's) Robert Hawsey. ''No matter who wins (the Roundtable was held before the Nov. 4th Presidential election), we expect to see continued support,'' says Hawsey. ''All of our cooperative research facilities are over-subscribed and we're looking at how we can expand them.'' Obviously, renewable energy is a hot button in the administration and likely to get increased financial backing to help meet our country's energy independence goals. When pressed, the panel was mostly optimistic about their future support, stating that external threats to the U.S. have not changed, and research work associated with homeland security and national defense is unlikely to see drastic change. ''We have a strong portfolio in life science and don't expect any changes,'' says Oak Ridge National Laboratory's (ORNL's) Michelle Buchanan. Ongoing federally funded work at the national labs that was started before the Oct. 1st start of the FY2009 fiscal year will continue without any changes - those funds are unaffected by the CR action. This applies as well to any

  20. 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.

  1. Shape and size of methane bubbles in muddy aquatic sediments and their dependence on sediment fracture toughness: a modeling approach

    Science.gov (United States)

    Katsman, Regina

    2014-05-01

    Shallow gassy marine sediments abundantly found on continental margins of Israel and worldwide, are a source of a major concern for their contribution to the destabilization of coastal and marine infrastructure, air pollution, and global warming. Bubbles are different in the different sediment types. Size of the bubbles residing in the fine-grained muddy sediment exceeds significantly the grain size of sediment, and its shape can be approximated by a large oblate spheroid surrounded by sediment saturated with water. Experimental results indicate that bubble growth is accompanied by fracturing of the fine-grained muddy sediment. Modeling reveals that fracture toughness of the muddy sediments significantly affects bubble shape and size evolution prior its ascent. Small fracture toughness is responsible for generation of the small bubbles with highly asymmetric configuration and with fracturing concentrated mostly on the bubble head. In contrast, bigger fracture toughness is responsible for generation of the large, more symmetric bubbles. Moreover, growing bubble demonstrates a positive allometry resulting in a bigger rate of growth of its surface area that is responsible for the effectiveness of the solute supply from pore water to the bubble interior. This scaling demonstrates a strong correlation with sediment fracture toughness as well. Cross-section of the buoyant bubbles evolves from the elliptic profile to the one resembling an 'inverted tear drop'. Calculated bubbles characteristics in different sediments types demonstrate a good agreement with values reported in the literature.

  2. Factors Affecting Leaf Selection by Foregut-fermenting Proboscis Monkeys: New Insight from in vitro Digestibility and Toughness of Leaves

    Science.gov (United States)

    Matsuda, Ikki; Clauss, Marcus; Tuuga, Augustine; Sugau, John; Hanya, Goro; Yumoto, Takakazu; Bernard, Henry; Hummel, Jürgen

    2017-01-01

    Free-living animals must make dietary choices in terms of chemical and physical properties, depending on their digestive physiology and availability of food resources. Here we comprehensively evaluated the dietary choices of proboscis monkeys (Nasalis larvatus) consuming young leaves. We analysed the data for leaf toughness and digestibility measured by an in vitro gas production method, in addition to previously reported data on nutrient composition. Leaf toughness, in general, negatively correlated with the crude protein content, one of the most important nutritional factors affecting food selection by leaf-eating primates. This result suggests that leaf toughness assessed by oral sensation might be a proximate cue for its protein content. We confirmed the importance of the leaf chemical properties in terms of preference shown by N. larvatus; leaves with high protein content and low neutral detergent fibre levels were preferred to those of the common plant species. We also found that these preferred leaves were less tough and more digestible than the alternatives. Our in vitro results also suggested that N. larvatus were little affected by secondary plant compounds. However, the spatial distribution pattern of plant species was the strongest factor explaining the selection of the preferred leaf species. PMID:28211530

  3. A review and conceptual re-examination of mental toughness: implications for future researchers

    OpenAIRE

    Crust, Lee

    2008-01-01

    This paper provides a review of mental toughness research and examines the major conceptual concerns that are evident in current mental toughness literature. Despite more rigorous scientific approaches to the study of mental toughness, a number of limitations are apparent: these include the assumption that elite or super elite performers are mentally tough (failure to provide objective measures), focusing research solely on elite or super elite performers, appearing to conceptualise mental to...

  4. 46 CFR 54.05-17 - Weld toughness test acceptance criteria.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Weld toughness test acceptance criteria. 54.05-17 Section 54.05-17 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PRESSURE VESSELS Toughness Tests § 54.05-17 Weld toughness test acceptance criteria. (a) For Charpy V-notch...

  5. 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...

  6. Hydrogen Assisted Cracking of High Strength Alloys

    National Research Council Canada - National Science Library

    Gangloff, Richard P

    2003-01-01

    ... (Irwin and Wells, 1997; Paris, 1998). Second, materials scientists developed metals with outstanding balances of high tensile strength and high fracture toughness (Garrison, 1990; Wells, 1993; Boyer, 1993...

  7. Impact Toughness of Ultrafine-Grained Interstitial-Free Steel

    Science.gov (United States)

    Saray, Onur; Purcek, Gencaga; Karaman, Ibrahim; Maier, Hans J.

    2012-11-01

    Impact toughness of an ultrafine-grained (UFG) interstitial-free (IF) steel produced by equal-channel angular extrusion/pressing (ECAE/P) at room temperature was investigated using Charpy impact tests. The UFG IF steel shows an improved combination of strength and impact toughness compared with the corresponding coarse-grained (CG) one. The CG IF steel samples underwent a transition in fracture toughness values with decreasing temperature because of a sudden change in fracture mode from microvoid coalescence (ductile) to cleavage (brittle) fracture. Grain refinement down to the submicron (≈320 nm) levels increased the impact energies in the upper shelf and lower shelf regions, and it considerably decreased the ductile-to-brittle transition temperature (DBTT) from 233 K (-40 °C) for the CG steel to approximately 183 K (-90 °C) for the UFG steel. Also, the sudden drop in DBTT with a small transition range for the CG sample changed to a more gradual decrease in energy for the UFG sample. The improvement in toughness after UFG formation was attributed to the combined effects of grain refinement and delamination and/or separation in the heavily deformed microstructure. Although an obvious change from the ductile fracture by dimples to the brittle fracture by cleavage was recognized at 233 K (-40 °C) for the CG steel, no fully brittle fracture occurred even at 103 K (-170 °C) in the UFG steel.

  8. Prediction of fracture toughness temperature dependence applying neural network

    Czech Academy of Sciences Publication Activity Database

    Dlouhý, Ivo; Hadraba, Hynek; Chlup, Zdeněk; Šmída, T.

    2011-01-01

    Roč. 11, č. 1 (2011), s. 9-14 ISSN 1451-3749 R&D Projects: GA ČR(CZ) GAP108/10/0466 Institutional research plan: CEZ:AV0Z20410507 Keywords : brittle to ductile transition * fracture toughness * artificial neural network * steels Subject RIV: JL - Materials Fatigue, Friction Mechanics

  9. 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.

  10. Effect of thermal aging on fracture toughness of RPV steel

    International Nuclear Information System (INIS)

    Fukakura, Juichi; Ishikawa, Masaaki

    1993-01-01

    The effect of thermal aging on mechanical properties and fracture toughness was investigated on pressure vessel steel of light water reactors. Submerged arc welded plates of ASME SA508 C1.3 steel were isothermally aged at 350 C, 400 C and 450 C for up to 10,000 hrs. Tensile, Charpy impact and fracture toughness testings were conducted on the base metal and the weld heat affected zone (HAZ) material to evaluate whether thermal aging induced by the plant operation is critical for the integrity of the pressure vessel or not. Tensile properties of the base metal was not changed by thermal aging as far as the thermal aging conditions were concerned. Relatively distinct degradation was observed in fracture toughness and J-resistance properties of both the base metal and the weld HAZ material, while only slight changes were observed in Charpy impact properties for both of them. However, it was concluded that the effect of thermal aging estimated by 40-80 years of plant operation on fracture toughness of both materials is small. (orig.)

  11. Understanding and Supporting Adolescents' Mental Toughness in an Education Context

    Science.gov (United States)

    McGeown, Sarah; Putwain, Dave; St. Clair-Thompson, Helen; Clough, Peter

    2017-01-01

    This study sought to explore the concept of mental toughness (comprising the attributes challenge, commitment, control, and confidence) from the perceptions of adolescents, to better understand their views on these attributes and the extent to which each were regarded as important within an educational setting. In total, 54 adolescents (31 female)…

  12. 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.

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

    International Nuclear Information System (INIS)

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

    2001-01-01

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

  14. 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.

  15. Importance of tubule density to the fracture toughness of dentin.

    Science.gov (United States)

    Montoya, C; Arola, D; Ossa, E A

    2016-07-01

    The fracture toughness of dentin is critical to the prevention of tooth fracture. Within the tooth crown, the mechanical properties of dentin are influenced by spatial variations in the density and diameter of the dentin tubules with distance from the pulp. There are also relevant changes to the microstructure of dentin with age. In this investigation the importance of tubule density to the fracture toughness of dentin was evaluated in "young" and "old" age groups. The variations in microstructure (density and diameter of tubules) from young and old donor teeth were studied by means of optical microscopy. A reduction in the density and diameter of tubules was identified to occur with aging. An approach previously proposed to study the mechanical behavior of porous materials was used to model the fracture toughness of coronal dentin in terms of the tubule characteristics. Results were then compared with published results from previous studies. The model predictions were consistent with experimental results for the fracture toughness of dentin from young donor teeth, but overestimated the values that have been reported for "old" dentin. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Jury Toughness: The Impact of Conservatism on Criminal Court Verdicts.

    Science.gov (United States)

    Levine, James P.

    1983-01-01

    Compared criminal court verdicts after trials with and without juries. A study of 58,336 trials of persons charged with felonies showed that juries convict substantially more often than judges trying cases alone. Jury toughness is seen as a response to the growth of popular conservatism on criminal justice issues. (JAC)

  17. Experimental fracture toughness characterization using the modified TSD specimen

    DEFF Research Database (Denmark)

    Berggreen, Christian; Quispitupa, Amilcar; Alonso, Jose L.

    2010-01-01

    The modified Tilted Sandwich Debond (TSD) specimen provides an improved methodology for characterization of the face/core fracture resistance. An experimental mixed mode characterization of the fracture toughness spanning a large range of phase angles has been achieved by specific steel bar...

  18. 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

  19. Directionally Solidified NiAl-Based Alloys Studied for Improved Elevated-Temperature Strength and Room-Temperature Fracture Toughness

    Science.gov (United States)

    Whittenberger, J. Daniel; Raj, Sai V.; Locci, Ivan E.; Salem, Jonathan A.

    2000-01-01

    Efforts are underway to replace superalloys used in the hot sections of gas turbine engines with materials possessing better mechanical and physical properties. Alloys based on the intermetallic NiAl have demonstrated potential; however, they generally suffer from low fracture resistance (toughness) at room temperature and from poor strength at elevated temperatures. Directional solidification of NiAl alloyed with both Cr and Mo has yielded materials with useful toughness and elevated-temperature strength values. The intermetallic alloy NiAl has been proposed as an advanced material to extend the maximum operational temperature of gas turbine engines by several hundred degrees centigrade. This intermetallic alloy displays a lower density (approximately 30-percent less) and a higher thermal conductivity (4 to 8 times greater) than conventional superalloys as well as good high-temperature oxidation resistance. Unfortunately, unalloyed NiAl has poor elevated temperature strength (approximately 50 MPa at 1027 C) and low room-temperature fracture toughness (about 5 MPa). Directionally solidified NiAl eutectic alloys are known to possess a combination of high elevated-temperature strength and good room-temperature fracture toughness. Research has demonstrated that a NiAl matrix containing a uniform distribution of very thin Cr plates alloyed with Mo possessed both increased fracture toughness and elevated-temperature creep strength. Although attractive properties were obtained, these alloys were formed at low growth rates (greater than 19 mm/hr), which are considered to be economically unviable. Hence, an investigation was warranted of the strength and toughness behavior of NiAl-(Cr,Mo) directionally solidified at faster growth rates. If the mechanical properties did not deteriorate with increased growth rates, directional solidification could offer an economical means to produce NiAl-based alloys commercially for gas turbine engines. An investigation at the NASA Glenn

  20. Effects of austempering heat treatment conditions on fracture toughness of austempered ductile cast iron; Kyujo kokuen chutetsu no hakai jinsei ni oyobosu austemper shori no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Sugiyama, Y.; Arai, M. [Musashi Institute of Technology, Tokyo (Japan)

    1996-03-25

    Discussions were given in various manners to learn effects of treatment conditions with respect to fracture toughness of austempered ductile cast iron. Austenitizing temperature and isothermal transforming conditions that result in comprehensively most excellent fracture toughness including tensile strength were 1173 K and 648 K - 3.6 ks, respectively. The austenitizing temperature as low as 1123 K reduces quantity of residual austenite, resulting in residual inclusion of free ferrite in the structure. If as high as 1223 K, reduction in the fracture toughness is caused under any condition as a result of increase in unstable austenite and growth of austenite into coarse particles. With respect to the isothermal transforming conditions, high fracture toughness may be achieved at a relatively high temperature. However, a structure that has been transformed from austenite to bainite causes a secondary reaction in a short time, and deposits particulates of cementite and graphite, leading to a prediction of decrease in the fracture toughness. Therefore, it is preferable that the treatment time is decreased in order to suppress the secondary reaction. 9 refs., 10 figs., 7 tabs.

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

    Directory of Open Access Journals (Sweden)

    MOHAMMED HAMDAN

    2012-06-01

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

  2. The role of Ti carbonitride precipitates on fusion zone strength-toughness in submerged arc welded linepipe joints

    Energy Technology Data Exchange (ETDEWEB)

    Aucott, L., E-mail: la126@le.ac.uk [Department of Engineering, University of Leicester (United Kingdom); Wen, S.W., E-mail: shuwen.wen@tatasteel.com [Department of Engineering, University of Leicester (United Kingdom); Tata Steel, Swinden Technology Centre, Rotherham (United Kingdom); Dong, H., E-mail: hd38@le.ac.uk [Department of Engineering, University of Leicester (United Kingdom)

    2015-01-12

    The role of micro-alloying in the submerged arc welding (SAW) of high strength low alloy steel linepipe is paramount in facilitating the high strength properties of the linepipe. In this study, transmission electron microscopy analysis revealed the presence of large (0.85 µm) Ti (C,N) precipitates within the predominantly acicular ferrite SAW joint. Cross-weld Vickers hardness and Charpy impact tests revealed that the fusion zone has high hardness and low toughness properties in relation to the base metal and heat affected zone. Fractography observations made on the ductile fracture surface of the fusion zone revealed a high number of the large Ti (C,N) precipitates to be located within the microvoids – suggesting their role in nucleating microvoids. Finally, fracture micro-mechanics are used to evaluate the relationship between the coarse precipitates and reduced strength-toughness properties in the SAW weld of the API-5L grade X65 linepipe steel.

  3. Effects of tensile loading on upper shelf fracture toughness

    Energy Technology Data Exchange (ETDEWEB)

    Joyce, J.A. [Naval Academy, Annapolis, MD (United States); Link, R.E. [Naval Surface Warfare Center, Annapolis, MD (United States)

    1994-03-01

    Constraint has been an important consideration in fracture mechanics from the earliest work that was done to develop the 1974 version of the ASTM Standard E399. O`Dowd and Shih (1991) have proposed that the difference in crack tip stress fields can be quantified in terms of a field quantity that they have call Q. The Q quantity is a function of J, the crack shape and size, the structural geometry, mode of loading and on the level of deformation and can only be calculated from a high resolution elastic-plastic computational analysis. A similar, simpler, but more controversial approach has been suggested by Betegon and Hancock (1991), who use the non-singular term of the elastic, crack singularity solution, called the T-Stress, as a measure of elastic-plastic crack tip constraint. The objective of this work is to develop some upper shelf, elastic-plastic experimental results to attempt to investigate the applicability of the Q and T stress parameters to the correlation of upper shelf initiation toughness and J resistance curves. The first objective was to obtain upper shelf J resistance curves, J{sub Ic}, and tearing resistance results for a range of applied constraint. The J-Q and J-T stress loci were developed and compared with the expectations of the O`Dowd and Shih and the Betegon and Hancock analyses. Constraint was varied by changing the crack length and also by changing the mode of loading from bending to predominantly tensile. The principle conclusions of this work are that J{sub Ic} does not appear to be dependent on T stress or Q while the material tearing resistance is dependent on T stress and Q, with the tearing modulus increasing as constraint decreases.

  4. Toughness measurements of tungsten coated ferritic steels using laser induced stress pulses

    International Nuclear Information System (INIS)

    El-Awady, J.; Gupta, V.; Kim, B.; Ghoniem, N.; Sharafat, S.

    2007-01-01

    Full text of publication follows: Tungsten is a primary candidate for armor material protecting low activation ferritic steel in plasma facing components. The tungsten coatings are applied by HIPing or vacuum plasma spraying (VPS). To facilitate high helium recycling of implanted helium from the armor surface, a high porosity (10% - 30%) VPS Tungsten coating consisting of nano-sized particles was produced. Because, these pores can act as crack nucleation sites, the resistance of the coating to failure is an important factor that needs to be quantified. The failure strength of coating is typically measured by pulling on the coatings or bending the samples until failure. Such techniques introduce a significant number of uncertainties regarding the accuracy of the resultant coating strength. One of the major obstacles in such techniques is the difficulty in measuring the intrinsic mechanical properties independently form the extrinsic effects arising from material inelasticity, specimen geometry and loading configuration. To avoid such extrinsic effects we use the Laser Spallation Technique (LST) to relate the local energy release rate (i.e. coating toughness) to the coating's free surface velocity following a nano-second laser induced compression/tension stress wave in the samples. The propagation of the tension wave results in the dynamic failure of the weakest link in the coating itself or bond interface. This technique produces high strain rate loadings (10 7 sec -1 ) that will suppress all inelastic deformation accompanying the crack initiation at pores sites, thus yielding a coating toughness value representative of the intrinsic interfacial energy. This coating toughness is then used to evaluate the true failure strength of the coating through numerical analysis based on the true geometry and true loading configuration in a typical fusion reactor environment. (authors)

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

    OpenAIRE

    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

    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...

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

    Directory of Open Access Journals (Sweden)

    Feng Jin

    2016-01-01

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

  7. 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

  8. Effect of accelerated aging on the fracture toughness of zirconias.

    Science.gov (United States)

    Harada, Kosuke; Shinya, Akikazu; Gomi, Harunori; Hatano, Yasuo; Shinya, Akiyoshi; Raigrodski, Ariel J

    2016-02-01

    Low temperature degradation (LTD) of yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) is of concern. The purpose of this in vitro study was to assess the effect of accelerated aging on the Vickers hardness and fracture toughness of a newly developed Y-TZP and 2 primary Y-TZPs. Two primary 3 mol% Y-TZP, Lava (LA), Everest Zirconium Soft (EV), and a new 3 mol% Y-TZP, ZirTough (NZ) were assessed. Specimens (n=30 each brand) of 10 × 10 × 3 mm were hydrothermally treated for accelerated aging to examine LTD. Five conditions were used (n = 5 per condition) as follows: control group (no aging); 5 hours at 134°C/0.2 MPa (5h-134°C); 100 hours at 134°C/0.2 MPa (100 h-134°C); 5 hours at 180°C/1.0 MPa (5 h-180°C); and 20 hours at 180°C/1.0 MPa (20 h-180°C). Fracture toughness was measured by using the indentation fracture (IF) method under a loading of 294 N and calculated from the obtained measurements. To observe differences in particle composition and fracture patterns, mirror-polished test specimens (n=5 each brand) were re-sintered at 1200°C for 1 hour as a thermal etching process, and a Vickers indenter was pressed into the test specimens according to the IF method. Test piece surfaces and cracks were observed with scanning electron microscopy (SEM). One-way ANOVA and the post- hoc (Scheffé test were used to examine) interlevel significant differences (α=.05). The Vickers hardness and fracture toughness were as follows: 1319 HV and 7.36 MPa · m(1/2) for LA, and 1371 HV and 6.76 MPa · m(1/2) for EV in no aging; 1334 HV and 7.02 MPa · m(1/2) for LA, and 1346 HV and 6.07 MPa · m(1/2) for EV in 5h-134°C. No significant differences were found between no aging and 5h-134°C for LA and EV for Vickers hardness and fracture toughness. Measurements could not be made for LA and EV for 100 h-134°C, 5h-180°C, or 20 h-180°C because of fractures in the surface layer. For NZ, Vickers hardness and fracture toughness were as follows: 1261 HV and 15.60 MPa

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

    Indian Academy of Sciences (India)

    Unknown

    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 in engi- neering structures. To nuclear scientists it is of great value in the study of irradiation related damage as the.

  10. High Toughness Light Weight Pressure Vessel, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Proposed is a pressure vessel with 25% better Fracture Strength over equal strength designed Fiberglass to help reduce 10 to 25% weight for aerospace use. Phase I is...

  11. Dynamic fracture toughness (JId) behavior of armor-grade Q&T steel weldments: Effect of weld metal composition and microstructure

    Science.gov (United States)

    Magudeeswaran, Govindaraj; Balasubramanian, Visvalingam; Sathyanarayanan, S.; Madhusudhan Reddy, Gankidi; Moitra, A.; Venugopal, S.; Sasikala, G.

    2009-12-01

    Austenitic stainless steel, low hydrogen ferritic steel and high nickel steel consumables are used for the welding of armor-grade quenched and tempered (Q&T) steels. The use of such consumables in the welding of armorgrade Q&T steel leads to the formation of distinct microstructures in the respective welds and has a major influence on the dynamic fracture toughness. Hence, this paper examines how shielded metal arc welding consumables affect the dynamic fracture toughness (J1d) of armor-grade Q&T steel joints. The J1d values of joints fabricated with high nickel steel joints are superior than all other joints.

  12. Effect of Heat Treatment Parameters on the Toughness of Unalloyed Ausferritic Ductile Iron

    Directory of Open Access Journals (Sweden)

    Guzik E.

    2016-06-01

    Full Text Available Studies were carried out to determine the effect of heat treatment parameters on the plastic properties of unalloyed ausferritic ductile iron, such as the elongation and toughness at ambient temperature and at – 60 °C. The effect of austenitizing temperature (850, 900 and 950°C and ausferritizing time (5 - 180 min. at a temperature of 360°C was also discussed. The next step covered investigations of a relationship that is believed to exist between the temperature (270, 300, 330, 360 and 390 °C and time (5, 10, 30, 60, 90, 120, 150, 180, 240 min. of the austempering treatment and the mechanical properties of unalloyed ausferritic ductile iron, when the austenitizing temperature is 950°C. The “process window” was calculated for the ADI characterized by high toughness corresponding to the EN-GJS-800-10-RT and EN-GJS-900-8 grades according to EN-PN 1564 and to other high-strength grades included in this standard. Low-alloyed cast iron with the nodular graphite is an excellent starting material for the technological design of all the ausferritic ductile iron grades included in the PN-EN-1624 standard. The examined cast iron is characterized by high mechanical properties stable within the entire range of heat treatment parameters.

  13. A turbulent transport network model in MULTIFLUX coupled with TOUGH2

    International Nuclear Information System (INIS)

    Danko, G.; Bahrami, D.; Birkholzer, J.T.

    2011-01-01

    A new numerical method is described for the fully iterated, conjugate solution of two discrete submodels, involving (a) a transport network model for heat, moisture, and airflows in a high-permeability, air-filled cavity; and (b) a variably saturated fractured porous medium. The transport network submodel is an integrated-parameter, computational fluid dynamics solver, describing the thermal-hydrologic transport processes in the flow channel system of the cavity with laminar or turbulent flow and convective heat and mass transport, using MULTIFLUX. The porous medium submodel, using TOUGH2, is a solver for the heat and mass transport in the fractured rock mass. The new model solution extends the application fields of TOUGH2 by integrating it with turbulent flow and transport in a discrete flow network system. We present demonstrational results for a nuclear waste repository application at Yucca Mountain with the most realistic model assumptions and input parameters including the geometrical layout of the nuclear spent fuel and waste with variable heat load for the individual containers. The MULTIFLUX and TOUGH2 model elements are fully iterated, applying a programmed reprocessing of the Numerical Transport Code Functionalization model-element in an automated Outside Balance Iteration loop. The natural, convective airflow field and the heat and mass transport in a representative emplacement drift during postclosure are explicitly solved in the new model. The results demonstrate that the direction and magnitude of the air circulation patterns and all transport modes are strongly affected by the heat and moisture transport processes in the surrounding rock, justifying the need for a coupled, fully iterated model solution such as the one presented in the paper.

  14. Fracture toughness of esthetic dental coating systems by nanoindentation and FIB sectional analysis.

    Science.gov (United States)

    Pecnik, Christina Martina; Courty, Diana; Muff, Daniel; Spolenak, Ralph

    2015-07-01

    Improving the esthetics of Ti-based dental implants is the last challenge remaining in the optimization process. The optical issues were recently solved by the application of highly and selectively reflective coatings on Ti implants. This work focuses on the mechanical durability of these esthetic ceramic based coating systems (with and without adhesion layers). The coating systems (Ti-ZrO2, Ti-Al-ZrO2, Ti-Ti-Al-ZrO2, Ti-Ag-ZrO2, Ti-Ti-Ag-ZrO2, Ti-Bragg and Ti-TiO2-Bragg) were subjected to nanoindentation experiments and examined using scanning electron microscopy and focused ion beam cross sectional analysis. Three coating systems contained adhesion layers (10nm of Ti or 60nm of TiO2 layers). The fracture toughness of selected samples was assessed applying two different models from literature, a classical for bulk materials and an energy-based model, which was further developed and adjusted. The ZrO2 based coating systems (total film thicknesstoughness between 2.70 and 3.70MPam(1/2) was calculated using an energy-based model. The classical model was applied to Bragg coated samples and their fracture toughness ranged between 0.70 and 0.80MPam(1/2). Furthermore, coating systems containing an additional layer (Ti-Ti-Al-ZrO2, Ti-Ti-Ag-ZrO2 and Ti-TiO2-Bragg) showed an improved adhesion between the substrate and the coating. The addition of a Ti or TiO2 layer improved the adhesion between substrate and coating. The validity of the models for the assessment of the fracture toughness depended on the layer structure and fracture profile of the samples investigated here (classical model for thick coatings and energy-based model for thin coatings). Copyright © 2015 Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

    Cowden, Richard G; Meyer-Weitz, Anna; Oppong Asante, Kwaku

    2016-01-01

    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 Sports 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 = 0.59), but negatively associated with total stress (r = -0.44). The resilience subscales of perception of self, perception of future, social competence, and social resources, but not family cohesion, significantly predicted total MT (R (2) = 0.35). Both total resilience and total MT significantly predicted total stress (R (2) = 0.21). 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.

  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. 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.

  18. 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.

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

    Science.gov (United States)

    Cowden, Richard G.; Meyer-Weitz, Anna; Oppong Asante, Kwaku

    2016-01-01

    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 Sports 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 = 0.59), but negatively associated with total stress (r = -0.44). The resilience subscales of perception of self, perception of future, social competence, and social resources, but not family cohesion, significantly predicted total MT (R2 = 0.35). Both total resilience and total MT significantly predicted total stress (R2 = 0.21). 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. PMID:27014132

  20. Size Effect in Fracture Toughness Determination of Brittle Matreials

    Czech Academy of Sciences Publication Activity Database

    Chlup, Zdeněk; Dlouhý, Ivo

    2006-01-01

    Roč. 45, - (2006), s. 101-106 ISSN 1662-0356. [CIMTEC 2006. Intrenational Ceramics Congress /11./. Acireale, 04.06.2006-09.06.2006] R&D Projects: GA MŠk ME 854; GA ČR GP106/05/P119 Institutional research plan: CEZ:AV0Z20410507 Keywords : fracture toughness * ceramics * straight-notch technique Subject RIV: JL - Materials Fatigue, Friction Mechanics

  1. 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...

  2. 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...

  3. 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).

  4. Oxide inclusions in laser additive manufactured stainless steel and their effects on impact toughness and stress corrosion cracking behavior

    Science.gov (United States)

    Lou, Xiaoyuan; Andresen, Peter L.; Rebak, Raul B.

    2018-02-01

    Intergranular and intragranular Si and Mn rich oxide inclusions are present in laser additive manufactured austenitic stainless steel. The uniform oxide dispersions in additive manufactured material promoted early initiation of microvoids and reduced its impact toughness relative to powder metallurgy (hot isostatic pressing) and wrought materials. For stress corrosion cracking in high temperature water, the silica inclusions along the grain boundaries preferentially dissolved and appeared to accelerate oxidation and caused extensive crack branching.

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

    International Nuclear Information System (INIS)

    Rintamaa, R.

    1993-04-01

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

  6. Toughness of carbon nanotubes conforms to classic fracture mechanics.

    Science.gov (United States)

    Yang, Lin; Greenfeld, Israel; Wagner, H Daniel

    2016-02-01

    Defects in crystalline structure are commonly believed to degrade the ideal strength of carbon nanotubes. However, the fracture mechanisms induced by such defects, as well as the validity of solid mechanics theories at the nanoscale, are still under debate. We show that the fracture toughness of single-walled nanotubes (SWNTs) conforms to the classic theory of fracture mechanics, even for the smallest possible vacancy defect (~2 Å). By simulating tension of SWNTs containing common types of defects, we demonstrate how stress concentration at the defect boundary leads to brittle (unstable) fracturing at a relatively low strain, degrading the ideal strength of SWNTs by up to 60%. We find that, owing to the SWNT's truss-like structure, defects at this scale are not sharp and stress concentrations are finite and low. Moreover, stress concentration, a geometric property at the macroscale, is interrelated with the SWNT fracture toughness, a material property. The resulting SWNT fracture toughness is 2.7 MPa m(0.5), typical of moderately brittle materials and applicable also to graphene.

  7. 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.

  8. 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).

  9. Anisotropic toughness and strength in graphene and its atomistic origin

    Science.gov (United States)

    Hossain, M. Zubaer; Ahmed, Tousif; Silverman, Benjamin; Khawaja, M. Shehroz; Calderon, Justice; Rutten, Andrew; Tse, Stanley

    2018-01-01

    This paper presents the implication of crystallographic orientation on toughness and ideal strength in graphene under lattice symmetry-preserving and symmetry-breaking deformations. In symmetry-preserving deformation, both toughness and strength are isotropic, regardless of the chirality of the lattice; whereas, in symmetry-breaking deformation they are strongly anisotropic, even in the presence of vacancy defects. The maximum and minimum of toughness or strength occur for loading along the zigzag direction and the armchair direction, respectively. The anisotropic behavior is governed by a complex interplay among bond-stretching deformation, bond-bending deformation, and the chirality of the lattice. Nevertheless, the condition for crack-nucleation is dictated by the maximum bond-force required for bond rupture, and it is independent of the chiral angle of the lattice or loading direction. At the onset of crack-nucleation a localized nucleation zone is formed, wherein the bonds rupture locally satisfying the maximum bond-force criterion. The nucleation zone acts as the physical origin in triggering the fracture nucleation process, but its presence is undetectable from the macroscopic stress-strain data.

  10. Examining Dark Triad traits in relation to mental toughness and physical activity in young adults.

    Science.gov (United States)

    Sabouri, Sarah; Gerber, Markus; Sadeghi Bahmani, Dena; Lemola, Sakari; Clough, Peter J; Kalak, Nadeem; Shamsi, Mahin; Holsboer-Trachsler, Edith; Brand, Serge

    2016-01-01

    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. 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. 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. 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.

  11. Visible Light Photoinitiator for 3D-Printing of Tough Methacrylate Resins.

    Science.gov (United States)

    Steyrer, Bernhard; Neubauer, Philipp; Liska, Robert; Stampfl, Jürgen

    2017-12-19

    Lithography-based additive manufacturing was introduced in the 1980s, and is still the method of choice for printing accurate plastic parts with high surface quality. Recent progress in this field has made tough photopolymer resins and cheap LED light engines available. This study presents the influence of photoinitiator selection and post-processing on the thermomechanical properties of various tough photopolymers. The influence of three photoinitiators (Ivocerin, BAPO, and TPO-L) on the double-bond conversion and mechanical properties was investigated by mid infrared spectroscopy, dynamic mechanical analysis and tensile tests. It was found that 1.18 wt % TPO-L would provide the best overall results in terms of double-bond conversion and mechanical properties. A correlation between double-bond conversion, yield strength, and glass transition temperature was found. Elongation at break remained high after post-curing at about 80-100%, and was not influenced by higher photoinitiator concentration. Finally, functional parts with 41 MPa tensile strength, 82% elongation at break, and 112 °C glass transition temperature were printed on a 405 nm DLP (digital light processing) printer.

  12. Improvement of the fracture toughness in the PWR pressurizer surgeline material (Final report)

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Jun Hwa; Lee, Bong Sang; Oh, Yong Jun; Yoon, Ji Hyun; Oh, Jong Myung; Park, Buk Gyun; Kim, Ju Hak; Kuk Il Hyun; Byun, Taek Sang [Korea Atomic Energy Research Institute, Taejon (Korea)

    1998-12-01

    Fracture toughness property of PWR surgeline pipe materials is one of the most important factor for Leak Before Break(LBB) analysis. In order to improve fracture toughness of the surgeline material (SA312-TP347 stainless steel), base on the evaluation and analysis of the commercial TP347 alloys, eleven TP347 model alloys were designed and manufactured. Tensile and fracture resistance properties of the model alloys, as well as microstructure, were evaluated. It is concluded that the nitrogen shall be added more than 0.1% for high tensile property and the carbon shall be in the range of 0.02 to 0.04% for high fracture resistance. In addition, four TP316N stainless steels were manufactured and evaluated to find out the applicability as a candidate material for PWR surgeline pipe. As a conclusion, TP316N stainless steels had an excellent property to be used for surgeline piping materials, substituting the present TP347 stainless steels. (author). 11 refs., 50 figs., 12 tabs.

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

    International Nuclear Information System (INIS)

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

    2003-01-01

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

  14. "Sleep well, our tough heroes!"--in adolescence, greater mental toughness is related to better sleep schedules.

    Science.gov (United States)

    Brand, Serge; Gerber, Markus; Kalak, Nadeem; Kirov, Roumen; Lemola, Sakari; Clough, Peter J; Pühse, Uwe; Holsboer-Trachsler, Edith

    2014-01-01

    Mental toughness (MT) is understood as the display of confidence, commitment, challenge, and control. The aim of this study was to explore the extent to which greater MT is associated with subjectively assessed sleep among adolescents. A total of 284 adolescents (M = 18.26 years) completed a series of questionnaires assessing MT, psychological functioning, and sleep. Greater MT was significantly associated with better sleep quality, shorter sleep onset latency, fewer awakenings after sleep onset, and longer sleep duration. Greater MT was also associated with less perceived stress and less depressive symptoms. MT was directly and indirectly associated with sleep quality. Mentally tough adolescents report good sleep quality and sleep schedules, along with psychological wellbeing.

  15. Interlaminar toughness of fusion bonded thermoplastic composites

    NARCIS (Netherlands)

    Sacchetti, Francisco R.

    2017-01-01

    Thermoplastic composites are of increasing interest to the aerospace industry. The melt-processability of the thermoplastic matrix allows for fast manufacturing and assembling techniques, such as thermoforming and fusion bonding, which are also highly suitable for process automation. Fusion bonding

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

    International Nuclear Information System (INIS)

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

    1999-10-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1999-10-01

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

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

    Science.gov (United States)

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

    2018-02-24

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

  19. Enhancement of toughness and wear resistance in boron nitride nanoplatelet (BNNP) reinforced Si3N4 nanocomposites

    Science.gov (United States)

    Lee, Bin; Lee, Dongju; Lee, Jun Ho; Ryu, Ho Jin; Hong, Soon Hyung

    2016-06-01

    Ceramics have superior hardness, strength and corrosion resistance, but are also associated with poor toughness. Here, we propose the boron nitride nanoplatelet (BNNP) as a novel toughening reinforcement component to ceramics with outstanding mechanical properties and high-temperature stability. We used a planetary ball-milling process to exfoliate BNNPs in a scalable manner and functionalizes them with polystyrene sulfonate. Non-covalently functionalized BNNPs were homogeneously dispersed with Si3N4 powders using a surfactant and then consolidated by hot pressing. The fracture toughness of the BNNP/Si3N4 nanocomposite increased by as much as 24.7% with 2 vol.% of BNNPs. Furthermore, BNNPs enhanced strength (9.4%) and the tribological properties (26.7%) of the ceramic matrix. Microstructural analyzes have shown that the toughening mechanisms are combinations of the pull-out, crack bridging, branching and blunting mechanisms.

  20. Analysis of interlaminar fracture toughness and damage mechanisms in composite laminates reinforced with sprayed multi-walled carbon nanotubes

    KAUST Repository

    Almuhammadi, Khaled

    2014-01-01

    The present work is focused on the nanoreinforcement of prepreg based carbon fiber composite laminates to improve delamination resistance. Functionalized multi-walled carbon nanotubes (MWCNTs) were dispersed over the interface between prepreg layers through solvent spraying and the resulting mode I interlaminar fracture toughness was determined. For comparison, baseline samples with neat prepregs were also prepared. Results indicate that the introduction of functionalized MWCNTs can favorably affect the interlaminar fracture toughness, and the associated mechanisms of failure have been investigated. The manufacturing procedures and the interfacial reinforcing mechanism were explored by analyzing (i) the wettability between CNTs-solvent solution and prepreg surface, (ii) CNTs dispersion and (iii) the fractured surfaces through high resolution scanning electron microscopy and Raman mapping. © 2013 Elsevier Ltd.

  1. INFLUENCE OF MULTILAYER NANOTUBES ON FRACTURE TOUGHNESS

    Directory of Open Access Journals (Sweden)

    B. M. Khroustalev

    2012-01-01

    Full Text Available Experimental research results of the stress intensity factor at normal separation, КIC, and cross-section shift, KIIC, respectively, of high-strength concrete are presented. Research on the specific power changing inputs on quasi-static destruction is carried out.The compact structure on the basis of the Portland cement modified with carbon nanodispersed systems has been studied. Carbon nanotubes Graphistrength by «Arkema» dispersed into the hydrodynamic plant in the solution of surface-active agent (SAA Polyplast SP-1 are used as modifying additives. An increase of the cross-breaking strength of a fine grain concrete up to 45,1 % and of the compressing strength up to 96,8 % was observed. The increase of concrete strength is related to morphological changes of new crystalline hydrate formations providing a less defective structure of cement matrix with high density. 

  2. Experimental Determination of the Fracture Toughness and Brittleness of the Mancos Shale, Utah.

    Science.gov (United States)

    Chandler, Mike; Meredith, Phil; Crawford, Brian

    2013-04-01

    The hydraulic fracturing of Gas-Shales has become a topic of interest since the US Shale Gas Revolution, and is increasingly being investigated across Europe. A significant issue during hydraulic fracturing is the risk of fractures propagating further than desired into aquifers or faults. This occured at Preese Hall, UK in April and May 2011 when hydraulic fractures propagated into an adjacent fault causing 2.3ML and 1.7ML earthquakes [1]. A rigorous understanding of how hydraulic fractures propagate under in-situ conditions is therefore important for treatment design, both to maximise gas accessed, and to minimise risks due to fracture overextension. Fractures will always propagate along the path of least resistance, but the direction and extent of this path is a complex relationship between the in-situ stress-field, the anisotropic mechanical properties of the rock, and the pore and fracturing pressures [2]. It is possible to estimate the anisotropic in-situ stress field using an isolated-section hydraulic fracture test, and the pore-pressure using well logs. However, the anisotropic mechanical properties of gas-shales remain poorly constrained, with a wide range of reported values. In particular, there is an extreme paucity of published data on the Fracture Toughness of soft sediments such as shales. Mode-I Fracture Toughness is a measure of a material's resistance to dynamic tensile fracture propagation. Defects such as pre-existing microcracks and pores in a material can induce high local stress concentrations, causing fracture propagation and material failure under substantially lower stress than its bulk strength. The mode-I stress intensity factor, KI, quantifies the concentration of stress at the crack tip. For linear elastic materials the Fracture Toughness is defined by the critical value of this stress intensity factor; KIc, beyond which rapid catastrophic crack growth occurs. However, rocks such as shales are relatively ductile and display significant

  3. 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.

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

    Directory of Open Access Journals (Sweden)

    Garry Kuan

    2007-10-01

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

  5. Imaging Inelastic Fracture Processes in Biomimetic Nanocomposites and Nacre by Laser Speckle for Better Toughness.

    Science.gov (United States)

    Verho, Tuukka; Karppinen, Pasi; Gröschel, André H; Ikkala, Olli

    2018-01-01

    Mollusk nacre is a prototypical biological inorganic-organic composite that combines high toughness, stiffness, and strength by its brick-and-mortar microstructure, which has inspired several synthetic mimics. Its remarkable fracture toughness relies on inelastic deformations at the process zone at the crack tip that dissolve stress concentrations and stop cracks. The micrometer-scale structure allows resolving the size and shape of the process zone to understand the fracture processes. However, for better scalability, nacre-mimetic nanocomposites with aligned inorganic or graphene nanosheets are extensively pursued, to avoid the packing problems of mesoscale sheets like in nacre or slow in situ biomineralization. This calls for novel methods to explore the process zone of biomimetic nanocomposites. Here the fracture of nacre and nacre-inspired clay/polymer nanocomposite is explored using laser speckle imaging that reveals the process zone even in absence of changes in optical scattering. To demonstrate the diagnostic value, compared to nacre, the nacre-inspired nanocomposite develops a process zone more abruptly with macroscopic crack deflection shown by a flattened process zone. In situ scanning electron microscopy suggests similar toughening mechanisms in nanocomposite and nacre. These new insights guide the design of nacre-inspired nanocomposites toward better mechanical properties to reach the level of synergy of their biological model.

  6. Fracture toughness of austenitic stainless steel weld metal at 4 K

    International Nuclear Information System (INIS)

    Goodwin, G.M.

    1984-08-01

    Selection of the welding processess and weld filler metals for fabrication of a large toroidal superconducting magnet is described. Data available in the literature are collected and compared with data generated in this study for three welding processes, shielded metal arc (SMA), gas tungsten arc (GTA), and flux cored arc (FCA) welds had the highest fracture toughness as measured by K/sub Ic/ estimated from J/sub Ic/. The SMA and FCA welds had about the same toughness, below the GTA values but above the average from the literature. The fracture mode for all three processes was typified by ductile dimples. The fracture morphology of the FCA weld specimens was influenced by the solidification substructure, and small particles were found to be nucleation sites for void formation, especially for the GTA welds. All three welding processes were deemed adequate for the intended service and were used to fabricate the large magnet. A trunnion-type turning fixture eliminated the need for welding in the vertical and overhead positions. The GTA process was used for all root passes, and the horizontal welds were filled by the SMA process. Over 80% of the welds were done in the flat position with the FCA process, and its high deposition rate and ease of operation are credited with contributing greatly to the success of the effort

  7. Fracture fragility of HFIR vessel caused by random crack size or random toughness

    International Nuclear Information System (INIS)

    Chang, Shih-Jung; Proctor, L.D.

    1993-01-01

    This report discuses the probability of fracture (fracture fragility) versus a range of applied hoop stresses along the HFIR vessel which is obtained as an estimate of its fracture capacity. Both the crack size and the fracture toughness are assumed to be random variables that follow given distribution functions. Possible hoop stress is based on the numerical solution of the vessel response by applying a point pressure-pulse it the center of the fluid volume within the vessel. Both the fluid-structure interaction and radiation embrittlement are taken into consideration. Elastic fracture mechanics is used throughout the analysis. The probability of vessel fracture for a single crack caused by either a variable crack depth or a variable toughness is first derived. Then the probability of fracture with multiple number of cracks is obtained. The probability of fracture is further extended to include different levels of confidence and variability. It, therefore, enables one to estimate the high confidence and low probability capacity accident load

  8. HYDROGEN EFFECTS ON THE FRACTURE TOUGHNESS PROPERTIES OF FORGED STAINLESS STEELS

    Energy Technology Data Exchange (ETDEWEB)

    Morgan, M

    2008-03-28

    The effect of hydrogen on the fracture toughness properties of Types 304L, 316L and 21-6-9 forged stainless steels was investigated. Fracture toughness samples were fabricated from forward-extruded forgings. Samples were uniformly saturated with hydrogen after exposure to hydrogen gas at 34 MPa or 69 and 623 K prior to testing. The fracture toughness properties were characterized by measuring the J-R behavior at ambient temperature in air. The results show that the hydrogen-charged steels have fracture toughness values that were about 50-60% of the values measured for the unexposed steels. The reduction in fracture toughness was accompanied by a change in fracture appearance. Both uncharged and hydrogen-charged samples failed by microvoid nucleation and coalescence, but the fracture surfaces of the hydrogen-charged steels had smaller microvoids. Type 316L stainless steel had the highest fracture toughness properties and the greatest resistance to hydrogen degradation.

  9. Tough and corrosion resistant austenitic alloy

    International Nuclear Information System (INIS)

    Johnson, T.E.

    1977-01-01

    The invention concerns austenitic alloys of high corrosion resistance, which can be deformed hot and tempered, so that they can be forged, rolled, and drawn into tubes and other shapes. The alloys have a basis of nickel, chromium and iron. The silicon content is between 2 and 4% by weight, and the molybdenum content is between 0 and 2% by weight. The alloys can be hardened by ageing and contain up to 0.1% by weight of boron. The other alloying materials are 1 to 3.5% by weight of manganese, 4 to 7.5% by weight of cobalt, 2.5 to 8% by weight of copper and 0.05 to 0.25% by weight of carbon. (IHOE) [de

  10. Plastic η-factor for Fracture Toughness Test of SA508 Narrow-gap Welds

    International Nuclear Information System (INIS)

    Huh, Yong; Cho, Sung Keun; Koo, Jae Mean; Seok, Chang Sung

    2007-01-01

    In this study, the plastic η-factors of SA508 narrow-gap welding part used for the primary piping system of nuclear power plant were obtained using the finite element analysis and suggested the revised fracture toughness testing method for the narrow-gap welding part. Also, we have performed the fracture toughness test for SA508 narrow-gap welding part applying the new testing method then compared the results with those by fracture toughness test according to ASTM

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

    OpenAIRE

    Feng Jin

    2016-01-01

    Four hundred and two R&D personnel were surveyed through questionnaires to study the relationship between mental toughness, stress appraisal (including experience of stress and stress control), and innovation performance. The findings reveal a significant negative correlation between mental toughness and stress experience and a significant positive correlation between mental toughness and both stress control and innovation performance. Furthermore, although the experience of stress was negati...

  12. The stability of mental toughness across situations: taking a social-cognitive approach

    OpenAIRE

    Weinberg, Robert; Butt, Joanne; Mellano, Kathleen; Harmsion, Robert

    2017-01-01

    The present study adopted a social-cognitive perspective to explore the stability of mental toughness. Specifically, the purpose of this study was two-fold: (a)to explore possible fluctuations in mental toughness across situations; and (b) to identify the cognitions, affect, and behaviors associated with perceived mental toughness and mental weakness. Participants were tennis players (n=12) based full time in an elite performance academy and were aged between 14 and 20 years (Mage = 29 16.5; ...

  13. Interrelation of material microstructure, ultrasonic factors, and fracture toughness of two phase titanium alloy

    Science.gov (United States)

    Vary, A.; Hull, D. R.

    1982-01-01

    The pivotal role of an alpha-beta phase microstructure in governing fracture toughness in a titanium alloy, Ti-662, is demonstrated. The interrelation of microstructure and fracture toughness is demonstrated using ultrasonic measurement techniques originally developed for nondestructive evaluation and material property characterization. It is shown that the findings determined from ultrasonic measurements agree with conclusions based on metallurgical, metallographic, and fractographic observations concerning the importance of alpha-beta morphology in controlling fracture toughness in two phase titanium alloys.

  14. Effect of WC/Co coherency phase boundaries on Fracture toughness of the nanocrystalline cemented carbides

    OpenAIRE

    Hongxian Xie; Xiaoyan Song; Fuxing Yin; Yongguang Zhang

    2016-01-01

    The effect of coherency WC/Co phase boundaries on the fracture toughness of the nanocrystalline WC-Co cemented carbides is studied by MD simulation method. The simulation results show that the nanocrystalline WC-Co cemented carbides with coherency WC/Co phase boundaries has higher fracture toughness than that without coherency WC/Co phase boundaries. Moreover, the mechanism of why coherency WC/Co phase boundaries can improve the fracture toughness of the nanocrystalline cemented carbides is a...

  15. Some observations of the influence of δ-ferrite content on the hardness, galling resistance, and fracture toughness of selected commercially available iron-based hardfacing alloys

    Science.gov (United States)

    Cockeram, B. V.

    2002-11-01

    Iron-based weld hardfacing deposits are used to provide a wear-resistant surface for a structural base material. Iron-based hardfacing alloys that are resistant to corrosion in oxygenated aqueous environments contain high levels of chromium and carbon, which results in a dendritic microstructure with a high volume fraction of interdendrite carbides which provide the needed wear resistance. The ferrite content of the dendrites depends on the nickel content and base composition of the iron-based hardfacing alloy. The amount of ferrite in the dendrites is shown to have a significant influence on the hardness and galling wear resistance, as determined using ASTM G98 methods. Fracture-toughness ( K IC) testing in accordance with ASTM E399 methods was used to quantify the damage tolerance of various iron-based hardfacing alloys. Fractographic and microstructure examinations were used to determine the influence of microstructure on the wear resistance and fracture toughness of the iron-based hardfacing alloys. A crack-bridging toughening model was shown to describe the influence of ferrite content on the fracture toughness. A higher ferrite content in the dendrites of an iron-based hardfacing alloy reduces the tendency for plastic stretching and necking of the dendrites, which results in improved wear resistance, high hardness, and lower fracture-toughness values. A NOREM 02 hardfacing alloy has the most-optimum ferrite content, which results in the most-desired balance of galling resistance and high K IC values.

  16. Understanding mental toughness in Australian soccer: perceptions of players, parents, and coaches.

    Science.gov (United States)

    Coulter, Tristan J; Mallett, Clifford J; Gucciardi, Daniel F

    2010-05-01

    We explored mental toughness in soccer using a triangulation of data capture involving players (n = 6), coaches (n = 4), and parents (n = 5). Semi-structured interviews, based on a personal construct psychology (Kelly, 1955/1991) framework, were conducted to elicit participants' perspectives on the key characteristics and their contrasts, situations demanding mental toughness, and the behaviours displayed and cognitions employed by mentally tough soccer players. The results from the research provided further evidence that mental toughness is conceptually distinct from other psychological constructs such as hardiness. The findings also supported Gucciardi, Gordon, and Dimmock's (2009) process model of mental toughness. A winning mentality and desire was identified as a key attribute of mentally tough soccer players in addition to other previously reported qualities such as self-belief, physical toughness, work ethic/motivation, and resilience. Key cognitions reported by mentally tough soccer players enabled them to remain focused and competitive during training and matches and highlighted the adoption of several forms of self-talk in dealing with challenging situations. Minor revisions to Gucciardi and colleagues' definition of mental toughness are proposed.

  17. Nanosilica Modification of Elastomer-Modified VARTM Epoxy Resins for Improved Resin and Composite Toughness

    National Research Council Canada - National Science Library

    Robinette, Jason; Bujanda, Andres; DeSchepper, Daniel; Dibelka, Jessica; Costanzo, Philip; Jensen, Robert; McKnight, Steven

    2007-01-01

    Recent publications have reported a synergy between rubber and silica in modified epoxy resins that results in significantly improved fracture toughness without reductions in other material properties...

  18. 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

    2017-01-01

    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. PMID:28773104

  19. The effect of microstructure and strength on the fracture toughness of an 18 Ni, 300 grade maraging steel

    Science.gov (United States)

    Psioda, J. A.; Low, J. R., Jr.

    1975-01-01

    A 300 grade maraging steel was chosen as a vehicle by which to understand the inverse relationship between strength and toughness in high strength alloys such as the 18 Ni maraging steels. The 18 Ni, 300 grade maraging material was a commercial grade consumable-electrode, vacuum arc remelted heat obtained in the form of forged and annealed plate. The matrix contained a population of second-phase impurity inclusions which was a product of the casting and hot working processes. These inclusions did not change with subsequent precipitation hardening. Changes in microstructure resulting in strength increases were brought about by variations in aging temperature and time. Maximum strength was attained in the 300 grade maraging steel by aging at 427 C (800 F) for 100 hours. Tensile, fatigue precracked Charpy impact, and plane-strain fracture toughness tests were performed at room temperature, 20 C (68 F). With increasing strength the fracture toughness decreases as smaller and smaller inclusions act as sites for void initiation.

  20. Effects of toughness anisotropy and combined tension, torsion, and bending loads on fracture behavior of ferritic nuclear pipe

    Energy Technology Data Exchange (ETDEWEB)

    Mohan, R.; Marshall, C.; Ghadiali, N.; Wilkowski, G. [Battelle, Columbus, OH (United States)

    1997-04-01

    This paper summarizes work on angled through-wall-crack initiation and combined loading effects on ferritic nuclear pipe performed as part of the Nuclear Regulatory Commission`s research program entitled {open_quotes}Short Cracks In Piping an Piping Welds{close_quotes}. The reader is referred to Reference 1 for details of the experiments and analyses conducted as part of this program. The major impetus for this work stemmed from the observation that initially circumferentially oriented cracks in carbon steel pipes exhibited a high tendency to grow at a different angle when the cracked pipes were subjected to bending or bending plus pressure loads. This failure mode was little understood, and the effect of angled crack grown from an initially circumferential crack raised questions about how cracks in a piping system subjected to combined loading with torsional stresses would behave. There were three major efforts undertaken in this study. The first involved a literature review to assess the causes of toughness anisotropy in ferritic pipes and to develop strength and toughness data as a function of angle from the circumferential plane. The second effort was an attempt to develop a screening criterion based on toughness anisotropy and to compare this screening criterion with experimental pipe fracture data. The third and more significant effort involved finite element analyses to examine why cracks grow at an angle and what is the effect of combined loads with torsional stresses on a circumferentially cracked pipe. These three efforts are summarized.

  1. Effects of toughness anisotropy and combined tension, torsion, and bending loads on fracture behavior of ferritic nuclear pipe

    International Nuclear Information System (INIS)

    Mohan, R.; Marshall, C.; Ghadiali, N.; Wilkowski, G.

    1997-01-01

    This paper summarizes work on angled through-wall-crack initiation and combined loading effects on ferritic nuclear pipe performed as part of the Nuclear Regulatory Commission's research program entitled open-quotes Short Cracks In Piping an Piping Weldsclose quotes. The reader is referred to Reference 1 for details of the experiments and analyses conducted as part of this program. The major impetus for this work stemmed from the observation that initially circumferentially oriented cracks in carbon steel pipes exhibited a high tendency to grow at a different angle when the cracked pipes were subjected to bending or bending plus pressure loads. This failure mode was little understood, and the effect of angled crack grown from an initially circumferential crack raised questions about how cracks in a piping system subjected to combined loading with torsional stresses would behave. There were three major efforts undertaken in this study. The first involved a literature review to assess the causes of toughness anisotropy in ferritic pipes and to develop strength and toughness data as a function of angle from the circumferential plane. The second effort was an attempt to develop a screening criterion based on toughness anisotropy and to compare this screening criterion with experimental pipe fracture data. The third and more significant effort involved finite element analyses to examine why cracks grow at an angle and what is the effect of combined loads with torsional stresses on a circumferentially cracked pipe. These three efforts are summarized

  2. WinGridder - An interactive grid generator for TOUGH - A user's manual (Version 1.0)

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Lehua; Hinds, Jennifer; Haukwa, Charles; Wu, Yu-Shu; Bodvarsson, Gudmundur

    2001-07-18

    WinGridder is a Windows-based software package for designing, generating, and visualizing at various spatial scales numerical grids used in reservoir simulations and groundwater modeling studies. Development of this software was motivated by the requirements of the TOUGH (Transport of Unsaturated Groundwater and Heat) family of codes (Pruess 1987, 1991) for simulating subsurface processes related to high-level nuclear waste isolation in partially saturated geological media. Although the TOUGH family of codes has great flexibility in handling the variety of grid information required to describe complex objects, designing and generating a suitable irregular grid can be a tedious and error-prone process, even with the help of existing grid generating programs. This is especially true when the number of cells and connections is very large. The processes of inspecting the quality of the grid or extracting sub-grids or other specific grid information are also complex. The mesh maker embedded within TOUGH2 generates only uniform numerical grids and handles only one set of uniform fracture and matrix properties throughout the model domain. This is not suitable for grid generation in complex flow and transport simulations (such as those of Yucca Mountain, which have heterogeneity in both fracture and matrix media). As a result, the software program Amesh (Haukwa 2000) was developed to generate irregular, effective-continuum (ECM) grids.

  3. 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 τ 12 on both sides of the grain boundary, while the main crack propagation is a consequence of the normal stress to the crack.

  4. Narrow groove gas tungsten arc welding of ASTM A508 Class 4 steel for improved toughness properties

    Energy Technology Data Exchange (ETDEWEB)

    Penik, M.A. Jr. [Rensselaer Polytechnic Inst., Troy, NY (United States)

    1997-04-01

    Welding of heavy section steel has traditionally used the automatic submerged arc welding (ASAW) process because of the high deposition rates achievable. However, the properties, particularly fracture toughness, of the weld are often inferior when compared to base material. This project evaluated the use of narrow groove gas tungsten arc welding (GTAW) to improve weld material properties. The welding procedures were developed for ASTM A508 Class 4 base material using a 1% Ni filler material complying to AWS Specification A.23-90-EF3-F3-N. A narrow groove joint preparation was used in conjunction with the GTAW process so competitive fabrication rates could be achieved when compared to the ASAW process. Weld procedures were developed to refine weld substructure to achieve better mechanical properties. Two heaters of weld wire were used to examine the effects of minor filler metal chemistry differences on weld mechanical properties. Extensive metallographic evaluations showed excellent weld quality with a refined microstructure. Chemical analysis of the weld metal showed minimal weld dilution by the base metal. Mechanical testing included bend and tensile tests to ensure weld quality and strength. A Charpy impact energy curve versus temperature and fracture toughness curve versus temperature were developed for each weld wire heat. Results of fracture toughness and Charpy impact testing indicated an improved transition temperature closer to that of the base material properties.

  5. Improvement of Strength-Toughness-Hardness Balance in Large Cross-Section 718H Pre-Hardened Mold Steel

    Directory of Open Access Journals (Sweden)

    Hanghang Liu

    2018-04-01

    Full Text Available The strength-toughness combination and hardness uniformity in large cross-section 718H pre-hardened mold steel from a 20 ton ingot were investigated with three different heat treatments for industrial applications. The different microstructures, including tempered martensite, lower bainite, and retained austenite, were obtained at equivalent hardness. The microstructures were characterized by using metallographic observations, scanning electron microscopy (SEM, transmission electron microscopy (TEM, X-ray diffraction (XRD, and electron back-scattered diffraction (EBSD. The mechanical properties were compared by tensile, Charpy U-notch impact and hardness uniformity tests at room temperature. The results showed that the test steels after normalizing-quenching-tempering (N-QT possessed the best strength-toughness combination and hardness uniformity compared with the conventional quenched-tempered (QT steel. In addition, the test steel after austempering-tempering (A-T demonstrated the worse hardness uniformity and lower yield strength while possessing relatively higher elongation (17% compared with the samples after N-QT (14.5% treatments. The better ductility of A-T steel mainly depended on the amount and morphology of retained austenite and thermal/deformation-induced twined martensite. This work elucidates the mechanisms of microstructure evolution during heat treatments and will highly improve the strength-toughness-hardness trade-off in large cross-section steels.

  6. Tough Amphiphilic Gels for Antifouling Applications

    Science.gov (United States)

    Villada, Laura M.

    concentration of crosslinking agent. The resultant variation in network mesh size had the strongest correlation with the BSA adsorption (R2 = 0.90) and algal spore attachment (R2 = 0.73). The second system evaluated was based upon a new siloxane non-isocyanate urethane divinyl monomer (NIUDMA) that was synthesized using environmentally friendly methods in order to produce more mechanically durable gels. A crosslinked amphiphilic network was synthesized utilizing NIUDMA in conjunction with the relatively hydrophobic hexafluorobutyl methacrylate (HFBMA) with hydrophilic HEMA. The initial HFBMA and HEMA feed composition was varied, and the effect on gel properties was equated to anti-biofouling efficacy. The different gel compositions altered the surface chemistry slightly and the structure of their surface; however, the greatest difference was seen in the bulk structure and mechanical properties. The elastic moduli measured for these gels was much higher than the gels previously tested; it ranged from 2 MPa to as high as 140 MPa by varying the ratio of hydrophilic (20 - 90 mol%) to hydrophobic (0 - 70 mol%) monomer concentration. For the NIUDMA gels, the biofouling assays performed to probe the effect of gel properties included U. linza sporeling attachment, N. incerta diatom and C. lytica bacteria biofilm growth and removal, and A. Amphitrite adult barnacle reattachment. The most effective results were seen with the fouling release results of diatoms, with up to 96% reduction, and marine bacteria with up to 98% reduction after an applied water pressure of 138 kPa. These two microfouling marine organisms are part of the first stages of the biofouling process, and reducing their attachment and adhesion is critical for preventing or reducing the later stages. There were complex trends seen with the properties of the gels and the bioassay results. Overall, the NIUDMA10 networks had comparable results to commercial coatings against spores, diatoms and marine bacteria.

  7. 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.

  8. 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

  9. Double Cantilever Beam Fracture Toughness Testing of Several Composite Materials

    Science.gov (United States)

    Kessler, Jeff A.; Adams, Donald F.

    1992-01-01

    Double-cantilever beam fracture toughness tests were performed by the Composite Materials Research Group on several different unidirectional composite materials provided by NASA Langley Research Center. The composite materials consisted of Hercules IM-7 carbon fiber and various matrix resin formulations. Multiple formulations of four different families of matrix resins were tested: LaRC - ITPI, LaRC - IA, RPT46T, and RP67/RP55. Report presents the materials tested and pertinent details supplied by NASA. For each material, three replicate specimens were tested. Multiple crack extensions were performed on each replicate.

  10. 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

  11. Relationships between fracture toughness and other material properties. Final report

    International Nuclear Information System (INIS)

    Perra, M.; Finnie, I.

    1974-01-01

    The key experimental and analytical studies which have led to our present understanding of the mechanisms of ductile fracture are reviewed. It is concluded that insufficient progress has been made in the quantitative description of ductile separation mechanisms on a microscale to allow the realistic prediction of fracture toughness from material properties and microstructure. An experimental study of ductile fracture is underway which has the aim of determining the growth rate of voids in known plastic deformation fields as a function of triaxiality of stress and material work-hardening. Novel specimens of particularly well characterized microstructure are utilized

  12. Study on Nanostructures Induced by High-Current Pulsed Electron Beam

    Directory of Open Access Journals (Sweden)

    Bo Gao

    2012-01-01

    Full Text Available Four techniques using high-current pulsed electron beam (HCPEB were proposed to obtain surface nanostructure of metal and alloys. The first method involves the distribution of several fine Mg nanoparticles on the top surface of treated samples by evaporation of pure Mg with low boiling point. The second technique uses superfast heating, melting, and cooling induced by HCPEB irradiation to refine the primary phase or the second phase in alloys to nanosized uniform distributed phases in the matrix, such as the quasicrystal phase Mg30Zn60Y10 in the quasicrystal alloy Mg67Zn30Y3. The third technique involves the refinement of eutectic silicon phase in hypereutectic Al-15Si alloys to fine particles with the size of several nanometers through solid solution and precipitation refinement. Finally, in the deformation zone induced by HCPEB irradiation, the grain size can be refined to several hundred nanometers, such as the grain size of the hypereutectic Al-15Si alloys in the deformation zone, which can reach ~400 nm after HCPEB treatment for 25 pulses. Therefore, HCPEB technology is an efficient way to obtain surface nanostructure.

  13. 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.

  14. Wingridder - an interactive grid generator for TOUGH2

    International Nuclear Information System (INIS)

    Pan, Lehua

    2003-01-01

    The TOUGH (Transport Of Unsaturated Groundwater and Heat) family of codes has great flexibility in handling the variety of grid information required to describe a complex subsurface system. However, designing and generating such a grid can be a tedious and error-prone process. This is especially true when the number of cells and connections is very large. As a user-friendly, efficient, and effective grid generating software, WinGridder has been developed for designing, generating, and visualizing (at various spatial scales) numerical grids used in reservoir simulations and groundwater modeling studies. It can save mesh files for TOUGH family codes. It can also output additional grid information for various purposes in either graphic format or plain text format. It has user-friendly graphical user interfaces, along with an easy-to-use interactive design and plot tools. Many important features, such as inclined faults and offset, layering structure, local refinements, and embedded engineering structures, can be represented in the grid

  15. Crack and fracture behaviour in tough ductile materials

    International Nuclear Information System (INIS)

    Venter, R.D.; Hoeppner, D.W.

    1985-10-01

    The report describes various approaches and developments pertaining to the understanding of crack and fracture behaviour in tough ductile materials. The fundamental elastic fracture mechanics concepts based on the concepts of energy, stress field, and displacement are introduced and their interrelationships demonstrated. The extension of these concepts to include elasto-plastic fracture mechanics considerations is reviewed in the context of the preferred options available for the development of appropriate design methodologies. The recommendations of the authors are directed towards the continued development of the J-integral concept. This energy-based concept, in its fundamental form, has a sound theoretical basis and as such offers the possibility of incorporating elasto-plastic fracture mechanics considerations in the crack and fracture behaviour of tough ductile materials. It must however be emphasized that the concise defintion of J becomes increasingly suspect as the crack length increases. J is not a material property, as is J IC , but emerges as a useful empirical parameter which is dependent upon the particular geometry and the loading imposed on the structure. It is proposed that 'lowest bound' J-resistance curves and the associated J-T curves be experimentally developed and employed in the design process. Improvements to these 'lowest bounds' can be developed through extensive analysis of the twin J-CTOA criteria and validation of this approach through near full scale tests

  16. Arousal and physiological toughness: implications for mental and physical health.

    Science.gov (United States)

    Dienstbier, R A

    1989-01-01

    From W.B. Cannon's identification of adrenaline with "fight or flight" to modern views of stress, negative views of peripheral physiological arousal predominate. Sympathetic nervous system (SNS) arousal is associated with anxiety, neuroticism, the Type A personality, cardiovascular disease, and immune system suppression; illness susceptibility is associated with life events requiring adjustments. "Stress control" has become almost synonymous with arousal reduction. A contrary positive view of peripheral arousal follows from studies of subjects exposed to intermittent stressors. Such exposure leads to low SNS arousal base rates, but to strong and responsive challenge- or stress-induced SNS-adrenal-medullary arousal, with resistance to brain catecholamine depletion and with suppression of pituitary adrenal-cortical responses. That pattern of arousal defines physiological toughness and, in interaction with psychological coping, corresponds with positive performance in even complex tasks, with emotional stability, and with immune system enhancement. The toughness concept suggests an opposition between effective short- and long-term coping, with implications for effective therapies and stress-inoculating life-styles.

  17. 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.

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

    Science.gov (United States)

    Cady, Carl M.; Liu, Cheng; Lovato, Manuel L.

    2015-09-01

    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.

  19. 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.

  20. Numerical modeling of ductile tearing effects on cleavage fracture toughness

    International Nuclear Information System (INIS)

    Dodds, R.H. Jr.; Tang, M.; Anderson, T.L.

    1994-05-01

    Experimental studies demonstrate a significant effect of specimen size, a/W ratio and prior ductile tearing on cleavage fracture toughness values (J c ) measured in the ductile-to-brittle transition region of ferritic materials. In the lower-transition region, cleavage fracture often occurs under conditions of large-scale yielding but without prior ductile crack extension. The increased toughness develops when plastic zones formed at the crack tip interact with nearby specimen surfaces which relaxes crack-tip constraint (stress triaxiality). In the mid-to-upper transition region, small amounts of ductile crack extension (often c -values. Previous work by the authors described a micromechanics fracture model to correct measured J c -values for the mechanistic effects of large-scale yielding. This new work extends the model to also include the influence of ductile crack extension prior to cleavage. The paper explores development of the new model, provides necessary graphs and procedures for its application and demonstrates the effects of the model on fracture data sets for two pressure vessel steels (A533B and A515)

  1. EOSN: A TOUGH2 module for noble gases

    International Nuclear Information System (INIS)

    Shan, Chao; Pruess, Karsten

    2003-01-01

    We developed a new fluid property module for TOUGH2, called EOSN, to simulate transport of noble gases in the subsurface. Currently, users may select any of five different noble gases as well as CO2, two at a time. For the three gas components (air and two user-specified noble gases) in EOSN, the Henry's coefficients and the diffusivities in the gas phase are no longer assumed constants, but are temperature dependent. We used the Crovetto et al. (1982) model to estimate Henry's coefficients, and the Reid et al. (1987) correlations to calculate gas phase diffusivities. The new module requires users to provide names of the selected noble gases, which properties are provided internally. There are options for users to specify any (non-zero) molecular weights and half-lives for the gas components. We provide two examples to show applications of TOUGH2IEOSN. While temperature effects are relatively insignificant for one example problem where advection is dominant, they cause almost an order of magnitude difference for the other case where diffusion becomes a dominant process and temperature variations are relatively large. It appears that thermodynamic effects on gas diffusivities and Henry's coefficients can be important for low-permeability porous media and zones with large temperature variations

  2. National drug policy: implications of the 'tough on drugs' ideology.

    Science.gov (United States)

    Norman, R

    2001-10-01

    Australia has emerged over the last decade as a world leader in drug policy. According to Single and Rohl (1997 pvii) Australia's National Drug Strategy 'has been characterised by a unique combination of features which have brought it international attention and acclaim'. The strength of Australia's policy has been its emphasis on both licit and illicit drugs, and also its clear articulation of harm minimisation as a guiding principle in all areas of action. The key policy goals recognised the harm associated with all substances and sought results in key areas of alcohol-related problems, tobacco-related problems, under-age consumption, prescription medication problems and illicit drug use. However, Australia has a new drug policy document for the new millennium, The National Drug Strategic Framework 1998 - 2002. As a result of a conservative influence in national politics, this framework has moved from the harm minimisation philosophy to a moralistic 'tough on drugs' philosophy that stresses zero tolerance, law enforcement and abstinence. There is a risk that Australia will experience an increase in adverse health, social and economic consequences as a result of this new policy direction. Nurses need to think critically about the 'tough on drugs' ideology. There is a risk that significant adverse affects may occur for their drug-using patients as a result of this policy change. In their practice, nurses need to challenge the validity of a punitive response, and to commit themselves to improving the health and safety of the illicit drug-using community.

  3. Apparent Interfacial Fracture Toughness of Resin/Ceramic Systems

    Science.gov (United States)

    Della Bona, A.; Anusavice, K.J.; Mecholsky, J.J.

    2008-01-01

    We suggest that the apparent interfacial fracture toughness (KA) may be estimated by fracture mechanics and fractography. This study tested the hypothesis that the KA of the adhesion zone of resin/ceramic systems is affected by the ceramic microstructure. Lithia disilicate-based (Empress2-E2) and leucite-based (Empress-E1) ceramics were surface-treated with hydrofluoric acid (HF) and/or silane (S), followed by an adhesive resin. Microtensile test specimens (n = 30; area of 1 ± 0.01 mm2) were indented (9.8 N) at the interface and loaded to failure in tension. We used tensile strength (σ) and the critical crack size (c) to calculate KA (KA = Yσc1/2) (Y = 1.65). ANOVA and Weibull analyses were used for statistical analyses. Mean KA (MPa•m1/2) values were: (E1HF) 0.26 ± 0.06; (E1S) 0.23 ± 0.06; (E1HFS) 0.30 ± 0.06; (E2HF) 0.31 ± 0.06; (E2S) 0.13 ± 0.05; and (E2HFS) 0.41 ± 0.07. All fractures originated from indentation sites. Estimation of interfacial toughness was feasible by fracture mechanics and fractography. The KA for the systems tested was affected by the ceramic microstructure and surface treatment. PMID:17062746

  4. Toughness and other mechanical properties of the duplex stainless steel 2205

    International Nuclear Information System (INIS)

    Sieurin, H.; Sandstroem, R.

    2003-01-01

    The use and range of potential applications of duplex stainless steel continuously increase. An overview of the mechanical properties of duplex stainless steel 2205 is presented with focus on toughness properties. Impact and fracture toughness as well as strength results from the European research project, EcoPress, are presented. (orig.)

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

    Science.gov (United States)

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

    2015-01-01

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

  6. 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…

  7. 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.

  8. 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.

  9. 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...

  10. 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…

  11. Influence of interstitial solute level on toughness properties of 40% Cr-Fe stainless-steel

    CSIR Research Space (South Africa)

    Van Zwieten, ACTM

    1993-02-01

    Full Text Available . 4.2 The effects of carbon, nitrogen and oxygen on toughness The results presented earlier were vary much as predicted by the literature. It has been known for about forty years 8 that carbon and nitrogen can adversely affect the toughness...

  12. 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...

  13. Microstructure and fracture toughness of the in-situ NiAl-Ni(3)Al intermetallic composites

    Science.gov (United States)

    Gao, Qian

    1997-11-01

    increase with increasing crack extension, forming a very special shape which can be called "HOOP HEAD". Particularly, a critical value (Jsb{Ivc}) of the fracture energy for a CNB test can be simply calculated by a horizontal line tangent to the "HOOP HEAD". It is shown that fracture toughness of Nisb3Al/NiAl increases with increasing volume fraction of Nisb3Al in the in-situ composites according to a general formula Ksb{Ivc}=6.1+0.7Vsbsp{d}{0.75} (Mpasurdm) (where Vsb{d} - volume % of Nisb3Al). In some Nisb3Al/NiAl composite alloys the Nisb5Alsb3 fine particles are formed (so-called "mat-like structure") which exhibits very high Vickers microhardness ({≈}690 kg/mmsp2). The significant yield strength of {≈}1150 kg/mmsp2 in the aged Nisb{65.9}Alsb{34.1} in-situ composite is also attributed to this needle-like structure of Nisb5Asb3. It is worth pointing out that a very high yield strength (sigmasb{YS}≈1150MPa) is combined in aged alloys with a reasonable value of fracture toughness ({≈}13 MPasurdm). It indicates that such a new promising alloy can be yielded by an economic and simple casting method followed by a proper heat treatment as shown in this research. The highest Weibull's modulus m ≈ 23.8 for Nisb{63.7}Alsb{36.3}\\ ({≈}17 vol.% Nisb3Al) indicates that this alloy is a very reliable material for engineering design even with lower fracture toughness value (Ksb{Ivm}sp{W}≈8 MPasurdm). The lowest Weibull's modulus m ≈ 5.8 for Nisb{73.2}Alsb{26.8}\\ ({≈}99 vol.% Nisb3Al) means that the fracture toughness of this alloy is highly variable and no single value for Ksb{Ivm}sp{W} be assigned easily.

  14. On improving the fracture toughness of a NiAl-based alloy by mechanical alloying

    Science.gov (United States)

    Kostrubanic, J.; Koss, D. A.; Locci, I. E.; Nathal, M.

    1991-01-01

    Mechanical alloying (MA) has been used to process the NiAl-based alloy Ni-35Al-20Fe, such that a fine-grain (about 2 microns) microstructure is obtained through the addition of 2 vol pct Y2O3 particles. When compared to a conventionally processed, coarse-grained (about 28 microns) Ni-35-20 alloy without the Y2O3 particles, the MA alloy exhibits two to three times higher fracture toughness values, despite a 50-percent increase in yield strength. Room-temperature K(O) values as high as 34 MPa sq rt m are observed, accompanied by a yield strength in excess of 1100 MPa. Fractography confirms a change in fracture characteristics of the fine-grained MA alloy.

  15. The CCT diagrams of ultra low carbon bainitic steels and their impact toughness properties

    International Nuclear Information System (INIS)

    Lis, A.K.; Lis, J.; Jeziorski, L.

    1998-01-01

    The CCT diagrams of ULCB N i steels, HN3MV, HN3MVCu having 5.1% Ni and 3.5% Ni and Cu bearing steels; HN3M1.5Cu, HSLA 100 have been determined. The reduced carbon concentration in steel, in order to prevent the formation of cementite, allowed for using nickel, manganese, chromium and molybdenum to enhance hardenability and refinement of the bainitic microstructures by lowering B S temperature. Copper and microadditions of vanadium and niobium are successfully used for precipitation strengthening of steel both in thermomechanically or heat treated conditions. Very good fracture toughness at low temperatures and high yield strength properties of HN3MVCu and HN3MV steels allowed for fulfillment of the requirements for steel plates for pressure vessels and cryogenic applications. (author)

  16. Investigations on the fracture toughness of austempered ductile iron alloyed with chromium

    Energy Technology Data Exchange (ETDEWEB)

    Rao, P. Prasad; Putatunda, Susil K

    2003-04-15

    An investigation was carried out to examine the influence of chromium content on the plane strain fracture toughness of austempered ductile iron (ADI). ADIs containing 0, 0.3 and 0.5 wt.% chromium were austempered over a range of temperatures to produce different microstructures. The microstructures were characterized by optical microscopy and X-ray diffraction. Plane strain fracture toughness of all these materials was determined and correlated with microstructure and chromium content. The chromium content was found to influence the fracture toughness through its influence on the processing window. Since the chromium addition shifts the processing window to shorter durations, the higher chromium alloys at higher austempering temperatures tend to fall outside of the processing window, resulting in less than optimum microstructure and inferior fracture toughness. A small chromium addition of 0.3 wt.% was found to be beneficial for the fracture toughness of ADI.

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

    International Nuclear Information System (INIS)

    Chipperfield, C.G.

    1978-01-01

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

  18. 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.

  19. Competitive Performance Correlates of Mental Toughness in Tennis: A Preliminary Analysis.

    Science.gov (United States)

    Cowden, Richard G

    2016-08-01

    This study investigated relationships between mental toughness and measures of competitive performance in tennis. Forty-three male (N = 25) and female (N = 18) players (M age = 13.6 years, SD = 2.4) completed the mental toughness inventory, and the point-by-point outcomes recorded during a competitive tennis match (singles) were used to generate performance indices for each athlete. The results indicated that mental toughness was associated with several, but not all, macro, micro, and critical moment performance indices. The findings suggest mental toughness may contribute to successful performance during tennis competition, although the importance of the construct appears to depend depend on specific match situations. Future mental toughness research should consider a range of factors related to sport performance, including athletes' and opponents' physical, technical, and tactical abilities. © The Author(s) 2016.

  20. Mode I fracture toughness of carbon-glass/epoxy interply hybrid composites

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Ha Na; Kim, Yon Jig [Chonbuk National University, Jeonju (Korea, Republic of)

    2015-05-15

    In this study, the fracture toughness of carbon-glass fiber reinforced epoxy interply hybrid composite was investigated. In this experiment, the interply hybrid composites were manufactured using a vacuum-assisted resin transfer molding (VARTM) process. The fracture toughness of the interply hybrid composites was decreased with increasing the number of glass fabrics. The decrease in fracture toughness with an increase in the glass fiber content can be expressed in the form of a linear equation. Test results showed that the arrangement of fiber significantly influences the fracture toughness of the composite material. Glass fiber was effective against improving the fracture toughness of the hybrid composite when the glass fibers are dispersed by multi layers rather than a single layer.