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

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

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.

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

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.

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.

Ion implantation and fracture toughness of ceramics

International Nuclear Information System (INIS)

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

1985-01-01

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

Toughness behaviour of tungsten-carbide-cobalt alloys

International Nuclear Information System (INIS)

Sigl, L.S.

1985-05-01

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

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.

Fracture toughness measurements with subsize disk compact specimens

International Nuclear Information System (INIS)

Alexander, D.J.

1994-01-01

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

46 CFR 54.05-16 - Production toughness testing.

Science.gov (United States)

2010-10-01

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

Mindfulness and mental toughness among provincial adolescent ...

African Journals Online (AJOL)

Kathryn van Boom

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

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

Science.gov (United States)

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

2016-09-01

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

Fracture toughness of Al-Cr alloys with minor additions

International Nuclear Information System (INIS)

Datta, S.; Banerjee, M.K.

2000-01-01

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

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)

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

Makiguchi Tsunesaburo and Language, Value-Creative Composition Instruction, and the Geography of Identity in Community Studies: A Response to Politicized Imagining and Ineffective Critical Approaches

Science.gov (United States)

Goulah, Jason

2013-01-01

In this article, the author examines Makiguchi Tsunesaburo's philosophy and practice of human geography ("jinsei chirigaku"), community studies ("kyodoka"), and composition instruction based on "value-creating pedagogy" ("soka kyoikugaku") for thinking through and responding to two competing trends…

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

Energy Technology Data Exchange (ETDEWEB)

Frieling, Gerd; Bracke, Guido

2013-12-15

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

ITOUGH2: Solving TOUGH inverse problems

Energy Technology Data Exchange (ETDEWEB)

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

1995-03-01

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

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

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.

Fracture toughness of irradiated and recovered vessel steels

International Nuclear Information System (INIS)

Perosanz, F.; Lapena, J.

1998-01-01

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

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).

A statistical study on fracture toughness data of Japanese RPVS

International Nuclear Information System (INIS)

Sakai, Y.; Ogura, N.

1987-01-01

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

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

Use of TOUGH2 on small computers

Energy Technology Data Exchange (ETDEWEB)

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

1995-03-01

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

Validity of fracture toughness determined with small bend specimens

International Nuclear Information System (INIS)

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

1994-02-01

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

Fracture toughness of Dy123 low porosity bulks at liquid nitrogen temperature

International Nuclear Information System (INIS)

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

2011-01-01

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

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.

Interlaminar fracture toughness for composite materials

International Nuclear Information System (INIS)

Lee, Kang Yong; Kwon, Soon Man

1991-01-01

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

High-temperature fracture toughness of duplex microstructures

International Nuclear Information System (INIS)

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

1996-01-01

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

Fracture toughness of dentin/resin-composite adhesive interfaces.

Science.gov (United States)

Tam, L E; Pilliar, R M

1993-05-01

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

More progress on tough graphs -- The Y2K report

NARCIS (Netherlands)

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

2000-01-01

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

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

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

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)

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

International Nuclear Information System (INIS)

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

2010-01-01

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

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.

Toughness degradation evaluation of low alloyed steels by electrical resistivity

Energy Technology Data Exchange (ETDEWEB)

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

1997-09-01

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

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).

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

International Nuclear Information System (INIS)

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

2012-01-01

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

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.

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)

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

International Nuclear Information System (INIS)

Shibata, Akira; Takada, Fumiki

2007-03-01

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

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

International Nuclear Information System (INIS)

Oldfield, W.

1981-01-01

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

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

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

Finite Element Simulation of Fracture Toughness Test

International Nuclear Information System (INIS)

Chu, Seok Jae; Liu, Cong Hao

2013-01-01

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

The toughness of secondary cell wall and woody tissue

OpenAIRE

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

1997-01-01

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

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...

Microstructure and fracture toughness of Mn-stabilized cubic titanium trialuminide

Science.gov (United States)

Zbroniec, Leszek Ireneusz

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

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

International Nuclear Information System (INIS)

Miura, Yasufumi

2016-01-01

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

Evaluation of fracture toughness of ductile cast iron for casks

International Nuclear Information System (INIS)

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

1988-01-01

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

Fracture toughness of ferritic alloys irradiated at FFTF

International Nuclear Information System (INIS)

Huang, F.H.

1986-05-01

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

46 CFR 57.06-5 - Production toughness testing.

Science.gov (United States)

2010-10-01

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

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.

Strength-toughness requirements for thick walled high pressure vessels

International Nuclear Information System (INIS)

Kapp, J.A.

1990-01-01

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

Rock Fracture Toughness Study Under Mixed Mode I/III Loading

Science.gov (United States)

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

2017-07-01

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

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.

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.

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

Science.gov (United States)

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

2014-01-01

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

A statistical approach to the prediction of pressure tube fracture toughness

International Nuclear Information System (INIS)

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

2008-01-01

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

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

International Nuclear Information System (INIS)

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

1996-01-01

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

Biaxial loading effects on fracture toughness of reactor pressure vessel steel

International Nuclear Information System (INIS)

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

1995-03-01

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

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

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

International Nuclear Information System (INIS)

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

2013-01-01

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

Summary of pre and post-processors for V-TOUGH

International Nuclear Information System (INIS)

Daveler, S.

1995-08-01

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

Fracture toughness of intermetallics using a micro-mechanical probe

International Nuclear Information System (INIS)

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

1993-01-01

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

A New Method for Evaluating the Indentation Toughness of Hardmetals

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Prem C. Jindal

2018-05-01

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

Fracture toughness and strength change of neutron-irradiated ceramic materials

International Nuclear Information System (INIS)

Dienst, W.; Zimmermann, H.

1994-01-01

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

New unified fracture toughness estimation scheme for structural integrity assessment

Energy Technology Data Exchange (ETDEWEB)

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

1999-12-31

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

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.

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.

Strong, tough and stiff bioinspired ceramics from brittle constituents

Science.gov (United States)

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

2014-05-01

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

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

International Nuclear Information System (INIS)

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

1993-01-01

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

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

International Nuclear Information System (INIS)

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

1991-01-01

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

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

Science.gov (United States)

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

2013-03-01

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

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

International Nuclear Information System (INIS)

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

1994-01-01

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

Developing Mental Toughness: Lessons from Paralympians

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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

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

Pie technique of LWR fuel cladding fracture toughness test

International Nuclear Information System (INIS)

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

2006-01-01

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

Fracture toughness evaluations of TP304 stainless steel pipes

International Nuclear Information System (INIS)

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

1997-02-01

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

Application of ISRM testing methods to fracture toughness testing of graphite

International Nuclear Information System (INIS)

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

1987-01-01

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

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)

Coupling of the reservoir simulator TOUGH and the wellbore simulator WFSA

Energy Technology Data Exchange (ETDEWEB)

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

1995-03-01

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

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.

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

Directory of Open Access Journals (Sweden)

Dena Sadeghi Bahmani

2016-08-01

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

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

Solving iTOUGH2 simulation and optimization problems using the PEST protocol

Energy Technology Data Exchange (ETDEWEB)

Finsterle, S.A.; Zhang, Y.

2011-02-01

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

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.

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.

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

Science.gov (United States)

Jossey-Bass, An Imprint of Wiley, 2008

2008-01-01

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

The toughness of split graphs

NARCIS (Netherlands)

Woeginger, G.J.

1998-01-01

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

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

International Nuclear Information System (INIS)

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

2011-01-01

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

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

International Nuclear Information System (INIS)

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

1994-01-01

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

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

International Nuclear Information System (INIS)

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

1979-01-01

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

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.

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.

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.

The effect of specimen and flaw dimensions on fracture toughness

International Nuclear Information System (INIS)

Nevalainen, M.J.

1997-06-01

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

Fracture toughness evaluation of Eurofer'97 by testing small specimens

International Nuclear Information System (INIS)

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

2006-01-01

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

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

Science.gov (United States)

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

2011-02-01

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

Fracture toughness behavior of irradiated stainless steel in PWR systems

Energy Technology Data Exchange (ETDEWEB)

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

2007-07-01

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

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

Directory of Open Access Journals (Sweden)

Y. L. Chen

2011-01-01

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

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)

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

International Nuclear Information System (INIS)

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

2007-01-01

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

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.

Fracture toughness calculation using dynamic testing

International Nuclear Information System (INIS)

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

1998-01-01

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

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

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

Directory of Open Access Journals (Sweden)

Elisa Borowski

2015-06-01

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

Fracture toughness properties of similar and dissimilar electron beam welds

International Nuclear Information System (INIS)

Kocak, M.; Junghans, E.

1994-01-01

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

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

Science.gov (United States)

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

2008-01-01

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

Fracture toughness behavior and its analysis on nuclear pressure vessel steels

Energy Technology Data Exchange (ETDEWEB)

Iwadate, Tadao; Tanaka, Yasuhiko; Ono, Shin-ichi; Tsukada, Hisashi [Japan Steel Works Ltd., Muroran, Hokkaido. Muroran Plant

1983-02-01

A drop weight J sub(Id) testing machine has been developed successfully, by which the multiple specimen J resistance curve test technique can be applied to measure the fracture toughness. In this study, the use of a small size round compact tension (RCT) specimen for measuring the fracture toughness J sub(Ic) or J sub(Id) of the nuclear pressure vessel steels is recommended and confirmed for the surveillance tests. The static and dynamic fracture toughness of ASTM A508 C 1.2, A508 C 1.3 and A533 Gr.B C 1.1 steels in the wide range of temperature including the upper shelf have been measured and their behavior has been analysed. The fracture toughness behavior under various strain rates and in a wide temperature range can be explained by the behavior of stretched zone formation preceding the crack initiation. The scatter of K sub(J) values in the transition range is caused by the amount of crack extension contained in the specimens. In this paper, the method to obtain the fracture toughness equivalent to the K sub(Ic) from the K sub(J) value is also presented.

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

International Nuclear Information System (INIS)

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

2012-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2012-04-30

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

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.

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

International Nuclear Information System (INIS)

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

2016-01-01

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

Fracture toughness of China low activation martensitic (CLAM) steel at room temperature

Energy Technology Data Exchange (ETDEWEB)

Li, Kunfeng [University of Science and Technology of China, Hefei, Anhui 230027 (China); Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Liu, Shaojun, E-mail: shaojun.liu@fds.org.cn [Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Huang, Qunying [University of Science and Technology of China, Hefei, Anhui 230027 (China); Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Xu, Gang; Jiang, Siben [Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui 230031 (China)

2014-04-15

Highlights: • The fracture toughness of CLAM steel at room temperature is 417.9 kJ/m{sup 2} measured by unloading compliance method according to the ASTM E1820-11. • The fracture toughness of CLAM steel at room temperature can be calculated on the basis of the fractal dimensions measured under plane strain conditions. The calculated result and relative error for this experiment are 454.6 kJ/m{sup 2} and 8.78% respectively. • The calculation method could be used to estimate the fracture toughness of materials with analysis of the fracture surface. - Abstract: The fracture toughness (J{sub IC}) of China low activation martensitic (CLAM) steel was tested at room temperature through the compact tension specimen, the result is 417.9 kJ/m{sup 2}, which is similar to the JLF-1 at same experimental conditions. The microstructural observation of the fracture surface shows that the fracture mode is a typical ductile fracture. Meanwhile, the fracture toughness is also calculated on the basis of the fractal dimension and the calculated result is 454.6 kJ/m{sup 2}, which is consistent well with the experimental result. This method could be used to estimate the fracture toughness of materials by analyzing of the fracture surface.

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.

Optimization design of strong and tough nacreous nanocomposites through tuning characteristic lengths

Science.gov (United States)

Ni, Yong; Song, Zhaoqiang; Jiang, Hongyuan; Yu, Shu-Hong; He, Linghui

2015-08-01

How nacreous nanocomposites with optimal combinations of stiffness, strength and toughness depend on constituent property and microstructure parameters is studied using a nonlinear shear-lag model. We show that the interfacial elasto-plasticity and the overlapping length between bricks dependent on the brick size and brick staggering mode significantly affect the nonuniformity of the shear stress, the stress-transfer efficiency and thus the failure path. There are two characteristic lengths at which the strength and toughness are optimized respectively. Simultaneous optimization of the strength and toughness is achieved by matching these lengths as close as possible in the nacreous nanocomposite with regularly staggered brick-and-mortar (BM) structure where simultaneous uniform failures of the brick and interface occur. In the randomly staggered BM structure, as the overlapping length is distributed, the nacreous nanocomposite turns the simultaneous uniform failure into progressive interface or brick failure with moderate decrease of the strength and toughness. Specifically there is a parametric range at which the strength and toughness are insensitive to the brick staggering randomness. The obtained results propose a parametric selection guideline based on the length matching for rational design of nacreous nanocomposites. Such guideline explains why nacre is strong and tough while most artificial nacreous nanocomposites aere not.

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.)

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

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

International Nuclear Information System (INIS)

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

1991-01-01

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

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

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.

An overview of EXTOOL: An analysis tool for V-TOUGH and NUFT

International Nuclear Information System (INIS)

Daveler, S.

1995-08-01

Several post-processors have been used in connection with V-TOUGH. Initially, a sequence of utilities were used to extract and plot V-TOUGH information. This changed in 1991 as a new post-processor, EXTOOL, was developed. Currently, EXTOOL, is the main post-processor for the modeling codes V-TOUGH and NUFT. In the following sections, a history of V-TOUGH post-processing is discussed along with an overview of EXTOOL. This overview describes some of Extool's capabilities and suggests reasons for using this code instead of another postprocessor. More detailed information on EXTOOL can be found in the Extool User's Manual and the Extool Programmer's Guide. Both these manuals are drafts, and can be requested by sending email to daveler2 at sign llnl.gov

Foundation of the Outstanding Toughness in Biomimetic and Natural Spider Silk.

Science.gov (United States)

Anton, Arthur Markus; Heidebrecht, Aniela; Mahmood, Nasir; Beiner, Mario; Scheibel, Thomas; Kremer, Friedrich

2017-12-11

Spider dragline silk is distinguished through the highest toughness of all natural as well as artificial fiber materials. To unravel the toughness's molecular foundation and to enable manufacturing biomimetic analogues, we investigated the morphological and functional structure of recombinant fibers, which exhibit toughness similar to that of the natural template, on the molecular scale by means of vibrational spectroscopy and on the mesoscale by X-ray scattering. Whereas the former was used to identify protein secondary structures and their alignment in the natural as well as artificial silks, the latter revealed nanometer-sized crystallites on the higher structural level. Furthermore, a spectral red shift of a crystal-specific absorption band demonstrated that macroscopically applied stress is directly transferred to the molecular scale, where it is finally dissipated. Concerning this feature, both the natural as well as the biomimetic fibers are almost indistinguishable, giving rise to the toughness of both fiber materials.

Mental Toughness Moderates Social Loafing in Cycle Time-Trial Performance

Science.gov (United States)

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

2016-01-01

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

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.

Fracture toughness evaluation in the transition region of reactor pressure vessel steel

International Nuclear Information System (INIS)

Onizawa, K.; Suzuki, M.

1995-01-01

The fracture toughness (K jc and Jc) values at the cleavage fracture initiation in the transition region of a RPV steel were investigated using mainly precracked Charpy specimens. A conventional statistical approach and a fractographic study were applied to analyze the scatter of the fracture toughness values from precracked Charpy specimens. The material used was an ASTM A533B class 1 steel, which was designated as an IAEA correlation monitor material, JRQ. A lower bound transition curve of the fracture toughness for unirradiated condition was determined by the 5% confidence limit from the Weibull and fractographic analyses. The lower bound transition curve after irradiation was evaluated based on the statistics of unirradiated specimens. The results indicated that the shift of the fracture toughness transition curbe were somewhat larger than the Charpy 41J transition temperature. The parameters to determine the lower bound toughness such as the Weibull slope and the amount of ductile crack growth are discussed. The results are also compared with a model based on weakest link theory. (author). 12 refs, 12 figs, 5 tabs

Formation of tough composite joints

International Nuclear Information System (INIS)

Brun, M.K.

1997-05-01

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

Development of the present reference fracture toughness curves in the ASME nuclear code

International Nuclear Information System (INIS)

Yukawa, S.; Merkle, J.G.

1984-01-01

Since the early 1970's, the Sections of the ASME Boiler and Pressure Vessel Code concerned with nuclear power plant components have included fracture mechanics procedures to analyze the effects of postulated or detected flaws. These procedures are contained in Appendix G of Section III and in Appendix A of Section XI of the Code. Specifically, Appendix G procedures are concerned with designing for protection against nonductile failures while Appendix A procedures are for evaluating the disposition of flaws detected during in-service inspection. An important element of the procedures is the inclusion of recommended material fracture toughness values. This paper describes the origin and development of these recommended fracture toughness values. Since these values appear in the Code in a graphical format, the values are often referred to as reference toughness curves. In the context of Code terminology, reference toughness means the allowable values of fracture toughness for the materials of concern that can be used in conjunction with the analytical procedures of Appendices G and A. The paper discusses the basis and rationale underlying the original formulation of these reference toughness curves and the modifications incorporated into them in the course of their adoption into the Code

Method to increase the toughness of aluminum-lithium alloys at cryogenic temperatures

Science.gov (United States)

Sankaran, Krishnan K. (Inventor); Sova, Brian J. (Inventor); Babel, Henry W. (Inventor)

2006-01-01

A method to increase the toughness of the aluminum-lithium alloy C458 and similar alloys at cryogenic temperatures above their room temperature toughness is provided. Increasing the cryogenic toughness of the aluminum-lithium alloy C458 allows the use of alloy C458 for cryogenic tanks, for example for launch vehicles in the aerospace industry. A two-step aging treatment for alloy C458 is provided. A specific set of times and temperatures to age the aluminum-lithium alloy C458 to T8 temper is disclosed that results in a higher toughness at cryogenic temperatures compared to room temperature. The disclosed two-step aging treatment for alloy 458 can be easily practiced in the manufacturing process, does not involve impractical heating rates or durations, and does not degrade other material properties.

Stainless steel submerged arc weld fusion line toughness

International Nuclear Information System (INIS)

Rosenfield, A.R.; Held, P.R.; Wilkowski, G.M.

1995-04-01

This effort evaluated the fracture toughness of austenitic steel submerged-arc weld (SAW) fusion lines. The incentive was to explain why cracks grow into the fusion line in many pipe tests conducted with cracks initially centered in SAWS. The concern was that the fusion line may have a lower toughness than the SAW. It was found that the fusion line, Ji. was greater than the SAW toughness but much less than the base metal. Of greater importance may be that the crack growth resistance (JD-R) of the fusion line appeared to reach a steady-state value, while the SAW had a continually increasing JD-R curve. This explains why the cracks eventually turn to the fusion line in the pipe experiments. A method of incorporating these results would be to use the weld metal J-R curve up to the fusion-line steady-state J value. These results may be more important to LBB analyses than the ASME flaw evaluation procedures, since there is more crack growth with through-wall cracks in LBB analyses than for surface cracks in pipe flaw evaluations

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.

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

International Nuclear Information System (INIS)

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

1977-01-01

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

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

Fracture toughness in nuclear waste glasses and ceramics: environmental and radiation effects

International Nuclear Information System (INIS)

Weber, W.J.; Matzke, H.J.

1986-03-01

The effects of atmospheric moisture and radiation damage on fracture properties of nuclear waste glasses and ceramics was investigated by indentation techniques. In nuclear waste glasses, atmospheric moisture has no measurable effect on hardness but decreases the fracture toughness; radiation damage, on the other hand, decreased the hardness and increased the fracture toughness. In nuclear ceramics, self-radiation damage from alpha decay decreased the hardness and elastic modules; the fracture toughness increased with dose to a broad maximum and then decreased slightly with further increases in dose

Fracture toughness of irradiated stainless steel alloys

International Nuclear Information System (INIS)

Mills, W.J.

1986-01-01

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

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)

Dynamic fracture toughness testing of structural steels

International Nuclear Information System (INIS)

Debel, C.P.

1978-01-01

Two candidate test methods aimed at producing materials properties of interest in connection with crack arrest assessments are currently under evaluation. These methods and the significance of the results are described. The quasi-static as well as the dynamic fracture toughness of a plain C-Mn steel in the as-quenched and tempered condition have been examined at temperatures between -115 0 C and the ambient temperature. Wedge-loaded duplex DCB-specimens were used in dynamic tests. The crack extension velocity was measured using a surface deposited grid and a registration circuit based on TTL-electronics. The toughness transition-temperature at quasi-static loading rate is found to be low; but during dynamic crack-extension a substantial shift of the transition-region to higher temperatures is produced, and fast fracture was obtained even at ambient temperature. Even though the dynamic fracture toughness Ksub(ID) increases with temperature, it decreases with increasing crack-extension velocity at a given temperature and the rate of decrease with respect to crack-extension velocity seems to be independent of temperature. Ksub(ID) appears to be insensitive to heat treatments. Test results indicate insufficient load-train stiffness, and problems due to crack branching were encountered. (author)

Fracture toughness testing on ferritic alloys using the electropotential technique

International Nuclear Information System (INIS)

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

1981-01-01

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

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.

On the Relationship of Hemingway's Tough Guys and the China Dream

Institute of Scientific and Technical Information of China (English)

Qin Chenghua

2017-01-01

Tough guys are a series of literary characters in Hemingway's works.The China Dream is a dream that calls on all Chinese people to be hard-working and aims at full development of the self and the nation.To realize the China Dream,hard work,development and environment protection are essential factors.Hemingway's tough guys are famous for their dedication to work and strong willpower in overcoming difficulties and hardships.Some of their reflections are also pertaining to environmental issues.All of these are good references in realizing the China Dream.Thus,to re-read Hemingway's stories about tough guys nowadays is important for Chinese reading pubhc.

Fracture Toughness (KIC) of Lithography Based Manufactured Alumina Ceramic

Science.gov (United States)

Nindhia, T. G. T.; Schlacher, J.; Lube, T.

2018-04-01

Precision shaped ceramic components can be obtained by an emerging technique called Lithography based Ceramic Manufacturing (LCM). A green part is made from a slurry consisting of a ceramic powder in a photocurable binder with addition of dispersant and plasticizer. Components are built in a layer–by-layer way by exposing the desired cross- sections to light. The parts are subsequently sintered to their final density. It is a challenge to produce ceramic component with this method that yield the same mechanical properties in all direction. The fracture toughness (KIc) of of LCM-alumina (prepared at LITHOZ GmbH, Austria) was tested by using the Single-Edge-V-Notched Beam (SEVNB) method. Notches are made into prismatic bend-bars in all three direction X, Y and Z to recognize the value of fracture toughness of the material in all three directions. The microstructure was revealed with optical microscopy as well as Scanning Electron Microscopy (SEM). The results indicate that the fracture toughness in Y-direction has the highest value (3.10 MPam1/2) that is followed by the one in X-direction which is just a bit lower (2.90 MPam1/2). The Z-direction is found to have a similar fracture toughness (2.95 MPam1/2). This is supported by a homogeneous microstructure showing no hint of the layers used during production.

Dependence of fracture toughness of molybdenum laser welds on processing parameters and in-situ oxygen gettering

International Nuclear Information System (INIS)

Pope, L.E.; Jellison, J.L.

1980-01-01

Fracture toughness properties have been determined for laser welds in different grades of molybdenum. The fracture toughness of welds in sintered molybdenum was consistently less than the fracture toughness of welds in vacuum arc remelted molybdenum. These differences cannot be attributed to oxygen content, since the oxygen level was nominally the same for all grades of molybdenum examined in this program. Alloy additions of titanium by means of physically deposited coatings significantly improved the fracture toughness of welds in sintered molybdenum, whereas titanium additions to welds in vacuum arc remelted molybdenum decreased the fracture toughness slightly. Pulsed laser welds exhibited fine columnar structures and, in the case of sintered molybdenum, superior fracture toughness when compared with continuous wave laser welds. 6 figures, 3 tables

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.)

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.

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

International Nuclear Information System (INIS)

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

1993-01-01

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

Four Takes on Tough Times

Science.gov (United States)

Rebell, Michael A.; Odden, Allan; Rolle, Anthony; Guthrie, James W.

2012-01-01

Educational Leadership talks with four experts in the fields of education policy and finance about how schools can weather the current financial crisis. Michael A. Rebell focuses on the recession and students' rights; Allan Odden suggests five steps schools can take to improve in tough times; Anthony Rolle describes the tension between equity and…

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.

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

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

Influence of texture on fracture toughness of zircaloy cladding

Energy Technology Data Exchange (ETDEWEB)

Grigoriev, V. [Studsvik Material AB, Nykoeping (Sweden); Andersson, Stefan [Royal Inst. of Tech., Stockholm (Sweden)

1997-06-01

The correlation between texture and fracture toughness of Zircaloy 2 cladding has been investigated in connection with axial cracks in fuel rods. The texture of the cladding determines the anisotropy of plasticity of the cladding which, in turn, should influence the strain conditions at the crack-tip. Plastic strains in the cladding under uniaxial tension were characterised by means of the anisotropy constants F, G and H calculated according to Hill`s theory. Test temperatures between 20 and 300 deg C do not influence the F, G and H values. Any significant effect of hydrogen (about 500 wtppm) on the anisotropy constants F, G and H has not been revealed at a test temperature of 300 deg C. The results, obtained for stress-relieved and recrystallized cladding with different texture, show an obvious influence of texture on the fracture toughness of Zircaloy cladding. A higher fracture toughness has been found for cladding with more radial texture. With a 2 page summary in Swedish. 32 refs, 18 figs.

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)

Fracture toughness evaluation of small notched specimen in consideration of notch effect and loading rate

International Nuclear Information System (INIS)

Lee, Baik Woo; Kwon, Dong Il; Jang, Jae Il

2000-01-01

Notch effect and loading rate dependency on fracture toughness were considered when evaluating fracture toughness of small notched specimens using the instrumented impact test. Notch effect was analyzed into stress redistribution effect and stress relaxation with a viewpoint of stress triaxiality. Stress redistribution effect was corrected by introducing effective crack length, which was the sum of actual crack length and plastic zone size. Stress relaxation effect was also corrected using elastic stress concentration factor, which would decrease if plastic deformation occurred. As a result, corrected fracture toughness of the notched specimen was very consistent with the reference fracture toughness obtained using precracked specimen. In addition, limiting notch root radius, below which fracture toughness was independent of notch radius, was observed and discussed. Loading rate dependency on fracture toughness, which was obtained from the static three point bending test and the instrumented impact test, was also discussed with stress field in plastic zone ahead of a notch and fracture based on stress control mechanism. (author)

Air-tough: A fully 3-dimensional linking of atmosphere with soil using eddy diffusivity concept and V-TOUGH

Energy Technology Data Exchange (ETDEWEB)

Montazer, P. [Multimedia Environmental Technology, Inc., Newport Beach, CA (United States)

1995-03-01

In arid climates, evapotranspiration is a strongly-coupled thermodynamic process that is controlled by the interaction of the atmospheric boundary layer and the upper soil surface. Simulation of this process requires a fully-coupled thermodynamic multi-phase fluid-flow and energy-transport code. Such a code was developed in a previous investigation using V-TOUGH. The resulting efficient computer code, A-TOUGH, simulates the effect of dynamic atmospheric fluctuations on vapor movement between the soil and the atmosphere and the resulting moisture movement in the soil. However, the coupling between the atmosphere and soil employed eddy diffusivity which was only a function of time and not a function of space. In the present study the code is extended to allow spatial as well as temporal variation of eddy diffusivity.

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

Fracture Toughness Evaluation of Kori-1 RPV Beltline Weld for a Long-Term Operation

International Nuclear Information System (INIS)

Lee, Bong-Sang; Kim, Min-Chul; Ahn, Sang-Bok; Kim, Byung-Chul; Hong, Jun-Hwa

2007-01-01

Irradiation embrittlement of RPV (reactor pressure vessel) material is the most important aging issue for a long-term operation of nuclear power plants. KORI unit 1, which is the first PWR in Korea, is approaching its initial licensing life of 30 years. In order to operate the reactor for another 10 years and more, it should be demonstrated that the irradiation embrittlement of the reactor will be adequately managed by ensuring that the fracture toughness properties have a certain level of the safety margin. The current regulation requires Charpy V-notch impact data through conventional surveillance tests. It is based on the assumption that Charpy impact test results are well correlated with the fracture toughness properties of many engineering steels. However, Charpy V-notch impact data may not be adequate to estimate the fracture toughness of certain materials, such as Linde 80 welds. During the last decade, a tremendous number of fracture toughness data on many RPV steels have been produced in accordance with the new standard test method, the so-called master curve method. ASTM E1921 represents a revolutionary advance in characterizing fracture toughness of RPV steels, since it permits establishing the ductile to brittle transition portion of the fracture toughness curve with direct measurements on a relatively small number of relatively small specimens, such as pre-cracked Charpy specimens. Actual fracture toughness data from many different RPV steels revealed that the Charpy test estimations are generally conservative with the exception of a few cases. Recent regulation codes in USA permit the master curve fracture toughness methodology in evaluating an irradiation embrittlement of commercial nuclear reactor vessels

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

International Nuclear Information System (INIS)

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

1997-01-01

The current methodology for determination of fracture toughness of irradiated reactor pressure vessel (RPV) steels is based on the upward temperature shift of the American Society of Mechanical Engineers (ASME) K Ic curve from either measurement of Charpy impact surveillance specimens or predictive calculations based on a database of Charpy impact tests from RPV surveillance programs. Currently, the provisions for determination of the upward temperature shift of the curve due to irradiation are based on the Charpy V-notch (CVN) 41-J shift, and the shape of the fracture toughness curve is assumed to not change as a consequence or irradiation. The ASME curve is a function of test temperature (T) normalized to a reference nit-ductility temperature, RT NDT , namely, T-RT NDT . That curve was constructed as the lower boundary to the available K Ic database and, therefore, does not consider probability matters. Moreover, to achieve valid fracture toughness data in the temperature range where the rate of fracture toughness increase with temperature is rapidly increasing, very large test specimens were needed to maintain plain-strain, linear-elastic conditions. Such large specimens are impractical for fracture toughness testing of each RPV steel, but the evolution of elastic-plastic fracture mechanics has led to the use of relatively small test specimens to achieve acceptable cleavage fracture toughness measurements, K Jc , in the transition temperature range. Accompanying this evolution is the employment of the Weibull distribution function to model the scatter of fracture toughness values in the transition range. Thus, a probabilistic-based bound for a given data population can be made. Further, it has been demonstrated by Wallin that the probabilistic-based estimates of median fracture toughness of ferritic steels tend to form transition curves of the same shape, the so-called ''master curve'', normalized to one common specimen size, namely the 1T [i.e., 1.0-in

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

Science.gov (United States)

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

2018-03-01

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

Study of cladding toughness in a pressure vessel steel water reactor

International Nuclear Information System (INIS)

Soulat, P.; Al Mundheri, M.

1984-12-01

Toughness of cladding and pressure vessel steel were determined at different temperatures in order to appreciate the participation of cladding resistance against crack propagation. The toughness of cladding is comparable with typical results on austenitic welds. The test on covered CT specimens shows the possibility of having a relatively good prevision of the behaviour of a coated structure

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

Science.gov (United States)

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

2018-05-01

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

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

Estimation of fracture toughness of cast stainless steels during thermal aging in LWR systems

International Nuclear Information System (INIS)

Chopra, O.K.

1991-06-01

A procedure and correlations are presented for predicting the change in fracture toughness of cast stainless steel components due to thermal aging during service in light water rectors (LWRs) at 280--330 degrees C (535--625 degrees F). The fracture toughness J-R curve and Charpy-impact energy of aged cast stainless steels are estimated from known mineral in formation. Fracture toughness of a specific cast stainless steel is estimated from the extent and kinetics of thermal embrittlement. The extent of thermal embrittlement is characterized by the room-temperature ''normalized'' Charpy-impact energy. A correlation for the extent of embrittlement at ''saturation,'' i.e., the minimum impact energy that would be achieved for the material after long-term aging, is given in terms of a material parameter, Φ, which is determined from the chemical composition. The fracture toughness J-R curve for the material is then obtained from correlations between room-temperature Charpy-impact energy and fracture toughness parameters. Fracture toughness as a function of time and temperature of reactor service is estimated from the kinetics of thermal embrittlement, which is determined from chemical composition. A common ''lower-bound'' J-R curve for cast stainless steels with unknown chemical composition is also defined for a given material specification, ferrite content, and temperature. Examples for estimating impact strength and fracture toughness of cast stainless steel components during reactor service are describes. 24 refs., 39 figs., 2 tabs

Estimation of fracture toughness of cast stainless steels during thermal aging in LWR systems

Energy Technology Data Exchange (ETDEWEB)

Chopra, O.K. (Argonne National Lab., IL (USA))

1991-06-01

A procedure and correlations are presented for predicting the change in fracture toughness of cast stainless steel components due to thermal aging during service in light water rectors (LWRs) at 280--330{degrees}C (535--625{degrees}F). The fracture toughness J-R curve and Charpy-impact energy of aged cast stainless steels are estimated from known mineral in formation. Fracture toughness of a specific cast stainless steel is estimated from the extent and kinetics of thermal embrittlement. The extent of thermal embrittlement is characterized by the room-temperature normalized'' Charpy-impact energy. A correlation for the extent of embrittlement at saturation,'' i.e., the minimum impact energy that would be achieved for the material after long-term aging, is given in terms of a material parameter, {Phi}, which is determined from the chemical composition. The fracture toughness J-R curve for the material is then obtained from correlations between room-temperature Charpy-impact energy and fracture toughness parameters. Fracture toughness as a function of time and temperature of reactor service is estimated from the kinetics of thermal embrittlement, which is determined from chemical composition. A common lower-bound'' J-R curve for cast stainless steels with unknown chemical composition is also defined for a given material specification, ferrite content, and temperature. Examples for estimating impact strength and fracture toughness of cast stainless steel components during reactor service are describes. 24 refs., 39 figs., 2 tabs.

Photoelastic stress analysis assisted evaluation of fracture toughness in hydrothermally aged epoxies

Directory of Open Access Journals (Sweden)

G. Pitarresi

2014-10-01

Full Text Available The present work has investigated the fracture toughness of a model DGEBA epoxy system subject to Hidro-Thermal aging. A Photoelastic Stress Analysis technique has been implemented, showing the evolution of stresses arising throughout the water uptake process due to the non-uniform swelling of the material. Gravimetric and Dynamic Mechanical Thermal Analyses have further complemented the characterization, showing the onset of plasticization effects with aging. The correlation of all previous characterizations has allowed to conclude that an increase of KIC fracture toughness is obtained at the fully saturated condition. In particular Photoelasticity has also revealed the onset of relevant swelling induced stresses during the first stages of water absorption, leading to an increase of fracture toughness due to compressive stresses settling near the crack tip. A stress free condition is instead reestablished at the later stages of absorption, suggesting that the increased toughness of the saturated material is an effect of the modifications induced by aging on the polymer structure.

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.

Effects of Forming Process on Composite mode I Interlaminar Fracture Toughness

Directory of Open Access Journals (Sweden)

CHEN Xingyi

2016-10-01

Full Text Available In order to compare and analyse the effect of two different kinds of forming process on composite mode I interlaminar fracture toughness, the DCB specimens were tested by using hypothesis inspeetion method.A finite element model was also used to simulate the crack propagation process.The results demonstrate that the average of mode I interlaminar fracture toughness from silicon rubber flexible mold forming is a bit higher than that from metal rigid mold forming.Howevers the variance of mode I interlaminar fracture toughness from the two groups shows no significant difference.The crack propagation process of the two forming process is similar. The established finite element model, which is identical to the test results, can predict the process of the crack expansion effectively.

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

International Nuclear Information System (INIS)

Goljahi, Sam; Lynch, Christopher S

2013-01-01

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

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

Science.gov (United States)

Goljahi, Sam; Lynch, Christopher S.

2013-09-01

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

Toughness of submerged arc weld metals of controlled rolled NB bearing steel

International Nuclear Information System (INIS)

Yamaguchi, T.; Shiga, A.; Kamada, A.; Tsuboi, J.

1982-01-01

The toughness and the hardness of reheated weld metals depend on the maximum reheating temperature. When the maximum reheating temperature is 500 to 700 0 C, the hardness of single pass weld metal increases and the toughness decreases because of fine Nb- and V-carbonitride precipitation. When the maximum reheating temperature is over 800 0 C, the hardness and the toughness remain almost unchanged. The stress relieving treatment of single pass weld metal at 600 0 C for 1 up to about 100 hours causes the increase in hardness and then decreases the hardness gradually. It needs over 500 hours to obtain the same hardness value as that of as-welded metal. The addition of Ti to weld metal is very effective to improve the toughness, however excess Ti increases the hardness of stress relieved weld metal by precipitating as fine Ti-carbonitride. Therefore Ti addition should be restricted within the lowest limit required to improve as-welded metal toughness. The optimum Ti content is about 0.020% in the case of weld metal of which oxygen content is 350 ppM or so. In multipass welding, the hardness of weld metal affected by subsequent weld heat cycle varies from pass to pass, because Nb and V content change with the passes as the result of the change in dilution from base metal. The most hardened zone is observed in the reheated first pass weld metal, in which Nb and V content are the highest. Good weld metal toughness would be obtained by lowering dilution from base metal and taking advantage of grain refinement by subsequent passes

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

International Nuclear Information System (INIS)

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

2005-01-01

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

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

International Nuclear Information System (INIS)

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

2008-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2008-09-15

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

Effect of Precipitation on Cryogenic Toughness in Isothermally Aged Austenitic Stainless Steel

Science.gov (United States)

Saucedo-Muñoz, M. L.; Lopez-Hirata, V. M.; Avila-Davila, E. O.; Villegas-Cardenas, J. D.; Gonzalez-Velazquez, J. L.

2017-03-01

The effect of grain-boundary precipitates on cryogenic impact toughness of two corrosion steels (standard AISI 316 and a steel with a nitrogen additive) is studied. The steels are aged at 600 - 900°C with a hold of up to 1000 min. The KCV impact toughness at -196°C is determined. It is shown that the impact toughness of the nitrogen-containing steel decreases under cooling after the aging at 700 and 800°C more considerably than that of steel 316 after aging at 800 and 900°C. The causes of the embrittlement of the nitrogen-containing steel are determined.

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

Energy Technology Data Exchange (ETDEWEB)

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

1997-04-01

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

Performance and biocompatibility of extremely tough alginate/polyacrylamide hydrogels.

Science.gov (United States)

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

2013-11-01

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

Upper shelf toughness of six submerged-arc weldmetals manufactured using Linde 124 flux

International Nuclear Information System (INIS)

Druce, S.G.; Hippsley, C.A.

1984-06-01

This paper describes the testing technique, data analysis procedures and results from the first phase of an experimental programme investigating upper shelf toughness of six submerged-arc weldmetals. The welds were manufactured using uncoated, Nickel coated and Copper coated wire electrodes and Linde 124 flux. J integral crack growth resistance curves have been derived from tests on single specimens over a range in temperature from 150 to 290 deg C. The results indicate a general decline in toughness with increasing temperature. At 290 deg C, the levels of initiation toughness from all six welds were essentially constant varying between 152 to 159 MPa square root of m. The Jsub(I)-R curves derived from this work are compared with toughness data used in the Marshall Study Group report of an assessment of the integrity of PWR pressure vessels. (author)

Friction weld ductility and toughness as influenced by inclusion morphology

International Nuclear Information System (INIS)

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

1983-01-01

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

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

TOUGH2: A general-purpose numerical simulator for multiphase nonisothermal flows

Energy Technology Data Exchange (ETDEWEB)

Pruess, K. [Lawrence Berkeley Lab., CA (United States)

1991-06-01

Numerical simulators for multiphase fluid and heat flows in permeable media have been under development at Lawrence Berkeley Laboratory for more than 10 yr. Real geofluids contain noncondensible gases and dissolved solids in addition to water, and the desire to model such `compositional` systems led to the development of a flexible multicomponent, multiphase simulation architecture known as MULKOM. The design of MULKOM was based on the recognition that the mass-and energy-balance equations for multiphase fluid and heat flows in multicomponent systems have the same mathematical form, regardless of the number and nature of fluid components and phases present. Application of MULKOM to different fluid mixtures, such as water and air, or water, oil, and gas, is possible by means of appropriate `equation-of-state` (EOS) modules, which provide all thermophysical and transport parameters of the fluid mixture and the permeable medium as a function of a suitable set of primary thermodynamic variables. Investigations of thermal and hydrologic effects from emplacement of heat-generating nuclear wastes into partially water-saturated formations prompted the development and release of a specialized version of MULKOM for nonisothermal flow of water and air, named TOUGH. TOUGH is an acronym for `transport of unsaturated groundwater and heat` and is also an allusion to the tuff formations at Yucca Mountain, Nevada. The TOUGH2 code is intended to supersede TOUGH. It offers all the capabilities of TOUGH and includes a considerably more general subset of MULKOM modules with added capabilities. The paper briefly describes the simulation methodology and user features.

Fracture toughness of welded joints of ASTM A543 steel plate

International Nuclear Information System (INIS)

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

1977-01-01

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

Heat-treatment and heat-to-heat variations in the fracture toughness of Alloy 718

International Nuclear Information System (INIS)

Mills, W.J.

1981-07-01

The effect of heat-treatment and heat-to-heat variations on the J Ic fracture toughness response of Alloy 718 was examined at room and elevated temperatures using the multiple-specimen R-curve technique. Six heats of alloy 718 were tested in the conventional and modified heat-treated conditions. The fracture toughness response for the modified superalloy was found to be superior to that exhibited by the conventional material. Heat-to-heat variations in the J Ic response of Alloy 718 were observed in both heat-treated conditions; the modified treatment exhibited much larger variability. The J Ic and corresponding K Ic fracture toughness values were analyzed statistically to establish minimum expected toughness, values for use in design and safety analyses. 26 refs., 10 figs., 9 tabs

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

During early and mid-adolescence, greater mental toughness is related to increased sleep quality and quality of life.

Science.gov (United States)

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

2016-06-01

The aim of this study was to explore the association between mental toughness, subjective sleep, physical activity, and quality of life during early and mid-adolescence. A total of 1475 participants (mean age = 13.4 years; range: 11-16 years) took part in the study. They completed questionnaires related to mental toughness, physical activity, subjective sleep, and quality of life. Greater mental toughness was related to more favorable quality of life and increased subjective sleep. Mental toughness was not related to physical activity. Increased mental toughness, favorable quality of life, and sleep are related during early and mid-adolescence. Against our expectations, mental toughness was not related to physical activity. © The Author(s) 2014.

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.

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.

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

Directory of Open Access Journals (Sweden)

Vishwesh Dikshit

2017-10-01

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

Determination of fracture toughness of human permanent and primary enamel using an indentation microfracture method.

Science.gov (United States)

Hayashi-Sakai, Sachiko; Sakai, Jun; Sakamoto, Makoto; Endo, Hideaki

2012-09-01

The purpose of the present study was to examine the fracture toughness and Vickers microhardness number of permanent and primary human enamel using the indentation microfracture method. Crack resistance and a parameter indirectly related to fracture toughness were measured in 48 enamel specimens from 16 permanent teeth and 12 enamel specimens obtained from six primary teeth. The Vickers microhardness number of the middle portion was greater than the upper portion in primary enamel. The fracture toughness was highest in the middle portion of permanent enamel, because fracture toughness greatly depends upon microstructure. These findings suggest that primary teeth are not miniature permanent teeth but have specific and characteristic mechanical properties.

The effect of crack instability/stability on fracture toughness of brittle materials

International Nuclear Information System (INIS)

Baratta, F.I.

1997-01-01

This paper summarizes three recent experimental works coauthored by the present author regarding the effect of crack instability/stability on fracture toughness, and also includes the necessary formulae for predicting stability. Two recent works have shown that unstable crack extension resulted in apparent increases in fracture toughness compared to that determined during stable crack growth. In the first investigation a quasi-brittle polymer, polymethylmethacrylate, was examined. In the second, a more brittle metallic material, tungsten, was tested. In both cases the transition from unstable to stable behavior was predicted based on stability analyses. The third investigation was conducted on a truly brittle ceramic material, hot pressed silicon nitride. These three papers showed that fracture toughness test results conducted on brittle materials vary according to whether the material fractures in an unstable or stable manner. Suggestions for achieving this important yet difficult phenomenon of stable crack growth, which is necessary when determining the fracture toughness variation occurring during unstable/stable crack advance, are presented, as well as recommendations for further research

Prediction of fracture toughness K/sub Ic/ of steel from Charpy impact test results

Energy Technology Data Exchange (ETDEWEB)

Iwadate, Tadao; Tanaka, Yasuhiko; Takemata, Hiroyuki; Terashima, Shuhei

1986-08-01

This paper presents a method to predict the fracture toughness K/sub Ic/ and/or K/sub Id/ of steels using their Charpy impact test results and tensile properties. The fracture toughness, Charpy impact and tensile properties of 2 1/4 Cr-1Mo, ASTM A508 Cl.1, A508 Cl.2 A508 Cl.3 and A533 Gr.B Cl.1 steels were measured and analysed on the basis of the excess temperature (test temperature minus FATT) and Rolfe-Novak correlation. The relationship between K/sub Ic//K/sub Ic-us/ and the excess temperature, where K/sub Ic-us/ is the upper-shelf fracture toughness K/sub Ic/ predicted by Rolfe-Novak correlation, discloses that the K/sub Ic/ transition curves of several steels are representable by only one trend curve of K/sub Ic//K/sub Ic-us/ or K/sub Id//K/sub Id-us/ versus excess temperature relation. This curve is denoted as a ''master curve''. By using this curve, the fracture toughness of steel can be predicted using Charpy impact and tensile test results. By taking account of the scattering of both the fracture toughness and Charpy impact test results, the confidence limits of the master curve were also determined. Another approach to develop more general procedure of predicting the fracture toughness K/sub Ic/ is also discussed.

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

Controlling coaching and athlete thriving in elite adolescent netballers: The buffering effect of athletes' mental toughness.

Science.gov (United States)

Gucciardi, Daniel F; Stamatis, Andreas; Ntoumanis, Nikos

2017-08-01

The purposes of this study were to examine the association between controlling coach behaviours and athlete experiences of thriving and test the buffering effect of mental toughness on this relation. A cross-sectional survey. In total, 232 female netballers aged 11 to 17 years (14.97+1.52) with between 1 and 15 years of experience in their sport (7.50+2.28) completed measures of controlling coach interpersonal style, mental toughness and thriving. Latent moderated structural models indicated that (i) controlling coach behaviours were inversely related with experiences of vitality and learning; (ii) mental toughness was positively associated with psychological experiences of both dimensions of thriving; and (iii) mental toughness moderated the effect of coach's controlling interpersonal style on learning but not vitality experiences, such that the effect was weaker for individuals who reported higher levels of mental toughness. This study extends past work and theory to show that mental toughness may enable athletes to counteract the potentially deleterious effect of controlling coach interpersonal styles. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

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

Energy Technology Data Exchange (ETDEWEB)

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

2010-03-25

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

The dose dependence of fracture toughness Of F82H steel

Energy Technology Data Exchange (ETDEWEB)

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

2007-07-01

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

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

Rapid estimation of fatigue entropy and toughness in metals

Energy Technology Data Exchange (ETDEWEB)

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

2014-10-15

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

Rapid estimation of fatigue entropy and toughness in metals

International Nuclear Information System (INIS)

Liakat, M.; Khonsari, M.M.

2014-01-01

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

Fracture toughness measurements of WC-based hard metals

International Nuclear Information System (INIS)

Prakash, L.; Albert, B.

1983-01-01

The fracture toughness of WC-based cemented carbides was determined by different methods. The values obtained are dependent on the procedure of measurement. Each method thoughness of hard metals mutually. (orig.) [de

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…

Analysis of size effect applicable to evaluation of fracture toughness of base metal for PWR vessel

International Nuclear Information System (INIS)

Benhamou, C.; Joly, P.; Andrieu, A.; Parrot, A.; Vidard, S.

2015-01-01

The objective of the present paper is to review the specimen size effect (also called crack front length effect) on Fracture Toughness of PWR Reactor Pressure Vessel Steel base metal. The analysis of the reality and amplitude of this effect is conducted in a first step on a database (the so-called GKSS database) including fracture toughness test results on a single representative material using specimens of different thicknesses, tested in the same temperature range. A realistic analytical form for describing the size effect observed in this data set is thus derived from statistical analyses and proposed for engineering application. In a second step, this size effect formulation is then applied to a large number of fracture toughness data, obtained in Irradiation Surveillance Programs, and also to the numerous data used for the definition of the ASME (and RCC-M) fracture toughness reference curves. This analysis allows normalizing all the available fracture toughness data with a single specimen width of 100 mm and defining the fracture toughness reference curve as the lower bound of this normalized set of data points. It is thus demonstrated that the fracture toughness reference curve is associated with a reference crack length of 100 mm, and can be used in RPV integrity analyses for other crack front length in association with the crack front length correction formula defined in the first step. (authors)

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

International Nuclear Information System (INIS)

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

2013-01-01

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

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

International Nuclear Information System (INIS)

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

2004-01-01

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

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

Science.gov (United States)

Li, Zhenshun; Zhao, Xuemin; Shan, Dongri

2018-06-06

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

Notch constraint effects on the dynamic fracture toughness of an unaged beta titanium alloy

International Nuclear Information System (INIS)

Rack, H.J.

1975-01-01

The influence of notch included angle and root radius on the apparent dynamic fracture toughness of an unaged metastable beta titanium alloy, Ti--3Al--8V--6Cr--4Zr--4Mo, has been examined. The apparent fracture toughness, K/sub Id/(rho), increases with both notch radius, rho and included angle, ω. These results have been compared with the theoretical predictions of Tetelman, et al. and Smith. The comparisons show that neither theory accurately describes the effect of varying notch constraint on the apparent dynamic fracture toughness. Although preliminary considerations indicate that qualitative descriptions of notch acuity effects may be given by recent finite element analysis of the stress and strain distributions below a notch root, there is presently no quantitative basis for determining the true dynamic fracture toughness of materials from the results of blunt notch experiments. (auth)

Development of the transverse tensile and fracture toughness test techniques for spent fuel cladding

Energy Technology Data Exchange (ETDEWEB)

Ahn, S. B.; Hong, K. P.; Jung, Y. H.; Seo, H. S.; Oh, W. H.; Yoo, B. O.; Kim, D. S.; Seo, K. S

2001-12-01

To define the cause of cladding damage which can take place during the operation of nuclear power plant and the storage through the degradation aspect of mechanical characteristics, the transverse tensile an fracture toughness test were developed in hot cell at IMEF(Irradiated Material Experiment Facility). The following hot cell techniques were developed. 1. The development of a jig and a specimen for transverse tensile test 2. The acquisition of a manufacturing technique for the transverse tensile specimen at hot cell 3. The acquisition of testing procedures and an analysis technque for the transverse tensile 4. The dimensional determination of an optimized fracture toughness specimen 5. The acquisition of manufacturing technique for the fracture toughness test specimen at the hot cell 6. The acquisition of testing procedures and analysis technique for the fracture toughness test (Multiple specimen method, DCPD method, Load ratio method)

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.

Influence of hydrogen content on fracture toughness of CWSR Zr-2.5Nb pressure tube alloy

Science.gov (United States)

Singh, R. N.; Bind, A. K.; Srinivasan, N. S.; Ståhle, P.

2013-01-01

In this work, influence of hydrogen and temperature on the fracture toughness parameters of unirradiated, cold worked and stress relieved (CWSR) Zr-2.5Nb pressure tube alloys used in Indian Pressurized Heavy Water Reactor is reported. The fracture toughness tests were carried out using 17 mm width curved compact tension specimens machined from gaseously hydrogen charged tube-sections. Metallography of the samples revealed that hydrides were predominantly oriented along axial-circumferential plane of the tube. Fracture toughness tests were carried out in the temperature range of 30-300 °C as per ASTM standard E-1820-06, with the crack length measured using direct current potential drop (DCPD) technique. The fracture toughness parameters (JQ, JMax and dJ/da), were determined. The critical crack length (CCL) for catastrophic failure was determined using a numerical method. It was observed that for a given test temperature, the fracture toughness parameters representing crack initiation (JQ) and crack propagation (JMax, and dJ/da) is practically unaffected by hydrogen content. Also, for given hydrogen content, all the aforementioned fracture toughness parameters increased with temperature to a saturation value.

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

International Nuclear Information System (INIS)

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

1984-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

Odegaard, T K

1979-06-01

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

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

International Nuclear Information System (INIS)

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

1990-01-01

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

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

International Nuclear Information System (INIS)

Odegaard, T.K.

1979-06-01

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

Thin slab processing of acicular ferrite steels with high toughness

Energy Technology Data Exchange (ETDEWEB)

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

2005-07-01

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

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.

Fracture toughness of the F-82H steel-effect of loading modes, hydrogen, and temperature

International Nuclear Information System (INIS)

Li, H.-X.; Jones, R.H.; Hirth, J.P.; Gelles, D.S.

1996-01-01

The effects of loading mode, hydrogen, and temperature on fracture toughness and tearing modulus were examined for a ferritic/martensitic steel (F-82H). The introduction of a shear load component, mode III, significantly decreased the initiation and propagation resistance of cracks compared to the opening load, mode I, behavior. Mode I crack initiation and propagation exhibited the highest resistance. A minimum resistance occurred when the mode I and mode III loads were nearly equal. The presence of 4 wppm hydrogen decreased the cracking resistance compared to behavior without H regardless of the loading mode. The minimum mixed-mode fracture toughness with the presence of hydrogen was about 30% of the hydrogen-free mode I fracture toughness. The mixed-mode toughness exhibited a lesser sensitivity to temperature than the mode I toughness. The J IC value was 284 kJ/m 2 at room temperature, but only 60 kJ/m 2 at -55 C and 30 kJ/m 2 at -90 C. The ductile to brittle transition temperature (DBTT) was apparently higher than -55 C. (orig.)

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%.

Postirradiation fracture toughness of Inconel X-750

International Nuclear Information System (INIS)

Mills, W.J.

1983-01-01

The effect of fast-neutron irradiation on the fracture toughness response of Inconel X-750 was characterized at 427 deg C using the J-R curve technique. Irradiation exposures ranging from 3 to 16 displacements per atom resulted in a reduction in Jsub(Ic) from 130 to 76 kJ/m 2 and a reduction in tearing modulus from 32 to 2.6. Postirradiation fractographic examination revealed that an intergranular fracture mechanism was dominant, in contrast to the extensive transgranular cracking mode found on unirradiated fracture surfaces. The enhanced intergranular failure observed after irradiation was caused by extensive heterogeneous slip in a matrix that was greatly strengthened by an irradiation-induced dislocation substructure. Specifically, intense planar slip bands impinged on the grain boundaries and generated large stress concentrations. Since the stress concentrations could not be relaxed by the hardened matrix, the grain boundaries 'unzipped' readily, resulting in the low toughness and tearing resistance. (author)

Effect of delaminations on improvement of notch toughness at low temperatures

International Nuclear Information System (INIS)

Zhou, W.; Loh, N.L.

1996-01-01

The notched-bar impact test is often used to assess the notch toughness of engineering materials. The principle of the test is that a material absorbs a certain amount of energy when it breaks; the energy thus absorbed is an indication of the material's resistance to impact fracture. If the material is brittle, it breaks easily with a small amount of absorbed energy. If it is tough, it will absorb more energy to fracture. It has been well recognized that most engineering materials undergo a transition from notch tough to notch brittle behavior when the temperature is reduced. In the present study, however, an abnormal trend in the transition behavior was found for an austenitic stainless steel. V-notched specimens of the steel were tested under impact loading in a wide temperature range from -196 C to room temperature. Contrary to expectation, the impact energy values obtained at low temperatures were found to be much higher than those obtained at room temperature, indicating that the steel became tougher rather than more brittle when the test temperature was lowered. This intriguing phenomenon cannot be explained simply according to the tensile stress fracture criterion. Strong evidence has been obtained in the present study to show that the improvement of notch toughness at low temperatures is caused by delaminations

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

Directory of Open Access Journals (Sweden)

Chiaki Sato

2011-04-01

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

Acoustic emission characterization of fracture toughness for fiber reinforced ceramic matrix composites

International Nuclear Information System (INIS)

Mei, Hui; Sun, Yuyao; Zhang, Lidong; Wang, Hongqin; Cheng, Laifei

2013-01-01

The fracture toughness of a carbon fiber reinforced silicon carbide composite was investigated relating to classical critical stress intensity factor K IC , work of fracture, and acoustic emission energy. The K IC was obtained by the single edge notch beam method and the work of fracture was calculated using the featured area under the load–displacement curves. The K IC , work of fracture, and acoustic emission energy were compared for the composites before and after heat treatment and then analyzed associated with toughening microstructures of fiber pullout. It indicates that the work of fracture and acoustic emission energy can be more suitable to reflect the toughness rather than the traditional K IC , which has certain limitation for the fracture toughness characterization of the crack tolerant fiber ceramic composites.

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

Directory of Open Access Journals (Sweden)

Zhenshun Li

2018-06-01

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

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

International Nuclear Information System (INIS)

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

1998-02-01

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

Evolution: Weevils Get Tough on Symbiotic Tyrosine.

Science.gov (United States)

Dale, Colin

2017-12-04

Weevils, which represent one of the most diverse groups of terrestrial insects in nature, obtain a tough exoskeleton through the activity of an ancient bacterial symbiont with a tiny genome that serves as a factory for the production of tyrosine. Copyright © 2017 Elsevier Ltd. All rights reserved.

Mode II Interlaminar Fracture Toughness and Fatigue Characterization of a Graphite Epoxy Composite Material

Science.gov (United States)

O'Brien, T. Kevin; Johnston, William M.; Toland, Gregory J.

2010-01-01

Mode II interlaminar fracture toughness and delamination onset and growth characterization data were generated for IM7/8552 graphite epoxy composite materials from two suppliers for use in fracture mechanics analyses. Both the fracture toughness testing and the fatigue testing were conducted using the End-notched Flexure (ENF) test. The ENF test for mode II fracture toughness is currently under review by ASTM as a potential standard test method. This current draft ASTM protocol was used as a guide to conduct the tests on the IM7/8552 material. This report summarizes the test approach, methods, procedures and results of this characterization effort.

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

Energy Technology Data Exchange (ETDEWEB)

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

1988-02-01

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

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

International Nuclear Information System (INIS)

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

1981-10-01

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

Role of specimen size upon the measured toughness of cellular solids

International Nuclear Information System (INIS)

Christodoulou, I; Tan, P J

2013-01-01

It is well known that the mechanical properties of cellular solids depend critically upon the specimen size and that a 'sufficiently' large test specimen is needed to obtain representative bulk values. Notwithstanding, the fracture toughness of cellular solids is still measured experimentally based on standards, such as the ASTM E399 and E813, developed for solid materials that do not possess an intermediate, 'cell-level' length scale. Experimental data in the literature appears to show that the toughness of stochastic 3D foams is, also, size-dependent. This paper presents the results of a detailed finite element (FE) study that will quantify, and identify the physical origin of, the size-dependent effect. Three-point bending of a single-edge notched (or SEN(B)) specimen, with a 2D Voronoi micro-architecture, is modelled numerically to obtain estimates of fracture toughness which are compared to those obtained with a 'boundary-layer' analysis

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

International Nuclear Information System (INIS)

Ishikawa, Keisuke; Maruyama, Norio; Tsuya, Kazuo

1978-01-01

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

J/sub 1c/ fracture toughness transition behavior of HT-9

International Nuclear Information System (INIS)

Huang, F.H.

1984-01-01

Small compact tension specimens of two heats of HT-9 were tested at temperatures ranging from room temperature to -192 0 C. The ductile-brittle transition toughness of HT-9 was evaluated using the J-integral approach. There were two loading rates of 2.1 x 10 -5 m/s and 3.2 x 10 -2 m/s. The ductile-brittle transition temperatures of HT-9 (number 1 heat) tested at 2.1 x 10 -5 m/s and HT-9 (number 2 heat) tested at 3.2 x 10 -2 m/s were found to be -60 and -10 0 C, respectively. Results showed the fracture toughness of the former was not sensitive to loading rate and the lower shelf toughness decreased with temperature to a J/sub 1c/ value of 5 kJ/m 2 at -190 0 C. Furthermore, the values of J/sub 1c/ were valid since the thickness of the test specimens was well above the thickness criterion

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

Science.gov (United States)

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

1982-04-01

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

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

International Nuclear Information System (INIS)

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

1988-01-01

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

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.

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

Science.gov (United States)

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

2017-02-01

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

Effect of TiC addition on fracture toughness of Al6061 alloy

Science.gov (United States)

Raviraj, M. S.; Sharanprabhu, C. M.; Mohankumar, G. C.

2018-04-01

Al 6061 matrix was reinforced with different proportions of TiC particles such as 3wt%, 5wt% and 7wt% and the effect on fracture toughness was studied. Al-TiC metal matrix composites were produced by stir casting method to ensure uniform distribution of the TiC particulates in the Al matrix. LEFM (Linear Elastic Fracture Mechanics) has been used to characterize the fracture toughness using various specimen geometries. The compact tension (CT) specimens with straight through notch were machined as per ASTM E399 specifications. All the specimens were machined to have constant a/W=0.5 and B/W was varied from 0.2 to 0.7. A sharp crack initiation was done at the end of notch by fatigue loading using servo-hydraulic controlled testing machine. Load v/s crack mouth opening displacement (CMOD) data was plotted and stress intensity factor, KQ determined. Critical stress intensity factor KIC was obtained by plotting KQ v/s thickness of specimen data. The fracture toughness of the composites varied between 16-19 MPa√m as compared to 23MPa√m for base alloy Al6061. Composites with 3wt% and 7wt% TiC showed better fracture toughness than 5wt% TiC reinforced Al metal matrix composites.

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

International Nuclear Information System (INIS)

Eriksson, K.

1998-01-01

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

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

International Nuclear Information System (INIS)

Finsterle, Stefan; Oldenburg, Curtis M.

2004-01-01

Numerical simulators are playing an increasingly important role in advancing our fundamental understanding of hydrological systems. They are indispensable tools for managing groundwater resources, analyzing proposed and actual remediation activities at contaminated sites, optimizing recovery of oil, gas, and geothermal energy, evaluating subsurface structures and mining activities, designing monitoring systems, assessing the long-term impacts of chemical and nuclear waste disposal, and devising improved irrigation and drainage practices in agricultural areas, among many other applications. The complexity of subsurface hydrology in the vadose zone calls for sophisticated modeling codes capable of handling the strong nonlinearities involved, the interactions of coupled physical, chemical and biological processes, and the multiscale heterogeneities inherent in such systems. The papers in this special section of ''Vadose Zone Journal'' are illustrative of the enormous potential of such numerical simulators as applied to the vadose zone. The papers describe recent developments and applications of one particular set of codes, the TOUGH family of codes, as applied to nonisothermal flow and transport in heterogeneous porous and fractured media (http://www-esd.lbl.gov/TOUGH2). The contributions were selected from presentations given at the TOUGH Symposium 2003, which brought together developers and users of the TOUGH codes at the Lawrence Berkeley National Laboratory (LBNL) in Berkeley, California, for three days of information exchange in May 2003 (http://www-esd.lbl.gov/TOUGHsymposium). The papers presented at the symposium covered a wide range of topics, including geothermal reservoir engineering, fracture flow and vadose zone hydrology, nuclear waste disposal, mining engineering, reactive chemical transport, environmental remediation, and gas transport. This Special Section of ''Vadose Zone Journal'' contains revised and expanded versions of selected papers from the

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.

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

International Nuclear Information System (INIS)

Merle, B.; Goeken, M.

2011-01-01

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

Effect of Thermal Aging and Test Temperatures on Fracture Toughness of SS 316(N) Welds

Science.gov (United States)

Dutt, B. Shashank; Babu, M. Nani; Shanthi, G.; Moitra, A.; Sasikala, G.

2018-03-01

The effect of thermal aging and test temperatures on fracture toughness (J 0.2) of SS 316(N) weld material has been studied based on J-R curve evaluations. The aging of the welds was carried out at temperatures 370, 475 and 550 °C and for durations varying from 1000 to 20,000 h. The fracture toughness (J-R curve) tests were carried out at 380 and 550 °C for specimens after all aging conditions, including as-weld condition. The initiation fracture toughness (J 0.2) of the SS 316(N) weld material has shown degradation after 20,000-h aging durations and is reflected in all the test temperatures and aging temperatures. The fracture toughness after different aging conditions and test temperatures, including as-weld condition, was higher than the minimum specified value for this class of welds.

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

Fracture toughness master curve characterization of Linde 1092 weld metal for Beaver valley 1 reactor

International Nuclear Information System (INIS)

Lee, Bong Sang; Yang, Won Jon; Hong, Jun Hwa

2000-12-01

This report summarizes the test results obtained from the Korean contribution to the integrity assessment of low toughness Beaver Valley reactor vessel by characterizing the fracture toughness of Linde 1092 (No. 305414) weld metal. 10 PCVN specimens and 10 1T-CT specimens were tested in accordance with the ASTM E 1921-97 standard, 'Standard test method for determination of reference temperature, T o , for ferritic steels in the transition range'. This results can also be useful for assessment of Linde 80 low toughness welds of Kori-1

Fracture toughness master curve characterization of Linde 1092 weld metal for Beaver valley 1 reactor

Energy Technology Data Exchange (ETDEWEB)

Lee, Bong Sang; Yang, Won Jon; Hong, Jun Hwa

2000-12-01

This report summarizes the test results obtained from the Korean contribution to the integrity assessment of low toughness Beaver Valley reactor vessel by characterizing the fracture toughness of Linde 1092 (No. 305414) weld metal. 10 PCVN specimens and 10 1T-CT specimens were tested in accordance with the ASTM E 1921-97 standard, 'Standard test method for determination of reference temperature, T{sub o}, for ferritic steels in the transition range'. This results can also be useful for assessment of Linde 80 low toughness welds of Kori-1.

Development of fracture toughness test method for nuclear grade graphite

Energy Technology Data Exchange (ETDEWEB)

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

2006-02-15

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

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

Energy Technology Data Exchange (ETDEWEB)

Lee, Ki-Hyoung, E-mail: shirimp@kaist.ac.k [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of); Kim, Min-Chul; Lee, Bong-Sang [Nuclear Materials Research Division, KAERI, Daejeon 305-353 (Korea, Republic of); Wee, Dang-Moon [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of)

2010-08-15

The fracture toughness properties of the tempered martensitic SA508 Gr.4N Ni-Mo-Cr low alloy steel for reactor pressure vessels were investigated by using the master curve concept. These results were compared to those of the bainitic SA508 Gr.3 Mn-Mo-Ni low alloy steel, which is a commercial RPV material. The fracture toughness tests were conducted by 3-point bending with pre-cracked charpy (PCVN) specimens according to the ASTM E1921-09c standard method. The temperature dependency of the fracture toughness was steeper than those predicted by the standard master curve, while the bainitic SA508 Gr.3 steel fitted well with the standard prediction. In order to properly evaluate the fracture toughness of the Gr.4N steels, the exponential coefficient of the master curve equation was changed and the modified curve was applied to the fracture toughness test results of model alloys that have various chemical compositions. It was found that the modified curve provided a better description for the overall fracture toughness behavior and adequate T{sub 0} determination for the tempered martensitic SA508 Gr.4N steels.

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

DEFF Research Database (Denmark)

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

2016-01-01

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

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.

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.)

Dependence of fracture toughness of molybdenum laser welds on dendritic spacing and in situ titanium additions

International Nuclear Information System (INIS)

Jellison, J.L.

1979-01-01

The fracture toughness of molybdenum welds has been improved by in situ gettering of oxygen by means of physically deposited titanium. The addition of titanium suppressed brittle intergranular fracture. Pulsed laser welds (both Nd:YAG and CO 2 ) exhibited superior toughness to that of continuous wave CO 2 laser welds. Also, welds of vacuum arc remelted grades were tougher than those of sintered molybdenum. However, weld toughness could not be correlated with either oxygen or carbon content

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

International Nuclear Information System (INIS)

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

2007-01-01

Experimental data are presented on the fracture toughness of wrought and cast austenitic stainless steels (SSs) that were irradiated to a fluence of ∼ 1.5 x 10 21 n/cm 2 (E > 1 MeV) * (∼ 2.3 dpa) at 296-305 o C. To evaluate the possible effects of test environment and crack morphology on the fracture toughness of these steels, all tests were conducted in normal-water-chemistry boiling water reactor (BWR) environments at ∼ 289 o C. Companion tests were also conducted in air on the same material for comparison. The fracture toughness J-R curves for SS weld heat-affected-zone materials in BWR water were found to be comparable to those in air. However, the results of tests on sensitized Type 304 SS and thermally aged cast CF-8M steel suggested a possible effect of water environment. The available fracture toughness data on irradiated austenitic SSs were reviewed to assess the potential for radiation embrittlement of reactor-core internal components. The synergistic effects of thermal and radiation embrittlement of cast austenitic SS internal components are also discussed. (author)

Ductile fracture toughness of heavy section pressure vessel steel plate. A specimen-size study of ASTM A 533 steels

International Nuclear Information System (INIS)

Williams, J.A.

1979-09-01

The ductile fracture toughness, J/sub Ic/, of ASTM A 533, Grade B, Class 1 and ASTM A 533, heat treated to simulate irradiation, was determined for 10- to 100-mm thick compact specimens. The toughness at maximum specimen load was also measured to determine the conservatism of J/sub Ic/. The toughness of ASTM A 533, Grade B, Class 1 steel was 349 kJ/m 2 and at the equivalent upper shelf temperature, the heat treated material exhibited 87 kJ/m 2 . The maximum load fracture toughness was found to be linearly proportional to specimen size, and only specimens which failed to meet ASTM size criteria exhibited maximum load toughness less than J/sub Ic/

Fracture toughness of A533B Part III - variability of A533B fracture toughness as determined from Charpy data

International Nuclear Information System (INIS)

Druce, S.G.; Eyre, B.L.

1978-08-01

This is the final part of a series of three reports examining the upper shelf fracture toughness of A533B Class 1 pressure vessel steel. Part I (AERE R 8968) critically reviews the current elasto plastic fracture mechanics methodologies employed to characterise toughness following extensive yielding and Part II (AERE R 8969) examines several sources of fracture mechanics data pertinent to A533B Class 1 in the longitudinal (RW) orientation. Part III is a review of the effects of (i) position and orientation within the plate (ii) welding processes and post weld heat treatment and (iii) neutron irradiation as measured by Charpy impact testing. It is concluded that the upper shelf factor energy is dependent on orientation and position and can be reduced by welding, extended post weld heat treatments and neutron irradiation. Neutron irradiation effects are known to be strongly dependent on composition and metallurgical conditions, but an explanation for the variability following extended post weld treatments has yet to be resolved. (author)

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

International Nuclear Information System (INIS)

Yoon, K.K.

1993-01-01

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

Fracture toughness behaviour of carbon fibre epoxy composite with Kevlar reinforced interleave

International Nuclear Information System (INIS)

Yadav, S.N.; Kumar, Vijai; Verma, Sushil K.

2006-01-01

This work was to evaluate as to how mode II fracture toughness G II is affected by interleave having Kevlar fibre reinforcement in the fracture plane. Thermoset interleave and chopped Kevlar fibres were applied between the carbon/epoxy composite layers. An artificial crack starter was implanted in the mid-plane to initiate the fracture process. The following five different types of carbon fibre/epoxy composites were prepared and tested. (a) Base laminate without interleave (b) unreinforced interleave and (c) 0.5, 1.0 and 1.5 mg/cm 2 chopped Kevlar fibre reinforced interleave. Results obtained show that fracture toughness G IIC enhanced up to about two times in all the laminates. However, enhancement in fracture toughness G IIC was more effective in interleaved laminate than Kevlar reinforced interleaved because of large energy absorbing capabilities of interleaf. Mechanism of fracture and toughening were examined by using scanning electron microscope

Fracture toughness of yttria-stabilized zirconia sintered in conventional and microwave ovens.

Science.gov (United States)

Marinis, Aristotelis; Aquilino, Steven A; Lund, Peter S; Gratton, David G; Stanford, Clark M; Diaz-Arnold, Ana M; Qian, Fang

2013-03-01

The fabrication of zirconium dioxide (ZrO2) dental prosthetic substructures requires an extended sintering process (8 to 10 hours) in a conventional oven. Microwave sintering is a shorter process (2 hours) than conventional sintering. The purpose of this study was to compare the fracture toughness of 3 mol % Y2O3-stabilized ZrO2 sintered in a conventional or microwave oven. Partially sintered ZrO2 specimens from 3 manufacturers, KaVo, Lava 3M, and Crystal HS were milled (KaVo Everest engine) and randomly divided into 2 groups: conventional sintering and microwave sintering (n=16 per group). The specimens were sintered according to the manufacturers' recommendations and stored in artificial saliva for 10 days. Fracture toughness was determined by using a 4-point bend test, and load to fracture was recorded. Mean fracture toughness for each material was calculated. A 2-way ANOVA followed by the Tukey HDS post hoc test was used to assess the significance of sintering and material effects on fracture toughness, including an interaction between the 2 factors (α=.05). The 2-way ANOVA suggested a significant main effect for ZrO2 manufacturer (P.05). The main effect of the sintering process (Conventional [5.30 MPa·m(1/2) ±1.00] or Microwave [5.36 MPa·m(1/2) ±0.92]) was not significant (P=.76), and there was no interaction between sintering and ZrO2 manufacturer (P=.91). Based on the results of this study, no statistically significant difference was observed in the fracture toughness of ZrO2 sintered in microwave or conventional ovens. Copyright © 2013 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

Fracture toughness versus micro-tensile bond strength testing of adhesive-dentin interfaces.

Science.gov (United States)

De Munck, Jan; Luehrs, Anne-Katrin; Poitevin, André; Van Ende, Annelies; Van Meerbeek, Bart

2013-06-01

To assess interfacial fracture toughness of different adhesive approaches and compare to a standard micro-tensile bond-strength (μTBS) test. Chevron-notched beam fracture toughness (CNB) was measured following a modified ISO 24370 standard. Composite bars with dimensions of 3.0×4.0×25 mm were prepared, with the adhesive-dentin interface in the middle. At the adhesive-dentin interface, a chevron notch was prepared using a 0.15 mm thin diamond blade mounted in a water-cooled diamond saw. Each specimen was loaded until failure in a 4-point bend test setup and the fracture toughness was calculated according to the ISO specifications. Similarly, adhesive-dentin micro-specimens (1.0×1.0×8-10 mm) were stressed in tensile until failure to determine the μTBS. A positive correlation (r(2)=0.64) was observed between CNB and μTBS, which however was only nearly statistically significant, mainly due to the dissimilar outcome of Scotchbond Universal (3M ESPE). While few μTBS specimens failed at the adhesive-dentin interface, almost all CNB specimens failed interfacially at the notch tip. Weibull moduli for interfacial fracture toughness were much higher than for μTBS (3.8-11.5 versus 2.7-4.8, respectively), especially relevant with regard to early failures. Although the ranking of the adhesives on their bonding effectiveness tested using CNB and μTBS corresponded well, the outcome of CNB appeared more reliable and less variable. Fracture toughness measurement is however more laborious and requires specific equipment. The μTBS nevertheless appeared to remain a valid method to assess bonding effectiveness in a versatile way. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Fracture toughness for materials of low ductility

International Nuclear Information System (INIS)

Barzilay, S.; Karp, B.; Perl, M.

1998-05-01

The results of a survey of methods for evaluating fracture toughness characteristics for semi-brittle and brittle materials are presented in this report. These methods differ considerably from those used for ductile materials by the specimen configurations, the methodology of the experiments and by the problems occurring while using these methods. The survey yields several important findings A. It is possible to create steady state crack growth by cyclic loading in several semi-brittle materials. B. The need for pre-cracking is not yet clear, nevertheless it is recommended to evaluate fracture toughens with pre-cracked specimen. C. As crack length and ligament size may effect fracture toughness results it is necessary to define minimum specimen dimensions to avoid this effect. D. The specimen thickness hardly affects the fracture toughens. E. Loading rate for the test is not well defined. It is commonly accepted to end the test in one minute. F. The main mechanism that causes inelastic deformation in semi-brittle materials is related to the generation of micro-cracks

Biofuels: making tough choices

Energy Technology Data Exchange (ETDEWEB)

Vermeulen, Sonja; Dufey, Annie; Vorley, Bill

2008-02-15

The jury is still out on biofuels. But one thing at least is certain: serious trade-offs are involved in the production and use of these biomass-derived alternatives to fossil fuels. This has not been lost on the European Union. The year kicked off with an announcement from the EU environment commissioner that it may be better for the EU to miss its target of reaching 10 per cent biofuel content in road fuels by 2020 than to compromise the environment and human wellbeing. The 'decision tree' outlined here can guide the interdependent processes of deliberation and analysis needed for making tough choices in national biofuels development.

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-04-15

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

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.

Application of TOUGH to hydrologic problems related to the unsaturated zone site investigation at Yucca Mountain, Nevada

Energy Technology Data Exchange (ETDEWEB)

Kwicklis, E.M.; Healy, R.W. [Geological Survey, Lakewood, CO (United States); Bodvarsson, G.S. [Lawrence Berkeley Laboratory, CA (United States)] [and others

1995-03-01

To date, TOUGH and TOUGH2 have been the principal codes used by the U.S. Geological Survey in their investigation of the hydrology of the unsaturated zone at Yucca Mountain. Examples of some applications of the TOUGH and TOUGH2 codes to flow and transport problems related to the Yucca Mountain site investigation are presented, and the slight modifications made to the codes to implement them are discussed. These examples include: (1) The use of TOUGH in a simple fracture network model, with a discussion of an approach to calculate directional relative permeabilities at computational cells located at fracture intersections. These simulations illustrated that, under unsaturated conditions, the locations of dominant pathways for flow through fracture networks are sensitive to imposed boundary conditions; (2) The application of TOUGH to investigate the possible hydrothermal effects of waste-generated heat at Yucca Mountain using a dual-porosity, dual-permeability treatment to better characterize fracture-matrix interactions. Associated modifications to TOUGH for this application included implementation of a lookup table that can express relative permeabilities parallel and transverse to the fracture plane independently. These simulations support the continued use of an effective media approach in analyses of the hydrologic effects of waste-generated heat; and (3) An investigation of flow and tracer movement beneath a wash at Yucca Mountain in which a particle tracker was used as a post-processor. As part of this study, TOUGH2 was modified to calculate and output the x-,y- and z- sequence of tuffs overlying the potential repository site will result in the formation of capillary barriers that locally promote considerable lateral flow, thereby significantly decreasing the magnitude of fluxes form peak values at the ground surface and delaying the arrival of surface-derived moisture at the potential repository horizon.

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

Science.gov (United States)

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

2018-03-01

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

On the proper fracture toughness properties to be used for pressurized thermal shock evaluations

International Nuclear Information System (INIS)

Server, W.L.

1997-01-01

The traditional approach in the U.S. for evaluating PTS has relied upon probabilistic studies in which the toughness has been based upon the data used to generated the lower bound ASME Code K IC and K IR curves. A mean curve through this data with a Gaussian statistical distribution assumed, except for a lower bound cutoff of somewhere between 2 and 3 standard deviations, has been used. The RT NDT normalizing concept has been maintained which then requires the measured shift in Charpy V-notch toughness at the 41 J (30 ft-lb) energy level be used to adjust the position of the Code curves. The Master Curve method provides a unique alternative in providing a much better measure of real fracture toughness, plus the opportunity to use a more refined statistical distribution using Weibull statistics. There are active moves in the U.S. to Standardize and Codify the Master Curve (also termed T 0 method). Benefits to both deterministic and probabilistic analyses will be realized since more realistic measures of toughness can be used

On the proper fracture toughness properties to be used for pressurized thermal shock evaluations

Energy Technology Data Exchange (ETDEWEB)

Server, W L [ATI Consulting, Danville, CA (United States)

1997-09-01

The traditional approach in the U.S. for evaluating PTS has relied upon probabilistic studies in which the toughness has been based upon the data used to generated the lower bound ASME Code K{sub IC} and K{sub IR} curves. A mean curve through this data with a Gaussian statistical distribution assumed, except for a lower bound cutoff of somewhere between 2 and 3 standard deviations, has been used. The RT{sub NDT} normalizing concept has been maintained which then requires the measured shift in Charpy V-notch toughness at the 41 J (30 ft-lb) energy level be used to adjust the position of the Code curves. The Master Curve method provides a unique alternative in providing a much better measure of real fracture toughness, plus the opportunity to use a more refined statistical distribution using Weibull statistics. There are active moves in the U.S. to Standardize and Codify the Master Curve (also termed T{sub 0} method). Benefits to both deterministic and probabilistic analyses will be realized since more realistic measures of toughness can be used.

Fracture toughness testing of core from the Cambro-Ordovician Section on the Oak Ridge Reservation

International Nuclear Information System (INIS)

Lemiszki, P.J.; Landes, J.D.

1996-01-01

The modified ring test was used to determine the mode I fracture toughness of bedrock cores from the DOE Oak Ridge Reservation in east Tennessee. Low porosity sandstones, limestones, and dolostones from the lower part of the Paleozoic section in Copper Creek and Whiteoak Mountain thrust sheets were sampled. In general, the average mode I fracture toughness decreases from sandstone, dolostone, and limestone. The fracture toughness of the limestones varies between rock units, which is related to different sedimentologic characteristics. Quality of results was evaluated by testing cores of Berea Sandstone and Indiana Limestone, which produced results similar to published results

A Novel Methods for Fracture Toughness Evaluation of Tool Steels with Post-Tempering Cryogenic Treatment

Directory of Open Access Journals (Sweden)

Ramona Sola

2017-02-01

Full Text Available Cryogenic treatments are usually carried out immediately after quenching, but their use can be extended to post tempering in order to improve their fracture toughness. This research paper focuses on the influence of post-tempering cryogenic treatment on the microstructure and mechanical properties of tempered AISI M2, AISI D2, and X105CrCoMo18 steels. The aforementioned steels have been analysed after tempering and tempering + cryogenic treatment with scanning electron microscopy, X-ray diffraction for residual stress measurements, and micro- and nano-indentation to determine Young’s modulus and plasticity factor measurement. Besides the improvement of toughness, a further aim of the present work is the investigation of the pertinence of a novel technique for characterizing the fracture toughness via scratch experiments on cryogenically-treated steels. Results show that the application of post-tempering cryogenic treatment on AISI M2, AISI D2, and X105CrCoMo18 steels induce precipitation of fine and homogeneously dispersed sub-micrometric carbides which do not alter hardness and Young’s modulus values, but reduce residual stresses and increase fracture toughness. Finally, scratch test proved to be an alternative simple technique to determine the fracture toughness of cryogenically treated steels.

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.

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

International Nuclear Information System (INIS)

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

2013-01-01

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

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

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

DEFF Research Database (Denmark)

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

2015-01-01

Bioactive glass ionomer cements (GICs) have been in widespread use for B40 years in dentistry and medicine. However, these composites fall short of the toughness needed for permanent implants. Significant impediment to improvement has been the requisite use of conventional destructive mechanical...... interfacial configurations. Contrary to convention, we find setting is non-monotonic, characterized by abrupt features not previously detected, including a glass–polymer coupling point, an early setting point, where decreasing toughness unexpectedly recovers, followed by stress-induced weakening of interfaces...

Evaluation of static and dynamic fracture toughness in ductile cast iron

International Nuclear Information System (INIS)

Kobayashi, Toshiro; Yamada, Shinya

1994-01-01

Ductile cast irons have been explored as a cask (container for spent nuclear fuel) material because of their low cost and good formability. The cask, which is a huge casting with 400-mm thickness and 100-Mg weight, envelops the nuclear material. Therefore, the fracture toughness of cask must be evaluated not only under the static loading condition but also under the dynamic loading condition to ensure its safety against an accident during the transport. In this article, crack extension behavior and fracture toughness of ductile cast iron were examined by three-point bend tests, where various detection methods of crack initiation under static and dynamic loading conditions were adopted. Loading on the specimens was interrupted at various displacement points, and the final fracture surfaces of the specimen were observed via scanning electron microscopy (SEM). Crack-tip opening displacement (CTOD) obtained under the dynamic loading conditions was smaller than that under the static loading condition in ferritic ductile cast iron, and CTOD additionally decreased with increasing pearlite content in the matrix. The relationship between J(ΔC) obtained by the compliance changing rate method and J(R) established by the intersection of the crack extension resistance curve and the theoretical blunting line varied with pearlite content. The average value of J(ΔC) and J(R), that is J(mid), was proposed to define the fracture toughness of ductile cast iron; J(mid) was considered to be a reasonable measure for the fracture toughness of ductile cast iron, irrespective of loading condition and the pearlite content in the matrix

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-06-21

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

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

International Nuclear Information System (INIS)

Yasunaka, T.; Nakano, K.

1993-01-01

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

Improvement of the fracture toughness matrix cured by electron beam radiation, by incorporation of thermoplastic

International Nuclear Information System (INIS)

Chauray, E.

2003-07-01

The aim of the present study is to improve the fracture toughness of a vinyl-ester matrix cured by electron beam radiation, by incorporation of a thermoplastic polymer. The ultimate plan is to improve the fracture toughness of the composite material made of this reinforced matrix and carbon fibres. The first step deals with the study of an epoxy matrix reinforced by a polyether-sulfone. This well-known material, as it is used in industrial formulation, allowed us to characterize all the parameters needed to obtain a good reinforcement as for instance the morphology, and also to compare two kinds of processes: thermal and electron beam curing. In fact, we are really interested in increasing fracture toughness of a vinyl-ester matrix that is not miscible with polyether-sulfone. So a copolymer which has a similar structure as polyether-sulfone is synthesized in order to obtain a miscible blend. The corresponding material has good fracture toughness, with an increase of 80 % for 15 % addition of thermoplastic. (author)

Influence of structures on fracture and fracture toughness of cemented tungsten carbides

International Nuclear Information System (INIS)

Zhao, W.; Zhang, X.

1987-01-01

A study was made of the influence of structures on fracture and fracture toughness of cemented tungsten carbides with different compositions and grain sizes. The measurement of the fracture toughness of cemented tungsten carbide was carried out using single edge notched beam. The microstructural parameters and the proportion for each fracture mode on the fracture surface were obtained. The brittle fracture of the alloy is mainly due to the interfacial decohesion fracture following the interface of the carbide crystals. It has been observed that there are localized fractures region ahead of the crack tip. The morphology of the crack propagation path as well as the slip structure in the cobalt phase of the deformed region have been investigated. In addition, a study of the correlation between the plane strain fracture toughness and microstructural parameters, such as mean free path of the cobalt phase, tungsten carbide grain size and the contiguity of tungsten carbide crystals was also made

Microstructure and toughness of ferritic weld metal of hyperbaric welded joints

International Nuclear Information System (INIS)

Mueller, L.

1988-01-01

In the present work ferritic weld metals of hyperbaric MIG/MAG welds with pressures up to 100 bar were examined. As a result of the pressure, interactions with the shielding gas, the filler metal as well as with the welding parameters had to be expected and were consequently included in the analysis. Investigation was focused on the influence of these parameters on the chemical composition of the weld metals, the microstructure and toughness behaviour, including fracture mechanics test. Using quantitative microstructural analysis as well as fractography a correlation between microstructure and toughness has been shown. (orig.) [de

Effect of Li level, artificial aging, and TiB2 reinforcement on the fracture toughness of Weldalite (tm) 049-type alloys

Science.gov (United States)

1991-01-01

Plane strain fracture toughness (K sub IC) was evaluated for Weldalite (tm) 049 with and without TiB2 reinforcement. For the nonreinforced variant, changes in toughness were measured for various aging conditions and lithium levels. Toughness testing was carried out on fatigue precracked compact tension (CT) specimens at 24 C, as per ASTM standard E-399. Toughness was measured as a function of aging time at 160 C for the two Weldalite 049(1.3) heats. The composition of these heats differed only in that 0.03 wt pct. Ti was added to one as an additional grain refiner. Both heats showed a decrease in toughness with increasing aging time, although toughness values for one were significantly higher than for the other. This greater toughness may be due to a subtle change in the grain size resulting for the presence of Ti or, alternatively, to differences in texture or substructure formed during extrusion.

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-09-05

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

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

International Nuclear Information System (INIS)

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

2016-01-01

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

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.

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

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).

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

International Nuclear Information System (INIS)

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

2016-01-01

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

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.

Characterizing and improving the toughness of thick-sectioned 2 1/4 Cr-1 Mo electroslag weldments

Energy Technology Data Exchange (ETDEWEB)

Edwards, G.R.; Frost, R.H.

1980-09-01

Efforts to improve the toughness of electroslag weldments consisted of four endeavors: process control, changes caused in 2 1/4 Cr-1 Mo steel by electroslag welding and post-weld heat treatment, electrochemical reactions during the electroslag welding, and toughness testing.

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

International Nuclear Information System (INIS)

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

1983-08-01

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

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.

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.

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

International Nuclear Information System (INIS)

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

2011-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2011-11-25

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

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

Energy Technology Data Exchange (ETDEWEB)

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

1999-08-01

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

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.

Fracture toughness of heat cured denture base acrylic resin modified with Chlorhexidine and Fluconazole as bioactive compounds.

Science.gov (United States)

Al-Haddad, Alaa; Vahid Roudsari, Reza; Satterthwaite, Julian D

2014-02-01

This study investigated the impact of incorporating Chlorhexidine and Fluconazole as bioactive compounds on the fracture toughness of conventional heat cured denture base acrylic resin material (PMMA). 30 single edge-notched (SEN) samples were prepared and divided into three groups. 10% (mass) Chlorhexidine and 10% (mass) Diflucan powder (4.5% mass Fluconazole) were added to heat cured PMMA respectively to create the two study groups. A third group of conventional heat cured PMMA was prepared as the control group. Fracture toughness (3-point bending test) was carried out for each sample and critical force (Fc) and critical stress intensity factor (KIC) values measured. Data were subject to parametric statistical analysis using one-way ANOVA and Post hoc Bonferroni test (p=0.05). Fluconazole had no significant effect on the fracture toughness of the PMMA while Chlorhexidine significantly reduced the KIC and therefore affected the fracture toughness. When considering addition of a bioactive material to PMMA acrylic, Chlorhexidine will result in reduced fracture toughness of the acrylic base while Fluconazole has no effect. Copyright © 2013 Elsevier Ltd. All rights reserved.

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

Science.gov (United States)

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

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

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

African Journals Online (AJOL)

South African Journal for Research in Sport, Physical Education and Recreation ... mental requirements, team unity, preparation skills, psychological hardiness, ... sport psychologists in strengthening the characteristics of mental toughness ...

Acoustic Emission Methodology to Evaluate the Fracture Toughness in Heat Treated AISI D2 Tool Steel

Science.gov (United States)

Mostafavi, Sajad; Fotouhi, Mohamad; Motasemi, Abed; Ahmadi, Mehdi; Sindi, Cevat Teymuri

2012-10-01

In this article, fracture toughness behavior of tool steel was investigated using Acoustic Emission (AE) monitoring. Fracture toughness ( K IC) values of a specific tool steel was determined by applying various approaches based on conventional AE parameters, such as Acoustic Emission Cumulative Count (AECC), Acoustic Emission Energy Rate (AEER), and the combination of mechanical characteristics and AE information called sentry function. The critical fracture toughness values during crack propagation were achieved by means of relationship between the integral of the sentry function and cumulative fracture toughness (KICUM). Specimens were selected from AISI D2 cold-work tool steel and were heat treated at four different tempering conditions (300, 450, 525, and 575 °C). The results achieved through AE approaches were then compared with a methodology proposed by compact specimen testing according to ASTM standard E399. It was concluded that AE information was an efficient method to investigate fracture characteristics.

Test methodology and technology of fracture toughness for small size specimens

Energy Technology Data Exchange (ETDEWEB)

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

2007-07-01

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

Fracture toughness study of new Zr-based Be-bearing bulk metallic glasses

OpenAIRE

Kim, C. Paul; Suh, Jin-Yoo; Wiest, Aaron; Lind, Mary Laura; Conner, R. Dale; Johnson, William L.

2009-01-01

Three new compositional variants of the Zr–Ti–Be–LTM (late transition metal) family of metallic glasses are discussed. Thermal stability, ΔT = T_x−T_g, was increased from 82 °C for Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5) (Viterloy 1) to 141 °C for Zr_(44)Ti_(11)Cu_(20)Be_(25). It is found that fracture toughness is the most distinguishing parameter characterizing the alloys in contrast to other mechanical properties. Quaternary alloys consistently had fracture toughness values exceeding 8...

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

Science.gov (United States)

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

1980-01-01

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

Sharing Ideas: Tough Times Encourage Colleges to Collaborate

Science.gov (United States)

Fain, Paul; Blumenstyk, Goldie; Sander, Libby

2009-01-01

Tough times are encouraging colleges to share resources in a variety of areas, including campus security, research, and degree programs. Despite its veneer of cooperation, higher education is a competitive industry, where resource sharing is eyed warily. But the recession is chipping away at that reluctance, and institutions are pursuing…

Effect of heat treatment on the elevated temperature tensile and fracture toughness behavior of Alloy 718 weldments

International Nuclear Information System (INIS)

Mills, W.J.

1980-05-01

The effect of heat treatment on the tensile and fracture toughness properties of Alloy 718 weldments was characterized at room temperature and elevated temperatures. The two heat treatments employed during this investigation were the convectional (ASTM A637) precipitation treatment and a modified treatment designed to improve the toughness of Alloy 718 welds. Weldments were also examined in the as-welded condition. The fracture toughness behavior of the Alloy 718 weldments was determined at 24, 427 and 538 degree C using both linear-elastic (K Ic ) and elastic-plastic (J Ic ) fracture mechanics concepts. Metallographic and electron fractographic examination of Alloy 718 weld fracture surfaces revealed that differences in fracture toughness behavior for the as-welded, conventional and modified conditions were associated with variations in the weld microstructure. 28 refs., 16 figs., 4 tabs

Fracture capacity of HFIR vessel with random crack size and toughness

International Nuclear Information System (INIS)

Chang, S.J.

1994-01-01

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

Techniques developed to evaluate the fracture toughness offast breeder reactor duct

International Nuclear Information System (INIS)

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

1979-01-01

Large changes in strength and ductility of metals after irradiation are known to occur. The fracture toughness of irradiated metals, which is related to the combined strength and ductility of a material, may be significantly reduced and the potential for unstable crack extension increased. Therefore, the resistance of cladding and duct materials to fracture after exposure to fast neutron environments is of concern. Existing Type 316 stainless steel irradiated ducts are relatively thin and since this material retains substantial ductility, even after irradiation, the fracture behavior of the duct material cannot be analyzed by linear elastic fracture mechanics techniques. Instead, the multispecimen R-curve method and J-integral analysis were used to develop an experimental approach to evaluate the fracture toughness of thin breeder reactor duct materials irradiated at elevated temperatures. Alloy A-286 was chosen for these experiments because the alloy exhibits elastic/plastic behavior and the fracture toughness data of thicker (12 mm) specimens were available for comparison. Technical problems associated with specimen buckling and remote handling were treated in this work. The results are discussed in terms of thickness criterion for plane strain

Structure-Property Relationships in Tough, Superabsorbent Thermoplastic Elastomers for Hemorrhage Control

Science.gov (United States)

Beyer, Frederick; Bain, Erich; Long, Tyler; Mrozek, Randy; Savage, Alice; Martin, Halie; Dadmun, Mark; Lenhart, Joseph

Between 2001 and 2009, uncontrolled hemorrhaging from major trauma accounted for the deaths of roughly 80% of wounded soldiers with potentially survivable injuries. Modern hemostatic materials are limited in their ability to deliver therapeutic agents, causing tissue damage themselves, or being difficult to remove intact. The goal of this study is to create a mechanically robust polymer that takes up as much as 1000 wt% water in seconds while maintaining sufficient toughness to be removed intact from the wound intact. A thermoplastic elastomer scaffold in which physical crosslinks provide mechanical toughness might provide an appropriate combination of fast swelling and excellent toughness if the matrix material can be engineered to be strongly hydrophilic and swell rapidly. In this work, a commercial SBS triblock copolymer has been modified with poly(acrylic acid) side chains, resulting in materials that are superabsorbent but retain good mechanical properties when saturated. Although SAXS experiments failed to show any significant changes in morphology, even with 800 wt% water uptake, preliminary SANS experiments using selectively deuterated materials and swelling with D2O show significant changes in morphology. Our most recent findings will be presented.

Measurement of tensile and fracture toughness properties using small punch test

International Nuclear Information System (INIS)

Chatterjee, S.; Shah Priti Kotak

2005-05-01

Small punch test wu carried out at room temperature on five different steels using 10 mm by 10 mm specimens of 0.4 mm thickness in a univesal testing machine. The tensile and fracture toughness properties of the five steels obtained from small punch test were compared with those obtained from the standard test method. The results (except in one steel) show that the tensile properties obtained from small punch test are in close proximity to those obtained ftom uni-axial tension test. The results also show that fracture toughness (Jic) properties obtained ftom small punch test are within ±20% of the corresponding values obtained using standard test procedures. (author)

Fracture toughness of irradiated Zr-2.5Nb pressure tube from Indian PHWR

Science.gov (United States)

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

2015-03-01

Fracture toughness of irradiated Zr-2.5Nb alloy pressure tube, fabricated by the cold pilgering and stress relieving route, was evaluated using disk compact tension type specimens. These specimens were punched out from the irradiated pressure tube (S-07), which was in service for about 8 effective full power years of reactor operation in the Kakrapar Atomic Power Station-2 (KAPS-2). The tests were carried out remotely inside a lead shielded enclosure. Crack growth during the test was measured using the direct current potential drop technique. The irradiated pressure tube showed low fracture toughness at 25 °C. The fracture toughness increased with increase in temperature up to 250 °C but was practically unaffected with further increase in temperature up to 300 °C. This paper discusses the fracture behavior of irradiated Indian pressure tube material and compares it with other data available.

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

International Nuclear Information System (INIS)

Lucon, E.

2008-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

Lucon, E.

2008-09-15

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

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

Energy Technology Data Exchange (ETDEWEB)

Lucon, E.; Scibetta, M.

2009-05-15

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

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.

A top-down approach for the prediction of hardness and toughness of hierarchical materials

International Nuclear Information System (INIS)

Carpinteri, Alberto; Paggi, Marco

2009-01-01

Many natural and man-made materials exhibit structure over more than one length scale. In this paper, we deal with hierarchical grained composite materials that have recently been designed to achieve superior hardness and toughness as compared to their traditional counterparts. Their nested structure, where meso-grains are recursively composed of smaller and smaller micro-grains at the different scales with a fractal-like topology, is herein studied from a hierarchical perspective. Considering a top-down approach, i.e. from the largest to the smallest scale, we propose a recursive micromechanical model coupled with a generalized fractal mixture rule for the prediction of hardness and toughness of a grained material with n hierarchical levels. A relationship between hardness and toughness is also derived and the analytical predictions are compared with experimental data.

Fracture toughness testing of pipeline girth welds

Energy Technology Data Exchange (ETDEWEB)

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

2005-06-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2008-05-10

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

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

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.

Characterizing the toughness of an epoxy resin after wet aging using compact tension specimens with non-uniform moisture content

KAUST Repository

Quino, Gustavo; El Yagoubi, Jalal; Lubineau, Gilles

2014-01-01

Characterizing the change in toughness of polymers subjected to wet aging is challenging because of the heterogeneity of the testing samples. Indeed, as wet aging is guided by a diffusion/reaction process, compact tension samples (defined by the ASTM D5045 standard), which are relevant for toughness characterization but are somewhat thick, display a non-uniform moisture content over the bulk material. We define here a rigorous procedure to extract meaningful data from such tests. Our results showed that the relation between the moisture uptake of the whole sample and the measured toughness was not a meaningful material property. In fact, we found that the measured toughness depended on the locally varying moisture uptake over the cracking path. Here, we propose a post-processing technique that relies on a validated reaction/diffusion model to predict the three-dimensional moisture state of the epoxy. This makes identification of the variation in toughness with respect to the local moisture content possible. In addition, we analyze the fracture surface using micrography and roughness measurements. The observed variations in toughness are correlated with the roughness in the vicinity of the crack tip. © 2014 Elsevier Ltd. All rights rese.

Characterizing the toughness of an epoxy resin after wet aging using compact tension specimens with non-uniform moisture content

KAUST Repository

Quino, Gustavo

2014-11-01

Characterizing the change in toughness of polymers subjected to wet aging is challenging because of the heterogeneity of the testing samples. Indeed, as wet aging is guided by a diffusion/reaction process, compact tension samples (defined by the ASTM D5045 standard), which are relevant for toughness characterization but are somewhat thick, display a non-uniform moisture content over the bulk material. We define here a rigorous procedure to extract meaningful data from such tests. Our results showed that the relation between the moisture uptake of the whole sample and the measured toughness was not a meaningful material property. In fact, we found that the measured toughness depended on the locally varying moisture uptake over the cracking path. Here, we propose a post-processing technique that relies on a validated reaction/diffusion model to predict the three-dimensional moisture state of the epoxy. This makes identification of the variation in toughness with respect to the local moisture content possible. In addition, we analyze the fracture surface using micrography and roughness measurements. The observed variations in toughness are correlated with the roughness in the vicinity of the crack tip. © 2014 Elsevier Ltd. All rights rese.

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

International Nuclear Information System (INIS)

Fabry, A.

1997-01-01

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

Crack arrest toughness of structural steels evaluated by compact test

International Nuclear Information System (INIS)

Nakano, Yoshifumi; Tanaka, Michihiro

1982-01-01

Crack arrest tests such as compact, ESSO and DCB tests were made on SA533B Cl. 1, HT80 and KD32 steels to evaluate the crack arrest toughness. The main results obtained are as follows: (1) The crack arrest toughness could be evaluated by K sub(Ia) which was obtained by the static analysis of compact test. (2) K sub(ID) determined by the dynamic analysis of compact test was greater than K sub(Ia), though K sub(ID) became close to K sub(Ia)/K sub(Q) became a unity where K sub(Q) is the stress intensity factor at the crack initiation. (3) No significant difference was observed between K sub(Ia) and K sub(ca) obtained by ESSO and DCB tests, though K sub(ca) obtained by DCB test tended to be smaller than K sub(Ia) at lower temperatures. (4) K sub(Ia) was smaller than K sub(Ic) in the transition temperature range, while it was greater than K sub(Id). In the temperature range where K sub(Ic), which was determined from J sub(Ic), decreased with temperature increase, however, it was smaller than K sub(Ia). (5) The fracture appearance transition temperature and the absorbed energy obtained by 2 mm V-notch Charpy test were appropriate parameters for representing the crack arrest toughness, while the NDT temperature was not. (author)

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.

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.

EOS7R: Radionuclide transport for TOUGH2

International Nuclear Information System (INIS)

Oldenburg, C.M.; Pruess, K.

1995-11-01

EOS7R provides radionuclide transport capability for TOUGH2. EOS7R extends the EOS7 module (water, brine, and optional air) to model water, brine, parent component, daughter component, and optional air and heat. The radionuclide components follow a first-order decay law, and may adsorb onto the solid grains. Volatilization of the decaying components is modeled by Henry's Law. The decaying components are normally referred to as radionuclides, but they may in fact by any trace components that decay, adsorb, and volatilize. The decay process need not be radioactive decay, but could be any process that follows a first-order decay law, such as biodegradation. EOS7R includes molecular diffusion for all components in gaseous and aqueous phases using a simplified binary diffusion model. When EOS7R is used with standard TOUGH2, transport occurs by advection and molecular diffusion in all phases. When EOS7R is coupled with the dispersion module T2DM, one obtains T2DMR, the radionuclide transport version of T2DM. T2DMR models advection, diffusion, and hydrodynamic dispersion in rectangular two-dimensional regions. Modeling of radionuclide transport requires input parameters specifying the half-life for first-order decay, distribution coefficients for each rock type for adsorption, and inverse Henry's constants for volatilization. Options can be specified in the input file to model decay in inactive grid blocks and to read from standard EOS7 INCON files. The authors present a number of example problems to demonstrate application and accuracy of TOUGH2/EOS7R. One-dimensional simulation results agree well with analytical solutions. For a two-dimensional salt-dome flow problem, the final distribution of daughter radionuclide component is complicated by the presence of weak recirculation caused by density effects due to salinity

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

International Nuclear Information System (INIS)

Miyata, T.; Tagawa, T.

1996-01-01

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

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

Science.gov (United States)

Sankar, Bhavani V.; Sharma, Suresh

1995-01-01

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

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

International Nuclear Information System (INIS)

Vecchio, Kenneth S.; Jiang, Fengchun

2016-01-01

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

Fracture toughness measurements with subsize disk compact specimens

International Nuclear Information System (INIS)

Alexander, D.J.

1992-01-01

Special fixtures and test methods are necessary to facilitate the fracture toughness testing of small disk compact specimens of irradiated candidate materials for first-wall fusion applications. New methods have been developed for both the unloading compliance and potential drop techniques of monitoring crack growth. Provisions have been made to allow the necessary probes and instrumentation to be installed remotely using manipulators for testing of irradiated specimens in a hot cell. Laboratory trials showed that both unloading compliance and potential drop gave useful results. Both techniques gave similar data, and predicted the final crack extension within allowable limits. The results from the small disk compact specimens were similar to results from conventional compact specimen 12.7 mm thick. However, the slopes of the J-R curves from the larger specimens were lower, suggesting that the smaller disk compact specimens may have lost some constraint due to their size. The testing shows that it should be possible to generate useful J-R curve fracture toughness data from the small disk compact specimens

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

International Nuclear Information System (INIS)

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

1996-01-01

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

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

International Nuclear Information System (INIS)

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

1997-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2009-07-01

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

Influence of grain boundaries on the fracture toughness of tungsten alloys

International Nuclear Information System (INIS)

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

2007-01-01

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

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)

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.

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

Directory of Open Access Journals (Sweden)

Z. Q. Yin

2014-03-01

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

Aspects of the Fracture Toughness of Carbon Nanotube Modified Epoxy Polymer Composites

Science.gov (United States)

Mirjalili, Vahid

Epoxy resins used in fibre reinforced composites exhibit a brittle fracture behaviour, because they show no sign of damage prior to a catastrophic failure. Rubbery materials and micro-particles have been added to epoxy resins to improve their fracture toughness, which reduces strength and elastic properties. In this research, carbon nanotubes (CNTs) are investigated as a potential toughening agent for epoxy resins and carbon fibre reinforced composites, which can also enhance strength and elastic properties. More specifically, the toughening mechanisms of CNTs are investigated theoretically and experimentally. The effect of aligned and randomly oriented carbon nanotubes (CNTs) on the fracture toughness of polymers was modelled using Elastic Plastic Fracture Mechanics. Toughening from CNT pull-out and rupture were considered, depending on the CNTs critical length. The model was used to identify the effect of CNTs geometrical and mechanical properties on the fracture toughness of CNT-modified epoxies. The modelling results showed that a uniform dispersion and alignment of a high volume fraction of CNTs normal to the crack growth plane would lead to the maximum fracture toughness enhancement. To achieve a uniform dispersion, the effect of processing on the dispersion of single walled and multi walled CNTs in epoxy resins was investigated. An instrumented optical microscope with a hot stage was used to quantify the evolution of the CNT dispersion during cure. The results showed that the reduction of the resin viscosity at temperatures greater than 100 °C caused an irreversible re-agglomeration of the CNTs in the matrix. The dispersion quality was then directly correlated to the fracture toughness of the modified resin. It was shown that the fine tuning of the ratio of epoxy resin, curing agent and CNT content was paramount to the improvement of the base resin fracture toughness. For the epoxy resin (MY0510 from Hexcel), an improvement of 38% was achieved with 0.3 wt

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

Science.gov (United States)

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

2018-05-18

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

2015 Accomplishments-Tritium aging studies on stainless steel. Effects of hydrogen isotopes, crack orientation, and specimen geometry on fracture toughness

Energy Technology Data Exchange (ETDEWEB)

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

2016-01-01

This study reports on the effects of hydrogen isotopes, crack orientation, and specimen geometry on the fracture toughness of stainless steels. Fracture toughness variability was investigated for Type 21-6-9 stainless steel using the 7K0004 forging. Fracture toughness specimens were cut from the forging in two different geometric configurations: arc shape and disc shape. The fracture toughness properties were measured at ambient temperature before and after exposure to hydrogen gas and compared to prior studies. There are three main conclusions that can be drawn from the results. First, the fracture toughness properties of actual reservoir forgings and contemporary heats of steel are much higher than those measured in earlier studies that used heats of steel from the 1980s and 1990s and forward extruded forgings which were designed to simulate reservoir microstructures. This is true for as-forged heats as well as forged heats exposed to hydrogen gas. Secondly, the study confirms the well-known observation that cracks oriented parallel to the forging grain flow will propagate easier than those oriented perpendicular to the grain flow. However, what was not known, but is shown here, is that this effect is more pronounced, particularly after hydrogen exposures, when the forging is given a larger upset. In brick forgings, which have a relatively low amount of upset, the fracture toughness variation with specimen orientation is less than 5%; whereas, in cup forgings, the fracture toughness is about 20% lower than that forging to show how specimen geometry affects fracture toughness values. The American Society for Testing Materials (ASTM) specifies minimum specimen section sizes for valid fracture toughness values. However, sub-size specimens have long been used to study tritium effects because of the physical limitation of diffusing hydrogen isotopes into stainless steel at mild temperatures so as to not disturb the underlying forged microstructure. This study shows

Tough Times: Strategic Planning as a War Canoe

Science.gov (United States)

Seymour, Daniel

2011-01-01

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

Toughness of 2,25Cr-1Mo steel and weld metal

Science.gov (United States)

Acarer, Mustafa; Arici, Gökhan; Acar, Filiz Kumdali; Keskinkilic, Selcuk; Kabakci, Fikret

2017-09-01

2,25Cr-1Mo steel is extensively used at elevated temperature structural applications in fossil fire power plants for steam pipes, nozzle chambers and petrochemical industry for hydrocracking unit due to its excellent creep resistance and good redundant to oxidation. Also they should have acceptable weldability and toughness. The steels are supplied in quenched and tempered condition and their welded components are subjected to post-weld heat treatment (PWHT). Tempering process is carried out at 690-710°C to improve toughness properties. However they are sensitive to reheat cracking and temper embrittlement. To measure temper embrittlement of the steels and their weld metal, temper embrittlement factor and formula (J factor - Watanabe and X formula- Bruscato) are used. Step cooling heat treatment is also applied to determine temper embrittlement. In this study, toughness properties of Cr Mo (W) steels were reviewed. Also transition temperature curves of 2,25Cr-1Mo steel and its weld metal were constructed before and after step cool heat treatment as experimental study. While 2,25Cr-1Mo steel as base metal was supplied, all weld metal samples were produced in Gedik Welding Company. Hardness measurements and microstructure evaluation were also carried out.

Effect of Control Mode and Test Rate on the Measured Fracture Toughness of Advanced Ceramics

Science.gov (United States)

Hausmann, Bronson D.; Salem, Jonathan A.

2018-01-01

The effects of control mode and test rate on the measured fracture toughness of ceramics were evaluated by using chevron-notched flexure specimens in accordance with ASTM C1421. The use of stroke control gave consistent results with about 2% (statistically insignificant) variation in measured fracture toughness for a very wide range of rates (0.005 to 0.5 mm/min). Use of strain or crack mouth opening displacement (CMOD) control gave approx. 5% (statistically significant) variation over a very wide range of rates (1 to 80 µm/m/s), with the measurements being a function of rate. However, the rate effect was eliminated by use of dry nitrogen, implying a stress corrosion effect rather than a stability effect. With the use of a nitrogen environment during strain controlled tests, fracture toughness values were within about 1% over a wide range of rates (1 to 80 micons/m/s). CMOD or strain control did allow stable crack extension well past maximum force, and thus is preferred for energy calculations. The effort is being used to confirm recommendations in ASTM Test Method C1421 on fracture toughness measurement.

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

Evaluation of dynamic fracture toughness of cold worked 9Cr-1Mo steel

International Nuclear Information System (INIS)

Sathyanarayanan, S.; Sasikala, G.; Ray, S.K.

2004-01-01

Dynamic J-R curves for cold worked 9Cr-1Mo steel have been estimated from instrumented impact test data at ambient temperature on pre-cracked Charpy specimens using three methods of analysis, namely those by Ray et al., Schindler, and Sreenivasan and Mannan. It is concluded that of these three, Schindler's method is the best suited for the purpose since it gives consistent variations with cold work of dynamic J-R curves and dynamic fracture toughness. Cold work results in substantial degradation in dynamic fracture toughness of 9Cr-1Mo steel

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

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

DEFF Research Database (Denmark)

Berggreen, Christian; Quispitupa, Amilcar; Costache, Andrei

2014-01-01

The modified tilted sandwich debond (TSD) test method is used to examine face/core debond fracture toughness of sandwich specimens with glass/polyester face sheets and PVC H45 and H100 foam cores over a large range of mode-mixities. The modification was achieved by reinforcing the loaded face sheet....... The fracture process was inspected visually during and after testing. For specimens with H45 core the crack propagated in the core. For specimens with an H100 core, the crack propagated between the resin-rich layer and the face sheet. © The Author(s) 2013 Reprints and permissions: sagepub...... with a steel bar, and fracture testing of the test specimens was conducted over a range of tilt angles. The fracture toughness exhibited mode-mixity phase angle dependence, especially for mode II dominated loadings; although, the fracture toughness remained quite constant for mode I dominated crack loadings...

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

Energy Technology Data Exchange (ETDEWEB)

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

2006-01-01

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

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

Effect of microstructure on the fracture toughness of ferrite-martensite-bainite steels

International Nuclear Information System (INIS)

Byun, Thak Sang; Kim, In Sup

1988-01-01

The effect of microstructure on the fracture toughness of ferrite-martensite -bainite steels was investigated with Fe-0.11C-1.64Mn-0.78Si composition. One inch compact tension specimens (1T-CTSs) were machined from hot rolled plates. The microstructure of ferrite-martensite-bainite was introduced to the specimens by the heat treatment of intercritical annealing at 800deg C and isothermal holding at 350deg C. Holding at 350deg C increased volume fraction of bainite, while decreased that of martensite, and refined martensite particles. Single specimen unloading compliance method was used in fracture test to obtain J-resistance (J-R) curve and to determine the fracture toughness(J IC ). Introduction of bainite to the ferrite-martensite steel improved the fracture toughness due to the deformation of bainite which relaxed the stress concentration on the interface of ferrite and martensite. Observation of fracto-graphs through the scanning electron microscope(SEM) identified the fracture mechanism of ferrite-martensite-bainite steels as dimple nucleation and crack growth by decohesion of ferrite matrix and second phase particles and by microvoid coales cence. (Author)

Improvement of impact toughness by modified hot working and heat treatment in 13%Cr martensitic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Srivatsa, Kulkarni, E-mail: srivatsa.kulkarni@kcssl.com; Srinivas, Perla; Balachandran, G.; Balasubramanian, V.

2016-11-20

Improvement of the general mechanical properties and in particular sub-zero impact toughness in a 0.2%C-13%Cr martensitic stainless steel has been explored by varying the hot deformation and heat treatment conditions. The deformation conditions include hot rolling an ingot in one case and cogging the ingot to a semis followed by hot rolling in another case. The bars made from both routes were subjected to a single hardening heat treatment at 980 °C and 1040 °C oil quenched and a double hardening heat treatment at 1040 °C followed by 980 °C oil quenched. The hardened steels were subjected to a standard two stage tempering at 710 °C followed by 680 °C. The impact toughness was found to be doubled in the cogged and rolled steel in double hardened condition. Other processing conditions show varying impact toughness levels. The toughness observed was correlated to the grain size and the carbide distribution in the matrix and the fractography features.

Fracture toughness requirements of reactor vessel material in evaluation of the safety analysis report of nuclear power plants

International Nuclear Information System (INIS)

Widia Lastana Istanto

2011-01-01

Fracture toughness requirements of reactor vessel material that must be met by applicants for nuclear power plants construction permit has been investigated in this paper. The fracture toughness should be described in the Safety Analysis Reports (SARs) document that will be evaluated by the Nuclear Energy Regulatory Agency (BAPETEN). Because BAPETEN does not have a regulations or standards/codes regarding the material used for the reactor vessel, especially in the fracture toughness requirements, then the acceptance criteria that applied to evaluate the fracture toughness of reactor vessel material refers to the regulations/provisions from the countries that have been experienced in the operation of nuclear power plants, such as from the United States, Japan and Korea. Regulations and standards used are 10 CFR Part 50, ASME and ASTM. Fracture toughness of reactor vessel materials are evaluated to ensure compliance of the requirements and provisions of the Regulatory Body and the applicable standards, such as ASME or ASTM, in order to assure a reliability and integrity of the reactor vessels as well as providing an adequate safety margin during the operation, testing, maintenance, and postulated accident conditions over the reactor vessel lifetime. (author)

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.

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

Energy Technology Data Exchange (ETDEWEB)

Fabry, A.

1997-01-01

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

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.

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

Use of forces from instrumented Charpy V-notch testing to determine crack-arrest toughness

International Nuclear Information System (INIS)

Iskander, S.K.; Nanstad, R.K.; Sokolov, M.A.; McCabe, D.E.; Hutton, J.T.

1996-06-01

The objective of this investigation is an estimation of the crack-arrest toughness, particularly of irradiated materials, from voltage versus time output of an instrumented setup during a test on a Charpy V-notch (CVN) specimen. This voltage versus time trace (which can be converted to force versus displacement) displays events during fracture of the specimen. Various stages of the fracture process can be identified on the trace, including an arrest point indicating arrest of brittle fracture. The force at arrest, F a , versus test temperature, T, relationship is examined to explore possible relationships to other experimental measures of crack-arrest toughness such as the drop-weight nil-ductility temperature (NDT), or crack-arrest toughness, K a . For a wide range of weld and plate materials, the temperature at which F a = 2.45 kN correlates with NDT with a standard deviation, sigma, of about 11 K. Excluding the so-called low upper-shelf energy (USE) welds from the analysis resulted in F a = 4.12 kN and σ = 6.6 K. The estimates of the correlation of the temperature for F a = 7.4 kN with the temperature at 100-MPa√m level for a mean American Society of Mechanical Engineers (ASME) type K Ia curve through crack-arrest toughness values show that prediction of conservative values of K a are possible

Correlation of microstructure and fracture toughness of advanced 9Cr/CrMoV dissimilarly welded joint

Energy Technology Data Exchange (ETDEWEB)

Guo, Qian [Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Lu, Fenggui, E-mail: Lfg119@sjtu.edu.cn [Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Liu, Xia [Shanghai Turbine Plant of Shanghai Electric Power Generation Equipment Co. Ltd., Shanghai 200240 (China); Yang, Renjie [Shanghai Turbine Works Company, Shanghai 200240 (China); Cui, Haichao [Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Gao, Yulai, E-mail: ylgao@shu.edu.cn [State Key Laboratory of Advanced Special Steels, Shanghai University, Shanghai 200072 (China)

2015-06-25

In this paper, the fracture toughness and the related microstructure characteristics of dissimilarly welded joint manufactured by advanced 9Cr and CrMoV steels were systematically investigated. The dissimilarly welded joint was fabricated by narrow gap submerged arc welding (NG-SAW) applying multi-layer and multi-pass technique. Fracture toughness, as one of the most important property to assess the reliability of welded joint, was studied for different regions including CrMoV base metal (CrMoV-BM), heat affected zone (HAZ) of CrMoV side (CrMoV-HAZ), weld metal (WM), heat affected zone of 9Cr side (9Cr-HAZ) and 9Cr base metal (9Cr-BM). It was found that the fracture toughness of CrMoV-BM, CrMoV-HAZ and WM was better than that of 9Cr-HAZ and 9Cr-BM. In order to illustrate these results, the microstructure of the whole welded joint was observed by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM) detailedly. It was found that the fine high-temperature tempered martensite and bainite in WM, CrMoV-BM and CrMoV-HAZ contribute to the higher fracture toughness, while lower fracture toughness for 9Cr-BM and HAZ was caused by coarse tempered lath-martensite. Furthermore, the fracture morphology showed that ductile fracture occurred in WM and CrMoV side, while brittle fracture appeared in BM and HAZ of 9Cr side.

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

Science.gov (United States)

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

2015-01-28

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

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...

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

Science.gov (United States)

Chang, Ling-Hui; Wang, Jye

2009-09-01

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

A model for fracture toughness evaluation of the carburized layer for SAE 5115 steel

OpenAIRE

Sandor, Leonardo Taborda; Ferreira, Itamar

2006-01-01

The purpose of this work is to propose a model for evaluating the fracture toughness along the SAE 5115 steel carburized layer. Due to the small thickness of those layers, it is impossible to machine specimens from those layer in accordance with standards. For simulating the microstructures of the carburized layer in order to get samples for tensile and the fracture toughness testing, specimens of SAE 5115, 5140, 5160, and 52100 steels have been machined, assuming the local influence just the...

Tough nanocomposite ionogel-based actuator exhibits robust performance.

Science.gov (United States)

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

2014-10-20

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

Development of Fracture Toughness Evaluation Method for Composite Materials by Non-Destructive Testing Method

International Nuclear Information System (INIS)

Lee, Y. T.; Kim, K. S.

1998-01-01

Fracture process of continuous fiber reinforced composites is very complex because various fracture mechanisms such as matrix cracking, debonding, delamination and fiber breaking occur simultaneously during crack growth. If fibers cause crack bridging during crack growth, the stable crack growth and unstable crack growth appear repeatedly. Therefore, it is very difficult to exactly determine tile starting point of crack growth and the fracture toughness at the critical crack length in composites. In this research, fracture toughness test for CFRP was accomplished by using acoustic emission(AE) and recording of tile fracture process in real time by video-microscope. The starting point of crack growth, pop-in point and the point of unstable crack growth can be exactly determined. Each fracture mechanism can be classified by analyzing the fracture process through AE and video-microscope. The more reliable method is the fracture toughness measurement of composite materials was proposed by using the combination of R-curve method, AE and video microscope

Measurement of the fracture toughness of polycrystalline bubbly ice from an Antarctic ice core

Directory of Open Access Journals (Sweden)

J. Christmann

2015-05-01

Full Text Available The critical fracture toughness is a material parameter describing the resistance of a cracked body to further crack extension. It is an important parameter for simulating and predicting the breakup behavior of ice shelves from the calving of single icebergs to the disintegration of entire ice shelves over a wide range of length scales. The fracture toughness values are calculated with equations that are derived from an elastic stress analysis. Additionally, an X-ray computer tomography (CT scanner was used to identify the density as a function of depth. The critical fracture toughness of 91 Antarctic bubbly ice samples with densities between 840 and 870 kg m−3 has been determined by applying a four-point bending technique on single-edge v-notched beam samples. The examined ice core was drilled 70 m north of Kohnen Station, Dronnning Maud Land (75°00' S, 00°04' E; 2882 m. Supplementary data are available at doi:10.1594/PANGAEA.835321.

Fracture Toughness and Elastic Modulus of Epoxy-Based Nanocomposites with Dopamine-Modified Nano-Fillers

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Kwang Liang Koh

2017-07-01

Full Text Available This paper examines the effect of surface treatment and filler shape factor on the fracture toughness and elastic modulus of epoxy-based nanocomposite. Two forms of nanofillers, polydopamine-coated montmorillonite clay (D-clay and polydopamine-coated carbon nanofibres (D-CNF were investigated. It was found that Young’s modulus increases with increasing D-clay and D-CNF loading. However, the fracture toughness decreases with increased D-clay loading but increases with increased D-CNF loading. Explanations have been provided with the aid of fractographic analysis using electron microscope observations of the crack-filler interactions. Fractographic analysis suggests that although polydopamine provides a strong adhesion between the fillers and the matrix, leading to enhanced elastic stiffness, the enhancement prohibits energy release via secondary cracking, resulting in a decrease in fracture toughness. In contrast, 1D fibre is effective in increasing the energy dissipation during fracture through crack deflection, fibre debonding, fibre break, and pull-out.

Fracture Toughness and Elastic Modulus of Epoxy-Based Nanocomposites with Dopamine-Modified Nano-Fillers

Science.gov (United States)

Koh, Kwang Liang; Ji, Xianbai; Lu, Xuehong; Lau, Soo Khim; Chen, Zhong

2017-01-01

This paper examines the effect of surface treatment and filler shape factor on the fracture toughness and elastic modulus of epoxy-based nanocomposite. Two forms of nanofillers, polydopamine-coated montmorillonite clay (D-clay) and polydopamine-coated carbon nanofibres (D-CNF) were investigated. It was found that Young’s modulus increases with increasing D-clay and D-CNF loading. However, the fracture toughness decreases with increased D-clay loading but increases with increased D-CNF loading. Explanations have been provided with the aid of fractographic analysis using electron microscope observations of the crack-filler interactions. Fractographic analysis suggests that although polydopamine provides a strong adhesion between the fillers and the matrix, leading to enhanced elastic stiffness, the enhancement prohibits energy release via secondary cracking, resulting in a decrease in fracture toughness. In contrast, 1D fibre is effective in increasing the energy dissipation during fracture through crack deflection, fibre debonding, fibre break, and pull-out. PMID:28773136

Enhancement of Fracture Toughness of Epoxy Nanocomposites by Combining Nanotubes and Nanosheets as Fillers.

Science.gov (United States)

Domun, Nadiim; Paton, Keith R; Hadavinia, Homayoun; Sainsbury, Toby; Zhang, Tao; Mohamud, Hibaaq

2017-10-19

In this work the fracture toughness of epoxy resin has been improved through the addition of low loading of single part and hybrid nanofiller materials. Functionalised multi-walled carbon nanotubes (f-MWCNTs) was used as single filler, increased the critical strain energy release rate, G IC , by 57% compared to the neat epoxy, at only 0.1 wt% filler content. Importantly, no degradation in the tensile or thermal properties of the nanocomposite was observed compared to the neat epoxy. When two-dimensional boron nitride nanosheets (BNNS) were added along with the one-dimensional f-MWCNTs, the fracture toughness increased further to 71.6% higher than that of the neat epoxy. Interestingly, when functionalised graphene nanoplatelets (f-GNPs) and boron nitride nanotubes (BNNTs) were used as hybrid filler, the fracture toughness of neat epoxy is improved by 91.9%. In neither of these hybrid filler systems the tensile properties were degraded, but the thermal properties of the nanocomposites containing boron nitride materials deteriorated slightly.

Enhancement of Fracture Toughness of Epoxy Nanocomposites by Combining Nanotubes and Nanosheets as Fillers

Directory of Open Access Journals (Sweden)

Nadiim Domun

2017-10-01

Full Text Available In this work the fracture toughness of epoxy resin has been improved through the addition of low loading of single part and hybrid nanofiller materials. Functionalised multi-walled carbon nanotubes (f-MWCNTs was used as single filler, increased the critical strain energy release rate, GIC, by 57% compared to the neat epoxy, at only 0.1 wt% filler content. Importantly, no degradation in the tensile or thermal properties of the nanocomposite was observed compared to the neat epoxy. When two-dimensional boron nitride nanosheets (BNNS were added along with the one-dimensional f-MWCNTs, the fracture toughness increased further to 71.6% higher than that of the neat epoxy. Interestingly, when functionalised graphene nanoplatelets (f-GNPs and boron nitride nanotubes (BNNTs were used as hybrid filler, the fracture toughness of neat epoxy is improved by 91.9%. In neither of these hybrid filler systems the tensile properties were degraded, but the thermal properties of the nanocomposites containing boron nitride materials deteriorated slightly.

European experiences of the proposed ASTM test method for crack arrest toughness of ferritic materials

International Nuclear Information System (INIS)

Jutla, T.; Lidbury, D.P.G.; Ziebs, J.; Zimmermann, C.

1986-01-01

The proposed ASTM test method for measuring the crack arrest toughness of ferritic materials using wedge-loaded, side-grooved, compact specimens was applied to three steels: A514 bridge steel, A588 bridge steel, and A533B pressure vessel steel. Five sets of results from different laboratories are discussed here. Notches were prepared by spark erosion, although root radii varied from ∝0.1-1.5 mm. Although fast fractures were successfully initiated, arrest did not occur in a significant number of cases. The results showed no obvious dependence of crack arrest toughness, K a , (determined by a static analysis) on crack initiation toughness, K 0 . It was found that K a decreases markedly with increasing crack jump distance. A limited amount of further work on smaller specimens of the A533B steel showed that lower K a values tended to be recorded. It is concluded that a number of points relating to the proposed test method and notch preparation are worthy of further consideration. It is pointed out that the proposed validity criteria may screen out lower bound data. Nevertheless, for present practical purposes, K a values may be regarded as useful in providing an estimate of arrest toughness - although not necessarily a conservative estimate. (orig./HP)

Investigation on Microstructure and Impact Toughness of Different Zones in Duplex Stainless Steel Welding Joint

Science.gov (United States)

Zhang, Zhiqiang; Jing, Hongyang; Xu, Lianyong; Han, Yongdian; Li, Guolu; Zhao, Lei

2017-01-01

This paper investigated on microstructure and impact toughness of different zones in duplex stainless steel welding joint. High-temperature heat-affected zone (HTHAZ) contained coarse ferrite grains and secondary precipitates such as secondary austenite, Cr2N, and sigma. Intergranular secondary austenite was prone to precipitation in low-temperature heat-affected zone (LTHAZ). Both in weld metal (WM) and in HTHAZ, the austenite consisted of different primary and secondary austenite. The ferrite grains in base metal (BM) presented typical rolling texture, while the austenite grains showed random orientation. Both in the HTHAZ and in the LTHAZ, the ferrite grains maintained same texture as the ferrite in the BM. The secondary austenite had higher Ni but lower Cr and Mo than the primary austenite. Furthermore, the WM exhibited the highest toughness because of sufficient ductile austenite and unapparent ferrite texture. The HTHAZ had the lowest toughness because of insufficient austenite formation in addition to brittle sigma and Cr2N precipitation. The LTHAZ toughness was higher than the BM due to secondary austenite precipitation. In addition, the WM fracture was dominated by the dimple, while the cleavage was main fracture mode of the HTHAZ. Both BM and LTHAZ exhibited a mixed fracture mode of the dimple and quasi-cleavage.

Next generation self-shielded flux cored electrode with improved toughness for off shore oil well platform structures

Energy Technology Data Exchange (ETDEWEB)

Singh, Daya; Soltis, Patrick; Narayanan, Badri; Quintana, Marie; Fox, Jeff [The Lincoln Electric Company (United States)

2005-07-01

Self-shielded flux cored arc welding electrodes (FCAW-S) are ideal for outdoor applications, particularly open fabrication yards where high winds are a possibility. Development work was carried out on a FCAW-S electrode for welding 70 and 80 ksi yield strength base materials with a required minimum average Charpy V-Notch (CVN) absorbed energy value of 35 ft-lb at -40 deg F in the weld metal. The effect of Al, Mg, Ti, and Zr on CVN toughness was evaluated by running a Design of Experiments approach to systematically vary the levels of these components in the electrode fill and, in turn, the weld metal. These electrodes were used to weld simulated pipe joints. Over the range of compositions tested, 0.05% Ti in the weld metal was found to be optimum for CVN toughness. Ti also had a beneficial effect on the usable voltage range. Simulated offshore joints were welded to evaluate the effect of base metal dilution, heat input, and welding procedure on the toughness of weld metal. CVN toughness was again measured at -40 deg F on samples taken from the root and the cap pass regions. The root pass impact toughness showed strong dependence on the base metal dilution and the heat input used to weld the root and fill passes. (author)

A new method for improving the reliability of fracture toughness surveillance of nuclear pressure vessel by neutron irradiated embrittlement

International Nuclear Information System (INIS)

Zhang Xinping; Shi Yaowu

1992-01-01

In order to obtain more information from neutron irradiated sample specimens and raise the reliability of fracture toughness surveillance test, it has more important significance to repeatedly exploit the broken Charpy-size specimen which had been tested in surveillance test. In this work, on the renewing design and utilization for Charpy-size specimens, 9 data of fracture toughness can be gained from one pre-cracked side-grooved Charpy-size specimen while at the preset usually only 1 to 3 data of fracture toughness can be obtained from one Chharpy-size specimen. Thus, it is found that the new method would obviously improve the reliability of fracture toughness surveillance test and evaluation. Some factors which affect the reasonable design of pre-cracked deep side-groove Charpy-size compound specimen have been discussed

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

DEFF Research Database (Denmark)

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

2008-01-01

-tolerant or gap-demanding species were considered. Conclusions: 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.   Key words: Dicots, fracture toughness, herbivory, leaves, monocots, punch strength, tropical rain forest  ...

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

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

Directory of Open Access Journals (Sweden)

Flavio Teixeira da Silva

2007-03-01

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

Allowable minimum upper shelf toughness for nuclear reactor pressure vessels

Energy Technology Data Exchange (ETDEWEB)

Zahoor, A.

1988-05-01

The paper develops methodology and procedure for determining the allowable minimum upper shelf toughness for continued safe operation of nuclear reactor pressure vessels. Elastic-plastic fracture mechanics analysis method based on the J-integral tearing modulus (J/T) approach is used. Closed from expressions for the applied J and tearing modulus are presented for finite length, part-throughwall axial flaw with aspect ratio of 1/6. Solutions are then presented for Section III, Appendix G flaw. A simple flaw evaluation procedure that can be applied quickly by utility engineers is presented. An attractive feature of the simple procedure is that tearing modulus calculations are not required by the user, and a solution for the slope of the applied J/T line is provided. Results for the allowable minimum upper shelf toughness are presented for a range of reactor pressure vessel thickness and heatup/cooldown rates.

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.

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.

Allowable minimum upper shelf toughness for nuclear reactor pressure vessels

International Nuclear Information System (INIS)

Zahoor, A.

1988-01-01

The paper develops methodology and procedure for determining the allowable minimum upper shelf toughness for continued safe operation of nuclear reactor pressure vessels. Elastic-plastic fracture mechanics analysis method based on the J-integral tearing modulus (J/T) approach is used. Closed from expressions for the applied J and tearing modulus are presented for finite length, part-throughwall axial flaw with aspect ratio of 1/6. Solutions are then presented for Section III, Appendix G flaw. A simple flaw evaluation procedure that can be applied quickly by utility engineers is presented. An attractive feature of the simple procedure is that tearing modulus calculations are not required by the user, and a solution for the slope of the applied J/T line is provided. Results for the allowable minimum upper shelf toughness are presented for a range of reactor pressure vessel thickness and heatup/cooldown rates. (orig.)

A new tensile impact test for the toughness characterization of sheet material

Science.gov (United States)

Könemann, Markus; Lenz, David; Brinnel, Victoria; Münstermann, Sebastian

2018-05-01

In the past, the selection of suitable steels has been carried out primarily based on the mechanical properties of different steels. One of these properties is the resistance against crack propagation. For many constructions, this value plays an important role, because it can compare the impact toughness of different steel grades easily and gives information about the loading capacity of the specific materials. For thin sheets, impact toughness properties were usually not considered. One of the reasons for this is that the Charpy-impact test is not applicable for sheets with thicknesses below 2 mm. For a long time, this was not relevant because conventional steels had a sufficient impact toughness in a wide temperature range. However, since new multiphase steel grades with improved mechanical property exploitations are available, it turned out that impact toughness properties need to be considered during the component design phase, as the activation of the cleavage fracture mechanism is observed under challenging loading conditions. Therefore, this work aims to provide a new and practical testing procedure for sheet material or thin walled structures. The new testing procedure is based on tensile tests conducted in an impact pendulum similar to the Charpy impact hammer. A new standard geometry is provided, which enables a comparison between different steels or steel grades. A connection to the conventional Charpy test is presented using a damage mechanics model, which predicts material failure with consideration of to the stress state at various temperatures. Different specimen geometries are analysed to cover manifold stress states. A special advantage of the damage mechanics model is also the possibility to predict the materials behaviour in the transition area. To verify the method a conventional steel was tested in Charpy tests as well as in the new tensile impact test.

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-04-15

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

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

A study on the fracture toughness of heavy section steel plates and forgings for nuclear pressure vessels produced in Japan, (4)

International Nuclear Information System (INIS)

Sakai, Yuzuru; Ogura, Nobukazu; Takahashi, Isao; Miya, Kenzo; Ando, Yoshio.

1985-01-01

As another parameter for evaluating the toughness of structural materials, there is crack arrest toughness. This is a parameter showing the resistance of materials to stop the cracks rapidly propagating in brittle state within the materials, unlike static and dynamic fracture toughness related to the occurrence of breaking. As the conventional method of determining the crack arrest toughness, the relatively large testing method such as double tensile test and ESSO test have been known, but the establishment of a smaller convenient testing method is desired. In this study, the evaluation of the crack arrest toughness of the very thick steel materials produced in Japan was carried out by the testing method using small test pieces. In order to make test pieces small, tapered type DCB test and the three-point bending test using DWTT test pieces were examined as well as the testing method recommended by ASTM. The test materials were A 533B, Cl. 1 and A 508, Cl. 3. The test pieces, the various testing methods and the experimental results are reported. The temperature dependence of the crack arrest toughness was shown. (Kako, I.)

A study on the fracture toughness of heavy section steel plates and forgings for nuclear pressure vessels produced in Japan, 2

International Nuclear Information System (INIS)

Sakai, Yuzuru; Ogura, Nobukazu; Takahashi, Isao; Miya, Kenzo; Ando, Yoshio.

1984-01-01

In this paper, the main results of a series of tests carried out by the Atomic Energy Research Committee, the Japan Welding Engineering Society, for six years for the purpose of evaluating the fracture toughness and strength of superthick steel materials for nuclear reactors made in Japan are reported. In this research, as the fracture toughness test, three kinds of static, dynamic and crack propagation stop tests were carried out. Not only parent metals but also welded parts were evaluated, and numerous data have been accumulated. The fracture toughness of structural materials generally depends on test temperature, and forms three regions of lower shelf, transition and upper shelf from low temperature side toward high temperature side. It is desired to establish the effective method to determine fracture toughness over wide temperature range with small test pieces, and as its promising method, J(IC) fracture toughness test based on elasto-plastic fracture mechanics is carried out. The toughness in lower shelf and transition regions was clarified by K(IC) test, and that in upper shelf region was evaluated by J(IC) test. The methods of test and analysis, and the results are reported. (Kako, I.)

Quantification of the toughness distribution in a heavy section submerged arc multilayer reactor pressure vessel weldment

International Nuclear Information System (INIS)

Cerjak, H.; Prader, R.

1999-01-01

In a working procedure qualification test weld representing a heavy section circumferential reactor pressure vessel (RPV) weld tested in 1968, lower toughness values were observed in the top layer region compared to those found in the filler region. Gleeble simulation, extensive microscopic evaluation, diligent Charpy V-notch testing and modelling of the bead sequence and distribution of alloying elements was applied to explain this effect. It could be revealed that the microstructure of the weld metal is the most important factor influencing the toughness. When an 'as welded' microstructure is partly or fully reaustenitised by the adjacent multilayer beads, the microstructure transforms and the toughness increases. In the filler region, 85% of the cross-section consists from transformed microstructure, whereas in the top layer only 20% are transformed. It is quite evident that, accidentally, the notch tip of Charpy samples in 1968 were placed in untransformed microstructures. When the top layer on the inner surface of the RPV is weld cladded by austenitic stainless steel, full transformation occurs and the toughness representing the filler region can be taken into account for safety evaluations. (orig.)

On the enhancement of bond toughness for Al/epoxy T-peel joints with laser treated substrates

KAUST Repository

Alfano, Marco

2011-10-01

The aim of the present work is to quantify the enhancement of bond toughness of Al/epoxy joints associated to substrates laser irradiation. For this reason a potential based cohesive model is employed and cohesive elements are implemented within the finite element framework. The influence of the cohesive properties on the predicted global response of the joints is firstly analyzed. The coupling between adherents plasticity and the cohesive properties is then discussed. It is shown that the global response is mainly affected by cohesive energy (the bond toughness) and cohesive strength. In turn, a proper cost function is defined which quantifies the deviation between numerical and experimental total dissipated energy. Based on a sensitivity analysis of the as-defined cost function, it is shown that an accurate estimation of the bond toughness can be expected from global data. The situation is different for the cohesive strength, whose estimation could require more advanced experimental observations or additional tests. The results reported in the present work allow us to conclude, in a reliable manner, that the laser surface treatment can lead to a large improvement of bond toughness. © 2011 Springer Science+Business Media B.V.

Fracture toughness of A533B. Part 2. Review of data pertinent to upper shelf temperatures

International Nuclear Information System (INIS)

Druce, S.G.; Eyre, B.L.; Belcher, W.P.A.

1978-08-01

This report is the second in a series of three examining the state of the art of elastoplastic fracture mechanics as applied to A533B pressure vessel steel in the upper shelf temperature regime. Part II presents a review of fracture toughness data for A533B Class 1 plate tested in the longitudinal (RW) orientation. Data from USA, UK and Scandinavian sources published prior to September 1976 has been included. It is concluded that previous studies using a maximum load criterion have over-estimated the initiation toughness in the upper shelf regime. Results derived from J integral tests now show the mean toughness at 275 0 C to vary between 141 ksi sq. root in and 154 ksi sq. root in depending on the exact analytical procedure used. Limited statistical analysis of the results obtained using several heats of material suggest that standard deviation of the scatter of results is approximately 11% of the mean value. Recommendations for future work to improve our understanding of the fracture properties of A533B and similar medium strength high toughness materials, and their application to large structures, are presented. (author)

Fracture toughness of a nanoscale WC-Co tool steel

International Nuclear Information System (INIS)

Densley, J.M.; Hirth, J.P.

1997-01-01

Tungsten carbide tool steels, comprising WC particles with 6.7--25wt% Co distributed in the interparticle regions as a quasi-continuous binder phase, can be considered as WC-Co composites. The fracture toughness of such WC-Co composites is dependent on the volume fraction, contiguity and thickness of the cobalt binder, and the size of the tungsten carbide grains. Research has shown that the ductile binder undergoes nearly all the plastic deformation during fracture, which provides the primary energy consuming process that enhances fracture resistance. Recent manufacturing developments have given rise to the production of a WC-6.7wt% Co cermet having an average WC grain size of 70 nm, with a corresponding binder mean thickness, h, of 9 nm calculated from d = h(1-V f )/V f where d = 70 nm and V f = 0.114. This composite has shown a higher wear resistance than that of conventional cermets in proportion to their hardness. Such improvement has been attributed to the difficulty in forming dislocations in the very small grains. There are also indications that the Co binder in the nanoscale cermet contains higher contents of dissolved W and C than for conventional scale cermets. Because plastic deformation is initially confined to the binder phase, it was of interest to perform mode 1 and mixed mode toughness tests on the nanoscale cermet to determine whether flow localization influenced mixed mode toughness as in bulk materials. Two generations of this cermet were provided by Rogers Tool Works. The first generation, A, had lower binder contiguity, with occasional agglomerations of WC grains. The second generation, B, was cleaner, with the cobalt binder more uniformly separating the WC grains

A Novel Procedure for Prediction of Mixed Mode I/II in Fracture Toughness of Laminate Composites

Directory of Open Access Journals (Sweden)

M. Mahmood Shokrieh

2014-06-01

Full Text Available Delamination is one of the important modes of failure in laminated composite materials. In this respect, the mixed mode I/II fracture is the most major mode of delamination incidence in laminated composite. In the present research, a relation between the fracture toughness of double cantilever beam (DCB and asymmetric double cantilever beam (ADCB specimens is presented. The DCB and ADCB samples are used for measuring the mode I and mixed mode I/II fracture toughness (G of laminated composite materials, respectively. By considering the diversity of the stacking sequence of lay-ups, the test performance on all different types of lay-ups in order to measure the fracture toughness of laminated composites is a tedious, costly and time consuming task. The purpose of deriving this relation is to estimate the value of the strain energy release rate of laminated composite ADCB specimens by testing a unidirectional DCB. To develop this relationship, the geometry of DCB and ADCB specimens are considered to obtain fracture toughness of multi-directional laminate composites of ADCB samples with arbitrary ply sequence which may be used for design purposes. The procedure presented here reduces the calculation costs of the finite element modeling and its corresponding test significantly. The results obtained by this method are compared with those of experimental and numerical methods. It is shown that the fracture toughness of multi-directional lay-ups can be predicted by measuring the unidirectional ply with an error less than 10% demonstrating the accuracy of the procedure developed in the present research.

Effects of Eutectic Si Particles on Mechanical Properties and Fracture Toughness of Cast A356 Aluminum Alloys

International Nuclear Information System (INIS)

Lee, Kyu Hong; Lee, Sung Hak; Kwon, Yong Nam

2007-01-01

The present study aims at investigating the effects of eutectic Si particles on mechanical properties and fracture toughness of three A356 aluminum alloys. These A356 alloys were fabricated by casting processes such as rheo-casting, squeeze-casting, and casting-forging, and their mechanical properties and fracture toughness were analyzed in relation with microfracture mechanism study. All the cast A356 alloys contained eutectic Si particles mainly segregated along solidification cells, and the distribution of Si particles was modified by squeeze-casting and casting-forging processes. Microfracture observation results showed that eutectic Si particles segregated along cells were cracked first, but that aluminum matrix played a role in blocking crack propagation. Tensile properties and fracture toughness of the squeeze cast and cast-forged alloys having homogeneous distribution of eutectic Si particles were superior to those of the rheo-cast alloy. In particular, the cast-forged alloy had excellent hardness, strength, ductility, and fracture toughness because of the matrix strengthening and homogeneous distribution of eutectic Si particles due to forging process

Fracture toughness of glasses and hydroxyapatite: a comparative study of 7 methods by using Vickers indenter

OpenAIRE

HERVAS , Isabel; MONTAGNE , Alex; Van Gorp , Adrien; BENTOUMI , M.; THUAULT , A.; IOST , Alain

2016-01-01

International audience; Numerous methods have been proposed to estimate the indentation fracture toughness Kic for brittle materials. These methods generally uses formulæ established from empirical correlations between critical applied force, or average crack length, and classical fracture mechanics tests. This study compares several models of fracture toughness calculation obtained by using Vickers indenters. Two optical glasses (Crown and Flint), one vitroceramic (Zerodur) and one ceramic (...

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

Science.gov (United States)

Okada, Nagaya; Takeuchi, Shinichi

2017-07-01

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

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

International Nuclear Information System (INIS)

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

2013-12-01

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

Influence of preliminary loading on fracture toughness of ceramics ZrO2-(3,4) mol.% Y2O3

International Nuclear Information System (INIS)

Akimov, G.Ya.; Timchenko, V.M.

2001-01-01

The effect of preliminary mechanical loading on the fracture toughness of ceramics of the ZrO 2 -3-4 mol.% Y 2 O 3 composition is studied. It is shown that the fracture toughness monotonously increases and the increment constitutes ∼ 50% from the initial value. It is supposed that by the preliminary loading there takes place slow isothermal stage of the martensitic phase transformation of the part of the material grains. This leads to increase in the transformation degree by mechanical testing which is expressed in the increase in the fracture toughness [ru

Basic fracture toughness requirements for ferritic materials of nuclear class pressure retaining equipment in NPP

International Nuclear Information System (INIS)

Ning Dong; Yao Weida

2005-01-01

In this paper, theory basis on cold brittleness and anti-brittle fracture design of ferritic materials are introduced summarily and fracture toughness requirements for ferritic materials in ASME code for nuclear safety class pressure retaining equipment in NPP are summarized and evaluated. The results show that notch impact toughness requirements for materials relate to nuclear safety class of materials so as to ensure that brittle fracture of retaining pressure boundary in NPP can not occur. (authors)

Fracture toughness of titanium–cement interfaces: effects of fibers and loading angles

Directory of Open Access Journals (Sweden)

Khandaker M

2014-04-01

Full Text Available Morshed Khandaker,1 Khatri Chhetri Utsaha,1 Tracy Morris21Department of Engineering and Physics, 2Department of Mathematics and Statistics, University of Central Oklahoma, Edmond, OK, USAAbstract: Ideal implant–cement or implant–bone interfaces are required for implant fixation and the filling of tissue defects created by disease. Micron- to nanosize osseointegrated features, such as surface roughness, fibers, porosity, and particles, have been fused with implants for improving the osseointegration of an implant with the host tissue in orthopedics and dentistry. The effects of fibers and loading angles on the interface fracture toughness of implant–cement specimens with and without fibers at the interface are not yet known. Such studies are important for the design of a long-lasting implant for orthopedic applications. The goal of this study was to improve the fracture toughness of an implant–cement interface by deposition of micron- to nanosize fibers on an implant surface. There were two objectives in the study: 1 to evaluate the influence of fibers on the fracture toughness of implant–cement interfaces with and without fibers at the interfaces, and 2 to evaluate the influence of loading angles on implant–cement interfaces with and without fibers at the interfaces. This study used titanium as the implant, poly(methyl methacrylate (PMMA as cement, and polycaprolactone (PCL as fiber materials. An electrospinning unit was fabricated for the deposition of PCL unidirectional fibers on titanium (Ti plates. The Evex tensile test stage was used to determine the interface fracture toughness (KC of Ti–PMMA with and without PCL fibers at 0°, 45°, and 90° loading angles, referred to in this article as tension, mixed, and shear tests. The study did not find any significant interaction between fiber and loading angles (P>0.05, although there was a significant difference in the KC means of Ti–PMMA samples for the loading angles (P<0

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.

Application of Master Curve fracture toughness for reactor pressure vessel integrity assessment in the USA

International Nuclear Information System (INIS)

Server, William; Rosinski, Stan; Lott, Randy; Kim, Charles; Weakland, Dennis

2002-01-01

The Master Curve fracture toughness approach has been used in the USA for better defining the transition temperature fracture toughness of irradiated reactor pressure vessel (RPV) steels for end-of-life (EOL) and EOL extension (EOLE) time periods. The first application was for the Kewaunee plant in which the life-limiting material was a circumferential weld metal. Fracture toughness testing of this weld metal corresponding to EOL and beyond EOLE was used to reassess the PTS screening value, RT PTS , and to develop new operating pressure-temperature curves. The NRC has approved this application using a shift-based methodology and higher safety margins than those proposed by the utility and its contractors. Beaver Valley Unit 1, a First Energy nuclear plant, has performed similar fracture toughness testing, but none of the testing has been conducted at EOL or EOLE at this time. Therefore, extrapolation of the life-limiting plate data to higher fluences is necessary, and the projections will be checked in the next decade by Master Curve fracture toughness testing of all of the Beaver Valley Unit 1 beltline materials (three plates and three welds) at fluences near or greater than EOLE. A supplemental surveillance capsule has been installed in the sister plant, Beaver Valley Unit 2, which has the capability of achieving a higher lead factor while operating under essentially the same environment. The Beaver Valley Unit 1 evaluation has been submitted to the NRC. This paper reviews the shift-based approach taken for the Beaver Valley Unit 1 RPV and presents the use of the RT T 0 methodology (which evolved out of the Master Curve testing and endorsed through two ASME Code Cases). The applied margin accounts for uncertainties in the various material parameters. Discussion of a direct measurement of RT T 0 approach, as originally submitted for the Kewaunee case, is also presented

Master curve approach to monitor fracture toughness of reactor pressure vessels in nuclear power plants

International Nuclear Information System (INIS)

2009-10-01

A series of coordinated research projects (CRPs) have been sponsored by the IAEA, starting in the early 1970s, focused on neutron radiation effects on reactor pressure vessel (RPV) steels. The purpose of the CRPs was to develop correlative comparisons to test the uniformity of results through coordinated international research studies and data sharing. The overall scope of the eighth CRP (CRP-8), Master Curve Approach to Monitor Fracture Toughness of Reactor Pressure Vessels in Nuclear Power Plants, has evolved from previous CRPs which have focused on fracture toughness related issues. The ultimate use of embrittlement understanding is application to assure structural integrity of the RPV under current and future operation and accident conditions. The Master Curve approach for assessing the fracture toughness of a sampled irradiated material has been gaining acceptance throughout the world. This direct measurement of fracture toughness approach is technically superior to the correlative and indirect methods used in the past to assess irradiated RPV integrity. Several elements have been identified as focal points for Master Curve use: (i) limits of applicability for the Master Curve at the upper range of the transition region for loading quasi-static to dynamic/impact loading rates; (ii) effects of non-homogeneous material or changes due to environment conditions on the Master Curve, and how heterogeneity can be integrated into a more inclusive Master Curve methodology; (iii) importance of fracture mode differences and changes affect the Master Curve shape. The collected data in this report represent mostly results from non-irradiated testing, although some results from test reactor irradiations and plant surveillance programmes have been included as available. The results presented here should allow utility engineers and scientists to directly measure fracture toughness using small surveillance size specimens and apply the results using the Master Curve approach

Transition Fracture Toughness Characterization of Eurofer 97 Steel using Pre-Cracked Miniature Multi-notch Bend Bar Specimens

Energy Technology Data Exchange (ETDEWEB)

Chen, Xiang [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Sokolov, Mikhail A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Linton, Kory D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Clowers, Logan N. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Katoh, Yutai [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2017-11-01

In this report, we present the feasibility study of using pre-cracked miniature multi-notch bend bar specimens (M4CVN) with a dimension of 45mm (length) x 3.3mm (width) x 1.65mm (thickness) to characterize the transition fracture toughness of Eurofer97 based on the ASTM E1921 Master Curve method. From literature survey results, we did not find any obvious specimen size effects on the measured fracture toughness of unirradiated Eurofer97. Nonetheless, in order to exclude the specimen size effect on the measured fracture toughness of neutron irradiated Eurofer97, comparison of results obtained from larger size specimens with those from smaller size specimens after neutron irradiation is necessary, which is not practical and can be formidably expensive. However, limited literature results indicate that the transition fracture toughness of Eurofer97 obtained from different specimen sizes and geometries followed the similar irradiation embrittlement trend. We then described the newly designed experimental setup to be used for testing neutron irradiated Eurofer97 pre-cracked M4CVN bend bars in the hot cell. We recently used the same setup for testing neutron irradiated F82H pre-cracked miniature multi-notch bend bars with great success. Considering the similarity in materials, specimen types, and the nature of tests between Eurofer97 and F82H, we believe the newly designed experimental setup can be used successfully in fracture toughness testing of Eurofer97 pre-cracked M4CVN specimens.

Fracture Toughness and Strength in a New Class of Bainitic Chromium-Tungsten Steels

Energy Technology Data Exchange (ETDEWEB)

Mao, S. X.; Sikka, V. K.

2006-06-01

This project dealt with developing an understanding of the toughening and stengthening mechanisms for a new class of Fe-3Cr-W(V) steels developed at Oak Ridge National Laboratory (ORNL) in collaboration with Nooter Corporation and other industrial partners. The new steele had 50% higher tensile strength up to 650 degrees Celsius than currently used steels and the potential for not requiring any postweld heat treatment (PWHT) and for reducing equipment weight by 25%. This project was closely related to the Nooter project described in the report Development of a New Class of Fe-3Cr-W(V) Ferritic steels for Industrial Process Applications (ORNL/TM-2005/82). The project was carried out jointly by the University of Pittsburgh and ORNL. The University of Pittsburgh carried out fracture toughness measurements and microstructural analysis on base metal and welded plates prepared at ORNL. The project focused on three areas. The first dealt with detailed microstructural analysis of base compositions of 3Cr-3WV and 3Cr-3WBV(Ta) in both normalized (N) and normalized and tempered (NT) conditions. The second aspect of the prject dealt with determining tensile properties and fracture toughness values of K{subIC} at room temperature for both 3Cr-3Wv and 3Cr-3WV(Ta) compositions. The third focus of the project was to measure the fracture toughness values of the base metal and the heat-affectged zone (HAZ) of a plate of Fe-3Cr-W(Mo)V steel plate welded by the gas tungsten are (GTA) process. The HAZ toughness was measured in both the as-welded and the PWHT condition.

Renewable Pentablock Copolymers Containing Bulky Natural Rosin for Tough Bioplastics

Science.gov (United States)

Rahman, Md Anisur; Ganewatta, Mitra S.; Lokupitiya, Hasala N.; Liang, Yuan; Stefik, Morgan; Tang, Chuanbing

Renewable polymers have received significant attention due to environmental concerns on petrochemical counterparts. One of the most abundant natural biomass is resin acids. However, most polymers derived from resin acids are low molecular weight and brittle because of the high chain entanglement molecular weight resulted from the bulky hydrophenanthrene pendant group. It is well established that the brittleness can be overcome by synthesizing multi-block copolymers with low entanglement molecular weight components. We investigated the effects of chain architecture and microdomain orientation on mechanical properties of both tri and pentablock copolymers. We synthesized rosin-containing A-B-A-B-A type pentablock and A-B-A type triblock copolymers to improve their mechanical properties. Pentablock copolymers showed higher strength and better toughness as compared to triblock copolymers, both superior to homopolymers. The greater toughness of pentablock copolymers is due to the presence of the rosin based midblock chains that act as bridging chains between two polynorbornene blocks.

Macroscale and microscale fracture toughness of microporous sintered Ag for applications in power electronic devices

International Nuclear Information System (INIS)

Chen, Chuantong; Nagao, Shijo; Suganuma, Katsuaki; Jiu, Jinting; Sugahara, Tohru; Zhang, Hao; Iwashige, Tomohito; Sugiura, Kazuhiko; Tsuruta, Kazuhiro

2017-01-01

The application of microporous sintered silver (Ag) as a bonding material to replace conventional die-bonding materials in power electronic devices has attracted considerable interest. Characterization of the mechanical properties of microporous Ag will enable its use in applications such as lead-free solder electronics and provide a fundamental understanding of its design principles. However, the material typically suffers from thermal and mechanical stress during its production fabrication, and service. In this work, we have studied the effect of microporous Ag specimen size on fracture toughness from the microscale to the macroscale. A focused ion beam was used to fabricate 20-, 10- and 5-μm-wide microscale specimens, which were of the same order of magnitude as the pore networks in the microporous Ag. Micro-cantilever bending tests revealed that fracture toughness decreased as the specimen size decreased. Conventional middle-cracked tensile tests were performed to determine the fracture toughness of the macroscale specimens. The microscale and macroscale fracture toughness results showed a clear size effect, which is discussed in terms of both the deformation behavior of crack tip and the influence of pore networks within Ag with different specimen sizes. Finite element model simulations showed that stress at the crack tip increased as the specimen size increased, which led to larger plastic deformation and more energy being consumed when the specimen fractured.

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

Science.gov (United States)

Gates, Thomas S.; Herring, Helen M.

2001-01-01

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

Adaptation of TOUGH2 to the transport of supercritical CO2. Final report

International Nuclear Information System (INIS)

Audigane, P.

2004-12-01

This work has been realized in the framework of the PICOR national research program which aims to study the massive injection of CO 2 in reservoirs (aquifers). It is considered as a mean for reducing atmospheric emissions of greenhouse effect gases. Numerical modeling is an important tool for studying these injections. Some modifications have been realized in the EWASG module to adapt the software TOUGH2 for the case of the supercritical CO 2 storage in saline aquifers. In order to validate the modifications, comparative evaluations are presented. The report presents the TOUGH2 software, more specially the EWASG module, the comparative evaluations and discusses the satisfying results. (A.L.B.)

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

OpenAIRE

Cooper, Adam J.; Sherry, Andrew

2018-01-01

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

Simulation of the Heber geothermal field, a TOUGH2/PC application

Energy Technology Data Exchange (ETDEWEB)

Antunez, E.; Lippmann, M. [Lawrence Berkeley Laboratory, Berkeley, CA (United States); Ali Khan, M. [California Department of Conservation, Santa Rosa, CA (United States)

1995-03-01

A numerical simulation model for the Heber geothermal field in southern California is being developed under a technology transfer agreement between the Department of Energy/LBL and the California Department of Conservation, Division of Oil, Gas, and Geothermal Resources (Division). The two objectives of the cooperation are: (1) to train Division personnel in the use of the TOUGH2/PC computer code; and (2) to develop a module compatible with TOUGH2 to investigate the effects of production/injection operations on the ground surface subsidence-rebound phenomenon observed in the field. The compaction of the rock formation will be handled assuming an elastic behavior of the rock-fluid system. Considered will be changes in pore volume and in-grid block dimensions, as well as, the process by which the change in formation volume is transmitted to the surface (vertical deformation; subsidence and rebound).

EOSN: A TOUGH2 module for noble gases

Energy Technology Data Exchange (ETDEWEB)

Shan, Chao; Pruess, Karsten

2003-03-07

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.

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

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.

Dynamic fracture mechanics with electromagnetic force and its application to fracture toughness and testing

International Nuclear Information System (INIS)

Yagawa, G.; Yoshimura, S.

1986-01-01

This study is concerned with the application of the electromagnetic force to the determination of the dynamic fracture toughness of materials. Taken is an edge-cracked specimen which carries a transient electric current I and is simply supported in a uniform and steady magnetic field B. As a result of their interaction, the dynamic electromagnetic force occurs in the whole body of the specimen, which is then deformed to fracture in the opening mode of cracking. For the evaluation of dynamic fracture toughness, the extended J integral with the effects of the electromagnetic force and inertia is calculated using the dynamic finite-element method. To determine the dynamic crack-initiation point in the experiment, the electric potential method is used in the case of brittle fracture, and the electric potential and the J-R curve methods in the case of ductile fracture, respectively. Using these techniques, the dynamic fracture toughness values of nuclear pressure vessel steel A508 class 3 are evaluated over a wide temperature range. (author)

Relationship between toughness and the physical fracture process on a microscopic scale

International Nuclear Information System (INIS)

Francois, D.

1975-01-01

Cleavage occurs when a local stress reaches a critical level sigma-f which is a function of temperature and metallurgical factors such as grain size. Cleavages occur ahead of the main crack tip. It is possible to establish a relationship between the cleavage stress and toughness, involving the notch root radius. At higher temperatures, fracture is ductile and occurs at a critical elongation epsilon-f, which is a function of the distribution of inclusions and the strain hardening index. It is possible to establish a relationship between toughness and this elongation at rupture. The influence of temperature, which affects several parameters, is complex. On the other hand, pressure, modifying only elongation at rupture represents an attractive means for confirming this theories. Experimental results are presented [fr

A graphical interface to the TOUGH family of flow simulators

Energy Technology Data Exchange (ETDEWEB)

O`Sullivan, M.J.; Bullivant, D.P. [Univ. of Auckland (New Zealand)

1995-03-01

A graphical interface for the TOUGH family of simulators is presented. The interface allows the user to graphically create or modify a computer model and then to graphically examine the simulation results. The package uses the X Window System, enabling it to be used on many computer platforms.

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

International Nuclear Information System (INIS)

Albuquerque, Victor Hugo C. de; Melo, Tadeu Antonio de A; Gomes, Rodinei M.; Lima, Severino Jackson G. de; Tavares, Joao Manuel R.S.

2010-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-02-15

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2010-11-25

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

Fracture toughness of epoxy/multi-walled carbon nanotube nano-composites under bending and shear loading conditions

International Nuclear Information System (INIS)

Ayatollahi, M.R.; Shadlou, S.; Shokrieh, M.M.

2011-01-01

Research highlights: → Mode I and mode II fracture tests were conducted on epoxy/MWCNT nano-composites. → Addition of MWCNT to epoxy increased both K Ic and K IIc of nano-composites. → The improvement in K IIc was more pronounced than in K Ic . → Mode I and mode II fracture surfaces were studied by scanning electron microscopy. -- Abstract: The effects of multi-walled carbon nanotubes (MWCNTs) on the mechanical properties of epoxy/MWCNT nano-composites were studied with emphasis on fracture toughness under bending and shear loading conditions. Several finite element (FE) analyses were performed to determine appropriate shear loading boundary conditions for a single-edge notch bend specimen (SENB) and an equation was derived for calculating the shear loading fracture toughness from the fracture load. It was seen that the increase in fracture toughness of nano-composite depends on the type of loading. That is to say, the presence of MWCNTs had a greater effect on fracture toughness of nano-composites under shear loading compared with normal loading. To study the fracture mechanisms, several scanning electron microscopy (SEM) pictures were taken from the fracture surfaces. A correlation was found between the characteristics of fracture surface and the mechanical behaviors observed in the fracture tests.

Fracture Toughness Improvement of Composites Reinforced with Optimally Shaped Short Ductile Fibers

National Research Council Canada - National Science Library

Wetherhold, Robert C; Patra, Abani K

2001-01-01

The fracture toughness of brittle matrix composites reinforced with ductile fibers has been greatly improved by shaping the fibers so that they fully contribute their plastic work to the fracture process...

Comparison of fracture toughness values from large-scale pipe system tests and C(T) specimens

International Nuclear Information System (INIS)

Olson, R.; Scott, P.; Marschall, C.; Wilkowski, G.

1993-01-01

Within the International Piping Integrity Research Group (IPIRG) program, pipe system experiments involving dynamic loading with intentionally circumferentially cracked pipe were conducted. The pipe system was fabricated from 406-mm (16-inch) diameter Schedule 100 pipe and the experiments were conducted at 15.5 MPa (2,250 psi) and 288 C (550 F). The loads consisted of pressure, dead-weight, thermal expansion, inertia, and dynamic anchor motion. Significant instrumentation was used to allow the material fracture resistance to be calculated from these large-scale experiments. A comparison of the toughness values from the stainless steel base metal pipe experiment of standard quasi-static and dynamic C(T) specimen tests showed the pipe toughness value was significantly lower than that obtained from C(T) specimens. It is hypothesized that the cyclic loading from inertial stresses in this pipe system experiment caused local degradation of the material toughness. Such effects are not considered in current LBB or pipe flaw evaluation criteria. 4 refs., 14 figs., 1 tab

Effect of Aging Treatment on Impact Toughness and Corrosion Resistance of Super Duplex Stainless Steel

Science.gov (United States)

Kim, Jae-Hwan; Oh, Eun-Ji; Lee, Byung-Chan; Kang, Chang-Yong

2016-01-01

The effect of aging time on impact toughness and corrosion resistance of 25%Cr-7%Ni-2%Mo-4%W-0.2%N super duplex stainless steel from the viewpoint of intermetallic secondary phase variation was investigated with scanning electron microscopic observation with energy-dispersive x-ray spectroscopic analysis and transmission electron microscopy. The results clarified that R-phase is precipitated not only at the interface of ferrite and austenite but inside the ferrite at an initial stage of aging and then transformed into σ-phase from an aging time of 1 h, while the ferrite phase decomposed into γ2 and σ-phase with increase of aging time. This variation of the phases led to decrease of its impact toughness, and specifically, the R-phase was proved to be predominant in the degradation of the impact toughness at the initial stage of the aging. Additionally, these secondary phases led to deterioration of corrosion resistance because of Cr depletion.

Fracture Anisotropy and Toughness in the Mancos Shale: Implications for crack-growth geometry

Science.gov (United States)

Chandler, M. R.; Meredith, P. G.; Brantut, N.; Crawford, B. R.

2013-12-01

The hydraulic fracturing of gas-shales has drawn attention to the fundamental fracture properties of shales. Fracture propagation is dependent on a combination of the in-situ stress field, the fracturing fluid and pressure, and the mechanical properties of the shale. However, shales are strongly anisotropic, and there is a general paucity of available experimental data on the anisotropic mechanical properties of shales in the scientific literature. The mode-I stress intensity factor, KI, quantifies the concentration of stress at crack tips. The Fracture Toughness of a linear elastic material is then defined as the critical value of this stress intensity factor; KIc, beyond which rapid catastrophic crack growth occurs. However, shales display significant non-linearity, which produces hysteresis during experimental cyclic loading. This allows for the calculation of a ductility coefficient using the residual displacement after successive loading cycles. From this coefficient, a ductility corrected Fracture Toughness value, KIcc can be determined. In the Mancos Shale this ductility correction can be as large as 60%, giving a Divider orientation KIcc value of 0.8 MPa.m0.5. Tensile strength and mode-I Fracture Toughness have been experimentally determined for the Mancos Shale using the Brazil Disk and Short-Rod methodologies respectively. The three principal fracture orientations; Arrester, Divider and Short-Transverse were all analysed. A significant anisotropy is observed in the tensile strength, with the Arrester value being 1.5 times higher than the Short-Transverse value. Even larger anisotropy is observed in the Fracture Toughness, with KIcc in the Divider and Arrester orientations being around 1.8 times that in the Short-Transverse orientation. For both tensile strength and fracture toughness, the Short-Transverse orientation, where the fracture propagates in the bedding plane in a direction parallel to the bedding, is found to have significantly lower values than

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

Energy Technology Data Exchange (ETDEWEB)

Yan, Guanghua; Han, Lizhan; Li, Chuanwei; Luo, Xiaomeng; Gu, Jianfeng, E-mail: gujf@sjtu.edu.cn

2017-01-15

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

Mode I type delamination fracture toughness of YBCO coated conductor with additional Cu layer

International Nuclear Information System (INIS)

Miyazato, T.; Hojo, M.; Sugano, M.; Adachi, T.; Inoue, Y.; Shikimachi, K.; Hirano, N.; Nagaya, S.

2011-01-01

A fracture toughness test method was developed for a YBCO coated conductor with an additional Cu layer. Mode I type tests were carried out using double cantilever beam (DCB) specimens. Delamination propagated into the YBCO layer, and sometimes reached the Ag/YBCO interface. The fracture toughness for YBCO was about 10 J/m 2 . That for Ag/YBCO interface was about 100 J/m 2 . Although interlaminar fracture at a YBa 2 Cu 3 O 7-δ (YBCO)/CeO 2 interface was reported for YBCO coated conductors, this has not yet been investigated by a fracture mechanical approach. In the present study, we developed a mode I type fracture toughness test method for a YBCO coated conductor with an additional Cu layer using double cantilever beam (DCB) specimens. Fracture mechanism was investigated by microscopic observation by a scanning electron microscope (SEM), together with composition analysis by an energy dispersive X-ray spectroscope (EDS). A pre-crack introduced at the YBCO/CeO 2 interface deviated from the interface, and propagated into the YBCO layer, and sometimes reached the Ag/YBCO interface. The fracture toughness, G R , for YBCO and the Ag/YBCO interface was evaluated to be 7-10 J/m 2 and 80-120 J/m 2 , respectively. The complex stress intensity factor ratio, K 2 /K 1 , at YBCO/CeO 2 interface was evaluated to be -0.19, and this ratio controlled the formation of microcracks in the YBCO layer. The main crack propagated into the YBCO layer accompanied with the formation of microcracks.

Fracture toughness properties of candidate canister materials for spent fuel storage by concrete cask

International Nuclear Information System (INIS)

Arai, Taku; Mayuzumi, Masami; Libin, Niu; Takaku, Hiroshi

2005-01-01

It is very significant to clarify the fracture toughness properties of candidate canister materials to ensure the structural integrity against the accidents during handling in the storage facility. Fracture toughness tests on the CT specimens cut from base metal, heat affected zone (HAZ) and weld metal in the 2 types of weld joints made by candidate canister materials (SUS329J4L duplex stainless steel and YUS270 super stainless steel) were conducted under various test temperature between 233K and 473K. Stable ductile crack extensions were observed in all of the specimens. The fracture toughness J Q of the base metal and the HAZ of SUS329L4L showed the smallest value at 233K, and increased with temperature, then reached to the largest value at 298K. At the higher temperature, the value of J Q decreased slightly with temperature. While, the value of J Q in the weld metal increased with temperature. The value of J Q of YUS270 increased with temperature. The values of J Q for weld metal in both of the materials were not greater than those in base metal and HAZ at each test temperature. The values of J Q in weld metal of both materials at 213K and 473K were greater than applied J derived from postulated semi-elliptical surface flaw and maximum allowable stress in JSME design coed. This result suggested that these materials have enough toughness for use as the canister material. (author)

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

INFLUENCE OF HEAT TREATMENT ON THE MICROSTRUCTURE AND TOUGHNESS OF BÖHLER M333 ISOPLAST STEEL

OpenAIRE

Perko, J.; Redl, C.; Leitner, H.

2009-01-01

In this work the through hardenability and the influence of the heat treatment parameters (austenitizingtemperature, cooling parameter ? and tempering temperature) on the microstructure and the achievabletoughness level of Böhler M333 ISOPLAST are investigated. The results are compared to the standardizedtool steel grade DIN 1.2083. The investigations showed that the cooling parameter ? has a strong influenceon the impact toughness of M333 ISOPLAST plastic mould steel. The toughness is reduce...

The role of powder preparation method in enhancing fracture toughness of zirconia ceramics with low alumina amount

International Nuclear Information System (INIS)

Danilenko, I.; Konstantinova, T.; Volkova, G.; Burkhovetski, V.; Glazunova, V.

2015-01-01

In most cases zirconia-alumina composites for scientific investigations and industry are prepared by means of mechanical mixing of powders, compaction and sintering. In our opinion, this is one of the reasons for the low values for fracture toughness of the sintered materials. In this study, we investigated the effect of nanopowder synthesis methods on the structure and mechanical properties of 3Y-TZP/alumina ceramic composites and determined the mechanisms involved in composite toughening. We show that the addition of a small amount of alumina (1 - 2 wt%) to zirconia ceramics has the potential to increase the fracture toughness of zirconia ceramics. The starting powders were obtained by means of co-precipitation and ball milling. It turned out that at equal density, bending strength and hardness values, the fracture toughness in ceramic composites sintered from co-precipitated nanopowders is higher in comparison with fracture toughness values in matrix material and traditional 3Y-TZP/alumina composites. We believed that the role of the crack deflection process in ceramic composites sintered from co-precipitated nanopowders increased significantly. This can be conditioned by means of a series of processes for composite structure formation during precipitation, crystallization, and sintering of nanopowders.

The role of powder preparation method in enhancing fracture toughness of zirconia ceramics with low alumina amount

Energy Technology Data Exchange (ETDEWEB)

Danilenko, I.; Konstantinova, T.; Volkova, G.; Burkhovetski, V.; Glazunova, V. [NAS of Ukraine, Donetsk (Ukraine). Donetsk Inst. for Physics and Engineering

2015-07-01

In most cases zirconia-alumina composites for scientific investigations and industry are prepared by means of mechanical mixing of powders, compaction and sintering. In our opinion, this is one of the reasons for the low values for fracture toughness of the sintered materials. In this study, we investigated the effect of nanopowder synthesis methods on the structure and mechanical properties of 3Y-TZP/alumina ceramic composites and determined the mechanisms involved in composite toughening. We show that the addition of a small amount of alumina (1 - 2 wt%) to zirconia ceramics has the potential to increase the fracture toughness of zirconia ceramics. The starting powders were obtained by means of co-precipitation and ball milling. It turned out that at equal density, bending strength and hardness values, the fracture toughness in ceramic composites sintered from co-precipitated nanopowders is higher in comparison with fracture toughness values in matrix material and traditional 3Y-TZP/alumina composites. We believed that the role of the crack deflection process in ceramic composites sintered from co-precipitated nanopowders increased significantly. This can be conditioned by means of a series of processes for composite structure formation during precipitation, crystallization, and sintering of nanopowders.

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

Science.gov (United States)

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

2018-03-01

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

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

International Nuclear Information System (INIS)

Almuhammadi, Khaled; Alfano, Marco; Yang, Yang; Lubineau, Gilles

2014-01-01

Highlights: • CNTs are solvent sprayed on CFRP prepreg to improve interlaminar fracture toughness. • Raman mapping revealed the actual penetration of CNTs across the interface. • A finite thickness nanoreinforced region was able to spread damage through CNT pull-out and peeling. • The induced dissipation mechanisms are operative at the microscale. • The nanoreinforcement strategy led to an increased fracture toughness. - Abstract: The present work is focused on the nanoreinforcement of prepreg based carbon fiber composite laminates to improve delamination resistance. Functionalized multi-walled carbon nanotubes (MWCNTs) were dispersed over the interface between prepreg layers through solvent spraying and the resulting mode I interlaminar fracture toughness was determined. For comparison, baseline samples with neat prepregs were also prepared. Results indicate that the introduction of functionalized MWCNTs can favorably affect the interlaminar fracture toughness, and the associated mechanisms of failure have been investigated. The manufacturing procedures and the interfacial reinforcing mechanism were explored by analyzing (i) the wettability between CNTs-solvent solution and prepreg surface, (ii) CNTs dispersion and (iii) the fractured surfaces through high resolution scanning electron microscopy and Raman mapping

Cross-Cultural Invariance of the Mental Toughness Inventory Among Australian, Chinese, and Malaysian Athletes: A Bayesian Estimation Approach.

Science.gov (United States)

Gucciardi, Daniel F; Zhang, Chun-Qing; Ponnusamy, Vellapandian; Si, Gangyan; Stenling, Andreas

2016-04-01

The aims of this study were to assess the cross-cultural invariance of athletes' self-reports of mental toughness and to introduce and illustrate the application of approximate measurement invariance using Bayesian estimation for sport and exercise psychology scholars. Athletes from Australia (n = 353, Mage = 19.13, SD = 3.27, men = 161), China (n = 254, Mage = 17.82, SD = 2.28, men = 138), and Malaysia (n = 341, Mage = 19.13, SD = 3.27, men = 200) provided a cross-sectional snapshot of their mental toughness. The cross-cultural invariance of the mental toughness inventory in terms of (a) the factor structure (configural invariance), (b) factor loadings (metric invariance), and (c) item intercepts (scalar invariance) was tested using an approximate measurement framework with Bayesian estimation. Results indicated that approximate metric and scalar invariance was established. From a methodological standpoint, this study demonstrated the usefulness and flexibility of Bayesian estimation for single-sample and multigroup analyses of measurement instruments. Substantively, the current findings suggest that the measurement of mental toughness requires cultural adjustments to better capture the contextually salient (emic) aspects of this concept.

Effect of microstructure evolution of the lamellar alpha on impact toughness in a two-phase titanium alloy

International Nuclear Information System (INIS)

Xu, Jianwei; Zeng, Weidong; Zhao, Yawei; Jia, Zhiqiang

2016-01-01

The effects of the evolution of the lamellar alpha microstructure on the impact toughness of Ti-17 alloy are investigated. For this purpose, the beta-processed material is isothermally forged at 820 °C and subsequently heat treated using the combination of solid solution and aging treatment. Then the impact tests are carried out at room temperature. The corresponding microstructure and fracture surface are examined by scanning electron microscope (SEM). Microstructural observations reveal that globularization behavior is the main feature of microstructure evolution and the globularization fraction increases with the increasing of prestrain. However, globularization behavior has a negative influence on the impact toughness of Ti-17 alloy. In this work, the impact toughness have been obtained in the range of 29–55 J/cm 2 via varying globularization fraction of alpha phase. A linear relationship between the impact toughness and globularization fraction can be observed though the quantitative analysis. The linear equation is expressed as A=−0.3232f+59.885. The two major reasons can be used to explain the effect of globularization fraction on the impact property of Ti-17 alloy. One explanation is that the lamellar structure can provide excellent interfacial strengthening effect, which can improve the toughness of material, and makes it not easy to fracture. On the other hand, the fracture surface of specimen with the lamellar structure has larger amplitude of ups and downs. A long crack path length will be generated during fracture process. By contrast, the fracture of specimen with the equiaxed structure presents more flat surface and shorter crack path.

Prediction of the brittle fracture toughness value of a RPV steel from the analysis of a limited set of Charpy results

International Nuclear Information System (INIS)

Forget, P.; Marini, B.; Verdiere, N.

2001-01-01

Our objective is to establish a method to be able to determine fracture toughness of a reactor pressure vessel (RPV) by using the small number of Charpy specimens used in the reactor surveillance program. Previous studies have shown that it is possible to determine fracture toughness from Charpy tests. Another point is to determine if statistical effects are compatible with a restricted number of specimens, this paper deals with this point and presents a methodology that is applicable to the case of irradiated materials from the surveillance program. Several conclusions can be drawn from this study: -) When determining failure parameters, we gain most accuracy by increasing the number of samples from 3 to about 6; -) it is possible to evaluate brittle fracture toughness using local approach, either by using Beremin or Renevey model; -) The effect of using a small number of Charpy specimens to determine fracture toughness in brittle fracture is evaluated. The error in the evaluation of fracture toughness is much smaller than the experimental dispersion itself. (A.C.)

Development of a Weibull model of cleavage fracture toughness for shallow flaws in reactor pressure vessel material

Energy Technology Data Exchange (ETDEWEB)

Bass, B.R.; Williams, P.T.; McAfee, W.J.; Pugh, C.E. [Oak Ridge National Lab., Heavy-Section Steel Technology Program, Oak Ridge, TN (United States)

2001-07-01

A primary objective of the United States Nuclear Regulatory Commission (USNRC) -sponsored Heavy-Section Steel Technology (HSST) Program is to develop and validate technology applicable to quantitative assessments of fracture prevention margins in nuclear reactor pressure vessels (RPVs) containing flaws and subjected to service-induced material toughness degradation. This paper describes an experimental/analytical program for the development of a Weibull statistical model of cleavage fracture toughness for applications to shallow surface-breaking and embedded flaws in RPV materials subjected to multi-axial loading conditions. The experimental part includes both material characterization testing and larger fracture toughness experiments conducted using a special-purpose cruciform beam specimen developed by Oak Ridge National Laboratory for applying biaxial loads to shallow cracks. Test materials (pressure vessel steels) included plate product forms (conforming to ASTM A533 Grade B Class 1 specifications) and shell segments procured from a pressurized-water reactor vessel intended for a nuclear power plant. Results from tests performed on cruciform specimens demonstrated that biaxial loading can have a pronounced effect on shallow-flaw fracture toughness in the lower-transition temperature region. A local approach methodology based on a three-parameter Weibull model was developed to correlate these experimentally-observed biaxial effects on fracture toughness. The Weibull model, combined with a new hydrostatic stress criterion in place of the more commonly used maximum principal stress in the kernel of the Weibull stress integral definition, is shown to provide a scaling mechanism between uniaxial and biaxial loading states for 2-dimensional flaws located in the A533-B plate material. The Weibull stress density was introduced as a matrice for identifying regions along a semi-elliptical flaw front that have a higher probability of cleavage initiation. Cumulative

Development of a Weibull model of cleavage fracture toughness for shallow flaws in reactor pressure vessel material

International Nuclear Information System (INIS)

Bass, B.R.; Williams, P.T.; McAfee, W.J.; Pugh, C.E.

2001-01-01

A primary objective of the United States Nuclear Regulatory Commission (USNRC) -sponsored Heavy-Section Steel Technology (HSST) Program is to develop and validate technology applicable to quantitative assessments of fracture prevention margins in nuclear reactor pressure vessels (RPVs) containing flaws and subjected to service-induced material toughness degradation. This paper describes an experimental/analytical program for the development of a Weibull statistical model of cleavage fracture toughness for applications to shallow surface-breaking and embedded flaws in RPV materials subjected to multi-axial loading conditions. The experimental part includes both material characterization testing and larger fracture toughness experiments conducted using a special-purpose cruciform beam specimen developed by Oak Ridge National Laboratory for applying biaxial loads to shallow cracks. Test materials (pressure vessel steels) included plate product forms (conforming to ASTM A533 Grade B Class 1 specifications) and shell segments procured from a pressurized-water reactor vessel intended for a nuclear power plant. Results from tests performed on cruciform specimens demonstrated that biaxial loading can have a pronounced effect on shallow-flaw fracture toughness in the lower-transition temperature region. A local approach methodology based on a three-parameter Weibull model was developed to correlate these experimentally-observed biaxial effects on fracture toughness. The Weibull model, combined with a new hydrostatic stress criterion in place of the more commonly used maximum principal stress in the kernel of the Weibull stress integral definition, is shown to provide a scaling mechanism between uniaxial and biaxial loading states for 2-dimensional flaws located in the A533-B plate material. The Weibull stress density was introduced as a matrice for identifying regions along a semi-elliptical flaw front that have a higher probability of cleavage initiation. Cumulative

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.

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.

Toughness determination of zirconia toughened alumina ceramics from growth of indentation-induced cracks

International Nuclear Information System (INIS)

Basu, D.; Sarkar, B.K.

1996-01-01

Short surface cracks were generated by Vickers indentation on the polished surface of alumina and different zirconia toughened alumina (ZTA) specimens, and their morphology was studied by serial sectioning. These cracks were grown in three-point bend tests under stepwise loading, and variation of toughness with crack extension was plotted to graphically separate the contributions from residual stress intensity and applied stress intensity factors. The plateau toughness determined from the intercept height of the crack extension plots exhibited an upward trend with zirconia content up to 15 vol% ZrO 2 addition in the composition, which was proportional to the fraction of transformable tetragonal grains contributing to transformation toughening. copyright 1996 Materials Research Society

Experimental analysis of quasi-static and dynamic fracture initiation toughness of gy4 armor steel material

Science.gov (United States)

Ren, Peng; Guo, Zitao

Quasi-static and dynamic fracture initiation toughness of gy4 armour steel material are investigated using three point bend specimen. The modified split Hopkinson pressure bar (SHPB) apparatus with digital image correlation (DIC) system is applied to dynamic loading experiments. Full-field deformation measurements are obtained by using DIC to elucidate on the strain fields associated with the mechanical response. A series of experiments are conducted at different strain rate ranging from 10-3 s-1 to 103 s-1, and the loading rate on the fracture initiation toughness is investigated. Specially, the scanning electron microscope imaging technique is used to investigate the fracture failure micromechanism of fracture surfaces. The gy4 armour steel material fracture toughness is found to be sensitive to strain rate and higher for dynamic loading as compared to quasi-static loading. This work is supported by National Nature Science Foundation under Grant 51509115.

Effects of low upper shelf fracture toughness on reactor vessel integrity during pressurized thermal shock events

International Nuclear Information System (INIS)

Bamford, W.H.; Heinecke, C.C.; Balkey, K.R.

1988-01-01

For the past decade, significant attention has been focused on the subject of nuclear rector vessel integrity during pressurized thermal shock (PTS) events. The issue of low upper shelf fracture toughness at operating temperatures has been a consideration for some reactor vessel materials since the early 1970's. Deterministic and probabilistic fracture mechanics sensitivity studies have been completed to evaluate the interaction between the PTS and lower upper shelf toughness issues that result from neutron embrittlement of the critical beltline region materials. This paper presents the results of these studies to show the interdependency of these fracture considerations in certain instances and to identify parameters that need to be carefully treated in reactor vessel integrity evaluations for these subjects. This issue is of great importance to those vessels which have low upper shelf toughness, both for demonstrating safety during the original design life and in life extension assessments

The toughness of cold worked 316 stainless steel at 20 degrees C

Energy Technology Data Exchange (ETDEWEB)

Chipperfield, C G [UKAEA, RNPDL, Risley (United Kingdom)

1977-07-01

General Yielding Fracture Mechanics Concepts have been used to evaluate and compare thickness effects, J-integral estimation procedures and methods of crack detection in three point bend test pieces of prestrained 316 stainless steel. The results suggest that no thickness effects will exist in irradiated test pieces so long as the failure mode is one of ductile fracture. The choice of toughness parameter, whether fracture initiation be characterised in terms of the contour integral J or Crack Opening Displacement, appears to be relatively unimportant since both criteria appear to predict critical defect sizes of similar magnitude. Suitable crack monitoring procedures have been evaluated for subsequent irradiated tests, and it would appear that a direct current potential drop technique is the most sensitive for a given specimen geometry and toughness level. (author)

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

International Nuclear Information System (INIS)

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

1991-11-01

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

Designing tough and fracture resistant polypropylene/multi wall carbon nanotubes nanocomposites by controlling stereo-complexity and dispersion morphology

International Nuclear Information System (INIS)

Das, Dibyendu; Satapathy, Bhabani K.

2014-01-01

Highlights: • New pathway to improve dispersion and toughness by tacticity modification. • >330% toughness enhancement in PP/MWCNT nanocomposites with stereo-complex PP. • Prominent dispersion and distribution morphology due to matrix stereocomplexity. • Tacticity induced “Semi-ductile-to-tough-to-quasi-brittle” transitions in the PP/MWCNT. • Two-fold reduced steady state CTOD rate in i-PP+s-PP/ MWCNT nanocomposites. - Abstract: A remarkable toughness enhancement (>330%) of multi wall carbon nanotubes (MWCNT) filled stereo-complex polypropylene (PP) matrix i.e. blend of isotactic-PP and syndiotactic-PP (70:30) with differences in stereo-regularity has been observed. The enhancement has been correlated to quantifiable morphological parameters such as free-space lengths concerning dispersion and relatively greater reduction in crystallite size/lamellar thickness. Systematic analysis of glass transition data and estimation of multi wall carbon nanotubes induced reduction in interfacial polymer chain immobilization reiterates susceptibility of polymer segments to ready-mobility. The extent of toughening has quantitatively been analyzed by fracture-energy partitioning, essential work of fracture (EWF), approach enabling the detection of a “semi-ductile-to-tough-to-quasi-brittle” transition in the MWCNT filled stereo-complex polypropylene. Real-time fracture kinetics analysis revealed toughening mechanism to be primarily blunting-assisted; an aspect also corroborated by extensive plastic flow without much energy dissipation in the inner fracture process zone. Thus the study establishes a new pathway of tacticity-defined matrix modification to toughen nanocomposites

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)

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

International Nuclear Information System (INIS)

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

1998-04-01

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

Sub-10-micrometer toughening and crack tip toughness of dental enamel.

Science.gov (United States)

Ang, Siang Fung; Schulz, Anja; Pacher Fernandes, Rodrigo; Schneider, Gerold A

2011-04-01

In previous studies, enamel showed indications to occlude small cracks in-vivo and exhibited R-curve behaviors for bigger cracks ex-vivo. This study quantifies the crack tip's toughness (K(I0),K(III0)), the crack's closure stress and the cohesive zone size at the crack tip of enamel and investigates the toughening mechanisms near the crack tip down to the length scale of a single enamel crystallite. The crack-opening-displacement (COD) profile of cracks induced by Vickers indents on mature bovine enamel was studied using atomic force microscopy (AFM). The mode I crack tip toughness K(I0) of cracks along enamel rod boundaries and across enamel rods exhibit a similar range of values: K(I0,Ir)=0.5-1.6MPa m(0.5) (based on Irwin's 'near-field' solution) and K(I0,cz)=0.8-1.5MPa m(0.5) (based on the cohesive zone solution of the Dugdale-Muskhelishvili (DM) crack model). The mode III crack tip toughness K(III0,Ir) was computed as 0.02-0.15MPa m(0.5). The crack-closure stress at the crack tip was computed as 163-770 MPa with a cohesive zone length and width 1.6-10.1μm and 24-44 nm utilizing the cohesive zone solution. Toughening elements were observed under AFM and SEM: crack bridging due to protein ligament and hydroxyapatite fibres (micro- and nanometer scale) as well as microcracks were identified. Crown Copyright © 2010. Published by Elsevier Ltd. All rights reserved.

Proposed rule package on fracture toughness and thermal annealing requirements and guidance for light water reactor vessels

International Nuclear Information System (INIS)

Allen Hiser, J.R.

1993-01-01

In the framework of updating and clarification of the fracture toughness and thermal annealing requirements and guidance for light water reactor pressure vessels, proposed revisions concerning the pressurized thermal shock rule, fracture toughness requirements and reactor vessel material surveillance program requirements, are described. A new rule concerning thermal annealing requirements and a draft regulatory guide on 'Format and Content of Application for Approval for Thermal Annealing of RPV' are also proposed

Proposed rule package on fracture toughness and thermal annealing requirements and guidance for light water reactor vessels

Energy Technology Data Exchange (ETDEWEB)

Allen Hiser, J R [UKAEA Harwell Lab. (United Kingdom). Engineering Div.

1994-12-31

In the framework of updating and clarification of the fracture toughness and thermal annealing requirements and guidance for light water reactor pressure vessels, proposed revisions concerning the pressurized thermal shock rule, fracture toughness requirements and reactor vessel material surveillance program requirements, are described. A new rule concerning thermal annealing requirements and a draft regulatory guide on `Format and Content of Application for Approval for Thermal Annealing of RPV` are also proposed.

The concept of fatigue fracture toughness in fatigue delamination growth behavior

NARCIS (Netherlands)

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

2015-01-01

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

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)

Effects of Rare Earth on the Microstructure and Impact Toughness of H13 Steel

Directory of Open Access Journals (Sweden)

Jinzhu Gao

2015-03-01

Full Text Available Studies of H13 steel suggest that under appropriate conditions, additions of rare-earth metals (REM can significantly enhance mechanical properties, such as impact toughness. This improvement is apparently due to the formation of finer and more dispersive RE inclusions and grain refinement after REM additions. In this present work, the microstructure evolution and mechanical properties of H13 steel with rare earth additions (0, 0.015, 0.025 and 0.1 wt.% were investigated. The grain size, inclusions and fracture morphology were systematically studied by means of optical microscopy (OM, scanning electron microscopy (SEM and transmission electron microscopy (TEM. The results indicate that REM addition of 0.015 wt.% can result in good improvement of performance compared to the REM additions of 0.025 wt.% and 0.1 wt.%. It is found that the impact toughness is significantly enhanced with the addition of 0.015% REM, which can be improved 90% from 10 J to 19 J. Such an addition of REM can result in a huge volume fraction of finer and more dispersive inclusions which are extremely good to toughness.

Tough and Conductive Hybrid Hydrogels Enabling Facile Patterning.

Science.gov (United States)

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

2018-04-25

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

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

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.

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

International Nuclear Information System (INIS)

Garrison, Warren M.; Maloney, James L.

2005-01-01

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

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.)

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

Energy Technology Data Exchange (ETDEWEB)

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

1992-11-01

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

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.

Role of the gender-linked norm of toughness in the decision to engage in treatment for depression.

Science.gov (United States)

O'Loughlin, Ryan E; Duberstein, Paul R; Veazie, Peter J; Bell, Robert A; Rochlen, Aaron B; Fernandez y Garcia, Erik; Kravitz, Richard L

2011-07-01

Given their prevalence and persuasive power in our culture, gender norms--commonly described as socially reinforced, learned expectations of what it means to be a man or a woman--likely contribute to sex differences in service utilization for depression. This study investigated whether sex differences in toughness, a gender-linked norm characterized by a desire to hide pain and maintain independence, were associated with a preference to wait for depression to resolve on its own without active professional treatment ("wait-and-see" approach). Participants (N=1,051) in the California Behavioral Risk Factor Surveillance System (BRFSS) survey were contacted in a follow-on survey to assess toughness, the kind of treatment they would prefer were they to receive a diagnosis of depression, and current symptoms of depression. Participants who reported ever having been diagnosed as having a depressive disorder on the BRFSS were oversampled threefold. Analyses were conducted using linear and logistic regressions. Men and women who scored higher on toughness had a greater preference for the wait-and-see approach (OR=1.14, pdifference in treatment preferences (OR=.91, pdifference observed in treatment-seeking preferences, but toughness undermined women's treatment seeking as well. Findings could be used to inform novel public health communications intended to attract both men and women to psychiatric services.

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.

Fracture toughness for copper oxide superconductors

Science.gov (United States)

Goretta, K.C.; Kullberg, M.L.

1993-04-13

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].

The Investigation on Flexural Toughness of Partially Steel Fiber Reinforced Concrete Immersed by Simulated Sea-Water

Directory of Open Access Journals (Sweden)

Feng GAO

2017-11-01

Full Text Available In order to investigate the corrosive resistance of partially steel fiber reinforced concrete (PSFRC, the flexural toughness experiment of nine specimens subjected to corrosion by alternating wet and dry cycles in a simulated marine environment were conducted, which aims at investigating the effect of corrosion time, steel fiber volume fraction and SFRC thickness on PSFRC toughness. The experimental results showed that both the mechanical and ductile characteristics of PSFRC got worse due to corrosion even if increasing the steel fiber volume. Additionally, the effect of steel fiber content on the toughness and ultimate load are greater than PSFRC thickness (t. The increase of 56.6% and 171% could be obtained in the mean ultimate load and I10 if the increase of steel fiber volume is from 0.5 % to 2.0%, respectively. This paper could offer a reference to the application of PSFRC in sea-water environment.DOI: http://dx.doi.org/10.5755/j01.ms.23.4.17049

Precipitation and impact toughness of Nb–V stabilised 18Cr–2Mo ferritic stainless steel during isothermal aging

International Nuclear Information System (INIS)

Han, Jian; Li, Huijun; Barbaro, Frank; Jiang, Laizhu; Zhu, Zhixiong; Xu, Haigang; Ma, Li

2014-01-01

The effect of isothermal aging on precipitation behaviour and Charpy impact toughness of Nb–V stabilised 18Cr–2Mo ferritic stainless steel was investigated by means of Thermo-Calc prediction, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Charpy impact toughness testing. The results show that, niobium, vanadium carbides and nitrides, Fe 2 Nb (Laves phase) and Cr 23 C 6 formed after 2 h aging at 800 °C, and the equilibrium solvus temperature of Fe 2 Nb phase increases to above 750 °C, higher than the calculated temperature (730 °C) using Thermo-Calc. After isothermal aging at 750–950 °C, 2 h aging resulted in a decrease in toughness due to the formation of precipitation, especially (Nb,V)(C,N) and Fe 2 Nb. When isothermally aged at 800 °C for up to 24 h, the coarsening rate of Fe 2 Nb particle is much higher than that of (Nb,V)(C,N), and the impact toughness of the steel is dependent on quantity and sizes of (Nb,V)(C,N) and Fe 2 Nb particles

Precipitation and impact toughness of Nb–V stabilised 18Cr–2Mo ferritic stainless steel during isothermal aging

Energy Technology Data Exchange (ETDEWEB)

Han, Jian, E-mail: jh595@uowmail.edu.au [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Li, Huijun [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Barbaro, Frank [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); CBMM Technology Suisse, 14, Rue du Rhone, Geneve 1204 (Switzerland); Jiang, Laizhu [Baoshan Iron and Steel Co., Ltd., Shanghai 200431 (China); Zhu, Zhixiong [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Xu, Haigang; Ma, Li [Baoshan Iron and Steel Co., Ltd., Shanghai 200431 (China)

2014-08-26

The effect of isothermal aging on precipitation behaviour and Charpy impact toughness of Nb–V stabilised 18Cr–2Mo ferritic stainless steel was investigated by means of Thermo-Calc prediction, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Charpy impact toughness testing. The results show that, niobium, vanadium carbides and nitrides, Fe{sub 2}Nb (Laves phase) and Cr{sub 23}C{sub 6} formed after 2 h aging at 800 °C, and the equilibrium solvus temperature of Fe{sub 2}Nb phase increases to above 750 °C, higher than the calculated temperature (730 °C) using Thermo-Calc. After isothermal aging at 750–950 °C, 2 h aging resulted in a decrease in toughness due to the formation of precipitation, especially (Nb,V)(C,N) and Fe{sub 2}Nb. When isothermally aged at 800 °C for up to 24 h, the coarsening rate of Fe{sub 2}Nb particle is much higher than that of (Nb,V)(C,N), and the impact toughness of the steel is dependent on quantity and sizes of (Nb,V)(C,N) and Fe{sub 2}Nb particles.

Fatigue and fracture toughness characteristics of laser rapid manufactured Inconel 625 structures

International Nuclear Information System (INIS)

Ganesh, P.; Kaul, R.; Paul, C.P.; Tiwari, Pragya; Rai, S.K.; Prasad, R.C.; Kukreja, L.M.

2010-01-01

Research highlights: → Mechanical test results of Laser rapid manufactured (LRM) Inconel 625 are reported. → 12 and 25 mm thick CT specimens of LRM Inconel 625 showed similar fatigue crack growth. → Stage II crack growth behavior is observed in the investigated ΔK range. → Fracture toughness testing by J-integral method yielded J 1c of about 200-250 kJ/m 2 . - Abstract: Fatigue crack growth and fracture toughness characteristics of laser rapid manufactured (LRMed) Inconel 625 compact tension specimens of thickness 12 and 25 mm were investigated. Fatigue crack propagation in all the specimens investigated in the stress intensity range (ΔK) of 14-38 MPa√m, exhibited stage II crack growth in Paris' regime with nearly same slopes of crack growth per cycle versus ΔK plot. Fatigue crack growth rates in the LRMed specimens of present study were found to be lower than the reported values for wrought Inconel 625 in the ΔK range of 14-24 MPa√m and above this range they tended to coincide. X-ray diffraction patterns of the fractured surfaces revealed that the crack propagated along the growth direction of the specimens which was predominantly along the (1 1 1) plane. The fracture toughness values (J 0.2 ) for LRMed Inconel 625 specimens were found to be in the range of about 200-255 kJ/m 2 . The LRMed specimens exhibited stable crack growth during the J-integral test.

The radiation swelling effect on fracture properties and fracture mechanisms of irradiated austenitic steels. Part I. Ductility and fracture toughness

Energy Technology Data Exchange (ETDEWEB)

Margolin, B., E-mail: mail@crism.ru; Sorokin, A.; Shvetsova, V.; Minkin, A.; Potapova, V.; Smirnov, V.

2016-11-15

The radiation swelling effect on the fracture properties of irradiated austenitic steels under static loading has been studied and analyzed from the mechanical and physical viewpoints. Experimental data on the stress-strain curves, fracture strain, fracture toughness and fracture mechanisms have been represented for austenitic steel of 18Cr-10Ni-Ti grade (Russian analog of AISI 321 steel) irradiated up to neutron dose of 150 dpa with various swelling. Some phenomena in mechanical behaviour of irradiated austenitic steels have been revealed and explained as follows: a sharp decrease of fracture toughness with swelling growth; untypical large increase of fracture toughness with decrease of the test temperature; some increase of fracture toughness after preliminary cyclic loading. Role of channel deformation and channel fracture has been clarified in the properties of irradiated austenitic steel and different tendencies to channel deformation have been shown and explained for the same austenitic steel irradiated at different temperatures and neutron doses.

The effect of irradiation and irradiation temperature on the fracture toughness of cold-worked Zr-2.5 wt percent Nb

International Nuclear Information System (INIS)

Simpson, L.A.; Ellis, R.B.; Stark, D.J.; Shillinglaw, A.J.

1984-09-01

The use of fracture mechanics methods and small specimens to assess the effect of metallurgical variables on fracture toughness and critical crack length in reactor pressure tubes is reviewed. Fracture toughness tests on specimens irradiated in the NRU research reactor at 260 degrees C are described and compared with results from a previous irradiation in the WR-1 research reactor at 350 degrees C. The J-resistance curve is used as the measure of fracture toughness, and is shown to be very sensitive to the metallurgical state. The lower irradiation temperature (260 degrees C), characteristic of the operating temperature range for power reactors, has a significant effect on fracture toughness. Circumferential hydrides also have an effect. Estimates of critical crack length are made using the J-resistance data, and are seen to slightly underestimate the actual critical crack length as determined in full-scale burst tests. This conservatism is not large enough to impose a significant penalty in design applications

The influence of hydride on fracture toughness of recrystallized Zircaloy-4 cladding

Energy Technology Data Exchange (ETDEWEB)

Hsu, Hsiao-Hung, E-mail: 175877@mail.csc.com.tw [Institute of Nuclear Energy Research (INER), Lungtan Township, Taoyuan County 32546, Taiwan, ROC (China); China Steel Corporation, Hsiao Kang District, Kaohsiung 81233, Taiwan, ROC (China); Chiang, Ming-Feng [China Steel Corporation, Hsiao Kang District, Kaohsiung 81233, Taiwan, ROC (China); Chen, Yen-Chen [Institute of Nuclear Energy Research (INER), Lungtan Township, Taoyuan County 32546, Taiwan, ROC (China)

2014-04-01

In this work, RXA cladding tubes were hydrogen-charged to target hydrogen content levels between 150 and 800 wppm (part per million by weight). The strings of zirconium hydrides observed in the cross sections are mostly oriented in the circumferential direction. The fracture toughness of hydrided RXA Zircaloy-4 cladding was measured to evaluate its hydride embrittlement susceptibility. With increasing hydrogen content, the fracture toughness of hydrided RXA cladding decreases at both 25 °C and 300 °C. Moreover, highly localized hydrides (forming a hydride rim) aggravate the degradation of the fracture properties of RXA Zircaloy-4 cladding at both 25 °C and 300 °C. Brittle features in the form of quasi-cleavages and secondary cracks were observed on the fracture surface of the hydride rim, even for RXA cladding tested at 300 °C.

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

Fracture toughness of 6.4 mm (0.25 inch) Arc-Cast molybdenum and molybdenum-TZM plate at room temperature and 300 oC

International Nuclear Information System (INIS)

Shields, J.A. jr.; Lipetzky, P.; Mueller, A.J.

2001-01-01

The fracture toughness of 6.4 mm (0.25 inch) low carbon arc-cast (LCAC) molybdenum and arc-cast molybdenum-TZM alloy plate were measured at room temperature and 300 o C using compact tension specimens. The effect of crack plane orientation (longitudinal vs. transverse) and annealing practice (stress-relieved vs. recrystallized) were evaluated. Depending upon the test temperature either a standard K IC or a J-integral analysis was used to obtain the toughness value. At room temperature, regardless of alloy, orientation, or microstructure, fracture toughness values between 15 and 22 MPa m 1/2 (14 and 20 ksi in 1/2 ) were measured. These K IC values were consistent with measurements by other authors. Increasing temperature improves the toughness, due to the fact that one takes advantage of the ductile-brittle transition behavior of molybdenum. At 300 o C, the fracture toughness of recrystallized LCAC and arc-cast TZM molybdenum were also similar at approximately 64 MPa m 1/2 (58 ksi in 1/2 ). In the stress-relieved condition, however, the toughness of arc-cast TZM (91 MPa m 1/2 / 83 ksi in 1/2 ) was higher than that of the LCAC molybdenum (74 MPa m 1/2 / 67 ksi in 1/2 ). (author)

Fracture toughness of glass sealants for solid oxide fuel cell application

DEFF Research Database (Denmark)

Abdoli, Hamid; Alizadeh, Parvin; Boccaccini, Dino

2014-01-01

-opening displacements in the near regions of a crack tip. Both approaches exhibited good agreement. La-containing glass showed higher stiffness, hardness and fracture toughness, which has been related to the in-situ toughening mechanism caused by devitrification and formation of crystalline phases. © 2013 Elsevier B.V....

The Development and Validation of a Mental Toughness Scale for Adolescents

Science.gov (United States)

McGeown, Sarah; St. Clair-Thompson, Helen; Putwain, David W.

2018-01-01

The present study examined the validity of a newly developed instrument, the Mental Toughness Scale for Adolescents, which examines the attributes of challenge, commitment, confidence (abilities and interpersonal), and control (life and emotion). The six-factor model was supported using exploratory factor analysis (n = 373) and confirmatory factor…

Fracture toughness and flexural strength of Sm(Co,Fe,Cu,Zr)7-8 magnetic alloys

International Nuclear Information System (INIS)

Ren, Libo.; Hadjipanayis, George C.; Parvizi-Majidi, Azar

2003-01-01

This paper presents the results of a parametric investigation of the strength and fracture toughness of Sm 2 Co 17 type permanent magnets in the Sm(Co,Fe,Cu,Zr) 7-8 family of alloys. The strength and fracture toughness of the as-received materials were characterized as a function of temperature, loading direction, and magnetization. Since these magnets are candidates for applications with service temperatures up to 450 deg. C, the effect of thermal exposure on the mechanical properties was determined by characterizing the properties after a thermal treatment of 40 h at 450 deg. C

Proceedings of the TOUGH Workshop `95 Lawrence Berkeley Laboratory, Berkeley, California, March 20--22, 1995

Energy Technology Data Exchange (ETDEWEB)

Pruess, K. [ed.

1995-03-01

The TOUGH Workshop `95 focused on applications and enhancements of the TOUGH/MULKOM family of numerical simulation programs for complex flows in permeable media, including multiphase, multicomponent, non- isothermal, and variable-density flows. There were about 100 participants from 10 countries in attendance. The topical areas covered included environmental remediation, nuclear waste isolation, geothermal and petroleum reservoir engineering, mining engineering, vadose zone hydrology, and simulation methods. This volume features the extended summaries of papers that were presented at the workshop. The technical program and lists of authors and registered participants are included in appendices. Individual papers have been processed separately for the databases.

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.

Determination of the toughness of a low alloy steel from the Charpy V-notch impact testing

International Nuclear Information System (INIS)

Rossoll, A.

1998-12-01

Charpy V-notch (CVN) impact testing is widely used to characterize the resistance of a material to brittle fracture, by measuring the energy consumed by a specimen during impact. Notably materials undergoing a ductile-to-brittle transition, e.g. ferritic steels, are quality controlled by means of CVN testing, and their ductile-to-brittle transition temperature can be determined. Charpy testing is also widely used in the toughness assessment of large forged components, e.g. pressure vessels for pressurised water reactors (PWR). However, currently no satisfactory link between the Charpy impact energy CVN and the fracture toughness KIc exists. This study aims to establish a non-empirical relationship between the Charpy V-notch energy CVN, and the fracture toughness KIc, on the lower shelf of fracture toughness and the onset of the ductile-to-brittle transition of a A508 Cl.3 steel. The methodology employed is based on the so-called 'local approach'. Brittle cleavage fracture is modelled in terms of the Beremin (1983) model based on 'weakest link' statistics, whereas ductile crack advance preceding cleavage in the transition region is accounted for with the GTN model (Gurson, 1977; Tvergaard, 1982; Tvergaard and Needleman, 1984). Mechanical testing at different strain rates allowed for the establishment of the constitutive equations of the material in an elastic-viscoplastic formulation. Fracture tests on different specimen geometries provided the large data set necessary for statistical evaluation. All specimen types have been modelled with finite element analysis. However, the dynamic nature of the Charpy test requires special consideration. The origin of these dynamic effects was studied, as well as their implications on interpretation of experimental results and on modeling. After a proper modeling procedure had been defined, the local approach was employed for studying fracture. It is found that the fracture toughness can be predicted from the Charpy impact test

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

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

Directory of Open Access Journals (Sweden)

Vellapandian Ponnusamy

2018-05-01

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

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

African Journals Online (AJOL)

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