WorldWideScience

Sample records for fracture mechanical analysis

  1. Fracture Mechanics

    International Nuclear Information System (INIS)

    Jang, Dong Il; Jeong, Gyeong Seop; Han, Min Gu

    1992-08-01

    This book introduces basic theory and analytical solution of fracture mechanics, linear fracture mechanics, non-linear fracture mechanics, dynamic fracture mechanics, environmental fracture and fatigue fracture, application on design fracture mechanics, application on analysis of structural safety, engineering approach method on fracture mechanics, stochastic fracture mechanics, numerical analysis code and fracture toughness test and fracture toughness data. It gives descriptions of fracture mechanics to theory and analysis from application of engineering.

  2. Fracture mechanics

    International Nuclear Information System (INIS)

    Miannay, D.P.

    1995-01-01

    This book entitle ''Fracture Mechanics'', the first one of the monograph ''Materiologie'' is geared to design engineers, material engineers, non destructive inspectors and safety experts. This book covers fracture mechanics in isotropic homogeneous continuum. Only the monotonic static loading is considered. This book intended to be a reference with the current state of the art gives the fundamental of the issues under concern and avoids the developments too complicated or not yet mastered for not making reading cumbersome. The subject matter is organized as going from an easy to a more complicated level and thus follows the chronological evolution in the field. Similarly the microscopic scale is considered before the macroscopic scale, the physical understanding of phenomena linked to the experimental observation of the material preceded the understanding of the macroscopic behaviour of structures. In this latter field the relatively recent contribution of finite element computations with some analogy with the experimental observation is determining. However more sensitive analysis is not skipped

  3. Selection of pipeline steels with an engineering fracture mechanical analysis

    Energy Technology Data Exchange (ETDEWEB)

    Stenbacka, N [Swedish State Power Board, Vaellingby

    1985-01-01

    Selection of pipeline steels is discussed on the basis of two mutually independent failure mechanisms: elastic fracture and plastic collapse. The presentation is restricted to axial flaws. A formal analysis shows that brittle fracture in modern pipelines has no high priority in design, since steels used today have a high fracture toughness. Instead, a case of practical concern is tha plastic collapse mode, where failure is flow stress controlled. Conditions governing this design case are specified. In conjunction with this, criterions for material selection with regard to fracture toughness is presented.

  4. [Mechanics analysis of fracture of orthodontic wires].

    Science.gov (United States)

    Wang, Yeping; Sun, Xiaoye; Zhang, Longqi

    2003-03-01

    Fracture problem of orthodontic wires was discussed in this paper. The calculation formulae of bending stress and tensile stress were obtained. All main factors that affect bending stress and tensile stress of orthodontic wires were analyzed and discussed. It was concluded that the main causes of fracture of orthodontic wires were fatigue and static disruption. Some improving proposals for preventing fracture of orthodontic wires were put forward.

  5. Fracture Mechanics

    CERN Document Server

    Zehnder, Alan T

    2012-01-01

    Fracture mechanics is a vast and growing field. This book develops the basic elements needed for both fracture research and engineering practice. The emphasis is on continuum mechanics models for energy flows and crack-tip stress- and deformation fields in elastic and elastic-plastic materials. In addition to a brief discussion of computational fracture methods, the text includes practical sections on fracture criteria, fracture toughness testing, and methods for measuring stress intensity factors and energy release rates. Class-tested at Cornell, this book is designed for students, researchers and practitioners interested in understanding and contributing to a diverse and vital field of knowledge. Alan Zehnder joined the faculty at Cornell University in 1988. Since then he has served in a number of leadership roles including Chair of the Department of Theoretical and Applied Mechanics, and Director of the Sibley School of Mechanical and Aerospace Engineering.  He teaches applied mechanics and his research t...

  6. Uncertainty analysis on probabilistic fracture mechanics assessment methodology

    International Nuclear Information System (INIS)

    Rastogi, Rohit; Vinod, Gopika; Chandra, Vikas; Bhasin, Vivek; Babar, A.K.; Rao, V.V.S.S.; Vaze, K.K.; Kushwaha, H.S.; Venkat-Raj, V.

    1999-01-01

    Fracture Mechanics has found a profound usage in the area of design of components and assessing fitness for purpose/residual life estimation of an operating component. Since defect size and material properties are statistically distributed, various probabilistic approaches have been employed for the computation of fracture probability. Monte Carlo Simulation is one such procedure towards the analysis of fracture probability. This paper deals with uncertainty analysis using the Monte Carlo Simulation methods. These methods were developed based on the R6 failure assessment procedure, which has been widely used in analysing the integrity of structures. The application of this method is illustrated with a case study. (author)

  7. Fracture mechanics

    CERN Document Server

    Perez, Nestor

    2017-01-01

    The second edition of this textbook includes a refined presentation of concepts in each chapter, additional examples; new problems and sections, such as conformal mapping and mechanical behavior of wood; while retaining all the features of the original book. The material included in this book is based upon the development of analytical and numerical procedures pertinent to particular fields of linear elastic fracture mechanics (LEFM) and plastic fracture mechanics (PFM), including mixed-mode-loading interaction. The mathematical approach undertaken herein is coupled with a brief review of several fracture theories available in cited references, along with many color images and figures. Dynamic fracture mechanics is included through the field of fatigue and Charpy impact testing. Explains computational and engineering approaches for solving crack-related problems using straightforward mathematics that facilitate comprehension of the physical meaning of crack growth processes; Expands computational understandin...

  8. Japanese round robin analysis for probabilistic fracture mechanics

    International Nuclear Information System (INIS)

    Yagawa, G.; Yoshimura, S.; Handa, N.

    1991-01-01

    Recently attention is focused on the probabilistic fracture mechanics, a branch of fracture mechanics with probability theory for a rational mean to assess the strength of components and structures. In particular, the probabilistic fracture mechanics is recognized as the powerful means for quantitative investigation of significance of factors and rational evaluation of life on problems involving a number of uncertainties, such as degradation of material strength, accuracy and frequency of inspection. Comparison with reference experiments are generally employed to assure the analytical accuracy. However, accuracy and reliability of analytical methods in the probabilistic fracture mechanics are hardly verified by experiments. Therefore, it is strongly needed to verify the probabilistic fracture mechanics through the round robin analysis. This paper describes results from the round robin analysis of flat plate with semi-elliptic cracks on the surface, conducted by the PFM Working Group of LE Subcommittee of the Japan Welding Society under the contract of the Japan Atomic Energy Research Institute and participated by Tokyo University, Yokohama National University, the Power Reactor and Nuclear Fuel Corporation, Tokyo Electric Power Co. Central Research Institute of Electric Power Industry, Toshiba Corporation, Kawasaki Heavy Industry Co. and Mitsubishi Heavy Industry Co. (author)

  9. Spartan Release Engagement Mechanism (REM) stress and fracture analysis

    Science.gov (United States)

    Marlowe, D. S.; West, E. J.

    1984-01-01

    The revised stress and fracture analysis of the Spartan REM hardware for current load conditions and mass properties is presented. The stress analysis was performed using a NASTRAN math model of the Spartan REM adapter, base, and payload. Appendix A contains the material properties, loads, and stress analysis of the hardware. The computer output and model description are in Appendix B. Factors of safety used in the stress analysis were 1.4 on tested items and 2.0 on all other items. Fracture analysis of the items considered fracture critical was accomplished using the MSFC Crack Growth Analysis code. Loads and stresses were obtaind from the stress analysis. The fracture analysis notes are located in Appendix A and the computer output in Appendix B. All items analyzed met design and fracture criteria.

  10. 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

  11. NASGRO(registered trademark): Fracture Mechanics and Fatigue Crack Growth Analysis Software

    Science.gov (United States)

    Forman, Royce; Shivakumar, V.; Mettu, Sambi; Beek, Joachim; Williams, Leonard; Yeh, Feng; McClung, Craig; Cardinal, Joe

    2004-01-01

    This viewgraph presentation describes NASGRO, which is a fracture mechanics and fatigue crack growth analysis software package that is used to reduce risk of fracture in Space Shuttles. The contents include: 1) Consequences of Fracture; 2) NASA Fracture Control Requirements; 3) NASGRO Reduces Risk; 4) NASGRO Use Inside NASA; 5) NASGRO Components: Crack Growth Module; 6) NASGRO Components:Material Property Module; 7) Typical NASGRO analysis: Crack growth or component life calculation; and 8) NASGRO Sample Application: Orbiter feedline flowliner crack analysis.

  12. Comparative analysis of deterministic and probabilistic fracture mechanical assessment tools

    Energy Technology Data Exchange (ETDEWEB)

    Heckmann, Klaus [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) gGmbH, Koeln (Germany); Saifi, Qais [VTT Technical Research Centre of Finland, Espoo (Finland)

    2016-11-15

    Uncertainties in material properties, manufacturing processes, loading conditions and damage mechanisms complicate the quantification of structural reliability. Probabilistic structure mechanical computing codes serve as tools for assessing leak- and break probabilities of nuclear piping components. Probabilistic fracture mechanical tools were compared in different benchmark activities, usually revealing minor, but systematic discrepancies between results of different codes. In this joint paper, probabilistic fracture mechanical codes are compared. Crack initiation, crack growth and the influence of in-service inspections are analyzed. Example cases for stress corrosion cracking and fatigue in LWR conditions are analyzed. The evolution of annual failure probabilities during simulated operation time is investigated, in order to identify the reasons for differences in the results of different codes. The comparison of the tools is used for further improvements of the codes applied by the partners.

  13. Why ductile fracture mechanics

    International Nuclear Information System (INIS)

    Ritchie, R.O.

    1983-01-01

    Until recently, the engineering application of fracture mechanics has been specific to a description of macroscopic fracture behavior in components and structural parts which remain nominally elastic under loading. While this approach, termed linear elastic fracture mechanics, has been found to be invaluable for the continuum analysis of crack growth in brittle and high strength materials, it is clearly inappropriate for characterizing failure in lower strength ductile alloys where extensive inelastic deformation precedes and accompanies crack initiation and subsequent propagation. Accordingly, much effort has been devoted in recent years toward the development of nonlinear or ductile fracture mechanics methodology to characterize fracture behavior under elastic/plastic conditions; an effort which has been principally motivated by problems in nuclear industry. In this paper, the concepts of ductile (elastic/plastic) fracture mechanics are introduced and applied to the problem of both stationary and nonstationary cracks. Specifically, the limitations inherent in this approach are defined, together with a description of the microstructural considerations and applications relevant to the failure of ductile materials by fracture, fatigue, and creep

  14. Classical fracture mechanics methods

    International Nuclear Information System (INIS)

    Schwalbe, K.H.; Heerens, J.; Landes, J.D.

    2007-01-01

    Comprehensive Structural Integrity is a reference work which covers all activities involved in the assurance of structural integrity. It provides engineers and scientists with an unparalleled depth of knowledge in the disciplines involved. The new online Volume 11 is dedicated to the mechanical characteristics of materials. This paper contains the chapter 11.02 of this volume and is structured as follows: Test techniques; Analysis; Fracture behavior; Fracture toughness tests for nonmetals

  15. comparison of elastic-plastic FE method and engineering method for RPV fracture mechanics analysis

    International Nuclear Information System (INIS)

    Sun Yingxue; Zheng Bin; Zhang Fenggang

    2009-01-01

    This paper described the FE analysis of elastic-plastic fracture mechanics for a crack in RPV belt line using ABAQUS code. It calculated and evaluated the stress intensity factor and J integral of crack under PTS transients. The result is also compared with that by engineering analysis method. It shows that the results using engineering analysis method is a little larger than the results using FE analysis of 3D elastic-plastic fracture mechanics, thus the engineering analysis method is conservative than the elastic-plastic fracture mechanics method. (authors)

  16. Fracture mechanical materials characterisation

    International Nuclear Information System (INIS)

    Wallin, K.; Planman, T.; Nevalainen, M.

    1998-01-01

    The experimental fracture mechanics development has been focused on the determination of reliable lower-bound fracture toughness estimates from small and miniature specimens, in particular considering the statistical aspects and loading rate effects of fracture mechanical material properties. Additionally, materials aspects in fracture assessment of surface cracks, with emphasis on the transferability of fracture toughness data to structures with surface flaws have been investigated. Further a modified crack-arrest fracture toughness test method, to increase the effectiveness of testing, has been developed. (orig.)

  17. Fracture mechanical analysis of strengthened concrete tension members with one crack

    DEFF Research Database (Denmark)

    Hansen, Christian Skodborg; Stang, Henrik

    2012-01-01

    A concrete tension member strengthened 2 with fiber reinforced polymer plates on two sides 3 is analyzed with non-linear fracture mechanics. The 4 analysis of the strengthened tension member incorpo5 rates cohesive properties for both concrete and inter6 face between concrete and strengthening...... the structural classification parameters, is inves13 tigated in a non-dimensional analysis, and found to 14 depend strongly on the ratio between interfacial and 15 concrete fracture energies....

  18. Development of Numerical Analysis Techniques Based on Damage Mechanics and Fracture Mechanics

    International Nuclear Information System (INIS)

    Chang, Yoon Suk; Lee, Dock Jin; Choi, Shin Beom; Kim, Sun Hye; Cho, Doo Ho; Lee, Hyun Boo

    2010-04-01

    The scatter of measured fracture toughness data and transferability problems among different crack configurations as well as geometry and loading conditions are major obstacles for application of fracture mechanics. To address these issues, recently, concerns on the local approach employing reliable micro-mechanical damage models are being increased again in connection with a progress of computational technology. In the present research, as part of development of fracture mechanical evaluation model for material degradation of reactor pressure boundary, several investigations on fracture behaviors were carried out. Especially, a numerical scheme to determine key parameters consisting both cleavage and ductile fracture estimate models was changed efficiently by incorporating a genetic algorithm. Also, with regard to the well-known master curve, newly reported methods such as bimodal master curve, randomly inhomogeneous master curve and single point estimation were reviewed to deal with homogeneous and inhomogeneous material characteristics. A series of preliminary finite element analyses was conducted to examine the element size effect on micro-mechanical models. Then, a new thickness correction equation was derived from parametric three-dimensional numerical simulations, which was founded on the current test standard, ASTM E1921, but could lead to get more realistic fracture toughness values. As a result, promising modified master curves as well as fracture toughness diagrams to convert data between pre-cracked V-notched and compact tension specimens were generated. Moreover, a user-subroutine in relation to GTN(Gurson-Tvergaard-Needleman) model was made by adopting Hill's 48 yield potential theory. By applying GTN model combined with the subroutine to small punch specimens, the effect of inhomogeneous properties on fracture behaviors of miniature specimens was confirmed. Therefore, it is anticipated that the aforementioned enhanced research results can be utilized

  19. Probabilistic fracture mechanics analysis of reactor vessel for pressurized thermal shock: the effect of residual stress and fracture toughness

    International Nuclear Information System (INIS)

    Jung, Sung Gyu; Jin, Tae Eun; Jhung, Myung Jo; Choi, Young Hwan

    2003-01-01

    The structural integrity of the reactor vessel with the approaching end of life must be assured for pressurized thermal shock. The regulation specifies the screening criteria for this and requires that specific analysis be performed for the reactor vessel which is anticipated to exceed the screening criteria at the end of plant life. In case the screening criteria is exceeded by the deterministic analysis, probabilistic analysis must be performed to show that failure probability is within the limit. In this study, probabilistic fracture mechanics analysis of the reactor vessel for pressurized thermal shock is performed and the effects of residual stress and master curve on the failure probability are investigated

  20. Mechanical strength and analysis of fracture of titanium joining submitted to laser and tig welding

    Directory of Open Access Journals (Sweden)

    Ana Cláudia Gabrielli Piveta

    2012-12-01

    Full Text Available This study compared the tensile strength and fracture mechanism of tungsten inert gas (TIG welds in cylindrical rods of commercially pure titanium (cp Ti with those of laser welds and intact samples. Thirty dumbbell-shaped samples were developed by using brass rods as patterns. The samples were invested in casings, subjected to thermal cycles, and positioned in a plasma arc welding machine under argon atmosphere and vacuum, and titanium was injected under vacuum/pressure. The samples were X-rayed to detect possible welding flaws and randomly assigned to three groups to test the tensile strength and the fracture mechanism: intact, laser welding, and TIG welding. The tensile test results were investigated using ANOVA, which indicated that the samples were statistically similar. The fracture analysis showed that the cpTi samples subjected to laser welding exhibited brittle fracture and those subjected to TIG welding exhibited mixed brittle/ductile fracture with a predominance of ductile fracture with the presence of microcavities and cleavage areas. Intact samples presented the characteristic straightening in the fracture areas, indicating the ductility of the material.

  1. Numerical Analysis and Experimental Study of Hard Roofs in Fully Mechanized Mining Faces under Sleeve Fracturing

    Directory of Open Access Journals (Sweden)

    Zhitao Zheng

    2015-11-01

    Full Text Available Sudden falls of large-area hard roofs in a mined area release a large amount of elastic energy, generate dynamic loads, and cause disasters such as impact ground pressure and gas outbursts. To address these problems, in this study, the sleeve fracturing method (SFM was applied to weaken a hard roof. The numerical simulation software FLAC3D was used to develop three models based on an analysis of the SFM working mechanism. These models were applied to an analysis of the fracturing effects of various factors such as the borehole diameter, hole spacing, and sleeve pressure. Finally, the results of a simulation were validated using experiments with similar models. Our research indicated the following: (1 The crack propagation directions in the models were affected by the maximum principal stress and hole spacing. When the borehole diameter was fixed, the fracturing pressure increased with increasing hole spacing. In contrast, when the fracturing pressure was fixed, the fracturing range increased with increasing borehole diameter; (2 The most ideal fracturing effect was found at a fracturing pressure of 17.6 MPa in the model with a borehole diameter of 40 mm and hole spacing of 400 mm. The results showed that it is possible to regulate the falls of hard roofs using the SFM. This research may provide a theoretical basis for controlling hard roofs in mining.

  2. Fracture mechanics safety approaches

    International Nuclear Information System (INIS)

    Roos, E.; Schuler, X.; Eisele, U.

    2004-01-01

    Component integrity assessments require the knowledge of reliable fracture toughness parameters characterising the initiation of the failure process in the whole relevant temperature range. From a large number of fracture mechanics tests a statistically based procedure was derived allowing to quantify the initiation of fracture toughness as a function of temperature as a closed function as well as the temperature dependence of the cleavage instability parameters. Alternatively to the direct experimental determination one also can use a correlation between fracture toughness and notch impact energy. (orig.)

  3. Elevated temperature fracture mechanics

    International Nuclear Information System (INIS)

    Tomkins, B.

    1979-01-01

    The application of fracture mechanics concepts to cracks at elevated temperatures is examined. Particular consideration is given to the characterisation of crack tip stress-strain fields and parameters controlling crack extension under static and cyclic loads. (author)

  4. An experimental analysis of fracture mechanisms by acoustic ...

    African Journals Online (AJOL)

    Afin d'analyser le comportement mécanique globale de l'assemblage, des essais de traction .... named as Groups A, B and C (Tab. 5). Table.1: Mechanical properties of epoxy matrix Vicotex 914. Table.2: Mechanical properties of fibers T300. Young. 's modul us. E. Poisson's ratio. Ν shear modulus. G. Tensile strength yield.

  5. An experimental analysis of fracture mechanisms by acoustic ...

    African Journals Online (AJOL)

    This work is focused on the study of the evolution of damage mode and failure mechanisms of woven composite bolted assembly carbon fiber/epoxy. In the present paper three configurations are studied [0°,45°,0°,45°], [0°,45°,0°,45°]s and [0°,45°,0°,45,0°]s. In order to analyze a global mechanical behavior of the assembly, ...

  6. Generalised fracture mechanics approach to the interfacial failure analysis of a bonded steel-concrete joint

    Czech Academy of Sciences Publication Activity Database

    De Corte, W.; Helincks, P.; Boel, V.; Klusák, Jan; Seitl, Stanislav; De Schutter, G.

    2017-01-01

    Roč. 11, č. 42 (2017), s. 147-160 ISSN 1971-8993 R&D Projects: GA MŠk(CZ) LQ1601; GA ČR(CZ) GA16-18702S Institutional support: RVO:68081723 Keywords : Epoxy adhesive * Fracture mechanics * Interfacial properties * Numerical study * Push-out test * Steel-concrete joint Subject RIV: JL - Materials Fatigue, Friction Mechanics OBOR OECD: Audio engineering, reliability analysis

  7. Fracture Mechanics Assessment for Different Notch Sizes Using Finite Element Analysis Based on Ductile Failure Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Keun Hyung; Jeon, Jun Young; Han, Jae Jun; Nam, Hyun Suk; Lee, Dae Young; Kim, Yun Jae [Korea Univ., Seoul (Korea, Republic of)

    2016-08-15

    In this study, notch defects are evaluated using fracture mechanics. To understand the effects of notch defects, FE analysis is conducted to predict the limit load and J-integral for middle-cracked and single-edge cracked plates with various sizes of notch under tension and bending. As the radius of the notch increases, the energy release rate also increases, although the limit load remains constant. The values of fracture toughness(J{sub IC}) of SM490A are determined for various notch radii through FE simulation instead of conducting an experiment. As the radius of the notch increases, the energy release rate also increases, together with a more significant increase in fracture toughness. To conclude, as the notch radius increases, the resistance to crack propagation also increases.

  8. Elastic plastic fracture mechanics

    International Nuclear Information System (INIS)

    Simpson, L.A.

    1978-07-01

    The application of linear elastic fracture mechanics (LEFM) to crack stability in brittle structures is now well understood and widely applied. However, in many structural materials, crack propagation is accompanied by considerable crack-tip plasticity which invalidates the use of LEFM. Thus, present day research in fracture mechanics is aimed at developing parameters for predicting crack propagation under elastic-plastic conditions. These include critical crack-opening-displacement methods, the J integral and R-curve techniques. This report provides an introduction to these concepts and gives some examples of their applications. (author)

  9. Analysis of the applicability of fracture mechanics on the basis of large scale specimen testing

    International Nuclear Information System (INIS)

    Brumovsky, M.; Polachova, H.; Sulc, J.; Anikovskij, V.; Dragunov, Y.; Rivkin, E.; Filatov, V.

    1988-01-01

    The verification is dealt with of fracture mechanics calculations for WWER reactor pressure vessels by large scale model testing performed on the large testing machine ZZ 8000 (maximum load of 80 MN) in the Skoda Concern. The results of testing a large set of large scale test specimens with surface crack-type defects are presented. The nominal thickness of the specimens was 150 mm with defect depths between 15 and 100 mm, the testing temperature varying between -30 and +80 degC (i.e., in the temperature interval of T ko ±50 degC). Specimens with a scale of 1:8 and 1:12 were also tested, as well as standard (CT and TPB) specimens. Comparisons of results of testing and calculations suggest some conservatism of calculations (especially for small defects) based on Linear Elastic Fracture Mechanics, according to the Nuclear Reactor Pressure Vessel Codes which use the fracture mechanics values from J IC testing. On the basis of large scale tests the ''Defect Analysis Diagram'' was constructed and recommended for brittle fracture assessment of reactor pressure vessels. (author). 7 figs., 2 tabs., 3 refs

  10. Fracture mechanics and microstructures

    International Nuclear Information System (INIS)

    Gee, M.G.; Morrell, R.

    1986-01-01

    The influence of microstructure on defects in ceramics, and the consequences of their presence for the application of fracture mechanics theories are reviewed. The complexities of microstructures, especially the multiphase nature, the crystallographic anisotropy and the resultant anisotropic physical properties, and the variation of microstructure and surface finish from point to point in real components, all lead to considerable uncertainties in the actual performance of any particular component. It is concluded that although the concepts of fracture mechanics have been and will continue to be most useful for the qualitative explanation of fracture phenomena, the usefulness as a predictive tool with respect to most existing types of material is limited by the interrelation between material microstructure and mechanical properties. At present, the only method of eliminating components with unsatisfactory mechanical properties is to proof-test them, despite the fact that proof-testing itself is limited in ability to cope with changes to the component in service. The aim of the manufacturer must be to improve quality and consistency within individual components, from component to component, and from batch to batch. The aim of the fracture specialist must be to study longer-term properties to improve the accuracy of behaviour predictions with a stronger data base. Materials development needs to concentrate on obtaining defect-free materials that can be translated into more-reliable products, using our present understanding of the influence of microstructure on strength and toughness

  11. Fracture mechanics and parapsychology

    Science.gov (United States)

    Cherepanov, G. P.

    2010-08-01

    The problem of postcritical deformation of materials beyond the ultimate strength is considered a division of fracture mechanics. A simple example is used to show the relationship between this problem and parapsychology, which studies phenomena and processes where the causality principle fails. It is shown that the concept of postcritical deformation leads to problems with no solution

  12. Fracture Mechanics of Concrete

    DEFF Research Database (Denmark)

    Ulfkjær, Jens Peder

    Chapter 1 Chapter l contains the introduction to this thesis. The scope of the thesis is partly to investigate different numerical and analytical models based on fracture mechanical ideas, which are able to predict size effects, and partly to perform an experimental investigation on high-strength......Chapter 1 Chapter l contains the introduction to this thesis. The scope of the thesis is partly to investigate different numerical and analytical models based on fracture mechanical ideas, which are able to predict size effects, and partly to perform an experimental investigation on high......-strength concrete. Chapter 2 A description of the factors which influence the strength and cracking of concrete and high strength concrete is made. Then basic linear fracture mechanics is outlined followed by a description and evaluation of the models used to describe concrete fracture in tension. The chapter ends...... and the goveming equations are explicit and simple. These properties of the model make it a very powerful tool, which is applicable for the designing engineer. The method is also extended to reinforced concrete, where the results look very promising. The large experimental investigation on high-strength concrete...

  13. User's manual and analysis methodology of probabilistic fracture mechanics analysis code PASCAL Ver.2 for reactor pressure vessel (Contract research)

    International Nuclear Information System (INIS)

    Osakabe, Kazuya; Onizawa, Kunio; Shibata, Katsuyuki; Kato, Daisuke

    2006-09-01

    As a part of the aging structural integrity research for LWR components, the probabilistic fracture mechanics (PFM) analysis code PASCAL (PFM Analysis of Structural Components in Aging LWR) has been developed in JAEA. This code evaluates the conditional probabilities of crack initiation and fracture of a reactor pressure vessel (RPV) under transient conditions such as pressurized thermal shock (PTS). The development of the code has been aimed to improve the accuracy and reliability of analysis by introducing new analysis methodologies and algorithms considering the recent development in the fracture mechanics and computer performance. PASCAL Ver.1 has functions of optimized sampling in the stratified Monte Carlo simulation, elastic-plastic fracture criterion of the R6 method, crack growth analysis models for a semi-elliptical crack, recovery of fracture toughness due to thermal annealing and so on. Since then, under the contract between the Ministry of Economy, Trading and Industry of Japan and JAEA, we have continued to develop and introduce new functions into PASCAL Ver.2 such as the evaluation method for an embedded crack, K I database for a semi-elliptical crack considering stress discontinuity at the base/cladding interface, PTS transient database, and others. A generalized analysis method is proposed on the basis of the development of PASCAL Ver.2 and results of sensitivity analyses. Graphical user interface (GUI) including a generalized method as default values has been also developed for PASCAL Ver.2. This report provides the user's manual and theoretical background of PASCAL Ver.2. (author)

  14. Fracture Mechanics of Concrete

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    the international workshop on concrete fracture, organised by A Carpinteri, at Torino ... The next question is how to bring the size effect into codes of practice on the ... analysis of the recent collapse of the World Trade Center in New York by Z P ...

  15. A New Approach to the Modeling and Analysis of Fracture through Extension of Continuum Mechanics to the Nanoscale

    KAUST Repository

    Sendova, T.; Walton, J. R.

    2010-01-01

    In this paper we focus on the analysis of the partial differential equations arising from a new approach to modeling brittle fracture based on an extension of continuum mechanics to the nanoscale. It is shown that ascribing constant surface tension

  16. Plastic fracture mechanics prediction of fracture instability in a circumferentially cracked pipe in bending - 1. J-integral analysis

    Energy Technology Data Exchange (ETDEWEB)

    Zahoor, A.; Kanninen, M.F.

    1981-11-01

    A method of evaluating the J-integral for a circumferentially cracked pipe in bending is proposed. The method allows a J-resistance curve to be evaluated directly from the load-displacement record obtained in a pipe fracture experiment. It permits an analysis for fracture instability in a circumferential crack growth using a J-resistance curve and the tearing modulus parameter. The influence of the system compliance on fracture instability is discussed in conjunction with the latter application. The importance of using a J-resistance curve that is consistent with the type of constraint for a given application is emphasized. The possibility of a pipe fracture emanating from a stress corrosion crack in the heat-affected zones of girth-welds in Type 304 stainless steel pipes was investigated. The J-resistance curve was employed. A pipe fracture experiment was performed using a spring-loaded four-point bending system that simulated an 8.8-m long section of unsupported 102-mm-dia pipe. An initial through-wall crack of length equal to 104 mm was used. Fracture instability was predicted to occur between 15.2 and 22.1 mm of stable crack growth at each tip. In the actual experiment, the onset of fracture instability occurred beyond maximum load at an average stable crack growth of 11.7 to 19 mm at each tip. 24 refs.

  17. Plastic fracture mechanics prediction of fracture instability in a circumferentially cracked pipe in bending - 1. J-integral analysis

    International Nuclear Information System (INIS)

    Zahoor, A.; Kanninen, M.F.

    1981-01-01

    A method of evaluating the J-integral for a circumferentially cracked pipe in bending is proposed. The method allows a J-resistance curve to be evaluated directly from the load-displacement record obtained in a pipe fracture experiment. It permits an analysis for fracture instability in a circumferential crack growth using a J-resistance curve and the tearing modulus parameter. The influence of the system compliance on fracture instability is discussed in conjunction with the latter application. The importance of using a J-resistance curve that is consistent with the type of constraint for a given application is emphasized. The possibility of a pipe fracture emanating from a stress corrosion crack in the heat-affected zones of girth-welds in Type 304 stainless steel pipes was investigated. The J-resistance curve was employed. A pipe fracture experiment was performed using a spring-loaded four-point bending system that simulated an 8.8-m long section of unsupported 102-mm-dia pipe. An initial through-wall crack of length equal to 104 mm was used. Fracture instability was predicted to occur between 15.2 and 22.1 mm of stable crack growth at each tip. In the actual experiment, the onset of fracture instability occurred beyond maximum load at an average stable crack growth of 11.7 to 19 mm at each tip. 24 refs

  18. Mechanical test and fractal analysis on anisotropic fracture of cortical bone

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Dagang [State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044 (China); College of Aerospace Engineering, Chongqing University, Chongqing 400044 (China); Chen, Bin, E-mail: bchen@cqu.edu.cn [State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044 (China); College of Aerospace Engineering, Chongqing University, Chongqing 400044 (China); Ye, Wei [College of Aerospace Engineering, Chongqing University, Chongqing 400044 (China); Gou, Jihua [Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, FL 32816 (United States); Fan, Jinghong [Division of Mechanical Engineering, Alfred University, Alfred, NY 14802 (United States)

    2015-12-01

    Highlights: • The mechanical properties of the cortical bone of fresh bovine femora along three different directions are tested through four-point bending experiments. • SEM observation shows that the roughness of the fracture surfaces of the three different directions of the bone are remarkably different. • The fractal dimensions of the different fracture surfaces of the bone are calculated by box-counting method in MATLAB. • The fracture energies of the different fracture directions are calculated based on their fractal models. - Abstract: The mechanical properties of the cortical bone of fresh bovine femora along three different directions are tested through four-point bending experiments. It is indicated that the fracture energy along the transversal direction of the bone is distinctly larger than those of the longitudinal and radial directions. The fracture surfaces of the three different directions are observed by scanning electron microscope (SEM). It is shown that the roughness of the fracture surface of the transversal direction is obviously larger than those of the fracture surfaces of the longitudinal and radial directions. It is also revealed that the osteons in the bone are perpendicular to the fracture surface of the transversal direction and parallel to the fracture surfaces of the longitudinal and radial directions. Based on these experimental results, the fractal dimensions of the fracture surfaces of different directions are calculated by box-counting method in MATLAB. The calculated results show that the fractal dimension of the fracture surface of the transversal direction is remarkably larger than those of the fracture surfaces of the longitudinal and radial directions. The fracture energies of different directions are also calculated based on their fractal models. It is denoted that the fracture energy of the transversal direction is remarkably larger than those of the longitudinal and radial directions. The calculated results are in

  19. Mechanical test and fractal analysis on anisotropic fracture of cortical bone

    International Nuclear Information System (INIS)

    Yin, Dagang; Chen, Bin; Ye, Wei; Gou, Jihua; Fan, Jinghong

    2015-01-01

    Highlights: • The mechanical properties of the cortical bone of fresh bovine femora along three different directions are tested through four-point bending experiments. • SEM observation shows that the roughness of the fracture surfaces of the three different directions of the bone are remarkably different. • The fractal dimensions of the different fracture surfaces of the bone are calculated by box-counting method in MATLAB. • The fracture energies of the different fracture directions are calculated based on their fractal models. - Abstract: The mechanical properties of the cortical bone of fresh bovine femora along three different directions are tested through four-point bending experiments. It is indicated that the fracture energy along the transversal direction of the bone is distinctly larger than those of the longitudinal and radial directions. The fracture surfaces of the three different directions are observed by scanning electron microscope (SEM). It is shown that the roughness of the fracture surface of the transversal direction is obviously larger than those of the fracture surfaces of the longitudinal and radial directions. It is also revealed that the osteons in the bone are perpendicular to the fracture surface of the transversal direction and parallel to the fracture surfaces of the longitudinal and radial directions. Based on these experimental results, the fractal dimensions of the fracture surfaces of different directions are calculated by box-counting method in MATLAB. The calculated results show that the fractal dimension of the fracture surface of the transversal direction is remarkably larger than those of the fracture surfaces of the longitudinal and radial directions. The fracture energies of different directions are also calculated based on their fractal models. It is denoted that the fracture energy of the transversal direction is remarkably larger than those of the longitudinal and radial directions. The calculated results are in

  20. Fracture analysis

    International Nuclear Information System (INIS)

    Ueng, Tzoushin; Towse, D.

    1991-01-01

    Fractures are not only the weak planes of a rock mass, but also the easy passages for the fluid flow. Their spacing, orientation, and aperture will affect the deformability, strength, heat transmittal, and fluid transporting properties of the rock mass. To understand the thermomechanical and hydrological behaviors of the rock surrounding the heater emplacement borehole, the location, orientation, and aperture of the fractures of the rock mass should be known. Borehole television and borescope surveys were performed to map the location, orientation, and aperture of the fractures intersecting the boreholes drilled in the Prototype Engineered Barrier System Field Tests (PEBSFT) at G-Tunnel. Core logging was also performed during drilling. However, because the core was not oriented and the depth of the fracture cannot be accurately determined, the results of the core logging were only used as reference and will not be discussed here

  1. Thermo-mechanically coupled fracture analysis of shape memory alloys using the extended finite element method

    Science.gov (United States)

    Hatefi Ardakani, S.; Ahmadian, H.; Mohammadi, S.

    2015-04-01

    In this paper, the extended finite element method is used for fracture analysis of shape memory alloys for both cases of super elastic and shape memory effects. Heat generation during the forward and reverse phase transformations can lead to temperature variation in the material because of strong thermo-mechanical coupling, which significantly influences the SMA mechanical behavior. First, the stationary crack mode is studied and the effects of loading rate on material behavior in the crack tip are examined. Then, the crack propagation analysis is performed in the presence of an initial crack by adopting a weighted averaging criterion, where the direction of crack propagation is determined by weighted averaging of effective stresses at all the integration points in the vicinity of the crack tip. Finally, several numerical examples are analyzed and the obtained results are compared with the available reference results.

  2. Pressurized thermal shock probabilistic fracture mechanics sensitivity analysis for Yankee Rowe reactor pressure vessel

    International Nuclear Information System (INIS)

    Dickson, T.L.; Cheverton, R.D.; Bryson, J.W.; Bass, B.R.; Shum, D.K.M.; Keeney, J.A.

    1993-08-01

    The Nuclear Regulatory Commission (NRC) requested Oak Ridge National Laboratory (ORNL) to perform a pressurized-thermal-shock (PTS) probabilistic fracture mechanics (PFM) sensitivity analysis for the Yankee Rowe reactor pressure vessel, for the fluences corresponding to the end of operating cycle 22, using a specific small-break-loss- of-coolant transient as the loading condition. Regions of the vessel with distinguishing features were to be treated individually -- upper axial weld, lower axial weld, circumferential weld, upper plate spot welds, upper plate regions between the spot welds, lower plate spot welds, and the lower plate regions between the spot welds. The fracture analysis methods used in the analysis of through-clad surface flaws were those contained in the established OCA-P computer code, which was developed during the Integrated Pressurized Thermal Shock (IPTS) Program. The NRC request specified that the OCA-P code be enhanced for this study to also calculate the conditional probabilities of failure for subclad flaws and embedded flaws. The results of this sensitivity analysis provide the NRC with (1) data that could be used to assess the relative influence of a number of key input parameters in the Yankee Rowe PTS analysis and (2) data that can be used for readily determining the probability of vessel failure once a more accurate indication of vessel embrittlement becomes available. This report is designated as HSST report No. 117

  3. Plastic fracture mechanics prediction of fracture instability in a circumferentially cracked pipe in bending--1. J-integral analysis

    International Nuclear Information System (INIS)

    Zahoor, A.; Kanninen, M.F.

    1980-01-01

    A method of evaluating the J-integral for a circumferentially cracked pipe in bending is proposed. The method allows a J-resistance curve to be evaluated directly from the load-displacement record obtained in a pipe fracture experiment. This method also permits an analysis for fracture instability in a circumferential crack growth using a J-resistance curve and the tearing modulus parameter. The importance of using a J-resistance curve that is consistent with the type of constraint for a given application is emphasized. 18 refs

  4. User's manuals of probabilistic fracture mechanics analysis code for aged piping, PASCAL-SP

    International Nuclear Information System (INIS)

    Itoh, Hiroto; Nishikawa, Hiroyuki; Onizawa, Kunio; Kato, Daisuke; Osakabe, Kazuya

    2010-03-01

    As a part of research on the material degradation and structural integrity assessment for aged LWR components, a PFM (Probabilistic Fracture Mechanics) analysis code PASCAL-SP (PFM Analysis of Structural Components in Aging LWR - Stress Corrosion Cracking at Welded Joints of Piping) has been developed. This code evaluates the failure probabilities at welded joints of aged piping by a Monte Carlo method. PASCAL-SP treats stress corrosion cracking (SCC) and fatigue crack growth in piping, according to the approaches of NISA and JSME FFS Code. The development of the code has been aimed to improve the accuracy and reliability of analysis by introducing new analysis methodologies and algorithms considering the latest knowledge in the SCC assessment and fracture criteria of piping. In addition, the accuracy of flaw detection and sizing at in-service inspection and residual stress distribution were modeled based on experimental data and introduced into PASCAL-SP. This code has been developed for a cross-check use by the regulatory body in Japan. In addition to this, this code can also be used for a research purpose by researchers in academia and industries. This report provides the user's manual and theoretical background of the code. (author)

  5. Analysis and modeling of coupled thermo-hydro-mechanical phenomena in 3D fractured media

    International Nuclear Information System (INIS)

    Canamon Valera, I.

    2006-11-01

    This doctoral research was conducted as part of a joint France-Spain co-tutelage PhD thesis in the framework of a bilateral agreement between two universities, the Institut National Polytechnique de Toulouse (INPT) and the Universidad Politecnica de Madrid (UPM). It concerns a problem of common interest at the national and international levels, namely, the disposal of radioactive waste in deep geological repositories. The present work is devoted, more precisely, to near-field hydrogeological aspects involving mass and heat transport phenomena. The first part of the work is devoted to a specific data interpretation problem (pressures, relative humidities, temperatures) in a multi-barrier experimental system at the scale of a few meters - the 'Mock-Up Test' of the FEBEX project, conducted in Spain. Over 500 time series are characterized in terms of spatial, temporal, and/or frequency/scale-based statistical analysis techniques. The time evolution and coupling of physical phenomena during the experiment are analyzed, and conclusions are drawn concerning the behavior and reliability of the sensors. The second part of the thesis develops in more detail the 3-Dimensional (3D) modeling of coupled Thermo-Hydro-Mechanical phenomena in a fractured porous rock, this time at the scale of a hundred meters, based on the data of the 'In-Situ Test' of the FEBEX project conducted at the Grimsel Test Site in the Swiss Alps. As a first step, a reconstruction of the 3D fracture network is obtained by Monte Carlo simulation, taking into account through optimization the geomorphological data collected around the FEBEX gallery. The heterogeneous distribution of traces observed on the cylindrical wall of the tunnel is fairly well reproduced in the simulated network. In a second step, we develop a method to estimate the equivalent permeability of a many-fractured block by extending the superposition method of Ababou et al. [1994] to the case where the permeability of the rock matrix is not

  6. Mechanics of Hydraulic Fractures

    Science.gov (United States)

    Detournay, Emmanuel

    2016-01-01

    Hydraulic fractures represent a particular class of tensile fractures that propagate in solid media under pre-existing compressive stresses as a result of internal pressurization by an injected viscous fluid. The main application of engineered hydraulic fractures is the stimulation of oil and gas wells to increase production. Several physical processes affect the propagation of these fractures, including the flow of viscous fluid, creation of solid surfaces, and leak-off of fracturing fluid. The interplay and the competition between these processes lead to multiple length scales and timescales in the system, which reveal the shifting influence of the far-field stress, viscous dissipation, fracture energy, and leak-off as the fracture propagates.

  7. PASCAL, Probabilistic Fracture Mechanics Analysis of Structural Components in Aging LWR

    International Nuclear Information System (INIS)

    Shibata, Katsuyuki; Onizawa, Kunio; Li, Yinsheng; Kato, Daisuke

    2005-01-01

    A - Description of program or function: PASCAL (PFM analysis of Structural Components in Aging LWR) is a PFM (Probabilistic Fracture Mechanics) code for evaluating the failure probability of aged pressure components. PASCAL has been developed as a part of the JAERI's research program on aging and structural integrity of LWR components, in order to respond to the increasing need of the probabilistic methodology in the regulation and inspection of nuclear components with the objective to provide a rational tool for the evaluation of the reliability and integrity of structural components. In order to improve the accuracy and reliability of the analysis code, some new fracture mechanics models or computational techniques are introduced considering the recent progress in the state of the art and performance of PC. Thus some new analysis models and original methodologies were introduced in PASCAL such as the elastic-plastic fracture criterion based on R6 method, a new crack extension model of semi-elliptical crack evaluation and so on. Moreover a function to evaluate the effect of embrittlement recovery by annealing of irradiated RPV is also introduced in the code based on the USNRC R.G. 1.162(1996). The code has been verified through various failure analysis results and international PTS round robin analysis ICAS which had been organized by the Principal Working Group 3 of OECD/NEA/CSNI. In order to attain a high usability, PASCAL Ver.1 with GUI provides an exclusive FEM pre-processor Pre-PASCAL for generating the input load transient data, a GUI system for generating the input data for PASCAL main processor of main solver and post-processor for output data. - Pre-PASCAL: Pre-PASCAL is an exclusive 3-D FEM pre-processor for generating the input transient data provided with 3 RPV mesh models and two simple specimen mesh models, i.e. CT and CCP. Almost the same input data format with that of PASCAL main processor is used. Output data of temperature and stress distribution

  8. Problems and chances for probabilistic fracture mechanics in the analysis of steel pressure boundary reliability

    Energy Technology Data Exchange (ETDEWEB)

    Staat, M [Forschungszentrum Juelich GmbH (Germany). Inst. fuer Sicherheitsforschung und Reaktortechnik

    1996-12-01

    It is shown that the difficulty for probabilistic fracture mechanics (PFM) is the general problem of the high reliability of a small population. There is no way around the problem as yet. Therefore what PFM can contribute to the reliability of steel pressure boundaries is demonstrated with the example of a typical reactor pressure vessel and critically discussed. Although no method is distinguishable that could give exact failure probabilities, PFM has several additional chances. Upper limits for failure probability may be obtained together with trends for design and operating conditions. Further, PFM can identify the most sensitive parameters, improved control of which would increase reliability. Thus PFM should play a vital role in the analysis of steel pressure boundaries despite all shortcomings. (author). 19 refs, 7 figs, 1 tab.

  9. Problems and chances for probabilistic fracture mechanics in the analysis of steel pressure boundary reliability

    International Nuclear Information System (INIS)

    Staat, M.

    1996-01-01

    It is shown that the difficulty for probabilistic fracture mechanics (PFM) is the general problem of the high reliability of a small population. There is no way around the problem as yet. Therefore what PFM can contribute to the reliability of steel pressure boundaries is demonstrated with the example of a typical reactor pressure vessel and critically discussed. Although no method is distinguishable that could give exact failure probabilities, PFM has several additional chances. Upper limits for failure probability may be obtained together with trends for design and operating conditions. Further, PFM can identify the most sensitive parameters, improved control of which would increase reliability. Thus PFM should play a vital role in the analysis of steel pressure boundaries despite all shortcomings. (author). 19 refs, 7 figs, 1 tab

  10. A Rock Mechanics and Coupled Hydro mechanical Analysis of Geological Repository of High Level Nuclear Waste in Fractured Rocks

    International Nuclear Information System (INIS)

    Min, Kibok

    2011-01-01

    This paper introduces a few case studies on fractured hard rock based on geological data from Sweden, Korea is one of a few countries where crystalline rock is the most promising rock formation as a candidate site of geological repository of high level nuclear waste. Despite the progress made in the area of rock mechanics and coupled hydro mechanics, extensive site specific study on multiple candidate sites is essential in order to choose the optimal site. For many countries concerned about the safe isolation of nuclear wastes from the biosphere, disposal in a deep geological formation is considered an attractive option. In geological repository, thermal loading continuously disturbs the repository system in addition to disturbances a recent development in rock mechanics and coupled hydro mechanical study using DFN(Discrete Fracture Network) - DEM(Discrete Element Method) approach mainly applied in hard, crystalline rock containing numerous fracture which are main sources of deformation and groundwater flow

  11. Fracture mechanical analysis of tungsten armor failure of a water-cooled divertor target

    Energy Technology Data Exchange (ETDEWEB)

    Li, Muyuan; Werner, Ewald [Lehrstuhl für Werkstoffkunde und Werkstoffmechanik, Technische Universität München, Boltzmannstr. 15, 85748 Garching (Germany); You, Jeong-Ha, E-mail: you@ipp.mpg.de [Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching (Germany)

    2014-11-15

    Highlights: • The FEM-based VCE method and XFEM were employed for computing K{sub I} (or J-integral) and predicting progressive cracking, respectively. • The most probable pattern of crack formation is radial cracking in the tungsten armor block. • The most probable site of cracking is the upper interfacial region of the tungsten armor block adjacent to the top position of the copper interlayer. • The initiation of a major crack becomes likely, only when the strength of tungsten armor block is significantly reduced from its original strength. - Abstract: The inherent brittleness of tungsten at low temperature and the embrittlement by neutron irradiation are its most critical weaknesses for fusion applications. In the current design of the ITER and DEMO divertor, the high heat flux loads during the operation impose a strong constraint on the structure–mechanical performance of the divertor. Thus, the combination of brittleness and the thermally induced stress fields due to the high heat flux loads raises a serious reliability issue in terms of the structural integrity of tungsten armor. In this study, quantitative estimates of the vulnerability of the tungsten monoblock armor cracking under stationary high heat flux loads are presented. A comparative fracture mechanical investigation has been carried out by means of two different types of computational approaches, namely, the extended finite element method (XFEM) and the finite element method (FEM)-based virtual crack tip extension (VCE) method. The fracture analysis indicates that the most probable pattern of crack formation is radial cracking in the tungsten armor starting from the interface to tube and the most probable site of cracking is the upper interfacial region of the tungsten armor adjacent to the top position of the copper interlayer. The strength threshold for crack initiation and the high heat flux load threshold for crack propagation are evaluated based on XFEM simulations and computations

  12. Fracture mechanics of piezoelectric and ferroelectric solids

    CERN Document Server

    Fang, Daining

    2013-01-01

    Fracture Mechanics of Piezoelectric and Ferroelectric Solids presents a systematic and comprehensive coverage of the fracture mechanics of piezoelectric/ferroelectric materials, which includes the theoretical analysis, numerical computations and experimental observations. The main emphasis is placed on the mechanics description of various crack problems such static, dynamic and interface fractures as well as the physical explanations for the mechanism of electrically induced fracture. The book is intended for postgraduate students, researchers and engineers in the fields of solid mechanics, applied physics, material science and mechanical engineering. Dr. Daining Fang is a professor at the School of Aerospace, Tsinghua University, China; Dr. Jinxi Liu is a professor at the Department of Engineering Mechanics, Shijiazhuang Railway Institute, China.

  13. Probabilistic fracture mechanics analysis for the life extension estimate of the high flux isotope reactor vessel

    International Nuclear Information System (INIS)

    Chang, S.J.

    1997-01-01

    The state of the vessel steel embrittlement as a result of neutron irradiation can be measured by its increase in the nil ductility temperature (NDT). This temperature is sometimes referred to as the brittle-ductile transition temperature (DBT) for fracture. The life extension of the High Flux Isotope Reactor (HFIR) vessel is calculated by using the method of fracture mechanics. A new method of fracture probability calculation is presented in this paper. The fracture probability as a result of the hydrostatic pressure test (hydrotest) is used to determine the life of the vessel. The hydrotest is performed in order to determine a safe vessel static pressure. It is then followed by using fracture mechanics to project the safe reactor operation time from the time of the satisfactory hydrostatic test. The life extension calculation provides the following information on the remaining life of the reactor as a function of the NDT increase: (1) the life of the vessel is determined by the probability of vessel fracture as a result of hydrotest at several hydrotest pressures and vessel embrittlement conditions, (2) the hydrotest time interval vs the NDT increase rate, and (3) the hydrotest pressure vs the NDT increase rate. It is understood that the use of a complete range of uncertainties of the NDT increase is equivalent to the entire range of radiation damage that can be experienced by the vessel steel. From the numerical values for the probabilities of the vessel fracture as a result of hydrotest, it is estimated that the reactor vessel life can be extended up to 50 EFPY (100 MW) with the minimum vessel operating temperature equal to 85 degrees F

  14. Continuum Damage Mechanics A Continuum Mechanics Approach to the Analysis of Damage and Fracture

    CERN Document Server

    Murakami, Sumio

    2012-01-01

    Recent developments in engineering and technology have brought about serious and enlarged demands for reliability, safety and economy in wide range of fields such as aeronautics, nuclear engineering, civil and structural engineering, automotive and production industry.  This, in turn, has caused more interest in continuum damage mechanics and its engineering applications.   This book aims to give a concise overview of the current state of damage mechanics, and then to show the fascinating possibility of this promising branch of mechanics, and to provide researchers, engineers and graduate students with an intelligible and self-contained textbook.   The book consists of two parts and an appendix.  Part I  is concerned with the foundation of continuum damage mechanics.  Basic concepts of material damage and the mechanical representation of damage state of various kinds are described in Chapters 1 and 2.  In Chapters 3-5, irreversible thermodynamics, thermodynamic constitutive theory and its application ...

  15. Mechanical properties of fracture zones

    International Nuclear Information System (INIS)

    Leijon, B.

    1993-05-01

    Available data on mechanical characteristics of fracture zones are compiled and discussed. The aim is to improve the basis for adequate representation of fracture zones in geomechanical models. The sources of data researched are primarily borehole investigations and case studies in rock engineering, involving observations of fracture zones subjected to artificial load change. Boreholes only yield local information about the components of fracture zones, i.e. intact rock, fractures and various low-strength materials. Difficulties are therefore encountered in evaluating morphological and mechanical properties of fracture zones from borehole data. Although often thought of as macroscopically planar features, available field data consistently show that fracture zones are characterized by geometrical irregularities such as thickness variations, surface undulation and jogs. These irregularities prevail on all scales. As a result, fracture zones are on all scales characterized by large, in-plane variation of strength- and deformational properties. This has important mechanical consequences in terms of non-uniform stress transfer and complex mechanisms of shear deformation. Field evidence for these findings, in particular results from the underground research laboratory in Canada and from studies of induced fault slip in deep mines, is summarized and discussed. 79 refs

  16. FRACTURE MECHANICS UNCERTAINTY ANALYSIS IN THE RELIABILITY ASSESSMENT OF THE REACTOR PRESSURE VESSEL: (2D SUBJECTED TO INTERNAL PRESSURE

    Directory of Open Access Journals (Sweden)

    Entin Hartini

    2016-06-01

    Full Text Available ABSTRACT FRACTURE MECHANICS UNCERTAINTY ANALYSIS IN THE RELIABILITY ASSESSMENT OF THE REACTOR PRESSURE VESSEL: (2D SUBJECTED TO INTERNAL PRESSURE. The reactor pressure vessel (RPV is a pressure boundary in the PWR type reactor which serves to confine radioactive material during chain reaction process. The integrity of the RPV must be guaranteed either  in a normal operation or accident conditions. In analyzing the integrity of RPV, especially related to the crack behavior which can introduce break to the reactor pressure vessel, a fracture mechanic approach should be taken for this assessment. The uncertainty of input used in the assessment, such as mechanical properties and physical environment, becomes a reason that the assessment is not sufficient if it is perfomed only by deterministic approach. Therefore, the uncertainty approach should be applied. The aim of this study is to analize the uncertainty of fracture mechanics calculations in evaluating the reliability of PWR`s reactor pressure vessel. Random character of input quantity was generated using probabilistic principles and theories. Fracture mechanics analysis is solved by Finite Element Method (FEM with  MSC MARC software, while uncertainty input analysis is done based on probability density function with Latin Hypercube Sampling (LHS using python script. The output of MSC MARC is a J-integral value, which is converted into stress intensity factor for evaluating the reliability of RPV’s 2D. From the result of the calculation, it can be concluded that the SIF from  probabilistic method, reached the limit value of  fracture toughness earlier than SIF from  deterministic method.  The SIF generated by the probabilistic method is 105.240 MPa m0.5. Meanwhile, the SIF generated by deterministic method is 100.876 MPa m0.5. Keywords: Uncertainty analysis, fracture mechanics, LHS, FEM, reactor pressure vessels   ABSTRAK ANALISIS KETIDAKPASTIAN FRACTURE MECHANIC PADA EVALUASI KEANDALAN

  17. Fracture mechanics and residual fatigue life analysis for complex stress fields. Technical report

    International Nuclear Information System (INIS)

    Besuner, P.M.

    1975-07-01

    This report reviews the development and application of an influence function method for calculating stress intensity factors and residual fatigue life for two- and three-dimensional structures with complex stress fields and geometries. Through elastic superposition, the method properly accounts for redistribution of stress as the crack grows through the structure. The analytical methods used and the computer programs necessary for computation and application of load independent influence functions are presented. A new exact solution is obtained for the buried elliptical crack, under an arbitrary Mode I stress field, for stress intensity factors at four positions around the crack front. The IF method is then applied to two fracture mechanics problems with complex stress fields and geometries. These problems are of current interest to the electric power generating industry and include (1) the fatigue analysis of a crack in a pipe weld under nominal and residual stresses and (2) fatigue analysis of a reactor pressure vessel nozzle corner crack under a complex bivariate stress field

  18. Fracture mechanics analysis and evaluation for the RPV of the Chinese Qinshan 300 MW NPP and PTS

    International Nuclear Information System (INIS)

    He Yinbiao; Isozaki, Toshikuni

    2000-03-01

    One of the most severe accident conditions of a reactor pressure vessel (RPV) in service is the loss of coolant accident (LOCA). Cold safety injection water is pumped into the downcomer of the RPV through inlet nozzles, while the internal pressure may remain at high level. Such an accident is called pressurized thermal shock (PTS) transient according to 10 CFR 50.61 definition. This paper illustrates the fracture mechanics analysis for the existing RPV of the Chinese Qinshan 300 MW nuclear power plant (NPP) under the postulated PTS transients that include SB-LOCA, LB-LOCA of Qinshan NPP and Rancho Seco transients. 3-D models with the flaw depth range a/w=0.05∼0.9 (a: flaw depth; w: wall thickness) were used to probe what kind of flaw and what kind of transient are most dangerous for the RPV in the end of life (EOF). Both the elastic and elastic-plastic material models were used in the stress analysis and fracture mechanics analysis. The different types of flaw and the influence of the stainless steel cladding on the fracture analysis were investigated for different PTS transients. comparing with the material initiation crack toughness K IC , the fracture evaluation for the RPV in question under PTS transients are performed in this paper. (author)

  19. Theoretical aspects of fracture mechanics

    Science.gov (United States)

    Atkinson, C.; Craster, R. V.

    1995-03-01

    In this review we try to cover various topics in fracture mechanics in which mathematical analysis can be used both to aid numerical methods and cast light on key features of the stress field. The dominant singular near crack tip stress field can often be parametrized in terms of three parameters K(sub I), K(sub II) and K(sub III) designating three fracture modes each having an angular variation entirely specified for the stress tensor and displacement vector. These results and contact zone models for removing the interpenetration anomaly are described. Generalizations of the above results to viscoelastic media are described. For homogeneous media with constant Poisson's ratio the angular variation of singular crack tip stresses and displacements are shown to be the same for all time and the same inverse square root singularity as occurs in the elastic medium case is found (this being true for a time varying Poisson ratio too). Only the stress intensity factor varies through time dependence of loads and relaxation properties of the medium. For cracks against bimaterial interfaces both the stress singularity and angular form evolve with time as a function of the time dependent properties of the bimaterial. Similar behavior is identified for sharp notches in viscoelastic plates. The near crack tip behavior in material with non-linear stress strain laws is also identified and stress singularities classified in terms of the hardening exponent for power law hardening materials. Again for interface cracks the near crack tip behavior requires careful analysis and it is shown that more than one singular term may be present in the near crack tip stress field. A variety of theory and applications is presented for inhomogeneous elastic media, coupled thermoelasticity etc. Methods based on reciprocal theorems and dual functions which can also aid in getting awkward singular stress behavior from numerical solutions are also reviewed. Finally theoretical calculations of fiber

  20. Mechanical Property Measurements and Fracture Propagation Analysis of Longmaxi Shale by Micro-CT Uniaxial Compression

    Directory of Open Access Journals (Sweden)

    Minyue Zhou

    2018-05-01

    Full Text Available The mechanical properties and fracture propagation of Longmaxi shale loading under uniaxial compression were measured using eight cylindrical shale specimens (4 mm in diameter and 8 mm in height, with the bedding plane oriented at 0° and 90° to the axial loading direction, respectively, by micro computed tomography (micro-CT. Based on the reconstructed three-dimensional (3-D CT images of cracks, different stages of the crack growth process in the 0° and 90° orientation specimen were revealed. The initial crack generally occurred at relatively smaller loading force in the 0° bedding direction specimen, mainly in the form of tensile splitting along weak bedding planes. Shear sliding fractures were dominant in the specimens oriented at 90°, with a small number of parallel cracks occurring on the bedding plane. The average thickness and volume of cracks in the 90° specimen is higher than those for the specimen oriented at 0°. The geometrical characterization of fractures segmented from CT scan binary images shows that a specific surface area correlates with tortuosity at the different load stages of each specimen. The 3-D box-counting dimension (BCD calculations can accurately reflect crack evolution law in the shale. The results indicate that the cracks have a more complex pattern and rough surface at an orientation of 90°, due to crossed secondary cracks and shear failure.

  1. Probabilistic fracture mechanics analysis for leak-before-break evaluation of light water reactor's piping

    International Nuclear Information System (INIS)

    Yoshimura, Shinobu; Yagawa, Genki; Akiba, Hiroshi; Fujioka, Terutaka.

    1997-01-01

    This paper describes Probabilistic Fracture Mechanics (PFM) analyses for quantitative evaluation of the likelihood of Leak-Before-Break (LBB) of Light Water Reactor's (LWR's) piping. The PFM analyses in general assume probabilistic distributions of initial crack size, applied stress cycles, crack growth laws, fracture criteria, leakage detection capability, defect inspection capability and so on. Referring to the deterministic procedure for LBB evaluation, most appropriate PFM models and data for LBB evaluation are discussed. Here the LBB index is newly proposed in order to quantitatively evaluate the likelihood of LBB. Through intensive sensitivity analyses, it is clarified that the LBB is more likely to occur for larger diameter pipe; the performance of leakage detection significantly affects the LBB likelihood; the LBB likelihood increases with plant's aging even conservatively assuming leak detection capability; the R6 method (Category 1, Option 1) for fracture criterion gives very conservative results; and In-Service Inspection (ISI) reduces the increase rate of failure probability than the failure probability itself. (author)

  2. Application of probabilistic fracture mechanics to the reliability analysis of pressure-bearing reactor components

    International Nuclear Information System (INIS)

    Schmitt, W.; Roehrich, E.; Wellein, R.

    1977-01-01

    Since no failures in the primary reactor components have been reported so far, it is impossible to estimate the failure probability of those components just by means of statistics. Therefore the way of probabilistic fracture mechanics has been proposed. Here the material properties, the loads and the crack distributions are treated as statistical variables with certain distributions. From the distributions of these data probability density functions can be established for the loading of a component (e.g. the stress intensity factor) as well as for the resistance of this component (e.g. the fracture toughness). From these functions the failure probability for a given failure mode (e.g. brittle fracture) is easily obtained either by the application of direct integration procedures which are shortly reviewed here, or by the use of Monte Carlo techniques. The most important part of the concept is the collection of a sufficiently large amount of raw data from different sources (departments within the company or external). These data need to be processed so that they can be transformed into probability density functions. The method of data collection and processing in terms of histograms, plots of probability density functions etc, is described. The choice of the various types of distribution functions is discussed. As an example the derivation of the probability density function for cracks of a given size in a component is presented. (Auth.)

  3. Development of Deterministic and Probabilistic Fracture Mechanics Analysis Code PROFAS-RV for Reactor Pressure Vessel - Progress of the Work

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jong Min; Lee, Bong Sang [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    In this study, a deterministic/probabilistic fracture mechanics analysis program for reactor pressure vessel, PROFAS-RV, is developed. This program can evaluate failure probability of RPV using recent radiation embrittlement model of 10CFR50.61a and stress intensity factor calculation method of RCC-MRx code as well as the required basic functions of PFM program. Applications of some new radiation embrittlement model, material database, calculation method of stress intensity factors, and others which can improve fracture mechanics assessment of RPV are introduced. The purpose of this study is to develop a probabilistic fracture mechanics (PFM) analysis program for RPV considering above modification and application of newly developed models and calculation methods. In this paper, it deals with the development progress of the PFM analysis program for RPV, PROFAS-RV. The PROFAS-RV is being tested with other codes, and it is expected to revise and upgrade by reflecting the latest model and calculation method continuously. These efforts can minimize the uncertainty of the integrity evaluation for the reactor pressure vessel.

  4. Fracture mechanical analysis of relevant transients in the pressure vessel of Atucha I reactor

    International Nuclear Information System (INIS)

    Saavedra, Fernando M.

    2001-01-01

    The evolution of the applied stress intensity factor K I for 10 relevant transients of the nuclear power station Atucha I obtained from thermohydraulic data is analyzed according to the methodology proposed in Section XI of ASME Boiler and Pressure Vessel Code. Vast knowledge was thus obtained about basic concepts of fracture mechanics and its application to remanent life of nuclear components. Basic knowledge which commands the performance of nuclear power stations was also obtained, especially that related to the Atucha I utility [es

  5. Probabilistic application of fracture mechanics

    International Nuclear Information System (INIS)

    Dufresne, J.

    1981-04-01

    The different methods used to evaluate the rupture probability of a pressure vessel are reviewed. Data collection and processing of all parameters necessary for fracture mechanics evaluation are presented with particular attention to the size distribution of defects in actual vessels. Physical process is followed during crack growth and unstable propagation, using LEFM (Linear Elastic Fracture Mechanism) and plastic instability. Results show that the final failure probability for a PWR pressure vessel is 3.5 10 -8 , and is due essentially to LOCAs for any break size. The weakest point is the internal side of the belt line

  6. A New Approach to the Modeling and Analysis of Fracture through Extension of Continuum Mechanics to the Nanoscale

    KAUST Repository

    Sendova, T.

    2010-02-15

    In this paper we focus on the analysis of the partial differential equations arising from a new approach to modeling brittle fracture based on an extension of continuum mechanics to the nanoscale. It is shown that ascribing constant surface tension to the fracture surfaces and using the appropriate crack surface boundary condition given by the jump momentum balance leads to a sharp crack opening profile at the crack tip but predicts logarithmically singular crack tip stress. However, a modified model, where the surface excess property is responsive to the curvature of the fracture surfaces, yields bounded stresses and a cusp-like opening profile at the crack tip. Further, two possible fracture criteria in the context of the new theory are discussed. The first is an energy-based crack growth condition, while the second employs the finite crack tip stress the model predicts. The classical notion of energy release rate is based upon the singular solution, whereas for the modeling approach adopted here, a notion analogous to the energy release rate arises through a different mechanism associated with the rate of working of the surface excess properties at the crack tip. © The Author(s), 2010.

  7. Fracture mechanics model of fragmentation

    International Nuclear Information System (INIS)

    Glenn, L.A.; Gommerstadt, B.Y.; Chudnovsky, A.

    1986-01-01

    A model of the fragmentation process is developed, based on the theory of linear elastic fracture mechanics, which predicts the average fragment size as a function of strain rate and material properties. This approach permits a unification of previous results, yielding Griffith's solution in the low-strain-rate limit and Grady's solution at high strain rates

  8. Effect of interfragmentary gap on the mechanical behavior of mandibular angle fracture with three fixation designs: A finite element analysis.

    Science.gov (United States)

    Wang, Russell; Liu, Yunfeng; Wang, Joanne Helen; Baur, Dale Allen

    2017-03-01

    The aim of this study was to simulate stress and strain distribution numerically on a normal mandible under physiological occlusal loadings. The results were compared with those of mandibles that had an angle fracture stabilized with different fixation designs under the same loadings. The amount of displacement at two interfragmentary gaps was also studied. A three-dimensional (3D) virtual mandible was reconstructed with an angle fracture that had a fracture gap of either 0.1 or 1 mm. Three types of plate fixation designs were used: Type I, a miniplate was placed across the fracture line following the Champy technique; Type II, two miniplates were used; and Type III, a reconstruction plate was used on the inferior border of the mandible. Loads of 100 and 500 N were applied to the models. The maximum von Mises stress, strain, and displacement were computed using finite element analysis. The results from the control and experimental groups were analyzed and compared. The results demonstrated that high stresses and strains were distributed to the condylar and angular areas regardless of the loading position. The ratio of the plate/bone average stress ranged from 215% (Type II design) to 848% (Type I design) irrespective of the interfragmentary gap size. With a 1-mm fracture gap, the ratio of the plate/bone stress ranged from 204% (Type II design) to 1130% (Type I design). All strains were well below critical bone strain thresholds. Displacement on the cross-sectional mapping at fracture interface indicated that uneven movement occurred in x, y, and z directions. Interfragmentary gaps between 0.1 and 1 mm did not have a substantial effect on the average stress distribution to the fractured bony segments; however, they had a greater effect on the stress distribution to the plates and screws. Type II fixation was the best mechanical design under bite loads. Type I design was the least stable system and had the highest stress distribution and the largest displacement

  9. Probabilistic safety analysis vs probabilistic fracture mechanics -relation and necessary merging

    International Nuclear Information System (INIS)

    Nilsson, Fred

    1997-01-01

    A comparison is made between some general features of probabilistic fracture mechanics (PFM) and probabilistic safety assessment (PSA) in its standard form. We conclude that: Result from PSA is a numerically expressed level of confidence in the system based on the state of current knowledge. It is thus not any objective measure of risk. It is important to carefully define the precise nature of the probabilistic statement and relate it to a well defined situation. Standardisation of PFM methods is necessary. PFM seems to be the only way to obtain estimates of the pipe break probability. Service statistics are of doubtful value because of scarcity of data and statistical inhomogeneity. Collection of service data should be directed towards the occurrence of growing cracks

  10. Fracture mechanics of ceramics. Vol. 7

    International Nuclear Information System (INIS)

    Bradt, R.C.; Evans, A.G.; Hasselman, D.P.; Lange, F.F.

    1986-01-01

    This volume, together with volume 8, constitutes the proceedings of an international symposium on the fracture mechanics of ceramics. The topics discussed in this volume include the toughening of ceramics by whisker reinforcement; the mechanical properties of SiCwhisker-reinforced TZP; the fracture of brittle rock and oil shale under dynamic explosive loading; impact damage models of ceramic coatings used in gas turbine and diesel engines; the use of exploratory data analysis for the safety evaluation of structural ceramics; and proof testing methods for the reliability of structural ceramics used in gas turbines

  11. Comparison between Visa-II and OCA-P for probabilistic fracture mechanics analysis focusing on analysis method

    International Nuclear Information System (INIS)

    Hirano, M.; Watanabe, N.; Tatewaki, I.; Akiba, H.

    1995-01-01

    Probabilistic fracture mechanics (PFM) analyses have been widely applied to evaluate the failure probabilities of PWR reactor pressure vessels subjected to pressurized thermal shock. In this study, a comparison between the VISA-II and OCA-P codes for PFM analyses was performed to clarify the differences in the numerical processes. For this purpose, the benchmark problems proposed by the U.S. Nuclear Regulatory Commission and the Electric Power Research Institute were applied. It is also discussed the algorithm to evaluate the deviations from the means of RT NDT and fracture toughness, and the numerical treatment of initial flaw depth as the major differences in these codes. 4 refs., 9 figs

  12. Fracture mechanics. With an introduction to micromechanics

    International Nuclear Information System (INIS)

    Gross, D.

    2006-01-01

    Concerned with the fundamental concepts and methods of fracture mechanics and micromechanics, Fracture Mechanics primarily focuses on the mechanical description of the fracture process; however, material specific aspects are also discussed. The presentation of continuum mechanical and phenomenological foundations is followed by an introduction into classical failure hypotheses. A major part of the book is devoted to linear elastic and elastic-plastic fracture mechanics. Further subjects are creep fracture, dynamic fracture mechanics, damage mechanics, probabilistic fracture mechanics, failure of thin films and fracture of piezoelectric materials. The book also contains an extensive introduction into micromechanics. Self-contained and well-illustrated, this text serves as a graduate-level text and reference

  13. A fracture mechanics analysis of bonded repaired skin/stiffener structures with inclined central crack

    International Nuclear Information System (INIS)

    Chung, Ki Hyun; Yang, Won Ho; Kim, Cheol; Heo, Sung Pil; Ko, Myung Hoon

    2001-01-01

    Composite patch repair of cracked aircraft structures has been accepted as one of improving fatigue life and attaining better structural integrity. Analysis for the stress intensity factor at the skin/stiffener structure with inclined central crack repaired by composite stiffened panels are developed. A numerical investigation was conducted to characterize the fracture behavior and crack growth behavior. In order to investigate the crack growth direction, Maximum Tangential Stress(MTS) criteria is used. The main objective of this research is the validation of the inclined crack patching design. In this paper, the reduction of stresses intensity factors at the crack-tip and prediction of crack growth direction are determined to evaluate the effects of various non-dimensional design parameter including; composite patch thickness and stiffener distance. The research on cracked structure subjected to mixed mode loading is accomplished and it is evident that more work using different approaches is necessary

  14. Model of T-Type Fracture in Coal Fracturing and Analysis of Influence Factors of Fracture Morphology

    Directory of Open Access Journals (Sweden)

    Yuwei Li

    2018-05-01

    Full Text Available Special T-type fractures can be formed when coal is hydraulically fractured and there is currently no relevant theoretical model to calculate and describe them. This paper first establishes the height calculation model of vertical fractures in multi-layered formations and deduces the stress intensity factor (SIF at the upper and lower sides of the fracture in the process of vertical fracture extension. Combined with the fracture tip stress analysis method of fracture mechanics theory, the horizontal bedding is taken into account for tensile and shear failure, and the critical mechanical conditions for the formation of horizontal fracture in coal are obtained. Finally, the model of T-type fracture in coal fracturing is established, and it is verified by fracturing simulation experiments. The model calculation result shows that the increase of vertical fracture height facilitates the increase of horizontal fracture length. The fracture toughness of coal has a significant influence on the length of horizontal fracture and there is a threshold. When the fracture toughness is less than the threshold, the length of horizontal fracture remains unchanged, otherwise, the length of horizontal fracture increases rapidly with the increase of fracture toughness. When the shear strength of the interface between the coalbed and the interlayer increases, the length of the horizontal fracture of the T-type fracture rapidly decreases.

  15. Application of probabilistic fracture mechanics to the reliability analysis of pressure-bearing reactor components

    International Nuclear Information System (INIS)

    Schmitt, W.; Roehrich, E.; Wellein, R.

    1977-01-01

    Since no failures in the primary reactor components have been reported so far, it is impossible to estimate the failure probability of those components just by means of statistics. Therefore the way of probabilistic fracture mechanics has been proposed. Here the material properties, the loads and the crack distributions are treated as statistical variables with certain distributions. From the distributions of these data probability density functions can be established for the loading of a component as well as for the resistance of this component. From these functions the failure probability for a given failure mode is easily obtained either by the application of direct integration procedures which are shortly reviewed here, or by the use of Monte Carlo techniques. The most important part of the concept is the collection of a sufficiently large amount of raw data from different sources. These data need to be processed so that they can be transformed into probability density functions. The method of data collection and processing in terms of histograms, plots of probability density functions etc. is described. The choice of the various types of distribution functions is discussed. As an example, the derivation of the probability density function for cracks of a given size in a component is presented. Here the raw data, i.e. the ultrasonic results, are transformed into real crack sizes by means of a conservative conversion rule. The true distribution of the indications is obtained by taking into account a detection probability function. The final probability density function is influenced by the fact that indications exceeding certain values need to be re

  16. Probabilistic fracture mechanics analysis of boiling water reactor vessel for cool-down and low temperature over-pressurization transients

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jeong Soon; Choi, Young Hwan; Jhung, Myung Jo [Safety Research Division, Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

    2016-04-15

    The failure probabilities of the reactor pressure vessel (RPV) for low temperature over-pressurization (LTOP) and cool-down transients are calculated in this study. For the cool-down transient, a pressure-temperature limit curve is generated in accordance with Section XI, Appendix G of the American Society of Mechanical Engineers (ASME) code, from which safety margin factors are deliberately removed for the probabilistic fracture mechanics analysis. Then, sensitivity analyses are conducted to understand the effects of some input parameters. For the LTOP transient, the failure of the RPV mostly occurs during the period of the abrupt pressure rise. For the cool-down transient, the decrease of the fracture toughness with temperature and time plays a main role in RPV failure at the end of the cool-down process. As expected, the failure probability increases with increasing fluence, Cu and Ni contents, and initial reference temperature-nil ductility transition (RTNDT). The effect of warm prestressing on the vessel failure probability for LTOP is not significant because most of the failures happen before the stress intensity factor reaches the peak value while its effect reduces the failure probability by more than one order of magnitude for the cool-down transient.

  17. Fracture mechanics evaluation of heavy welded structures

    International Nuclear Information System (INIS)

    Sprung, I.; Ericksson, C.W.; Zilberstein, V.A.

    1982-01-01

    This paper describes some applications of nondestructive examination (NDE) and engineering fracture mechanics to evaluation of flaws in heavy welded structures. The paper discusses not only widely recognized linear elastic fracture mechanics (LEFM) analysis, but also methods of the elastic-plastic fracture mechanics (EPFM), such as COD, J-integral, and Failure Assessment Diagram. Examples are given to highlight the importance of interaction between specialists providing input and the specialists performing the analysis. The paper points out that the critical parameters for as-welded structures when calculated by these methods are conservative since they are based on two pessimistic assumptions: that the magnitude of residual stress is always at the yield strength level, and that the residual stress always acts in the same direction as the applied (mechanical) stress. The suggestion is made that it would be prudent to use the COD or the FAD design curves for a conservative design. The appendix examines a J-design curve modified to include residual stresses

  18. Fracture mechanics analysis approach to assess structural integrity of the first confinement boundaries in ITER Generic Upper Port Plug structure

    Energy Technology Data Exchange (ETDEWEB)

    Guirao, Julio, E-mail: julio@natec-ingenieros.com [Numerical Analysis Technologies S.L. (NATEC), Gijon (Spain); Iglesias, Silvia; Vacas, Christian; Udintsev, Victor [CHD, Diagnostic Division, ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France); Pak, Sunil [Diagnostic and Control Team, National Fusion Research Institute, Daejeon (Korea, Republic of); Maquet, Philippe [CHD, Diagnostic Division, ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France); Rodriguez, Eduardo; Roces, Jorge [Department of Construction and Manufacturing Engineering, University of Oviedo, Gijon (Spain)

    2015-10-15

    Highlights: • A parametric submodel of the spot under study is developed. • The associated macro has the capability to successively re-build the submodel implementing the crack with the geometry of the updated crack front as a function of the predicted increments of length in the apexes of the crack from the calculated stress intensity factor at the crack front. • The analysis incorporates the crack behavior model to predict the evolution of the postulated defect under the application of the different transients. • The analysis is based on the Elasto-Plastic Fracture Mechanics (EPFM) theory to account for the ductility of the materials (316LN type stainless steel). - Abstract: This paper demonstrates structural integrity of the first confinement boundary in Generic Upper Port Plug structures against cracking during service. This constitutes part of the justification to demonstrate that the non-aggression to the confinement barrier requirement may be compatible with the absent of a specific in-service inspections (ISI) program in the trapezoidal section. Since the component will be subjected to 100% volumetric inspections it can be assumed that no defects below the threshold of applied Nondestructive Evaluation techniques will be present before its commissioning. Cracks during service would be associated to defects under Code acceptance limit. This limit can be reasonably taken as 2 mm. Using elastic–plastic fracture mechanics an initial defect is postulated at the worst location in terms of probability and impact on the confinement boundary. Its evolution is simulated through finite element analysis and final dimension at the end of service is estimated. Applying the procedures in RCC-MR 2007 (App-16) the stability of the crack is assessed. As relative high safety margin was achieved, a complementary assessment postulating an initial defect of 6 mm was also conducted. New margin calculated provides a more robust design.

  19. Fracture mechanisms in lead zirconate titanate ceramics

    International Nuclear Information System (INIS)

    Freiman, S.W.; Chuck, L.; Mecholsky, J.J.; Shelleman, D.L.

    1986-01-01

    Lead Zirconate Titanate (PZT) ceramics can be formed over a wide range of PbTiO 3 /PbZrO 3 ratios and exist in a number of crystal structures. This study involved the use of various fracture mechanics techniques to determine critical fracture toughness, K /SUB IC/ , as a function of composition, microstructure, temperature, and electrical and thermal history. The results of these experiments indicate that variations in K /SUB IC/ are related to phase transformations in the material as well as to other toughening mechanisms such as twinning and microcracking. In addition, the strength and fracture toughness of selected PZT ceramics were determined using specimens in which a crack was introduced by a Vicker's hardness indentor. The variation of K /SUB IC/ with composition and microstructure was related to the extent of twin-crack interaction. Comparison of the plot of strength as a function of indentation load with that predicted from indentation fracture models indicates the presence of internal stresses which contribute to failure. The magnitude of these internal stresses has been correlated with electrical properties of the ceramic. Fractographic analysis was used to determine the magnitude of internal stresses in specimens failing from ''natural flaws.''

  20. Deformation and fracture mechanics of engineering materials

    National Research Council Canada - National Science Library

    Hertzberg, Richard W; Vinci, Richard Paul; Hertzberg, Jason L

    2012-01-01

    "Hertzberg's 5th edition of Deformation & Fracture Mechanics of Engineering Materials offers several new features including a greater number and variety of homework problems using more computational software...

  1. Fracture Mechanics: Inspirations from Nature

    Directory of Open Access Journals (Sweden)

    David Taylor

    2014-10-01

    Full Text Available In Nature there are many examples of materials performing structural functions. Nature requires materials which are stiff and strong to provide support against various forces, including self-weight, the dynamic forces involved in movement, and external loads such as wind or the actions of a predator. These materials and structures have evolved over millions of years; the science of Biomimetics seeks to understand Nature and, as a result, to find inspiration for the creation of better engineering solutions. There has been relatively little fundamental research work in this area from a fracture mechanics point of view. Natural materials are quite brittle and, as a result, they have evolved several interesting strategies for preventing failure by crack propagation. Fatigue is also a major problem for many animals and plants. In this paper, several examples will be given of recent work in the Bioengineering Research Centre at Trinity College Dublin, investigating fracture and fatigue in such diverse materials as bamboo, the legs and wings of insects, and living cells.

  2. Study on calculation of influence function with fracture mechanics analysis method for circumferential through-crack pipe

    International Nuclear Information System (INIS)

    Zheng Bin; Lu Yuechuan; Zang Fenggang; Sun Yingxue

    2009-01-01

    In order to widen the application of the engineering method of EPRI, with a series of analysis on the 3D elastic and elastic-plastic fracture mechanics finite element, the crack open displacements (COD) of cracked pipe were calculated and a key influence function h 2 in EPRI engineering method was studied against the COD results of FEM. A calculation method of h2 under the condition of tension and bending combined load was introduced in detail. In order to validate this method, the calculated h 2 results were compared with that of EPRI, and the calculated COD results based on the h 2 results were compared with that of PICEP. The compared results indicated that the calculated h 2 results as well as the COD results and the corresponding reference values were respectively accordant, and the calculation method in this paper was validated accordingly. (authors)

  3. Fracture mechanics and physics approach to cleavage analysis in bcc monocrystals

    International Nuclear Information System (INIS)

    Ivanova, V.S.; Plastinin, V.M.

    1980-01-01

    On monocrystals of molybdenum obtained by electron--beam zone melting studied are the bonds between micro-and macroparameters of fracture controlling the limit state. Monocrystals of three orientations have been studied, namely >001 110 111<. Confirmed is an important role of plastic deformation in the (110) family planes at cleavage forming in the (100) family planes. A correlation connection is established between threshold value of the stress intensity coefficient and activation energy of plastic deformation

  4. Recent trends in fracture and damage mechanics

    CERN Document Server

    Zybell, Lutz

    2016-01-01

    This book covers a wide range of topics in fracture and damage mechanics. It presents historical perspectives as well as recent innovative developments, presented by peer reviewed contributions from internationally acknowledged authors.  The volume deals with the modeling of fracture and damage in smart materials, current industrial applications of fracture mechanics, and it explores advances in fracture testing methods. In addition, readers will discover trends in the field of local approach to fracture and approaches using analytical mechanics. Scholars in the fields of materials science, engineering and computational science will value this volume which is dedicated to Meinhard Kuna on the occasion of his 65th birthday in 2015. This book incorporates the proceedings of an international symposium that was organized to honor Meinhard Kuna’s contributions to the field of theoretical and applied fracture and damage mechanics.

  5. 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

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

    KAUST Repository

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

    2014-01-01

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

  7. Intermetallic alloys: Deformation, mechanical and fracture behaviour

    International Nuclear Information System (INIS)

    Dogan, B.

    1988-01-01

    The state of the art in intermetallic alloys development with particular emphasis on deformation, mechanical and fracture behaviour is documented. This review paper is prepared to lay the ground stones for a future work on mechanical property characterization and fracture behaviour of intermetallic alloys at GKSS. (orig.)

  8. Mechanical comparison between lengthened and short sacroiliac screws in sacral fracture fixation: a finite element analysis.

    Science.gov (United States)

    Zhao, Y; Zhang, S; Sun, T; Wang, D; Lian, W; Tan, J; Zou, D; Zhao, Y

    2013-09-01

    To compare the stability of lengthened sacroiliac screw and standard sacroiliac screw for the treatment of unilateral vertical sacral fractures; to provide reference for clinical applications. A finite element model of Tile type C pelvic ring injury (unilateral Denis type II fracture of the sacrum) was produced. The unilateral sacral fractures were fixed with lengthened sacroiliac screw and sacroiliac screw in six different types of models respectively. The translation and angle displacement of the superior surface of the sacrum (in standing position on both feet) were measured and compared. The stability of one lengthened sacroiliac screw fixation in S1 or S2 segment is superior to that of one sacroiliac screw fixation in the same sacral segment. The stability of one lengthened sacroiliac screw fixation in S1 and S2 segments respectively is superior to that of one sacroiliac screw fixation in S1 and S2 segments respectively. The stability of one lengthened sacroiliac screw fixation in S1 and S2 segments respectively is superior to that of one lengthened sacroiliac screw fixation in S1 or S2 segment. The stability of one sacroiliac screw fixation in S1 and S2 segments respectively is markedly superior to that of one sacroiliac screw fixation in S1 or S2 segment. The vertical and rotational stability of lengthened sacroiliac screw fixation and sacroiliac screw fixation in S2 is superior to that of S1. In a finite element model of type C pelvic ring disruption, S1 and S2 lengthened sacroiliac screws should be utilized for the fixation as regularly as possible and the most stable fixation is the combination of the lengthened sacroiliac screws of S1 and S2 segments. Even if lengthened sacroiliac screws cannot be systematically used due to specific conditions, one sacroiliac screw fixation in S1 and S2 segments respectively is recommended. No matter which kind of sacroiliac screw is used, if only one screw can be implanted, the fixation in S2 segment is more recommended

  9. Mechanical Integrity of Canisters Using a Fracture Mechanics Approach

    Energy Technology Data Exchange (ETDEWEB)

    Koyama, Tomofumi; Guoxiang Zhang; Lanru Jing [Royal Inst. of Technology, Stockholm (Sweden). Dept. of Land and Water Resources Engineering

    2006-07-15

    This report presents the methods and results of a research project about numerical modeling of mechanical integrity of cast-iron canisters for the final disposal of spent nuclear fuel in Sweden, using combined boundary element (BEM) and finite element (FEM) methods. The objectives of the project are: 1) to investigate the possibility of initiation and growth of fractures in the cast-iron canisters under the mechanical loading conditions defined in the premises of canister design by Swedish Nuclear Fuel and Waste Management Co. (SKB); 2) to investigate the maximum bearing capacity of the cast iron canisters under uniformly distributed and gradually increasing boundary pressure until plastic failure. Achievement of the two objectives may provide some quantitative evidence for the mechanical integrity and overall safety of the cast-iron canisters that are needed for the final safety assessment of the geological repository of the radioactive waste repository in Sweden. The geometrical dimension, distribution and magnitudes of loads and Material properties of the canisters and possible fractures were provided by the latest investigations of SKB. The results of the BEM simulations, using the commercial code BEASY, indicate that under the currently defined loading conditions the possibility of initiation of new fractures or growth of existing fractures (defects) are very small, due to the reasons that: 1) the canisters are under mainly compressive stresses; 2) the induced tensile stress regions are too small in both dimension and magnitude to create new fractures or to induce growth of existing fractures, besides the fact that the toughness of the fractures in the cast iron canisters are much higher that the stress intensity factors in the fracture tips. The results of the FEM simulation show a approximately 75 MPa maximum pressure beyond which plastic collapse of the cast-iron canisters may occur, using an elastoplastic Material model. This figure is smaller compared

  10. Physical fracture properties (fracture surfaces as information sources; crackgrowth and fracture mechanisms; exemples of cracks)

    International Nuclear Information System (INIS)

    Meny, Lucienne.

    1979-06-01

    Fracture surfaces are considered as a useful source of informations: an introduction to fractography is presented; the fracture surface may be observed through X ray microanalysis, and other physical methods such as Auger electron spectroscopy or secundary ion emission. The mechanisms of macroscopic and microscopic crackgrowth and fracture are described, in the case of unstable fracture (cleavage, ductile with shear, intergranular brittleness) and of progressive crack propagation (creep, fatigue). Exemples of cracks are presented in the last chapter [fr

  11. Fracture mechanisms and fracture control in composite structures

    Science.gov (United States)

    Kim, Wone-Chul

    Four basic failure modes--delamination, delamination buckling of composite sandwich panels, first-ply failure in cross-ply laminates, and compression failure--are analyzed using linear elastic fracture mechanics (LEFM) and the J-integral method. Structural failures, including those at the micromechanical level, are investigated with the aid of the models developed, and the critical strains for crack propagation for each mode are obtained. In the structural fracture analyses area, the fracture control schemes for delamination in a composite rib stiffener and delamination buckling in composite sandwich panels subjected to in-plane compression are determined. The critical fracture strains were predicted with the aid of LEFM for delamination and the J-integral method for delamination buckling. The use of toughened matrix systems has been recommended for improved damage tolerant design for delamination crack propagation. An experimental study was conducted to determine the onset of delamination buckling in composite sandwich panel containing flaws. The critical fracture loads computed using the proposed theoretical model and a numerical computational scheme closely followed the experimental measurements made on sandwich panel specimens of graphite/epoxy faceskins and aluminum honeycomb core with varying faceskin thicknesses and core sizes. Micromechanical models of fracture in composites are explored to predict transverse cracking of cross-ply laminates and compression fracture of unidirectional composites. A modified shear lag model which takes into account the important role of interlaminar shear zones between the 0 degree and 90 degree piles in cross-ply laminate is proposed and criteria for transverse cracking have been developed. For compressive failure of unidirectional composites, pre-existing defects play an important role. Using anisotropic elasticity, the stress state around a defect under a remotely applied compressive load is obtained. The experimentally

  12. Computational methods for fracture mechanics analysis of pressurized-thermal-shock experiments

    International Nuclear Information System (INIS)

    Bass, B.R.; Bryan, R.H.; Bryson, J.W.; Merkle, J.G.

    1984-01-01

    Extensive computational analyses are required to determine material parameters and optimum pressure-temperature transients compatible with proposed pressurized-thermal-shock (PTS) test scenarios and with the capabilities of the PTS test facility at the Oak Ridge National Laboratory (ORNL). Computational economy has led to the application of techniques suitable for parametric studies involving the analysis of a large number of transients. These techniques, which include analysis capability for two- and three-dimensional (2-D and 3-D) superposition, inelastic ligament stability, and upper-shelf arrest, have been incorporated into the OCA/USA computer program. Features of the OCA/USA program are discussed, including applications to the PTS test configuration

  13. Computational methods for fracture mechanics analysis of pressurized-thermal-shock experiments

    International Nuclear Information System (INIS)

    Bass, B.R.; Bryan, R.H.; Bryson, J.W.; Merkle, J.G.

    1984-01-01

    Extensive computational analyses are required to determine material parameters and optimum pressure-temperature transients compatible with proposed pressurized-thermal-shock (PTS) test scenarios and with the capabilities of the PTS test facility at the Oak Ridge National Laboratory (ORNL). Computational economy has led to the application of techniques suitable for parametric studies involving the analysis of a large number of transients. These techniques, which include analysis capability for two- and three-dimensional (2-D and 3-D) superposition, inelastic ligament stability, and upper-shelf arrest, have been incorporated into the OCA/ USA computer program. Features of the OCA/USA program are discussed, including applications to the PTS test configuration. (author)

  14. Test techniques for fracture mechanics testing

    International Nuclear Information System (INIS)

    Schwalbe, K.H.

    1980-01-01

    Test methods for fracture mechanics tests are described. Two groups of techniques are distinguished: Those for measurement of stable crack growth and those for determination of the loading parameters. (orig.) [de

  15. Hybrid-finite-element analysis of some nonlinear and 3-dimensional problems of engineering fracture mechanics

    Science.gov (United States)

    Atluri, S. N.; Nakagaki, M.; Kathiresan, K.

    1980-01-01

    In this paper, efficient numerical methods for the analysis of crack-closure effects on fatigue-crack-growth-rates, in plane stress situations, and for the solution of stress-intensity factors for arbitrary shaped surface flaws in pressure vessels, are presented. For the former problem, an elastic-plastic finite element procedure valid for the case of finite deformation gradients is developed and crack growth is simulated by the translation of near-crack-tip elements with embedded plastic singularities. For the latter problem, an embedded-elastic-singularity hybrid finite element method, which leads to a direct evaluation of K-factors, is employed.

  16. A generic approach for a linear elastic fracture mechanics analysis of components containing residual stress

    International Nuclear Information System (INIS)

    Lee, Hyeong Y.; Nikbin, Kamran M.; O'Dowd, Noel P.

    2005-01-01

    A review of through thickness transverse residual stress distribution measurements in a number of components, manufactured from a range of steels, has been carried out. Residual stresses introduced by welding and mechanical deformation have been considered. The geometries consisted of welded T-plate joints, pipe butt joints, tube-on-plate joints, tubular Y-joints and tubular T-joints as well as cold bent tubes and repair welds. In addition, the collected data cover a range of engineering steels including ferritic, austenitic, C-Mn and Cr-Mo steels. The methods used to measure the residual stresses also varied. These included neutron diffraction, X-ray diffraction and deep hole drilling techniques. Measured residual stress data, normalised by their respective yield stress have shown an inverse linear correlation versus the normalised depth of the region containing the residual stress (up to 0.5 of the component thickness). A simplified generic residual stress profile based on a linear fit to the data is proposed for the case of a transverse residual tensile stress field. Whereas the profiles in assessment procedures are case specific the proposed linear profile can be varied to produce a combination of membrane and bending stress distributions to give lower or higher levels of conservatism on stress intensity factors, depending on the amount of case specific data available or the degree of safety required

  17. Elastic-plastic analysis of fracture mechanics test specimens. Part 2

    International Nuclear Information System (INIS)

    Talja, H.; Wallin, K.

    1984-12-01

    This is second part of the report of the research program 'Comparisons between computational and experimental elastic-plastic results' started at the Technical Research Centre of Finland in 1981. The first part of the research program was reported earlier and contained a two dimensional linear elastic finite element analysis of four specimen geometries (CT, RCT, ASTM-3P and Charpy-V) and testing and elastic-plastic analysis of the specimen (EGF71; 1TCT, material A 542). In this report the second part of the program containing the testing and 2-D elastic-plastic analyses of five specimens is described. The four specimen geometries mentioned above and two different materials (stainless steel AISI 304 and ferrite pressure vessel steel A533B) are considered. The following comparisons are presented in the report: load vs. load displacement curves, J-integral, crack opening displacement (COD), J vs. COD and the size of the plastic zone. The agreement between the computational and experimental results is quite good. Complete agreement can be achieved only with 3-dimensional calculation models. (author)

  18. Development of a computer code 'CRACK' for elastic and elastoplastic fracture mechanics analysis of 2-D structures by finite element technique

    International Nuclear Information System (INIS)

    Dutta, B.K.; Kakodkar, A.; Maiti, S.K.

    1986-01-01

    The fracture mechanics analysis of nuclear components is required to ensure prevention of sudden failure due to dynamic loadings. The linear elastic analysis near to a crack tip shows presence of stress singularity at the crack tip. The simulation of this singularity in numerical methods enhance covergence capability. In finite element technique this can be achieved by placing mid nodes of 8 noded or 6 noded isoparametric elements, at one fourth ditance from crack tip. Present report details this characteristic of finite element, implementation of this element in a code 'CRACK', implementation of J-integral to compute stress intensity factor and solution of number of cases for elastic and elastoplastic fracture mechanics analysis. 6 refs., 6 figures. (author)

  19. Mechanical Behaviour of Materials Volume II Fracture Mechanics and Damage

    CERN Document Server

    François, Dominique; Zaoui, André

    2013-01-01

    Designing new structural materials, extending lifetimes and guarding against fracture in service are among the preoccupations of engineers, and to deal with these they need to have command of the mechanics of material behaviour. This ought to reflect in the training of students. In this respect, the first volume of this work deals with elastic, elastoplastic, elastoviscoplastic and viscoelastic behaviours; this second volume continues with fracture mechanics and damage, and with contact mechanics, friction and wear. As in Volume I, the treatment links the active mechanisms on the microscopic scale and the laws of macroscopic behaviour. Chapter I is an introduction to the various damage phenomena. Chapter II gives the essential of fracture mechanics. Chapter III is devoted to brittle fracture, chapter IV to ductile fracture and chapter V to the brittle-ductile transition. Chapter VI is a survey of fatigue damage. Chapter VII is devoted to hydogen embrittlement and to environment assisted cracking, chapter VIII...

  20. Probabilistic Fracture Mechanics Analysis of the Orbiter's LH2 Feedline Flowliner

    Science.gov (United States)

    Bonacuse, Peter J. (Technical Monitor); Hudak, Stephen J., Jr.; Huyse, Luc; Chell, Graham; Lee, Yi-Der; Riha, David S.; Thacker, Ben; McClung, Craig; Gardner, Brian; Leverant, Gerald R.; hide

    2005-01-01

    Work performed by Southwest Research Institute (SwRI) as part of an Independent Technical Assessment (ITA) for the NASA Engineering and Safety Center (NESC) is summarized. The ITA goal was to establish a flight rationale in light of a history of fatigue cracking due to flow induced vibrations in the feedline flowliners that supply liquid hydrogen to the space shuttle main engines. Prior deterministic analyses using worst-case assumptions predicted failure in a single flight. The current work formulated statistical models for dynamic loading and cryogenic fatigue crack growth properties, instead of using worst-case assumptions. Weight function solutions for bivariant stressing were developed to determine accurate crack "driving-forces". Monte Carlo simulations showed that low flowliner probabilities of failure (POF = 0.001 to 0.0001) are achievable, provided pre-flight inspections for cracks are performed with adequate probability of detection (POD)-specifically, 20/75 mils with 50%/99% POD. Measurements to confirm assumed POD curves are recommended. Since the computed POFs are very sensitive to the cyclic loads/stresses and the analysis of strain gage data revealed inconsistencies with the previous assumption of a single dominant vibrant mode, further work to reconcile this difference is recommended. It is possible that the unaccounted vibrational modes in the flight spectra could increase the computed POFs.

  1. Three-dimensional effects in fracture mechanics

    International Nuclear Information System (INIS)

    Benitez, F.G.

    1991-01-01

    An overall view of the pioneering theories and works, which enlighten the three-dimensional nature of fracture mechanics during the last years is given. the main aim is not an exhaustive reviewing but the displaying of the last developments on this scientific field in a natural way. This work attempts to envisage the limits of disregarding the three-dimensional behaviour in theories, analyses and experiments. Moreover, it tries to draw attention on the scant fervour, although increasing, this three-dimensional nature of fracture has among the scientific community. Finally, a constructive discussion is presented on the use of two-dimensional solutions in the analysis of geometries which bear a three-dimensional configuration. the static two-dimensional solutions and its applications fields are reviewed. also, the static three-dimensional solutions, wherein a comparative analysis with elastoplastic and elastostatic solutions are presented. to end up, the dynamic three-dimensional solutions are compared to the asymptotic two-dimensional ones under the practical applications point of view. (author)

  2. Probabilistic finite elements for fracture mechanics

    Science.gov (United States)

    Besterfield, Glen

    1988-01-01

    The probabilistic finite element method (PFEM) is developed for probabilistic fracture mechanics (PFM). A finite element which has the near crack-tip singular strain embedded in the element is used. Probabilistic distributions, such as expectation, covariance and correlation stress intensity factors, are calculated for random load, random material and random crack length. The method is computationally quite efficient and can be expected to determine the probability of fracture or reliability.

  3. Sensitivity analysis of a coupled hydro-mechanical paleo-climate model of density-dependent groundwater flow in discretely fractured crystalline rock

    International Nuclear Information System (INIS)

    Normani, S.D.; Sykes, J.F.

    2011-01-01

    A high resolution three-dimensional sub-regional scale (104 km 2 ) density-dependent, discretely fractured groundwater flow model with hydro-mechanical coupling and pseudo-permafrost was developed from a larger 5734 km 2 regional-scale groundwater flow model of a Canadian Shield setting. The objective of the work is to determine the sensitivity of modelled groundwater system evolution to the hydro-mechanical parameters. The discrete fracture dual continuum numerical model FRAC3DVS-OPG was used for all simulations. A discrete fracture network model delineated from surface features was superimposed onto an approximate 790 000 element domain mesh with approximately 850 000 nodes. Orthogonal fracture faces (between adjacent finite element grid blocks) were used to best represent the irregular discrete fracture zone network. Interconnectivity of the permeable fracture zones is an important pathway for the possible migration and subsequent reduction in groundwater and contaminant residence times. The crystalline rock matrix between these structural discontinuities was assigned mechanical and flow properties characteristic of those reported for the Canadian Shield. The variation of total dissolved solids with depth was assigned using literature data for the Canadian Shield. Performance measures for the sensitivity analysis include equivalent freshwater heads, environmental heads, linear velocities, and depth of penetration by conservative non-decaying tracers released at the surface. A 121 000 year North American continental scale paleo-climate simulation was applied to the domain with ice-sheet histories estimated by the University of Toronto Glacial Systems Model (UofT GSM). Hydro-mechanical coupling between the rock matrix and the pore fluid, due to the ice sheet normal stress, was included in the simulations. The flow model included the influence of vertical strain and assumed that areal loads were homogeneous. Permafrost depth was applied as a permeability reduction

  4. Failure analysis of fractured dental zirconia implants.

    Science.gov (United States)

    Gahlert, M; Burtscher, D; Grunert, I; Kniha, H; Steinhauser, E

    2012-03-01

    The purpose of the present study was the macroscopic and microscopic failure analysis of fractured zirconia dental implants. Thirteen fractured one-piece zirconia implants (Z-Look3) out of 170 inserted implants with an average in situ period of 36.75±5.34 months (range from 20 to 56 months, median 38 months) were prepared for macroscopic and microscopic (scanning electron microscopy [SEM]) failure analysis. These 170 implants were inserted in 79 patients. The patient histories were compared with fracture incidences to identify the reasons for the failure of the implants. Twelve of these fractured implants had a diameter of 3.25 mm and one implant had a diameter of 4 mm. All fractured implants were located in the anterior side of the maxilla and mandibula. The patient with the fracture of the 4 mm diameter implant was adversely affected by strong bruxism. By failure analysis (SEM), it could be demonstrated that in all cases, mechanical overloading caused the fracture of the implants. Inhomogeneities and internal defects of the ceramic material could be excluded, but notches and scratches due to sandblasting of the surface led to local stress concentrations that led to the mentioned mechanical overloading by bending loads. The present study identified a fracture rate of nearly 10% within a follow-up period of 36.75 months after prosthetic loading. Ninety-two per cent of the fractured implants were so-called diameter reduced implants (diameter 3.25 mm). These diameter reduced implants cannot be recommended for further clinical use. Improvement of the ceramic material and modification of the implant geometry has to be carried out to reduce the failure rate of small-sized ceramic implants. Nevertheless, due to the lack of appropriate laboratory testing, only clinical studies will demonstrate clearly whether and how far the failure rate can be reduced. © 2011 John Wiley & Sons A/S.

  5. Petrous bone fracture: a virtual trauma analysis.

    Science.gov (United States)

    Montava, Marion; Deveze, Arnaud; Arnoux, Pierre-Jean; Bidal, Samuel; Brunet, Christian; Lavieille, Jean-Pierre

    2012-06-01

    The temporal bone shields sensorineural, nervous, and vascular structures explaining the potential severity and complications of trauma related to road and sport accidents. So far, no clear data are available on the exact mechanisms involved for fracture processes. Modelization of structures helps to answer these concerns. Our objective was to design a finite element model of the petrous bone structure to modelize temporal bone fracture propagation in a scenario of lateral impact. A finite element model of the petrous bone structure was designed based on computed tomography data. A 7-m/s lateral impact was simulated to reproduce a typical lateral trauma. Results of model analysis was based on force recorded, stress level on bone structure up to induce a solution of continuity of the bony structure. Model simulation showed that bone fractures follow the main axes of the petrous bone and occurred in a 2-step process: first, a crush, and second, a massive fissuration of the petrous bone. The lines of fracture obtained by simulation of a lateral impact converge toward the middle ear region. This longitudinal fracture is located at the mastoid-petrous pyramid junction. Using this model, it was possible to map petrous bone fractures including fracture chronology and areas of fusion of the middle ear region. This technique may represent a first step to investigate the pathophysiology of the petrous bone fractures, aiming to define prognostic criteria for patients' care.

  6. A three-dimensional analysis of fracture mechanics test pieces of different geometries part 2 - Constraint and material variations

    Energy Technology Data Exchange (ETDEWEB)

    Tkach, Y., E-mail: Yuri.Tkach@WGIM.com [Department of Civil and Structural Engineering, School of MACE, UMIST/University of Manchester, PO Box 88, Manchester M60 1QD (United Kingdom); Burdekin, F.M., E-mail: mburdekin@aol.com [Department of Civil and Structural Engineering, School of MACE, UMIST/University of Manchester, PO Box 88, Manchester M60 1QD (United Kingdom)

    2012-05-15

    This paper reports the second stage of an extensive series of detailed three-dimensional elastic-plastic finite element analyses on the influence of fracture mechanics test specimen geometry and different material properties on constraint and triaxiality in the near crack tip region. The specimens studied were pre-cracked plain-sided and side-grooved Charpy sized specimens, plain-sided and side-grooved compact tension specimens of thickness B = 25 mm and plain-sided compact tension specimens of thickness B = 100 mm all with the ratio of the crack length to the specimen width a/W = 0.5. Stress-strain curves of materials of different yield strength and strain hardening behaviour spanning the range of practical interest for typical structural steels were implemented into the finite element models. The level of constraint in the specimens modelled has been characterised in terms of both the Q-stress parameter and the ratio of hydrostatic to the equivalent stress components. It has been established that in-plane constraint in the fracture toughness test pieces is significantly affected by the absolute ligament size of the specimen. It has also been shown that the strain hardening behaviour is one of the major material parameters defining constraint level in the fracture toughness specimen. - Highlights: Black-Right-Pointing-Pointer 3D FE analyses on plain and side-grooved Charpy sized and CT specimens of two sizes. Black-Right-Pointing-Pointer Crack tip constraint analysed for Q-stress and hydrostatic/equivalent stress ratio. Black-Right-Pointing-Pointer In-plane constraint is significantly affected by the absolute ligament size. Black-Right-Pointing-Pointer Constraint level is significantly affected by material strain hardening behaviour.

  7. A three-dimensional analysis of fracture mechanics test pieces of different geometries part 2 - Constraint and material variations

    International Nuclear Information System (INIS)

    Tkach, Y.; Burdekin, F.M.

    2012-01-01

    This paper reports the second stage of an extensive series of detailed three-dimensional elastic-plastic finite element analyses on the influence of fracture mechanics test specimen geometry and different material properties on constraint and triaxiality in the near crack tip region. The specimens studied were pre-cracked plain-sided and side-grooved Charpy sized specimens, plain-sided and side-grooved compact tension specimens of thickness B = 25 mm and plain-sided compact tension specimens of thickness B = 100 mm all with the ratio of the crack length to the specimen width a/W = 0.5. Stress–strain curves of materials of different yield strength and strain hardening behaviour spanning the range of practical interest for typical structural steels were implemented into the finite element models. The level of constraint in the specimens modelled has been characterised in terms of both the Q-stress parameter and the ratio of hydrostatic to the equivalent stress components. It has been established that in-plane constraint in the fracture toughness test pieces is significantly affected by the absolute ligament size of the specimen. It has also been shown that the strain hardening behaviour is one of the major material parameters defining constraint level in the fracture toughness specimen. - Highlights: ► 3D FE analyses on plain and side-grooved Charpy sized and CT specimens of two sizes. ► Crack tip constraint analysed for Q-stress and hydrostatic/equivalent stress ratio. ► In-plane constraint is significantly affected by the absolute ligament size. ► Constraint level is significantly affected by material strain hardening behaviour.

  8. Mechanical properties and fracture of titanium hydrides

    International Nuclear Information System (INIS)

    Koketsu, Hideyuki; Taniyama, Yoshihiro; Yonezu, Akio; Cho, Hideo; Ogawa, Takeshi; Takemoto, Mikio; Nakayama, Gen

    2006-01-01

    Titanium hydrides tend to suffer fracture when their thicknesses reach a critical thickness. Morphology and mechanical property of the hydrides are, however, not well known. The study aims to reveal the hydride morphology and fracture types of the hydrides. Chevron shaped plate hydrides were found to be produced on the surface of pure titanium (Grade 1) and Grade 7 titanium absorbing hydrogen. There were tree types of fracture of the hydrides, i.e., crack in hydride layer, exfoliation of the layer and shear-type fracture of the hydride plates, during the growth of the hydrides and deformation. We next estimated the true stress-strain curves of the hydrides on Grade 1 and 7 titanium using the dual Vickers indentation method, and the critical strain causing the Mode-I fine crack by indentation. Fracture strength and strain of the hydrides in Grade 1 titanium were estimated as 566 MPa and 4.5%, respectively. Those of the hydride in Grade 7 titanium were 498 MPa and 16%. Though the fracture strains estimated from the plastic instability of true stress-strain curves were approximately the half of those estimated by finite element method, the titanium hydrides were estimated to possess some extent of toughness or plastic deformation capability. (author)

  9. Numerical methods in dynamic fracture mechanics

    International Nuclear Information System (INIS)

    Beskos, D.E.

    1987-01-01

    A review of numerical methods for the solution of dynamic problems of fracture mechanics is presented. Finite difference, finite element and boundary element methods as applied to linear elastic or viscoelastic and non-linear elastoplastic or elastoviscoplastic dynamic fracture mechanics problems are described and critically evaluated. Both cases of stationary cracks and rapidly propagating cracks of simple I, II, III or mixed modes are considered. Harmonically varying with time or general transient dynamic disturbances in the form of external loading or incident waves are taken into account. Determination of the dynamic stress intensity factor for stationary cracks or moving cracks with known velocity history as well as determination of the crack-tip propagation history for given dynamic fracture toughness versus crack velocity relation are described and illustrated by means of certain representative examples. Finally, a brief assessment of the present state of knowledge is made and research needs are identified

  10. Geometry, mechanics and transmissivity of rock fractures

    International Nuclear Information System (INIS)

    Lanaro, F.

    2001-04-01

    This thesis work investigates methods and tools for characterising, testing and modelling the behaviour of rock fractures. Using a 3D-laser-scanning technique, the topography of the surfaces and their position with respect to one another are measured. From the fracture topography, fracture roughness, angularity and aperture are quantified; the major features used for characterisation. The standard deviations for the asperity heights, surface slopes and aperture are determined. These statistical parameters usually increase/decrease according to power laws of the sampling size, and sometimes reach a sill beyond which they become constant. Also the number of contact spots with a certain area decreases according to a power-law function of the area. These power-law relations reveal the self affine fractal nature of roughness and aperture. Roughness is 'persistent' while aperture varies between 'persistent' and 'anti-persistent' probably depending on the degree of match of the fracture walls. The fractal models for roughness, aperture and contact area are used to develop a constitutive model, based on contact mechanics, for describing the fracture normal and shear deformability. The experimental testing results of normal deformability are simulated well by the model whereas fracture shear deformability is not as well modelled. The model predicts well fracture dilation but is too stiff compared to rock samples. A mathematical description of the aperture pattern during shearing is also formulated. The mean value and covariance of the aperture in shearing is calculated and verifies reported observations. The aperture map of samples is inserted in a numerical program for flow calculation. The 'integral transform method' is used for solving the Reynolds' equation; it transforms the fracture transmissivity pattern into a frequency-based function. This closely resembles the power laws that describe fractals. This function can be described directly from the fractal properties of

  11. Primer: Fracture mechanics in the nuclear power industry

    International Nuclear Information System (INIS)

    Wessel, E.T.; Server, W.L.; Kennedy, E.L.

    1990-01-01

    This Primer is intended to familiarize utility engineers with the fracture mechanics technology and to provide the basis for a working knowledge of the subject. It is directed towards all the engineering disciplines that are involved either directly or indirectly with the structural reliability of electrical power generation equipment and systems. These engineering disciplines include such areas as: design and stress analysis, metallurgy and materials, nondestructive inspection and quality control, structural analysis and reliability engineering, chemical engineering and water chemistry control, and architectural engineering. This Primer does not provide a comprehensive, in-depth treatment of all the detailed aspects involved in fracture mechanics. It does, however, provide sufficient information and a common vocabulary that should enable engineers to: read and converse intelligently about the subject, understand and utilize ASME Codes and Regulatory Guides involving fracture mechanics, absorb technical information presented and discussed at various technical meetings, and begin to apply this technology towards actual engineering problems encountered in the course of their work. Example problems are provided to further enhance an understanding of fracture mechanics. Also, Appendix A describes fracture mechanics computer codes available through EPRI to analyze rotors, reactor pressure vessels and piping

  12. Review of Acceleration Methods for Seismic Analysis of Through-Wall Cracked Piping from the Viewpoint of Linear Elastic Fracture Mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jong Sung; Kim, Yong Woo [Sunchon National University, Suncheon (Korea, Republic of)

    2014-10-15

    Two acceleration methods, an effective force method (or inertia method) and a large mass method, have been applied for performing time history seismic analysis. The acceleration methods for uncracked structures have been verified via previous studies. However, no study has identified the validity of these acceleration methods for cracked piping. In this study, the validity of the acceleration methods for through-wall cracked piping is assessed via time history implicit dynamic elastic seismic analysis from the viewpoint of linear elastic fracture mechanics. As a result, it is identified that both acceleration methods show the same results for cracked piping if a large mass magnitude and maximum time increment are adequately selected.

  13. Review of Acceleration Methods for Seismic Analysis of Through-Wall Cracked Piping from the Viewpoint of Linear Elastic Fracture Mechanics

    International Nuclear Information System (INIS)

    Kim, Jong Sung; Kim, Yong Woo

    2014-01-01

    Two acceleration methods, an effective force method (or inertia method) and a large mass method, have been applied for performing time history seismic analysis. The acceleration methods for uncracked structures have been verified via previous studies. However, no study has identified the validity of these acceleration methods for cracked piping. In this study, the validity of the acceleration methods for through-wall cracked piping is assessed via time history implicit dynamic elastic seismic analysis from the viewpoint of linear elastic fracture mechanics. As a result, it is identified that both acceleration methods show the same results for cracked piping if a large mass magnitude and maximum time increment are adequately selected

  14. Fracture mechanics analysis of reactor pressure vessel under pressurized thermal shock - The effect of elastic-plastic behavior and stainless steel cladding -

    International Nuclear Information System (INIS)

    Joo, Jae Hwang; Kang, Ki Ju; Jhung, Myung Jo

    2002-01-01

    Performed here is an assessment study for deterministic fracture mechanics analysis of a pressurized thermal shock (PTS). The PTS event means an event or transient in pressurized water reactors (PWRs) causing severe overcooling (thermal shock) concurrent with or followed by significant pressure in the reactor vessel. The problems consisting of two transients and 10 cracks are solved and maximum stress intensity factors and maximum allowable nil-ductility reference temperatures are calculated. Their results are compared each other to address the general characteristics between transients, crack types and analysis methods. The effects of elastic-plastic material behavior and clad coating on the inner surface are explored

  15. Fracture mechanics of collagen fibrils

    DEFF Research Database (Denmark)

    Svensson, Rene B; Mulder, Hindrik; Kovanen, Vuokko

    2013-01-01

    Tendons are important load-bearing structures, which are frequently injured in both sports and work. Type I collagen fibrils are the primary components of tendons and carry most of the mechanical loads experienced by the tissue, however, knowledge of how load is transmitted between and within...... fibrils is limited. The presence of covalent enzymatic cross-links between collagen molecules is an important factor that has been shown to influence mechanical behavior of the tendons. To improve our understanding of how molecular bonds translate into tendon mechanics, we used an atomic force microscopy...... technique to measure the mechanical behavior of individual collagen fibrils loaded to failure. Fibrils from human patellar tendons, rat-tail tendons (RTTs), NaBH₄ reduced RTTs, and tail tendons of Zucker diabetic fat rats were tested. We found a characteristic three-phase stress-strain behavior in the human...

  16. Relating Cohesive Zone Model to Linear Elastic Fracture Mechanics

    Science.gov (United States)

    Wang, John T.

    2010-01-01

    The conditions required for a cohesive zone model (CZM) to predict a failure load of a cracked structure similar to that obtained by a linear elastic fracture mechanics (LEFM) analysis are investigated in this paper. This study clarifies why many different phenomenological cohesive laws can produce similar fracture predictions. Analytical results for five cohesive zone models are obtained, using five different cohesive laws that have the same cohesive work rate (CWR-area under the traction-separation curve) but different maximum tractions. The effect of the maximum traction on the predicted cohesive zone length and the remote applied load at fracture is presented. Similar to the small scale yielding condition for an LEFM analysis to be valid. the cohesive zone length also needs to be much smaller than the crack length. This is a necessary condition for a CZM to obtain a fracture prediction equivalent to an LEFM result.

  17. Role of fracture mechanics in modern technology

    International Nuclear Information System (INIS)

    Sih, G.C.

    1987-01-01

    The conference served as a forum not only for reviewing past concepts and technologies but it provided an opportunity for many of the designers, engineers and scientists to come forth with more advanced ideas so that fracture mechanics application can be broadened and employed more effectively to avoid unexpected failures that are annoying, costly and destructive of credibility of the engineering community in general

  18. Fractures and Rock Mechanics, Phase 1

    DEFF Research Database (Denmark)

    Krogsbøll, Anette; Jakobsen, Finn; Madsen, Lena

    1997-01-01

    The main objective of the project is to combine geological descriptions of fractures, chalk types and rock mechanical properties in order to investigate whether the chosen outcrops can be used as analogues to reservoir chalks. This report deals with 1) geological descriptions of outcrop locality...

  19. Fractures and Rock Mechanics, Phase 1

    DEFF Research Database (Denmark)

    Havmøller, Ole; Krogsbøll, Anette

    1997-01-01

    The main objectives of the project are to combine geological description of fractures, chalk types and rock mechanical properties, and to investigate whether the chosen outcrops can be used as analogues to reservoir chalks. Five chalk types, representing two outcrop localities: Stevns...

  20. Associations of early premenopausal fractures with subsequent fractures vary by sites and mechanisms of fractures.

    Science.gov (United States)

    Honkanen, R; Tuppurainen, M; Kroger, H; Alhava, E; Puntila, E

    1997-04-01

    In a retrospective population-based study we assessed whether and how self-reported former fractures sustained at the ages of 20-34 are associated with subsequent fractures sustained at the ages of 35-57. The 12,162 women who responded to fracture questions of the baseline postal enquiry (in 1989) of the Kuopio Osteoporosis Study, Finland formed the study population. They reported 589 former and 2092 subsequent fractures. The hazard ratio (HR), with 95% confidence interval (CI), of a subsequent fracture was 1.9 (1.6-2.3) in women with the history of a former fracture compared with women without such a history. A former low-energy wrist fracture was related to subsequent low-energy wrist [HR = 3.7 (2.0-6.8)] and high-energy nonwrist [HR = 2.4 (1.3-4.4)] fractures, whereas former high-energy nonwrist fractures were related only to subsequent high-energy nonwrist [HR = 2.8 (1.9-4.1)] but not to low-energy wrist [HR = 0.7 (0.3-1.8)] fractures. The analysis of bone mineral density (BMD) data of a subsample of premenopausal women who underwent dual x-ray absorptiometry (DXA) during 1989-91 revealed that those with a wrist fracture due to a fall on the same level at the age of 20-34 recorded 6.5% lower spinal (P = 0.140) and 10.5% lower femoral (P = 0.026) BMD than nonfractured women, whereas the corresponding differences for women with a former nonwrist fracture due to high-energy trauma were -1.8% (P = 0.721) and -2.4% (P = 0. 616), respectively. Our results suggest that an early premenopausal, low-energy wrist fracture is an indicator of low peak BMD which predisposes to subsequent fractures in general, whereas early high-energy fractures are mainly indicators of other and more specific extraskeletal factors which mainly predispose to same types of subsequent fractures only.

  1. Fracture Mechanisms in Steel Castings

    Directory of Open Access Journals (Sweden)

    Stradomski Z.

    2013-09-01

    Full Text Available The investigations were inspired with the problem of cracking of steel castings during the production process. A single mechanism of decohesion - the intergranular one - occurs in the case of hot cracking, while a variety of structural factors is decisive for hot cracking initiation, depending on chemical composition of the cast steel. The low-carbon and low-alloyed steel castings crack due to the presence of the type II sulphides, the cause of cracking of the high-carbon tool cast steels is the net of secondary cementite and/or ledeburite precipitated along the boundaries of solidified grains. Also the brittle phosphor and carbide eutectics precipitated in the final stage solidification are responsible for cracking of castings made of Hadfield steel. The examination of mechanical properties at 1050°C revealed low or very low strength of high-carbon cast steels.

  2. Mechanical dispersion in fractured crystalline rock systems

    International Nuclear Information System (INIS)

    Lafleur, D.W.; Raven, K.G.

    1986-12-01

    This report compiles and evaluates the hydrogeologic parameters describing the flow of groundwater and transport of solutes in fractured crystalline rocks. This report describes the processes of mechanical dispersion in fractured crystalline rocks, and compiles and evaluates the dispersion parameters determined from both laboratory and field tracer experiments. The compiled data show that extrapolation of the reliable test results performed over intermediate scales (10's of m and 10's to 100's of hours) to larger spatial and temporal scales required for performance assessment of a nuclear waste repository in crystalline rock is not justified. The reliable measures of longitudinal dispersivity of fractured crystalline rock are found to range between 0.4 and 7.8 m

  3. The optimal XFEM approximation for fracture analysis

    International Nuclear Information System (INIS)

    Jiang Shouyan; Du Chengbin; Ying Zongquan

    2010-01-01

    The extended finite element method (XFEM) provides an effective tool for analyzing fracture mechanics problems. A XFEM approximation consists of standard finite elements which are used in the major part of the domain and enriched elements in the enriched sub-domain for capturing special solution properties such as discontinuities and singularities. However, two issues in the standard XFEM should specially be concerned: efficient numerical integration methods and an appropriate construction of the blending elements. In the paper, an optimal XFEM approximation is proposed to overcome the disadvantage mentioned above in the standard XFEM. The modified enrichment functions are presented that can reproduced exactly everywhere in the domain. The corresponding FORTRAN program is developed for fracture analysis. A classic problem of fracture mechanics is used to benchmark the program. The results indicate that the optimal XFEM can alleviate the errors and improve numerical precision.

  4. Statistical fracture mechanics approach to the strength of brittle rock

    International Nuclear Information System (INIS)

    Ratigan, J.L.

    1981-06-01

    Statistical fracture mechanics concepts used in the past for rock are critically reviewed and modifications are proposed which are warranted by (1) increased understanding of fracture provided by modern fracture mechanics and (2) laboratory test data both from the literature and from this research. Over 600 direct and indirect tension tests have been performed on three different rock types; Stripa Granite, Sierra White Granite and Carrara Marble. In several instances assumptions which are common in the literature were found to be invalid. A three parameter statistical fracture mechanics model with Mode I critical strain energy release rate as the variant is presented. Methodologies for evaluating the parameters in this model as well as the more commonly employed two parameter models are discussed. The experimental results and analysis of this research indicate that surfacially distributed flaws, rather than volumetrically distributed flaws are responsible for rupture in many testing situations. For several of the rock types tested, anisotropy (both in apparent tensile strength and size effect) precludes the use of contemporary statistical fracture mechanics models

  5. Evaluation of fracture mechanics analyses used in RPV integrity assessment regarding brittle fracture

    International Nuclear Information System (INIS)

    Moinereau, D.; Faidy, C.; Valeta, M.P.; Bhandari, S.; Guichard, D.

    1997-01-01

    Electricite de France has conducted during these last years some experimental and numerical research programmes in order to evaluate fracture mechanics analyses used in nuclear reactor pressure vessels structural integrity assessment, regarding the risk of brittle fracture. These programmes included cleavage fracture tests on large scale cladded specimens containing subclad flaws with their interpretations by 2D and 3D numerical computations, and validation of finite element codes for pressurized thermal shocks analyses. Four cladded specimens made of ferritic steel A508 C13 with stainless steel cladding, and containing shallow subclad flaws, have been tested in four point bending at very low temperature in order to obtain cleavage failure. The specimen failure was obtained in each case in base metal by cleavage fracture. These tests have been interpreted by two-dimensional and three-dimensional finite element computations using different fracture mechanics approaches (elastic analysis with specific plasticity corrections, elastic-plastic analysis, local approach to cleavage fracture). The failure of specimens are conservatively predicted by different analyses. The comparison between the elastic analyses and elastic-plastic analyses shows the conservatism of specific plasticity corrections used in French RPV elastic analyses. Numerous finite element calculations have also been performed between EDF, CEA and Framatome in order to compare and validate several fracture mechanics post processors implemented in finite element programmes used in pressurized thermal shock analyses. This work includes two-dimensional numerical computations on specimens with different geometries and loadings. The comparisons show a rather good agreement on main results, allowing to validate the finite element codes and their post-processors. (author). 11 refs, 24 figs, 3 tabs

  6. Evaluation of fracture mechanics analyses used in RPV integrity assessment regarding brittle fracture

    Energy Technology Data Exchange (ETDEWEB)

    Moinereau, D [Electricite de France, Dept. MTC, Moret-sur-Loing (France); Faidy, C [Electricite de France, SEPTEN, Villeurbanne (France); Valeta, M P [Commisariat a l` Energie Atomique, Dept. DMT, Gif-sur-Yvette (France); Bhandari, S; Guichard, D [Societe Franco-Americaine de Constructions Atomiques (FRAMATOME), 92 - Paris-La-Defense (France)

    1997-09-01

    Electricite de France has conducted during these last years some experimental and numerical research programmes in order to evaluate fracture mechanics analyses used in nuclear reactor pressure vessels structural integrity assessment, regarding the risk of brittle fracture. These programmes included cleavage fracture tests on large scale cladded specimens containing subclad flaws with their interpretations by 2D and 3D numerical computations, and validation of finite element codes for pressurized thermal shocks analyses. Four cladded specimens made of ferritic steel A508 C13 with stainless steel cladding, and containing shallow subclad flaws, have been tested in four point bending at very low temperature in order to obtain cleavage failure. The specimen failure was obtained in each case in base metal by cleavage fracture. These tests have been interpreted by two-dimensional and three-dimensional finite element computations using different fracture mechanics approaches (elastic analysis with specific plasticity corrections, elastic-plastic analysis, local approach to cleavage fracture). The failure of specimens are conservatively predicted by different analyses. The comparison between the elastic analyses and elastic-plastic analyses shows the conservatism of specific plasticity corrections used in French RPV elastic analyses. Numerous finite element calculations have also been performed between EDF, CEA and Framatome in order to compare and validate several fracture mechanics post processors implemented in finite element programmes used in pressurized thermal shock analyses. This work includes two-dimensional numerical computations on specimens with different geometries and loadings. The comparisons show a rather good agreement on main results, allowing to validate the finite element codes and their post-processors. (author). 11 refs, 24 figs, 3 tabs.

  7. An efficient hydro-mechanical model for coupled multi-porosity and discrete fracture porous media

    Science.gov (United States)

    Yan, Xia; Huang, Zhaoqin; Yao, Jun; Li, Yang; Fan, Dongyan; Zhang, Kai

    2018-02-01

    In this paper, a numerical model is developed for coupled analysis of deforming fractured porous media with multiscale fractures. In this model, the macro-fractures are modeled explicitly by the embedded discrete fracture model, and the supporting effects of fluid and fillings in these fractures are represented explicitly in the geomechanics model. On the other hand, matrix and micro-fractures are modeled by a multi-porosity model, which aims to accurately describe the transient matrix-fracture fluid exchange process. A stabilized extended finite element method scheme is developed based on the polynomial pressure projection technique to address the displacement oscillation along macro-fracture boundaries. After that, the mixed space discretization and modified fixed stress sequential implicit methods based on non-matching grids are applied to solve the coupling model. Finally, we demonstrate the accuracy and application of the proposed method to capture the coupled hydro-mechanical impacts of multiscale fractures on fractured porous media.

  8. Flaw acceptance criteria taking into consideration the NDT: radiographic and ultrasonic testing. Analysis through the fracture mechanics methods

    International Nuclear Information System (INIS)

    Capurro, E.; Alicino, F.; Corvi, A.

    1993-01-01

    The present study compares and evaluates the flaw acceptance criteria of the non-destructive inspections meeting European Community standards, through the application of the fracture mechanics methods that were determined and verified by the previous activity. Some choices were made; these, however, do not change the general validity of the conclusions. Shaved full-penetration butt welds of Class 1 components making up the primary circuit were considered and the following parameters varied: standards: French, German, Italian (ASME III) and UK; material: AISI 316 and low alloy steel A 533; base material and weld metal; temperature: RT, 370 deg C for the austenitic and 260 deg C for the ferritic steel; ultrasonic and radiographic methods; defect position: surface and internal; stress condition: situations with different primary and secondary stresses. From a preliminary examination of this study it is evident that the large quantity of results available and the abundance of information contained therein make a simple and exhaustive synthesis difficult. In fact, different analyses are possible and we have, therefore, limited the research to activities to perform a comparison and a general evaluation of the acceptance criteria of the non-destructive testing. (authors). 57 refs., 25 figs., 11 tabs

  9. Cracking mechanism of shale cracks during fracturing

    Science.gov (United States)

    Zhao, X. J.; Zhan, Q.; Fan, H.; Zhao, H. B.; An, F. J.

    2018-06-01

    In this paper, we set up a model for calculating the shale fracture pressure on the basis of Huang’s model by the theory of elastic-plastic mechanics, rock mechanics and the application of the maximum tensile stress criterion, which takes into account such factors as the crustal stress field, chemical field, temperature field, tectonic stress field, the porosity of shale and seepage of drilling fluid and so on. Combined with the experimental data of field fracturing and the experimental results of three axis compression of shale core with different water contents, the results show that the error between the present study and the measured value is 3.85%, so the present study can provide technical support for drilling engineering.

  10. Mechanical transport in two-dimensional networks of fractures

    International Nuclear Information System (INIS)

    Endo, H.K.

    1984-04-01

    The objectives of this research are to evaluate directional mechanical transport parameters for anisotropic fracture systems, and to determine if fracture systems behave like equivalent porous media. The tracer experiments used to measure directional tortuosity, longitudinal geometric dispersivity, and hydraulic effective porosity are conducted with a uniform flow field and measurements are made from the fluid flowing within a test section where linear length of travel is constant. Since fluid flow and mechanical transport are coupled processes, the directional variations of specific discharge and hydraulic effective porosity are measured in regions with constant hydraulic gradients to evaluate porous medium equivalence for the two processes, respectively. If the fracture region behaves like an equivalent porous medium, the system has the following stable properties: (1) specific discharge is uniform in any direction and can be predicted from a permeability tensor; and (2) hydraulic effective porosity is directionally stable. Fracture systems with two parallel sets of continuous fractures satisfy criterion 1. However, in these systems hydraulic effective porosity is directionally dependent, and thus, criterion 2 is violated. Thus, for some fracture systems, fluid flow can be predicted using porous media assumptions, but it may not be possible to predict transport using porous media assumptions. Two discontinuous fracture systems were studied which satisfied both criteria. Hydraulic effective porosity for both systems has a value between rock effective porosity and total porosity. A length-density analysis (LDS) of Canadian fracture data shows that porous media equivalence for fluid flow and transport is likely when systems have narrow aperture distributions. 54 references, 90 figures, 7 tables

  11. Comparative study of fracture mechanical test methods for concrete

    DEFF Research Database (Denmark)

    Østergaard, Lennart; Olesen, John Forbes

    2004-01-01

    and the interpretation, i.e. the analysis needed to extract the stress-crack opening relationship, the fracture energy etc. Experiments are carried out with each test configuration using mature, high performance concrete. The results show that the UTT is a highly complicated test, which only under very well controlled...... circumstances will yield the true fracture mechanical properties. It is also shown that both the three point bending test and the WST are well-suited substitutes for the uniaxial tension test.......This paper describes and compares three different fracture mechanical test methods; the uniaxial tension test (UTT), the three point bending test (TPBT) and the wedge splitting test (WST). Potentials and problems with the test methods will be described with regard to the experiment...

  12. Finite elements in fracture mechanics theory, numerics, applications

    CERN Document Server

    Kuna, Meinhard

    2013-01-01

    Fracture mechanics has established itself as an important discipline of growing interest to those working to assess the safety, reliability and service life of engineering structures and materials. In order to calculate the loading situation at cracks and defects, nowadays numerical techniques like finite element method (FEM) have become indispensable tools for a broad range of applications. The present monograph provides an introduction to the essential concepts of fracture mechanics, its main goal being to procure the special techniques for FEM analysis of crack problems, which have to date only been mastered by experts. All kinds of static, dynamic and fatigue fracture problems are treated in two- and three-dimensional elastic and plastic structural components. The usage of the various solution techniques is demonstrated by means of sample problems selected from practical engineering case studies. The primary target group includes graduate students, researchers in academia and engineers in practice.

  13. Integration of fracture mechanics and NDE

    International Nuclear Information System (INIS)

    Njo, D.H.; McDonald, N.R.; Nichols, R.W.

    1991-01-01

    This paper addresses issues concerning the effective assessment of the structural integrity of safety related components, principally the primary system, in operating nuclear power plants. The failure mode of greatest safety concern is fracture and this is usually assessed by fracture mechanics (FM) procedures. These require the choice and application of an appropriate analytical method based on a knowledge of the materials, loading and environmental conditions, and characteristics of such defects as have been identified by non destructive examination (NDE). The paper focuses on capabilities and limitations of the NDE procedures, FM methods and other input information which must be taken into account in practical circumstances as well as some problems encountered. It concludes that an integral approach requiring mutual understanding, dialogue and cooperation among the materials, FM and NDE experts is essential for effective and reliable structural integrity assessments

  14. Analysis and modeling of coupled thermo-hydro-mechanical phenomena in 3D fractured media; Analyse et modelisation des phenomenes couples thermo-hydromecaniques en milieux fractures 3D

    Energy Technology Data Exchange (ETDEWEB)

    Canamon Valera, I

    2006-11-15

    This doctoral research was conducted as part of a joint France-Spain co-tutelage PhD thesis in the framework of a bilateral agreement between two universities, the Institut National Polytechnique de Toulouse (INPT) and the Universidad Politecnica de Madrid (UPM). It concerns a problem of common interest at the national and international levels, namely, the disposal of radioactive waste in deep geological repositories. The present work is devoted, more precisely, to near-field hydrogeological aspects involving mass and heat transport phenomena. The first part of the work is devoted to a specific data interpretation problem (pressures, relative humidities, temperatures) in a multi-barrier experimental system at the scale of a few meters - the 'Mock-Up Test' of the FEBEX project, conducted in Spain. Over 500 time series are characterized in terms of spatial, temporal, and/or frequency/scale-based statistical analysis techniques. The time evolution and coupling of physical phenomena during the experiment are analyzed, and conclusions are drawn concerning the behavior and reliability of the sensors. The second part of the thesis develops in more detail the 3-Dimensional (3D) modeling of coupled Thermo-Hydro-Mechanical phenomena in a fractured porous rock, this time at the scale of a hundred meters, based on the data of the 'In-Situ Test' of the FEBEX project conducted at the Grimsel Test Site in the Swiss Alps. As a first step, a reconstruction of the 3D fracture network is obtained by Monte Carlo simulation, taking into account through optimization the geomorphological data collected around the FEBEX gallery. The heterogeneous distribution of traces observed on the cylindrical wall of the tunnel is fairly well reproduced in the simulated network. In a second step, we develop a method to estimate the equivalent permeability of a many-fractured block by extending the superposition method of Ababou et al. [1994] to the case where the permeability of

  15. 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.

  16. Analysis of the competition between brittle and ductile fracture: application for the mechanical behaviour of C-Mn and theirs welds

    International Nuclear Information System (INIS)

    Le Corre, V.

    2006-09-01

    This study deals with the fracture behaviour of welded thin structures in the ductile to brittle transition range. It aims to propose a criterion to define the conditions for which the risk of fracture by cleavage does not exist on a cracked structure. The literature review shows that the difficulties of prediction of the fracture behaviour of a structure are related to the dependence of the fracture probability to the mechanical fields at the crack tip. The ductile to brittle transition range thus depends on the studied geometry of the structure. A threshold stress, below which cleavage cannot take place, is defined using fracture tests on notched specimens broken at very low temperature. The finite element numerical simulation of fracture tests on CT specimens in the transition range shows a linear relationship between the fracture probability and the volume exceeding the threshold stress, thus showing the relevance of the proposed criterion. Moreover, several relations are established allowing to simplify the identification of the criterion parameters. The criterion is applied to a nuclear structural C-Mn steel, by focusing more particularly on the higher boundary of the transition range. A fracture test on a full-scale pipe is designed, developed, carried out and analysed using its numerical simulation. The results show firstly that, on the structure, the transition range is shifted in temperature, compared to laboratory specimens, due to the low plasticity constraint achieved in thin structures, and secondly that the threshold stress criterion allows to estimate simply this shift. (author)

  17. Introduction into technical application of fracture mechanics. 3. rev. ed.

    International Nuclear Information System (INIS)

    Heckel, K.

    1991-01-01

    Technical components made out of metal material are liable to be defective. Cracks are the most dangerous defects. Based on fracture mechanics methods were developed which permit to estimate the proveness of cracks to intrate fracture. The present book is restricted to the standardised methods of fracture mechanics. Theoretical foundations of various concepts aspect under the fracture mechanics are given. Experimental methods of determining material characteristics of fracture mechanics are explained in detail as a profound knowledge of testing criteria is necessary in order to be able to a characteristic to a component. This book contains the latest level of standardised methods of fracture mechanics. It is meant for advanced students and engineers working in practice. Some fully calculated examples are used as an introduction into the thinking of fracture mechanics. (orig./MM) [de

  18. Use of fracture mechanics in engineering problems

    Energy Technology Data Exchange (ETDEWEB)

    Carter, C S

    1965-02-26

    If an engineering material containing a crack is subjected to a slowly increasing load, applied so that the crack tends to open, a small zone of plastic yielding develops at the crack tip. This zone increases in size with increasing load, and has the effect of resisting the tendency of the crack to extend. The basic concepts of fracture mechanics are outlined and the significance of crack toughness as measured by KDcU and KD1cU which relate the applied stress and crack size for unstable fracture prior to general yielding is discussed. The methods available for crack-toughness evaluation are indicated, and the mathematical expressions describing KDcU and KD1cU for a variety of geometrical situations are quoted. This approach to the design of fracture- resistant structures has been used in a number of fields in the U.S. and could be of value to the British steam turbine, aerospace, and pressure-vessel industries for design, inspection, and material selection. (64 refs.)

  19. Micro- and macroapproaches in fracture mechanics for interpreting brittle fracture and fatigue crack growth

    International Nuclear Information System (INIS)

    Ekobori, T.; Konosu, S.; Ekobori, A.

    1980-01-01

    Classified are models of the crack growth mechanism, and in the framework of the fracture mechanics suggested are combined micro- and macroapproaches to interpreting the criterion of the brittle fracture and fatigue crack growth as fracture typical examples, when temporal processes are important or unimportant. Under the brittle fracture conditions the crack propagation criterion is shown to be brought with the high accuracy to a form analogous to one of the crack propagation in a linear fracture mechanics although it is expressed with micro- and macrostructures. Obtained is a good agreement between theoretical and experimental data

  20. Elastic-plastic fracture mechanics study of thermal shock cracking

    International Nuclear Information System (INIS)

    Hirano, K.; Kobayashi, H.; Nakazawa, H.

    1980-01-01

    This paper describes thermal shock experiments conducted on a nuclear pressure vessel steel (A533 Grade B Class 1), an AISI304 steel and a tool steel (JIS SKD62) using both a new thermal shock test facility and method. Analysis of their quasi-static thermal stress intensity factors is performed on the basis of linear-elastic fracture mechanics; and a thermal shock fracture toughness value, Ksub(tsc) is evaluated. Then elastic-plastic fracture toughness tests are carried out in the same high temperature range of the thermal shock experiment, and a relation between the stretched zone width, SZW, formed as a result of the fatigue precrack tip plastic blunting and the J-integral is clarified. An elastic-plastic thermal shock fracture toughness value, Jsub(tsc), is evaluated from a critical value of the stretched zone width, SZWsub(tsc), at the initiation of the thermal shock cracking by using the relation between SZW and J. The Jsub(tsc) value is compared with an elastic-plastic fracture toughness value, Jsub(Ic), and the difference between these Jsub(tsc) and Jsub(Ic) values is discussed on the basis of fractography. (author)

  1. Effect of hydro mechanical coupling on natural fracture network formation in sedimentary basins

    Science.gov (United States)

    Ouraga, Zady; Guy, Nicolas; Pouya, Amade

    2018-05-01

    In sedimentary basin context, numerous phenomena, depending on the geological time span, can result in natural fracture network formation. In this paper, fracture network and dynamic fracture spacing triggered by significant sedimentation rate are studied considering mode I fracture propagation using a coupled hydro-mechanical numerical methods. The focus is put on synthetic geological structure under a constant sedimentation rate on its top. This model contains vertical fracture network initially closed and homogeneously distributed. The fractures are modelled with cohesive zone model undergoing damage and the flow is described by Poiseuille's law. The effect of the behaviour of the rock is studied and the analysis leads to a pattern of fracture network and fracture spacing in the geological layer.

  2. OCA-P, PWR Vessel Probabilistic Fracture Mechanics

    International Nuclear Information System (INIS)

    Cheverton, R.D.; Ball, D.G.

    2001-01-01

    1 - Description of program or function: OCA-P is a probabilistic fracture-mechanics code prepared specifically for evaluating the integrity of pressurized-water reactor vessels subjected to overcooling-accident loading conditions. Based on linear-elastic fracture mechanics, it has two- and limited three-dimensional flaw capability, and can treat cladding as a discrete region. Both deterministic and probabilistic analyses can be performed. For deterministic analysis, it is possible to conduct a search for critical values of the fluence and the nil-ductility reference temperature corresponding to incipient initiation of the initial flaw. The probabilistic portion of OCA-P is based on Monte Carlo techniques, and simulated parameters include fluence, flaw depth, fracture toughness, nil-ductility reference temperature, and concentrations of copper, nickel, and phosphorous. Plotting capabilities include the construction of critical-crack-depth diagrams (deterministic analysis) and a variety of histograms (probabilistic analysis). 2 - Method of solution: OAC-P accepts as input the reactor primary- system pressure and the reactor pressure-vessel downcomer coolant temperature, as functions of time in the specified transient. Then, the wall temperatures and stresses are calculated as a function of time and radial position in the wall, and the fracture-mechanics analysis is performed to obtain the stress intensity factors as a function of crack depth and time in the transient. In a deterministic analysis, values of the static crack initiation toughness and the crack arrest toughness are also calculated for all crack depths and times in the transient. A comparison of these values permits an evaluation of flaw behavior. For a probabilistic analysis, OCA-P generates a large number of reactor pressure vessels, each with a different combination of the various values of the parameters involved in the analysis of flaw behavior. For each of these vessels, a deterministic fracture

  3. Development of probabilistic fracture mechanics code PASCAL and user's manual

    Energy Technology Data Exchange (ETDEWEB)

    Shibata, Katsuyuki; Onizawa, Kunio [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Li, Yinsheng; Kato, Daisuke [Fuji Research Institute Corporation, Tokyo (Japan)

    2001-03-01

    As a part of the aging and structural integrity research for LWR components, a new PFM (Probabilistic Fracture Mechanics) code PASCAL (PFM Analysis of Structural Components in Aging LWR) has been developed since FY1996. This code evaluates the failure probability of an aged reactor pressure vessel subjected to transient loading such as PTS (Pressurized Thermal Shock). The development of the code has been aimed to improve the accuracy and reliability of analysis by introducing new analysis methodologies and algorithms considering the recent development in the fracture mechanics methodologies and computer performance. The code has some new functions in optimized sampling and cell dividing procedure in stratified Monte Carlo simulation, elastic-plastic fracture criterion of R6 method, extension analysis models in semi-elliptical crack, evaluation of effect of thermal annealing and etc. In addition, an input data generator of temperature and stress distribution time histories was also prepared in the code. Functions and performance of the code have been confirmed based on the verification analyses and some case studies on the influence parameters. The present phase of the development will be completed in FY2000. Thus this report provides the user's manual and theoretical background of the code. (author)

  4. Micro-mechanical analysis and modelling of the behavior and brittle fracture of a french 16MND5 steel: role of microstructural heterogeneities

    International Nuclear Information System (INIS)

    Mathieu, J.Ph.

    2006-10-01

    Reactor Pressure Vessel is the second containment barrier between nuclear fuel and the environment. Electricite de France's reactors are made with french 16MND5 low-alloyed steel (equ. ASTM A508 Cl.3). Various experimental techniques (scanning electron microscopy, X-ray diffraction...) are set up in order to characterize mechanical heterogeneities inside material microstructure during tensile testing at different low temperatures [-150 C;-60 C]. Heterogeneities can be seen as the effect of both 'polycrystalline' and 'composite' microstructural features. Interphase (until 150 MPa in average between ferritic and bainitic macroscopic stress state) and intra-phase (until 100 MPa in average between ferritic orientations) stress variations are highlighted. Modelling involves micro-mechanical description of plastic glide, mean fields models and realistic three-dimensional aggregates, all put together inside a multi-scale approach. Calibration is done on macroscopic stress-strain curves at different low temperatures, and modelling reproduces experimental stress heterogeneities. This modelling allows to apply a local micro-mechanical fracture criterion for crystallographic cleavage. Deterministic computations of time to fracture for different carbides random selection provide a way to express probability of fracture for the elementary volume. Results are in good agreement with hypothesis made by local approach to fracture. Hence, the main difference is that no dependence to loading nor microstructure features is supposed for probability of fracture on the representative volume: this dependence is naturally introduced by modelling. (author)

  5. Thermal hydraulic-Mechanic Integrated Simulation for Advanced Cladding Thermal Shock Fracture Analysis during Reflood Phase in LBLOCA

    Energy Technology Data Exchange (ETDEWEB)

    Son, Seong Min; Lee, You Ho; Cho, Jae Wan; Lee, Jeong Ik [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    This study suggested thermal hydraulic-mechanical integrated stress based methodology for analyzing the behavior of ATF type claddings by SiC-Duplex cladding LBLOCA simulation. Also, this paper showed that this methodology could predict real experimental result well. That concept for enhanced safety of LWR called Advanced Accident-Tolerance Fuel Cladding (ATF cladding, ATF) is researched actively. However, current nuclear fuel cladding design criteria for zircaloy cannot be apply to ATF directly because those criteria are mainly based on limiting their oxidation. So, the new methodology for ATF design criteria is necessary. In this study, stress based analysis methodology for ATF cladding design criteria is suggested. By simulating LBLOCA scenario of SiC cladding which is the one of the most promising candidate of ATF. Also we'll confirm our result briefly through comparing some facts from other experiments. This result is validating now. Some of results show good performance with 1-D failure analysis code for SiC fuel cladding that already developed and validated by Lee et al,. It will present in meeting. Furthermore, this simulation presented the possibility of understanding the behavior of cladding deeper. If designer can predict the dangerous region and the time precisely, it may be helpful for designing nuclear fuel cladding geometry and set safety criteria.

  6. Technical report on micro-mechanical versus conventional modelling in non-linear fracture mechanics

    International Nuclear Information System (INIS)

    2001-07-01

    While conventional fracture mechanics is capable of predicting crack growth behaviour if sufficient experimental observations are available, micro-mechanical modelling can both increase the accuracy of these predictions and model phenomena that are inaccessible by the conventional theory such as the ductile-cleavage temperature transition. A common argument against micro-mechanical modelling is that it is too complicated for use in routine engineering applications. This is both a computational and an educational problem. That micro-mechanical modelling is unnecessarily complicated is certainly true in many situations. The on-going development of micro-mechanical models, computational algorithms and computer speed will however most probably diminish the computational problem rather rapidly. Compare for instance the rate of development of computational methods for structural analysis. Meanwhile micro-mechanical modelling may serve as a tool by which more simplified engineering methods can be validated. The process of receiving a wide acceptance of the new methods is probably much slower. This involves many steps. First the research community must be in reasonable agreement on the methods and their use. Then the methods have to be implemented into computer software and into code procedures. The development and acceptance of conventional fracture mechanics may serve as an historical example of the time required before a new methodology has received a wide usage. The CSNI Working Group on Integrity and Ageing (IAGE) decided to carry out a report on micro-mechanical modeling to promote this promising and valuable technique. The report presents a comparison with non-linear fracture mechanics and highlights key aspects that could lead to a better knowledge and accurate predictions. Content: - 1. Introduction; - 2. Concepts of non-linear fracture mechanics with point crack tip modelling; - 3. Micro-mechanical models for cleavage fracture; - 4, Micro-mechanical modelling of

  7. Fracture mechanics performance of UF6 containers

    International Nuclear Information System (INIS)

    Gonzalez, M.E.; Iorio, A.F.; Crespi, J.C.

    1993-01-01

    The main purpose of this work was to determine the fracture mechanics performance of UF 6 transport cylinders type ANSI N14.1.30B, which was made from ASTM A 516 Grade 70 steel. It was assumed an internal surface axial crack subjected to stresses due to service, proof and transport accident loads. The KUMAR-GERMAN-SHIH elastoplastic methodology gave adequate results for crack depth estimation. The results validate the leak-before-break criteria for service and proof conditions but not for accident ones. In the last case a non-destructive examination must be done in order to assure the absence of defects larger than one third of the cylinder wall thickness. (Author)

  8. Numerical modelling in non linear fracture mechanics

    Directory of Open Access Journals (Sweden)

    Viggo Tvergaard

    2007-07-01

    Full Text Available Some numerical studies of crack propagation are based on using constitutive models that accountfor damage evolution in the material. When a critical damage value has been reached in a materialpoint, it is natural to assume that this point has no more carrying capacity, as is done numerically in the elementvanish technique. In the present review this procedure is illustrated for micromechanically based materialmodels, such as a ductile failure model that accounts for the nucleation and growth of voids to coalescence, and a model for intergranular creep failure with diffusive growth of grain boundary cavities leading to micro-crack formation. The procedure is also illustrated for low cycle fatigue, based on continuum damage mechanics. In addition, the possibility of crack growth predictions for elastic-plastic solids using cohesive zone models to represent the fracture process is discussed.

  9. State-of-the-art report on piping fracture mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Wilkowski, G.M.; Olson, R.J.; Scott, P.M. [Battelle, Columbus, OH (United States)

    1998-01-01

    This report is an in-depth summary of the state-of-the-art in nuclear piping fracture mechanics. It represents the culmination of 20 years of work done primarily in the US, but also attempts to include important aspects from other international efforts. Although the focus of this work was for the nuclear industry, the technology is also applicable in many cases to fossil plants, petrochemical/refinery plants, and the oil and gas industry. In compiling this detailed summary report, all of the equations and details of the analysis procedure or experimental results are not necessarily included. Rather, the report describes the important aspects and limitations, tells the reader where he can go for further information, and more importantly, describes the accuracy of the models. Nevertheless, the report still contains over 150 equations and over 400 references. The main sections of this report describe: (1) the evolution of piping fracture mechanics history relative to the developments of the nuclear industry, (2) technical developments in stress analyses, material property aspects, and fracture mechanics analyses, (3) unresolved issues and technically evolving areas, and (4) a summary of conclusions of major developments to date.

  10. State-of-the-art report on piping fracture mechanics

    International Nuclear Information System (INIS)

    Wilkowski, G.M.; Olson, R.J.; Scott, P.M.

    1998-01-01

    This report is an in-depth summary of the state-of-the-art in nuclear piping fracture mechanics. It represents the culmination of 20 years of work done primarily in the US, but also attempts to include important aspects from other international efforts. Although the focus of this work was for the nuclear industry, the technology is also applicable in many cases to fossil plants, petrochemical/refinery plants, and the oil and gas industry. In compiling this detailed summary report, all of the equations and details of the analysis procedure or experimental results are not necessarily included. Rather, the report describes the important aspects and limitations, tells the reader where he can go for further information, and more importantly, describes the accuracy of the models. Nevertheless, the report still contains over 150 equations and over 400 references. The main sections of this report describe: (1) the evolution of piping fracture mechanics history relative to the developments of the nuclear industry, (2) technical developments in stress analyses, material property aspects, and fracture mechanics analyses, (3) unresolved issues and technically evolving areas, and (4) a summary of conclusions of major developments to date

  11. Results of fracture mechanics tests on PNC SUS 304 plate

    International Nuclear Information System (INIS)

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

    1985-08-01

    PNC provided SUS 304 plate to be irradiated in FFTF at about 400 0 C to a target fluence of 5 x 10 21 n/cm 2 (E > 0.1 MeV). The actual irradiation included two basically different exposure levels to assure that information would be available for the exposure of interest. After irradiation, tensile properties, fatigue-crack growth rates and J-integral fracture toughness response were determined. These same properties were also measured for the unirradiated material so radiation damage effects could be characterized. This report presents the results of this program. It is expected that these results would be applicable for detailed fracture analysis of reactor components. Recent advances in elastic-plastic fracture mechanics enable reasonably accurate predictions of failure conditions for flawed stainless steel components. Extensive research has focused on the development of J-integral-based engineering approach for assessing the load carrying capacity of low-strength, high-toughness structural materials. Furthermore, Kanninen, et al., have demonstrated that J-integral concepts can accurately predict the fracture response for full-scale cracked structures manufactured from Type 304 stainless steel

  12. Fracture mechanics of concrete : Will applications start to emerge?

    NARCIS (Netherlands)

    Van Mier, J.G.M.

    1995-01-01

    Fracture mechanics of concrete has developed into an active field of research in the past decades. It promises a rational solution technique to structural problems in reinforced concrete in the limit state. Numerical tools have been developed on the basis of fracture mechanics theories. The question

  13. (Environmental and geophysical modeling, fracture mechanics, and boundary element methods)

    Energy Technology Data Exchange (ETDEWEB)

    Gray, L.J.

    1990-11-09

    Technical discussions at the various sites visited centered on application of boundary integral methods for environmental modeling, seismic analysis, and computational fracture mechanics in composite and smart'' materials. The traveler also attended the International Association for Boundary Element Methods Conference at Rome, Italy. While many aspects of boundary element theory and applications were discussed in the papers, the dominant topic was the analysis and application of hypersingular equations. This has been the focus of recent work by the author, and thus the conference was highly relevant to research at ORNL.

  14. Finnie's notes on fracture mechanics fundamental and practical lessons

    CERN Document Server

    Dharan, C K H; Finnie, Iain

    2016-01-01

    This textbook consists primarily of notes by Iain Finnie who taught a popular course on fracture mechanics at the University of California at Berkeley. It presents a comprehensive and detailed exposition of fracture, the fundamentals of fracture mechanics and procedures for the safe design of engineering components made from metal alloys, brittle materials like glasses and ceramics, and composites. Interesting and practical problems are listed at the end of most chapters to give the student practice in applying the theory. A solutions manual is provided to the instructor. The text presents a unified perspective of fracture with a strong fundamental foundation and practical applications. In addition to its role as a text, this reference would be invaluable for the practicing engineer who is involved in the design and evaluation of components that are fracture critical. This book also: Presents details of derivations of the basic equations of fracture mechanics and the historical context of the development of f...

  15. Dependence of fracture mechanical and fluid flow properties on fracture roughness and sample size

    International Nuclear Information System (INIS)

    Tsang, Y.W.; Witherspoon, P.A.

    1983-01-01

    A parameter study has been carried out to investigate the interdependence of mechanical and fluid flow properties of fractures with fracture roughness and sample size. A rough fracture can be defined mathematically in terms of its aperture density distribution. Correlations were found between the shapes of the aperture density distribution function and the specific fractures of the stress-strain behavior and fluid flow characteristics. Well-matched fractures had peaked aperture distributions that resulted in very nonlinear stress-strain behavior. With an increasing degree of mismatching between the top and bottom of a fracture, the aperture density distribution broadened and the nonlinearity of the stress-strain behavior became less accentuated. The different aperture density distributions also gave rise to qualitatively different fluid flow behavior. Findings from this investigation make it possible to estimate the stress-strain and fluid flow behavior when the roughness characteristics of the fracture are known and, conversely, to estimate the fracture roughness from an examination of the hydraulic and mechanical data. Results from this study showed that both the mechanical and hydraulic properties of the fracture are controlled by the large-scale roughness of the joint surface. This suggests that when the stress-flow behavior of a fracture is being investigated, the size of the rock sample should be larger than the typical wave length of the roughness undulations

  16. Complexity: a new paradigm for fracture mechanics

    Directory of Open Access Journals (Sweden)

    S. Puzzi

    2009-10-01

    Full Text Available The so-called Complexity Sciences are a topic of fast growing interest inside the scientific community. Actually, researchers did not come to a definition of complexity, since it manifests itself in so many different ways [1]. This field itself is not a single discipline, but rather a heterogeneous amalgam of different techniques of mathematics and science. In fact, under the label of Complexity Sciences we comprehend a large variety of approaches: nonlinear dynamics, deterministic chaos theory, nonequilibrium thermodynamics, fractal geometry, intermediate asymptotics, complete and incomplete similarity, renormalization group theory, catastrophe theory, self-organized criticality, neural networks, cellular automata, fuzzy logic, etc. Aim of this paper is at providing insight into the role of complexity in the field of Materials Science and Fracture Mechanics [2-3]. The presented examples will be concerned with the snap-back instabilities in the structural behaviour of composite structures (Carpinteri [4-6], the occurrence of fractal patterns and selfsimilarity in material damage and deformation of heterogeneous materials, and the apparent scaling on the nominal mechanical properties of disordered materials (Carpinteri [7,8]. Further examples will deal with criticality in the acoustic emissions of damaged structures and with scaling in the time-to-failure (Carpinteri et al. [9]. Eventually, results on the transition towards chaos in the dynamics of cracked beams will be reported (Carpinteri and Pugno [10,11].

  17. Fracture mechanics behaviour of neutron irradiated Alloy A-286

    International Nuclear Information System (INIS)

    Mills, W.J.; James, L.A.

    The effect of fast-neutron irradiation on the fatigue-crack propagation and fracture toughness behaviour of Alloy A-286 was characterized using fracture mechanics techniques. The fracture toughness was found to decrease continuously with increasing irradiation damage at both 24 deg. C and 427 deg. C. In the unirradiated and low fluence conditions, specimens displayed appreciable plasticity prior to fracture, and equivalent Ksub(Ic) values were determined from Jsub(Ic) fracture toughness results. At high irradiation exposure levels, specimens exhibited a brittle Ksub(Ic) fracture mode. The 427 deg. C fracture toughness fell from 129 MPa√m in the unirradiated condition to 35 MPa√m at an exposure of 16.2 dpa (total fluence of 5.2x10 22 n/cm 2 ). Room temperature fracture toughness values were consistently 40 to 60 percent higher than the 427 deg. C values. Electron fractography revealed that the reduction in fracture resistance was attributed to a fracture mechanism transition from ductile microvoid coalescence to channel fracture. Fatigue-crack propagation tests were conducted at 427 deg. C on specimens irradiated at 2.4 dpa and 16.2 dpa. Crack growth rates at the lower exposure level were comparable to those in unirradiated material, while those at the higher exposure were slightly higher than in unirradiated material. (author)

  18. Mechanical design optimization of bioabsorbable fixation devices for bone fractures.

    Science.gov (United States)

    Lovald, Scott T; Khraishi, Tariq; Wagner, Jon; Baack, Bret

    2009-03-01

    Bioabsorbable bone plates can eliminate the necessity for a permanent implant when used to fixate fractures of the human mandible. They are currently not in widespread use because of the low strength of the materials and the requisite large volume of the resulting bone plate. The aim of the current study was to discover a minimally invasive bioabsorbable bone plate design that can provide the same mechanical stability as a standard titanium bone plate. A finite element model of a mandible with a fracture in the body region is subjected to bite loads that are common to patients postsurgery. The model is used first to determine benchmark stress and strain values for a titanium plate. These values are then set as the limits within which the bioabsorbable bone plate must comply. The model is then modified to consider a bone plate made of the polymer poly-L/DL-lactide 70/30. An optimization routine is run to determine the smallest volume of bioabsorbable bone plate that can perform and a titanium bone plate when fixating fractures of this considered type. Two design parameters are varied for the bone plate design during the optimization analysis. The analysis determined that a strut style poly-L-lactide-co-DL-lactide plate of 690 mm2 can provide as much mechanical stability as a similar titanium design structure of 172 mm2. The model has determined a bioabsorbable bone plate design that is as strong as a titanium plate when fixating fractures of the load-bearing mandible. This is an intriguing outcome, considering that the polymer material has only 6% of the stiffness of titanium.

  19. Fluid driven fracture mechanics in highly anisotropic shale: a laboratory study with application to hydraulic fracturing

    Science.gov (United States)

    Gehne, Stephan; Benson, Philip; Koor, Nick; Enfield, Mark

    2017-04-01

    The finding of considerable volumes of hydrocarbon resources within tight sedimentary rock formations in the UK led to focused attention on the fundamental fracture properties of low permeability rock types and hydraulic fracturing. Despite much research in these fields, there remains a scarcity of available experimental data concerning the fracture mechanics of fluid driven fracturing and the fracture properties of anisotropic, low permeability rock types. In this study, hydraulic fracturing is simulated in a controlled laboratory environment to track fracture nucleation (location) and propagation (velocity) in space and time and assess how environmental factors and rock properties influence the fracture process and the developing fracture network. Here we report data on employing fluid overpressure to generate a permeable network of micro tensile fractures in a highly anisotropic shale ( 50% P-wave velocity anisotropy). Experiments are carried out in a triaxial deformation apparatus using cylindrical samples. The bedding planes are orientated either parallel or normal to the major principal stress direction (σ1). A newly developed technique, using a steel guide arrangement to direct pressurised fluid into a sealed section of an axially drilled conduit, allows the pore fluid to contact the rock directly and to initiate tensile fractures from the pre-defined zone inside the sample. Acoustic Emission location is used to record and map the nucleation and development of the micro-fracture network. Indirect tensile strength measurements at atmospheric pressure show a high tensile strength anisotropy ( 60%) of the shale. Depending on the relative bedding orientation within the stress field, we find that fluid induced fractures in the sample propagate in two of the three principal fracture orientations: Divider and Short-Transverse. The fracture progresses parallel to the bedding plane (Short-Transverse orientation) if the bedding plane is aligned (parallel) with the

  20. Two-parameter fracture mechanical analysis of a near-crack-tip stress field in wedge splitting test specimens

    Czech Academy of Sciences Publication Activity Database

    Seitl, Stanislav; Veselý, V.; Řoutil, L.

    2011-01-01

    Roč. 89, 21-22 (2011), s. 1852-1858 ISSN 0045-7949. [International Conference on Civil, Structural and Enviromental Engineering Computing /12./. Funchal, Madeira, 01.09.2009-04.09.2009] Institutional research plan: CEZ:AV0Z20410507 Keywords : Wedge splitting test * Stress intensity factor * T-stress * Numerical simulation * Direct method Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.874, year: 2011

  1. Integration of NDE Reliability and Fracture Mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Becker, F. L.; Doctor, S. R.; Heas!er, P. G.; Morris, C. J.; Pitman, S. G.; Selby, G. P.; Simonen, F. A.

    1981-03-01

    The Pacific Northwest Laboratory is conducting a four-phase program for measuring and evaluating the effectiveness and reliability of in-service inspection (lSI} performed on the primary system piping welds of commercial light water reactors (LWRs). Phase I of the program is complete. A survey was made of the state of practice for ultrasonic rsr of LWR primary system piping welds. Fracture mechanics calculations were made to establish required nondestrutive testing sensitivities. In general, it was found that fatigue flaws less than 25% of wall thickness would not grow to failure within an inspection interval of 10 years. However, in some cases failure could occur considerably faster. Statistical methods for predicting and measuring the effectiveness and reliability of lSI were developed and will be applied in the "Round Robin Inspections" of Phase II. Methods were also developed for the production of flaws typical of those found in service. Samples fabricated by these methods wilI be used in Phase II to test inspection effectiveness and reliability. Measurements were made of the influence of flaw characteristics {i.e., roughness, tightness, and orientation) on inspection reliability. These measurernents, as well as the predictions of a statistical model for inspection reliability, indicate that current reporting and recording sensitivities are inadequate.

  2. Correlation analysis of fracture arrangement in space

    Science.gov (United States)

    Marrett, Randall; Gale, Julia F. W.; Gómez, Leonel A.; Laubach, Stephen E.

    2018-03-01

    We present new techniques that overcome limitations of standard approaches to documenting spatial arrangement. The new techniques directly quantify spatial arrangement by normalizing to expected values for randomly arranged fractures. The techniques differ in terms of computational intensity, robustness of results, ability to detect anti-correlation, and use of fracture size data. Variation of spatial arrangement across a broad range of length scales facilitates distinguishing clustered and periodic arrangements-opposite forms of organization-from random arrangements. Moreover, self-organized arrangements can be distinguished from arrangements due to extrinsic organization. Traditional techniques for analysis of fracture spacing are hamstrung because they account neither for the sequence of fracture spacings nor for possible coordination between fracture size and position, attributes accounted for by our methods. All of the new techniques reveal fractal clustering in a test case of veins, or cement-filled opening-mode fractures, in Pennsylvanian Marble Falls Limestone. The observed arrangement is readily distinguishable from random and periodic arrangements. Comparison of results that account for fracture size with results that ignore fracture size demonstrates that spatial arrangement is dominated by the sequence of fracture spacings, rather than coordination of fracture size with position. Fracture size and position are not completely independent in this example, however, because large fractures are more clustered than small fractures. Both spatial and size organization of veins here probably emerged from fracture interaction during growth. The new approaches described here, along with freely available software to implement the techniques, can be applied with effect to a wide range of structures, or indeed many other phenomena such as drilling response, where spatial heterogeneity is an issue.

  3. Piping reliability analysis: Some views on the roles of data-driven models vs. probabilistic fracture mechanics (PFM)

    International Nuclear Information System (INIS)

    Lydell, B.

    1997-01-01

    The objective of the presentation is to address the question in five different perspectives: Historical; Methodological; Quality PSA and the specifications for pipe rupture frequency estimation -verification and validation; User-perspectives on frequency estimation; data analysis perspectives on the choice of estimation technique

  4. Fractographic analysis of fractured dental implant components

    Directory of Open Access Journals (Sweden)

    Chih-Ling Chang

    2013-03-01

    Conclusion: To avoid implant fracture, certain underlying mechanical risk factors should be noted such as patients with a habit of bruxism, bridgework with a cantilever design, or two implants installed in a line in the posterior mandible.

  5. Concepts and possibilities of fracture mechanics for fracture safety assessment

    International Nuclear Information System (INIS)

    Blauel, J.

    1980-01-01

    In very tough materials for pressure vessels and pipelines of nuclear plants, cracking begins in a stable manner and only after macroscopic plastic deformations and crack blunting. It is possible to describe this elasto-plastic fracture behaviour and to quantify the safety margin compared to the assessment criteria based on linear elastic stressing and initiation by the concept of the J integral, the crack peak width and the crack resistance Jsub(R) curve. The numerous problems of details still open and the partly very limited validity range should not prevent the further investigation into the great possibilities of this concept and making greater use of the interpretation of large scale tests. (orig./RW) [de

  6. Analysis of damage processes in short glass fibre reinforced polyamide under mechanical loading by X-ray refractometry, fracture mechanics and fractography; Analyse der Schaedigungsprozesse in einem kurzglasfaserverstaerkten Polyamid unter mechanischer Belastung mittels Roentgenrefraktometrie, Bruchmechanik und Fraktografie

    Energy Technology Data Exchange (ETDEWEB)

    Guenzel, Stephan

    2013-04-01

    This thesis presents an analysis of the damage behaviour in a short glass fibre reinforced polyamide. The micro cracking is investigated by X-ray refraction technique under various, mechanical in-service loadings. In this context, potentials and limits of X-ray refraction analysis for short glass fibre reinforced polyamides are compiled. In particular the influence of fibre orientation and the influence of damage mechanisms are examined according to the X-ray refraction analysis and its interpretation. The method offers a quantitative and phenomenological based characterisation of micro crack damage. For the investigated material micro crack damage emerges as fibre matrix debonding and matrix micro cracking. The state of damage correlates with a nonlinear strain portion in a linear manner and depends on the kind of loading. Absorption of moisture in the material may influence significantly the micro crack damage behaviour. Damage of micro cracking appears preferentially under tension. The macro damage due to propagation of a single crack is characterised in an automated test setup, considering the fibre orientation and content of moisture. Based on the findings an empirical assessment approach is developed. The investigations of the micro and macro damage behaviour are accompanied by fractography, in order to support the model assumptions according to damage and fracture mechanisms.

  7. In situ grain fracture mechanics during uniaxial compaction of granular solids

    Science.gov (United States)

    Hurley, R. C.; Lind, J.; Pagan, D. C.; Akin, M. C.; Herbold, E. B.

    2018-03-01

    Grain fracture and crushing are known to influence the macroscopic mechanical behavior of granular materials and be influenced by factors such as grain composition, morphology, and microstructure. In this paper, we investigate grain fracture and crushing by combining synchrotron x-ray computed tomography and three-dimensional x-ray diffraction to study two granular samples undergoing uniaxial compaction. Our measurements provide details of grain kinematics, contacts, average intra-granular stresses, inter-particle forces, and intra-grain crystal and fracture plane orientations. Our analyses elucidate the complex nature of fracture and crushing, showing that: (1) the average stress states of grains prior to fracture vary widely in their relation to global and local trends; (2) fractured grains experience inter-particle forces and stored energies that are statistically higher than intact grains prior to fracture; (3) fracture plane orientations are primarily controlled by average intra-granular stress and contact fabric rather than the orientation of the crystal lattice; (4) the creation of new surfaces during fracture accounts for a very small portion of the energy dissipated during compaction; (5) mixing brittle and ductile grain materials alters the grain-scale fracture response. The results highlight an application of combined x-ray measurements for non-destructive in situ analysis of granular solids and provide details about grain fracture that have important implications for theory and modeling.

  8. Fracture mechanics parameters for glasses: A compilation and correlation

    International Nuclear Information System (INIS)

    Freiman, S.W.; Baker, T.L.; Wachtmann, J.B.

    1985-01-01

    This paper describes a computerized fracture mechanics data base and associated computer programs which permit extension and modification of data base as well as selection, plotting and curve fitting. Some preliminary results of correlations of fracture energy, gamma, with composition and elastic modulus are presented

  9. Sedimentary facies control on mechanical and fracture stratigraphy in turbidites

    NARCIS (Netherlands)

    Ogata, Kei; Storti, Fabrizio; Balsamo, Fabrizio; Tinterri, Roberto; Bedogni, Enrico; Fetter, Marcos; Gomes, Leonardo; Hatushika, Raphael

    2017-01-01

    Natural fracture networks exert a first-order control on the exploitation of resources such as aquifers, hydrocarbons, and geothermal reservoirs, and on environmental issues like underground gas storage and waste disposal. Fractures and the mechanical stratigraphy of layered sequences have been

  10. Fracture mechanics and statistical mechanics of reinforced elastomeric blends

    CERN Document Server

    Heinrich, Gert; Kaliske, Michael; Klüppel, Manfred; Schneider, Konrad; Vilgis, Thomas

    2013-01-01

    Elastomers are found in many applications ranging from technology to daily life applications for example in tires, drive systems, sealings and print rollers. Dynamical operation conditions put extremely high demands on the performance and stability of these materials and their elastic and flow properties can be easily adjusted by simple manipulations on their elastic and viscous properties. However, the required service life suffers often from material damage as a result of wear processes such as abrasion and wear fatigue, mostly caused by crack formation and propagation. This book covers interdisciplinary research between physics, physical chemistry, material sciences and engineering of elastomers within the range from nanometres to millimetres and connects these aspects with the constitutive material properties. The different chapters describe reliable lifetime and durability predictions based on new fracture mechanical testing concepts and advanced material-theoretical methods which are finally implemented...

  11. Fracture mechanics as judgement criterion in reference publications

    International Nuclear Information System (INIS)

    Bartholome, G.

    1976-01-01

    Fracture mechanics is applied in particular in ship and aeroplane construction, in astronautics, and in nuclear engineering. Around 1950, the high quality demands in nuclear engineering led to the first regulation for brittle-fracture-safe operation of thick-walled nuclear pressure vessels. These regulations are based on the brittle-fracture-plan (NDT concept). For reactor engineering this plan is applied in a simplified way, the so-called modified PORSE-diagram. The permissible operational stresses must be out of the range of brittle fracture margin which is defined by the NDT temperature extension limit. (RW) [de

  12. Linking advanced fracture models to structural analysis

    Energy Technology Data Exchange (ETDEWEB)

    Chiesa, Matteo

    2001-07-01

    Shell structures with defects occur in many situations. The defects are usually introduced during the welding process necessary for joining different parts of the structure. Higher utilization of structural materials leads to a need for accurate numerical tools for reliable prediction of structural response. The direct discretization of the cracked shell structure with solid finite elements in order to perform an integrity assessment of the structure in question leads to large size problems, and makes such analysis infeasible in structural application. In this study a link between local material models and structural analysis is outlined. An ''ad hoc'' element formulation is used in order to connect complex material models to the finite element framework used for structural analysis. An improved elasto-plastic line spring finite element formulation, used in order to take cracks into account, is linked to shell elements which are further linked to beam elements. In this way one obtain a global model of the shell structure that also accounts for local flexibilities and fractures due to defects. An important advantage with such an approach is a direct fracture mechanics assessment e.g. via computed J-integral or CTOD. A recent development in this approach is the notion of two-parameter fracture assessment. This means that the crack tip stress tri-axiality (constraint) is employed in determining the corresponding fracture toughness, giving a much more realistic capacity of cracked structures. The present thesis is organized in six research articles and an introductory chapter that reviews important background literature related to this work. Paper I and II address the performance of shell and line spring finite elements as a cost effective tool for performing the numerical calculation needed to perform a fracture assessment. In Paper II a failure assessment, based on the testing of a constraint-corrected fracture mechanics specimen under tension, is

  13. Small Crack Growth and Fatigue Life Predictions for High-Strength Aluminium Alloys. Part 1; Experimental and Fracture Mechanics Analysis

    Science.gov (United States)

    Wu, X. R.; Newman, J. C.; Zhao, W.; Swain, M. H.; Ding, C. F.; Phillips, E. P.

    1998-01-01

    The small crack effect was investigated in two high-strength aluminium alloys: 7075-T6 bare and LC9cs clad alloy. Both experimental and analytical investigations were conducted to study crack initiation and growth of small cracks. In the experimental program, fatigue tests, small crack and large crack tests A,ere conducted under constant amplitude and Mini-TWIST spectrum loading conditions. A pronounced small crack effect was observed in both materials, especially for the negative stress ratios. For all loading conditions, most of the fatigue life of the SENT specimens was shown to be crack propagation from initial material defects or from the cladding layer. In the analysis program, three-dimensional finite element and A weight function methods were used to determine stress intensity factors and to develop SIF equations for surface and corner cracks at the notch in the SENT specimens. A plastisity-induced crack-closure model was used to correlate small and large crack data, and to make fatigue life predictions, Predicted crack-growth rates and fatigue lives agreed well with experiments. A total fatigue life prediction method for the aluminum alloys was developed and demonstrated using the crack-closure model.

  14. Elastic-plastic fracture mechanics analysis of a pressure vessel with an axial outer surface flaw. Pt. 2

    International Nuclear Information System (INIS)

    Brocks, W.; Kuenecke, G.

    1989-06-01

    Continuing preceding investigations, a further elastic-plastic finite element analysis of a test vessel with a semi-elliptical axial outer surface crack has been performed. The variations of J and CTOD along the crack front and the stress state in the vicinity of the crack are presented. The applicability of analytical approaches to determine J is examined. The FE results are used to analyze the experimental data with respect to the validity of J-controlled crack growth. Local J R -curves of the surface flaw are compared with J R -curves of various specimens of different geometries. Again, it became evident that the local ductile crack growth and, especially, the developing 'canoe shape' of the surface crack cannot be described by a single resistance curve which is assumed to be a material property. A method described in a previous report to predict the ductile crack growth by using local J R -curves which depend on the triaxiality of the stress state did not result in a satisfactory outcome, in the present case. The presumed reasons will be discussed. (orig.) [de

  15. Effect of reference loads on fracture mechanics analysis of surface cracked pipe based on reference stress method

    International Nuclear Information System (INIS)

    Shim, Do Jun; Son, Beom Goo; Kim, Young Jin; Kim, Yun Jae

    2004-01-01

    To investigate relevance of the definition of the reference stress to estimate J and C * for surface crack problems, this paper compares FE J and C * results for surface cracked pipes with those estimated according to the reference stress approach using various definitions of the reference stress. Pipes with part circumferential inner surface crack and finite internal axial crack are considered, subject to internal pressure and global bending. The crack depth and aspect ratio are systematically varied. The reference stress is defined in four different ways using (I) the local limit load, (II) the global limit load, (III) the global limit load determined from the FE limit analysis, and (IV) the optimised reference load. It is found that the reference stress based on the local limit load gives overall excessively conservative estimates of J and C * . Use of the global limit load clearly reduces the conservatism, compared to that of the local limit load, although it can provide sometimes non-conservative estimates of J and C * . The use of the FE global limit load gives overall non-conservative estimates of J and C * . The reference stress based on the optimised reference load gives overall accurate estimates of J and C * , compared to other definitions of the reference stress. Based on the present finding, general guidance on the choice of the reference stress for surface crack problems is given

  16. Analysis of fracture patterns and local stress field variations in fractured reservoirs

    Science.gov (United States)

    Deckert, Hagen; Drews, Michael; Fremgen, Dominik; Wellmann, J. Florian

    2010-05-01

    A meaningful qualitative evaluation of permeabilities in fractured reservoirs in geothermal or hydrocarbon industry requires the spatial description of the existing discontinuity pattern within the area of interest and an analysis how these fractures might behave under given stress fields. This combined information can then be used for better estimating preferred fluid pathway directions within the reservoir, which is of particular interest for defining potential drilling sites. A description of the spatial fracture pattern mainly includes the orientation of rock discontinuities, spacing relationships between single fractures and their lateral extent. We have examined and quantified fracture patterns in several outcrops of granite at the Costa Brava, Spain, and in the Black Forest, Germany, for describing reservoir characteristics. For our analysis of fracture patterns we have used photogrammetric methods to create high-resolution georeferenced digital 3D images of outcrop walls. The advantage of this approach, compared to conventional methods for fracture analysis, is that it provides a better 3D description of the fracture geometry as the entity of position, extent and orientation of single fractures with respect to their surrounding neighbors is conserved. Hence for instance, the method allows generating fracture density maps, which can be used for a better description of the spatial distribution of discontinuities in a given outcrop. Using photogrammetric techniques also has the advantage to acquire very large data sets providing statistically sound results. To assess whether the recorded discontinuities might act as fluid pathways information on the stress field is needed. A 3D model of the regional tectonic structure was created and the geometry of the faults was put into a mechanical 3D Boundary Element (BE) Model. The model takes into account the elastic material properties of the geological units and the orientation of single fault segments. The

  17. Experimental-numerical analysis of the fracture mechanic in polymeric materials; Analisis numerico-experimental de la mecanica de la fractura en materiales polimeros

    Energy Technology Data Exchange (ETDEWEB)

    Beltran Fernandez, Juan Alfonso; Hernandez Gomez, Luis H; Urriolagoitia Calderon, Guillermo; Villa y Rabasa, Gabriel; Rodriguez, Gustavo Ricardo; Mendoza Nunez, Maribel A [Instituto Politecnico Nacional, Zacatenco (Mexico)

    2004-10-15

    In this piece of work some fracture testings on specimens with a lateral fracture are made to analyze the resultant stress state around of the tip of the fracture and the way in which the strength of the material is modified to get the fracture toughness, to the load mode I. Also, it is explained the way in which mechanic properties were got in the Polymetil-Methacylate, (PMMA), such as: modulus of elasticity, maximum tensile stress, yielding stress and stress-unitary strain, stress-rate and strain-rate curves, throughout of the carry out of the tensile testing. With the objective to know the real mechanical behavior with the initial loading conditions established and different testing velocities. All and each one of the results are calculated experimental and numerically and validated throughout of the finite element method, using the software ANSYS 5.5.3. [Spanish] En este trabajo se efectuan pruebas de fractura en especimenes con una grieta lateral, para analizar el estado de esfuerzos resultantes alrededor de la punta de la grieta y la forma en que se afecta la resistencia del material a fin de obtener la tenacidad de fractura para el modo de carga I. Ademas, se explica la forma como se obtienen las propiedades mecanicas en el polimetil metacrilato (PMMA), tales como: modulo de elasticidad, esfuerzo normal maximo, esfuerzo de cadencia y las curvas esfuerzo-deformacion unitaria, esfuerzo-tiempo (stress-rate) y deformacion-tiempo (strain-rate), a traves de la realizacion de la prueba de tension. Se busca conocer el comportamiento mecanico real ante las condiciones de carga establecidas y a distintas velocidades de prueba. Todo y cada uno de los resultados se efectuan de manera experimental y son evaluados numericamente a traves del metodo del elemento finito, con el programa ANSYS 5.5.3.

  18. Yield fracture mechanics. Report colloquium of the DFG

    International Nuclear Information System (INIS)

    1992-01-01

    This volume contains 17 lectures, which were given at the Report Colloquium of the DFG at Bonn on November 5th 1992. The main points of yield fracture mechanics were: Theory, experiment technique, transferability, material and structure. (MM) [de

  19. Fracture Mechanics Prediction of Fatigue Life of Aluminum Highway Bridges

    DEFF Research Database (Denmark)

    Rom, Søren; Agerskov, Henning

    2015-01-01

    Fracture mechanics prediction of the fatigue life of aluminum highway bridges under random loading is studied. The fatigue life of welded joints has been determined from fracture mechanics analyses and the results obtained have been compared with results from experimental investigations. The fati......Fracture mechanics prediction of the fatigue life of aluminum highway bridges under random loading is studied. The fatigue life of welded joints has been determined from fracture mechanics analyses and the results obtained have been compared with results from experimental investigations...... against fatigue in aluminum bridges, may give results which are unconservative. Furthermore, it was in both investigations found that the validity of the results obtained from Miner's rule will depend on the distribution of the load history in tension and compression....

  20. ORNL probabilistic fracture-mechanics code OCA-P

    International Nuclear Information System (INIS)

    Cheverton, R.D.; Ball, D.G.

    1984-01-01

    The computer code OCA-P was developed at the request of the USNRC for the purpose of helping to evaluate the integrity of PWR pressure vessels during overcooling accidents (OCA's). The code can be used for both deterministic and probabilistic fracture-mechanics calculations, and consists essentially of OCA-II and a Monte Carlo routine similar to that developed by Strosnider et al. In the probabilistic mode OCA-P generates a large number of vessels (10 6 more or less), each with a different combination of the various values of the different parameters involved in the analysis of flaw behavior. For each of these vessels a deterministic fracture-mechanics analysis is performed (calculation of K/sub I/, K/sub Ic/, K/sub Ia/) to determine whether vessel failure takes place. The conditional probability of failure is simply the number of vessels that fail divided by the number of vessels generated. OCA-II is used for the deterministic analysis. Basic input to OCA-II includes, among other things, the primry-system pressure transient and the temperature transient for the coolant in the reactor-vessel downcomer. With this and additional information available OCA-II performs a one-dimensional thermal analysis to obtain the temperature distribution in the wall as a function of time and then a one-dimensional linear-elastic stress analysis. OCA-P has been checked against similar codes and is presently being used in the Integrated Pressurized Thermal Shock Program for specific PWR plants

  1. Analysis of compressive fracture in rock using statistical techniques

    Energy Technology Data Exchange (ETDEWEB)

    Blair, S.C.

    1994-12-01

    Fracture of rock in compression is analyzed using a field-theory model, and the processes of crack coalescence and fracture formation and the effect of grain-scale heterogeneities on macroscopic behavior of rock are studied. The model is based on observations of fracture in laboratory compression tests, and incorporates assumptions developed using fracture mechanics analysis of rock fracture. The model represents grains as discrete sites, and uses superposition of continuum and crack-interaction stresses to create cracks at these sites. The sites are also used to introduce local heterogeneity. Clusters of cracked sites can be analyzed using percolation theory. Stress-strain curves for simulated uniaxial tests were analyzed by studying the location of cracked sites, and partitioning of strain energy for selected intervals. Results show that the model implicitly predicts both development of shear-type fracture surfaces and a strength-vs-size relation that are similar to those observed for real rocks. Results of a parameter-sensitivity analysis indicate that heterogeneity in the local stresses, attributed to the shape and loading of individual grains, has a first-order effect on strength, and that increasing local stress heterogeneity lowers compressive strength following an inverse power law. Peak strength decreased with increasing lattice size and decreasing mean site strength, and was independent of site-strength distribution. A model for rock fracture based on a nearest-neighbor algorithm for stress redistribution is also presented and used to simulate laboratory compression tests, with promising results.

  2. Investigation of translaminar fracture in fibrereinforced composite laminates---applicability of linear elastic fracture mechanics and cohesive-zone model

    Science.gov (United States)

    Hou, Fang

    With the extensive application of fiber-reinforced composite laminates in industry, research on the fracture mechanisms of this type of materials have drawn more and more attentions. A variety of fracture theories and models have been developed. Among them, the linear elastic fracture mechanics (LEFM) and cohesive-zone model (CZM) are two widely-accepted fracture models, which have already shown applicability in the fracture analysis of fiber-reinforced composite laminates. However, there remain challenges which prevent further applications of the two fracture models, such as the experimental measurement of fracture resistance. This dissertation primarily focused on the study of the applicability of LEFM and CZM for the fracture analysis of translaminar fracture in fibre-reinforced composite laminates. The research for each fracture model consisted of two sections: the analytical characterization of crack-tip fields and the experimental measurement of fracture resistance parameters. In the study of LEFM, an experimental investigation based on full-field crack-tip displacement measurements was carried out as a way to characterize the subcritical and steady-state crack advances in translaminar fracture of fiber-reinforced composite laminates. Here, the fiber-reinforced composite laminates were approximated as anisotropic solids. The experimental investigation relied on the LEFM theory with a modification with respect to the material anisotropy. Firstly, the full-field crack-tip displacement fields were measured by Digital Image Correlation (DIC). Then two methods, separately based on the stress intensity approach and the energy approach, were developed to measure the crack-tip field parameters from crack-tip displacement fields. The studied crack-tip field parameters included the stress intensity factor, energy release rate and effective crack length. Moreover, the crack-growth resistance curves (R-curves) were constructed with the measured crack-tip field parameters

  3. Application of simulation techniques in the probabilistic fracture mechanics

    International Nuclear Information System (INIS)

    De Ruyter van Steveninck, J.L.

    1995-03-01

    The Monte Carlo simulation is applied on a model of the fracture mechanics in order to assess the applicability of this simulation technique in the probabilistic fracture mechanics. By means of the fracture mechanics model the brittle fracture of a steel container or pipe with defects can be predicted. By means of the Monte Carlo simulation also the uncertainty regarding failures can be determined. Based on the variations in the toughness of the fracture and the defect dimensions the distribution of the chance of failure is determined. Also attention is paid to the impact of dependency between uncertain variables. Furthermore, the influence of the applied distributions of the uncertain variables and non-destructive survey on the chance of failure is analyzed. The Monte Carlo simulation results agree quite well with the results of other methods from the probabilistic fracture mechanics. If an analytic expression can be found for the chance of failure, it is possible to determine the variation of the chance of failure, next to an estimation of the chance of failure. It also appears that the dependency between the uncertain variables has a large impact on the chance of failure. It is also concluded from the simulation that the chance of failure strongly depends on the crack depth, and therefore of the distribution of the crack depth. 15 figs., 7 tabs., 12 refs

  4. Elastic-plastic fracture mechanics of compact bone

    Science.gov (United States)

    Yan, Jiahau

    Bone is a composite composed mainly of organics, minerals and water. Most studies on the fracture toughness of bone have been conducted at room temperature. Considering that the body temperature of animals is higher than room temperature, and that bone has a high volumetric percentage of organics (generally, 35--50%), the effect of temperature on fracture toughness of bone should be studied. Single-edged V-shaped notched (SEVN) specimens were prepared to measure the fracture toughness of bovine femur and manatee rib in water at 0, 10, 23, 37 and 50°C. The fracture toughness of bovine femur and manatee rib were found to decrease from 7.0 to 4.3 MPa·m1/2 and from 5.5 to 4.1 MPa·m1/2, respectively, over a temperature range of 50°C. The decreases were attributed to inability of the organics to sustain greater stresses at higher temperatures. We studied the effects of water and organics on fracture toughness of bone using water-free and organics-free SEVN specimens at 23°C. Water-free and organics-free specimens were obtained by placing fresh bone specimen in a furnace at different temperatures. Water and organics significantly affected the fracture toughness of bone. Fracture toughness of the water-free specimens was 44.7% (bovine femur) and 32.4% (manatee rib) less than that of fresh-bone specimens. Fracture toughness of the organics-free specimens was 92.7% (bovine femur) and 91.5% (manatee rib) less than that of fresh bone specimens. Linear Elastic Fracture Mechanics (LEFM) is widely used to study bone. However, bone often has small to moderate scale yielding during testing. We used J integral, an elastic-plastic fracture-mechanics parameter, to study the fracture process of bone. The J integral of bovine femur increased from 6.3 KJ/mm2 at 23°C to 6.7 KJ/mm2 at 37°C. Although the fracture toughness of bovine bone decreases as the temperature increases, the J integral results show a contrary trend. The energy spent in advancing the crack beyond the linear

  5. Quantitative x-ray fractographic analysis of fatigue fractures

    International Nuclear Information System (INIS)

    Saprykin, Yu.V.

    1983-01-01

    The study deals with quantitative X-ray fractographic investigation of fatigue fractures of samples with sharp notches tested at various stresses and temperatures with the purpose of establishing a connection between material crack resistance parameters and local plastic instability zones restraining and controlling the crack growth. At fatigue fractures of notched Kh18N9T steel samples tested at +20 and -196 deg C a zone of sharp ring notch effect being analogous to the zone in which crack growth rate is controlled by the microshifting mechanisms is singled out. The size of the notched effect zone in the investigate steel is unambiguosly bound to to the stress amplitude. This provides the possibility to determine the stress value by the results of quantitative fractographic analysis of notched sample fractures. A possibility of determining one of the threshold values of cyclic material fracture toughness by the results of fatigue testing and fractography of notched sample fractures is shown. Correlation between the size of the hsub(s) crack effect zone in the notched sample, delta material yield limit and characteristic of cyclic Ksub(s) fracture toughness has been found. Such correlation widens the possibilities of quantitative diagnostics of fractures by the methods of X-ray fractography

  6. STAFAN, Fluid Flow, Mechanical Stress in Fractured Rock of Nuclear Waste Repository

    International Nuclear Information System (INIS)

    Huyakorn, P.; Golis, M.J.

    1989-01-01

    1 - Description of program or function: STAFAN (Stress And Flow Analysis) is a two-dimensional, finite-element code designed to model fluid flow and the interaction of fluid pressure and mechanical stresses in a fractured rock surrounding a nuclear waste repository. STAFAN considers flow behavior of a deformable fractured system with fracture-porous matrix interactions, the coupling effects of fluid pressure and mechanical stresses in a medium containing discrete joints, and the inelastic response of the individual joints of the rock mass subject to the combined fluid pressure and mechanical loading. 2 - Restrictions on the complexity of the problem: STAFAN does not presently contain thermal coupling, and it is unable to simulate inelastic deformation of the rock mass and variably saturated or two-phase flow in the fractured porous medium system

  7. Application of fracture mechanics to fatigue in pressure vessels

    International Nuclear Information System (INIS)

    Ghavami, K.

    1982-01-01

    The methods of application of fracture mechanics to predict fatigue crack propagation in welded structures and pressure vessels are described with the following objectives: i) To identify the effect of different variables such as crack tip plasticity, free surface, finite plate thickness, stress concentration and type of the structure, on the magnitude of stress intensity factor K in Welded joint. ii) To demonstrate the use of fracture mechanics for analysing fatigue crack propagation data. iii) To show how a law of fatigue crack propagation based on fracure mechanics, may be used to predict fatigue behavior of welded structures such as pressure vessel. (Author) [pt

  8. Thermo-hydro-mechanical behavior of fractured rock mass

    International Nuclear Information System (INIS)

    Coste, F.

    1997-12-01

    The purpose of this research is to model Thermo-Hydro-Mechanical behavior of fractured rock mass regarding a nuclear waste re-depository. For this, a methodology of modeling was proposed and was applied to a real underground site (EDF site at Nouvelle Romanche). This methodology consists, in a first step, to determine hydraulic and mechanical REV. Beyond the greatest of these REV, development of a finite element code allows to model all the fractures in an explicit manner. The homogenized mechanical properties are determined in drained and undrained boundary conditions by simulating triaxial tests that represent rock mass subject to loading. These simulations allow to study the evolution of hydraulic and mechanical properties as a function of stress state. Drained and undrained boundary conditions enable to discuss the validity of assimilation of a fractured rock mass to a porous medium. The simulations lead to a better understanding of the behavior of the fractured rock masses and allow to show the dominant role of the shear behavior of the fractures on the hydraulic and mechanical homogenized properties. From a thermal point of view, as long as conduction is dominant, thermal properties of the rock mass are almost the same as those the intact rock. (author)

  9. Reliability Analysis of Fatigue Fracture of Wind Turbine Drivetrain Components

    DEFF Research Database (Denmark)

    Berzonskis, Arvydas; Sørensen, John Dalsgaard

    2016-01-01

    in the volume of the casted ductile iron main shaft, on the reliability of the component. The probabilistic reliability analysis conducted is based on fracture mechanics models. Additionally, the utilization of the probabilistic reliability for operation and maintenance planning and quality control is discussed....

  10. Wear resistance and fracture mechanics of WC-Co composites

    International Nuclear Information System (INIS)

    Kaytbay, Saleh; El-Hadek, Medhat

    2014-01-01

    Manufacturing of WC-Co composites using the electroless precipitation method at different sintering temperatures of 1 100, 1 250, 1 350 and 1 500 C was successfully achieved. The chemical composition of the investigated materials was 90 wt.% WC with 10 wt.% Co, and 80 wt.% WC with 20 wt.% Co. The specific density, densification, and Vickers microhardness measurements were found to increase with increased sintering temperature for both the WC-Co compositions. The composites of tungsten carbide with 10 wt.% Co had a higher specific density and Vickers microhardness measurements than those for the composites of tungsten carbide with 20 wt.% Co. Composites with WC-10 wt.% Co had better wear resistance. The stress-strain and transverse rupture strength increased monotonically with the increase in sintering temperatures, agreeing with the material hardness and wear resistance behavior. Fractographical scanning electron microscopy analysis of the fracture surface demonstrated a rough characteristic conical shape failure in the direction of the maximum shear stress. A proposed mechanism for the formation of the conical fracture surface under compression testing is presented. (orig.)

  11. Nonlinear Fracture Mechanics and Plasticity of the Split Cylinder Test

    DEFF Research Database (Denmark)

    Olesen, John Forbes; Østergaard, Lennart; Stang, Henrik

    2006-01-01

    properties. This implies that the linear elastic interpretation of the ultimate splitting force in term of the uniaxial tensile strength of the material is only valid for special situations, e.g. for very large cylinders. Furthermore, the numerical analysis suggests that the split cylinder test is not well...... models are presented, a simple semi-analytical model based on analytical solutions for the crack propagation in a rectangular prismatic body, and a finite element model including plasticity in bulk material as well as crack propagation in interface elements. A numerical study applying these models...... demonstrates the influence of varying geometry or constitutive properties. For a split cylinder test in load control it is shown how the ultimate load is either plasticity dominated or fracture mechanics dominated. The transition between the two modes is related to changes in geometry or constitutive...

  12. The hydro-mechanical modeling of the fractured media; Modelisation hydromecanique des milieux fractures

    Energy Technology Data Exchange (ETDEWEB)

    Kadiri, I

    2002-10-15

    The hydro-mechanical modeling of the fractured media is quite complex. Simplifications are necessary for the modeling of such media, but, not always justified, Only permeable fractures are often considered. The rest of the network is approximated by an equivalent continuous medium. Even if we suppose that this approach is validated, the hydraulic and mechanical properties of the fractures and of the continuous medium are seldom known. Calibrations are necessary for the determination of these properties. Until now, one does not know very well the nature of measurements which must be carried out in order to carry on a modeling in discontinuous medium, nor elements of enough robust validation for this kind of modeling. For a better understanding of the hydro-mechanical phenomena in fractured media, two different sites have been selected for the work. The first is the site of Grimsel in Switzerland in which an underground laboratory is located at approximately 400 m of depth. The FEBEX experiment aims at the in-situ study of the consecutive phenomena due to the installation of a heat source representative of radioactive waste in the last 17 meters of the FEBEX tunnel in the laboratory of Grimsel. Only, the modeling of the hydro-mechanical of the excavation was model. The modeling of the Febex enabled us to establish a methodology of calibration of the hydraulic properties in the discontinuous media. However, this kind of study on such complex sites does not make possible to answer all the questions which arise on the hydro-mechanical behavior of the fractured media. We thus carried out modeling on an other site, smaller than the fist one and more accessible. The experimental site of Coaraze, in the Maritime Alps, is mainly constituted of limestone and fractures. Then the variation of water pressure along fractures is governed by the opening/closure sequence of a water gate. Normal displacement as well as the pore pressure along these fractures are recorded, and then

  13. Influence of ageing on glass and resin bonding of dental glass-ceramic veneer adhesion to zirconia: A fracture mechanics analysis and interpretation.

    Science.gov (United States)

    Swain, M V; Gee, C; Li, K C

    2018-04-26

    Adhesion plays a major role in the bonding of dental materials. In this study the adhesion of two glass-ceramic systems (IPS e.max and VITABLOCS) to a zirconia sintered substrate using a glass (for IPS e.max) and resin (VITABLOCS) before and after exposure to ageing for 14 days in distilled water at 37 °C are compared using two interfacial fracture mechanics tests, the 3 point bend Schwickerath (Kosyfaki and Swain, 2014; Schneider and Swain, 2015) and 4 point bend (Charalambides et al., 1989) approaches. Both tests result in stable crack extension from which the strain energy release rate (G, N/m or J/m 2 ) can be determined. In the case of the 3 PB test the Work of Fracture was also determined. In addition, the Schwickerath test enables determination of the critical stress for the onset of cracking to occur, which forms the basis of the ISO (ISO9693-2:2016) adhesion test for porcelain ceramic adhesion to zirconia. For the aged samples there was a significant reduction in the resin-bonded strengths (Schwickerath) and strain energy release rate (both 3 and 4 PB tests), which was not evident for the glass bonded specimens. Critical examination of the force-displacement curves showed that ageing of the resin resulted in a major change in the form of the curves, which may be interpreted in terms of a reduction in the critical stress to initiate cracking and also in the development of an R-curve. The extent of the reduction in strain energy release rate following ageing was greater for the Schwickerath test than the Charalambides test. The results are discussed in terms of; the basic mechanics of these two tests, the deterioration of the resin bonding following moisture exposure and the different dimensions of the specimens. These in-vitro results raise concerns regarding resin bonding to zirconia. The present study uses a novel approach to investigate the role of ageing or environmental degradation on the adhesive bonding of two dental ceramics to zirconia

  14. The hydro-mechanical modeling of the fractured media

    International Nuclear Information System (INIS)

    Kadiri, I.

    2002-10-01

    The hydro-mechanical modeling of the fractured media is quite complex. Simplifications are necessary for the modeling of such media, but, not always justified, Only permeable fractures are often considered. The rest of the network is approximated by an equivalent continuous medium. Even if we suppose that this approach is validated, the hydraulic and mechanical properties of the fractures and of the continuous medium are seldom known. Calibrations are necessary for the determination of these properties. Until now, one does not know very well the nature of measurements which must be carried out in order to carry on a modeling in discontinuous medium, nor elements of enough robust validation for this kind of modeling. For a better understanding of the hydro-mechanical phenomena in fractured media, two different sites have been selected for the work. The first is the site of Grimsel in Switzerland in which an underground laboratory is located at approximately 400 m of depth. The FEBEX experiment aims at the in-situ study of the consecutive phenomena due to the installation of a heat source representative of radioactive waste in the last 17 meters of the FEBEX tunnel in the laboratory of Grimsel. Only, the modeling of the hydro-mechanical of the excavation was model. The modeling of the Febex enabled us to establish a methodology of calibration of the hydraulic properties in the discontinuous media. However, this kind of study on such complex sites does not make possible to answer all the questions which arise on the hydro-mechanical behavior of the fractured media. We thus carried out modeling on an other site, smaller than the fist one and more accessible. The experimental site of Coaraze, in the Maritime Alps, is mainly constituted of limestone and fractures. Then the variation of water pressure along fractures is governed by the opening/closure sequence of a water gate. Normal displacement as well as the pore pressure along these fractures are recorded, and then

  15. Early Age Fracture Mechanics and Cracking of Concrete

    DEFF Research Database (Denmark)

    Østergaard, Lennart

    2003-01-01

    . The reasons are the increased autogenous deformation, the high rate of heat evolution and a higher brittleness of these concretes. Due to these adverse mechanisms the interest in the full description of the behavior of early age concrete has increased dramatically in the last two or three decades. Almost all...... the fictitious crack model and the aim has been experimentally to determine the fracture mechanical properties related to this model. The results provide interesting and important insight into the development of the fracture properties in early age. It is found that the characteristic length has moments of low...... values in early age, which means that the cracking sensibility is higher at those time points. The possible influence of time-dependent effects in the fracture mechanical properties on the cracking behavior in early age has also been investigated. The reason for this has been the known fact...

  16. The application of fracture mechanics on nodular cast iron

    International Nuclear Information System (INIS)

    Kussmaul, K.; Blind, D.; Kockelmann, H.; Roos, E.; Eisele, U.

    1987-01-01

    A series of studies on predominantly thick-walled castings was the first attempt at a characterization of the material of ferritization-annealed ductile cast iron under aspects of fracture mechanics according to today's state of fracture-mechanics research and testing. As in static and dynamic tensile testing, ferritic cast iron meeting specifications was found to be tough down -40 0 C and below in fracture mechanical testing without substantial reduction of the corresponding characteristics at room temperature; this is true for a temperature range where the lowest point of impact notch work has been reached already. Impact-type stresses with and without notching resulted in enhanced deformation resistance and deformability in the longitudinal samples taken from tubes. (orig./DG) [de

  17. Interdisciplinary seminar on nondestructive testing and fracture mechanics. Lectures

    International Nuclear Information System (INIS)

    1998-01-01

    The proceedings volume contains 17 lectures presented at a DGZfP seminar held in Berlin/Germany, 2-3 November 1998. Fracture mechanics data are of interest with respect to determining maximum permissible limits for non-destructive materials evaluation, and as quantitative NDE test results indicating existing materials flaws in a system component, delivering information for assessement of remaining service life and safety risks. The topics of lectures are: Quality concepts for welded joints; NDE for service life assessment of engine components, shown for evaluation of engine pales and disks; NDE and crack detection at pressurized gas cylinders; fracture mechanics requirements for NDE in nuclear installations, discussion of practical examples (T. Seidenkranz); failure of off-shore constructions seen in the light of a novel fracture mechanics technical code. (orig./CB) [de

  18. Computational aspects of nonlinear fracture mechanics

    International Nuclear Information System (INIS)

    Brocks, W.; Cornec, A.; Scheider, I.

    2003-01-01

    The following contribution will essentially restrict to the application of the von Mises theory of incremental plasticity to cracked specimens and components. In particular, the classical parameters of EPFM, J and CTOD, as well as subsequently proposed parameters such as energy dissipation rate and crack-tip opening angle (CTOA) and the related computational aspects will be discussed. Some remarks follow on the 'local approach to fracture' which is based on continuum field quantities, namely stresses and strains, and the damage models of Gurson (1977) and Rousselier (1987), which have now found increasing application, will be briefly addressed in Section 3.03.4. The numerical modeling of decohesion and separation phenomena by 'cohesive elements' will be presented in Section 3.03.5. (orig.)

  19. Applications of probabilistic fracture mechanics to FBR components

    International Nuclear Information System (INIS)

    Yagawa, Genki; Yoshimura, Shinobu; Takenaka, Makoto; Hojo, Kiminobu; Kaguchi, Hitoshi.

    1991-01-01

    A probabilistic fracture mechanics code PCCF which could analyze half-elliptical crack behavior in a plate under creep-fatigue condition using nonlinear fracture mechanics parameters was developed. The effects of bending stress level on failure probability was studied using the PCCF as test analyses. As the results, failure mode was leakage not break in all cases analyzed in this study. It is shown that leak probability is sensitive to stress level and increase rapidly around yield stress of materials. (J.P.N.)

  20. Assessment of copper resistance to stress-corrosion cracking in nitrite solutions by means of joint analysis of acoustic emission measurements, deformation diagrams, qualitative and quantitative fractography, and non-linear fracture mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Khanzhin, V.G.; Nikulin, S.A. [Moscow State Inst. of Steel and Alloys (Russian Federation)

    2005-06-01

    A study of stress-corrosion cracking (SCC) of copper in 0.1M NaNO{sub 2} aqueous solution is presented. The fracture kinetics was monitored by measuring the acoustic emission (AE) signals. Macro- and micro-fractography analysis, using scanning electron microscopy (SEM), was employed to investigate the fracture mechanisms. Estimates of stress intensity factor, KI, and J-integral were derived in order to assess the resistance of copper to stress corrosion cracking. Two kinds of SCC tests under continuous circulation of the corrosive solution were employed in the present study: 1. Constant extension rate (2x10{sup -6}/s) tests on pre-cracked, middle tension (MT) panel specimens. 2. Tests on pre-cracked, compact tension (CT) specimens at a fixed (by a fixing bolt) opening of the crack walls ({delta} = 0.3 mm, K{sub i} = 27 MPax{radical}m). The time base for these tests was about two months. After the completion of the SCC test, the CT specimen was additionally tested, under a constant-rate (0.02 mm/s) off-center extension. In the both kinds of tests, the SCC fracture kinetics is found to exhibit two typical stages: Stage 1: SCC initiation stage (after a certain incubation period, T{sub i}, measured to be T{sub i} {approx_equal} 3-4 hours for MT specimens under constant extension, the corresponding stress was {sigma} {approx_equal} 40-70 MPa, and T{sub i} {approx_equal} 200 hours for CT specimens under a fixed crack wall opening). Stage 2: Active fracture process (SCC macro-fracture) distinguished by strong AE pulses (which are registered after time T{sub 2} {approx_equal} 8 hours for MT specimens and T{sub 2} {approx_equal} 800 hours for CT specimens). Fractography analysis has shown that the zone of SCC fracture in MT specimens extends to approximately 1,500 {mu}m. A 400-700 {mu}m deep zone of brittle transgranular fracture, which included small areas showing characteristic SCC 'striations', was observed adjacent to the fatigue pre-crack area. At higher

  1. Fracture mechanism of coronal teenage dentin

    Science.gov (United States)

    Panfilov, P. E.; Kabanova, A. V.; Borodin, I. N.; Guo, J.; Zang, Z.

    2017-10-01

    The structure of coronal teenage dentin and the development of cracks in it are studied on microand nanolevels. The material is found to fail according to a ductile mechanism on a microlelvel and according to a ductile-brittle mechanism on a nanoscale. This behavior is similar to the failure of a polyethylene film and rubber, when significant elastic and irreversible deformation precedes crack growth. The viscoelastic behavior can be considered as the reaction of dentin to an applied mechanical load.

  2. Fracture mechanics based life assessment in petrochemical plants

    International Nuclear Information System (INIS)

    Norasiah Ab Kasim; Abd Nassir Ibrahim; Ab Razak Hamzah; Shukri Mohd

    2004-01-01

    The increasing use of thick walled pressure vessels in petrochemical plants operating at high pressure under severe service conditions could lead to catastrophic failure. In the Malaysian Institute for Nuclear Technology Research (MINT), initial efforts are underway to apply fracture mechanics approach for assessment of significance of defects detected during periodic in service inspection (ISI) of industrial plants. This paper outlines the integrity management strategy based on fracture mechanics and proposes a new procedure for life assessment of petrochemical plants based on ASME Boiler and Pressure Vessel Code, Section XI, BSI PD 6493:1991, BSI 6539:1994, BSI Standard 7910:1999 and API 579:2000. Essential relevant data required for the assessment is listed. Several methods available for determination of fracture toughness are reviewed with limitations in their application to petrochemical plants. A new non destructive method for determination of fracture toughness based on hardness testing and normalized key roughness curve is given. Results of fracture mechanics based life assessment conducted for 100 mm thick ammonia converter of Ni r o steel and 70 mm thick plat forming reactor vessel of ASTM A 38 7 grade B steel in operational fertilizer and petroleum refining plants are presented. (Author)

  3. Rheology and Fracture Mechanics of Foods

    NARCIS (Netherlands)

    Vliet, van T.

    2013-01-01

    The mechanical properties of food play an important role during manufacturing, storage, handling, and last but not least, during consumption. For an adequate understanding of the mechanical properties of liquid, liquid-like, soft solid, and solid foods, a basic understanding of relevant aspects of

  4. Fracture mechanics evaluation for at typical PWR primary coolant pipe

    International Nuclear Information System (INIS)

    Tanaka, T.; Shimizu, S.; Ogata, Y.

    1997-01-01

    For the primary coolant piping of PWRs in Japan, cast duplex stainless steel which is excellent in terms of strength, corrosion resistance, and weldability has conventionally been used. The cast duplex stainless steel contains the ferrite phase in the austenite matrix and thermal aging after long term service is known to change its material characteristics. It is considered appropriate to apply the methodology of elastic plastic fracture mechanics for an evaluation of the integrity of the primary coolant piping after thermal aging. Therefore we evaluated the integrity of the primary coolant piping for an initial PWR plant in Japan by means of elastic plastic fracture mechanics. The evaluation results show that the crack will not grow into an unstable fracture and the integrity of the piping will be secured, even when such through wall crack length is assumed to equal the fatigue crack growth length for a service period of up to 60 years

  5. Fracture mechanics evaluation for at typical PWR primary coolant pipe

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, T. [Kansai Electric Power Company, Osaka (Japan); Shimizu, S.; Ogata, Y. [Mitsubishi Heavy Industries, Ltd., Kobe (Japan)

    1997-04-01

    For the primary coolant piping of PWRs in Japan, cast duplex stainless steel which is excellent in terms of strength, corrosion resistance, and weldability has conventionally been used. The cast duplex stainless steel contains the ferrite phase in the austenite matrix and thermal aging after long term service is known to change its material characteristics. It is considered appropriate to apply the methodology of elastic plastic fracture mechanics for an evaluation of the integrity of the primary coolant piping after thermal aging. Therefore we evaluated the integrity of the primary coolant piping for an initial PWR plant in Japan by means of elastic plastic fracture mechanics. The evaluation results show that the crack will not grow into an unstable fracture and the integrity of the piping will be secured, even when such through wall crack length is assumed to equal the fatigue crack growth length for a service period of up to 60 years.

  6. A calculational round robin in elastic-plastic fracture mechanics

    International Nuclear Information System (INIS)

    Larsson, L.H.

    1983-01-01

    Eighteen organisations participated in this elastic-plastic fracture mechanics (EPFM) numerical analysis round robin which treated the same three-point bend problem as a similar round robin conducted by ASTM four years earlier. The work involved the calculation of overall deformation, J, CTOD and crack profile using plane strain elastic-plastic finite element analysis for a monotonically increasing load up to a maximum deformation which was far beyond the elastic regime. It was found that all of the elastic solutions were accurate to within a few per cent. In the elastic-plastic regime, however, there was a large scatter of the results, increasing with increasing plastic deformation and roughly of the same order as in the ASTM round robin which contained ten solutions. No significant progress has taken place in the state of the art of numerical EPFM analysis over the four-year interval. The reasons for this scatter and tentative conclusions on the most suitable numerical analysis methods in EPFM are discussed. (author)

  7. The fluid mechanics of channel fracturing flows: experiment

    Science.gov (United States)

    Rashedi, Ahmadreza; Tucker, Zachery; Ovarlez, Guillaume; Hormozi, Sarah

    2017-11-01

    We show our preliminary experimental results on the role of fluid mechanics in channel fracturing flows, particularly yield stress fracturing fluids. Recent trends in the oil industry have included the use of cyclic pumping of a proppant slurry interspersed with a yield stress fracturing fluid, which is found to increase wells productivity, if particles disperse in a certain fashion. Our experimental study aims to investigate the physical mechanisms responsible for dispersing the particles (proppant) within a yield stress carrier fluid, and to measure the dispersion of proppant slugs in various fracturing regimes. To this end we have designed and built a unique experimental setup that resembles a fracture configuration coupled with a particle image/tracking velocimetry setup operating at micro to macro dimensions. Moreover, we have designed optically engineered suspensions of complex fluids with tunable yield stress and consistency, well controlled density match-mismatch properties and refractive indices for both X-rays and visible lights. We present our experimental system and preliminary results. NSF (Grant No. CBET-1554044- CAREER), ACS PRF (Grant No. 55661-DNI9).

  8. Draft fracture mechanics code case for American Society of Mechanical Engineers NUPACK rules

    International Nuclear Information System (INIS)

    McConnell, P.; Sorenson, K.; Nickell, R.; Saegusa, T.

    2004-01-01

    The containment boundaries of most spent-fuel casks certified for use in the United States by the Nuclear Regulatory Commission are constructed with stainless steel, a material that is ductile in an engineering sense at all temperatures and for which, therefore, fracture mechanics principles are not relevant for the containment application. Ferritic materials may fail in a nonductile manner at sufficiently low temperatures, so fracture mechanics principles may be applied to preclude nonductile fracture. Because of the need to transport and store spent nuclear fuel safely in all types of climatic conditions, these vessels have regulatory lowest service temperatures that range down to -40 C (-40 F) for transport application. Such low service temperatures represent a severe challenge in terms of fracture toughness to many ferritic materials. Linear-elastic and elastic-plastic fracture mechanics principles provide a methodology for evaluating ferritic materials under such conditions

  9. Approximative determination of failure probabilities in probabilistic fracture mechanics

    International Nuclear Information System (INIS)

    Riesch-Oppermann, H.; Brueckner, A.

    1987-01-01

    The possibility of using FORM in probabilistic fracture mechanics (PFM) is investigated. After a short review of the method and a description of some specific problems occurring in PFM applications, results obtained with FORM for the failure probabilities in a typical PFM problem (fatigue crack growth) are compared with those determined by a Monte Carlo simulation. (orig./HP)

  10. Fracture mechanics applied to the machining of brittle materials

    Energy Technology Data Exchange (ETDEWEB)

    Hiatt, G.D.; Strenkowski, J.S.

    1988-12-01

    Research has begun on incorporating fracture mechanics into a model of the orthogonal cutting of brittle materials. Residual stresses are calculated for the machined material by a combination of Eulerian and Lagrangian finite element models and then used in the calculation of stress intensity factors by the Green`s Function Method.

  11. Use of fracture mechanics in the US industry

    Energy Technology Data Exchange (ETDEWEB)

    Landes, J.D. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Materialforschung

    2001-07-01

    The modern fracture mechanics technology began in the US in the 1960's. It was developed in response to failure problems that could not be explained by current technology. Some segments of the US industry were quick to embrace this new technology. The period of 1960 to middle 1980's marked a time of active fracture mechanics research in the US industry. From this various codes and assessment procedures have been developed to apply the fracture mechanics approach to evaluate the safety and reliability of critical structural components. This report discusses the US industry use of fracture mechanics. It considers the historical developments, some of the fracture mechanics tools that are available and present practices. Several different industry segments that have used the fracture mechanics approach are considered. These include aerospace, military, power generation, petrochemical and pipelines, metal producers, and construction/transportation. Their current use of the fracture mechanics methods involves the implementation of codes and procedures, the development of software packages, the use of outside consulting groups and some in-house research efforts. (orig.) [German] Die Entwicklung der modernen Bruchmechanik in den USA begann in den 1960er Jahren im Zusammenhang mit einer Reihe von Versagensfaellen, die auf konventionelle Weise nicht erklaert werden konnten. Die neuen Ansaetze wurden von einigen Branchen schnell aufgegriffen und weiterentwickelt. Die Periode von 1960 bis in die Mitte der 1980er Jahre markiert eine Zeit intensiver Forschungsarbeit in der amerikanischen Industrie. Eine Reihe von Codes und Vorschriften zur Bewertung der Sicherheit und Zuverlaessigkeit gefaehrdeter Strukturen hat ihren Ursprung in dieser Zeit. Der vorliegende Aufsatz thematisiert die Anwendung bruchmechanischer Methoden in der Industrie der USA anhand historischer Aspekte, des heute verfuegbaren Instrumentariums der Bauteilbewertung und der gaengigen Praxis bei der

  12. Correlation between high resolution sequence stratigraphy and mechanical stratigraphy for enhanced fracture characteristic prediction

    Science.gov (United States)

    Al Kharusi, Laiyyan M.

    Sequence stratigraphy relates changes in vertical and lateral facies distribution to relative changes in sea level. These relative changes in carbonates effect early diagenesis, types of pores, cementation and dissolution patterns. As a result, in carbonates, relative changes in sea level significantly impact the lithology, porosity, diagenesis, bed and bounding surfaces which are all factors that control fracture patterns. This study explores these relationships by integrating stratigraphy with fracture analysis and petrophysical properties. A special focus is given to the relationship between mechanical boundaries and sequence stratigraphic boundaries in three different settings: (1) Mississippian strata in Sheep Mountain Anticline, Wyoming, (2) Mississippian limestones in St. Louis, Missouri, and (3) Pennsylvanian limestones intermixed with elastics in the Paradox Basin, Utah. The analysis of these sections demonstrate that a fracture hierarchy exists in relation to the sequence stratigraphic hierarchy. The majority of fractures (80%) terminate at genetic unit boundaries or the internal flooding surface that separates the transgressive from regressive hemicycle. Fractures (20%) that do not terminate at genetic unit boundaries or their internal flooding surface terminate at lower order sequence stratigraphic boundaries or their internal flooding surfaces. Secondly, the fracture spacing relates well to bed thickness in mechanical units no greater than 0.5m in thickness but with increasing bed thickness a scatter from the linear trend is observed. In the Paradox Basin the influence of strain on fracture density is illustrated by two sections measured in different strain regimes. The folded strata at Raplee Anticline has higher fracture densities than the flat-lying beds at the Honaker Trail. Cemented low porosity rocks in the Paradox Basin do not show a correlation between fracture pattern and porosity. However velocity and rock stiffness moduli's display a slight

  13. Fracture Penis: An Analysis of 26 Cases

    Directory of Open Access Journals (Sweden)

    G.V.Soundra Pandyan

    2006-01-01

    Full Text Available The aim of this study was to review the pattern of penile fracture occurrence, its clinical presentation, diagnosis, management, and outcome at our center. A retrospective analysis of 26 patients with penile fractures treated at our hospital from January 1997 to January 2005 was carried out. We noted an incidence of 3.5 cases per year, occurring more commonly in unmarried men. Of our study group, 28 episodes of penile fractures occurred in 26 patients. Hospital presentation after trauma varied from 2 h to 21 days. Masturbation was the main initiating causative factor and penile hematoma was the most common clinical finding. Nearly 81% noticed the characteristic click prior to the fracture. Clinical diagnosis was adequate in a majority of the cases. Midshaft fractures with right-sided laterality were more frequent in this series. The tear size ranged from 0.5—2.5 cm with a mean of 1.1 cm. All cases, but one, were treated by surgical repair using absorbable sutures. Out of three cases treated conservatively, two failed to respond and had to be treated surgically. False fracture with dorsal vein tear was present in two cases. Involvement of bilateral corpora was seen in one patient. Infection was the most common early complication, while pain with deviation was the late complication. In our experience, clinical findings are adequate enough to diagnose fracture penis in a majority of cases. Surgical exploration with repair of the tear is recommended both in early and delayed presentations. There was no noticeable relationship to the time of initial presentation or with the size and site of tear to the final outcome.

  14. OCA-P, a deterministic and probabilistic fracture-mechanics code for application to pressure vessels

    International Nuclear Information System (INIS)

    Cheverton, R.D.; Ball, D.G.

    1984-05-01

    The OCA-P code is a probabilistic fracture-mechanics code that was prepared specifically for evaluating the integrity of pressurized-water reactor vessels when subjected to overcooling-accident loading conditions. The code has two-dimensional- and some three-dimensional-flaw capability; it is based on linear-elastic fracture mechanics; and it can treat cladding as a discrete region. Both deterministic and probabilistic analyses can be performed. For the former analysis, it is possible to conduct a search for critical values of the fluence and the nil-ductility reference temperature corresponding to incipient initiation of the initial flaw. The probabilistic portion of OCA-P is based on Monte Carlo techniques, and simulated parameters include fluence, flaw depth, fracture toughness, nil-ductility reference temperature, and concentrations of copper, nickel, and phosphorous. Plotting capabilities include the construction of critical-crack-depth diagrams (deterministic analysis) and various histograms (probabilistic analysis)

  15. Unique Mechanism of Chance Fracture in a Young Adult Male

    Directory of Open Access Journals (Sweden)

    Aaron Birch

    2013-03-01

    Full Text Available Since the first description of the Chance fracture in 1948, there have been few case reports ofunique mechanisms causing this classical flexion-extension injury to the spine in motor vehicleaccidents, sports injury, and falls. To our knowledge, this injury has not been reported from a fall withthe mechanistic forces acting laterally on the spine and with spinal support in place. We present a21-year-old male who slid down a flight of stairs onto his side wearing a heavy mountaineering stylebackpack, subsequently sustaining a Chance fracture of his first lumbar vertebrae.

  16. Finite element analysis of tibial fractures

    DEFF Research Database (Denmark)

    Wong, Christian Nai En; Mikkelsen, Mikkel Peter W; Hansen, Leif Berner

    2010-01-01

    Project. The data consisted of 21,219 3D elements with a cortical shell and a trabecular core. Three types of load of torsion, a direct lateral load and axial compression were applied. RESULTS: The finite element linear static analysis resulted in relevant fracture localizations and indicated relevant...

  17. Fracture behavior and deformation mechanisms under fast neutron irradiation

    International Nuclear Information System (INIS)

    Boutard, J.L.; Dupouy, J.M.

    1980-09-01

    We have established the out-of-pile and in-pile deformation mechanism maps of a 316 stainless steel irradiated in a fast reactor. The knowledge of the dominating deformation mechanism either in post irradiation creep experiments or during the in-pile steady state operating conditions allows to rationalize the apparent discrepancy between the very low out-of-pile ductility and the rather high plastic diametral strains which are obtained in the fast reactor environment without fracture

  18. Application of Fracture-Mechanics Approach to Gas Pipelines

    Czech Academy of Sciences Publication Activity Database

    Gajdoš, Lubomír; Šperl, Martin

    VII, č. 73 (2011), s. 480-487 ISSN 2010-376X R&D Projects: GA ČR(CZ) GAP105/10/2052; GA ČR(CZ) GPP105/10/P555 Grant - others:GAMPO(CZ) FT-TA5/076 Program:FT Institutional research plan: CEZ:AV0Z20710524 Keywords : axial crack * fracture-mechanics * J integral * pipeline wall Subject RIV: JL - Materials Fatigue, Friction Mechanics

  19. The fracture properties and toughening mechanisms of bone and dentin

    Science.gov (United States)

    Koester, Kurt John

    The mechanical properties of bone and dentin and in particular their fracture properties, are the subject of intense research. The relevance of these properties is increasing as our population ages and fracture incidence impacts the lives of a greater portion of the population. A robust framework is needed to understand the fracture properties of bone and dentin to guide researchers as they attempt to characterize the effects of aging, disease, and pharmaceutical treatments on the properties of these mineralized tissues. In the present work, this framework is provided and applied to human bone, human dentin, and animal bone. In situ electron microscopy was also used to identify the salient toughening mechanisms in bone and dentin. It was found that bone and dentin are extrinsically toughened materials and consequently their fracture properties are best characterized utilizing a crack-growth resistance approach. A description of the different mechanical measurements commonly employed when using small animal models (rats and mice) to evaluate the influence of drug therapies on bone fragility is provided. A study where these properties were measured for a large population of wild-type rats and mice was also conducted. Given my findings, it was determined that for the most complete understanding of small animal bone it was necessary to measure strength and toughness. Strength measurements probe the flaw distribution and toughness measurements to evaluate the resistance to facture in the presence of a single dominant worst-case flaw.

  20. Prediction of retained residual stresses in laboratory fracture mechanics specimens extracted from welded components

    International Nuclear Information System (INIS)

    Hurlston, R.G.; Sherry, A.H.; James, P.; Sharples, J.K.

    2015-01-01

    The measurement of weld material fracture toughness properties is important for the structural integrity assessment of engineering components. However, welds can contain high levels of residual stress and these can be retained in fracture mechanics specimens, particularly when machined from non-stress relieved welds. Retained residual stresses can make the measurement of valid fracture toughness properties difficult. This paper describes the results of analytical work undertaken to investigate factors that can influence the magnitude and distribution of residual stresses retained in fracture mechanics specimen blanks extracted from as-welded ferritic and austenitic stainless steel plates. The results indicate that significant levels of residual stress can be retained in specimen blanks prior to notching, and that the magnitude and distribution of stress is dependent upon material properties, specimen geometry and size, and extraction location through the thickness of the weld. Finite element modelling is shown to provide a useful approach for estimating the level and distributions of retained residual stresses. A new stress partitioning approach has been developed to estimate retained stress levels and results compare favourably with FE analysis and available experimental data. The approach can help guide the selection of specimen geometry and machining strategies to minimise the level of residual stresses retained in fracture mechanics specimen blanks extracted from non stress-relieved welds and thus improve the measurement of weld fracture toughness properties. - Highlights: • A simplified method for generating realistic weld residual stresses has been developed. • It has been shown that significant levels of residual stress can be retained within laboratory fracture mechanics specimens. • The level and distribution is dependant upon material, specimen type, specimen size and extraction location. • A method has been developed to allow estimates of the

  1. Characterizing Fractures Across the Astronaut Corps: Preliminary Findings from Population-Level Analysis

    Science.gov (United States)

    Rossi, Meredith M.; Charvat, Jacqueline; Sibonga, Jean; Sieker, Jeremy

    2017-01-01

    -selection fractures experienced those fractures following their first mission (mean 12.7 +/- 11.1 years following first mission; range 14.0 days - 50.6 years). Additional analyses are ongoing and include examination of fracture history, skeletal site, mechanism, and type of fracture, age at time of fracture, time from spaceflight to fracture, as well as multivariable analysis comparing fracture events to non-events. The results of such analyses may reveal trends in risk factors for fracture among the astronaut corps that have yet to be systematically described through a corps-wide approach.

  2. Fracture mechanics analyses of ceramic/veneer interface under mixed-mode loading.

    Science.gov (United States)

    Wang, Gaoqi; Zhang, Song; Bian, Cuirong; Kong, Hui

    2014-11-01

    Few studies have focused on the interface fracture performance of zirconia/veneer bilayered structure, which plays an important role in dental all-ceramic restorations. The purpose of this study was to evaluate the fracture mechanics performance of zirconia/veneer interface in a wide range of mode-mixities (at phase angles ranging from 0° to 90°), and to examine the effect of mechanical properties of the materials and the interface on the fracture initiation and crack path of an interfacial crack. A modified sandwich test configuration with an oblique interfacial crack was proposed and calibrated to choose the appropriate geometry dimensions by means of finite element analysis. The specimens with different interface inclination angles were tested to failure under three-point bending configuration. Interface fracture parameters were obtained with finite element analyses. Based on the interfacial fracture mechanics, three fracture criteria for crack kinking were used to predict crack initiation and propagation. In addition, the effects of residual stresses due to coefficient of thermal expansion mismatch between zirconia and veneer on the crack behavior were evaluated. The crack initiation and propagation were well predicted by the three fracture criteria. For specimens at phase angle of 0, the cracks propagated in the interface; whereas for all the other specimens the cracks kinked into the veneer. Compressive residual stresses in the veneer can improve the toughness of the interface structure. The results suggest that, in zirconia/veneer bilayered structure the veneer is weaker than the interface, which can be used to explain the clinical phenomenon that veneer chipping rate is larger than interface delamination rate. Consequently, a veneer material with larger fracture toughness is needed to decrease the failure rate of all-ceramic restorations. And the coefficient of thermal expansion mismatch of the substrates can be larger to produce larger compressive

  3. Understanding cracking failures of coatings: A fracture mechanics approach

    Science.gov (United States)

    Kim, Sung-Ryong

    A fracture mechanics analysis of coating (paint) cracking was developed. A strain energy release rate (G(sub c)) expression due to the formation of a new crack in a coating was derived for bending and tension loadings in terms of the moduli, thicknesses, Poisson's ratios, load, residual strain, etc. Four-point bending and instrumented impact tests were used to determine the in-situ fracture toughness of coatings as functions of increasing baking (drying) time. The system used was a thin coating layer on a thick substrate layer. The substrates included steel, aluminum, polycarbonate, acrylonitrile-butadiene-styrene (ABS), and Noryl. The coatings included newly developed automotive paints. The four-point bending configuration promoted nice transversed multiple coating cracks on both steel and polymeric substrates. The crosslinked type automotive coatings on steel substrates showed big cracks without microcracks. When theoretical predictions for energy release rate were compared to experimental data for coating/steel substrate samples with multiple cracking, the agreement was good. Crosslinked type coatings on polymeric substrates showed more cracks than theory predicted and the G(sub c)'s were high. Solvent evaporation type coatings on polymeric substrates showed clean multiple cracking and the G(sub c)'s were higher than those obtained by tension analysis of tension experiments with the same substrates. All the polymeric samples showed surface embrittlement after long baking times using four-point bending tests. The most apparent surface embrittlement was observed in the acrylonitrile-butadiene-styrene (ABS) substrate system. The impact properties of coatings as a function of baking time were also investigated. These experiments were performed using an instrumented impact tester. There was a rapid decrease in G(sub c) at short baking times and convergence to a constant value at long baking times. The surface embrittlement conditions and an embrittlement toughness

  4. Applications of Automation Methods for Nonlinear Fracture Test Analysis

    Science.gov (United States)

    Allen, Phillip A.; Wells, Douglas N.

    2013-01-01

    Using automated and standardized computer tools to calculate the pertinent test result values has several advantages such as: 1. allowing high-fidelity solutions to complex nonlinear phenomena that would be impractical to express in written equation form, 2. eliminating errors associated with the interpretation and programing of analysis procedures from the text of test standards, 3. lessening the need for expertise in the areas of solid mechanics, fracture mechanics, numerical methods, and/or finite element modeling, to achieve sound results, 4. and providing one computer tool and/or one set of solutions for all users for a more "standardized" answer. In summary, this approach allows a non-expert with rudimentary training to get the best practical solution based on the latest understanding with minimum difficulty.Other existing ASTM standards that cover complicated phenomena use standard computer programs: 1. ASTM C1340/C1340M-10- Standard Practice for Estimation of Heat Gain or Loss Through Ceilings Under Attics Containing Radiant Barriers by Use of a Computer Program 2. ASTM F 2815 - Standard Practice for Chemical Permeation through Protective Clothing Materials: Testing Data Analysis by Use of a Computer Program 3. ASTM E2807 - Standard Specification for 3D Imaging Data Exchange, Version 1.0 The verification, validation, and round-robin processes required of a computer tool closely parallel the methods that are used to ensure the solution validity for equations included in test standard. The use of automated analysis tools allows the creation and practical implementation of advanced fracture mechanics test standards that capture the physics of a nonlinear fracture mechanics problem without adding undue burden or expense to the user. The presented approach forms a bridge between the equation-based fracture testing standards of today and the next generation of standards solving complex problems through analysis automation.

  5. Multiple Sclerosis Increases Fracture Risk: A Meta-Analysis

    Directory of Open Access Journals (Sweden)

    Guixian Dong

    2015-01-01

    Full Text Available Purpose. The association between multiple sclerosis (MS and fracture risk has been reported, but results of previous studies remain controversial and ambiguous. To assess the association between MS and fracture risk, a meta-analysis was performed. Method. Based on comprehensive searches of the PubMed, Embase, and Web of Science, we identified outcome data from all articles estimating the association between MS and fracture risk. The pooled risk ratios (RRs with 95% confidence intervals (CIs were calculated. Results. A significant association between MS and fracture risk was found. This result remained statistically significant when the adjusted RRs were combined. Subgroup analysis stratified by the site of fracture suggested significant associations between MS and tibia fracture risk, femur fracture risk, hip fracture risk, pelvis fracture risk, vertebrae fracture risk, and humerus fracture risk. In the subgroup analysis by gender, female MS patients had increased fracture risk. When stratified by history of drug use, use of antidepressants, hypnotics/anxiolytics, anticonvulsants, and glucocorticoids increased the risk of fracture risk in MS patients. Conclusions. This meta-analysis demonstrated that MS was significantly associated with fracture risk.

  6. Cyclic Fracture Toughness of Railway Axle and Mechanisms of its Fatigue Fracture

    Directory of Open Access Journals (Sweden)

    Sorochak Andriy

    2015-06-01

    Full Text Available The main regularities in fatigue fracture of the railway axle material - the OSL steel - are found in this paper. Micromechanisms of fatigue crack propagation are described and systematized, and a physical-mechanical interpretation of the relief morphology at different stages of crack propagation is proposed for fatigue cracks in specimens cut out of the surface, internal and central layers of the axle.

  7. Fracture mechanism of a dispersion-hardened molybdenum alloy with strong structural interfaces

    International Nuclear Information System (INIS)

    Vasil'ev, A.D.; Malashenko, I.S.; Moiseev, V.F.; Pechkovskij, Eh.P.; Sul'zhenko, V.K.; Trefilov, V.I.; AN Ukrainskoj SSR, Kiev. Inst. Ehlektrosvarki)

    1978-01-01

    Fracture mechanism in the two-phase Mo-15wt.%Nb-3.5 vol.% TiN alloy known to be of ''brittle matrix-strong interfaces'' type has been investigated depending on tensile test temperature. Several temperature intervals of fracture have been found, each of them having its own peculiarities. A scheme is suggested for fracture mechanism changes in dispersion-hardened alloys with strong interfaces. At low test temperatures brittle cleavage fracture takes place. With temperature increase fracture mechanisms change in the following way: brittle intergranular fracture; fracture of ''microvoid coalescence'' type; fracture typical for reinforced materials with ductile matrix; intergran laru fracture. Particles of strengthening phase have been shown to play different roles depending on the test temperature in the fracture of the alloys studied

  8. Probalistic Finite Elements (PFEM) structural dynamics and fracture mechanics

    Science.gov (United States)

    Liu, Wing-Kam; Belytschko, Ted; Mani, A.; Besterfield, G.

    1989-01-01

    The purpose of this work is to develop computationally efficient methodologies for assessing the effects of randomness in loads, material properties, and other aspects of a problem by a finite element analysis. The resulting group of methods is called probabilistic finite elements (PFEM). The overall objective of this work is to develop methodologies whereby the lifetime of a component can be predicted, accounting for the variability in the material and geometry of the component, the loads, and other aspects of the environment; and the range of response expected in a particular scenario can be presented to the analyst in addition to the response itself. Emphasis has been placed on methods which are not statistical in character; that is, they do not involve Monte Carlo simulations. The reason for this choice of direction is that Monte Carlo simulations of complex nonlinear response require a tremendous amount of computation. The focus of efforts so far has been on nonlinear structural dynamics. However, in the continuation of this project, emphasis will be shifted to probabilistic fracture mechanics so that the effect of randomness in crack geometry and material properties can be studied interactively with the effect of random load and environment.

  9. Integration of nondestructive examination reliability and fracture mechanics

    International Nuclear Information System (INIS)

    Doctor, S.R.; Bates, D.J.; Charlot, L.A.

    1985-01-01

    The primary pressure boundaries (pressure vessels and piping) of nuclear power plants are in-service inspected (ISI) according to the rules of ASME Boiler and Pressure Vessel Code, Section XI. Ultrasonic techniques are normally used for these inspections, which are periodically performed on a sampling of welds. The Integration of Nondestructive Examination (NDE) Reliability and Fracture Mechanics (FM) Program at Pacific Northwest Laboratory was established to determine the reliability of current ISI techniques and to develop recommendations that will ensure a suitably high inspection reliability. The objectives of this NRC program are to: 1) determine the reliability of ultrasonic ISI performed on commercial light-water reactor primary systems; 2) using probabilistic FM analysis, determine the impact of NDE unreliability on system safety and determine the level of inspection reliability required to ensure a suitably low failure probability; 3) evaluate the degree of reliability improvement that could be achieved using improved and advanced NDE techniques; and 4) based on material properties, service conditions, and NDE uncertainties, formulate recommended revisions to ASME Code, Section XI, and Regulatory Requirements needed to ensure suitably low failure probabilities

  10. 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)

  11. Acoustic emission from zirconium alloys during mechanical and fracture testing

    International Nuclear Information System (INIS)

    Coleman, C.E.

    1986-10-01

    The application of acoustic emission during the mechanical and fracture testing of zirconium alloys is reviewed. Acoustic emission is successful in following delayed hydride cracking quantitatively. It is especially useful when great sensitivity is required. Application to fatigue, tensile deformation and stress corrosion cracking appears promising but requires more work to separate phenomena before it can be used quantitatively. This report is based on an invited review for the American Society of Non-Destructive Testing Handbook: Volume 5, Acoustic Emission Testing

  12. Special fracture mechanics specimens for multilayer plastic pipes testing

    Czech Academy of Sciences Publication Activity Database

    Hutař, Pavel; Šestáková, Lucie; Knésl, Zdeněk; Nezbedová, E.; Náhlík, Luboš

    2009-01-01

    Roč. 28, č. 8 (2009), s. 785-792 ISSN 0142-9418 R&D Projects: GA ČR GA106/09/0279; GA ČR GC101/09/J027 Institutional research plan: CEZ:AV0Z20410507 Keywords : Multilayer plastic pipes * C-type specimen * K-calibration * Fracture toughness * Slow crack growth * Non-homogenous specimens Subject RIV: JL - Material s Fatigue, Friction Mechanics Impact factor: 1.667, year: 2009

  13. A unified approach to elastic-plastic fracture mechanics

    International Nuclear Information System (INIS)

    Neale, B.K.; Townley, C.H.A.

    1976-01-01

    To assess the integrity of a cracked structure, using materials data obtained from simple laboratory tests, it is essential to define materials properties which are independent of the shape and the size of the specimen and of the loading system applied to it. In those situations where either the specimen or the structure fails after significant yielding has taken place, there is considerable speculation about the materials parameters which are relevant. By extending the Griffith equation for the stability of a perfectly elastic cracked body, the authors derive a fracture criterion which is applicable in the post yield regime. Comparisons are made with procedures based on the J-contour integral, equivalent energy, and crack opening displacements and with the post yield fracture mechanics of Heald, Spink and Worthington, and Dowling and Townley. For certain materials, it is shown that the factor controlling crack initiation is the fracture toughness Ksub(1c), irrespective of the amount of prior plastic damage, and hence independent of the shape and size of the specimen tested. Load carrying capacity in the post yield regime cannot, however, be derived directly from a knowledge of fracture toughness; the ultimate tensile strength of the material is also relevant

  14. Rock mechanics in the disposal of radioactive wastes by hydraulic fracturing

    Energy Technology Data Exchange (ETDEWEB)

    McClain, W C

    1968-01-01

    The ultimate capacity of a hydraulic-fracturing waste disposal facility is governed primarily by the integrity of the rocks overlying the injected wastes. The objective of this study is to analyze theoretically the stresses and strains generated by the injected wastes in an effort to understand the behavior of the system sufficiently well that the failure mechanism can be predicted and the capacity of the injection well estimated. The surface uplifts at Oak Ridge National Laboratory's fracturing site were compared with theoretical curves obtained by assuming the uplifts to be inversely analogous to the subsidence which occurs over mining excavations. This analysis, based on assumptions of homogeneity, isotropy, and linear elasticity, provided considerable insight into the mechanics of the process. The most probable mechanism of failure of the rock appears to be by the formation of a vertical instead of a horizontal fracture. Fracture orientation is controlled primarily by the orientation of the principal stress field in the rock. Each successive waste injection slightly modifies this stress field toward a condition more favorable to the formation of a vertical fracture. (16 refs.)

  15. Studying physical properties of deformed intact and fractured rocks by micro-scale hydro-mechanical-seismicity model

    Science.gov (United States)

    Raziperchikolaee, Samin

    The pore pressure variation in an underground formation during hydraulic stimulation of low permeability formations or CO2 sequestration into saline aquifers can induce microseismicity due to fracture generation or pre-existing fracture activation. While the analysis of microseismic data mainly focuses on mapping the location of fractures, the seismic waves generated by the microseismic events also contain information for understanding of fracture mechanisms based on microseismic source analysis. We developed a micro-scale geomechanics, fluid-flow and seismic model that can predict transport and seismic source behavior during rock failure. This model features the incorporation of microseismic source analysis in fractured and intact rock transport properties during possible rock damage and failure. The modeling method considers comprehensive grains and cements interaction through a bonded-particle-model. As a result of grain deformation and microcrack development in the rock sample, forces and displacements in the grains involved in the bond breakage are measured to determine seismic moment tensor. In addition, geometric description of the complex pore structure is regenerated to predict fluid flow behavior of fractured samples. Numerical experiments are conducted for different intact and fractured digital rock samples, representing various mechanical behaviors of rocks and fracture surface properties, to consider their roles on seismic and transport properties of rocks during deformation. Studying rock deformation in detail provides an opportunity to understand the relationship between source mechanism of microseismic events and transport properties of damaged rocks to have a better characterizing of fluid flow behavior in subsurface formations.

  16. 35. Conference of the DVM Working Group on Fracture Processes: Advances in fracture and damage mechanics - simulation methods of fracture mechanics

    International Nuclear Information System (INIS)

    2003-01-01

    Subjects of the meeting were: Simulation of fatigue crack growth in real strucures using FEA (M. Fulland, Paderborn); Modelling of ductile crack growth (W. Brocks, Geesthacht); Advances in non-local modelling of ductile damage (F. Reusch et al., Berlin, Dortmund); Fracture mechanics of ceramics (D. Munz, Karlsruhe); From materials testing to vehicle crash testing (J.G. Blauel, Freiburg); Analytical simulation of crack growth in thin-walled structures (U. Zerbst, Geesthacht); The influence of intrinsic stresses on fatigue crack growth (C. Dalle Donne etc., Cologne, Dortmund, Pisa, and M. Sander, Paderborn); Fracture mechanical strength calculation in case of mixed mode loads on cracks (H.A. Richard, Paderborn); Numeric simulation of intrinsic stresses during welding (C. Veneziano, Freiburg); New research fields of the Fraunhofer-Institut fuer Werkstoffmechanik (P. Gumbsch, Head of the Institute, Freiburg); Modern developments and advances in fracture and damage mechanics; Numeric and experimental simulation of crack propagation and damage processes; Exemplary damage cases; Fracture mechanics in product development; Failure characteristics of lightweight constructional materials and joints [de

  17. Probabilistic finite elements for fatigue and fracture analysis

    Science.gov (United States)

    Belytschko, Ted; Liu, Wing Kam

    1993-04-01

    An overview of the probabilistic finite element method (PFEM) developed by the authors and their colleagues in recent years is presented. The primary focus is placed on the development of PFEM for both structural mechanics problems and fracture mechanics problems. The perturbation techniques are used as major tools for the analytical derivation. The following topics are covered: (1) representation and discretization of random fields; (2) development of PFEM for the general linear transient problem and nonlinear elasticity using Hu-Washizu variational principle; (3) computational aspects; (4) discussions of the application of PFEM to the reliability analysis of both brittle fracture and fatigue; and (5) a stochastic computational tool based on stochastic boundary element (SBEM). Results are obtained for the reliability index and corresponding probability of failure for: (1) fatigue crack growth; (2) defect geometry; (3) fatigue parameters; and (4) applied loads. These results show that initial defect is a critical parameter.

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

    International Nuclear Information System (INIS)

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

    1997-01-01

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

  19. Mechanical properties of highly defective graphene: from brittle rupture to ductile fracture

    International Nuclear Information System (INIS)

    Xu, Lanqing; Wei, Ning; Zheng, Yongping

    2013-01-01

    Defects are generally believed to deteriorate the superlative performance of graphene-based devices but may also be useful when carefully engineered to tailor the local properties and achieve new functionalities. Central to most defect-associated applications is the defect coverage and arrangement. In this work, we investigate, by molecular dynamics simulations, the mechanical properties and fracture dynamics of graphene sheets with randomly distributed vacancies or Stone–Wales defects under tensile deformations over a wide defect coverage range. With defects presented, an sp–sp 2 bonding network and an sp–sp 2 –sp 3 bonding network are observed in vacancy-defected and Stone–Wales-defected graphene, respectively. The ultimate strength degrades gradually with increasing defect coverage and saturates in the high-ratio regime, whereas the fracture strain presents an unusual descending–saturating–improving trend. In the dense vacancy defect situation, the fracture becomes more plastic and super-ductility is observed. Further fracture dynamics analysis reveals that the crack trapping by sp–sp 2 and sp–sp 2 –sp 3 rings and the crack-tip blunting account for the ductile fracture, whereas geometric rearrangement on the entire sheet for vacancy defects and geometric rearrangement on the specific defect sites for Stone–Wales defects account for their distinctive rules of the evolution of the fracture strain. (paper)

  20. Mechanical properties of highly defective graphene: from brittle rupture to ductile fracture.

    Science.gov (United States)

    Xu, Lanqing; Wei, Ning; Zheng, Yongping

    2013-12-20

    Defects are generally believed to deteriorate the superlative performance of graphene-based devices but may also be useful when carefully engineered to tailor the local properties and achieve new functionalities. Central to most defect-associated applications is the defect coverage and arrangement. In this work, we investigate, by molecular dynamics simulations, the mechanical properties and fracture dynamics of graphene sheets with randomly distributed vacancies or Stone-Wales defects under tensile deformations over a wide defect coverage range. With defects presented, an sp-sp(2) bonding network and an sp-sp(2)-sp(3) bonding network are observed in vacancy-defected and Stone-Wales-defected graphene, respectively. The ultimate strength degrades gradually with increasing defect coverage and saturates in the high-ratio regime, whereas the fracture strain presents an unusual descending-saturating-improving trend. In the dense vacancy defect situation, the fracture becomes more plastic and super-ductility is observed. Further fracture dynamics analysis reveals that the crack trapping by sp-sp(2) and sp-sp(2)-sp(3) rings and the crack-tip blunting account for the ductile fracture, whereas geometric rearrangement on the entire sheet for vacancy defects and geometric rearrangement on the specific defect sites for Stone-Wales defects account for their distinctive rules of the evolution of the fracture strain.

  1. Measurement of residual stresses using fracture mechanics weight functions

    International Nuclear Information System (INIS)

    Fan, Y.

    2000-01-01

    A residual stress measurement method has been developed to quantify through-the-thickness residual stresses. Accurate measurement of residual stresses is crucial for many engineering structures. Fabrication processes such as welding and machining generate residual stresses that are difficult to predict. Residual stresses affect the integrity of structures through promoting failures due to brittle fracture, fatigue, stress corrosion cracking, and wear. In this work, the weight function theory of fracture mechanics is used to measure residual stresses. The weight function theory is an important development in computational fracture mechanics. Stress intensity factors for arbitrary stress distribution on the crack faces can be accurately and efficiently computed for predicting crack growth. This paper demonstrates that the weight functions are equally useful in measuring residual stresses. In this method, an artificial crack is created by a thin cut in a structure containing residual stresses. The cut relieves the residual stresses normal to the crack-face and allows the relieved residual stresses to deform the structure. Strain gages placed adjacent to the cut measure the relieved strains corresponding to incrementally increasing depths of the cut. The weight functions of the cracked body relate the measured strains to the residual stresses normal to the cut within the structure. The procedure details, such as numerical integration of the singular functions in applying the weight function method, will be discussed

  2. Measurement of residual stresses using fracture mechanics weight functions

    International Nuclear Information System (INIS)

    Fan, Y.

    2001-01-01

    A residual stress measurement method has been developed to quantify through-the-thickness residual stresses. Accurate measurement of residual stresses is crucial for many engineering structures. Fabrication processes such as welding and machining generate residual stresses that are difficult to predict. Residual stresses affect the integrity of structures through promoting failures due to brittle fracture, fatigue, stress corrosion cracking, and wear. In this work, the weight function theory of fracture mechanics is used to measure residual stresses. The weight function theory is an important development in computational fracture mechanics. Stress intensity factors for arbitrary stress distribution on the crack faces can be accurately and efficiently computed for predicting crack growth. This paper demonstrates that the weight functions are equally useful in measuring residual stresses. In this method, an artificial crack is created by a thin cut in a structure containing residual stresses. The cut relieves the residual stresses normal to the crack-face and allows the relieved residual stresses to deform the structure. Strain gages placed adjacent to the cut measure the relieved strains corresponding to incrementally increasing depths of the cut. The weight functions of the cracked body relate the measured strains to the residual stresses normal to the cut within the structure. The procedure details, such as numerical integration of the singular functions in applying the weight function method, will be discussed. (author)

  3. Probabilistic fracture mechanics applied for lbb case study: international benchmark

    International Nuclear Information System (INIS)

    Radu, V.

    2015-01-01

    An application of probabilistic fracture mechanics to evaluate the structural integrity for a case study chosen from experimental Mock-ups of FP7 STYLE project is described. The reliability model for probabilistic structural integrity, focused on the assessment of TWC in the pipe weld under complex loading (bending moment and residual stress) has been setup. The basic model is the model of fracture for through-wall cracked pipe under elastic-plastic conditions. The corresponding structural reliability approach is developed with the probabilities of failure associated with maximum load for crack initiation, net-section collapse but also the evaluation the instability loads. The probabilities of failure for a through-wall crack in a pipe subject to pure bending are evaluated by using crude Monte Carlo simulations. The results from the international benchmark are presented for the mentioned case in the context of ageing and lifetime management of pressure boundary/pressure circuit component. (authors)

  4. Effects of local mechanical and fracture properties on LBB behavior of a dissimilar metal welded joint in nuclear power plants

    Energy Technology Data Exchange (ETDEWEB)

    Du, L.Y.; Wang, G.Z., E-mail: gzwang@ecust.edu.cn; Xuan, F.Z.; Tu, S.T.

    2013-12-15

    Highlights: • Effect of local mechanical and fracture properties on LBB behavior were investigated. • Considering local mechanical properties leads to slightly high LBB curve. • Use of fracture resistance of base or weld will produce non-conservative LBB result. • Local fracture properties of interface region cannot be ignored in LBB analysis. - Abstract: In this paper, three-dimensional finite element models with and without considering local mechanical properties were built for a dissimilar metal welded joint (DMWJ) connected the safe end to pipe-nozzle of a reactor pressure vessel. The inner circumferential surface cracks were postulated at the interface of A508 steel and buttering Alloy52Mb. Based on the elastic–plastic fracture mechanics theory of J-integral, the crack growth stability was analyzed. The effects of the local mechanical and fracture resistance properties on LBB behavior were investigated. The results show that considering local mechanical properties leads to slightly high LBB curve. For the A508/Alloy52Mb interface region cracks in the DMWJ, if the fracture resistance curve of base metal A508 or the buttering Alloy52Mb is used, the non-conservative (unsafe) LBB assessment result will be produced. With increasing the applied bending moment, the degree of un-conservatism in LBB behavior becomes large. Therefore, to obtain accurate LBB assessment results, the local fracture resistance properties of the interface region should be used.

  5. Future trends in fracture mechanics: theory and applications

    International Nuclear Information System (INIS)

    Hosbons, R.R.

    1978-05-01

    A brief description of the current methods available for the analysis of fracture in ductile materials is given. Crack-opening displacement, R-curves and J-integrals are discussed and their future incorporation into structural codes assessed. The current areas of research which will probably influence code making bodies are also described. Emphasis is made on J-integral theory and a description of its limitations and extensions. Numerical techniques for calculating J for complicated structure are outlined. (author)

  6. Effects of chemical alteration on fracture mechanical properties in hydrothermal systems

    Science.gov (United States)

    Callahan, O. A.; Eichhubl, P.; Olson, J. E.

    2015-12-01

    Fault and fracture networks often control the distribution of fluids and heat in hydrothermal and epithermal systems, and in related geothermal and mineral resources. Additional chemical influences on conduit evolution are well documented, with dissolution and precipitation of mineral species potentially changing the permeability of fault-facture networks. Less well understood are the impacts of chemical alteration on the mechanical properties governing fracture growth and fracture network geometry. We use double-torsion (DT) load relaxation tests under ambient air conditions to measure the mode-I fracture toughness (KIC) and subcritical fracture growth index (SCI) of variably altered rock samples obtained from outcrop in Dixie Valley, NV. Samples from southern Dixie Valley include 1) weakly altered granite, characterized by minor sericite in plagioclase, albitization and vacuolization of feldspars, and incomplete replacement of biotite with chlorite, and 2) granite from an area of locally intense propylitic alteration with chlorite-calcite-hematite-epidote assemblages. We also evaluated samples of completely silicified gabbro obtained from the Dixie Comstock epithermal gold deposit. In the weakly altered granite KIC and SCI are 1.3 ±0.2 MPam1/2 (n=8) and 59 ±25 (n=29), respectively. In the propylitic assemblage KIC is reduced to 0.6 ±0.1 MPam1/2 (n=11), and the SCI increased to 75 ±36 (n = 33). In both cases, the altered materials have lower fracture toughness and higher SCI than is reported for common geomechanical standards such as Westerly Granite (KIC ~1.7 MPam1/2; SCI ~48). Preliminary analysis of the silicified gabbro shows a significant increase in fracture toughness, 3.6 ±0.4 MPam1/2 (n=2), and SCI, 102 ±45 (n=19), compared to published values for gabbro (2.9 MPam1/2 and SCI = 32). These results suggest that mineralogical and textural changes associated with different alteration assemblages may result in spatially variable rates of fracture

  7. Numerical Fracture Analysis of Cryogenically Treated Alloy Steel Weldments

    International Nuclear Information System (INIS)

    Rasool Mohideen, S; Thamizhmanii, S; Muhammed Abdul Fatah, M.M; Saidin, W. Najmuddin W.

    2016-01-01

    Cryogenic treatment is being used commercially in the industries in the last two decades for improving the life of many engineering component such as bearings and cutting tools. Though their influence in improving the wear resistance of tool materials is well established, the effect of treatment on weldments is not much investigated. In the present work, a two dimensional finite element analysis was carried out on the compact tension specimen model for simulating the treatment process and to study the fracture behaviour. The weldments were modelled by thermo- mechanical coupled field analysis for simulating he temperature distribution in the model during weld pool cooling and introducing thermal stresses due to uneven contraction and cooling. The model was subjected to cryogenic treatment by adopting radiation effect. The fracture analysis was carried out using Rice's J- Integral approach. The analysis produced a similar outcome of experimental results i.e. Increase in the fracture toughness of the specimen after cryogenic treatment in the heat affected zone of weldment. (paper)

  8. Hydro-mechanical coupled simulation of hydraulic fracturing using the eXtended Finite Element Method (XFEM)

    Science.gov (United States)

    Youn, Dong Joon

    This thesis presents the development and validation of an advanced hydro-mechanical coupled finite element program analyzing hydraulic fracture propagation within unconventional hydrocarbon formations under various conditions. The realistic modeling of hydraulic fracturing is necessarily required to improve the understanding and efficiency of the stimulation technique. Such modeling remains highly challenging, however, due to factors including the complexity of fracture propagation mechanisms, the coupled behavior of fracture displacement and fluid pressure, the interactions between pre-existing natural and initiated hydraulic fractures and the formation heterogeneity of the target reservoir. In this research, an eXtended Finite Element Method (XFEM) scheme is developed allowing for representation of single or multiple fracture propagations without any need for re-meshing. Also, the coupled flows through the fracture are considered in the program to account for their influence on stresses and deformations along the hydraulic fracture. In this research, a sequential coupling scheme is applied to estimate fracture aperture and fluid pressure with the XFEM. Later, the coupled XFEM program is used to estimate wellbore bottomhole pressure during fracture propagation, and the pressure variations are analyzed to determine the geometry and performance of the hydraulic fracturing as pressure leak-off test. Finally, material heterogeneity is included into the XFEM program to check the effect of random formation property distributions to the hydraulic fracture geometry. Random field theory is used to create the random realization of the material heterogeneity with the consideration of mean, standard deviation, and property correlation length. These analyses lead to probabilistic information on the response of unconventional reservoirs and offer a more scientific approach regarding risk management for the unconventional reservoir stimulation. The new stochastic approach

  9. Defect vectors and path integrals in fracture mechanics

    International Nuclear Information System (INIS)

    Roche, R.L.

    1979-01-01

    Several criteria have been proposed in Elastic Plastic Fracture Mechanics. One of the most interesting ones is the J 1 criterion where J 1 is a path integral surrounding the crack tip. Other path integrals (or surface integrals in 3D problems) can be used. But all these integrals are introduced on an elastic basis, though they are applied in plasticity. This paper shows that it is possible to introduce these integrals without any reference to the elastic behavior of the material. The method is based on the 'defect vector theory' which is an extension of the energy-momentum tensor theory. (orig.)

  10. Forecasts on service life by fracture mechanics methods

    International Nuclear Information System (INIS)

    Munz, D.

    1985-01-01

    The service life of many component parts can frequently be divided into the stages up to the formation of a crack and of crack propagation. This holds good of fatigue crack, stress corrosion crack, and also in many cases of creep. But often the crack propagation stage is the only one of interest for service life forecasts if cracks must be reckoned with already on putting parts into service. Cracks in welding constructions are typical examples. Crack- and -fracture mechanics deal with the laws underlying crack propagation and provide quantitative information on crack propagation behaviour. (orig./DG) [de

  11. Fracture analysis of the planet support used in a nuclear power plant

    Directory of Open Access Journals (Sweden)

    Zu Shuai

    2016-01-01

    Full Text Available In this paper, the fracture analysis of the planet support, which was made of aluminium alloy and used in an electric actuator, was investigated. The laboratory analysis was conducted to find out whether there are defects generated during manufacturing process. Besides, the finite element analysis was carried out to calculate the maximum tensile stress and compared it with the material strength. The mechanism of the fracture was found to be low-cycle fatigue.

  12. Fatigue fracture of steel after mechanical and ultrasonic strengthening

    International Nuclear Information System (INIS)

    Stotskij, I.M.

    1978-01-01

    Fatigue fracture surfaces of samples after mechanical and ultrasonic strengthening have been studied metallographically and by electron fractography. Studied was the 40Kh steel hardened from 850 deg and then tempered at 180 deg or at 550 deg C. The ultrasound power was 25 kWt, the frequency was 20 kHz, the sample rotation velocity was 39.5 m/min. Mechanical and ultrasonic treatment was found to cause structural changes (formation of a white layer) and deformation of the material under the layer. The fatigue cracks were extending beyond the white layer; their propagation involved generation and coalescence of microcracks on account of segregation of carbides. It is concluded that mechanical and ultrasonic treatment should be used for increasing the fatigue strength of low and average strength materials rather than hardened or low-tempered ones

  13. Reduced Fracture Finite Element Model Analysis of an Efficient Two-Scale Hybrid Embedded Fracture Model

    KAUST Repository

    Amir, Sahar Z.

    2017-06-09

    A Hybrid Embedded Fracture (HEF) model was developed to reduce various computational costs while maintaining physical accuracy (Amir and Sun, 2016). HEF splits the computations into fine scale and coarse scale. Fine scale solves analytically for the matrix-fracture flux exchange parameter. Coarse scale solves for the properties of the entire system. In literature, fractures were assumed to be either vertical or horizontal for simplification (Warren and Root, 1963). Matrix-fracture flux exchange parameter was given few equations built on that assumption (Kazemi, 1968; Lemonnier and Bourbiaux, 2010). However, such simplified cases do not apply directly for actual random fracture shapes, directions, orientations …etc. This paper shows that the HEF fine scale analytic solution (Amir and Sun, 2016) generates the flux exchange parameter found in literature for vertical and horizontal fracture cases. For other fracture cases, the flux exchange parameter changes according to the angle, slop, direction, … etc. This conclusion rises from the analysis of both: the Discrete Fracture Network (DFN) and the HEF schemes. The behavior of both schemes is analyzed with exactly similar fracture conditions and the results are shown and discussed. Then, a generalization is illustrated for any slightly compressible single-phase fluid within fractured porous media and its results are discussed.

  14. Reduced Fracture Finite Element Model Analysis of an Efficient Two-Scale Hybrid Embedded Fracture Model

    KAUST Repository

    Amir, Sahar Z.; Chen, Huangxin; Sun, Shuyu

    2017-01-01

    A Hybrid Embedded Fracture (HEF) model was developed to reduce various computational costs while maintaining physical accuracy (Amir and Sun, 2016). HEF splits the computations into fine scale and coarse scale. Fine scale solves analytically for the matrix-fracture flux exchange parameter. Coarse scale solves for the properties of the entire system. In literature, fractures were assumed to be either vertical or horizontal for simplification (Warren and Root, 1963). Matrix-fracture flux exchange parameter was given few equations built on that assumption (Kazemi, 1968; Lemonnier and Bourbiaux, 2010). However, such simplified cases do not apply directly for actual random fracture shapes, directions, orientations …etc. This paper shows that the HEF fine scale analytic solution (Amir and Sun, 2016) generates the flux exchange parameter found in literature for vertical and horizontal fracture cases. For other fracture cases, the flux exchange parameter changes according to the angle, slop, direction, … etc. This conclusion rises from the analysis of both: the Discrete Fracture Network (DFN) and the HEF schemes. The behavior of both schemes is analyzed with exactly similar fracture conditions and the results are shown and discussed. Then, a generalization is illustrated for any slightly compressible single-phase fluid within fractured porous media and its results are discussed.

  15. Practical application of fracture mechanics with consideration of multiaxiality of stress state to degraded nuclear piping

    International Nuclear Information System (INIS)

    Kussmaul, K.; Blind, D.; Herter, K.H.; Eisele, U.; Schuler, X.

    1995-01-01

    Within the scope of a research project nuclear piping components (T-branches and elbows) with dimensions like the primary coolant lines of PWR plants were investigated. In addition to the experimental full scale tests, extensive numerical calculations by means of the finite element method (FEM) as well as fracture mechanics analyses were performed. The applicability of these methods was verified by comparison with the experimental results. The calculation of fracture mechanics parameters as well as the calculated component stress enabled a statement on crack initiation. The failure behavior could be evaluated by means of the multiaxiality of stress state in the ligament (gradient of the quotient of the multiaxiality of stress state q). With respect to practical application on other pressurized components it is shown how to use the procedure (e.g. in a LBB analysis). A quantitative assessment with regard to crack initiation is possible by comparison of the effective crack initiation value J ieff with the calculated component stress. If the multiaxiality of stress state and the q gradient in the ligament of the fracture ligament of the fracture mechanics specimen and the pressurized component to be evaluated is comparable a quantitative assessment is possible as for crack extension and maximum load. If there is no comparability of the gradients a qualitative assessment is possible for the failure behavior

  16. Plain film analysis of acetabular fracture

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Chang Soo; Han, Sang Suk; Yoon, Eu Giene; Cha, Seong Sook; Eun, Tchoong Kie; Chung, Duck Hwan [Inje Medical College Paik Hospital, Pusan (Korea, Republic of)

    1986-02-15

    Acetabular fracture can result in severe limitation of the motion of the hip joint, which supports total weight of human body. Because of different methods of surgical approach according to fracture type, precise interpretation of X-ray films of acetabular fracture is required. We reviewed 38 cases of simple X-ray films showing acetabular fracture. The results were as follows: 1. Almost 60% of the cases-were in their 2nd and 3rd decades. 2. Twenty cases were male, and 18 cases were female. 3. The most common cause of the injury was traffic accident (33 cases, 86.8%), followed by fall down (4 cases, 10.5%), and slip down (1 case, 2.7%). 4. Elementary fractures were 21 cases (55.3%), and associated fractures were 17 cases (44.7%). 5. Among elementary fractures, posterior wall fractures were 9 cases (23.7%), followed by anterior column fractures (8 cases, 21.1%), anterior wall fractures (4 cases, 10.5%). 6. Among associated fractures, T-shaped fractures were 8 cases (21.1%), followed by both column fractures (6 cases, 15.8%), anterior and hemitransverse fractures (3 cases, 7.8%). 7. Other pelvic bone fractures associated with the acetabular fracture were as follows: fractures of contralateral pubic rami (6 cases, 15.8%) contralateral iliac bone (1 case, 2.6%) and ipsilateral iliac bone (1 case, 2.6%). 8. Injuries of other organs adjacent to the acetabulum were as follows: rupture of the bladder (3 cases, 7.9%), urethra (2 cases, 5.3%) and uterus (1 cases, 2.6%)

  17. Plain film analysis of acetabular fracture

    International Nuclear Information System (INIS)

    Kim, Chang Soo; Han, Sang Suk; Yoon, Eu Giene; Cha, Seong Sook; Eun, Tchoong Kie; Chung, Duck Hwan

    1986-01-01

    Acetabular fracture can result in severe limitation of the motion of the hip joint, which supports total weight of human body. Because of different methods of surgical approach according to fracture type, precise interpretation of X-ray films of acetabular fracture is required. We reviewed 38 cases of simple X-ray films showing acetabular fracture. The results were as follows: 1. Almost 60% of the cases-were in their 2nd and 3rd decades. 2. Twenty cases were male, and 18 cases were female. 3. The most common cause of the injury was traffic accident (33 cases, 86.8%), followed by fall down (4 cases, 10.5%), and slip down (1 case, 2.7%). 4. Elementary fractures were 21 cases (55.3%), and associated fractures were 17 cases (44.7%). 5. Among elementary fractures, posterior wall fractures were 9 cases (23.7%), followed by anterior column fractures (8 cases, 21.1%), anterior wall fractures (4 cases, 10.5%). 6. Among associated fractures, T-shaped fractures were 8 cases (21.1%), followed by both column fractures (6 cases, 15.8%), anterior and hemitransverse fractures (3 cases, 7.8%). 7. Other pelvic bone fractures associated with the acetabular fracture were as follows: fractures of contralateral pubic rami (6 cases, 15.8%) contralateral iliac bone (1 case, 2.6%) and ipsilateral iliac bone (1 case, 2.6%). 8. Injuries of other organs adjacent to the acetabulum were as follows: rupture of the bladder (3 cases, 7.9%), urethra (2 cases, 5.3%) and uterus (1 cases, 2.6%).

  18. 3-D description of fracture surfaces and stress-sensitivity analysis for naturally fractured reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, S.Q.; Jioa, D.; Meng, Y.F.; Fan, Y.

    1997-08-01

    Three kinds of reservoir cores (limestone, sandstone, and shale with natural fractures) were used to study the effect of morphology of fracture surfaces on stress sensitivity. The cores, obtained from the reservoirs with depths of 2170 to 2300 m, have fractures which are mated on a large scale, but unmated on a fine scale. A specially designed photoelectric scanner with a computer was used to describe the topography of the fracture surfaces. Then, theoretical analysis of the fracture closure was carried out based on the fracture topography generated. The scanning results show that the asperity has almost normal distributions for all three types of samples. For the tested samples, the fracture closure predicted by the elastic-contact theory is different from the laboratory measurements because plastic deformation of the aspirates plays an important role under the testing range of normal stresses. In this work, the traditionally used elastic-contact theory has been modified to better predict the stress sensitivity of reservoir fractures. Analysis shows that the standard deviation of the probability density function of asperity distribution has a great effect on the fracture closure rate.

  19. Fracture mechanisms in multilayer phosphorene assemblies: from brittle to ductile.

    Science.gov (United States)

    Liu, Ning; Hong, Jiawang; Zeng, Xiaowei; Pidaparti, Ramana; Wang, Xianqiao

    2017-05-24

    The outstanding mechanical performance of nacre has stimulated numerous studies on the design of artificial nacres. Phosphorene, a new two-dimensional (2D) material, has a crystalline in-plane structure and non-bonded interaction between adjacent flakes. Therefore, multi-layer phosphorene assemblies (MLPs), in which phosphorene flakes are piled up in a staggered manner, may exhibit outstanding mechanical performance, especially exceptional toughness. Therefore, molecular dynamics simulations are performed to study the dependence of the mechanical properties on the overlap distance between adjacent phosphorene layers and the number of phosphorene flakes per layer. The results indicate that when the flake number is equal to 1, a transition of fracture patterns is observed by increasing the overlap distance, from a ductile failure controlled by interfacial friction to a brittle failure dominated by the breakage of covalent bonds inside phosphorene flakes. Moreover, the failure pattern can be tuned by changing the number of flakes in each phosphorene layer. The results imply that the ultimate strength follows a power law with the exponent -0.5 in terms of the flake number, which is in good agreement with our analytical model. Furthermore, the flake number in each phosphorene layer is optimized as 2 when the temperature is 1 K in order to potentially achieve both high toughness and strength. Moreover, our results regarding the relations between mechanical performance and overlap distance can be explained well using a shear-lag model. However, it should be pointed out that increasing the temperature of MLPs could cause the transition of fracture patterns from ductile to brittle. Therefore, the optimal flake number depends heavily on temperature to achieve both its outstanding strength and toughness. Overall, our findings unveil the fundamental mechanism at the nanoscale for MLPs as well as provide a method to design phosphorene-based structures with targeted properties

  20. Application of fracture mechanics to weldments; Bruchmechanische Bewertung von Schweissverbindungen

    Energy Technology Data Exchange (ETDEWEB)

    Zerbst, U.; Kocak, M. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Werkstofforschung; Huebner, P. [Technische Univ. Bergakademie Freiberg (Germany)

    2002-07-01

    Weldments have been a major topic of engineering fracture mechanics research for many years as it shows up in the immense number of scientific papers published recently. Part of this generated knowledge has already been implemented in some industrial codes and standards. The focussing on weldments has its own reason in the utmost importance of this class of components in many industrial fields, but also in its susceptibility to the formation of defects during manufacturing and cracks in service, which promotes the danger of component failure. The present report is addressed to designers and material testers to provide updated information on the present state-of-the-art of fracture mechanics application to weldments. (orig.) [German] Schweissverbindungen bilden seit vielen Jahren einen Schwerpunkt der anwendungsnahen bruchmechanischen Forschung, was seinen Niederschlag in einer nahezu unuebersehbaren Fuelle an wissenschaftlichen Publikationen findet. Ein Teil der Ergebnisse hat bereits Eingang in industrienahe bruchmechanische Bewertungsvorschriften gefunden. Die Konzentration auf Schweissverbindungen hat ihre Ursache in der immensen Bedeutung dieser Bauteilklasse fuer viele Gebiete der Volkswirtschaft, aber auch in ihrer besonderen Anfaelligkeit zur Rissbildung in der Fertigung und im Betrieb und damit hinsichtlich der Gefahr von Bauteilversagen. Der vorliegende Beitrag wendet sich an Konstrukteure und Werkstoffpruefer, die einen Einblick in den gegenwaertigen Stand der Ingenieurbruchmechanik an Schweissverbindungen gewinnen wollen. (orig.)

  1. Hot ductility and fracture mechanisms of a structural steel

    International Nuclear Information System (INIS)

    Calvo, J.; Cabrera, J. M.; Prado, J. M.

    2006-01-01

    The hot ductility of a structural steel produced from scrap recycling has been studied to determine the origin of the transverse cracks in the corners that appeared in some billets. Samples extracted both from a billet with transverse cracks and from a billet with no external damage were tested. To evaluate the influence of residual elements and inclusions, the steel was compared to another one impurity free. Reduction in area of the samples tensile tested to the fracture was taken as a measure of the hot ductility. The tests were carried out at temperatures ranging from 1000 degree centigree to 650 degree centigree and at a strain rate of 1.10-3 s-1. The fracture surfaces of the tested samples were observed by scanning electron microscopy in order to determine the embrittling mechanisms that could be acting. The steel with residuals and impurities exhibited lower ductility values for a wider temperature range than the clean steel. The embrittling mechanisms also changed as compared to the impurity free steel. (Author)

  2. Fracturing Fluid Leak-off for Deep Volcanic Rock in Zhungeer Basin: Mechanism and Control Method

    Directory of Open Access Journals (Sweden)

    Huang Bo

    2017-01-01

    Full Text Available The deep volcanic reservoir in Zhungeer Basin is buried in over 4000m depth, which is characterized by complex lithology (breccia, andesite, basalt, etc., high elastic modulus and massive natural fractures. During hydraulic fracturing, hydraulic fracture will propagate and natural fractures will be triggered by the increasing net pressure. However, the extension of fractures, especially natural fractures, would aggravate the leak-off effect of fracturing fluid, and consequently decrease the fracturing success rate. 4 out of 12 fracturing wells in the field have failed to add enough proppants due to fluid loss. In order to increase the success rate and efficiency of hydraulic fracturing for deep volcanic reservoir, based on theoretical and experimental method, the mechanism of fracturing fluid leak-off is deeply studied. We propose a dualistic proppant scheme and employ the fluid loss reducer to control the fluid leak-off in macro-fractures and micro-fractures respectively. The proposed technique remarkably improved the success rate in deep volcanic rock fracturing. It bears important theoretical value and practical significance to improve the hydraulic fracturing design for deep volcanic reservoir.

  3. CT for diagnosing fractures of the undersurface of the talus and mechanism of injury

    International Nuclear Information System (INIS)

    Okamoto, Hideaki; Shibata, Yoshimori; Nishi, Genzaburo; Tago, Kyoji; Tsuchiya, Daiji; Chiba, Takehiro; Okumura, Hisashi; Ikeda, Takeshi; Wada, Ikuo

    2000-01-01

    Talus fractures whose fracture lines extend to the subtalar joint, except fractures of the neck and the body of the talus, are defined as fractures of the lower portion of the talus. It is difficult to make a correctly diagnosis of inferior fractures of the talus by plain radiography or tomography alone. The author encountered 12 cases of inferior fractures of the talus between 1989 and 1997, and CT imaging in 2 directions, in the horizontal and frontal plane, was useful in making the diagnosis. The correct diagnosis rate was 100%, and differentiation of the site and extent of the fractures was possible. Based on the CT findings, the fractures were classified into 8 types (fractures of the lateral process of the talus, fractures of the medial tubercle, fractures of the posterior process, and combinations of the above, and comminuted fractures). The mechanism of the injuries was also investigated, and the fractures of the lateral process of the talus seemed to have been caused by excessive eversion force on the ankle joint, with the lateral process becoming trapped between the fibula and the calcaneus. Medial tubercle fractures also seemed to be caused by forcible inversion of the ankle, with the tip of the medial malleous impacting and the medial tubercle being trapped between it and the sustentaculum tali. The comminuted fractures seem to have been caused by axial compression added to various of external forces. (K.H.)

  4. CT for diagnosing fractures of the undersurface of the talus and mechanism of injury

    Energy Technology Data Exchange (ETDEWEB)

    Okamoto, Hideaki; Shibata, Yoshimori; Nishi, Genzaburo; Tago, Kyoji; Tsuchiya, Daiji; Chiba, Takehiro; Okumura, Hisashi [Aichiken Koseiren Kainan Hospital, Yatomi (Japan); Ikeda, Takeshi; Wada, Ikuo

    2000-02-01

    Talus fractures whose fracture lines extend to the subtalar joint, except fractures of the neck and the body of the talus, are defined as fractures of the lower portion of the talus. It is difficult to make a correctly diagnosis of inferior fractures of the talus by plain radiography or tomography alone. The author encountered 12 cases of inferior fractures of the talus between 1989 and 1997, and CT imaging in 2 directions, in the horizontal and frontal plane, was useful in making the diagnosis. The correct diagnosis rate was 100%, and differentiation of the site and extent of the fractures was possible. Based on the CT findings, the fractures were classified into 8 types (fractures of the lateral process of the talus, fractures of the medial tubercle, fractures of the posterior process, and combinations of the above, and comminuted fractures). The mechanism of the injuries was also investigated, and the fractures of the lateral process of the talus seemed to have been caused by excessive eversion force on the ankle joint, with the lateral process becoming trapped between the fibula and the calcaneus. Medial tubercle fractures also seemed to be caused by forcible inversion of the ankle, with the tip of the medial malleous impacting and the medial tubercle being trapped between it and the sustentaculum tali. The comminuted fractures seem to have been caused by axial compression added to various of external forces. (K.H.)

  5. Probabilistic fracture mechanics of nuclear structural components. Consideration of transition from embedded crack to surface crack

    International Nuclear Information System (INIS)

    Yagawa, Genki; Yoshimura, Shinobu; Kanto, Yasuhiro

    1998-01-01

    This paper describes a probabilistic fracture mechanics (PFM) analysis of aged nuclear reactor pressure vessel (RPV) material. New interpolation formulas are first derived for both embedded elliptical surface cracks and semi-elliptical surface cracks. To investigate effects of transition from embedded crack to surface crack in PFM analyses, one of PFM round-robin problems set by JSME-RC111 committee, i.e. 'aged RPV under normal and upset operating conditions' is solved, employing the interpolation formulas. (author)

  6. Coupled Flow and Mechanics in Porous and Fractured Media*

    Science.gov (United States)

    Martinez, M. J.; Newell, P.; Bishop, J.

    2012-12-01

    Numerical models describing subsurface flow through deformable porous materials are important for understanding and enabling energy security and climate security. Some applications of current interest come from such diverse areas as geologic sequestration of anthropogenic CO2, hydro-fracturing for stimulation of hydrocarbon reservoirs, and modeling electrochemistry-induced swelling of fluid-filled porous electrodes. Induced stress fields in any of these applications can lead to structural failure and fracture. The ultimate goal of this research is to model evolving faults and fracture networks and flow within the networks while coupling to flow and mechanics within the intact porous structure. We report here on a new computational capability for coupling of multiphase porous flow with geomechanics including assessment of over-pressure-induced structural damage. The geomechanics is coupled to the flow via the variation in the fluid pore pressures, whereas the flow problem is coupled to mechanics by the concomitant material strains which alter the pore volume (porosity field) and hence the permeability field. For linear elastic solid mechanics a monolithic coupling strategy is utilized. For nonlinear elastic/plastic and fractured media, a segregated coupling is presented. To facilitate coupling with disparate flow and mechanics time scales, the coupling strategy allows for different time steps in the flow solve compared to the mechanics solve. If time steps are synchronized, the controller allows user-specified intra-time-step iterations. The iterative coupling is dynamically controlled based on a norm measuring the degree of variation in the deformed porosity. The model is applied for evaluation of the integrity of jointed caprock systems during CO2 sequestration operations. Creation or reactivation of joints can lead to enhanced pathways for leakage. Similarly, over-pressures can induce flow along faults. Fluid flow rates in fractures are strongly dependent on the

  7. Fatigue and fracture mechanics in pressure vessels and piping. PVP-Volume 304

    International Nuclear Information System (INIS)

    Mehta, H.S.; Wilkowski, G.; Takezono, S.; Bloom, J.; Yoon, K.; Aoki, S.; Rahman, S.; Nakamura, T.; Brust, F.; Yoshimura, S.

    1995-01-01

    Fracture mechanics and fatigue evaluations are an important part of the structural integrity analyses to assure safe operation of pressure vessels and piping components during their service life. The paper presented in this volume illustrate the application of fatigue and fracture mechanics techniques to assess the structural integrity of a wide variety of Pressure Vessels and Piping components. The papers are organized in six sections: (1) fatigue and fracture--vessels; (2) fatigue and fracture--piping; (3) fatigue and fracture--material property evaluations; (4) constraint effects in fracture mechanics; (5) probabilistic fracture mechanics analyses; and (6) user's experience with failure assessment diagrams. Separate abstracts were prepared for most of the papers in this book

  8. Fracture mechanics of piezoelectric solids with interface cracks

    CERN Document Server

    Govorukha, Volodymyr; Loboda, Volodymyr; Lapusta, Yuri

    2017-01-01

    This book provides a comprehensive study of cracks situated at the interface of two piezoelectric materials. It discusses different electric boundary conditions along the crack faces, in particular the cases of electrically permeable, impermeable, partially permeable, and conducting cracks. The book also elaborates on a new technique for the determination of electromechanical fields at the tips of interface cracks in finite sized piezoceramic bodies of arbitrary shape under different load types. It solves scientific problems of solid mechanics in connection with the investigation of electromechanical fields in piezoceramic bodies with interface cracks, and develops calculation models and solution methods for plane fracture mechanical problems for piecewise homogeneous piezoceramic bodies with cracks at the interfaces. It discusses the “open” crack model, which leads to a physically unrealistic oscillating singularity at the crack tips, and the contact zone model for in-plane straight interface cracks betw...

  9. Fractal analysis of fracture increasing spontaneous imbibition in porous media with gas-saturated

    KAUST Repository

    Cai, Jianchao; Sun, Shuyu

    2013-01-01

    Spontaneous imbibition (SI) of wetting liquid into matrix blocks due to capillary pressure is regarded as an important recovery mechanism in low permeability fractured reservoir. In this paper, an analytical model is proposed for characterizing SI horizontally from a single plane fracture into gas-saturated matrix blocks. The presented model is based on the fractal character of pores in porous matrix, with gravity force included in the entire imbibition process. The accumulated mass of wetting liquid imbibed into matrix blocks is related to a number of factors such as contact area, pore fractal dimension, tortuosity, maximum pore size, porosity, liquid density and viscosity, surface tension, contact angle, as well as height and tilt angle of the fracture. The mechanism of fracture-enhanced SI is analyzed accordingly. Because of the effect of fracture, the gravity force is positive to imbibition process. Additionally, the farther away from the fracture top of the pore, the more influential the hydrostatic pressure is upon the imbibition action. The presented fractal analysis of horizontal spontaneous imbibition from a single fracture could also shed light on the scaling study of the mass transfer function between matrix and fracture system of fractured reservoirs. © 2013 World Scientific Publishing Company.

  10. Fractal analysis of fracture increasing spontaneous imbibition in porous media with gas-saturated

    KAUST Repository

    Cai, Jianchao

    2013-08-01

    Spontaneous imbibition (SI) of wetting liquid into matrix blocks due to capillary pressure is regarded as an important recovery mechanism in low permeability fractured reservoir. In this paper, an analytical model is proposed for characterizing SI horizontally from a single plane fracture into gas-saturated matrix blocks. The presented model is based on the fractal character of pores in porous matrix, with gravity force included in the entire imbibition process. The accumulated mass of wetting liquid imbibed into matrix blocks is related to a number of factors such as contact area, pore fractal dimension, tortuosity, maximum pore size, porosity, liquid density and viscosity, surface tension, contact angle, as well as height and tilt angle of the fracture. The mechanism of fracture-enhanced SI is analyzed accordingly. Because of the effect of fracture, the gravity force is positive to imbibition process. Additionally, the farther away from the fracture top of the pore, the more influential the hydrostatic pressure is upon the imbibition action. The presented fractal analysis of horizontal spontaneous imbibition from a single fracture could also shed light on the scaling study of the mass transfer function between matrix and fracture system of fractured reservoirs. © 2013 World Scientific Publishing Company.

  11. Tibial Fractures in Alpine Skiing and Snowboarding in Finland: A Retrospective Study on Fracture Types and Injury Mechanisms in 363 Patients.

    Science.gov (United States)

    Stenroos, A; Pakarinen, H; Jalkanen, J; Mälkiä, T; Handolin, L

    2016-09-01

    Alpine skiing and snowboarding share the hazards of accidents accounting for tibial fractures. The aim of this study was to evaluate the fracture patterns and mechanisms of injury of tibial fractures taking place in downhill skiing and snowboarding. All patients with tibial fracture due to alpine skiing or snowboarding accident treated in four trauma centers next to the largest ski resorts in Finland were analyzed between 2006 and 2012. The hospital records were retrospectively reviewed for data collection: equipment used (skis or snowboard), age, gender, and mechanism of injury. Fractures were classified according to AO-classification. There were 342 skiing and 30 snowboarding related tibial fractures in 363 patients. Tibial shaft fracture was the most common fracture among skiers (n = 215, 63%), followed by proximal tibial fractures (n = 92, 27%). Snowboarders were most likely to suffer from proximal tibial fracture (13, 43%) or tibial shaft fracture (11, 37%). Snowboarders were also more likely than skiers to suffer complex AO type C fractures (23% vs 9%, p jumping (46%). The most important finding was the relatively high number of the tibial plateau fractures among adult skiers. The fracture patterns between snowboarding and skiing were different; the most common fracture type in skiers was spiral tibial shaft fracture compared to proximal tibial fractures in snowboarders. Children had more simple fractures than adults. © The Finnish Surgical Society 2016.

  12. Anisotropic characterization of rock fracture surfaces subjected to profile analysis

    International Nuclear Information System (INIS)

    Zhou, H.W.; Xie, H.

    2004-01-01

    The mechanical parameters of a rock fracture are dependent on its surface roughness anisotropy. In this Letter, we show how quantitatively describe the anisotropy of a rock fracture surface. A parameter, referred to as the index for the accumulation power spectral density psd*, is proposed to characterize the anisotropy of a rock fracture surface. Variation of psd*, with orientation angle θ of sampling, is also discussed

  13. Evaluation of viscoplastic fracture criteria and analysis methods

    International Nuclear Information System (INIS)

    Bass, B.R.; Pugh, C.E.; Keeney-Walker, J.; Dexter, R.J.; O'Donoghue, P.E.; Schwartz, C.W.

    1988-01-01

    The role of nonlinear rate-dependent effects in the interpretation of crack run-arrest events in ductile materials is being investigated by the Heavy-Section Steel Technology (HSST) program through development and applications of viscoplastic-dynamic finite element analysis techniques. This paper describes a portion of these studies wherein various viscoplastic constitutive models and several proposed nonlinear fracture criteria are being installed in general purpose (ADINA) and special purpose (VISCRK) finite element computer programs. The formulations of the Bodner-Partom, the Perzyna, and the Robinson constitutive models installed in the HSST computer programs are summarized. This is followed by a description of three integral functions that are candidate fracture parameters. The capabilities of these nonlinear techniques re compared and evaluated through applications to one of the HSST wide-plate crack-arrest tests. Results are presented from benchmark viscoplastic-dynamic wide-plate analyses performed using the ADINA and VISCRK computer programs. Finally, plans are summarized for additional computational and experimental studies to assess the utility of viscoplastic analysis techniques in constructing a transferable inelastic fracture mechanics model for ductile steels. (author)

  14. A three-dimensional coupled thermo-hydro-mechanical model for deformable fractured geothermal systems

    DEFF Research Database (Denmark)

    Salimzadeh, Saeed; Paluszny, Adriana; Nick, Hamidreza M.

    2018-01-01

    A fully coupled thermal-hydraulic-mechanical (THM) finite element model is presented for fractured geothermal reservoirs. Fractures are modelled as surface discontinuities within a three-dimensional matrix. Non-isothermal flow through the rock matrix and fractures are defined and coupled to a mec......A fully coupled thermal-hydraulic-mechanical (THM) finite element model is presented for fractured geothermal reservoirs. Fractures are modelled as surface discontinuities within a three-dimensional matrix. Non-isothermal flow through the rock matrix and fractures are defined and coupled....... The model has been validated against several analytical solutions, and applied to study the effects of the deformable fractures on the injection of cold water in fractured geothermal systems. Results show that the creation of flow channelling due to the thermal volumetric contraction of the rock matrix...

  15. Fracture Analysis of Debonded Sandwich Columns Under Axial Compression

    DEFF Research Database (Denmark)

    May, A.; Avilés, F.; Berggreen, Christian

    A sandwich structure consists of two strong and stiff face sheets bonded to a weak low density core. The large separation between the face sheets provides increased bending rigidity and strength at low weight cost. Thus, sandwich structures frequently present better mechanical properties than...... monolithic structures of the same weight. The vast range of applications of such materials includes wind turbines, marine, and aerospace industries. In this work, geometrically nonlinear finite element analysis is conducted to investigate the fracture parameters and debond propagation of sandwich columns...

  16. Fracture analysis of HFIR beam tube caused by radiation embrittlement

    International Nuclear Information System (INIS)

    Chang, S.J.

    1994-01-01

    With an attempt to estimate the neutron beam tube embrittlement condition for the Oak Ridge High Flux Isotope Reactor (HFIR), fracture mechanics calculations are carried out in this paper. The analysis provides some numerical result on how the tube has been structurally weakened. In this calculation, a lateral impact force is assumed. Numerical result is obtained on how much the critical crack size should be reduced if the beam tube has been subjected to an extended period of irradiation. It is also calculated that buckling strength of the tube is increased, not decreased, with irradiation

  17. Study on predicting residual life of elevator links by fracture mechanics approach

    Energy Technology Data Exchange (ETDEWEB)

    Li Helin; Zhang Yi; Deng Zengjie [China National Petroleum Corp., Xi`an, Shaanxi (China). Tubular Goods Research Center; Jin Dazeng [Xi`an Jiaotong Univ., Xi`an, Shaanxi (China)

    1995-12-31

    On the basis of investigation, failure and fracture analysis of elevator links, residual life prediction of links using fracture mechanics approach is studied, and mechanical properties, fracture toughness value K{sub IC} and fatigue crack propagation rage da/dN of the steel for elevator links are determined. Using the relation between stress intensity factor K{sub I} and the strain-energy release rate, the two-dimensional conversion thickness finite element method has been used to calculate the stress intensity factors K{sub I} for dangerous sections in the ring part of links. Furthermore, the reliability of calculations of the finite element stress intensity factors K{sub I} for dangerous sections of elevator links and the residual life computation for links are verified by fatigue tests of actual links. Finally, the experimental verification of computed results by 150T link fractured at site indicates that the computed critical crack lengths and residual life tally well with those measured and meet the needs of oil drilling.

  18. Fracture mechanics of ceramics. Vol. 8. Microstructure, methods, design, and fatigue

    International Nuclear Information System (INIS)

    Bradt, R.C.; Evans, A.G.; Hasselman, D.P.H.; Lange, F.F.

    1986-01-01

    This paper presents information on the following topics: fracture mechanics and microstructures; non-lubricated sliding wear of Al 2 O 3 , PSZ and SiC; mixed-mode fracture of ceramics; some fracture properties of alumina-containing electrical porcelains; transformation toughening in the Al 2 O 3 -Cr 2 O 3 /ZrO 2 -HfO 2 system; strength toughness relationships for transformation toughened ceramics; tensile strength and notch sensitivity of Mg-PSZ; fracture mechanisms in lead zirconate titanate ceramics; loading-unloading techniques for determining fracture parameters of brittle materials utilizing four-point bend, chevron-notched specimens; application of the potential drop technique to the fracture mechanics of ceramics; ceramics-to-metal bonding from a fracture mechanics perspective; observed changes in fracture strength following laser irradiation and ion beam mixing of Ni overlayers on sintered alpha-SiC; crack growth in single-crystal silicon; a fracture mechanics and non-destructive evaluation investigation of the subcritical-fracture process in rock; slow crack growth in sintered silicon nitride; uniaxial tensile fatigue testing of sintered silicon carbide under cyclic temperature change; and effect of surface corrosion on glass fracture

  19. Development of probabilistic fracture mechanics code PASCAL and user's manual

    Energy Technology Data Exchange (ETDEWEB)

    Shibata, Katsuyuki; Onizawa, Kunio [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Li, Yinsheng; Kato, Daisuke [Fuji Research Institute Corporation, Tokyo (Japan)

    2001-03-01

    As a part of the aging and structural integrity research for LWR components, a new PFM (Probabilistic Fracture Mechanics) code PASCAL (PFM Analysis of Structural Components in Aging LWR) has been developed since FY1996. This code evaluates the failure probability of an aged reactor pressure vessel subjected to transient loading such as PTS (Pressurized Thermal Shock). The development of the code has been aimed to improve the accuracy and reliability of analysis by introducing new analysis methodologies and algorithms considering the recent development in the fracture mechanics methodologies and computer performance. The code has some new functions in optimized sampling and cell dividing procedure in stratified Monte Carlo simulation, elastic-plastic fracture criterion of R6 method, extension analysis models in semi-elliptical crack, evaluation of effect of thermal annealing and etc. In addition, an input data generator of temperature and stress distribution time histories was also prepared in the code. Functions and performance of the code have been confirmed based on the verification analyses and some case studies on the influence parameters. The present phase of the development will be completed in FY2000. Thus this report provides the user's manual and theoretical background of the code. (author)

  20. Hydro-thermo-mechanical response of a fractured rock block

    International Nuclear Information System (INIS)

    Kelkar, S.; Zyvoloski, G.

    1990-01-01

    Hydro-thermo-mechanical effects in fractured rocks are important in many engineering applications and geophysical processes. Modeling these effects is made difficult by the fact that the governing equations are nonlinear and coupled, and the problems to be solved are three dimensional. In this paper we describe a numerical code developed for this purpose. The code is finite element based to allow for complicated geometries, and the time differencing is implicit, allowing for large time steps. The use of state-of-the-art equation solvers has resulted in a practical code. The code is capable of fully three dimensional simulations, however, in this paper we consider only the case of two dimensional heat and mass flow coupled to one dimensional deformation. Partial verification of the code is obtained by comparison with published semianalytical results. Several examples are presented to demonstrate the effects of matrix expansion, due to pore pressure and heating, on fracture opening due to fluid injection. 16 refs., 11 figs

  1. Fracture analysis of concrete gravity dam under earthquake induced ...

    African Journals Online (AJOL)

    In this paper, seismic fracture behavior of the concrete gravity dam using finite element (2D) theory has been studied. Bazant model which is non-linear fracture mechanics criteria as a measure of growth and smeared crack was chosen to develop profiles of the crack. Behavior of stress - strain curves of concrete as a ...

  2. The COD concept and its application to fracture mechanical evaluation of cracked components

    International Nuclear Information System (INIS)

    Kockelmann, H.

    1984-01-01

    Based on a comprehensive literature study, this report critically evaluates the current state of experiences with the COD concept in fracture mechanics. First the concept is explained and the procedure of materials testing with a view to fracture mechanics is discussed in detail with emphasis on: The definition of crack shape modification; the procedure to detect crack modification, with subsequent comparison; the determination of material characteristics; the impact on the characteristics of the crack tip opening and the dispersion of results. The correlation between crack tip opening characteristics and notch impact strength is explained, and the methods applied for analysis of the streses affecting the structural components are shown. The design-based and failure threshold curves and the treatment of real crack geometries are also discussed. Problems still to be solved are shown. (orig./HP) [de

  3. Analysis of nature of brazed joints fracture under operating conditions

    International Nuclear Information System (INIS)

    Orlov, A.V.; Gura, P.M.

    1985-01-01

    Technique establishing causes leading to brazed joint fracture in pressure boundary components, operating under heavy conditions of high temperature and corrosive medium is described. Some cases of tube brazed joint fractures in a superheater of 12Kh1MF and 08Kh18N10T steels are considered. The attention is paid on using metallography for determination of mechanical or corrosion fracture properties. The diagram is developed permitting to take into account the interrelation between the fracture area in the given zone and its strength

  4. Well test analysis in fractured media

    Energy Technology Data Exchange (ETDEWEB)

    Karasaki, K.

    1987-04-01

    The behavior of fracture systems under well test conditions and methods for analyzing well test data from fractured media are investigated. Several analytical models are developed to be used for analyzing well test data from fractured media. Numerical tools that may be used to simulate fluid flow in fractured media are also presented. Three types of composite models for constant flux tests are investigated. These models are based on the assumption that a fracture system under well test conditions may be represented by two concentric regions, one representing a small number of fractures that dominates flow near the well, and the other representing average conditions farther away from the well. Type curves are presented that can be used to find the flow parameters of these two regions and the extent of the inner concentric region. Several slug test models with different geometric conditions that may be present in fractured media are also investigated. A finite element model that can simulate transient fluid flow in fracture networks is used to study the behavior of various two-dimensional fracture systems under well test conditions. A mesh generator that can be used to model mass and heat flow in a fractured-porous media is presented.

  5. Reliability of Source Mechanisms for a Hydraulic Fracturing Dataset

    Science.gov (United States)

    Eyre, T.; Van der Baan, M.

    2016-12-01

    Non-double-couple components have been inferred for induced seismicity due to fluid injection, yet these components are often poorly constrained due to the acquisition geometry. Likewise non-double-couple components in microseismic recordings are not uncommon. Microseismic source mechanisms provide an insight into the fracturing behaviour of a hydraulically stimulated reservoir. However, source inversion in a hydraulic fracturing environment is complicated by the likelihood of volumetric contributions to the source due to the presence of high pressure fluids, which greatly increases the possible solution space and therefore the non-uniqueness of the solutions. Microseismic data is usually recorded on either 2D surface or borehole arrays of sensors. In many cases, surface arrays appear to constrain source mechanisms with high shear components, whereas borehole arrays tend to constrain more variable mechanisms including those with high tensile components. The abilities of each geometry to constrain the true source mechanisms are therefore called into question.The ability to distinguish between shear and tensile source mechanisms with different acquisition geometries is investigated using synthetic data. For both inversions, both P- and S- wave amplitudes recorded on three component sensors need to be included to obtain reliable solutions. Surface arrays appear to give more reliable solutions due to a greater sampling of the focal sphere, but in reality tend to record signals with a low signal to noise ratio. Borehole arrays can produce acceptable results, however the reliability is much more affected by relative source-receiver locations and source orientation, with biases produced in many of the solutions. Therefore more care must be taken when interpreting results.These findings are taken into account when interpreting a microseismic dataset of 470 events recorded by two vertical borehole arrays monitoring a horizontal treatment well. Source locations and

  6. Fracture mechanics of hydroxyapatite single crystals under geometric confinement.

    Science.gov (United States)

    Libonati, Flavia; Nair, Arun K; Vergani, Laura; Buehler, Markus J

    2013-04-01

    Geometric confinement to the nanoscale, a concept that refers to the characteristic dimensions of structural features of materials at this length scale, has been shown to control the mechanical behavior of many biological materials or their building blocks, and such effects have also been suggested to play a crucial role in enhancing the strength and toughness of bone. Here we study the effect of geometric confinement on the fracture mechanism of hydroxyapatite (HAP) crystals that form the mineralized phase in bone. We report a series of molecular simulations of HAP crystals with an edge crack on the (001) plane under tensile loading, and we systematically vary the sample height whilst keeping the sample and the crack length constant. We find that by decreasing the sample height the stress concentration at the tip of the crack disappears for samples with a height smaller than 4.15nm, below which the material shows a different failure mode characterized by a more ductile mechanism with much larger failure strains, and the strength approaching that of a flaw-less crystal. This study directly confirms an earlier suggestion of a flaw-tolerant state that appears under geometric confinement and may explain the mechanical stability of the reinforcing HAP platelets in bone. Copyright © 2012 Elsevier Ltd. All rights reserved.

  7. Mezzo-scopic Analysis of Fracture Toughness in Steels

    Directory of Open Access Journals (Sweden)

    Miyata Takashi

    2002-01-01

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

  8. Dispersion analysis for waves propagated in fractured media

    Energy Technology Data Exchange (ETDEWEB)

    Lesniak, A; Niitsuma, H [Tohoku University, Sendai (Japan). Faculty of Engineering

    1996-05-01

    Dispersion of velocity is defined as a variation of the phase velocity with frequency. This paper describes the dispersion analysis of compressional body waves propagated in the heterogeneous fractured media. The new method proposed and discussed here permitted the evaluation of the variation in P wave arrival with frequency. For this processing method, any information about the attenuation of the medium are not required, and only an assumption of weak heterogeneity is important. It was shown that different mechanisms of dispersion can be distinguished and its value can be quantitatively estimated. Although the frequency used in this study was lower than those in most previous experiments reported in literature, the evaluated dispersion was large. It was suggested that such a large dispersion may be caused by the velocity structure of the media studied and by frequency dependent processes in a highly fractured zone. It was demonstrated that the present method can be used in the evaluation of subsurface fracture systems or characterization of any kind of heterogeneities. 10 refs., 6 figs.

  9. Application of fracture-mechanics principles to austenitic steels

    International Nuclear Information System (INIS)

    Schwalbe, K.H.; Cornec, A.; Baustian, K.

    1996-01-01

    Recent experimental and analytical work mainly carried out at GKSS and TH Darmstadt is used to check the usefulness of fracture mechanics methods as developed for more conventional materials, such as ferritic steels and aluminium alloys. Finite element calculations serve for quantifying J validity limits; they are a function of constraint conditions and strain hardening properties. Crack growth studies show the ability of the J-integral, the modified J-integral, J(M), and of the crack tip opening displacement, CTOD delta(5), to generate unique, i.e. size-independent, R-curves. It is also shown that the delta(5)-type CTOD technique yields values close to the standardised CTOD. Finally, the Engineering Treatment Model is used to estimate delta(5) and J as driving force parameters. Special attention is given to the power law representation of actual stress/strain curves. (author)

  10. Investigations on the influence of the stress state on fracture-mechanical values

    International Nuclear Information System (INIS)

    Schmidt, P.

    1979-01-01

    Fracture toughness obtained from specimen can be applied to construction elements only when the same stress state exists. In standardised fracture-mechanical tests plain strain is realised. Using the stress intensity factor, a critical crack length or a critical load can be obtained. Above these values a crack propagates in an unstable way. The specimen are tested under uni-axial load. In this paper investigations have been made whether a biaxial load increases the stress state over the plain strain and whether consequently a decrease of the critical fracture toughness and a shift of the temperatures Tsub(g)sub(y) and Tsub(s) results which characterise the fracture behaviour of steel. In order to answer these questions the tests were made which induced due to their geometry an additional nominal stress parallel to the crack front in spite of uni-axial loading. The results were compared with those from specimen without an additional nominal stress and having in their cross section under same test conditions nearly the same plain strain. The fracture toughness of both specimen types were compared at temperatures between 142 K and 252 K and correlated to other material-characterising values. The tests were completed by stress analysis and by comparing the crack opening displacement. Due to the additional stress, Tsub(g)sub(y) was found to be 20 K higher than for the reference specimen. The fracture toughness decreases significantly in certain temperature ranges. The plastic stress concentration factor was comperatively higher and the remaining plastic crack opening decreases up to 25%. (orig.) [de

  11. Well test analysis in fractured media

    Energy Technology Data Exchange (ETDEWEB)

    Karasaki, K.

    1986-04-01

    In this study the behavior of fracture systems under well test conditions and methods for analyzing well test data from fractured media are investigated. Several analytical models are developed to be used for analyzing well test data from fractured media. Numerical tools that may be used to simulate fluid flow in fractured media are also presented. Three types of composite models for constant flux tests are investigated. Several slug test models with different geometric conditions that may be present in fractured media are also investigated. A finite element model that can simulate transient fluid flow in fracture networks is used to study the behavior of various two-dimensional fracture systems under well test conditions. A mesh generator that can be used to model mass and heat flow in a fractured-porous media is presented. This model develops an explicit solution in the porous matrix as well as in the discrete fractures. Because the model does not require the assumptions of the conventional double porosity approach, it may be used to simulate cases where double porosity models fail.

  12. Capabilities and limitations of fracture mechanics methods in the assessment of integrity of light water reactor components

    Energy Technology Data Exchange (ETDEWEB)

    Burdekin, F M

    1988-12-31

    This document deals with fracture mechanics methods used for the assessment of Light Water Reactor (LWR) components. The background to analysis methods using elastic plastic parameters is described. Several results obtained with these methods are presented as well as results of reliability analysis methods. (TEC). 27 refs.

  13. Impact of Injury Mechanisms on Patterns and Management of Facial Fractures.

    Science.gov (United States)

    Greathouse, S Travis; Adkinson, Joshua M; Garza, Ramon; Gilstrap, Jarom; Miller, Nathan F; Eid, Sherrine M; Murphy, Robert X

    2015-07-01

    Mechanisms causing facial fractures have evolved over time and may be predictive of the types of injuries sustained. The objective of this study is to examine the impact of mechanisms of injury on the type and management of facial fractures at our Level 1 Trauma Center. The authors performed an Institutional Review Board-approved review of our network's trauma registry from 2006 to 2010, documenting age, sex, mechanism, Injury Severity Score, Glasgow Coma Scale, facial fracture patterns (nasal, maxillary/malar, orbital, mandible), and reconstructions. Mechanism rates were compared using a Pearson χ2 test. The database identified 23,318 patients, including 1686 patients with facial fractures and a subset of 1505 patients sustaining 2094 fractures by motor vehicle collision (MVC), fall, or assault. Nasal fractures were the most common injuries sustained by all mechanisms. MVCs were most likely to cause nasal and malar/maxillary fractures (P management. Age and number of fractures sustained were associated with operative intervention. Although there is a statistically significant correlation between mechanism of injury and type of facial fracture sustained, none of the mechanisms evaluated herein are statistically associated with surgical intervention. Clinical Question/Level of Evidence: Therapeutic, III.

  14. Stress analysis of implant-bone fixation at different fracture angle

    Science.gov (United States)

    Izzawati, B.; Daud, R.; Afendi, M.; Majid, MS Abdul; Zain, N. A. M.; Bajuri, Y.

    2017-10-01

    Internal fixation is a mechanism purposed to maintain and protect the reduction of a fracture. Understanding of the fixation stability is necessary to determine parameters influence the mechanical stability and the risk of implant failure. A static structural analysis on a bone fracture fixation was developed to simulate and analyse the biomechanics of a diaphysis shaft fracture with a compression plate and conventional screws. This study aims to determine a critical area of the implant to be fractured based on different implant material and angle of fracture (i.e. 0°, 30° and 45°). Several factors were shown to influence stability to implant after surgical. The stainless steel, (S. S) and Titanium, (Ti) screws experienced the highest stress at 30° fracture angle. The fracture angle had a most significant effect on the conventional screw as compared to the compression plate. The stress was significantly higher in S.S material as compared to Ti material, with concentrated on the 4th screw for all range of fracture angle. It was also noted that the screws closest to the intense concentration stress areas on the compression plate experienced increasing amounts of stress. The highest was observed at the screw thread-head junction.

  15. Numerical simulation of the heat extraction in EGS with thermal-hydraulic-mechanical coupling method based on discrete fractures model

    International Nuclear Information System (INIS)

    Sun, Zhi-xue; Zhang, Xu; Xu, Yi; Yao, Jun; Wang, Hao-xuan; Lv, Shuhuan; Sun, Zhi-lei; Huang, Yong; Cai, Ming-yu; Huang, Xiaoxue

    2017-01-01

    The Enhanced Geothermal System (EGS) creates an artificial geothermal reservoir by hydraulic fracturing which allows heat transmission through the fractures by the circulating fluids as they extract heat from Hot Dry Rock (HDR). The technique involves complex thermal–hydraulic–mechanical (THM) coupling process. A numerical approach is presented in this paper to simulate and analyze the heat extraction process in EGS. The reservoir is regarded as fractured porous media consisting of rock matrix blocks and discrete fracture networks. Based on thermal non-equilibrium theory, the mathematical model of THM coupling process in fractured rock mass is used. The proposed model is validated by comparing it with several analytical solutions. An EGS case from Cooper Basin, Australia is simulated with 2D stochastically generated fracture model to study the characteristics of fluid flow, heat transfer and mechanical response in geothermal reservoir. The main parameters controlling the outlet temperature of EGS are also studied by sensitivity analysis. The results shows the significance of taking into account the THM coupling effects when investigating the efficiency and performance of EGS. - Highlights: • EGS reservoir comprising discrete fracture networks and matrix rock is modeled. • A THM coupling model is proposed for simulating the heat extraction in EGS. • The numerical model is validated by comparing with several analytical solutions. • A case study is presented for understanding the main characteristics of EGS. • The THM coupling effects are shown to be significant factors to EGS's running performance.

  16. Microscale fracture mechanisms of a Cr3C2-NiCr HVOF coating

    International Nuclear Information System (INIS)

    Robertson, Andrew L.; White, Ken W.

    2017-01-01

    Thermal spray coatings, often composed of heterogeneous, multiphase microstructures, may, consequently, exhibit complex fracture behavior. For such coating structures, conventional mechanical evaluation methods fail to isolate the contribution of microstructural features to the overall fracture behavior. For this reason, this study employed focused ion beam machined (FIB) microcantilever beams and FIB sectioning methods to study the fracture mechanisms important at the scale of the heterogeneous Cr 3 C 2 -NiCr thermal spray coating. We found three fracture modes, namely, intergranular matrix fracture, matrix/carbide interfacial fracture, and carbide cleavage. By comparison, microindentation-induced cracks, the frequency of crack deflection around carbides is significantly more prevalent at this much larger crack dimension. This mechanistic variation provides some insight into the specific role and limitations of the microcantilever beam technique for fracture characterization of composite microstructures.

  17. The effect of multiaxial stress state on creep behavior and fracture mechanism of P92 steel

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Yuan; Xu, Hong, E-mail: xuhong@ncepu.edu.cn; Ni, Yongzhong; Lan, Xiang; Li, Hongyuan

    2015-06-11

    The creep experiments on plain and double U-typed notched specimens were conducted on P92 steel at 650 °C. The notch strengthening effect was found in the notched specimens. Fracture appearance observed by scanning electron microscopy revealed that dimpled fracture for relatively blunt notched specimen, and dimpled fracture doubled with intergranular brittle fracture for relatively sharp notched specimen, which meant that fracture mechanism of P92 steel altered due to the presence of the notch. Meanwhile, based on Norton–Bailey and Kachanov–Robotnov constitutive models, a modified model was proposed. Finite element simulations were carried out to investigate the effect of multiaxial stress state on the creep behavior, fracture mechanism and damage evolvement of P92 steel. The simulation results agreed well with the fracture behaviors observed experimentally.

  18. Effective Hydro-Mechanical Properties of Fluid-Saturated Fracture Networks

    Science.gov (United States)

    Pollmann, N.; Vinci, C.; Renner, J.; Steeb, H.

    2015-12-01

    Consideration of hydro-mechanical processes is essential for the characterization of liquid-resources as well as for many engineering applications. Furthermore, the modeling of seismic waves in fractured porous media finds application not only in geophysical exploration but also reservoir management. Fractures exhibit high-aspect-ratio geometries, i.e. they constitute thin and long hydraulic conduits. Motivated by this peculiar geometry, the investigation of the hydro-mechanically coupled processes is performed by means of a hybrid-dimensional modeling approach. The effective material behavior of domains including complex fracture patterns in a porous rock is assessed by investigating the fluid pressure and the solid displacement of the skeleton saturated by compressible fluids. Classical balance equations are combined with a Poiseuille-type flow in the dimensionally reduced fracture. In the porous surrounding rock, the classical Biot-theory is applied. For simple geometries, our findings show that two main fluid-flow processes occur, leak-off from fractures to the surrounding rock and fracture flow within and between the connected fractures. The separation of critical frequencies of the two flow processes is not straightforward, in particular for systems containing a large number of fractures. Our aim is to model three dimensional hydro-mechanically coupled processes within complex fracture patterns and in particular determine the frequency-dependent attenuation characteristics. Furthermore, the effect of asperities of the fracture surfaces on the fracture stiffness and on the hydraulic conductivity will be added to the approach.

  19. Rheological Characteristics of Cement Grout and its Effect on Mechanical Properties of a Rock Fracture

    Science.gov (United States)

    Liu, Quansheng; Lei, Guangfeng; Peng, Xingxin; Lu, Chaobo; Wei, Lai

    2018-02-01

    Grouting reinforcement, which has an obvious strengthening effect on fractured rock mass, has been widely used in various fields in geotechnical engineering. The rheological properties of grout will greatly affect its diffusion radius in rock fractures, and the water-cement ratio is an important factor in determining the grouting flow patterns. The relationship between shear stress and shear rate which could reflect the grout rheological properties, the effects of water-cement ratio, and temperature on the rheological properties of grouting was studied in the laboratory. Besides, a new method for producing fractured rock specimens was proposed and solved the problem of producing natural fractured rock specimens. To investigate the influences of grouting on mechanical properties of a rock fracture, the fractured rock specimens made using the new method were reinforced by grouting on the independent designed grouting platform, and then normal and tangential mechanical tests were carried out on fractured rock specimens. The results showed that the mechanical properties of fractured rock mass are significantly improved by grouting, the peak shear strength and residual strength of rock fractures are greatly improved, and the resistance to deformation is enhanced after grouting. Normal forces affect the tangential behavior of the rock fracture, and the tangential stress strength increases with normal forces. The strength and stability of fractured rock mass are increased by grouting reinforcement.

  20. Fracture analysis of tube boiler for physical explosion accident.

    Science.gov (United States)

    Kim, Eui Soo

    2017-09-01

    Material and failure analysis techniques are key tools for determining causation in case of explosive and bursting accident result from material and process defect of product in the field of forensic science. The boiler rupture generated by defect of the welding division, corrosion, overheating and degradation of the material have devastating power. If weak division of boiler burner is fractured by internal pressure, saturated vapor and water is vaporized suddenly. At that time, volume of the saturated vapor and water increases up to thousands of volume. This failure of boiler burner can lead to a fatal disaster. In order to prevent an explosion and of the boiler, it is critical to introduce a systematic investigation and prevention measures in advance. In this research, the cause of boiler failure is investigated through forensic engineering method. Specifically, the failure mechanism will be identified by fractography using scanning electron microscopes (SEM) and Optical Microscopes (OM) and mechanical characterizations. This paper presents a failure analysis of household welding joints for the water tank of a household boiler burner. Visual inspection was performed to find out the characteristics of the fracture of the as-received material. Also, the micro-structural changes such as grain growth and carbide coarsening were examined by optical microscope. Detailed studies of fracture surfaces were made to find out the crack propagation on the weld joint of a boiler burner. It was concluded that the rupture may be caused by overheating induced by insufficient water on the boiler, and it could be accelerated by the metal temperature increase. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Fracture propagation in sandstone and slate – Laboratory experiments, acoustic emissions and fracture mechanics

    Directory of Open Access Journals (Sweden)

    Ferdinand Stoeckhert

    2015-06-01

    Full Text Available Fracturing of highly anisotropic rocks is a problem often encountered in the stimulation of unconventional hydrocarbon or geothermal reservoirs by hydraulic fracturing. Fracture propagation in isotropic material is well understood but strictly isotropic rocks are rarely found in nature. This study aims at the examination of fracture initiation and propagation processes in a highly anisotropic rock, specifically slate. We performed a series of tensile fracturing laboratory experiments under uniaxial as well as triaxial loading. Cubic specimens with edge lengths of 150 mm and a central borehole with a diameter of 13 mm were prepared from Fredeburg slate. An experiment using the rather isotropic Bebertal sandstone as a rather isotropic rock was also performed for comparison. Tensile fractures were generated using the sleeve fracturing technique, in which a polymer tube placed inside the borehole is pressurized to generate tensile fractures emanating from the borehole. In the uniaxial test series, the loading was varied in order to observe the transition from strength-dominated fracture propagation at low loading magnitudes to stress-dominated fracture propagation at high loading magnitudes.

  2. Characterization of fracture networks for fluid flow analysis

    International Nuclear Information System (INIS)

    Long, J.C.S.; Billaux, D.; Hestir, K.; Majer, E.L.; Peterson, J.; Karasaki, K.; Nihei, K.; Gentier, S.; Cox, L.

    1989-06-01

    The analysis of fluid flow through fractured rocks is difficult because the only way to assign hydraulic parameters to fractures is to perform hydraulic tests. However, the interpretation of such tests, or ''inversion'' of the data, requires at least that we know the geometric pattern formed by the fractures. Combining a statistical approach with geophysical data may be extremely helpful in defining the fracture geometry. Cross-hole geophysics, either seismic or radar, can provide tomograms which are pixel maps of the velocity or attenuation anomalies in the rock. These anomalies are often due to fracture zones. Therefore, tomograms can be used to identify fracture zones and provide information about the structure within the fracture zones. This structural information can be used as the basis for simulating the degree of fracturing within the zones. Well tests can then be used to further refine the model. Because the fracture network is only partially connected, the resulting geometry of the flow paths may have fractal properties. We are studying the behavior of well tests under such geometry. Through understanding of this behavior, it may be possible to use inverse techniques to refine the a priori assignment of fractures and their conductances such that we obtain the best fit to a series of well test results simultaneously. The methodology described here is under development and currently being applied to several field sites. 4 refs., 14 figs

  3. Mechanisms Underlying Stress Fracture and the Influence of Sex and Race/Ethnicity

    Science.gov (United States)

    2017-10-01

    AWARD NUMBER: W81XWH-16-1-0652 TITLE: Mechanisms Underlying Stress Fracture and the Influence of Sex and Race/Ethnicity PRINCIPAL INVESTIGATOR...5a. CONTRACT NUMBER W81XWH-16-1-0652 Mechanisms Underlying Stress Fracture and the Influence of Sex and Race/Ethnicity 5b. GRANT NUMBER W81XWH...to stress fracture risk. In particular, in Study 1, we will perform advanced skeletal imaging along with gait-assessments in subjects with history of

  4. Multiscale Stochastic Fracture Mechanics of Composites Informed by In-situ XCT Tests

    Science.gov (United States)

    2016-02-02

    interfacial fracture ) in CFRP was recently found in the fuselages of Dreamliner 787, and two types of cracks were found in the rib feet brackets...AFRL-AFOSR-UK-TR-2016-0003 Multiscale Stochastic Fracture Mechanics of Composites Informed by In-situ XCT Tests Zhenjun Yang UNIVERSITY OF MANCHESTER...Multiscale Stochastic Fracture Mechanics of Composites Informed by In-situ XCT Tests 5a. CONTRACT NUMBER EOARD 12-2100 5b. GRANT NUMBER F8655-12-1

  5. From fracture mechanics to damage mechanics: how to model structural deterioration

    International Nuclear Information System (INIS)

    Nicolet, S.; Lorentz, E.; Barbier, G.

    1998-01-01

    Modelling of structural deteriorations of thermo-mechanical origin is highly enhanced when using damage mechanics. Indeed, the latter offers both a fine description of the material behaviour and an ability to deal with any loading conditions, moving away the current limits of fracture mechanics. But new difficulties can arise, depending on the examined problem: if forecasts of rack initiation are well mastered, the study of crack propagation remains more complex and needs sophisticated modelizations, which are nevertheless on the point of being well understood too. (authors)

  6. Decoupling damage mechanisms in acid-fractured gas/condensate reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Bachman, R.C.; Walters, D.A. [Taurus Reservoir Solutions Ltd., Calgary, AB (Canada); Settari, A. [Calgary Univ., AB (Canada); Rahim, Z.; Ahmed, M.S. [Saudi Aramco, Dhahran (Saudi Arabia)

    2006-07-01

    The Khuff is a gas condensate field located 11,500 feet beneath the producing Ghawar oil field in Saudi Arabia. Wells are mainly acid fracture stimulated following drilling with excellent fracture conductivity and length properties. The wells experience a quick production loss however, after tie-in which eventually stabilizes after two to five months. In order to identify the source of productivity loss, such as near well liquid dropout, fracture conductivity loss, reservoir permeability loss due to increased effective stress, a study of a well in the Khuff field was conducted. The study reviewed basic geomechanical and reservoir properties and identified the mechanisms of production loss. The paper presented the methodology, data and preliminary analysis, relative permeability and results of the history matching. It was concluded that traditional production type curves in cases with changing skin may indicate that transient flow is occurring when boundary effects are felt. In addition, stress dependent fracture conductivity and reservoir permeability can be modeled with simpler pressure dependent functions for relatively low overall loss in reservoir pressure. 30 refs., 25 figs., 1 appendix.

  7. Analysis Strategy for Fracture Assessment of Defects in Ductile Materials

    Energy Technology Data Exchange (ETDEWEB)

    Dillstroem, Peter; Andersson, Magnus; Sattari-Far, Iradj; Weilin Zang (Inspecta Technology AB, Stockholm (Sweden))

    2009-06-15

    The main purpose of this work is to investigate the significance of the residual stresses for defects (cracks) in ductile materials with nuclear applications, when the applied primary (mechanical) loads are high. The treatment of weld-induced stresses as expressed in the SACC/ProSACC handbook and other fracture assessment procedures such as the ASME XI code and the R6-method is believed to be conservative for ductile materials. This is because of the general approach not to account for the improved fracture resistance caused by ductile tearing. Furthermore, there is experimental evidence that the contribution of residual stresses to fracture diminishes as the degree of yielding increases to a high level. However, neglecting weld-induced stresses in general, though, is doubtful for loads that are mostly secondary (e.g. thermal shocks) and for materials which are not ductile enough to be limit load controlled. Both thin-walled and thick-walled pipes containing surface cracks are studied here. This is done by calculating the relative contribution from the weld residual stresses to CTOD and the J-integral. Both circumferential and axial cracks are analysed. Three different crack geometries are studied here by using the finite element method (FEM). (i) 2D axisymmetric modelling of a V-joint weld in a thin-walled pipe. (ii) 2D axisymmetric modelling of a V-joint weld in a thick-walled pipe. (iii) 3D modelling of a X-joint weld in a thick-walled pipe. t. Each crack configuration is analysed for two load cases; (1) Only primary (mechanical) loading is applied to the model, (2) Both secondary stresses and primary loading are applied to the model. Also presented in this report are some published experimental investigations conducted on cracked components of ductile materials subjected to both primary and secondary stresses. Based on the outcome of this study, an analysis strategy for fracture assessment of defects in ductile materials of nuclear components is proposed. A new

  8. Analysis Strategy for Fracture Assessment of Defects in Ductile Materials

    International Nuclear Information System (INIS)

    Dillstroem, Peter; Andersson, Magnus; Sattari-Far, Iradj; Weilin Zang

    2009-06-01

    The main purpose of this work is to investigate the significance of the residual stresses for defects (cracks) in ductile materials with nuclear applications, when the applied primary (mechanical) loads are high. The treatment of weld-induced stresses as expressed in the SACC/ProSACC handbook and other fracture assessment procedures such as the ASME XI code and the R6-method is believed to be conservative for ductile materials. This is because of the general approach not to account for the improved fracture resistance caused by ductile tearing. Furthermore, there is experimental evidence that the contribution of residual stresses to fracture diminishes as the degree of yielding increases to a high level. However, neglecting weld-induced stresses in general, though, is doubtful for loads that are mostly secondary (e.g. thermal shocks) and for materials which are not ductile enough to be limit load controlled. Both thin-walled and thick-walled pipes containing surface cracks are studied here. This is done by calculating the relative contribution from the weld residual stresses to CTOD and the J-integral. Both circumferential and axial cracks are analysed. Three different crack geometries are studied here by using the finite element method (FEM). (i) 2D axisymmetric modelling of a V-joint weld in a thin-walled pipe. (ii) 2D axisymmetric modelling of a V-joint weld in a thick-walled pipe. (iii) 3D modelling of a X-joint weld in a thick-walled pipe. t. Each crack configuration is analysed for two load cases; (1) Only primary (mechanical) loading is applied to the model, (2) Both secondary stresses and primary loading are applied to the model. Also presented in this report are some published experimental investigations conducted on cracked components of ductile materials subjected to both primary and secondary stresses. Based on the outcome of this study, an analysis strategy for fracture assessment of defects in ductile materials of nuclear components is proposed. A new

  9. Implications of recent developments in the plastic fracture mechanics field to the PCI stress corrosion problem

    International Nuclear Information System (INIS)

    Smith, E.

    1980-01-01

    Fractographic observations on irradiated Zircaloy cladding stress corrosion fracture surfaces are considered against the background of recent developments in the plastic fracture mechanics field. Dimples have been observed on the fracture surfaces of failed cladding, even though the cracks in metallographic sections are tight, i.e., crack propagation is associated with a low crack tip opening angle. This result is interpreted as providing evidence for an environmentally assisted ductile mode of fracture. The presence of this fracture mode forms the basis of an argument, which adds further support for the view that power ramp stress corrosion cladding failures are caused by stress concentrations that produce stress gradients in the cladding. (orig.)

  10. Deformation Mechanisms and Fracture of Ni-Based Metallic Glasses

    Directory of Open Access Journals (Sweden)

    Lesz S.

    2016-06-01

    Full Text Available The cracking of materials and fracture surface is of great practical and academic importance. Over the last few years the development of the fractography of crystalline alloys resulted in a useful tool for the prediction or failure analysis. Many attempts have been made to observe cracks using optical microscopy, X-ray topography and transmission electron microscopy (TEM. Of these techniques, the resolution of optical microscopy and X-ray topography is too poor. By contrast, the resolution of TEM is high enough for detailed information to be obtained. However, in order to apply TEM observations, a thin foil specimen must be prepared, and it is usually extremely difficult to prepare such a specimen from a pre-selected region containing a crack.

  11. Fracture-mechanical results of non-destructive testing - function, goals, methods

    International Nuclear Information System (INIS)

    Herter, K.H.; Kockelmann, H.; Schuler, X.; Waidele, H.

    2004-01-01

    Non-destructive testing provides data for fracture-mechanical analyses, e.g. defect size and orientation. On the other hand, fracture-mechanical analyses may help to define criteria for non-destructive testing, e.g. sensitivity, inspection intervals and inspection sites. The criteria applied differ as a function of the safety relevance of a component. (orig.) [de

  12. Proceedings of the Joint IAEA/CSNI Specialists' Meeting on Fracture Mechanics Verification by Large-Scale Testing

    International Nuclear Information System (INIS)

    1993-10-01

    This report provides the proceedings of a Specialists' Meeting on Fracture Mechanics Verification by Large-Scale Testing that was held in Oak Ridge, Tennessee, on October 23-25, 1992. The meeting was jointly sponsored by the International Atomic Energy Agency (IAEA) and the Nuclear Energy Agency (NEA) of the Organization for Economic Cooperation and Development. In particular, the International Working Group (IWG) on Life Management of Nuclear Power Plants (LMNPP) was the IAEA sponsor, and the Principal Working Group 3 (PWG-3) (Primary System Component Integrity) of the Committee for the Safety of Nuclear Installations (CSNI) was the NEA's sponsor. This meeting was preceded by two prior international activities that were designed to examine the state-of-the-art in fracture analysis capabilities and emphasized applications to the safety evaluation of nuclear power facilities. The first of those two activities was an IAEA Specialists' Meeting on Fracture Mechanics Verification by Large-Scale Testing that was held at the Staatliche Materialprufungsanstalt (MPA) in Stuttgart, Germany, on May 25-27, 1988; the proceedings of that meeting were published 1991.1 The second activity was the CSNI/PWG-3's Fracture Assessment Group's Project FALSIRE (Fracture Analyses of Large-Scale International Reference Experiments). The proceedings of the FALSIRE workshop that was held in Boston, Massachusetts, U.S.A., on May 8-10, 1990, was recently published by the Oak Ridge National Laboratory (ORNL). Those previous activities identified capabilities and shortcomings of various fracture analysis methods based on analyses of six available large-scale experiments. Different modes of fracture behavior, which ranged from brittle to ductile, were considered. In addition, geometry, size, constraint and multiaxial effects were considered. While generally good predictive capabilities were demonstrated for brittle fracture, issues were identified relative to predicting fracture behavior at higher

  13. Two-criteria method for fracture-mechanical analysis of pipelines - practical application and influencing parameters; Zwei-Kriterien-Verfahren zur bruchmechanischen Befundbewertung in Rohrleitungen - praktische Anwendung und Einflussgroessen

    Energy Technology Data Exchange (ETDEWEB)

    Beukelmann, D. [TUeV Sued Industrie Service GmbH (Germany); Doerk, O.; Wernicke, R. [TUeV Nord SysTec GmbH und Co. KG (Germany)

    2006-07-01

    The findings obtained in recurrent inspections as a rule are evaluated by fracture-mechanical analyses. On the basis of the results, it is decided whether a component must be repaired or if operation can continue as it is for the time being. The two-criteria method is applied as a rule because of its universal applicability. Limited ductile crack growth can be taken into account if crack resistance curves are available that can be transferred to the component in question. In the investigations presented here, the influence of the relevant initial variables, e.g. strength coefficents, fracture-mechanical material coefficients, primary and secondary stresses and the intrinsic state of stress is illustrated by exemplary calculations. Further, the safety concepts underlying the assessment are gone into. (orig.)

  14. Undercut tolerances in industry from a fracture mechanic perspective

    Directory of Open Access Journals (Sweden)

    Steimbreger Ceferino

    2018-01-01

    Full Text Available Fatigue is an important damage mechanism that particularly affects welded components, since they are likely to present residual stresses, inhomogeneities and stress raisers. Assessment of cyclic load effects on welds has concerned both industries and scientist for decades; unexpected failure must be prevented and at the same time, structures must withstand design loads with minimum requirements of material. All these facts together with economic issues have lead to the creation of normative that rule designing and construction of welded components. Particularly, toe undercuts are generally found in large structures, and large scatter and disagreement exists towards their significance and effects. Documents usually limit only their depth without considering radius, width or length, and there is currently no explanation to that fact. Understanding the damaging process will also help to set less conservative tolerances, with consequent cost reduction due to less demanding inspection. The present paper deals with a fracture mechanic approach that uses the Resistance Curve concept to predict fatigue limit of welded components with undercuts. Results revealed that depth is the most influencing variable, and it can be used as the limiting parameter in design regulations. Moreover, good correlation was obtained with FAT values normally assigned to this kind of defect.

  15. Hydrogen embrittlement of titanium tested with fracture mechanics specimens

    International Nuclear Information System (INIS)

    Aho-Mantila, I.; Rahko, P.

    1990-11-01

    Titanium is one of the possible canister materials for spent nuclear fuel. The aim of this study is to determine whether the hydrogen embrittlement of titanium could be a possible deterioration mechanism of titanium canisters. This experimental study was preceded by a literature review and an experimental study on crack nucleation. Tests in this study were carried out with hydrogen charged fracture mechanics specimens. The studied hydrogen contents were as received, 100 ppm, 200 ppm, 500 ppm and 700 ppm and the types of the studied titanium were ASTM Grades 2 and 12. Test methods were slow tensile test (0.027 mm/h) and fatigue test (stress ratio 0.7 or 0.8 and frequency 5 Hz). According to the literature titanium may be embrittled by hydrogen at slow strain rates and cracking may occur under sustained load. In this study no evidence of hydrogen embrittlement was noticed in slow strain rate tension with bulk hydrogen contents up to 700 ppm. The fatigue tests of titanium Grades 2 and 12 containing 700 ppm hydrogen showed even slower crack growth compared to the as received condition. Very high hydrogen contents well in eccess of 700 ppm on the surface of titanium can, however, facilitate surface crack nucleation and crack growth, as shown in the previous study

  16. Probabilistic Fatigue Life Prediction of Bridge Cables Based on Multiscaling and Mesoscopic Fracture Mechanics

    Directory of Open Access Journals (Sweden)

    Zhongxiang Liu

    2016-04-01

    Full Text Available Fatigue fracture of bridge stay-cables is usually a multiscale process as the crack grows from micro-scale to macro-scale. Such a process, however, is highly uncertain. In order to make a rational prediction of the residual life of bridge cables, a probabilistic fatigue approach is proposed, based on a comprehensive vehicle load model, finite element analysis and multiscaling and mesoscopic fracture mechanics. Uncertainties in both material properties and external loads are considered. The proposed method is demonstrated through the fatigue life prediction of cables of the Runyang Cable-Stayed Bridge in China, and it is found that cables along the bridge spans may have significantly different fatigue lives, and due to the variability, some of them may have shorter lives than those as expected from the design.

  17. Hydro-mechanically coupled finite-element analysis of the stability of a fractured-rock slope using the equivalent continuum approach: a case study of planned reservoir banks in Blaubeuren, Germany

    Science.gov (United States)

    Song, Jie; Dong, Mei; Koltuk, Serdar; Hu, Hui; Zhang, Luqing; Azzam, Rafig

    2017-12-01

    Construction works associated with the building of reservoirs in mountain areas can damage the stability of adjacent valley slopes. Seepage processes caused by the filling and drawdown operations of reservoirs also affect the stability of the reservoir banks over time. The presented study investigates the stability of a fractured-rock slope subjected to seepage forces in the lower basin of a planned pumped-storage hydropower (PSH) plant in Blaubeuren, Germany. The investigation uses a hydro-mechanically coupled finite-element analyses. For this purpose, an equivalent continuum model is developed by using a representative elementary volume (REV) approach. To determine the minimum required REV size, a large number of discrete fracture networks are generated using Monte Carlo simulations. These analyses give a REV size of 28 × 28 m, which is sufficient to represent the equivalent hydraulic and mechanical properties of the investigated fractured-rock mass. The hydro-mechanically coupled analyses performed using this REV size show that the reservoir operations in the examined PSH plant have negligible effect on the adjacent valley slope.

  18. Hydro-mechanically coupled finite-element analysis of the stability of a fractured-rock slope using the equivalent continuum approach: a case study of planned reservoir banks in Blaubeuren, Germany

    Science.gov (United States)

    Song, Jie; Dong, Mei; Koltuk, Serdar; Hu, Hui; Zhang, Luqing; Azzam, Rafig

    2018-05-01

    Construction works associated with the building of reservoirs in mountain areas can damage the stability of adjacent valley slopes. Seepage processes caused by the filling and drawdown operations of reservoirs also affect the stability of the reservoir banks over time. The presented study investigates the stability of a fractured-rock slope subjected to seepage forces in the lower basin of a planned pumped-storage hydropower (PSH) plant in Blaubeuren, Germany. The investigation uses a hydro-mechanically coupled finite-element analyses. For this purpose, an equivalent continuum model is developed by using a representative elementary volume (REV) approach. To determine the minimum required REV size, a large number of discrete fracture networks are generated using Monte Carlo simulations. These analyses give a REV size of 28 × 28 m, which is sufficient to represent the equivalent hydraulic and mechanical properties of the investigated fractured-rock mass. The hydro-mechanically coupled analyses performed using this REV size show that the reservoir operations in the examined PSH plant have negligible effect on the adjacent valley slope.

  19. Analysis of PITFL injuries in rotationally unstable ankle fractures.

    Science.gov (United States)

    Warner, Stephen J; Garner, Matthew R; Schottel, Patrick C; Hinds, Richard M; Loftus, Michael L; Lorich, Dean G

    2015-04-01

    Reduction and stabilization of the syndesmosis in unstable ankle fractures is important for ankle mortise congruity and restoration of normal tibiotalar contact forces. Of the syndesmotic ligaments, the posterior inferior tibiofibular ligament (PITFL) provides the most strength for maintaining syndesmotic stability, and previous work has demonstrated the significance of restoring PITFL function when it remains attached to a posterior malleolus fracture fragment. However, little is known regarding the nature of a PITFL injury in the absence of a posterior malleolus fracture. The goal of this study was to describe the PITFL injury pattern based on magnetic resonance imaging (MRI) and intraoperative observation. A prospective database of all operatively treated ankle fractures by a single surgeon was used to identify all supination-external rotation (SER) types III and IV ankle fracture patients with complete preoperative orthogonal ankle radiographs and MRI. All patients with a posterior malleolus fracture were excluded. Using a combination of preoperative imaging and intraoperative findings, we analyzed the nature of injuries to the PITFL. In total, 185 SER III and IV operatively treated ankle fractures with complete imaging were initially identified. Analysis of the preoperative imaging and operative reports revealed 34% (63/185) had a posterior malleolus fracture and were excluded. From the remaining 122 ankle fractures, the PITFL was delaminated from the posterior malleolus in 97% (119/122) of cases. A smaller proportion (3%; 3/122) had an intrasubstance PITFL rupture. Accurate and stable syndesmotic reduction is a significant component of restoring the ankle mortise after unstable ankle fractures. In our large cohort of rotationally unstable ankle fractures without posterior malleolus fractures, we found that most PITFL injuries occur as a delamination off the posterior malleolus. This predictable PITFL injury pattern may be used to guide new methods for

  20. An investigation of the mechanical and hydrologic behavior of tuff fractures under saturated conditions

    International Nuclear Information System (INIS)

    Voss, C.F.; Shotwell, L.R.

    1990-04-01

    The mechanical and hydrologic behavior of natural fractures in a partially welded tuff rock were investigated. Tuff cores, each containing part of the same natural fracture oriented subparallel to the core axis, were subjected a range of stress and hydraulic gradients while simultaneously monitoring changes in the fracture aperture and volumetric flow rate. The fractures were tested in three configurations: intact, mated, and offset. Fracture deformation was nonlinear over the stress range tested with permanent deformation and hysteresis occurring with each loading cycle. The offset samples had larger permanent deformation and significantly reduced normal stiffness at lower stress levels. The cubic flow law appears to be valid for the relatively undisturbed tuff fractures at the scale tested. The cubic law did not explain the observed hydraulic behavior of the offset fractures. 6 refs., 10 figs., 2 tabs

  1. Elastic-plastic FEM-analysis of a nozzle corner crack and discussion of the results by some fracture mechanics concepts

    International Nuclear Information System (INIS)

    Aurich, D.; Brocks, W.; Noack, D.; Veith, H.

    1981-01-01

    From a three-dimensional elastic-plastic stress-distortion analysis according to the finite element method (FEM) for a straight inner edge crack at room temperature in a nozzle of the intermediate vessel ZB 2 made of 22 NiMoCr 37 steel, the results obtained for stresses and strains in the ligament before the crack front, the crack opening profile, and the propagation of the plastic zone as a function of internal pressure until through-plastifying of the ligament are shown and explained. (orig.) [de

  2. Stochastic and fractal analysis of fracture trajectories

    Science.gov (United States)

    Bessendorf, Michael H.

    1987-01-01

    Analyses of fracture trajectories are used to investigate structures that fall between 'micro' and 'macro' scales. It was shown that fracture trajectories belong to the class of nonstationary processes. It was also found that correlation distance, which may be related to a characteristic size of a fracture process, increases with crack length. An assemblage of crack trajectory processes may be considered as a diffusive process. Chudnovsky (1981-1985) introduced a 'crack diffusion coefficient' d which reflects the ability of the material to deviate the crack trajectory from the most energetically efficient path and thus links the material toughness to its structure. For the set of fracture trajectories in AISI 304 steel, d was found to be equal to 1.04 microns. The fractal dimension D for the same set of trajectories was found to be 1.133.

  3. Application of probabilistic fracture mechanics to reactor pressure vessel safety assessment

    International Nuclear Information System (INIS)

    Venturini, V.; Pitner, P.

    1995-06-01

    Among all the components of a PWR (Pressurized Water Reactor) nuclear power plant, the reactor vessel is of major importance for safety. The integrity of this structure must be guaranteed in all circumstances, even in the case of the most severe accidents, and its mechanical state can be decisive for the lifetime of the plant. The brittle rupture would be the most important of all potential hazards if the irradiation effects were not consistent with predictions. The interest of having a reliable and precise method of evaluating the available safety margins and the integrity of this component led Electricite de France (EDF) to carry out a probabilistic fracture mechanics analysis. The probabilistic model developed by integration of the uncertainties in the usual fracture mechanics equations is presented. A special focus is made on the problem of coupling thermo-mechanical finite element calculations and reliability analysis. The use of a finite element code can be associated with prohibitive computation times when it is invoked numerous times during simulations sequences or complex iterative procedures. The response surface method is used. It provides an approximation of the response from a reduced number of original data. The global approach is illustrated on an example corresponding to a specific accidental transient. A validation of the obtained results is also carried out through the comparison with an equivalent model without coupling. (author)

  4. The effect of advanced ultrasonic forging on fatigue fracture mechanisms of welded Ti-6A1-4V alloy

    Science.gov (United States)

    Smirnova, A.; Pochivalov, Yu.; Panin, V.; Panin, S.; Eremin, A.; Gorbunov, A.

    2017-12-01

    The current study is devoted to application of advanced postwelding ultrasonic forging to joints formed by laser welding of Ti-6A1-4V alloy in order to enhance their mechanical properties and fatigue durability. Low cycle fatigue tests were performed via digital image correlation technique used to obtain strain fields and in situ characterization of deformation, crack growth and fracture. Fracture surfaces were studied by SEM analysis accompanied with calculation of fracture patterns percentage. The fatigue tests demonstrate the high increase in the number of cycles until fracture (from 17 000 to 32 000 cycles) which could be explained by high ductility of welded material after treatment. This leads to lower fatigue crack growth rate due to higher energy dissipation. The obtained effect is attributable only for small cracks on micro-/mesoscales and fails to play a significant role for macro cracks.

  5. Isolated posterior malleolus fracture: A rare injury mechanism ...

    African Journals Online (AJOL)

    Sprain of the ankle is undoubtedly a common injury during athletic activity, and the sprain can be also associated with fracture of the ankle. Isolated posterior malleolus fracture is a very rare condition, which is usually missed. Here, we are presenting a 37 years old female patient, who suffered injury secondary pressing on ...

  6. Mechanisms of Plastic and Fracture Instabilities for Alloy Development of Fusion Materials. Final Project Report for period July 15, 1998 - July 14, 2003

    Energy Technology Data Exchange (ETDEWEB)

    Ghoniem, N. M.

    2003-07-14

    The main objective of this research was to develop new computational tools for the simulation and analysis of plasticity and fracture mechanisms of fusion materials, and to assist in planning and assessment of corresponding radiation experiments.

  7. Mechanisms of Plastic and Fracture Instabilities for Alloy Development of Fusion Materials. Final Project Report for period July 15, 1998 - July 14, 2003

    International Nuclear Information System (INIS)

    Ghoniem, N.M.

    2003-01-01

    The main objective of this research was to develop new computational tools for the simulation and analysis of plasticity and fracture mechanisms of fusion materials, and to assist in planning and assessment of corresponding radiation experiments

  8. Stresses, fatigue and fracture analysis in the tube sheets

    International Nuclear Information System (INIS)

    Billon, F.

    1986-05-01

    The purpose of the present work is to study the behaviour of the nuclear PWR steam generator tube sheet. But the methods developed in this field can easily be generalized in order to study tube sheets from any other type of heat exchangers. The aim of the stress analysis of these sheets is to verify their correct design, to quantify the risk of fatigue damage in the areas submitted to a high stress concentration and through the fracture mechanic, to make sure there is no risk of fast fracture resulting from initiated or pre-existing defects. This analysis necessarily relates to the calculation of stresses in all parts of the multidrilled area, mainly around the holes where they are concentrated. However the tube sheets are so complexe structures that their direct modelization cannot be envisaged within the context of the finite element method. We then must refer to the concept of equivalent medium in order to calculate the nominal stresses. Then using the stresses multiple fonctions appropriate to the net geometry, we can calculate the actual stresses concentrated around the holes. The method depends on the behaviour of the elementary volume which represents the behaviour of the multidrilled medium. This approach must allow to correctly take account of the ''thermal skin effect'', which is a phenomenon particular to the tube sheets with thermal loads. It must as well be generalized in order to analyse the irregular ligaments which affect the periodical stresses distribution and locally overconcentrate them [fr

  9. Investigation of Mechanical Properties and Fracture Simulation of Solution-Treated AA 5754

    Science.gov (United States)

    Kumar, Pankaj; Singh, Akhilendra

    2017-10-01

    In this work, mechanical properties and fracture toughness of as-received and solution-treated aluminum alloy 5754 (AA 5754) are experimentally evaluated. Solution heat treatment of the alloy is performed at 530 °C for 2 h, and then, quenching is done in water. Yield strength, ultimate tensile strength, impact toughness, hardness, fatigue life, brittle fracture toughness (K_{Ic} ) and ductile fracture toughness (J_{Ic} ) are evaluated for as-received and solution-treated alloy. Extended finite element method has been used for the simulation of tensile and fracture behavior of material. Heaviside function and asymptotic crack tip enrichment functions are used for modelling of the crack in the geometry. Ramberg-Osgood material model coupled with fracture energy is used to simulate the crack propagation. Fracture surfaces obtained from various mechanical tests are characterized by scanning electron microscopy.

  10. Sandia National Laboratories cask drop test programme: a demonstration of fracture mechanics principles for the prevention of brittle fracture

    International Nuclear Information System (INIS)

    McConnell, P.; Sorenson, K.B.

    1995-01-01

    Sandia National Laboratories recently completed a cask drop test programme. The aims of the programme were (1) to demonstrate the applicability of a fracture mechanics-based methodology for ensuring cask integrity, and (2) to assess the viability of using a ferritic materials for cask containment. The programme consisted of four phases: (i) materials characterisation; (ii) non-destructive examination of the cask; (iii) finite element analyses of the drop events; and (iv) a series of drop tests of a ductile iron cask. The first three phases of the programme provided information for fracture mechanics analyses and predictions for the drop test phase. The drop tests were nominally based upon the IAEA 9 m drop height hypothetical accident scenario although one drop test was from 18 m. All tests were performed in the side drop orientation at a temperature of -29 o C. A circumferential, mid-axis flaw was introduced into the cask body for each drop test. Flaw depth ranged from 19 to 76 mm. Steel saddles were welded to the side wall of the cask to enhance the stresses imposed upon the cask in the region of the introduced flaw. The programme demonstrated the applicability of a fracture mechanics methodology for predicting the conditions under which brittle fracture may occur and thereby the utility of fracture mechanics design for ensuring cask structural integrity by ensuring an appropriate margin of safety. Positive assessments of ductile iron for cask containment and the quality of the casting process for producing ductile iron casks were made. The results of this programme have provided data to support IAEA efforts to develop brittle fracture acceptance criteria for cask containment. (author)

  11. Defect forces, defect couples and path integrals in fracture mechanics

    International Nuclear Information System (INIS)

    Roche, R.L.

    1979-07-01

    In this work, it is shown that the path integrals can be introduced without any reference to the material behavior. The method is based on the definition in a continuous medium of a set of vectors and couples having the dimension of a force or a moment. More precisely, definitions are given of volume defect forces, surface defect forces, volume defect couples, and surface defect couples. This is done with the help of the stress working variation of a particule moving through the solid. The most important result is: the resultant of all the defect forces included in a volume V is the J integral on the surface surrounding V and the moment resultant is the L integral. So these integrals are defined without any assumption on the material constitutive equation. Another result is the material form of the virtual work principle - defect forces are acting like conventional forces in the conventional principles of virtual work. This lead to the introduction of the energy momentum tensor and of the associated couple stress. Application of this method is made to fracture mechanics in studying the defect forces distribution around a crack [fr

  12. Fracture Mechanics Analyses for Interface Crack Problems - A Review

    Science.gov (United States)

    Krueger, Ronald; Shivakumar, Kunigal; Raju, Ivatury S.

    2013-01-01

    Recent developments in fracture mechanics analyses of the interfacial crack problem are reviewed. The intent of the review is to renew the awareness of the oscillatory singularity at the crack tip of a bimaterial interface and the problems that occur when calculating mode mixity using numerical methods such as the finite element method in conjunction with the virtual crack closure technique. Established approaches to overcome the nonconvergence issue of the individual mode strain energy release rates are reviewed. In the recent literature many attempts to overcome the nonconvergence issue have been developed. Among the many approaches found only a few methods hold the promise of providing practical solutions. These are the resin interlayer method, the method that chooses the crack tip element size greater than the oscillation zone, the crack tip element method that is based on plate theory and the crack surface displacement extrapolation method. Each of the methods is validated on a very limited set of simple interface crack problems. However, their utility for a wide range of interfacial crack problems is yet to be established.

  13. Fracturing mechanics before valve-in-valve therapy of small aortic bioprosthetic heart valves.

    Science.gov (United States)

    Johansen, Peter; Engholt, Henrik; Tang, Mariann; Nybo, Rasmus F; Rasmussen, Per D; Nielsen-Kudsk, Jens Erik

    2017-10-13

    Patients with degraded bioprosthetic heart valves (BHV) who are not candidates for valve replacement may benefit from transcatheter valve-in-valve (VIV) therapy. However, in smaller-sized surgical BHV the resultant orifice may become too narrow. To overcome this, the valve frame can be fractured by a high-pressure balloon prior to VIV. However, knowledge on fracture pressures and mechanics are prerequisites. The aim of this study was to identify the fracture pressures needed in BHV, and to describe the fracture mechanics. Commonly used BHV of small sizes were mounted on a high-pressure balloon situated in a biplane fluoroscopic system with a high-speed camera. The instant of fracture was captured along with the balloon pressure. The valves were inspected for material protrusion and later dissected for fracture zone investigation and description. The valves with a polymer frame fractured at a lower pressure (8-10 atm) than those with a metal stent (19-26 atm). None of the fractured valves had elements protruding. VIV procedures in small-sized BHV may be performed after prior fracture of the valve frame by high-pressure balloon dilatation. This study provides tentative guidelines for expected balloon sizes and pressures for valve fracturing.

  14. Essential work of fracture analysis for starch filled poly(propylene carbonate) composites

    International Nuclear Information System (INIS)

    Wang, X.L.; Li, R.K.Y.; Cao, Y.X.; Meng, Y.Z.

    2007-01-01

    Starch filled poly(propylene carbonate) composites are environmental friendly materials. In this study, the fracture toughness of composites under mode I loading was determined by the essential work of fracture concept. The specific essential fracture work of the poly(propylene carbonate)/starch composites decreases with increasing the starch content, while the non-essential work term, βw p increases with increasing the starch content. In addition, the morphologies, thermal properties, thermo-mechanical properties were studied by scanning electron microscope, thermogravimetric analysis, dynamic mechanical analysis, and differential scanning calorimetry, respectively. The thermal and thermo-mechanical measurements revealed that increasing starch content led to an increase in glass transition temperature and thermal stability. Morphology observation indicates that poly(propylene carbonate) and starch have weak interfacial adhesion

  15. QAPP for Hydraulic Fracturing (HF) Surface Spills Data Analysis

    Science.gov (United States)

    This QAPP provides information concerning the analysis of spills associated with hydraulic fracturing. This project is relevant to both the chemical mixing and flowback and produced water stages of the HF water cycle as found in the HF Study Plan.

  16. Mean load effect on fatigue of welded joints using structural stress and fracture mechanics approach

    International Nuclear Information System (INIS)

    Kim, Jong Sung; Kim, Cheol; Jin, Tae Eun; Dong, P.

    2006-01-01

    In order to ensure the structural integrity of nuclear welded structures during design life, the fatigue life has to be evaluated by fatigue analysis procedures presented in technical codes such as ASME B and PV Code Section III. However, existing fatigue analysis procedures do not explicitly consider the presence of welded joints. A new fatigue analysis procedure based on a structural stress/fracture mechanics approach has been recently developed in order to reduce conservatism by erasing uncertainty in the analysis procedure. A recent review of fatigue crack growth data under various mean loading conditions using the structural stress/fracture mechanics approach, does not consider the mean loading effect, revealed some significant discrepancies in fatigue crack growth curves according to the mean loading conditions. In this paper, we propose the use of the stress intensity factor range ΔK characterized with loading ratio R effects in terms of the structural stress. We demonstrate the effectiveness in characterizing fatigue crack growth and S-N behavior using the well-known data. It was identified that the S-N data under high mean loading could be consolidated in a master S-N curve for welded joints

  17. Analysis of Flow Behavior for Acid Fracturing Wells in Fractured-Vuggy Carbonate Reservoirs

    Directory of Open Access Journals (Sweden)

    Mingxian Wang

    2018-01-01

    Full Text Available This study develops a mathematical model for transient flow analysis of acid fracturing wells in fractured-vuggy carbonate reservoirs. This model considers a composite system with the inner region containing finite number of artificial fractures and wormholes and the outer region showing a triple-porosity medium. Both analytical and numerical solutions are derived in this work, and the comparison between two solutions verifies the model accurately. Flow behavior is analyzed thoroughly by examining the standard log-log type curves. Flow in this composite system can be divided into six or eight main flow regimes comprehensively. Three or two characteristic V-shaped segments can be observed on pressure derivative curves. Each V-shaped segment corresponds to a specific flow regime. One or two of the V-shaped segments may be absent in particular cases. Effects of interregional diffusivity ratio and interregional conductivity ratio on transient responses are strong in the early-flow period. The shape and position of type curves are also influenced by interporosity coefficients, storativity ratios, and reservoir radius significantly. Finally, we show the differences between our model and the similar model with single fracture or without acid fracturing and further investigate the pseudo-skin factor caused by acid fracturing.

  18. Probabilistic fracture mechanics of nuclear structural components: consideration of transition from embedded crack to surface crack

    International Nuclear Information System (INIS)

    Yagawa, G.; Yoshimura, S.

    1999-01-01

    This paper describes a probabilistic fracture mechanics (PFM) analysis of aged nuclear reactor pressure vessel (RPV) material. New interpolation formulas of three-dimensional stress intensity factors are presented for both embedded elliptical surface cracks and semi-elliptical surface cracks. To investigate effects of transition from embedded crack to surface crack in PFM analyses, one of the PFM round-robin problems set by JSME-RC111 committee (i.e. aged RPV under normal and upset operating conditions) is solved, employing the interpolation formulas. (orig.)

  19. Three-dimensional elastic--plastic stress and strain analyses for fracture mechanics: complex geometries

    International Nuclear Information System (INIS)

    Bellucci, H.J.

    1975-11-01

    The report describes the continuation of research into capability for three-dimensional elastic-plastic stress and strain analysis for fracture mechanics. A computer program, MARC-3D, has been completed and was used to analyze a cylindrical pressure vessel with a nozzle insert. A method for generating crack tip elements was developed and a model was created for a cylindrical pressure vessel with a nozzle and an imbedded flaw at the inside nozzle corner. The MARC-3D program was again used to analyze this flawed model. Documentation for the use of the MARC-3D computer program has been included as an appendix

  20. Integrity evaluation of power plant components by fracture mechanics and related techniques

    International Nuclear Information System (INIS)

    Mukherjee, B.; Vanderglas, M.L.; Davies, P.H.

    1982-01-01

    Power plant components can be subject to unexpected failures with serious consequences, unless careful attention is paid to minute crack defects and their possible growth. The Linear Elastic Fracture Mechanics approach to structural integrity evaluation, as it appears in the ASME Code, is discussed. Projects related to material data generation and the development of structural analysis methods to make the above method usable are described. Several integrity-related questions outside the scope of the Code guidelines are documented, concluding with comments on possible future developments

  1. CANDIDATE GENE ANALYSIS IN ISRAELI SOLDIERS WITH STRESS FRACTURES

    Directory of Open Access Journals (Sweden)

    Ran Yanovich

    2012-03-01

    Full Text Available To investigate the association of polymorphisms within candidate genes which we hypothesized may contribute to stress fracture predisposition, a case-control, cross- sectional study design was employed. Genotyping 268 Single Nucleotide Polymorphisms- SNPs within 17 genes in 385 Israeli young male and female recruits (182 with and 203 without stress fractures. Twenty-five polymorphisms within 9 genes (NR3C1, ANKH, VDR, ROR2, CALCR, IL6, COL1A2, CBG, and LRP4 showed statistically significant differences (p < 0.05 in the distribution between stress fracture cases and non stress fracture controls. Seventeen genetic variants were associated with an increased stress fracture risk, and eight variants with a decreased stress fracture risk. None of the SNP associations remained significant after correcting for multiple comparisons (false discovery rate- FDR. Our findings suggest that genes may be involved in stress fracture pathogenesis. Specifically, the CALCR and the VDR genes are intriguing candidates. The putative involvement of these genes in stress fracture predisposition requires analysis of more cases and controls and sequencing the relevant genomic regions, in order to define the specific gene mutations

  2. 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)

  3. Failure conditions from push out tests of a steel-concrete joint: fracture mechanics approach

    Czech Academy of Sciences Publication Activity Database

    Klusák, Jan; Seitl, Stanislav; De Corte, W.; Helincks, P.; Boel, V.; De Schutter, G.

    488-489, - (2012), s. 710-713 ISSN 1013-9826. [International Conference on Fracture and Damage Mechanics - FDM 2011 /10./. Dubrovník, 19.09.2011-21.09.2011] R&D Projects: GA ČR GAP108/10/2049 Institutional research plan: CEZ:AV0Z20410507 Keywords : Push out test * generalized linear elastic fracture mechanics * bi-material notch Subject RIV: JL - Materials Fatigue, Friction Mechanics

  4. The elasto plastic fracture mechanics in ductile metal sheets

    International Nuclear Information System (INIS)

    Khan, M.A.; Malik, M.N.; Naeem, A.; Haq, A.U.; Atkins, A.G.

    1999-01-01

    The crack initiation of propagation in ductile metal sheets are caused by various micro and macro changes taking place due to material properties, applied loads, shape of the indenter (tool geometry) and the environmental conditions. These microstructural failures are directly related to the atomic bonding, crystal lattices, grain boundary status, material flaws in matrix, inhomogeneities and anisotropy in the metal sheets. The Elasto-Plastic related energy based equations are applied to these Rigid Plastic materials to determine the onset of fracture in metal forming. The combined stress and strain criterion of a critical plastic work per unit volume is no more considered as a universal ductile fracture criterion, rather a critical plastic work per unit volume dependence on all sort of stresses (hydrostatic) are the required features for the sheet metal failure (fracture). In this present study, crack initiation and propagation are related empirically with fracture toughness and the application of the theory in industry to save energy. (author)

  5. Fracture mechanical analysis of operational damaged piping

    International Nuclear Information System (INIS)

    Azodi, D.

    1987-01-01

    A series of crack arrest experiments by means of transverse wedge-loaded compact specimen was simulated numerically to verify the dynamic J-integral formulation, for applications in brittle and ductile regions as well as for two- and three-dimensional geometries. The transverse wedge-loaded compact crack arrest test is a widely used small scale test to evaluate the crack arrest toughness of nuclear pressure vessel steels. In this test method the crack attains a high velocity after initiation, then decelerates to a low velocity prior to arrest. The opening displacement remains constant during the crack propagation. Crack extension and the opening displacement behaviour were measured using a sensitive time scale. Regarding material toughness two entirely different kind of steels, HFX 760 (brittle) and 20 MnMoNi 55 (ductile) were considered. The testing temperature was the room temperature. The numerical analyses were performed by an extended version of the finite element code ADINA. Crack propagation was simulated by 'node shift and fixity release' procedure. Discussions in this report are, among others, directed to the: Numerical stability of different J-integral contours during the fast crack propagation and comparison between the static approach, dynamic finite element analyses and experimental results for crack initiation toughness and arrest toughness. The numerical simulation results and experimental data were in close agreement. The achieved results confirm that the dynamic J-integral formulation is able to describe the rapid crack propagation and the crack arrest in steel components sufficiently. (orig.) [de

  6. Moisture desorption in mechanically masticated fuels: effects of particle fracturing and fuelbed compaction

    Science.gov (United States)

    Jesse K. Kreye; J.Morgan Varner; Eric E. Knapp

    2012-01-01

    Mechanical mastication is increasingly used as a wildland fuel treatment, reducing standing trees and shrubs to compacted fuelbeds of fractured woody fuels. One major shortcoming in our understanding of these fuelbeds is how particle fracturing influences moisture gain or loss, a primary determinant of fire behaviour. To better understand fuel moisture dynamics, we...

  7. Probabilistic finite elements for fracture and fatigue analysis

    Science.gov (United States)

    Liu, W. K.; Belytschko, T.; Lawrence, M.; Besterfield, G. H.

    1989-01-01

    The fusion of the probabilistic finite element method (PFEM) and reliability analysis for probabilistic fracture mechanics (PFM) is presented. A comprehensive method for determining the probability of fatigue failure for curved crack growth was developed. The criterion for failure or performance function is stated as: the fatigue life of a component must exceed the service life of the component; otherwise failure will occur. An enriched element that has the near-crack-tip singular strain field embedded in the element is used to formulate the equilibrium equation and solve for the stress intensity factors at the crack-tip. Performance and accuracy of the method is demonstrated on a classical mode 1 fatigue problem.

  8. Evaluation of piping fracture analysis method by benchmark study, 1

    International Nuclear Information System (INIS)

    Takahashi, Yukio; Kashima, Koichi; Kuwabara, Kazuo

    1987-01-01

    Importance of strength evaluation methods for cracked piping is growing with the progress of the rationalization of the nuclear piping system based on the leak-before-break concept. As an analytical tool, finite element method is principally used. To obtain the reliable solutions by the finite element programs, it is important to grasp the influences of various factors on the solutions. In this study, benchmark analysis is carried out for a stainless steel pipe with a circumferential through-wall crack subjected to four-point bending loading. Eight solutions obtained by using five finite element programs are compared with each other. Good agreement is obtained between the solutions on the deformation characteristics as well as fracture mechanics parameters. It is found through this study that the influence of the difference in the solution technique is generally small. (author)

  9. Compartmentalization analysis using discrete fracture network models

    Energy Technology Data Exchange (ETDEWEB)

    La Pointe, P.R.; Eiben, T.; Dershowitz, W. [Golder Associates, Redmond, VA (United States); Wadleigh, E. [Marathon Oil Co., Midland, TX (United States)

    1997-08-01

    This paper illustrates how Discrete Fracture Network (DFN) technology can serve as a basis for the calculation of reservoir engineering parameters for the development of fractured reservoirs. It describes the development of quantitative techniques for defining the geometry and volume of structurally controlled compartments. These techniques are based on a combination of stochastic geometry, computational geometry, and graph the theory. The parameters addressed are compartment size, matrix block size and tributary drainage volume. The concept of DFN models is explained and methodologies to compute these parameters are demonstrated.

  10. An extension of fracture mechanics/technology to larger and smaller cracks/defects

    Science.gov (United States)

    Abé, Hiroyuki

    2009-01-01

    Fracture mechanics/technology is a key science and technology for the design and integrity assessment of the engineering structures. However, the conventional fracture mechanics has mostly targeted a limited size of cracks/defects, say of from several hundred microns to several tens of centimeters. The author and his group has tried to extend that limited size and establish a new version of fracture technology for very large cracks used in geothermal energy extraction and for very small cracks/defects or damage often appearing in the combination of mechanical and electronic components of engineering structures. Those new versions are reviewed in this paper. PMID:19907123

  11. Some probabilistic aspects of fracture

    International Nuclear Information System (INIS)

    Thomas, J.M.

    1982-01-01

    Some probabilistic aspects of fracture in structural and mechanical components are examined. The principles of fracture mechanics, material quality and inspection uncertainty are formulated into a conceptual and analytical framework for prediction of failure probability. The role of probabilistic fracture mechanics in a more global context of risk and optimization of decisions is illustrated. An example, where Monte Carlo simulation was used to implement a probabilistic fracture mechanics analysis, is discussed. (orig.)

  12. Thermo-hydro-mechanical simulation of a 3D fractured porous rock: preliminary study of coupled matrix-fracture hydraulics

    International Nuclear Information System (INIS)

    Canamon, I.; Javier Elorza, F.; Ababou, R.

    2007-01-01

    We present a problem involving the modeling of coupled flow and elastic strain in a 3D fractured porous rock, which requires prior homogenization (up-scaling) of the fractured medium into an equivalent Darcian anisotropic continuum. The governing equations form a system of PDE's (Partial Differential Equations) and, depending on the case being considered, this system may involve two different types of 'couplings' (in a real system, both couplings (1) and (2) generally take place): 1) Hydraulic coupling in a single (no exchange) or in a dual matrix-fracture continuum (exchange); 2) Thermo-Hydro-Mechanical interactions between fluid flow, pressure, elastic stress, strain, and temperature. We present here a preliminary model and simulation results with FEMLAB R , for the hydraulic problem with anisotropic heterogeneous coefficients. The model is based on data collected at an instrumented granitic site (FEBEX project) for studying a hypothetical nuclear waste repository at the Grimsel Test Site in the Swiss Alps. (authors)

  13. Constitutive relations in plasticity, damage and fracture mechanics based on a work property

    International Nuclear Information System (INIS)

    Marigo, J.J.

    1989-01-01

    This paper is devoted to restrictions imposed by a work property of Drucker-Iliushin's type on the general class of mechanical systems with an elastic range which contains plastic, damaged and cracked media. The analysis is purely mechanical and quasi-static. Starting from very weak assumptions relative to this constitutive class, we obtain a fundamental inequality which generalizes Hill's maximal work principle. So we can justify, for instance: the convexity of the elastic domain and the normality rule of the plastic strain rate in stress space for the infinitesimal and some finite plasticity theories, Griffith's criterion in brittle fracture mechanics, and we obtain some original results for elastic and elastic plastic damaged materials. It must be noted that the procedure is purely deductive, the assumptions are explicit and the results are implications

  14. Fracture mechanics model of stone comminution in ESWL and implications for tissue damage

    Science.gov (United States)

    Lokhandwalla, Murtuza; Sturtevant, Bradford

    2000-07-01

    Focused shock waves administered during extracorporeal shock-wave lithotripsy (ESWL) cause stone fragmentation. The process of stone fragmentation is described in terms of a dynamic fracture process. As is characteristic of all brittle materials, fragmentation requires nucleation, growth and coalescence of flaws, caused by a tensile or shear stress. The mechanisms, operative in the stone, inducing these stresses have been identified as spall and compression-induced tensile microcracks, nucleating at pre-existing flaws. These mechanisms are driven by the lithotripter-generated shock wave and possibly also by cavitation effects in the surrounding fluid. In this paper, the spall mechanism has been analysed, using a cohesive-zone model for the material. The influence of shock wave parameters, and physical properties of stone, on stone comminution is described. The analysis suggests a potential means to exploit the difference between the stone and tissue physical properties, so as to make stone comminution more effective, without increasing tissue damage.

  15. Study of gas production from shale reservoirs with multi-stage hydraulic fracturing horizontal well considering multiple transport mechanisms

    Science.gov (United States)

    Wei, Mingzhen; Liu, Hong

    2018-01-01

    Development of unconventional shale gas reservoirs (SGRs) has been boosted by the advancements in two key technologies: horizontal drilling and multi-stage hydraulic fracturing. A large number of multi-stage fractured horizontal wells (MsFHW) have been drilled to enhance reservoir production performance. Gas flow in SGRs is a multi-mechanism process, including: desorption, diffusion, and non-Darcy flow. The productivity of the SGRs with MsFHW is influenced by both reservoir conditions and hydraulic fracture properties. However, rare simulation work has been conducted for multi-stage hydraulic fractured SGRs. Most of them use well testing methods, which have too many unrealistic simplifications and assumptions. Also, no systematical work has been conducted considering all reasonable transport mechanisms. And there are very few works on sensitivity studies of uncertain parameters using real parameter ranges. Hence, a detailed and systematic study of reservoir simulation with MsFHW is still necessary. In this paper, a dual porosity model was constructed to estimate the effect of parameters on shale gas production with MsFHW. The simulation model was verified with the available field data from the Barnett Shale. The following mechanisms have been considered in this model: viscous flow, slip flow, Knudsen diffusion, and gas desorption. Langmuir isotherm was used to simulate the gas desorption process. Sensitivity analysis on SGRs’ production performance with MsFHW has been conducted. Parameters influencing shale gas production were classified into two categories: reservoir parameters including matrix permeability, matrix porosity; and hydraulic fracture parameters including hydraulic fracture spacing, and fracture half-length. Typical ranges of matrix parameters have been reviewed. Sensitivity analysis have been conducted to analyze the effect of the above factors on the production performance of SGRs. Through comparison, it can be found that hydraulic fracture

  16. Fracture of nasal bones: an epidemiologic analysis

    Directory of Open Access Journals (Sweden)

    Fornazieri, Marco Aurélio

    2008-12-01

    Full Text Available Introduction: One of the most common diseases in the otorhinolaryngology emergency room is the nasal bones fracture. The peak of incidence is between 15 and 25 years of age. Generally men are more affected. Objective: To analyze the age, gender and the most frequent causes of nasal fractures evaluated in the otorhinolaryngology service of a tertiary hospital. Method: Retrospective study of records of the patients with nasal fracture diagnosis treated between July 1st, 2003 and July 1st, 2007. Results: 167 patients with nasal bones fracture were included in the study, including 134 men and 33 women. Violence was the most frequent cause, with 55 cases (32.9%, followed by fall from their own height, with 33 cases (19.7%, and motorcycle accident, 14 cases (8.4%. The most common age was between 21 and 39 years (46.1%. Conclusion: Male, age between 21 and 39 years and violence are the most common characteristics found in our service. Motorcycle accidents also play an important role in this affection.

  17. Proceedings of the 1985 pressure vessels and piping conference. Volume PVP-98-8. Fracture, fatigue and advanced mechanics

    International Nuclear Information System (INIS)

    Short, W.E.; Zamrik, S.Y.

    1985-01-01

    State-of-the-art engineering practices in pressure vessel and piping technology are the result of continual efforts in the evaluation of problems which have been experienced and the development of appropriate design and analysis methods for those applications. The resulting advances in technology benefit industry with properly engineered, safe, cost-effective pressure vessels and piping systems. To this end, advanced study continues in specialized areas of mechanical engineering such as fracture mechanics, experimental stress analysis, high pressure applications and related material considerations, as well as advanced techniques for evaluation of commonly encountered design problems. This volume is comprised of current technical papers on various aspects of fracture, fatigue and advanced mechanics as related to the design and analysis of pressure vessels and piping

  18. The radiation swelling effect on fracture properties and fracture mechanisms of irradiated austenitic steels. Part II. Fatigue crack growth rate

    Energy Technology Data Exchange (ETDEWEB)

    Margolin, B., E-mail: margolinbz@yandex.ru; Minkin, A.; Smirnov, V.; Sorokin, A.; Shvetsova, V.; Potapova, V.

    2016-11-15

    The experimental data on the fatigue crack growth rate (FCGR) have been obtained for austenitic steel of 18Cr-10Ni-Ti grade (Russian analog of AISI 321 steel) irradiated up to neutron dose of 150 dpa with various radiation swelling. The performed study of the fracture mechanisms for cracked specimens under cyclic loading has explained why radiation swelling affects weakly FCGR unlike its effect on fracture toughness. Mechanical modeling of fatigue crack growth has been carried out and the dependencies for prediction of FCGR in irradiated austenitic steel with and with no swelling are proposed and verified with the obtained experimental results. As input data for these dependencies, FCGR for unirradiated steel and the tensile mechanical properties for unirradiated and irradiated steels are used.

  19. Mechanics of the Delayed Fracture of Viscoelastic Bodies with Cracks: Theory and Experiment (Review)

    Science.gov (United States)

    Kaminsky, A. A.

    2014-09-01

    Theoretical and experimental studies on the deformation and delayed fracture of viscoelastic bodies due to slow subcritical crack growth are reviewed. The focus of this review is on studies of subcritical growth of cracks with well-developed fracture process zones, the conditions that lead to their critical development, and all stages of slow crack growth from initiation to the onset of catastrophic growth. Models, criteria, and methods used to study the delayed fracture of viscoelastic bodies with through and internal cracks are analyzed. Experimental studies of the fracture process zones in polymers using physical and mechanical methods as well as theoretical studies of these zones using fracture mesomechanics models that take into account the structural and rheological features of polymers are reviewed. Particular attention is given to crack growth in anisotropic media, the effect of the aging of viscoelastic materials on their delayed fracture, safe external loads that do not cause cracks to propagate, the mechanism of multiple-flaw fracture of viscoelastic bodies with several cracks and, especially, processes causing cracks to coalesce into a main crack, which may result in a break of the body. Methods and results of solving two- and three-dimensional problems of the mechanics of delayed fracture of aging and non-aging viscoelastic bodies with cracks under constant and variable external loads, wedging, and biaxial loads are given

  20. Fractures of the mandible and maxilla: A 10-year analysis

    Directory of Open Access Journals (Sweden)

    Estie Kruger

    2016-01-01

    Full Text Available Background Previous analysis of jaw fracture hospitalisations in Western Australia (WA indicated disproportionately high rates of hospitalisations for Aboriginal people. This study was to follow-up on the earlier analysis to determine if inequalities in terms of jaw fracture hospitalisation rates between Aboriginal and non-Aboriginal people have changed. Aims This study, done over a 10-year period from 1999/2000 to 2008/2009, aimed to determine rates of hospitalisations for jaw fractures in WA, trends over the 10–year period, and direct costs associated with these hospital admissions. Methods Hospitalisation data were obtained from the Western Australian Hospital Morbidity Data System (HMDS. Episodes were selected on the basis of an ICD10-AM code being S02.4 (Fracture of the malar and maxillary bones and S02.6 (Fracture of the mandible. Self-reported Aboriginality were used to compare Aboriginal to non-Aboriginal populations. Estimated cost of care was determined for each episode using the national standard diagnostic-related group (DRG average price. Results Our findings indicate that inequalities between Aboriginal and non-Aboriginal people in terms of hospital admissions for jaw fractures exist in WA, and continued over a decade-long period. Higher fracture rates occurred amongst males, Aboriginal people, younger adult age-groups, those from low socioeconomic areas, and those from remote and very remote areas. The DRG cost per person for jaw fractures ranged between AUD $842 and $109,002, with a median cost of $4,965. Conclusion Hospital admission rates for the treatment of maxillary and mandibular fractures is very strongly divided along racial and socioeconomic lines in WA.

  1. A Mathematical Pressure Transient Analysis Model for Multiple Fractured Horizontal Wells in Shale Gas Reservoirs

    Directory of Open Access Journals (Sweden)

    Yan Zeng

    2018-01-01

    Full Text Available Multistage fractured horizontal wells (MFHWs have become the main technology for shale gas exploration. However, the existing models have neglected the percolation mechanism in nanopores of organic matter and failed to consider the differences among the reservoir properties in different areas. On that account, in this study, a modified apparent permeability model was proposed describing gas flow in shale gas reservoirs by integrating bulk gas flow in nanopores and gas desorption from nanopores. The apparent permeability was introduced into the macroseepage model to establish a dynamic pressure analysis model for MFHWs dual-porosity formations. The Laplace transformation and the regular perturbation method were used to obtain an analytical solution. The influences of fracture half-length, fracture permeability, Langmuir volume, matrix radius, matrix permeability, and induced fracture permeability on pressure and production were discussed. Results show that fracture half-length, fracture permeability, and induced fracture permeability exert a significant influence on production. A larger Langmuir volume results in a smaller pressure and pressure derivative. An increase in matrix permeability increases the production rate. Besides, this model fits the actual field data relatively well. It has a reliable theoretical foundation and can preferably describe the dynamic changes of pressure in the exploration process.

  2. Strength and fracture mechanism of iron reinforced tricalcium phosphate cermet fabricated by spark plasma sintering.

    Science.gov (United States)

    Tkachenko, Serhii; Horynová, Miroslava; Casas-Luna, Mariano; Diaz-de-la-Torre, Sebastian; Dvořák, Karel; Celko, Ladislav; Kaiser, Jozef; Montufar, Edgar B

    2018-05-01

    The present work studies the microstructure and mechanical performance of tricalcium phosphate (TCP) based cermet toughened by iron particles. A novelty arises by the employment of spark plasma sintering for fabrication of the cermet. Results showed partial transformation of initial alpha TCP matrix to beta phase and the absence of oxidation of iron particles, as well as a lack of chemical reaction between TCP and iron components during sintering. The values of compressive and tensile strength of TCP/Fe cermet were 3.2 and 2.5 times, respectively, greater than those of monolithic TCP. Fracture analysis revealed the simultaneous action of crack-bridging and crack-deflection microstructural toughening mechanisms under compression. In contrast, under tension the reinforcing mechanism was only crack-bridging, being the reason for smaller increment of strength. Elastic properties of the cermet better matched values reported for human cortical bone. Thereby the new TCP/Fe cermet has potential for eventual use as a material for bone fractures fixation under load-bearing conditions. Copyright © 2018 Elsevier Ltd. All rights reserved.

  3. Consideration on the Mechanism of Microwave Emission Due to Rock Fracture

    Science.gov (United States)

    Takano, Tadashi; Sugita, Seiji; Yoshida, Shingo; Maeda, Takashi

    2010-05-01

    Microwave emission due to rock fracture was found at 300 MHz, 2 GHz, and 22 GHz, and its power was calibrated in laboratory for the first time in the world. The observed waveform is impulsive, and contains correspondent frequency component inside the envelope at each frequency band. At such high frequencies, the electro-magnetic signal power can be calibrated as a radiating wave with high accuracy. Accordingly, it was verified that a substantial power is emitted. The microwave emission phenomena were also observed on occasions of hypervelocity impact, and esteemed as phenomena generally associated with material destruction. Earthquakes and volcanic activities are association with rock fractures so that the microwave is expected to be emitted. Actually, the e emission was confirmed by the data analysis of the brightness temperature obtained by a remote sensing satellite, which flew over great earthquakes of Wuenchan and Sumatra, and great volcanic eruptions of Reventador and Chanten. It is important to show the microwave emission during rock fracture in natural phenomena. Therefore, the field test to detect the microwave due to the collapse of a crater cliff was planned and persecuted at the volcano of Miyake-jima about 100 km south of Tokyo. Volcanic activity may be more convenient than an earthquake because of the known location and time. As a result, they observed the microwave emission which was strongly correlated with the cliff collapses. Despite of the above-mentioned phenomenological fruits, the reason of the microwave emission is not fixed yet. We have investigated the mechanism of the emission in consideration of the obtained data in rock fracture experiments so far and the study results on material destruction by hypervelocity impact. This paper presents the proposal of the hypothesis and resultant discussions. The microwave sensors may be useful to monitor natural hazards such as an earthquake or a volcanic eruption, because the microwave due to rock

  4. Tensile properties and fracture mechanism of IN-100 superalloy in high temperature range

    Directory of Open Access Journals (Sweden)

    Milan T. Jovanović

    2017-06-01

    Full Text Available Tensile properties and fracture mechanism of a polycrystalline IN-100 superalloy have been investigated in the range from room temperature to 900°C. Optical microscopy (OM and transmission electron microscopy (TEM applying replica technique were used for microstructural investigation, whereas scanning electron microscopy (SEM was utilized for fracture study. High temperature tensile tests were carried out in vacuumed chamber. Results show that strength increases up to 700°C, and then sharply decreases with further increase in temperature. Elongation increases very slowly (6-7.5% till 500°C, then decreases to 4.5% at 900°C. Change in elongation may be ascribed to a change of fracture mechanism. Appearance of a great number of microvoids prevails up to 500°C resulting in a slow increase of elongation, whereas above this temperature elongation decrease is correlated with intergranular crystallographic fracture and fracture of carbides.

  5. Continuum and micro-mechanics treatment of constraint in fracture

    International Nuclear Information System (INIS)

    Dodds, R.H. Jr.; Shih, C.F.

    1993-01-01

    This paper explores the fundamental concepts of the J-Q description of crack-tip fields, the fracture toughness locus and micromechanics approaches to predict the variability of macroscopic fracture toughness with constraint under elastic-plastic conditions. While these concepts derived from plane-strain considerations, initial applications in fully 3-D geometries are very promising. Computational results are presented for a surface cracked plate containing a 6:1 semi-elliptical, a=t/4 flaw subjected to remote uniaxial and biaxial tension. Crack-tip stress fields consistent with the J-Q theory are demonstrated to exist at each location along the crack front. The micromechanics model employs the J-Q description of crack-front stresses to interpret fracture toughness values measured on laboratory specimens for fracture assessment of the surface cracked plate. The computational results suggest only a minor effect of the biaxial loading on the crack tip stress fields and, consequently, on the propensity for fracture relative to the uniaxial loading. 45 refs., 19 figs., 3 tabs

  6. The use of fracture mechanics for the evaluation of NDE flaw acceptance standards

    Energy Technology Data Exchange (ETDEWEB)

    Alicino, A; Capurro, E; Ansaldo, Sp; Corvi, A [Ansaldo SpA, Genoa (Italy)

    1988-12-31

    This document deals with the use of fracture mechanics criteria to evaluate the Non Destructive Examination (NDE) flaw acceptance standards. The communication discusses the general schemes and the guidelines of the activity carried out. (TEC).

  7. Forming limit and fracture mechanism of ferritic stainless steel sheets

    International Nuclear Information System (INIS)

    Xu Le; Barlat, Frederic; Ahn, Deok Chan; Bressan, Jose Divo

    2011-01-01

    Research highlights: → Forming limit curves of two ferritic stainless steel sheets were well predicted. → Failure occurs by necking in uniaxial and plane strain tension for both materials. → Failure occurs by shearing in balanced biaxial tension for both materials. → Strain rate sensitivity does not affect the limit strains a lot for both materials. → Strain rate sensitivity likely influences the failure mode for both materials. - Abstract: In this work, the forming limit curves (FLCs) of two ferritic stainless steel sheets, AISI409L and AISI430, were predicted with the Marciniak-Kuczynski (MK) and Bressan-William-Hill (BWH) models, combined with the Yld2000-2d yield function and the Swift hardening law. Uniaxial tension, disk compression and hydraulic bulge tests were performed to determine the yield loci and hardening curves of both materials. Meanwhile, the strain rate sensitivity (SRS) coefficient was measured through uniaxial tension tests carried out at different strain rates. Out-of-plane stretching tests were conducted in sheet specimens to obtain the surface limit strains under different linear strain paths. Micrographs of the specimens fractured in different stress states were obtained by optical and scanning electron microscopy. The overall results show that the BWH model can predict the FLC better than the MK model, and that the SRS does not have much effect on the limit strains for both materials. The predicted FLCs and micrograph analysis both indicate that failure occurs by surface localized necking in uniaxial and plane strain tension states, whereas it occurs by localized shearing in the through thickness direction in balanced biaxial tension state.

  8. Subcritical fracture propagation in rocks: An examination using the methods of fracture mechanics and non-destructive testing. Ph.D. Thesis

    Science.gov (United States)

    Swanson, P. L.

    1984-01-01

    An experimental investigation of tensile rock fracture is presented with an emphasis on characterizing time dependent crack growth using the methods of fracture mechanics. Subcritical fracture experiments were performed in moist air on glass and five different rock types at crack velocities using the double torsion technique. The experimental results suggest that subcritical fracture resistance in polycrystals is dominated by microstructural effects. Evidence for gross violations of the assumptions of linear elastic fracture mechanics and double torsion theory was found in the tests on rocks. In an effort to obtain a better understanding of the physical breakdown processes associated with rock fracture, a series of nondestructive evaluation tests were performed during subcritical fracture experiments on glass and granite. Comparison of the observed process zone shape with that expected on the basis of a critical normal principal tensile stress criterion shows that the zone is much more elongated in the crack propagation direction than predicted by the continuum based microcracking model alone.

  9. Failure analysis of eleven Gates Glidden drills that fractured intraorally during post space preparation. A retrieval analysis study.

    Science.gov (United States)

    Al Jabbari, Youssef S; Fournelle, Raymond; Al Taweel, Sara M; Zinelis, Spiros

    2017-07-19

    The purpose of this study was to determine the failure mechanism of clinically failed Gates Glidden (GG) drills. Eleven retrieved GG drills (sizes #1 to #3) which fractured during root canal preparation were collected and the fracture location was recorded based on macroscopic observation. All fracture surfaces were investigated by a SEM. Then the fractured parts were embedded in acrylic resin and after metallographic preparation, the microstructure and elemental composition was evaluated by SEM and EDS. The Vickers hardness (HV) of all specimens was also determined. Macroscopic examination and SEM analysis showed that the drills failed near the hand piece end by torsional fatigue with fatigue cracks initiating at several locations around the circumference and propagating toward the center. Final fracture followed by a tensile overloading at the central region of cross section. Microstructural analysis, hardness measurements and EDS show that the drills are made of a martensitic stainless steel like AISI 440C. Based on the findings of this study, clinicians should expect fatigue fracture of GG drills that have small size during root canal preparation. Selection of a more fatigue resistant stainless steel alloy and enhancing the instrument design might reduce the incidence of quasi-cleavage fracture on GG drills.

  10. First spinning cylinder test analysis by using local approach to fracture

    International Nuclear Information System (INIS)

    Eripret, C.; Rousselier, G.

    1993-01-01

    In recent years, several experimental programs on large scale specimens were organized to evaluate capabilities of the fracture mechanics concepts employed in structural integrity assessment of PWR pressure vessels. During the first spinning cylinder test, a geometry effect was experimentally pointed out and exhibited the problem of transferability of toughness data from small scale to large scale specimens. An original analysis of this test, by means of local approach to fracture is presented in this paper. Both compact tension specimen and spinning cylinder fracture behaviour were computed by using a continuum damage mechanics model developed at EDF. The authors confirmed by numerical analysis that the cylinder's resistance to ductile tearing was considerably larger than in small scale fracture mechanics specimens tests, about 50 percent. The final crack growth predicted by the model was close to the experimental value. Discrepancies in J-R curves seemed to be due to an effect of stress triaxiality and plastic zone evolution. The geometry effect inducing differences in resistance to ductile tearing of the material involved in the specimens can be investigated and explained by using local approach to fracture methodology. 14 refs., 9 figs., 2 tabs

  11. Progress in elastic-plastic fracture mechanics and its applications

    International Nuclear Information System (INIS)

    Paris, P.C.; Zahalak, G.I.

    1980-01-01

    This paper surveys recent developments in the application of J-Integral methods to problems of elastic-plastic fracture. The analytical and experimental development of the J-Integral concept over the last ten years is reviewed briefly. Tearing instability theory is presented in general terms, and specific applications of the theory are discussed. Principles of fracture-proof design are shown to follow naturally from the tearing instability theory. These principles are illustrated first for simple structures, and then generalized to more complex configurations and loading conditions. Examples include multiple member tension structures, beams, frames, nuclear reactor pressure vessel nozzles and piping, and beams on elastic foundations. It is concluded that J-integral based methods offer the best immediate opportunity for the development of sound analytical techniques for treating important practical problems of elastic-plastic fracture

  12. Fracture Mechanics Analyses of the Slip-Side Joggle Regions of Wing-Leading-Edge Panels

    Science.gov (United States)

    Raju, Ivatury S.; Knight, Norman F., Jr.; Song, Kyongchan; Phillips, Dawn R.

    2011-01-01

    The Space Shuttle wing-leading edge consists of panels that are made of reinforced carbon-carbon. Coating spallation was observed near the slip-side region of the panels that experience extreme heating. To understand this phenomenon, a root-cause investigation was conducted. As part of that investigation, fracture mechanics analyses of the slip-side joggle regions of the hot panels were conducted. This paper presents an overview of the fracture mechanics analyses.

  13. Generalized linear elastic fracture mechanics: an application to a crack touching the bimaterial interface

    Czech Academy of Sciences Publication Activity Database

    Náhlík, Luboš; Šestáková, L.; Hutař, Pavel; Knésl, Zdeněk

    2011-01-01

    Roč. 452-453, - (2011), s. 445-448 ISSN 1013-9826 R&D Projects: GA AV ČR(CZ) KJB200410803; GA ČR GA101/09/1821 Institutional research plan: CEZ:AV0Z20410507 Keywords : generalized stress intensity factor * bimaterial interface * composite materials * strain energy density factor * fracture criterion * generalized linear elastic fracture mechanics Subject RIV: JL - Materials Fatigue, Friction Mechanics

  14. Mechanical properties and fracture behaviour of defective phosphorene nanotubes under uniaxial tension

    Science.gov (United States)

    Liu, Ping; Pei, Qing-Xiang; Huang, Wei; Zhang, Yong-Wei

    2017-12-01

    The easy formation of vacancy defects and the asymmetry in the two sublayers of phosphorene nanotubes (PNTs) may result in brand new mechanical properties and failure behaviour. Herein, we investigate the mechanical properties and fracture behaviour of defective PNTs under uniaxial tension using molecular dynamics simulations. Our simulation results show that atomic vacancies cause local stress concentration and thus significantly reduce the fracture strength and fracture strain of PNTs. More specifically, a 1% defect concentration is able to reduce the fracture strength and fracture strain by as much as 50% and 66%, respectively. Interestingly, the reduction in the mechanical properties is found to depend on the defect location: a defect located in the outer sublayer has a stronger effect than one located in the inner layer, especially for PNTs with a small diameter. Temperature is also found to strongly influence the mechanical properties of both defect-free and defective PNTs. When the temperature is increased from 0 K to 400 K, the fracture strength and fracture strain of defective PNTs with a defect concentration of 1% are reduced further by 71% and 61%, respectively. These findings are of great importance for the structural design of PNTs as building blocks in nanodevices.

  15. Model of mechanical representation of the formation of natural fractures inside a petroleum reservoir; Modele de representation mecanique de la formation des fractures naturelles d'un reservoir petrolier

    Energy Technology Data Exchange (ETDEWEB)

    Picard, D.

    2005-09-15

    The optimisation of the oil production requires a better characterisation of naturally fractured reservoirs. We consider and analyse two spatial distributions. One with systematic joints is arranged in an homogeneous way; joint spacing is linked to individual bedding thickness with propagation frequently interrupted by stratigraphic interfaces (single layer jointing). The second, so-called fracture swarms, consists in fractures clustering, where stratigraphic interfaces seem to play a minor role. The analysis is based on the singularity theory and matched asymptotic expansions method with a fine scale for local perturbations and a global one for general trends. We examine the conditions of fracture propagation that are determined herein using simultaneously two fracture criteria an energy and a stress condition. We consider two modes of loading. Usually, the joint (crack opening mode) and fracture swarm growths are explained by a first order phenomenon involving effective traction orthogonal to fracture plane. Although commonly used, this hypothesis seems unrealistic in many circumstances and may conflict with geological observations. Then, we try to describe fracture growth as a second order phenomena resulting from crack parallel compression. As far as propagation across layer interfaces is concerned, the effect of loading and geometry has been summarised in maps of fracture mechanisms, describing areas of 'step-over', 'straight through propagation' and 'crack arrest'. Fracture criteria, relative size of heterogeneities, contrast of mechanical properties between bed and layer are parameters of the problem. For fracture swarms, we present a discussion bringing out what is reasonable as a loading to justify their morphology. In particular, horizontal effective tension is unable to explain neighbouring joints. Simultaneous propagation of parallel near cracks is explained by finite width cracks growing under the influence of vertical

  16. Mechanical properties and fracture behavior of single-layer phosphorene at finite temperatures

    International Nuclear Information System (INIS)

    Sha, Zhen-Dong; Pei, Qing-Xiang; Ding, Zhiwei; Zhang, Yong-Wei; Jiang, Jin-Wu

    2015-01-01

    Phosphorene, a new two-dimensional (2D) material beyond graphene, has attracted great attention in recent years due to its superior physical and electrical properties. However, compared to graphene and other 2D materials, phosphorene has a relatively low Young’s modulus and fracture strength, which may limit its applications due to possible structure failures. For the mechanical reliability of future phosphorene-based nanodevices, it is necessary to have a deep understanding of the mechanical properties and fracture behaviors of phosphorene. Previous studies on the mechanical properties of phosphorene were based on first principles calculations at 0 K. In this work, we employ molecular dynamics simulations to explore the mechanical properties and fracture behaviors of phosphorene at finite temperatures. It is found that temperature has a significant effect on the mechanical properties of phosphorene. The fracture strength and strain reduce by more than 65% when the temperature increases from 0 K to 450 K. Moreover, the fracture strength and strain in the zigzag direction is more sensitive to the temperature rise than that in the armchair direction. More interestingly, the failure crack propagates preferably along the groove in the puckered structure when uniaxial tension is applied in the armchair direction. In contrast, when the uniaxial tension is applied in the zigzag direction, multiple cracks are observed with rough fracture surfaces. Our present work provides useful information about the mechanical properties and failure behaviors of phosphorene at finite temperatures. (paper)

  17. Clastic patterned ground in Lomonosov crater, Mars: examining fracture controlled formation mechanisms

    Science.gov (United States)

    Barrett, Alexander M.; Balme, Matthew R.; Patel, Manish R.; Hagermann, Axel

    2017-10-01

    The area surrounding Lomonosov crater on Mars has a high density of seemingly organised boulder patterns. These form seemingly sorted polygons and stripes within kilometre scale blockfields, patches of boulder strewn ground which are common across the Martian high latitudes. Several hypotheses have been suggested to explain the formation of clastic patterned ground on Mars. It has been proposed that these structures could have formed through freeze-thaw sorting, or conversely by the interaction of boulders with underlying fracture polygons. In this investigation a series of sites were examined to evaluate whether boulder patterns appear to be controlled by the distribution of underlying fractures and test the fracture control hypotheses for their formation. It was decided to focus on this suite of mechanisms as they are characterised by a clear morphological relationship, namely the presence of an underlying fracture network which can easily be evaluated over a large area. It was found that in the majority of examples at these sites did not exhibit fracture control. Although fractures were present at many sites there were very few sites where the fracture network appeared to be controlling the boulder distribution. In general these were not the sites with the best examples of organization, suggesting that the fracture control mechanisms are not the dominant geomorphic process organising the boulders in this area.

  18. Odontoid fractures: A retrospective analysis of 53 cases

    Directory of Open Access Journals (Sweden)

    Shetty Arjun

    2009-01-01

    Full Text Available Background: The management of odontoid fracture has evolved but controversy persists as to the best method for Type II odontoid fractures with or without atlantoaxial (AA instability. The anterior odontoid screw fixation can be associated with significant morbidity while delayed odontoid screw fixation has shown to be associated with reasonable good fusion rates. We conducted a retrospective analysis to evaluate the outcome of a trial of conservative management in type II odontoid fractures without atlantoaxial instability (Group A followed by delayed odontoid screw fixation in cases in which fusion was not achieved by conservative treatment. The outcome of type II odontoid fracture with AA subluxation (Group B was also analysed where closed reduction on traction could be achieved and in those atlantoaxial subluxations that were irreducible an intraoperative reduction was done. Materials and Methods: A retrospective evaluation of 53 cases of odontoid fractures treated over a 9-year period is being reported. All odontoid fractures without AA instability (n=29 were initially managed conservatively. Three patients who did not achieve union with conservative management were treated with delayed anterior screw fixation. Twenty-four cases of odontoid fractures were associated with AA instability; 17 of them could be reduced with skeletal traction and were managed with posterior fusion and fixation. Of the seven cases that were irreducible, the initial three cases were treated by odontoid excision followed by posterior fusion and fixation; however, in the later four cases, intra operative reduction was achieved by a manipulation procedure, and posterior fusion and fixation was performed. Results: Twenty-six of 29 cases of odontoid fracture without AA instability achieved fracture union with conservative management whereas the remaining three patients achieved union following delayed anterior odontoid screw fixation. 17 out of 24 odontoid fracture with

  19. Atomistic investigations on the mechanical properties and fracture mechanisms of indium phosphide nanowires.

    Science.gov (United States)

    Pial, Turash Haque; Rakib, Tawfiqur; Mojumder, Satyajit; Motalab, Mohammad; Akanda, M A Salam

    2018-03-28

    The mechanical properties of indium phosphide (InP) nanowires are an emerging issue due to the promising applications of these nanowires in nanoelectromechanical and microelectromechanical devices. In this study, molecular dynamics simulations of zincblende (ZB) and wurtzite (WZ) crystal structured InP nanowires (NWs) are presented under uniaxial tension at varying sizes and temperatures. It is observed that the tensile strengths of both types of NWs show inverse relationships with temperature, but are independent of the size of the nanowires. Moreover, applied load causes brittle fracture by nucleating cleavage on ZB and WZ NWs. When the tensile load is applied along the [001] direction, the direction of the cleavage planes of ZB NWs changes with temperature. It is found that the {111} planes are the cleavage planes at lower temperatures; on the other hand, the {110} cleavage planes are activated at elevated temperatures. In the case of WZ NWs, fracture of the material is observed to occur by cleaving along the (0001) plane irrespective of temperature when the tensile load is applied along the [0001] direction. Furthermore, the WZ NWs of InP show considerably higher strength than their ZB counterparts. Finally, the impact of strain rate on the failure behavior of InP NWs is also studied, and higher fracture strengths and strains at higher strain rates are found. With increasing strain rate, the number of cleavages also increases in the NWs. This paper also provides in-depth understanding of the failure behavior of InP NWs, which will aid the design of efficient InP NWs-based devices.

  20. Simulation of crack propagation in fiber-reinforced concrete by fracture mechanics

    International Nuclear Information System (INIS)

    Zhang Jun; Li, Victor C.

    2004-01-01

    Mode I crack propagation in fiber-reinforced concrete (FRC) is simulated by a fracture mechanics approach. A superposition method is applied to calculate the crack tip stress intensity factor. The model relies on the fracture toughness of hardened cement paste (K IC ) and the crack bridging law, so-called stress-crack width (σ-δ) relationship of the material, as the fundamental material parameters for model input. As two examples, experimental data from steel FRC beams under three-point bending load are analyzed with the present fracture mechanics model. A good agreement has been found between model predictions and experimental results in terms of flexural stress-crack mouth opening displacement (CMOD) diagrams. These analyses and comparisons confirm that the structural performance of concrete and FRC elements, such as beams in bending, can be predicted by the simple fracture mechanics model as long as the related material properties, K IC and (σ-δ) relationship, are known

  1. Strain rate effects on the mechanical properties and fracture mode of skeletal muscle

    Energy Technology Data Exchange (ETDEWEB)

    Shapiro, Michael; Tovar, Nick; Yoo, Daniel [Biomaterials and Biomimetics, New York University College of Dentistry (United States); Sobieraj, Micheal [Orthopedic Surgery, Hospital for Joint Diseases (United States); Gupta, Nikhil [Mechanical and Aerospace Engineering, NYU-Poly (United States); Branski, Ryan C. [Dept of Otolaryngology, New York University School of Medicine (United States); Coelho, Paulo G., E-mail: pc92@nyu.edu [Biomaterials and Biomimetics, New York University College of Dentistry (United States)

    2014-06-01

    The present study aimed to characterize the mechanical response of beagle sartorius muscle fibers under strain rates that increase logarithmically (0.1 mm/min, 1 mm/min and 10 mm/min), and provide an analysis of the fracture patterns of these tissues via scanning electron microscopy (SEM). Muscle tissue from dogs' sartorius was excised and test specimens were sectioned with a lancet into sections with nominal length, width, and thickness of 7, 2.5 and 0.6 mm, respectively. Trimming of the tissue was done so that the loading would be parallel to the direction of the muscle fiber. Samples were immediately tested following excision and failures were observed under the SEM. No statistically significant difference was observed in strength between the 0.1 mm/min (2.560 ± 0.37 MPa) and the 1 mm/min (2.702 ± 0.55 MPa) groups. However, the 10 mm/min group (1.545 ± 0.50 MPa) had a statistically significant lower strength than both the 1 mm/min group and the 0.1 mm/min group with p < 0.01 in both cases. At the 0.1 mm/min rate the primary fracture mechanism was that of a shear mode failure of the endomysium with a significant relative motion between fibers. At 1 mm/min this continues to be the predominant failure mode. At the 10 mm/min strain rate there is a significant change in the fracture pattern relative to other strain rates, where little to no evidence of endomysial shear failure nor of significant motion between fibers was detected.

  2. Study of mechanical properties and fracture mechanisms of synthetic fibers nylon-and-polyester type, used in engineering products

    International Nuclear Information System (INIS)

    Cardoso, Sergio Gomes

    2009-01-01

    Fibers are groups formed by molecular-chain-oriented filaments. Fibers play a fundamental role in human being's daily life and they can be found in several forms and geometries, such as filaments, yarns, beams, rope, fabric, composite, coatings, others. They are used in various segments such as civil, mechanical, electrical, electronics, military, naval, nautical, aviation, health, medicine, environment, communications, safety, space, others. Fibers are divided into two distinct classes: natural and chemical ones, which cover synthetic and man-made sub-classes. They can be produced from several materials, such as wool, cotton, rayon, flax, silk, rock, nylon, polyester, polyethylene, poly-propylene, aramid, glass, carbon, steel, ceramic, others. Globally, the participation of chemical fibers corresponds to approximately 59,9%, and the synthetic fiber polyester, the most used one, represents approximately 63% of the world market. Vital needs have led to the development of multi-function fibers and the focus has changed in the last 10 years with the use of nano technology for environmental responsibility and smart fibers. The study of mechanical properties and fracture mechanisms of fibers is of great relevance for characterization and understanding of causes as consequence of failures. For such reason, it was selected technical fabrics made of high performance synthetic fiber nylon-and-polyester type, used in engineered products such as tires, belts, hoses and pneumatic springs, which have been analyzed in each processing phase. Fiber samples were extracted after each processing phase to be analyzed, by traction destructive tests and scanning electron microscopy. The results of analysis of mechanical properties showed loss of resistance to temperature and multi axial stress during fiber processing phase. Through microscopy tests, it was possible to find contamination, surface stains, plastic deformations, scaling, variations in the fracture faces of the filaments and

  3. Structure, thermal and fracture mechanical properties of benzoxazine-modified amine-cured DGEBA epoxy resins

    Directory of Open Access Journals (Sweden)

    2011-03-01

    Full Text Available First, traditional diamine hardeners of epoxy resins (EP were checked as potential accelerators for the benzoxazine (BOX homopolymerization. It was established that the acceleration effect depends on both the type and amount of the diamine compounds. In the follow-up work amine-curable diglycidyl ether bisphenol A (DGEBA type EP was modified with BOX keeping the EP/BOX ratio constant (75/25 wt.%. The amine hardeners, added in the EP in stoichiometric amounts, were of aliphatic and aromatic nature, viz. diethylenetriamine (DETA, 4,4'-diaminodiphenyl methane (DDM, and their 1/1 mixture. The thermal, viscoelastic, flexural and fracture mechanical properties of the EP/BOX hybrids were determined and compared to those of the reference EPs. Based on dynamic-mechanical thermal analysis and atomic force microscopy the formation of co-network between EP and BOX was concluded. Homopolymerized BOX was built in the network in nanoscaled inclusions and it was associated with internal antiplasticization. Incorporation of BOX improved the charring, enhanced the flexural modulus and strength, and reduced the glass transition of the parent EP. The fracture toughness and energy were not improved by hybridization with BOX.

  4. A mechanism for the production of ultrafine particles from concrete fracture.

    Science.gov (United States)

    Jabbour, Nassib; Rohan Jayaratne, E; Johnson, Graham R; Alroe, Joel; Uhde, Erik; Salthammer, Tunga; Cravigan, Luke; Faghihi, Ehsan Majd; Kumar, Prashant; Morawska, Lidia

    2017-03-01

    While the crushing of concrete gives rise to large quantities of coarse dust, it is not widely recognized that this process also emits significant quantities of ultrafine particles. These particles impact not just the environments within construction activities but those in entire urban areas. The origin of these ultrafine particles is uncertain, as existing theories do not support their production by mechanical processes. We propose a hypothesis for this observation based on the volatilisation of materials at the concrete fracture interface. The results from this study confirm that mechanical methods can produce ultrafine particles (UFP) from concrete, and that the particles are volatile. The ultrafine mode was only observed during concrete fracture, producing particle size distributions with average count median diameters of 27, 39 and 49 nm for the three tested concrete samples. Further volatility measurements found that the particles were highly volatile, showing between 60 and 95% reduction in the volume fraction remaining by 125 °C. An analysis of the volatile fraction remaining found that different volatile material is responsible for the production of particles between the samples. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. On the estimation of the steam generator maintenance efficiency by the means of probabilistic fracture mechanics

    International Nuclear Information System (INIS)

    Cizelj, L.

    1994-10-01

    In this report, an original probabilistic model aimed to assess the efficiency of particular maintenance strategy in terms of tube failure probability is proposed. The model concentrates on axial through wall cracks in the residual stress dominated tube expansion transition zone. It is based on the recent developments in probabilistic fracture mechanics and accounts for scatter in material, geometry and crack propagation data. Special attention has been paid to model the uncertainties connected to non-destructive examination technique (e.g., measurement errors, non-detection probability). First and second order reliability methods (FORM and SORM) have been implemented to calculate the failure probabilities. This is the first time that those methods are applied to the reliability analysis of components containing stress-corrosion cracks. In order to predict the time development of the tube failure probabilities, an original linear elastic fracture mechanics based crack propagation model has been developed. It accounts for the residual and operating stresses together. Also, the model accounts for scatter in residual and operational stresses due to the random variations in tube geometry and material data. Due to the lack of reliable crack velocity vs load data, the non-destructive examination records of the crack propagation have been employed to estimate the velocities at the crack tips. (orig./GL) [de

  6. Fracture analysis of concrete gravity dam under earthquake induced ...

    African Journals Online (AJOL)

    Michael Horsfall

    Fracture analysis of concrete gravity dam under earthquake induced loads. 1. ABBAS MANSOURI;. 2 ... 1 Civil Engineering, Islamic Azad University (South Branch of Tehran)Tehran, Iran ..... parameter has on the results of numerical calculations. In this analysis ... with the help of Abaqus software (Abaqus theory manual ...

  7. Layered Manufacturing of Dental Ceramics: Fracture Mechanics, Microstructure, and Elemental Composition of Lithography-Sintered Ceramic.

    Science.gov (United States)

    Uçar, Yurdanur; Aysan Meriç, İpek; Ekren, Orhun

    2018-02-11

    To compare the fracture mechanics, microstructure, and elemental composition of lithography-based ceramic manufacturing with pressing and CAD/CAM. Disc-shaped specimens (16 mm diameter, 1.2 mm thick) were used for mechanical testing (n = 10/group). Biaxial flexural strength of three groups (In-Ceram alumina [ICA], lithography-based alumina, ZirkonZahn) were determined using the "piston on 3-ball" technique as suggested in test Standard ISO-6872. Vickers hardness test was performed. Fracture toughness was calculated using fractography. Results were statistically analyzed using Kruskal-Wallis test followed by Dunnett T3 (α = 0.05). Weibull analysis was conducted. Polished and fracture surface characterization was made using scanning electron microscope (SEM). Energy dispersive spectroscopy (EDS) was used for elemental analysis. Biaxial flexural strength of ICA, LCM alumina (LCMA), and ZirkonZahn were 147 ± 43 MPa, 490 ± 44 MPa, and 709 ± 94 MPa, respectively, and were statistically different (P ≤ 0.05). The Vickers hardness number of ICA was 850 ± 41, whereas hardness values for LCMA and ZirkonZahn were 1581 ± 144 and 1249 ± 57, respectively, and were statistically different (P ≤ 0.05). A statistically significant difference was found between fracture toughness of ICA (2 ± 0.4 MPa⋅m 1/2 ), LCMA (6.5 ± 1.5 MPa⋅m 1/2 ), and ZirkonZahn (7.7 ± 1 MPa⋅m 1/2 ) (P ≤ 0.05). Weibull modulus was highest for LCMA (m = 11.43) followed by ZirkonZahn (m = 8.16) and ICA (m = 5.21). Unlike LCMA and ZirkonZahn groups, a homogeneous microstructure was not observed for ICA. EDS results supported the SEM images. Within the limitations of this in vitro study, it can be concluded that LCM seems to be a promising technique for final ceramic object manufacturing in dental applications. Both the manufacturing method and the material used should be improved. © 2018 by the American College of Prosthodontists.

  8. Analysis of thin fractures with GPR: from theory to practice

    Science.gov (United States)

    Arosio, Diego; Zanzi, Luigi; Longoni, Laura; Papini, Monica

    2017-04-01

    Whenever we perform a GPR survey to investigate a rocky medium, being the ultimate purpose of the survey either to study the stability of a rock slope or to determine the soundness of a quarried rock block, we would like mainly to detect any fracture within the investigated medium and, possibly, to estimate the parameters of the fractures, namely thickness and filling material. In most of the practical cases, rock fracture thicknesses are very small when compared to the wavelength of the electromagnetic radiation generated by the GPR systems. In such cases, fractures are to be considered as thin beds, i.e. two interfaces whose distance is smaller than GPR resolving capability, and the reflected signal is the sum of the electromagnetic reverberation within the bed. According to this, fracture parameters are encoded in the thin bed complex response and in this work we propose a methodology based on deterministic deconvolution to process amplitude and phase information in the frequency domain to estimate fracture parameters. We first present some theoretical aspects related to thin bed response and a sensitivity analysis concerning fracture thickness and filling. Secondly, we deal with GPR datasets collected both during laboratory experiments and in the facilities of quarrying activities. In the lab tests fractures were simulated by placing materials with known electromagnetic parameters and controlled thickness in between two small marble blocks, whereas field GPR surveys were performed on bigger quarried ornamental stone blocks before they were submitted to the cutting process. We show that, with basic pre-processing and the choice of a proper deconvolving signal, results are encouraging although an ambiguity between thickness and filling estimates exists when no a-priori information is available. Results can be improved by performing CMP radar surveys that are able to provide additional information (i.e., variation of thin bed response versus offset) at the expense

  9. A demographic analysis of vertical root fractures.

    Science.gov (United States)

    Cohen, Stephen; Berman, Louis H; Blanco, Lucia; Bakland, Leif; Kim, Jay S

    2006-12-01

    Teeth with vertical root fractures (VRFs) have complete or incomplete fractures that extends through the enamel, dentin and pulp, down the long axis of the tooth. Several different variables were investigated and statistically evaluated as to their correlation with the presence of VRFs. Specifically analyzed were gender, tooth location, age, radiographic and clinical findings, bruxism, and pulpal status. The data were collected from three different endodontists, from three different geographic locations, comprising a total of 227 teeth. Although VRFs may occur in conjunction with any of the parameters investigated, only certain factors were found to occur in a significant number of cases. The results indicate that VRFs are statistically more prevalent in mandibular molars and maxillary premolars. They are associated with periradicular bone loss, pain to percussion, extensive restorations, and seem to occur more often in females and older patients. However, VRFs are not necessarily related to periapical bone loss, a widening of the periodontal ligament space, associated periodontal pockets, a sinus tract, particular pulpal status, or bruxism.

  10. The mechanics of tessellations - bioinspired strategies for fracture resistance.

    Science.gov (United States)

    Fratzl, Peter; Kolednik, Otmar; Fischer, F Dieter; Dean, Mason N

    2016-01-21

    Faced with a comparatively limited palette of minerals and organic polymers as building materials, evolution has arrived repeatedly on structural solutions that rely on clever geometric arrangements to avoid mechanical trade-offs in stiffness, strength and flexibility. In this tutorial review, we highlight the concept of tessellation, a structural motif that involves periodic soft and hard elements arranged in series and that appears in a vast array of invertebrate and vertebrate animal biomaterials. We start from basic mechanics principles on the effects of material heterogeneities in hypothetical structures, to derive common concepts from a diversity of natural examples of one-, two- and three-dimensional tilings/layerings. We show that the tessellation of a hard, continuous surface - its atomization into discrete elements connected by a softer phase - can theoretically result in maximization of material toughness, with little expense to stiffness or strength. Moreover, the arrangement of soft/flexible and hard/stiff elements into particular geometries can permit surprising functions, such as signal filtering or 'stretch and catch' responses, where the constrained flexibility of systems allows a built-in safety mechanism for ensuring that both compressive and tensile loads are managed well. Our analysis unites examples ranging from exoskeletal materials (fish scales, arthropod cuticle, turtle shell) to endoskeletal materials (bone, shark cartilage, sponge spicules) to attachment devices (mussel byssal threads), from both invertebrate and vertebrate animals, while spotlighting success and potential for bio-inspired manmade applications.

  11. Fracture mechanics of polymer mortar made with recycled raw materials

    OpenAIRE

    Jurumenha,Marco Antonio Godoy; Reis,João Marciano Laredo dos

    2010-01-01

    The aim of this work is to show that industrial residues could be used in construction applications so that production costs as well as environmental protection can be improved. The fracture properties of polymer mortar manufactured with recycled materials are investigated to evaluate the materials behaviour to crack propagation. The residues used in this work were spent sand from foundry industry as aggregate, unsaturated polyester resin from polyethylene terephthalate (PET) as matrix and po...

  12. Pseudoarthrosis following proximal humeral fractures: A possible mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Rooney, P.J.; Cockshott, W.P.

    1986-01-01

    A small series of four patients with pseudarthrosis of the proximal humeral shaft is reported. These patients all had restricted movement of the shoulder joint prior to the trauma, three as a result of rheumatoid arthritis and one due a surgical fusion of the glenohumeral joint. It is suggested that pseudarthrosis is more likely under these circumstances and that pursuit of union of the fracture in such patients may not always be necessary.

  13. FAVOR: A new fracture mechanics code for reactor pressure vessels subjected to pressurized thermal shock

    International Nuclear Information System (INIS)

    Dickson, T.L.

    1993-01-01

    This report discusses probabilistic fracture mechanics (PFM) analysis which is a major element of the comprehensive probabilistic methodology endorsed by the NRC for evaluation of the integrity of Pressurized Water Reactor (PWR) pressure vessels subjected to pressurized-thermal-shock (PTS) transients. It is anticipated that there will be an increasing need for an improved and validated PTS PFM code which is accepted by the NRC and utilities, as more plants approach the PTS screening criteria and are required to perform plant-specific analyses. The NRC funded Heavy Section Steel Technology (HSST) Program at Oak Ridge National Laboratories is currently developing the FAVOR (Fracture Analysis of Vessels: Oak Ridge) PTS PFM code, which is intended to meet this need. The FAVOR code incorporates the most important features of both OCA-P and VISA-II and contains some new capabilities such as PFM global modeling methodology, the capability to approximate the effects of thermal streaming on circumferential flaws located inside a plume region created by fluid and thermal stratification, a library of stress intensity factor influence coefficients, generated by the NQA-1 certified ABAQUS computer code, for an adequate range of two and three dimensional inside surface flaws, the flexibility to generate a variety of output reports, and user friendliness

  14. 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

  15. Fracture mechanical treatment of bridging stresses in ceramics

    International Nuclear Information System (INIS)

    Fett, T.; Munz, D.

    1993-12-01

    Failure of ceramic materials often starts from cracks which can originate at pores, inclusions or can be generated during surface treatment. Fracture occurs when the stress intensity factor of the most serious crack in a component reaches a critical value K lc , the fracture toughness of the material. In case of ideal brittle materials the fracture toughness is independent of the crack extension and, consequently, identical with the stress intensity factor K l0 necessary for the onset of stable crack growth. It is a well-known fact that failure of several ceramics is influenced by an increasing crack-growth resistance curve. Several effects are responsible for this behaviour. Crack-border interactions in the wake of the advancing crack, residual stress fields in the crack region of transformation-toughened ceramics, the generation of a micro-crack zone ahead the crack tip and crack branching. The effect of increasing crack resistance has consequences on many properties of ceramic materials. In this report the authors discuss the some aspects of R-curve behaviour as the representation by stress intensity factors or energies and the influence on the compliance using the bridging stress model. (orig.) [de

  16. Mechanical behavior and essential work of fracture of starch-based blown films

    Science.gov (United States)

    Nottez, M.; Chaki, S.; Soulestin, J.; Lacrampe, M. F.; Krawczak, P.

    2015-05-01

    A fracture mechanics approach (Essential Work of Fracture, EWF) was applied to assess the toughness of novel partly starch-grafted polyolefin blown films, compared to that of a neat polyethylene reference. Tests were performed on double-end notched samples. The digital image correlation method was used to monitor the deformation field around the notch. Regular tensile and tear tests were also carried out. The specific essential work of fracture is a characteristic which is much more sensitive to materials structural modifications than the tensile or tear properties.

  17. State of the Art Report on Fracture Mechanics (Fracture in the Creep Range). Volume 3: Appendices H - M

    International Nuclear Information System (INIS)

    Ellison, E.G.; Musicco, G.G.; Pineau, A.

    1988-01-01

    A CEC State of the Art Report on Fracture Mechanics for Fast Breeder Reactors (Fracture below the Creep Range) has recently been published by Bhandari and coworkers (1984). There has also been a compilation of Creep Crack Growth Data from Germany, France and the U.K. for 304 and 316 stainles steel by Lloyd et al (1984). The present Report provides considerably more data and analytical techniques taken from Worldwide sources on creep crack initiation and propagation. Since the subject is moving quickly there is an emphasis on the most recent work; indeed research studies as yet unpublished are also included. The total Report is in 3 volumes. Volume 3 contains the most important and up-to-date information in some detail in Appendices H to M; this provides a sound base for the Report and for future workers

  18. State of the Art Report on Fracture Mechanics (Fracture in the Creep Range). Volume 2: Appendices A - G

    International Nuclear Information System (INIS)

    Ellison, E.G.; Musicco, G.G.; Pineau, A.

    1988-01-01

    A CEC State of the Art Report on Fracture Mechanics for Fast Breeder Reactors (Fracture below the Creep Range) has recently been published by Bhandari and coworkers (1984). There has also been a compilation of Creep Crack Growth Data from Germany, France and the U.K. for 304 and 316 stainles steel by Lloyd et al (1984). The present Report provides considerably more data and analytical techniques taken from Worldwide sources on creep crack initiation and propagation. Since the subject is moving quickly there is an emphasis on the most recent work; indeed research studies as yet unpublished are also included. The total Report is in 3 volumes. Volume 2 contains the most important and up-to-date information in some detail in Appendices A to G; this provides a sound base for the Report and for future workers

  19. Intra-articualr calcaneal fractures: Computed tomographic analysis

    International Nuclear Information System (INIS)

    Rosenberg, Z.S.; Feldman, F.; Singson, R.D.

    1987-01-01

    Computed tomography (CT) analysis of 21 intra-articular calcaneal fractures categorized according to the Essex-Lopresti classification revealed the following distribution: joint depression-type 57%, comminuted type 43%, tongue-type 0%. The posterior calcaneal facet was fractured and/or depressed in 100% of the cases while the medial facet was involved in only 25% of the cases. CT proved superior to plain films by consistently demonstrating additional fracture components within each major category suggesting subclassifications which have potential prognostic value. CT allowed more expeditious handling of acutely injured patients, and improved preoperative planning, postoperative follow-up, and detailed analysis of causes for chronic residual pain. CT further identified significant soft tissue injuries such as peroneal tendon displacement which cannot be delineated on plain films. (orig.)

  20. Experimental and theoretical fracture mechanics applied to volcanic conduits and domes

    Science.gov (United States)

    Sammonds, P.; Matthews, C.; Kilburn, C.; Smith, R.; Tuffen, H.; Meredith, P.

    2008-12-01

    We present an integrated modelling and experimental approach to magma deformation and fracture, which we attempt to validate against field observations of seismicity. The importance of fracture processes in magma ascent dynamics and lava dome growth and collapse are apparent from the associated seismicity. Our laboratory experiments have shown that brittle fracture of magma can occur at high temperature and stress conditions prevalent in the shallow volcanic system. Here, we use a fracture mechanics approach to model seismicity preceding volcanic eruptions. Starting with the fracture mechanics concept of a crack in an elastic body, we model crack growth around the volcanic conduit through the processes of crack interactions, leading either to the propagation and linkage of cracks, or crack avoidance and the inhibition of crack propagation. The nature of that interaction is governed by the temperature and plasticity of the magma. We find that fracture mechanics rules can account for the style of seismicity preceding eruptions. We have derived the changes in seismic b-value predicted by the model and interpret these in terms of the style of fracturing, fluid flow and heat transport. We compare our model with results from our laboratory experiments where we have deformed lava at high temperatures under triaxial stresses. These experiments were conducted in dry and water saturated conditions at effective pressures up to 10 MPa, temperatures up to 1000°C and strain rates from 10-4 s-1 to 10-6 s-1. The behaviour of these magmas was largely brittle under these conditions. We monitored the acoustic emission emitted and calculate the change in micro-seismic b-value with deformation. These we find are in accord with volcano seismicity and our fracture mechanics model.

  1. J-integral evaluation and stability analysis in the unstable ductile fracture

    International Nuclear Information System (INIS)

    Miyoshi, Toshiro; Yoshida, Yuichiro; Shiratori, Masaki.

    1984-01-01

    Concerning unstable ductile fracture, which is an important problem on the structural stability of line pipes, nuclear reactor piping and so on, the research on fracture mechanics parameters which control the beginning of the stable growth and unstable growth of cracks attracts interest. At present, as the parameters, the T-modulus based on J-integral crack tip opening angle, crack opening angle averaged over crack developing part, plastic work coefficient and so on have been proposed. The research on the effectiveness and inter-relation of these parameters is divided into generation phase and application phase, and by these researches, it was reported that all T-modulus, CTOA and COA took almost constant values in relation to crack development, except initial transition period. In order to decide which parameter is most appropriate, the detailed analysis is required. In this study, the analysis of unstable ductile fracture of a central crack test piece and a small tensile test piece was carried out by finite element method, and the evaluation of J-integral in relation to crack development, J-integral resistance value when COA is assumed to be a constant, the form of an unstable fracture occurring point and the compliance dependence were examined. The method of analysis, the evaluation of J-integral, J-integral resistance value, unstable fracture occurring point and stability diagram are described. (Kako, I.)

  2. Mechanical and mathematical models of multi-stage horizontal fracturing strings and their application

    Directory of Open Access Journals (Sweden)

    Zhanghua Lian

    2015-03-01

    Full Text Available Multi-stage SRV fracturing in horizontal wells is a new technology developed at home and abroad in recent years to effectively develop shale gas or low-permeability reservoirs, but on the other hand makes the mechanical environment of fracturing strings more complicated at the same time. In view of this, based on the loading features of tubing strings during the multi-stage fracturing of a horizontal well, mechanical models were established for three working cases of multiple packer setting, open differential-pressure sliding sleeve, and open ball-injection sliding sleeve under a hold-down packer. Moreover, mathematical models were respectively built for the above three cases. According to the Lame formula and Von Mises stress calculation formula for the thick-walled cylinder in the theory of elastic mechanics, a mathematical model was also established to calculate the equivalent stress for tubing string safety evaluation when the fracturing string was under the combined action of inner pressure, external squeezing force and axial stress, and another mathematical model was built for the mechanical strength and safety evaluation of multi-stage fracturing strings. In addition, a practical software was developed for the mechanical safety evaluation of horizontal well multi-stage fracturing strings according to the mathematical model developed for the mechanical calculation of the multi-packer string in horizontal wells. The research results were applied and verified in a gas well of Tahe Oilfield in the Tarim Basin with excellent effects, providing a theoretical basis and a simple and reliable technical means for optimal design and safety evaluation of safe operational parameters of multi-stage fracturing strings in horizontal wells.

  3. Preliminary fracture analysis of the core pressure boundary tube for the Advanced Neutron Source Research Reactor

    International Nuclear Information System (INIS)

    Schulz, K.C.

    1995-08-01

    The outer core pressure boundary tube (CPBT) of the Advanced neutron Source (ANS) reactor being designed at Oak Ridge National Laboratory is currently specified as being composed of 6061-T6 aluminum. ASME Boiler and Pressure Vessel Code fracture analysis rules for nuclear components are based on the use of ferritic steels; the expressions, tables, charts and equations were all developed from tests and analyses conducted for ferritic steels. Because of the nature of the Code, design with thin aluminum requires analytical approaches that do not directly follow the Code. The intent of this report is to present a methodology comparable to the ASME Code for ensuring the prevention of nonductile fracture of the CPBT in the ANS reactor. 6061-T6 aluminum is known to be a relatively brittle material; the linear elastic fracture mechanics (LEFM) approach is utilized to determine allowable flaw sizes for the CPBT. A J-analysis following the procedure developed by the Electric Power Research Institute was conducted as a check; the results matched those for the LEFM analysis for the cases analyzed. Since 6061-T6 is known to embrittle when irradiated, the reduction in K Q due to irradiation is considered in the analysis. In anticipation of probable requirements regarding maximum allowable flaw size, a survey of nondestructive inspection capabilities is also presented. A discussion of probabilistic fracture mechanics approaches, principally Monte Carlo techniques, is included in this report as an introduction to what quantifying the probability of nonductile failure of the CPBT may entail

  4. Computational methods for fracture analysis of heavy-section steel technology (HSST) pressure vessel experiments

    International Nuclear Information System (INIS)

    Bass, B.R.; Bryan, R.H.; Bryson, J.W.; Merkle, J.G.

    1983-01-01

    This paper summarizes the capabilities and applications of the general-purpose and special-purpose computer programs that have been developed for use in fracture mechanics analyses of HSST pressure vessel experiments. Emphasis is placed on the OCA/USA code, which is designed for analysis of pressurized-thermal-shock (PTS) conditions, and on the ORMGEN/ADINA/ORVIRT system which is used for more general analysis. Fundamental features of these programs are discussed, along with applications to pressure vessel experiments

  5. Calculation of stress intensity factors using the UNCLE finite element system and their application in fracture mechanics

    International Nuclear Information System (INIS)

    Pearce, J.H.B.

    1978-02-01

    The behaviour of crack-like defects in loaded structures is in many cases characterised by the stress intensity factor, K, which describes the spatial distribution around the crack tip. Analytical evaluation of K for generalised loading and geometry would be extremely complex. A finite element approach is described which utilises the existing UNCLE system of the UKAEA. The interpretation of the results for a fracture mechanics analysis is briefly reviewed. (author)

  6. Two-parameter fracture mechanics: Theory and applications

    International Nuclear Information System (INIS)

    O'Dowd, N.P.; Shih, C.F.

    1993-02-01

    A family of self-similar fields provides the two parameters required to characterize the full range of high- and low-triaxiality crack tip states. The two parameters, J and Q, have distinct roles: J sets the size scale of the process zone over which large stresses and strains develop, while Q scales the near-tip stress distribution relative to a high triaxiality reference stress state. An immediate consequence of the theory is this: it is the toughness values over a range of crack tip constraint that fully characterize the material's fracture resistance. It is shown that Q provides a common scale for interpreting cleavage fracture and ductile tearing data thus allowing both failure modes to be incorporated in a single toughness locus. The evolution of Q, as plasticity progresses from small scale yielding to fully yielded conditions, has been quantified for several crack geometries and for a wide range of material strain hardening properties. An indicator of the robustness of the J-Q fields is introduced; Q as a field parameter and as a pointwise measure of stress level is discussed

  7. Thermo-hydro-mechanical simulation of a 3D fractured porous rock: preliminary study of coupled matrix-fracture hydraulics

    Energy Technology Data Exchange (ETDEWEB)

    Canamon, I.; Javier Elorza, F. [Universidad Politecnica de Madrid, Dept. de Matematica Aplicada y Metodos Informaticas, ETSI Minas (UPM) (Spain); Ababou, R. [Institut de Mecanique des Fluides de Toulouse (IMFT), 31 (France)

    2007-07-01

    We present a problem involving the modeling of coupled flow and elastic strain in a 3D fractured porous rock, which requires prior homogenization (up-scaling) of the fractured medium into an equivalent Darcian anisotropic continuum. The governing equations form a system of PDE's (Partial Differential Equations) and, depending on the case being considered, this system may involve two different types of 'couplings' (in a real system, both couplings (1) and (2) generally take place): 1) Hydraulic coupling in a single (no exchange) or in a dual matrix-fracture continuum (exchange); 2) Thermo-Hydro-Mechanical interactions between fluid flow, pressure, elastic stress, strain, and temperature. We present here a preliminary model and simulation results with FEMLAB{sup R}, for the hydraulic problem with anisotropic heterogeneous coefficients. The model is based on data collected at an instrumented granitic site (FEBEX project) for studying a hypothetical nuclear waste repository at the Grimsel Test Site in the Swiss Alps. (authors)

  8. Assessment of bone quality in the isolated femoral head for intracapsular fractures of the femoral head. Analysis of bone architecture using micro-CT and pQCT, and comparison with extracapsular fractures

    International Nuclear Information System (INIS)

    Sando, Masaru

    2003-01-01

    Block sections were prepared from the five locations, central portion, superior portion, inferior portion, anterior portion, and posterior portion, of the region around the fracture of the femoral head isolated from 21 patients (16 patients with intracapsular fracture, 5 patients with extracapsular fracture). Cancellous bone microstructure, cortical bone thickness, and bone density were evaluated and analyzed for differences in the mechanism from which intracapsular versus extracapsular fracture and fragility developed. The method of evaluating the bone architecture differed from conventional bone histomorphometry of hard tissues and involved non-invasive micro-CT measurements, while the bone density was measured by peripheral quantitative computed topography (pQCT). The results indicate that in comparison to patients with extracapsular fractures, patients with intracapsular fractures showed significant decreases in the trabecular thickness of superior and posterior portions in the cancellous bone. The cortical bone thickness was significantly decreased in the superior portion. Bone density was significantly decreased in the superior portion, while in the extracapsular fracture group density tended to be lower in the inferior, anterior, and posterior portions, although this was not statistically significant. Although there have been previous studies on the bone quality of the femoral head isolated from intracapsular fracture of the femoral head, most reports are of two-dimensional analysis of coronal sections. As far as we are aware, there have been no previous reports comparing individual locations to extracapsular fractures. In view of the various reports that bone density is lower in the extracapsular fracture compared to the intracapsular fracture, we speculate that extracapsular fracture results from the effects of external forces on decreased bone density, while in the intracapsular fracture type, thinning of the superior portion of the cortical bone creates

  9. Fatigue fracture analysis in medium carbon structural steel and austenitic stainless steel by X-ray fractography

    International Nuclear Information System (INIS)

    Rao, N.N.; Azmi bin Rahmat

    1994-01-01

    Apart from the reidual stresses present in the bulk material, a growing fatigue crack may develop its own stress field ahead of the crack tip which in turn could influence the crack propagation behaviour. A fracture surface analysis through measurement of the residual stress of a failed component may provide some additional useful information to that obtained through conventional metallurgical and fracture mechanics investigations. This method of fracture surface analysis using x-ray diffraction technique is known as X -ray Fractography . Residual stress (ρ sub γ) and the full width at half maximum (FWHM) of the x-ray diffraction profile of any reflection are determined at different crack lengths on the fracture surface. These are then corelated to the fracture toughness parameters such as fracture toughness K sub I sub C, the maximum stress intensity factor K sub max and the stress intensity factor range δK. The present investigation aims at detailed x-ray analysis of the fatigue fractured surfaces of the compact tension specimens prepared from ferritic and austenitic stainless steels. The ferritic steel has been subjected to various heat treatments to obtain different microstructures and mechanical properties. The overall observations are analyzed through fatigue (cumulative) damage and material science concepts

  10. Variate generation for probabilistic fracture mechanics and fitness-for-service studies

    International Nuclear Information System (INIS)

    Walker, J.R.

    1987-01-01

    Atomic Energy of Canada Limited is conducting studies in Probabilistic Fracture Mechanics. These studies are being conducted as part of a fitness-for-service programme in support of CANDU reactors. The Monte Carlo analyses, which form part of the Probabilistic Fracture Mechanics studies, require that variates can be sampled from probability density functions. Accurate pseudo-random numbers are necessary for accurate variate generation. This report details the principles of variate generation, and describes the production and testing of pseudo-random numbers. A new algorithm has been produced for the correct performance of the lattice test for the independence of pseudo-random numbers. Two new pseudo-random number generators have been produced. These generators have excellent randomness properties and can be made fully machine-independent. Versions, in FORTRAN, for VAX and CDC computers are given. Accurate and efficient algorithms for the generation of variates from the specialized probability density functions of Probabilistic Fracture Mechanics are given. 38 refs

  11. Fracture processes and mechanisms of crack growth resistance in human enamel

    Science.gov (United States)

    Bajaj, Devendra; Park, Saejin; Quinn, George D.; Arola, Dwayne

    2010-07-01

    Human enamel has a complex micro-structure that varies with distance from the tooth’s outer surface. But contributions from the microstructure to the fracture toughness and the mechanisms of crack growth resistance have not been explored in detail. In this investigation the apparent fracture toughness of human enamel and the mechanisms of crack growth resistance were evaluated using the indentation fracture approach and an incremental crack growth technique. Indentation cracks were introduced on polished surfaces of enamel at selected distances from the occlusal surface. In addition, an incremental crack growth approach using compact tension specimens was used to quantify the crack growth resistance as a Junction of distance from the occlusal surface. There were significant differences in the apparent toughness estimated using the two approaches, which was attributed to the active crack length and corresponding scale of the toughening mechanisms.

  12. Coupled hydrological-mechanical effects due to excavation of underground openings in unsaturated fractured rocks

    International Nuclear Information System (INIS)

    Montazer, P.

    1985-01-01

    One of the effects of excavating an underground opening in fractured rocks is a modification of the state of the stress in the rock mass in the vicinity of the opening. This effect causes changes in the geometry of the cross sections of the fracture planes, which in turn results in modification of the hydrologic properties of the fractures of the rock mass. The significance of the orientation of the fractures and their stiffness on the extent of the modification of the hydrologic properties as a result of excavation of underground openings is demonstrated. A conceptual model is presented to illustrate the complexity of the coupled hydrological-mechanical phenomena in the unsaturated zone. This conceptual model is used to develop an investigative program to assess the extent of the effect at a proposed repository site for storing high-level nuclear wastes

  13. Hydraulic and mechanical properties of natural fractures in low-permeability rock

    International Nuclear Information System (INIS)

    Pyrack-Nolte, L.J.; Myer, L.R.; Cook, N.G.W.; Witherspoon, P.A.

    1987-01-01

    The results of a comprehensive laboratory study of the mechanical displacement, permeability, and void geometry of single rock fractures in a quartz monzonite are summarized and analyzed. A metal-injection technique was developed that provided quantitative data on the precise geometry of the void spaces between the fracture surfaces and the areas of contact at different stresses. At effective stresses of less than 20 MPa fluid flow was proportional to the mean fracture aperture raised to a power greater than 3. As stress was increased, contact area was increased and void spaces become interconnected by small tortuous channels that constitute the principal impediment to fluid flow. At effective stresses higher than 20 MPa, the mean fracture aperture continued to diminish with increasing stress, but this had little effect on flow because the small tortuous flow channels deformed little with increasing stress

  14. Impact and fracture analysis of fish scales from Arapaima gigas.

    Science.gov (United States)

    Torres, F G; Malásquez, M; Troncoso, O P

    2015-06-01

    Fish scales from the Amazonian fish Arapaima gigas have been characterised to study their impact and fracture behaviour at three different environmental conditions. Scales were cut in two different directions to analyse the influence of the orientation of collagen layers. The energy absorbed during impact tests was measured for each sample and SEM images were taken after each test in order to analyse the failure mechanisms. The results showed that scales tested at cryogenic temperatures display fragile behaviour, while scales tested at room temperature did not fracture. Different failure mechanisms have been identified, analysed and compared with the failure modes that occur in bone. The impact energy obtained for fish scales was two to three times higher than the values reported for bone in the literature. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Fracture mechanics of polymer mortar made with recycled raw materials

    Directory of Open Access Journals (Sweden)

    Marco Antonio Godoy Jurumenha

    2010-12-01

    Full Text Available The aim of this work is to show that industrial residues could be used in construction applications so that production costs as well as environmental protection can be improved. The fracture properties of polymer mortar manufactured with recycled materials are investigated to evaluate the materials behaviour to crack propagation. The residues used in this work were spent sand from foundry industry as aggregate, unsaturated polyester resin from polyethylene terephthalate (PET as matrix and polyester textile fibres from garment industry, producing an unique composite material fully from recycled components with low cost. The substitution of fresh by used foundry sand and the insertions of textile fibres contribute to a less brittle behaviour of polymer mortar.

  16. The mechanical benefit of medial support screws in locking plating of proximal humerus fractures.

    Directory of Open Access Journals (Sweden)

    Wen Zhang

    Full Text Available BACKGROUND: The purpose of this study was to evaluate the biomechanical advantages of medial support screws (MSSs in the locking proximal humeral plate for treating proximal humerus fractures. METHODS: Thirty synthetic left humeri were randomly divided into 3 subgroups to establish two-part surgical neck fracture models of proximal humerus. All fractures were fixed with a locking proximal humerus plate. Group A was fixed with medial cortical support and no MSSs; Group B was fixed with 3 MSSs but without medial cortical support; Group C was fixed with neither medial cortical support nor MSSs. Axial compression, torsional stiffness, shear stiffness, and failure tests were performed. RESULTS: Constructs with medial support from cortical bone showed statistically higher axial and shear stiffness than other subgroups examined (P<0.0001. When the proximal humerus was not supported by medial cortical bone, locking plating with medial support screws exhibited higher axial and torsional stiffness than locking plating without medial support screws (P ≤ 0.0207. Specimens with medial cortical bone failed primarily by fracture of the humeral shaft or humeral head. Specimens without medial cortical bone support failed primarily by significant plate bending at the fracture site followed by humeral head collapse or humeral head fracture. CONCLUSIONS: Anatomic reduction with medial cortical support was the stiffest construct after a simulated two-part fracture. Significant biomechanical benefits of MSSs in locking plating of proximal humerus fractures were identified. The reconstruction of the medial column support for proximal humerus fractures helps to enhance mechanical stability of the humeral head and prevent implant failure.

  17. Fracture Failure Analysis of Fuel Pump Transmission Shaft of Dual-Fuel Engine

    Directory of Open Access Journals (Sweden)

    Chen Pei-hong

    2017-01-01

    Full Text Available NTS6ZLCz-129 dual-fuel turbocharged and intercooled engine durability test at 1000h, fuel pump shaft fractured. Fracture analysis, chemical analysis, microstructure examination and finite element stress analysis were carried out on the fractured shaft. The analysis result showed that the shaft fracture cause is forging fold. By improving the forging process, the forging fold was solved, and the durability test can be carried out smoothly.

  18. Fracture Mechanics Models for Brittle Failure of Bottom Rails due to Uplift in Timber Frame Shear Walls

    Directory of Open Access Journals (Sweden)

    Joergen L. Jensen

    2016-01-01

    Full Text Available In partially anchored timber frame shear walls, hold-down devices are not provided; hence the uplift forces are transferred by the fasteners of the sheathing-to-framing joints into the bottom rail and via anchor bolts from the bottom rail into the foundation. Since the force in the anchor bolts and the sheathing-to-framing joints do not act in the same vertical plane, the bottom rail is subjected to tensile stresses perpendicular to the grain and splitting of the bottom rail may occur. This paper presents simple analytical models based on fracture mechanics for the analysis of such bottom rails. An existing model is reviewed and several alternative models are derived and compared qualitatively and with experimental data. It is concluded that several of the fracture mechanics models lead to failure load predictions which seem in sufficiently good agreement with the experimental results to justify their application in practical design.

  19. Outcome analysis of retrograde nailing and less invasive stabilization system in distal femoral fractures: A retrospective analysis

    Directory of Open Access Journals (Sweden)

    Christian Hierholzer

    2011-01-01

    Full Text Available Background: Two major therapeutic principles can be employed for the treatment of distal femoral fractures: retrograde intramedullary (IM nailing (RN or less invasive stabilization on system (LISS. Both operative stabilizing systems follow the principle of biological osteosynthesis. IM nailing protects the soft-tissue envelope due to its minimally invasive approach and closed reduction techniques better than distal femoral locked plating. The purpose of this study was to evaluate and compare outcome of distal femur fracture stabilization using RN or LISS techniques. Materials and Methods: In a retrospective study from 2003 to 2008, we analyzed 115 patients with distal femur fracture who had been treated by retrograde IM nailing (59 patients or LISS plating (56 patients. In the two cohort groups, mean age was 54 years (17-89 years. Mechanism of injury was high energy impact in 57% (53% RN, 67% LISS and low-energy injury in 43% (47% RN, 33% LISS, respectively. Fractures were classified according to AO classification: there were 52 type A fractures (RN 31, LISS 21 and 63 type C fractures (RN 28, LISS 35; 32% (RN and 56% (LISS were open and 68% (RN and 44% (LISS were closed fractures, respectively. Functional and radiological outcome was assessed. Results: Clinical and radiographic evaluation demonstrated osseous healing within 6 months following RN and following LISS plating in over 90% of patients. However, no statistically significant differences were found for the parameters time to osseous healing, rate of nonunion, and postoperative complications. The following complications were treated: hematoma formation (one patient RN and three patients LISS, superficial infection (one patient RN and three patients LISS, deep infection (2 patients LISS. Additional secondary bone grafting for successful healing 3 months after the primary operation was required in four patients in the RN (7% of patients and six in the LISS group (10% of patients

  20. An Improved Rate-Transient Analysis Model of Multi-Fractured Horizontal Wells with Non-Uniform Hydraulic Fracture Properties

    Directory of Open Access Journals (Sweden)

    Youwei He

    2018-02-01

    Full Text Available Although technical advances in hydraulically fracturing and drilling enable commercial production from tight reservoirs, oil/gas recovery remains at a low level. Due to the technical and economic limitations of well-testing operations in tight reservoirs, rate-transient analysis (RTA has become a more attractive option. However, current RTA models hardly consider the effect of the non-uniform production on rate decline behaviors. In fact, PLT results demonstrate that production profile is non-uniform. To fill this gap, this paper presents an improved RTA model of multi-fractured horizontal wells (MFHWs to investigate the effects of non-uniform properties of hydraulic fractures (production of fractures, fracture half-length, number of fractures, fracture conductivity, and vertical permeability on rate transient behaviors through the diagnostic type curves. Results indicate obvious differences on the rate decline curves among the type curves of uniform properties of fractures (UPF and non-uniform properties of fractures (NPF. The use of dimensionless production integral derivative curve magnifies the differences so that we can diagnose the phenomenon of non-uniform production. Therefore, it’s significant to incorporate the effects of NPF into the RDA models of MFHWs, and the model proposed in this paper enables us to better evaluate well performance based on long-term production data.

  1. Evaluation of tensile strength and fracture toughness of yttria-stabilized zirconia polycrystals with fracture surface analysis

    International Nuclear Information System (INIS)

    Oishi, Manabu; Matsuda, Yukihisa; Noguchi, Kenichi; Masaki, Takaki

    1995-01-01

    The tensile strength of yttria-stabilized tetragonal zirconia polycrystals (Y-TZPs) was measured and the fracture surfaces were analyzed with the scanning electron microscope and X-ray microanalyzer. The fracture origins of the pressureless-sintered samples were voids or inclusions such as Al 2 O 3 , Al 2 O 3 with SiO 2 , and cubic-ZrO 2 , while the fracture origins of the hot isostatically pressed samples were inclusions; no voids were detected at fracture origins. The higher strengths of the hot isostatically pressed samples versus those of the pressureless-sintered samples were consistent with the change in fracture origins. The fracture toughness of the samples calculate from the tensile strength and analysis of the fracture origins was 3.4 to 3.7 MPa ·√m. These values are lower than those measured with the SEPB method. These discrepancies might be caused by the difference in the state of the fracture origin and its neighborhood, such as the size of the fracture origin and interaction between two surfaces in the precrack

  2. Computational simulation for creep fracture properties taking microscopic mechanism into account

    International Nuclear Information System (INIS)

    Tabuchi, Masaaki

    2003-01-01

    Relationship between creep crack growth rate and microscopic fracture mechanism i.e., wedge-type intergranular, transgranular and cavity-type intergranular crack growth, has been investigated. The growth rate of wedge-type and transgranular creep crack could be characterized by creep ductility. Creep damages formed ahead of the cavity-type crack tip accelerated the crack growth rate. Based on the experimental results, FEM code that simulates creep crack growth has been developed by taking the fracture mechanism into account. The effect of creep ductility and void formation ahead of the crack tip on creep crack growth behavior could be simulated. (author)

  3. Proceedings of the 20th meeting of the working group on fracture mechanisms

    International Nuclear Information System (INIS)

    1988-01-01

    This volume contains 41 contributions presented at the 20th meeting of the working group on fracture mechanisms. The contributions dealt with the following topics: 1.) mechanical and test fundamentals of crack initiating corrosion processes; 2.) crack formation in water and seawater; 3.) crack formation in the process industry; 4.) hydrogen-induced crack formation; 5.) stress and crack corrosion of rustproof cast alloys; 6.) corrosion-induced crack formation at high temperatures; 7.) experimental and numerical studies on fracture behaviour. 30 contributions were separately integrated in the data base 'ENERGY'. (MM) [de

  4. Combining NDE and fracture mechanics by artifical intelligence expert systems techniques

    International Nuclear Information System (INIS)

    Mucciardi, A.N.; Riccardella, P.C.

    1986-01-01

    This paper reports on the development of a PC-based expert system for non-destructive evaluation. Software tools from the expert systems subfield of artificial intelligence are being used to combine both NDE and fracture mechanics algorithms into one, unified package. The system incorporates elements of computer-enhanced ultrasonic signal processing, featuring artificial intelligence learning capability, state-of-the-art fracture mechanics analytical tools, and all relevant metallurgical and design data necessary to emulate the decisions of the panel(s) of experts typically involved in generating and dispositioning NDE data

  5. Investigation on fracture behavior and mechanisms of DGEBF toughened by CTBN

    Science.gov (United States)

    Wang, Lulu; Tan, Yefa; Wang, Haitao; Gao, Li; Xiao, Chufan

    2018-05-01

    Carboxyl-terminated butadiene-co-acrylonitrile (CTBN) was used as the toughener to improve the mechanical performance and fracture toughness of diglycidyl ether of bisphenol F (DGEBF) by prereacted approach. The results show that the chemical bonding interface was formed between DGEBF and CTBN particles in the prepolymerization reaction process, which remarkably enhances the fracture toughness of the composites. Based on the qualitative and quantitative analyses, it shows the main toughening mechanisms are the plastic shear banding effect resulted from the plastic deformation of the EP matrix and the plastic void expansion because of the debonding of CTBN particles from the EP matrix.

  6. Validation of a fracture mechanics approach to nuclear transportation cask design through a drop test program

    International Nuclear Information System (INIS)

    Sorenson, K.B.

    1986-01-01

    Sandia National Laboratories (SNL), under contract to the Department of Energy, is conducting a research program to develop and validate a fracture mechanics approach to cask design. A series of drop tests of a transportation cask is planned for the summer of 1986 as the method for benchmarking and, thereby, validating the fracture mechanics approach. This paper presents the drop test plan and background leading to the development of the test plan including structural analyses, material characterization, and non-destructive evaluation (NDE) techniques necessary for defining the test plan properly

  7. An Overview of Innovative Strategies for Fracture Mechanics at NASA Langley Research Center

    Science.gov (United States)

    Ransom, Jonathan B.; Glaessgen, Edward H.; Ratcliffe, James G.

    2010-01-01

    Engineering fracture mechanics has played a vital role in the development and certification of virtually every aerospace vehicle that has been developed since the mid-20th century. NASA Langley Research Center s Durability, Damage Tolerance and Reliability Branch has contributed to the development and implementation of many fracture mechanics methods aimed at predicting and characterizing damage in both metallic and composite materials. This paper presents a selection of computational, analytical and experimental strategies that have been developed by the branch for assessing damage growth under monotonic and cyclic loading and for characterizing the damage tolerance of aerospace structures

  8. 3-D Experimental Fracture Analysis at High Temperature

    Energy Technology Data Exchange (ETDEWEB)

    John H. Jackson; Albert S. Kobayashi

    2001-09-14

    T*e, which is an elastic-plastic fracture parameter based on incremental theory of plasticity, was determined numerically and experimentally. The T*e integral of a tunneling crack in 2024-T3 aluminum, three point bend specimen was obtained through a hybrid analysis of moire interferometry and 3-D elastic-plastic finite element analysis. The results were verified by the good agreement between the experimentally and numerically determined T*e on the specimen surface.

  9. Fracture mechanics of thin wall cylindrical pressure vessels: an interim review

    International Nuclear Information System (INIS)

    Kurtz, R.J.; Olson, N.J.

    1977-08-01

    The report is a result of activities in the LMFBR Fuel Rod Transient Performance Program sponsored by the LMFBR Branch of the Division of Project Management, U.S. Nuclear Regulatory Commission. One of the objectives is to develop predictions relative to the length, direction, and rate of growth of cladding rips subsequent to (or concurrent with) the initial cladding breach during unprotected transients. To provide a basis for evaluation, Battelle, Pacific Northwest Laboratories has reviewed most available fracture mechanics assessments relative to thin-wall cylindrical pressure vessels. The purpose of the report is to review the various fracture mechanics models and to describe the pertinent fracture parameters. It is intended to provide a formal basis for assessing future analytical predictions of fracture behavior of materials exposed to transient LMFBR thermal and mechanical loading conditions. In addition, the report is expected to provide reference material for evaluating or developing experimental programs required to properly address the problem of predicting fracture behavior of materials during transient events

  10. Crack-jump mechanism of microvein formation and its implications for stress cyclicity during extension fracturing

    Science.gov (United States)

    Caputo, Riccardo; Hancock, Paul L.

    1998-11-01

    It is well accepted and documented that faulting is produced by the cyclic behaviour of a stress field. Some extension fractures, such as veins characterised by the crack-seal mechanism, have also been presumed to result from repeated stress cycles. In the present note, some commonly observed field phenomena and relationships such as hackle marks and vein and joint spacing, are employed to argue that a stress field can also display cyclic behaviour during extensional fracturing. Indeed, the requirement of critical stress conditions for the occurrence of extensional failure events does not accord with the presence of contemporaneously open nearby parallel fractures. Therefore, because after each fracture event there is stress release within the surrounding volume of rock, high density sets of parallel extensional fractures also strongly support the idea that rocks undergo stress cyclicity during jointing and veining. A comparison with seismological data from earthquakes with dipole mechanical solutions, confirms that this process presently occurs at depth in the Earth crust. Furthermore, in order to explain dense sets of hair-like closely spaced microveins, a crack-jump mechanism is introduced here as an alternative to the crack-seal mechanism. We also propose that as a consequence of medium-scale stress cyclicity during brittle deformation, the re-fracturing of a rock mass occurs in either one or the other of these two possible ways depending on the ratio between the elastic parameters of the sealing material and those of the host rock. The crack-jump mechanism occurs when the former is stronger.

  11. [Association between hip fractures and risk factors for osteoporosis. Multivariate analysis].

    Science.gov (United States)

    Masoni, Ana; Morosano, Mario; Tomat, María Florencia; Pezzotto, Stella M; Sánchez, Ariel

    2007-01-01

    In this observational, case-control study, 376 inpatients were evaluated in order to determine the association of risk factors (RF) and hip fracture; 151 patients had osteoporotic hip fracture (cases); the remaining were controls. Data were obtained from medical charts, and through a standardized questionnaire about RF. Mean age of the sample (+/- SD) was 80.6 +/- 8.1 years, without statistically significant difference between cases and controls; the female:male ratio was 3:1 in both groups. Fractured women were older than men (82.5 +/- 8.1 vs. 79.7 +/- 7.2 years, respectively; p household duties was a RF (p = 0.007), which was absent in males. In multivariate analysis, the following RF were significantly more frequent: Cognitive impairment (p = 0.001), and previous falls (p < 0.0001); whereas the following protective factors were significantly different from controls: Calcium intake during youth (p < 0.0001), current calcium intake (p < 0.0001), and mechanical aid for walking (p < 0.0001). Evaluation of RF and protective factors may contribute to diminish the probability of hip fracture, through a modification of personal habits, and measures to prevent falls among elderly adults. Present information can help to develop local and national population-based strategies to diminish the burden of hip fractures for the health system.

  12. Analysis of fracture surface of CFRP material by three-dimensional reconstruction methods

    International Nuclear Information System (INIS)

    Lobo, Raquel M.; Andrade, Arnaldo H.P.

    2009-01-01

    Fracture surfaces of CFRP (carbon Fiber Reinforced Polymer) materials, used in the nuclear fuel cycle, presents an elevated roughness, mainly due to the fracture mode known as pulling out, that displays pieces of carbon fibers after debonding between fiber and matrix. The fractographic analysis, by bi-dimensional images is deficient for not considering the so important vertical resolution as much as the horizontal resolution. In this case, the knowledge of this heights distribution that occurs during the breaking, can lead to the calculation of the involved energies in the process that would allows a better agreement on the fracture mechanisms of the composite material. An important solution for the material characterization, whose surface presents a high roughness due to the variation in height, is to reconstruct three-dimensionally these fracture surfaces. In this work, the 3D reconstruction was done by two different methods: the variable focus reconstruction, through a stack of images obtained by optical microscopy (OM) and the parallax reconstruction, carried through with images acquired by scanning electron microscopy (SEM). The results of both methods present an elevation map of the reconstructed image that determine the height of the surface pixel by pixel,. The results obtained by the methods of reconstruction for the CFRP surfaces, have been compared with others materials such as aluminum and copper that present a ductile type fracture surface, with lower roughness. (author)

  13. Analysis of Fracture Behaviour of Multilayer Pipes

    Czech Academy of Sciences Publication Activity Database

    Nezbedová, E.; Knésl, Zdeněk; Vlach, B.

    2007-01-01

    Roč. 36, č. 5 (2007), s. 207-212 ISSN 1465-8011. [Plastic Pipes /13./. Washington, D. C., 02.10.2006-05.10.2006] R&D Projects: GA ČR GA106/07/1284 Institutional research plan: CEZ:AV0Z20410507 Keywords : multi-layer pipes Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.431, year: 2007

  14. Fracture mechanics evaluation for the cast duplex stainless steel after thermal aging

    Energy Technology Data Exchange (ETDEWEB)

    Urata, Shigeru [Kansai Electric Power Co., Inc., Osaka (Japan)

    1998-12-31

    For the primary coolant piping of PWRs in Japan, cast duplex stainless steel which is excellent in terms of strength, corrosion resistance, and weldability has conventionally been used. The cast duplex stainless steel contains the ferrite phase in the austenite matrix and thermal aging after long term service is known to change its material characteristics. It is considered appropriate to apply the methodology of elastic plastic fracture mechanics for an evaluation of the integrity of the primary coolant piping after thermal aging. Therefore, we evaluated the integrity of the primary coolant piping for an initial PWR plant in Japan by means of elastic plastic fracture mechanics. The evaluation results show that the crack will not grow into an unstable fracture and the integrity of the piping will be secured, even when such through wall crack length is assumed to equal the fatigue crack growth length for a service period of up to 60 years. (author)

  15. Ultra high vacuum fracture and transfer device for AES analysis of irradiated austenitic stainless steel

    International Nuclear Information System (INIS)

    Urie, M.W.; Panayotou, N.F.; Robinson, J.E.

    1980-01-01

    An ultrahigh vacuum fracture and transfer device for analysis of irradiated and non-irradiated SS 316 fuel cladding is described. Mechanical property tests used to study the behavior of cladding during reactor transient over-power conditions are reported. The stress vs temperature curves show minimal differences between unirradiated cladding and unfueled cladding. The fueled cladding fails at a lower temperature. All fueled specimens failed in an intergranular mode

  16. Development of ductile cast iron for spent fuel cask applications using fracture mechanics principles

    International Nuclear Information System (INIS)

    Ray, K.K.; Tiwari, S.; Hemlata Kumari; Mamta Kumari; Kumar, Hemant; Albert, S.K.; Bhaduri, A.K.

    2016-01-01

    The structure-property relations of ductile cast irons (DCIs) with varying Cu content and ~1 wt.% Ni has been investigated with an emphasis on examining their fracture toughness property towards the development of suitable materials for large volume containers for transport of spent fuel. The detailed microstructural characteristics, hardness, tensile and fracture toughness properties of three DCIs were assessed in as-cast and annealed conditions. Fracture toughness values were determined using both ball indentation (K BI ) and J-integral (KJ Ic ) test. The obtained results assist to infer that: (i) the amount of pearlite and nodule count increases with increased amount of Cu, (ii) the hardness and strength values increases whereas fracture toughness values marginally decreases with increased Cu content, and (iii) the magnitudes of K BI estimated using a proposed analysis are in good agreement with KJ Ic values for the as-cast materials. (author)

  17. FAVOR: A new fracture mechanics code for reactor pressure vessels subjected to pressurized thermal shock

    International Nuclear Information System (INIS)

    Dickson, T.L.

    1993-01-01

    Probabilistic fracture mechanics (PFM) analysis is a major element of the comprehensive probabilistic methodology endorsed by the Nuclear Regulatory Commission (NRC) for evaluation of the integrity of pressurized water reactor pressure vessels subjected to pressurized-thermal-shock (PTS) transients. OCA-P and VISA-II are PTS PFM computer codes that are currently referenced in Regulatory Guide 1.154 as acceptable codes for performing plant-specific analyses. These codes perform PFM analyses to estimate the increase in vessel failure probability as the vessel accumulates radiation damage over the operating life of the vessel. Experience with the application of these codes in the last few years has provided insights into areas where they could be improved. As more plants approach the PTS screening criteria and are required to perform plant-specific analyses, there will be an increasing need for an improved and validated PTS PFM code that is accepted by the NRC and utilities. The NRC funded Heavy Section Steel Technology Program (HSST) at the Oak Ridge National Laboratory is currently developing the FAVOR (Fracture Analysis of Vessels: Oak Ridge) code, which is expected to meet this need. The FAVOR code incorporates the most important features of both OCA-P and VISA-II and contains some new capabilities such as (1) a PFM global modeling methodology; (2) the calculation of the axial stress component associated with coolant streaming beneath an inlet nozzle; (3) a library of stress intensity factor influence coefficients, generated by the NQA-1 certified ABAQUS computer code, for an appropriate range of two and three dimensional inner-surface flaws; (4) the flexibility to generate a variety of output reports; and (5) enhanced user friendliness

  18. Microscale fracture mechanisms of a Cr{sub 3}C{sub 2}-NiCr HVOF coating

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, Andrew L., E-mail: Andrew.robertson99987@gmail.com; White, Ken W.

    2017-03-14

    Thermal spray coatings, often composed of heterogeneous, multiphase microstructures, may, consequently, exhibit complex fracture behavior. For such coating structures, conventional mechanical evaluation methods fail to isolate the contribution of microstructural features to the overall fracture behavior. For this reason, this study employed focused ion beam machined (FIB) microcantilever beams and FIB sectioning methods to study the fracture mechanisms important at the scale of the heterogeneous Cr{sub 3}C{sub 2}-NiCr thermal spray coating. We found three fracture modes, namely, intergranular matrix fracture, matrix/carbide interfacial fracture, and carbide cleavage. By comparison, microindentation-induced cracks, the frequency of crack deflection around carbides is significantly more prevalent at this much larger crack dimension. This mechanistic variation provides some insight into the specific role and limitations of the microcantilever beam technique for fracture characterization of composite microstructures.

  19. Effects of fibre content on mechanical properties and fracture ...

    Indian Academy of Sciences (India)

    Administrator

    cost. The most important factors that affect the short fibres reinforcement are ... made with conventional techniques, including single or twin screw extruding (Li et al 2005), wet ball-milling mixing (Song et al 2002) and high-speed mechanical.

  20. Fracture Analysis of the FAA/NASA Wide Stiffened Panels

    Science.gov (United States)

    Seshadri, B. R.; Newman, J. C., Jr.; Dawicke, D. S.; Young, R. D.

    1999-01-01

    This paper presents the fracture analyses conducted on the FAA/NASA stiffened and unstiffened panels using the STAGS (STructural Analysis of General Shells) code with the critical crack-tip-opening angle (CTOA) fracture criterion. The STAGS code with the "plane-strain" core option was used in all analyses. Previous analyses of wide, flat panels have shown that the high-constraint conditions around a crack front, like plane strain, has to be modeled in order for the critical CTOA fracture criterion to predict wide panel failures from small laboratory tests. In the present study, the critical CTOA value was determined from a wide (unstiffened) panel with anti-buckling guides. The plane-strain core size was estimated from previous fracture analyses and was equal to about the sheet thickness. Rivet flexibility and stiffener failure was based on methods and criteria, like that currently used in industry. STAGS and the CTOA criterion were used to predict load-against-crack extension for the wide panels with a single crack and multiple-site damage cracking at many adjacent rivet holes. Analyses were able to predict stable crack growth and residual strength within a few percent (5%) of stiffened panel tests results but over predicted the buckling failure load on an unstiffened panel with a single crack by 10%.

  1. Analysis of fluid flow and solute transport though a single fracture intersecting a canister: comparison between fractal and Gaussian fractures

    International Nuclear Information System (INIS)

    Liu, L.; Neretnieks, I.

    2005-01-01

    Full text of publication follows: Canisters with spent fuel will be deposited in fractured crystalline rock in the Swedish concept for a final repository. The fractures intersect the canister holes at different angles and they have variable apertures and therefore locally varying flowrates. Our previous model with fractures with a constant aperture and a 90 deg. intersection angle is now extended to arbitrary intersection angles and stochastically variable apertures. It is shown the previous basic model can be simply amended to account for these effects. The mean and the standard deviation of the water flowrate in the fractures are obtained from the statistics of the aperture variations by a simple formula. Likewise, the statistical form of distribution of the so-called 'equivalent flowrate', which describes the mass transfer of solutes between the canister and the flowing water, is also obtained by a simple relation. These simple statistical relations obviate the need to simulate each fracture that intersects a canister in great detail. The water flowrate and the equivalent flowrate of a fracture are instead taken from the simple distributions presented in this work. This allows the use of complex fractures also in very large fracture network models used in performance assessment. The distributions have been obtained by generating a multitude of fractures and by studying their flow and transport properties. Fractal as well as Gaussian aperture distributions have been studied. It has been found that the distributions of the volumetric and the equivalent flow rates are all close to the Normal for both types of fractures, with the mean of the distribution of the volumetric flow rate being determined solely by the hydraulic aperture, and that of the equivalent flow rate being determined by the mechanical aperture. Moreover, the standard deviation of the volumetric flow rates of the many realizations increases with increasing roughness and spatial correlation length of

  2. Correction of fatigue parameters of concrete using approximation of mechanical-Fracture parameters in time

    Czech Academy of Sciences Publication Activity Database

    Šimonová, H.; Keršner, Z.; Seitl, Stanislav; Pryl, D.; Pukl, R.

    -, č. 1 (2012), s. 57-59 ISSN 1213-3116 R&D Projects: GA ČR(CZ) GAP104/11/0833 Institutional support: RVO:68081723 Keywords : fatigue * concrete * correction * fracture parameters Subject RIV: JL - Materials Fatigue, Friction Mechanics

  3. Applications and limits of application of fracture mechanics methods in assessing the safety of components

    International Nuclear Information System (INIS)

    Stahlberg, R.

    1977-01-01

    On the basis of fracture mechanics calculations and experimental investigations, it is shown how cracks of different shape and location behave under given static and cyclic loads. In particular, component safety with regard to spontaneous failure and crack growth behaviour in different components are discussed. [de

  4. The relationship of microstructure and temperature to fracture mechanics parameters in reaction bonded silicon nitride

    International Nuclear Information System (INIS)

    Jennings, H.M.; Dalgleish, B.J.; Pratt, P.L.

    1978-01-01

    The development of physical properties in reaction bonded silicon nitride has been investigated over a range of temperatures and correlated with microstructure. Fracture mechanics parameters, elastic moduli, strength and critical defect size have been determined. The nitrided microstructure is shown to be directly related to these observed properties and these basic relationships can be used to produce material with improved properties. (orig.) [de

  5. Analysis of Fractured Teeth Utilizing Digital Microscopy: A Pilot Study

    Science.gov (United States)

    2016-06-01

    pathology (8). Artifacts such as beam hardening, streaking and cupping may limit the clinician’s ability to detect fractures (9). Metallic structures...visualization of a pathologic condition in the area of diagnostic interest (9). There have been multiple studies published which measure the size of...Heimel P, Metscher B. Volume analysis of heat-induced cracks in human molars: A preliminary study. J Forensic Dent Sci 2014;6:139-44. 13. Hunter J

  6. Fracture Analysis of Functionally Graded Materials

    International Nuclear Information System (INIS)

    Zhang, Ch.; Gao, X. W.; Sladek, J.; Sladek, V.

    2010-01-01

    This paper reports our recent research works on crack analysis in continuously non-homogeneous and linear elastic functionally graded materials. A meshless boundary element method is developed for this purpose. Numerical examples are presented and discussed to demonstrate the efficiency and the accuracy of the present numerical method, and to show the effects of the material gradation on the crack-opening-displacements and the stress intensity factors.

  7. Elastic, plastic, fracture analysis of masonry arches: A multi-span bridge case study

    Science.gov (United States)

    Lacidogna, Giuseppe; Accornero, Federico

    2018-01-01

    In this work a comparison is presented between elastic, plastic, and fracture analysis of the monumental arch bridge of Porta Napoli, Taranto (Italy). By means of a FEM model and applying the Mery's Method, the behavior of the curved structure under service loads is verified, while considering the Safe Theorem approach byHeyman, the ultimate carrying capacity of the structure is investigated. Moreover, by using Fracture Mechanics concepts, the damage process which takes place when the conditions assessed through linear elastic analysis are no longer valid, and before the set-in of the conditions established by means of the plastic limit analysis, is numerically analyzed. The study of these transitions returns an accurate and effective whole service life assessment of the Porta Napoli masonry arch bridge.

  8. NDE and fracture mechanics evaluation of bottom-head weld indications in a BWR reactor pressure vessel

    Energy Technology Data Exchange (ETDEWEB)

    Brickstad, B [Swedish Plant Inspectorate, Stockholm (Sweden)

    1988-12-31

    This document deals with the Non Destructive Examination (NDE) and the fracture mechanics evaluation of bottom head welds in a BWR. The NDE equipment is presented, together with the geometry of evaluated flaw regions. After the fracture mechanics evaluation, it appeared that the plant results fulfilled the usual conditions, and the plant was allowed to operate one more year. (TEC).

  9. High-temperature mechanical properties and fracture mechanisms of Al–Si piston alloy reinforced with in situ TiB{sub 2} particles

    Energy Technology Data Exchange (ETDEWEB)

    Han, Gang [School of Mechanical Engineering, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing 100081 (China); Zhang, Weizheng, E-mail: zhangwz@bit.edu.cn [School of Mechanical Engineering, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing 100081 (China); Zhang, Guohua; Feng, Zengjian; Wang, Yanjun [Shandong Binzhou Bohai Piston Co., Ltd., Binzhou 256602 (China)

    2015-05-01

    In order to assess the high-temperature performance of aluminum–silicon alloy reinforced with titanium diboride particles as potential piston material, the tensile behaviors and fracture mechanisms of in situ 4 wt% TiB{sub 2}/Al–Si composite were investigated in the temperature range 25–350 °C. The tensile results revealed that the composite exhibited higher modulus than the matrix alloy at all testing temperatures, but both the matrix alloy and the composite presented similar strength levels above 200 °C. The ductility of the composite was found to be lower than that of the unreinforced matrix alloy at 25 and 200 °C, but no obvious distinction was observed at 350 °C. The effects of temperature and the presence of TiB{sub 2} particles on tensile properties of the composite had been evaluated. Fractographic morphology studies were done using scanning electron microscope, which indicated that the fracture of the composite altered from brittle to ductile mode with temperature increasing. At 25 and 200 °C, fracture was dominated by cracked silicon particles and separated TiB{sub 2} particles, while decohesion at particle–matrix interface was prevalent at 350 °C. Analysis of the fracture surfaces also showed that regions of clustered TiB{sub 2} particles were found to be the locations prone to damage in the composite at both room and high temperatures.

  10. Potential effect of fracture technology on IPTS [Integrated Pressurized Thermal Shock] analysis (Fracture toughness: Kla and Klc and warm prestressing)

    International Nuclear Information System (INIS)

    Dickson, T.L.

    1990-01-01

    A major nuclear plant life extension issue to be confronted in the 1990's is pressure vessel integrity for the pressurized thermal shock (PTS) loading condition. Governing criteria associated with PTS are included in ''The PTS Rule'' (10 CFR 50.61) and Regulatory Guide 1.154: Format and Content of Plant-Specific Pressurized Thermal Shock Safety Analysis Reports for Pressurized Water Reactors. The results of the Integrated Pressurized Water Reactors. The results of the Integrated Pressurized Thermal Shock (IPTS) Program, along with risk assessments and fracture analyses performed by the NRC and reactor system vendors, contributed to the derivation of the PTS Rule. Over the last several years, the Heavy Section Steel Technology (HSST) Program at the Oak Ridge National Laboratory (ORNL) has performed a series of large-scale fracture-mechanics experiments. The Thermal Shock Experiments (TSE), Pressurized Thermal Shock Experiments (PTSE), and Wide Plate Experiments (WPE) produced K IC and K Ia data that suggest increased mean K IC and K Ia curves relative to the ones used in the IPTS study. Also, the PTSE and WPE have demonstrated that prototypical nuclear reactor pressure vessel steels are capable of arresting a propagating crack at K I values considerably above 220 MPa√m, the implicit limit of the ASME Code and the limit used in the IPTS studies. This document provides a discussion of the results of these experiments

  11. Mechanism and patterns of cervical spine fractures-dislocations in vertebral artery injury

    Directory of Open Access Journals (Sweden)

    Pankaj Gupta

    2012-01-01

    Full Text Available Purpose: To identify the fracture patterns and mechanism of injury, based on subaxial cervical spine injury classification system (SLIC, on non-contrast computed tomography (NCCT of cervical spine predictive of vertebral artery injury (VAI. Patients and Methods: We retrospectively analyzed cervical spine magnetic resonance imaging (MRI of 320 patients who were admitted with cervical spine injury in our level I regional trauma center over a period of two years (April 2010 to April 2012. Diagnosis of VAI was based on hyperintensity replacing the flow void on a T2-weighted axial image. NCCT images of the selected 43 patients with MRI diagnosis of VAI were then assessed for the pattern of injury. The cervical spinal injuries were classified into those involving the C1 and C2 and subaxial spine. For the latter, SLIC was used. Results: A total of 47 VAI were analyzed in 43 patients. Only one patient with VAI on MRI had no detectable abnormality on NCCT. C1 and C2 injuries were found in one and six patients respectively. In subaxial injuries, the most common mechanism of injury was distraction (37.5% with facet dislocation with or without fracture representing the most common pattern of injury (55%. C5 was the single most common affected vertebral level. Extension to foramen transversarium was present in 20 (42.5% cases. Conclusion: CT represents a robust screening tool for patients with VAI. VAI should be suspected in patients with facet dislocation with or without fractures, foramina transversarium fractures and C1-C3 fractures, especially type III odontoid fractures and distraction mechanism of injury.

  12. Non-linear finite element analyses of wide plate fracture mechanics experiments

    International Nuclear Information System (INIS)

    Harrop, L.P.; Gibson, S.

    1988-06-01

    A series of centre-cracked, wide plate fracture mechanics tests is being conducted with plates made from 0.36% carbon steel. This report gives an account of post-test finite element analyses performed to compare with the results of one of these tests (designated CSTP4) and a pre-test analysis of the next test which has a slightly different geometry (CSTP5). The plates are relatively thick (75mm) and have a width of 1.62m. The finite element analyses use a two-dimensional plane stress mesh. The work shows good agreement between the post-test analysis results and the overall experimental results for CSTP4. It is not expected that the analysis results will be accurate within the dimensions of the process zone ahead of the crack tip; the mesh is not sufficient for this. A vital ingredient in attaining the good overall agreement is the representation of the actual stress-strain curve of the material. The predicted response of test CSTP5 is markedly different from that of CSTP4 even though the only change is the increase in the height of the plate. In particular the shape and size of the plastic zone ahead of the crack tip is quite different in the two tests at the same nominal remote applied load. (author)

  13. Interlocking Friction Governs the Mechanical Fracture of Bilayer MoS2.

    Science.gov (United States)

    Jung, Gang Seob; Wang, Shanshan; Qin, Zhao; Martin-Martinez, Francisco J; Warner, Jamie H; Buehler, Markus J

    2018-04-24

    A molybdenum disulfide (MoS 2 ) layered system is a two-dimensional (2D) material, which is expected to provide the next generation of electronic devices together with graphene and other 2D materials. Due to its significance for future electronics applications, gaining a deep insight into the fundamental mechanisms upon MoS 2 fracture is crucial to prevent mechanical failure toward reliable applications. Here, we report direct experimental observation and atomic modeling of the complex failure behaviors of bilayer MoS 2 originating from highly variable interlayer frictions, elucidated with in situ transmission electron microscopy and large-scale reactive molecular dynamics simulations. Our results provide a systematic understanding of the effects that different stacking and loading conditions have on the failure mechanisms and crack-tip behaviors in the bilayer MoS 2 systems. Our findings unveil essential properties in fracture of this 2D material and provide mechanistic insight into its mechanical failure.

  14. Tissue-Level Mechanical Properties of Bone Contributing to Fracture Risk.

    Science.gov (United States)

    Nyman, Jeffry S; Granke, Mathilde; Singleton, Robert C; Pharr, George M

    2016-08-01

    Tissue-level mechanical properties characterize mechanical behavior independently of microscopic porosity. Specifically, quasi-static nanoindentation provides measurements of modulus (stiffness) and hardness (resistance to yielding) of tissue at the length scale of the lamella, while dynamic nanoindentation assesses time-dependent behavior in the form of storage modulus (stiffness), loss modulus (dampening), and loss factor (ratio of the two). While these properties are useful in establishing how a gene, signaling pathway, or disease of interest affects bone tissue, they generally do not vary with aging after skeletal maturation or with osteoporosis. Heterogeneity in tissue-level mechanical properties or in compositional properties may contribute to fracture risk, but a consensus on whether the contribution is negative or positive has not emerged. In vivo indentation of bone tissue is now possible, and the mechanical resistance to microindentation has the potential for improving fracture risk assessment, though determinants are currently unknown.

  15. Analysis of the flow property of aluminum alloy AA6016 based on the fracture morphology using the hydroforming technology

    Science.gov (United States)

    Lang, Lihui; Zhang, Quanda; Sun, Zhiying; Wang, Yao

    2017-09-01

    In this paper, the hydraulic bulging experiments were respectively carried out using AA6016-T4 aluminum alloy and AA6016-O aluminum alloy, and the deformation properties and fracture mechanism of aluminum alloy under the conditions of thermal and hydraulic were analyzed. Firstly, the aluminum alloy AA6016 was dealt with two kinds of heat treatment systems such as solid solution heat treatment adding natural ageing and full annealing, then the aluminum alloy such as AA6016-T4 and AA6016-O were obtained. In the same working environment, the two kinds of materials were used in the process of hydraulic bulging experiments, according to the observation and measurement of the deformation sizes of grid circles and material thicknesses near the fracture region, the flow properties and development trend of fracture defect of the materials were analyzed comprehensively from the perspective of qualitative analysis and quantitative analysis; Secondly, the two kinds of materials were sampled in different regions of the fracture area and the microstructure morphology of the fracture was observed by the scanning electron microscope (SEM). The influence laws of the heat treatment systems on the fracture defect of the aluminum alloy under the condition of the liquid pressure were studied preliminarily by observing the distribution characteristics of the fracture microstructure morphology of dimple. At the same time, the experimental research on the ordinary stamping forming process of AA6016-O was carried out and the influence law of different forming process on the fracture defect of the aluminum alloy material was studied by observing the distribution of the fracture microstructure morphology; Finally, the development process of the fracture defect of aluminum alloy sheet was described theoretically from the view of the stress state.

  16. Probabilistic Fracture Mechanics of Reactor Pressure Vessels with Populations of Flaws

    Energy Technology Data Exchange (ETDEWEB)

    Spencer, Benjamin [Idaho National Lab. (INL), Idaho Falls, ID (United States); Backman, Marie [Univ. of Tennessee, Knoxville, TN (United States); Williams, Paul [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hoffman, William [Idaho National Lab. (INL), Idaho Falls, ID (United States); Alfonsi, Andrea [Idaho National Lab. (INL), Idaho Falls, ID (United States); Dickson, Terry [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Bass, B. Richard [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Klasky, Hilda [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-09-01

    This report documents recent progress in developing a tool that uses the Grizzly and RAVEN codes to perform probabilistic fracture mechanics analyses of reactor pressure vessels in light water reactor nuclear power plants. The Grizzly code is being developed with the goal of creating a general tool that can be applied to study a variety of degradation mechanisms in nuclear power plant components. Because of the central role of the reactor pressure vessel (RPV) in a nuclear power plant, particular emphasis is being placed on developing capabilities to model fracture in embrittled RPVs to aid in the process surrounding decision making relating to life extension of existing plants. A typical RPV contains a large population of pre-existing flaws introduced during the manufacturing process. The use of probabilistic techniques is necessary to assess the likelihood of crack initiation at one or more of these flaws during a transient event. This report documents development and initial testing of a capability to perform probabilistic fracture mechanics of large populations of flaws in RPVs using reduced order models to compute fracture parameters. The work documented here builds on prior efforts to perform probabilistic analyses of a single flaw with uncertain parameters, as well as earlier work to develop deterministic capabilities to model the thermo-mechanical response of the RPV under transient events, and compute fracture mechanics parameters at locations of pre-defined flaws. The capabilities developed as part of this work provide a foundation for future work, which will develop a platform that provides the flexibility needed to consider scenarios that cannot be addressed with the tools used in current practice.

  17. Study on the mechanism of seepage flow in the grouting for multiple fractured model

    International Nuclear Information System (INIS)

    Nishigaki, Makoto; Mikake, Shin-ichiro

    2002-01-01

    The purpose of study is to improve the grouting method for fractured rock masses. In this paper, the results on the fundamental phenomenon for grasping the properties of grouting injection and seepage flow are discussed. The case of grouting stage is studied about the multiple hydraulic fractured apertures in the injected borehole. So the theory on the mechanism is constructed, and experiment is executed in order to verify the availability of the theory. From the results, it is shown that Bernoulli's law is able to prove the behavior of the grouting. And the theoretical evaluation is executed on the experiential procedure of the grouting. (author)

  18. The use of the J* integral for non-linear fracture mechanics

    International Nuclear Information System (INIS)

    Hellen, T.K.

    1976-09-01

    The Griffith energy balance criterion, first postulated over 50 years ago, is still the basis of linear elastic fracture mechanics. From this, accurate numerical methods for establishing stress intensity factors and energy release rates have been developed. One such method involves path independent contour integrals about the crack tip. An improved contour integral, designated J* is discussed, and shown to have distinct advantages over others in non-linear strain situations. A number of examples are shown including fractures in thermo-plastic and creep situations. (author)

  19. Rock mechanics issues and research needs in the disposal of wastes in hydraulic fractures

    International Nuclear Information System (INIS)

    Doe, T.W.; McClain, W.C.

    1984-07-01

    The proposed rock mechanics studies outlined in this document are designed to answer the basic questions concerning hydraulic fracturing for waste disposal. These questions are: (1) how can containment be assured for Oak Ridge or other sites; and (2) what is the capacity of a site. The suggested rock mechanics program consists of four major tasks: (1) numerical modeling, (2) laboratory testing, (3) field testing, and (4) monitoring. These tasks are described

  20. Hygrothermal effects on dynamic mechanical snalysis and fracture behavior of polymeric composites

    Directory of Open Access Journals (Sweden)

    Michelle Leali Costa

    2005-09-01

    Full Text Available Polymer composites used above their glass transition temperatures Tg present a substantial degradation of physical properties; therefore a material's glass transition temperature and its change with moisture absorption are of practical importance. Little attention has been paid to the role of the adhesive bonding between the reinforcing fiber and matrix, particularly for BMI matrix. In this work the effect of moisture on the dynamic mechanical behavior and the fiber/matrix interface was investigated. Two systems were evaluated: carbon fabric/epoxy and carbon fabric/bismaleimide laminates. The results demonstrated that the moisture absorbed by the laminates causes either reversible or irreversible plasticization of the matrix. The humidity combined with the temperature effects may cause significant changes in the Tg matrix and toughness affecting the laminate strength. Moisture absorption was correlated to the fracture mode of the laminate demonstrating the deleterious effect of moisture on the interface. This leads to debonding between fiber and matrix. This behavior was investigated by scanning electron microscopy and dynamic mechanical analysis.

  1. Flexible parallel implicit modelling of coupled thermal-hydraulic-mechanical processes in fractured rocks

    Science.gov (United States)

    Cacace, Mauro; Jacquey, Antoine B.

    2017-09-01

    Theory and numerical implementation describing groundwater flow and the transport of heat and solute mass in fully saturated fractured rocks with elasto-plastic mechanical feedbacks are developed. In our formulation, fractures are considered as being of lower dimension than the hosting deformable porous rock and we consider their hydraulic and mechanical apertures as scaling parameters to ensure continuous exchange of fluid mass and energy within the fracture-solid matrix system. The coupled system of equations is implemented in a new simulator code that makes use of a Galerkin finite-element technique. The code builds on a flexible, object-oriented numerical framework (MOOSE, Multiphysics Object Oriented Simulation Environment) which provides an extensive scalable parallel and implicit coupling to solve for the multiphysics problem. The governing equations of groundwater flow, heat and mass transport, and rock deformation are solved in a weak sense (either by classical Newton-Raphson or by free Jacobian inexact Newton-Krylow schemes) on an underlying unstructured mesh. Nonlinear feedbacks among the active processes are enforced by considering evolving fluid and rock properties depending on the thermo-hydro-mechanical state of the system and the local structure, i.e. degree of connectivity, of the fracture system. A suite of applications is presented to illustrate the flexibility and capability of the new simulator to address problems of increasing complexity and occurring at different spatial (from centimetres to tens of kilometres) and temporal scales (from minutes to hundreds of years).

  2. The effect of inferomedial screw on postoperative shoulder function and mechanical alignment in proximal humerus fractures.

    Science.gov (United States)

    Erdoğan, Murat; Desteli, Engin Eren; İmren, Yunus; Üztürk, Ali; Kılıç, Mesut; Sezgin, Hicabi

    2014-10-01

    The aim of the study was to evaluate the clinical and radiologic results of locking plate fixation with or without inferomedial screw (IMS) in surgically treated proximal humerus fractures. Thirty-six patients with displaced proximal humerus fractures from two centers were operated using locking plate. All of the fractures were classified according to the Neer classification. In 18 of the cases, an additional IMS running through the medial curvature of the surgical neck was used. There was no significant difference among both groups in terms of height, gender, weight, and mechanism of injury. The fractures were evaluated according to the radiographic and functional findings during follow-up period of 14 months in average (range 8-32 months). At the end of first year, shoulder radiographs were received and shoulder examinations were performed using ASES scores. Humeral head-shaft angles were measured by true AP projections. Head-shaft angle measurements were categorized as varus if 145. Mean time for fracture healing was 18 weeks. Complete union was achieved in 35 patients by the end of 6 months. In one of the 18 displaced proximal humerus fractures of IMS (+) group, the head-shaft angle was measured to be <125, whereas six patients had varus deviation in IMS (-) group at follow-up (p < 0.05). Mean ASES scores of IMS (+) group and IMS (-) group were 58.21 ± 5.82 and 38.61 ± 3.44, respectively (p < 0.001). Use of inferomedial screw running through the medial curvature of surgical neck prevents varus deformity and improves functional outcome after surgical treatment for proximal humerus fractures.

  3. Fracture mechanics evaluation of cast duplex stainless steel after thermal aging

    International Nuclear Information System (INIS)

    Tujikura, Y.; Urata, S.

    1999-01-01

    For the primary coolant piping of PWRs in Japan, cast duplex stainless steel, which is excellent in terms of strength, corrosion resistance and weldability, has conventionally been used. Cast duplex stainless steel contains the ferrite phase in the austenite matrix, and thermal aging after long-term service is known to decrease fracture toughness. Therefore, we evaluated the integrity of the primary coolant piping for an initial PWR plant in Japan by means of elastic plastic fracture mechanics. The evaluation results show that the crack will not grow into an unstable fracture and the integrity of the piping will be secure, even when such through-wall crack length is assumed to be as large as the fatigue crack length grown for a service period of up to 60 years. (orig.)

  4. Fracture mechanics evaluation of cast duplex stainless steel after thermal aging

    Energy Technology Data Exchange (ETDEWEB)

    Tujikura, Y.; Urata, S. [Kansai Electr. Power Co., Inc., Osaka (Japan). General Office of Nucl. and Fossil Power Production

    1999-07-01

    For the primary coolant piping of PWRs in Japan, cast duplex stainless steel, which is excellent in terms of strength, corrosion resistance and weldability, has conventionally been used. Cast duplex stainless steel contains the ferrite phase in the austenite matrix, and thermal aging after long-term service is known to decrease fracture toughness. Therefore, we evaluated the integrity of the primary coolant piping for an initial PWR plant in Japan by means of elastic plastic fracture mechanics. The evaluation results show that the crack will not grow into an unstable fracture and the integrity of the piping will be secure, even when such through-wall crack length is assumed to be as large as the fatigue crack length grown for a service period of up to 60 years. (orig.)

  5. Mechanical and fracture properties at impact loading of selected steels for nuclear power engineering

    International Nuclear Information System (INIS)

    Buchar, J.; Bilek, Z.

    1988-01-01

    The possibilities are briefly characterized of experimental research of mechanical and fracture properties of steels used in nuclear power engineering. Attention is paid to plastic deformation and the assessment of fracture formation during impact loading. The results are reported for steels 15Kh2MFA and 10GN2MFA. For steel 15Kh2MFA the effect was also studied of neutron radiation at different temperatures. From the theory developed for non-irradiated material 10GN2MFA, a prediction is made within the original model of the fracture stress value for steel 15Kh2MFA in both non-irradiated and irradiated states. The conclusion is arrived at that the existing methods of assessing steel properties at impact load allow obtaining knowledge of all significant effects during actual stress, this using only small specimens of the materials. (Z.M.). 4 figs., 8 refs

  6. Nontraumatic Fracture of the Femoral Condylar Prosthesis in a Total Knee Arthroplasty Leading to Mechanical Failure

    Directory of Open Access Journals (Sweden)

    Girish N. Swamy

    2014-01-01

    Full Text Available This paper reports a case of fatigue fracture of the femoral component in a cruciate-retaining cemented total knee arthroplasty (TKA. A 64-year-old man had undergone a primary TKA for osteoarthritis 10 years previously at another institution using the PFC-Sigma prosthesis. The patient recovered fully and was back to his regular activities. He presented with a history of sudden onset pain and locking of the left knee since the preceding three months. There was no history of trauma, and the patient was mobilizing with difficulty using crutches. Radiographs revealed fracture of the posterior condyle of the femoral prosthesis. Revision surgery was performed as an elective procedure revealing the broken prosthesis. The TC3RP-PFC revision prosthesis was used with a medial parapatellar approach. The patient recovered fully without any squeal. Mechanical failure of the knee arthroplasty prosthesis is rare, and nontraumatic fracture of the femoral metallic component has not been reported before.

  7. Nontraumatic fracture of the femoral condylar prosthesis in a total knee arthroplasty leading to mechanical failure.

    Science.gov (United States)

    Swamy, Girish N; Quah, Conal; Bagouri, Elmunzar; Badhe, Nitin P

    2014-01-01

    This paper reports a case of fatigue fracture of the femoral component in a cruciate-retaining cemented total knee arthroplasty (TKA). A 64-year-old man had undergone a primary TKA for osteoarthritis 10 years previously at another institution using the PFC-Sigma prosthesis. The patient recovered fully and was back to his regular activities. He presented with a history of sudden onset pain and locking of the left knee since the preceding three months. There was no history of trauma, and the patient was mobilizing with difficulty using crutches. Radiographs revealed fracture of the posterior condyle of the femoral prosthesis. Revision surgery was performed as an elective procedure revealing the broken prosthesis. The TC3RP-PFC revision prosthesis was used with a medial parapatellar approach. The patient recovered fully without any squeal. Mechanical failure of the knee arthroplasty prosthesis is rare, and nontraumatic fracture of the femoral metallic component has not been reported before.

  8. Combined loading effects on the fracture mechanics behavior of line pipes

    Energy Technology Data Exchange (ETDEWEB)

    Bravo, R.E.; Cravero, S.; Ernst, H.A. [Tenaris Group, Campana (Argentina). SIDERCA R and D Center

    2009-12-19

    For certain applications, pipelines may be submitted to biaxial loading situations. In these cases, it is not clear the influence of the biaxial loading on the fracture mechanics behavior of cracked pipelines. For further understanding of biaxial loading effects, this work presents a numerical simulation of ductile tearing in a circumferentially surface cracked pipe under biaxial loading using the computational cell methodology. The model was adjusted with experimental results obtained in laboratory using single edge cracked under tension (SENT) specimens. These specimens appear as the better alternative to conventional fracture specimens to characterize fracture toughness of cracked pipes. The negligible effect of biaxial loadings on resistance curves was demonstrated. To guarantee the similarities of stress and strains fields between SENT specimens and cracked pipes subjected to biaxial loading, a constraint study using the J-Q methodology and the h parameter was used. The constraint study gives information about the characteristics of the crack-tip conditions. (author)

  9. The Role of Multi-wall Carbon Nanotubes on Fracture Mechanism of Epoxy Nanocomposite

    Directory of Open Access Journals (Sweden)

    M. Hooshiar Sadegian

    2008-12-01

    Full Text Available In order to investigate the role of multi-wall carbon nanotubes (MWCNTs on fracture mechanism of epoxy nanocomposites, a series of tensile standard specimens reinforced with different carbon nanotube contents (0, 0.3, 0.6 and 1 wt% were produced. The fracture surfaces of the produced nanocomposites were evaluated using scanning electron microscope (SEM. The results show that the surface fracture of epoxy nanocomposites comprised of three regions, i.e. mirror, transition and final propagation zones. The extension of all zones depends strongly on curing agent as well asMWCNTs content. The mirror zone is disappeared as curing agent and MWCNTs content increases, while the transition zone depends on the nucleation rate of secondary microcrack. The pattern of final propagation zone becomes coarser as MWCNTs are added to epoxy system.

  10. Metallurgical characteristics and fracture mechanical properties of unirradiated Kori-1 RPV weld: Linde 80, WF-233

    International Nuclear Information System (INIS)

    Hong, Jun Hwa; Lee, B. S.; Oh, Y. J.; Chi, S. H.; Kim, J. H.; Park, D. G.; Yoon, J. H.; Oh, J. M.

    2000-07-01

    The fracture toughness transition properties of the low upper shelf weld, Linde 80 WF-233, of Kori-1 RPV were evaluated by the master curve method, which is designated by ASTM E 1921, 'Standard test method for determination of reference temperature, T o , for ferritic steels in the transition range'. The reference temperature, T o =-83 deg C, was determined by PCVN specimens at -90 deg C. This value is similar to that of other high copper welds. The initial RT NDT was conservatively estimated as -26 deg F from the current fracture toughness results. From the studies on the chemistry and microstructure, the fracture mechanical properties of WF-233 weld is convincingly not worse than WF-70 and 72W welds

  11. Fracture analysis for engineering geological utilization

    Energy Technology Data Exchange (ETDEWEB)

    Choi, H I; Choi, P Y; Hong, S H; Chi, K H; Kim, J Y; Lee, S R; Lee, S G; Park, D W; Han, J G [Korea Institute of Geology Mining and Materials, Taejon (Korea, Republic of)

    1997-12-01

    The problem of geological hazards (earthquakes) and water or thermal resources urges us to understand the regional tectonic setting or recent tectonics. The Uisong Subbasin is located in one of the seismicity zones in Korea. Because the reactivity of the Gaeum Fault System is an important problem focussing on these faults, we studied their whole extension and timing of faulting in terms of tectonics. Fault tectonic analysis is so effective as to easily reconstruct the tectonic sequence and each stress state at each site, eventually in a region. One can get insights for faulting timing in terms of the restored tectonic sequence, and discriminating the active faults or the faults active in the last (present) tectonics. Examining the filling materials in tension gashes, one can get raw knowledge regarding the thermal states at each site. For this study, we first analyzed the topographic textures (lineament, drainage and circular structures) on the relief map produced based on the topographic maps of 1:100,000 scale. Through investigations of susceptible area along the faults, their existence and movement modes were studied, and we can get information about movement history and whole extension of the faults belonging to the WNW-ESE trending Gaeum Fault System. In order to reconstruct the tectonic sequence, we measured fault slip data, tension gashes and dikes, from which fault populations were classified and stress (and thermal) states were determined. Seven compressional tectonic events and six extensional events were reconstructed. Because coaxial events partially coexisted, we bundled these events in one, finally we get seven tectonic events. Determining the types of minerals filling the tension gashes, we suggested the possibility of investigation of geothermal resources with less efforts. (author). 162 refs., 14 tabs., 51 figs.

  12. The association between type of spine fracture and the mechanism of trauma: A useful tool for identifying mechanism of trauma on legal medicine field.

    Science.gov (United States)

    Aghakhani, Kamran; Kordrostami, Roya; Memarian, Azadeh; Asl, Nahid Dadashzadeh; Zavareh, Fatemeh Noorian

    2018-05-01

    Determining the association between mechanism of trauma, and the type of spine column fracture is a useful approach for exactly describing spine injury on forensic medicine field. We aimed to determine mechanism of trauma based on distribution of the transition of spinal column fractures. This cross-sectional survey was performed on 117 consecutive patients with the history of spinal trauma who were admitted to emergency ward of Rasoul-e-Akram Hospital in Tehran, Iran from April 2015 to March 2016. The baseline characteristics were collected by reviewing the hospital recorded files. With respect to mechanism of fracture, 63.2% of fractures were caused by falling, 30.8% by collisions with motor vehicles, and others caused by the violence. Regarding site of fracture, lumbosacral was affected in 47.9%, thoracic in 29.9%, and cervical in 13.7%. Regarding type of fracture, burst fracture was the most common type (71.8%) followed by compressive fracture (14.5%). The site of fracture was specifically associated with the mechanism of injury; the most common injuries induced by falling from height were found in lumbosacral and cervical sites, and the most frequent injuries by traffic accidents were found in thoracic site; also the injuries following violence were observed more in lumbar vertebrae. The burst fractures were more revealed in the patients affected by falling from height and by traffic accidents, and both burst and compressive fractures were more observed with the same result in the patients injured with violence (p = 0.003). The type of spine fracture due to trauma is closely associated with the mechanism of trauma that can be helpful in legal medicine to identify the mechanism of trauma in affected patients. Copyright © 2018. Published by Elsevier Ltd.

  13. Fracture Mechanics Analyses of Subsurface Defects in Reinforced Carbon-Carbon Joggles Subjected to Thermo-Mechanical Loads

    Science.gov (United States)

    Knight, Norman F., Jr.; Raju, Ivatury S.; Song, Kyongchan

    2011-01-01

    Coating spallation events have been observed along the slip-side joggle region of the Space Shuttle Orbiter wing-leading-edge panels. One potential contributor to the spallation event is a pressure build up within subsurface voids or defects due to volatiles or water vapor entrapped during fabrication, refurbishment, or normal operational use. The influence of entrapped pressure on the thermo-mechanical fracture-mechanics response of reinforced carbon-carbon with subsurface defects is studied. Plane-strain simulations with embedded subsurface defects are performed to characterize the fracture mechanics response for a given defect length when subjected to combined elevated-temperature and subsurface-defect pressure loadings to simulate the unvented defect condition. Various subsurface defect locations of a fixed-length substrate defect are examined for elevated temperature conditions. Fracture mechanics results suggest that entrapped pressure combined with local elevated temperatures have the potential to cause subsurface defect growth and possibly contribute to further material separation or even spallation. For this anomaly to occur, several unusual circumstances would be required making such an outcome unlikely but plausible.

  14. A calculational round robin in elastic-plastic fracture mechanics

    International Nuclear Information System (INIS)

    Larsson, L.H.

    Eighteen organizations participated in this round robin which treated the same three-point bend problem as an ASTM round robin four years earlier. Overall deformation, J, CTOD and crack profile were the main results required using plane strain elastic-plastic finite element analysis for a monotonically increasing load up to a maximum deformation which was far beyond the elastic regime. All elastic solutions were accurate to within a few percent. In the elastic-plastic regime, however, there was a large scatter of the results, increasing with increasing plastic deformation and roughly of the same order as in the ASTM round robin which contained ten solutions. Apparently no significant progress has taken place in the state of the art of numerical EPFM analysis in four years time. The paper discusses the reasons for this scatter and draws tentative conclusions on the most suitable numerical analysis methods in EPFM. (Auth.)

  15. Fracture mechanics in new designed power module under thermo-mechanical loads

    Directory of Open Access Journals (Sweden)

    Durand Camille

    2014-06-01

    Full Text Available Thermo-mechanically induced failure is a major reliability issue in the microelectronic industry. On this account, a new type of Assembly Interconnected Technology used to connect MOSFETs in power modules has been developed. The reliability is increased by using a copper clip soldered on the top side of the chip, avoiding the use of aluminium wire bonds, often responsible for the failure of the device. Thus the new designed MOSFET package does not follow the same failure mechanisms as standard modules. Thermal and power cycling tests were performed on these new packages and resulting failures were analyzed. Thermo-mechanical simulations including cracks in the aluminium metallization and intermetallics (IMC were performed using Finite Element Analysis in order to better understand crack propagation and module behaviour.

  16. Proceedings of the Joint IAEA/CSNI Specialists` Meeting on Fracture Mechanics Verification by Large-Scale Testing held at Pollard Auditorium, Oak Ridge, Tennessee

    Energy Technology Data Exchange (ETDEWEB)

    Pugh, C.E.; Bass, B.R.; Keeney, J.A. [comps.] [Oak Ridge National Lab., TN (United States)

    1993-10-01

    This report contains 40 papers that were presented at the Joint IAEA/CSNI Specialists` Meeting Fracture Mechanics Verification by Large-Scale Testing held at the Pollard Auditorium, Oak Ridge, Tennessee, during the week of October 26--29, 1992. The papers are printed in the order of their presentation in each session and describe recent large-scale fracture (brittle and/or ductile) experiments, analyses of these experiments, and comparisons between predictions and experimental results. The goal of the meeting was to allow international experts to examine the fracture behavior of various materials and structures under conditions relevant to nuclear reactor components and operating environments. The emphasis was on the ability of various fracture models and analysis methods to predict the wide range of experimental data now available. The individual papers have been cataloged separately.

  17. Failure probability assessment of wall-thinned nuclear pipes using probabilistic fracture mechanics

    International Nuclear Information System (INIS)

    Lee, Sang-Min; Chang, Yoon-Suk; Choi, Jae-Boong; Kim, Young-Jin

    2006-01-01

    The integrity of nuclear piping system has to be maintained during operation. In order to maintain the integrity, reliable assessment procedures including fracture mechanics analysis, etc., are required. Up to now, this has been performed using conventional deterministic approaches even though there are many uncertainties to hinder a rational evaluation. In this respect, probabilistic approaches are considered as an appropriate method for piping system evaluation. The objectives of this paper are to estimate the failure probabilities of wall-thinned pipes in nuclear secondary systems and to propose limited operating conditions under different types of loadings. To do this, a probabilistic assessment program using reliability index and simulation techniques was developed and applied to evaluate failure probabilities of wall-thinned pipes subjected to internal pressure, bending moment and combined loading of them. The sensitivity analysis results as well as prototypal integrity assessment results showed a promising applicability of the probabilistic assessment program, necessity of practical evaluation reflecting combined loading condition and operation considering limited condition

  18. Fracture Mechanics Analyses of the Slip-Side Joggle Regions of Wing-Leading Edge Panels

    Science.gov (United States)

    Raju, Ivatury S.; Knight, Norman F., Jr.; Song, Kyongchan; Phillips, Dawn R.

    2010-01-01

    The Space Shuttle Orbiter wing comprises of 22 leading edge panels on each side of the wing. These panels are part of the thermal protection system that protects the Orbiter wings from extreme heating that take place on the reentry in to the earth atmosphere. On some panels that experience extreme heating, liberation of silicon carbon (SiC) coating was observed on the slip side regions of the panels. Global structural and local fracture mechanics analyses were performed on these panels as a part of the root cause investigation of this coating liberation anomaly. The wing-leading-edge reinforced carbon-carbon (RCC) panels, Panel 9, T-seal 10, and Panel 10, are shown in Figure 1 and the progression of the stress analysis models is presented in Figure 2. The global structural analyses showed minimal interaction between adjacent panels and the T-seal that bridges the gap between the panels. A bounding uniform temperature is applied to a representative panel and the resulting stress distribution is examined. For this loading condition, the interlaminar normal stresses showed negligible variation in the chord direction and increased values in the vicinity of the slip-side joggle shoulder. As such, a representative span wise slice on the panel can be taken and the cross section can be analyzed using plane strain analysis.

  19. Fracture of the proximal tibia after revision total knee arthroplasty with an extensor mechanism allograft.

    Science.gov (United States)

    Klein, Gregg R; Levine, Harlan B; Sporer, Scott M; Hartzband, Mark A

    2013-02-01

    Extensor mechanism reconstruction with an extensor mechanism allograft (EMA) remains one of the most reliable methods for treating the extensor mechanism deficient total knee arthroplasty. We report 3 patients who were treated with an EMA who sustained a proximal tibial shaft fracture. In all 3 cases, a short tibial component was present that ended close to the level of the distal extent of the bone block. When performing an EMA, it is important to recognize that the tibial bone block creates a stress riser and revision to a long-stemmed tibial component should be strongly considered to bypass this point to minimize the risk of fracture. Copyright © 2013 Elsevier Inc. All rights reserved.

  20. Understanding Irreversible Degradation of Nb3Sn Wires with Fundamental Fracture Mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Zhai, Yuhu [PPPL; Calzolaio, Ciro [Univ of Geneva; Senatore, Carmine [Univ of Geneva

    2014-08-01

    Irreversible performance degradation of advanced Nb3Sn superconducting wires subjected to transverse or axial mechanical loading is a critical issue for the design of large-scale fusion and accelerator magnets such as ITER and LHC. Recent SULTAN tests indicate that most cable-in-conduit conductors for ITER coils made of Nb3Sn wires processed by various fabrication techniques show similar performance degradation under cyclic loading. The irreversible degradation due to filament fracture and local strain accumulation in Nb3Sn wires cannot be described by the existing strand scaling law. Fracture mechanic modeling combined with X-ray diffraction imaging of filament micro-crack formation inside the wires under mechanical loading may reveal exciting insights to the wire degradation mechanisms. We apply fundamental fracture mechanics with a singularity approach to study influence of wire filament microstructure of initial void size and distribution to local stress concentration and potential crack propagation. We report impact of the scale and density of the void structure on stress concentration in the composite wire materials for crack initiation. These initial defects result in an irreversible degradation of the critical current beyond certain applied stress. We also discuss options to minimize stress concentration in the design of the material microstructure for enhanced wire performance for future applications.

  1. Effect of the build orientation on the mechanical properties and fracture modes of SLM Ti–6Al–4V

    Energy Technology Data Exchange (ETDEWEB)

    Simonelli, M., E-mail: M.Simonelli@lboro.ac.uk [Department of Materials, Loughborough University, Loughborough LE11 3TU (United Kingdom); Tse, Y.Y. [Department of Materials, Loughborough University, Loughborough LE11 3TU (United Kingdom); Tuck, C. [Additive Manufacturing and 3D Printing Research Group, Faculty of Engineering, The University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2014-10-20

    Recent research on the additive manufacturing (AM) of Ti alloys has shown that the mechanical properties of the parts are affected by the characteristic microstructure that originates from the AM process. To understand the effect of the microstructure on the tensile properties, selective laser melted (SLM) Ti–6Al–4V samples built in three different orientations were tensile tested. The investigated samples were near fully dense, in two distinct conditions, as-built and stress relieved. It was found that the build orientation affects the tensile properties, and in particular the ductility of the samples. The mechanical anisotropy of the parts was discussed in relation to the crystallographic texture, phase composition and the predominant fracture mechanisms. Fractography and electron backscatter diffraction (EBSD) results indicate that the predominant fracture mechanism is intergranular fracture present along the grain boundaries and thus provide and explain the typical fracture surface features observed in fracture AM Ti–6Al–4V.

  2. Effect of the build orientation on the mechanical properties and fracture modes of SLM Ti–6Al–4V

    International Nuclear Information System (INIS)

    Simonelli, M.; Tse, Y.Y.; Tuck, C.

    2014-01-01

    Recent research on the additive manufacturing (AM) of Ti alloys has shown that the mechanical properties of the parts are affected by the characteristic microstructure that originates from the AM process. To understand the effect of the microstructure on the tensile properties, selective laser melted (SLM) Ti–6Al–4V samples built in three different orientations were tensile tested. The investigated samples were near fully dense, in two distinct conditions, as-built and stress relieved. It was found that the build orientation affects the tensile properties, and in particular the ductility of the samples. The mechanical anisotropy of the parts was discussed in relation to the crystallographic texture, phase composition and the predominant fracture mechanisms. Fractography and electron backscatter diffraction (EBSD) results indicate that the predominant fracture mechanism is intergranular fracture present along the grain boundaries and thus provide and explain the typical fracture surface features observed in fracture AM Ti–6Al–4V

  3. The fracture mechanics of steam turbine electron beam welded rotors

    International Nuclear Information System (INIS)

    Coulon, P.A.

    1987-01-01

    Increased steam turbine unit ratings presupposes that steelmakers are capable of manufacturing larger and larger rotor components. However, there are few steelmakers in the world capable of manufacturing monobloc rotors for high rated turbines, which limits the choice of supplier. Most nuclear turbine rotors have a composite arrangement and are made either by shrinking discs on a shaft or using elements welded together. Those in favour of welding have applied a classical socalled ''submerged'' method using a filler metal. However welding can also be performed by using an Electron Beam in a vacuum room without a filler metal. This technique has many advantages: mechanical characteristics of the joint are identical to those of the base material after tempering without heat affected zones. Moreover, parts are only very slightly deformed during welding. Two steam turbine rotors have been produced in this way. This paper described the destructive tests carried out in the four Electron Beam (EB) welds (two on each rotor)

  4. Hip fracture in the elderly: a re-analysis of the EPIDOS study with causal Bayesian networks.

    Science.gov (United States)

    Caillet, Pascal; Klemm, Sarah; Ducher, Michel; Aussem, Alexandre; Schott, Anne-Marie

    2015-01-01

    Hip fractures commonly result in permanent disability, institutionalization or death in elderly. Existing hip-fracture predicting tools are underused in clinical practice, partly due to their lack of intuitive interpretation. By use of a graphical layer, Bayesian network models could increase the attractiveness of fracture prediction tools. Our aim was to study the potential contribution of a causal Bayesian network in this clinical setting. A logistic regression was performed as a standard control approach to check the robustness of the causal Bayesian network approach. EPIDOS is a multicenter study, conducted in an ambulatory care setting in five French cities between 1992 and 1996 and updated in 2010. The study included 7598 women aged 75 years or older, in which fractures were assessed quarterly during 4 years. A causal Bayesian network and a logistic regression were performed on EPIDOS data to describe major variables involved in hip fractures occurrences. Both models had similar association estimations and predictive performances. They detected gait speed and mineral bone density as variables the most involved in the fracture process. The causal Bayesian network showed that gait speed and bone mineral density were directly connected to fracture and seem to mediate the influence of all the other variables included in our model. The logistic regression approach detected multiple interactions involving psychotropic drug use, age and bone mineral density. Both approaches retrieved similar variables as predictors of hip fractures. However, Bayesian network highlighted the whole web of relation between the variables involved in the analysis, suggesting a possible mechanism leading to hip fracture. According to the latter results, intervention focusing concomitantly on gait speed and bone mineral density may be necessary for an optimal prevention of hip fracture occurrence in elderly people.

  5. Mechanisms and multi-scale modelling of the brittle fracture modifications induced by thermal ageing of a pressurised water reactor steel

    International Nuclear Information System (INIS)

    Andrieu, Antoine

    2013-01-01

    The use of some PWR components at a relatively high temperature generates a drop of their fracture properties. This embrittlement is generally attributed to the segregation of some impurities at grains boundaries. This work aims at correlating the kinetics of this segregation to the embrittlement kinetics through a multi-scale approach, combining thermodynamical and micro-mechanical analysis. (author)

  6. Hybrid external fixation in the treatment of tibial pilon fractures: A retrospective analysis of 162 fractures.

    Science.gov (United States)

    Galante, Vito N; Vicenti, Giovanni; Corina, Gianfranco; Mori, Claudio; Abate, Antonella; Picca, Girolamo; Conserva, Vito; Speciale, Domenico; Scialpi, Lorenzo; Tartaglia, Nicola; Caiaffa, Vincenzo; Moretti, Biagio

    2016-10-01

    To determine the efficacy of hybrid external fixation in the treatment of tibial pilon fractures. Retrospective, multicentre study. Adult patients with tibial pilon fractures treated with hybrid external fixation. Fracture reduction with ligamentotaxis and fixation with XCaliber hybrid external fixator. Fracture union, complications, functional outcome (Mazur Ankle Score). Union was obtained in 159 fractures at an average of 125days; there were three delayed unions and three non-unions. The most frequent complication was superficial pin-track infections (48), all of which responded to local wound care and antibiotics. There were no deep infections and no DVT. Only one fracture had loss of reduction that required frame revision. The overall functional scores were 91 (excellent) for AO/OTA type A fractures, 89 (good) for type B fractures, and 75 (satisfactory) for type C fractures. Hybrid external fixation is an effective method of stabilising tibial pilon fractures, particularly those with marked comminution. The minimally-invasive technique and stable fixation enable early mobilisation, with good functional results and minimal complications. Level IV Case series. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Analysis of blowout fractures using cine mode MRI

    International Nuclear Information System (INIS)

    Kawahara, Masaaki; Shiihara, Kumiko; Kimura, Hisashi; Fukai, Sakuko; Tabuchi, Akio; Kojo, Tuyoshi

    1995-01-01

    By observing conventional CT and MRI images, it is difficult to distinguish extension failure from adhesion, bone fracture or damage to the extraocular muscle, any one of which may be the direct cause of the eye movement disturbance accompanying blowout fracture. We therefore carried out dynamic analysis of eye movement disturbance using a cine mode MRI. We put seven fixation points in the gantry of the MRI and filmed eye movement disturbances by the gradient echo method, using a surface coil and holding the vision on each fixation point. We also video recorded the CRT monitor of the MRI to obtain dynamic MRI images. The subjects comprised 5 cases (7-23 years old). In 4 cases, we started orthoptic treatment, saccadic eye movement training, convergence training and fusional amplitude training after surgery, with only orthoptic treatment in the 5 th case. In all cases, fusion area improvement was recognized during training. In 2 cases examined by cine mode MRI before and after surgery, we observed improved eye movement after training, the effectiveness of which was thereby proven. Also, using cine mode MRI we were able to determine the character of incarcerated tissue and the cause of eye movement disturbance. We conclude that it blowout fracture, cine mode MRI may be useful in selecting treatment and observing its effectiveness. (author)

  8. Mechanical stimulation enhanced estrogen receptor expression and callus formation in diaphyseal long bone fracture healing in ovariectomy-induced osteoporotic rats.

    Science.gov (United States)

    Chow, S K H; Leung, K S; Qin, J; Guo, A; Sun, M; Qin, L; Cheung, W H

    2016-10-01

    Estrogen receptor (ER) in ovariectomy-induced osteoporotic fracture was reported to exhibit delayed expression. Mechanical stimulation enhanced ER-α expression in osteoporotic fracture callus at the tissue level. ER was also found to be required for the effectiveness of vibrational mechanical stimulation treatment in osteoporotic fracture healing. Estrogen receptor(ER) is involved in mechanical signal transduction in bone metabolism. Its expression was reported to be delayed in osteoporotic fracture healing. The purpose of this study was to investigate the roles played by ER during osteoporotic fracture healing enhanced with mechanical stimulation. Ovariectomy-induced osteoporotic SD rats that received closed femoral fractures were divided into five groups, (i) SHAM, (ii) SHAM-VT, (iii) OVX, (iv) OVX-VT, and (v) OVX-VT-ICI, where VT stands for whole-body vibration treatment and ICI for ER antagonization by ICI 182,780. Callus formation and gene expression were assessed at 2, 4, and 8 weeks postfracture. In vitro osteoblastic differentiation, mineralization, and ER-α expression were assessed. The delayed ER expression was found to be enhanced by vibration treatment. Callus formation enhancement was shown by callus morphometry and micro-CT analysis. Enhancement effects by vibration were partially abolished when ER was modulated by ICI 182,780, in terms of callus formation capacity at 2-4 weeks and ER gene and protein expression at all time points. In vitro, ER expression in osteoblasts was not enhanced by VT treatment, but osteoblastic differentiation and mineralization were enhanced under estrogen-deprived condition. When osteoblastic cells were modulated by ICI 182,780, enhancement effects of VT were eliminated. Vibration was able to enhance ER expression in ovariectomy-induced osteoporotic fracture healing. ER was essential in mechanical signal transduction and enhancement in callus formation effects during osteoporotic fracture healing enhanced by vibration

  9. Mechanism of distal radius fracture as analyzed by 3D finite element model

    International Nuclear Information System (INIS)

    Tomizawa, Kazuo

    2007-01-01

    The purpose of this study is to see the difference of distal radius fracture between normal and osteoporotic bones and in its patterns due to limb position at injury through simulation and analysis of the biomechanics using three-dimensional (3D) finite element model. CT images were taken with SIEMENS machine, of right wrist joints of 32 and 76 years old, normal healthy man and osteoporotic woman, respectively. The wrist joint angles at CT were 70 degrees both at dorsiflexion and at palmerflexion for simulating fracture at tumbling down. The 3D bone model reconstructed from CT images with Forge software (Studio PON) was trimmed to remain the distal radial-ulnar portion and proximal carpal bones to make simulation easer, and the simplified 3D model was divided to 56,622 elements and 13,274 nodal points (normal bone) or 51,760 and 12,940 (osteoporosis), respectively, in 3 areas of different bone densities calculated with Scion Image processor. This 3D finite element model was analyzed with the software ANSYS LS-DYNA 10.0 for simulating the fracture (the defined yield stress attained) by impacting the elements of carpal bones to the radial bone joint surface with a measure of Mises stress. In osteoporotic bone, fracture was found to occur at dorsal cortex closer to the joint surface. Fracture occurred at dorsal and palmer cortex at dorsiflexion and palmerflexion, respectively. (R.T.)

  10. Analysis of the competition between brittle and ductile fracture: application for the mechanical behaviour of C-Mn and theirs welds; Etude de la competition dechirure ductile/rupture fragile: application de la tenue mecanique des tubes en acier C-Mn et de leurs joints soudes

    Energy Technology Data Exchange (ETDEWEB)

    Le Corre, V

    2006-09-15

    This study deals with the fracture behaviour of welded thin structures in the ductile to brittle transition range. It aims to propose a criterion to define the conditions for which the risk of fracture by cleavage does not exist on a cracked structure. The literature review shows that the difficulties of prediction of the fracture behaviour of a structure are related to the dependence of the fracture probability to the mechanical fields at the crack tip. The ductile to brittle transition range thus depends on the studied geometry of the structure. A threshold stress, below which cleavage cannot take place, is defined using fracture tests on notched specimens broken at very low temperature. The finite element numerical simulation of fracture tests onspecimens in the transition range shows a linear relationship between the fracture probability and the volume exceeding the threshold stress, thus showing the relevance of the proposed criterion. Moreover, several relations are established allowing to simplify the identification of the criterion parameters. The criterion is applied to a nuclear structural C-Mn steel, by focusing more particularly on the higher boundary of the transition range. A fracture test on a full-scale pipe is designed, developed, carried out and analysed using its numerical simulation. The results show firstly that, on the structure, the transition range is shifted in temperature, compared to laboratory specimens, due to the low plasticity constraint achieved in thin structures, and secondly that the threshold stress criterion allows to estimate simply this shift. (author)

  11. Fracture mechanics evaluation of LOFT lower plenum injection nozzle

    International Nuclear Information System (INIS)

    Nagata, P.K.; Reuter, W.G.

    1977-01-01

    An analysis to establish whether or not a leak-before-break concept would apply to the LOFT lower plenum injection nozzle is described. The analysis encompassed the structure from the inlet side of valve V-2170 to the lower plenum nozzle-to-reactor vessel weld on the left side of the emergency core cooling system (ECCS). The defect that was assumed to exist was of such a size that the probability of its being missed by the applicable inspection technique was near zero. The Inconel 600 nozzle forging with an initial assumed defect size of 0.64 cm (0.25 in.) deep would behave as follows: (1) the axially oriented defect would result in leak before rupture (the number of cycles to rupture was 11,000), (2) the circumferentially oriented defect would result in a rupture before leak. The number of cycles to failure would be in excess of 14,000. Based on the conservative assumption that the thermal stresses were membrane stresses as opposed to a bending stress, the following were found. For the Inconel 82 weld metal (thickness of 1.3 cm [0.53 in.]) and AISI 316 SST valve body, with an initial assumed defect of 0.25 cm (0.1 in.), the crack would grow through the thickness in a minimum of 3950 cycles and to a critical rupture crack length of 5.1 cm (2.0 in.) in an additional 80 cycles. The Inconel 82 weld metal at the shell body (thickness of 9.7 cm or 3.8 in.) with an assumed defect 1.3 cm (0.5 in.) deep would fail in 334 cycles. Calculations made assuming a linear stress gradient instead of the above-mentioned flat distribution through the wall indicated that the number of stress cycles increased to 2200

  12. Benchmark on residual stress modeling in fracture mechanics assessment

    International Nuclear Information System (INIS)

    Marie, S.; Deschanels, H.; Chapuliot, S.; Le Delliou, P.

    2014-01-01

    In the frame of development in analytical defect assessment methods for the RSE-M and RCC-MRx codes, new work on the consideration of residual stresses is initiated by AREVA, CEA and EDF. The first step of this work is the realization of a database of F.E. reference cases. To validate assumptions and develop a good practice guideline for the consideration of residual stresses in finite element calculations, a benchmark between AREVA, CEA and EDF is going-on. A first application presented in this paper focuses on the analysis of the crack initiation of aged duplex stainless steel pipes submitted to an increasing pressure loading. Residual stresses are related to pipe fabrication process and act as shell bending condition. Two tests were performed: the first with an internal longitudinal semi-elliptical crack and the second with an external crack. The analysis first focuses on the ability to accurately estimate the measured pressure at the crack initiation of the two tests. For that purpose, the comparison of results obtained with different methods of taking into account the residual stresses (i.e. thermal fields or initial strain field). It then validates post-treatment procedures for J or G determination, and finally compares of the results obtained by the different partners. It is then shown that the numerical models can integrate properly the impact of residual stresses on the crack initiation pressure. Then, an excellent agreement is obtained between the different numerical evaluations of G provided by the participants to the benchmark so that best practice and reference F.E. solutions for residual stresses consideration can be provided based on that work. (authors)

  13. Elastoplasticity analysis of the nails used in long bone fractures

    International Nuclear Information System (INIS)

    Paterson, R; Paterson, A; Miralles, M T; Del Sel, G; Del Sel, N

    2011-01-01

    Elastoplastic endomedullary nail-insertion system in long bone fractures is a method which allows generating forces, moments, frictions and stress states in parts of the bone previously selected. Adding previous knowledge on the distribution of forces and acting moments over the bone fragments to be threaded, as well as on the elastoplastic and mechanical properties of the nails to be inserted (designing a special, specific structure for each case), the results, coming from 26 years of applying this technique, have been promising. It is from this perspective that we call this threading and anchoring procedure 'Selective Tension System' (STS). Physicochemical analyses and mechanical trials on elastoplastic nails used in the osteosynthesis in long bone fractures are presented. The magnitude of the forces produced by flattening the nails and the reacting forces at both ends are measured. It is expected that the evidence provided on the elastic variability of these nails will be useful as guidance on the availability and choice of the elastoplastic combinations that best fit each patient.

  14. Fracture Mechanics Analyses of Reinforced Carbon-Carbon Wing-Leading-Edge Panels

    Science.gov (United States)

    Raju, Ivatury S.; Phillips, Dawn R.; Knight, Norman F., Jr.; Song, Kyongchan

    2010-01-01

    Fracture mechanics analyses of subsurface defects within the joggle regions of the Space Shuttle wing-leading-edge RCC panels are performed. A 2D plane strain idealized joggle finite element model is developed to study the fracture behavior of the panels for three distinct loading conditions - lift-off and ascent, on-orbit, and entry. For lift-off and ascent, an estimated bounding aerodynamic pressure load is used for the analyses, while for on-orbit and entry, thermo-mechanical analyses are performed using the extreme cold and hot temperatures experienced by the panels. In addition, a best estimate for the material stress-free temperature is used in the thermo-mechanical analyses. In the finite element models, the substrate and coating are modeled separately as two distinct materials. Subsurface defects are introduced at the coating-substrate interface and within the substrate. The objective of the fracture mechanics analyses is to evaluate the defect driving forces, which are characterized by the strain energy release rates, and determine if defects can become unstable for each of the loading conditions.

  15. Ipsilateral simultaneous fracture of the trochlea involving the lateral end clavicle and distal end radius: a rare combination and a unique mechanism of injury

    Directory of Open Access Journals (Sweden)

    Gupta RK

    2014-07-01

    Full Text Available 【Abstract】Isolated trochlea fracture in adults is a rare surgical entity as compared to its capitellar counterpart. It has been only mentioned sporadically in the literature as case reports. Fracture of the trochlea is accompanied by other elbow injuries like elbow dislocation, capitellum fracture, ulnar fracture and extraarticular condylar fracture. Here we report a unique case of isolated displaced trochlea fracture associated with fractures of the lateral end clavicle and the distal end radius. We propose a unique mechanism for this rare combination of injuries: typical triad of injury, i.e. fracture of the distal end radius with trochlea and fracture of the lateral end of the clavicle. Nonoperative treatment is recommended for undisplaced humeral trochlea fractures; but for displaced ones, anatomical reduction and internal fixation are essential to maintain the congruous trochleacoronoid articulation and hence to maintain the intrinsic stability of the elbow. Key words: Isolated trochlea fracture; Clavicle; Radius fractures

  16. Ductile fracture mechanics methodology for complex cracks in nuclear piping

    Energy Technology Data Exchange (ETDEWEB)

    Zahoor, A.

    1988-02-01

    Limit load and J-integral estimation solutions are developed for circumferentially complex-cracked pipes in bending. The limit load solution is developed using thick-walled cylinder analysis which included the effects of flaw depth accurately. J-integral estimation solutions are developed that are suitable for a wide range of loading from linear elastic, elastic-plastic to net-section yielding of the flawed section. Mode I stress intensity factor solution is developed from experimental compliance data. Two types of J solutions are developed. First, J solutions for determining the J-resistance curve from single load-displacement record are presented. Next, elastic-plastic J solution in the format of EPRI J estimation scheme is presented. The latter solution was used to predict the load carrying capacity of complex-cracked pipes made of Type-304 stainless steel, Inconel 600, and A106 GrB materials. Predictions were compared against pipe tests to demonstrate the accuracy of the limit load and J estimation solutions.

  17. Ductile fracture mechanics methodology for complex cracks in nuclear piping

    International Nuclear Information System (INIS)

    Zahoor, A.

    1988-01-01

    Limit load and J-integral estimation solutions are developed for circumferentially complex-cracked pipes in bending. The limit load solution is developed using thick-walled cylinder analysis which included the effects of flaw depth accurately. J-integral estimation solutions are developed that are suitable for a wide range of loading from linear elastic, elastic-plastic to net-section yielding of the flawed section. Mode I stress intensity factor solution is developed from experimental compliance data. Two types of J solutions are developed. First, J solutions for determining the J-resistance curve from single load-displacement record are presented. Next, elastic-plastic J solution in the format of EPRI J estimation scheme is presented. The latter solution was used to predict the load carrying capacity of complex-cracked pipes made of Type-304 stainless steel, Inconel 600, and A106 GrB materials. Predictions were compared against pipe tests to demonstrate the accuracy of the limit load and J estimation solutions. (orig.)

  18. Computational methods for fracture analysis of heavy-section steel technology (HSST) press