The Experts below are selected from a list of 48 Experts worldwide ranked by ideXlab platform
A.k. Ghosh - One of the best experts on this subject based on the ideXlab platform.
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An insight of the structure of stress fields for stationary crack in strength mismatch weld under plane strain mode-I loading – Part II: Compact tension and middle tension specimens
International Journal of Mechanical Sciences, 2014Co-Authors: I.a. Khan, Vivek Bhasin, Jayanta Chattopadhyay, R. K. Singh, K. K. Vaze, A.k. GhoshAbstract:Abstract In-service inspections of many nuclear power plants have revealed that cracks are most likely to occur in a weld or in the regions near the weld. In part-I, the problem of a stationary crack lying at the centre of a weld in a pure bending specimen SE(PB) was analysed. The detailed structure of the global Plastic fields for a deep crack, under Fully Plastic Condition, was presented. Aspects related to the state of stress at the base-weld interface were discussed. To enhance our understanding of the weld strength mismatch effects, other commonly used fracture specimens, that is, compact tension C(T) and middle tension M(T) specimens having a weld centre crack were analysed in the present investigation. The influence of weld mismatch on the structure of global stress fields (leading to Plastic yielding of the ligament) as well as on the crack tip constraint was studied. It is demonstrated that, when a crack is postulated at the centre of a weld, a family of stress fields proposed in part-I for a SE(PB) specimen is applicable to a C(T) specimen also. The studies performed in this article, along with part-I, have established that in comparison to slip line field analysis, the modified upper bound theorem is simple and more general. It is applicable to macroscopically homogeneous materials and can also account for weld mismatch effects.
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An insight of the structure of stress fields for stationary crack in strength mismatch weld under plane strain mode-I loading—Part I: Pure bending specimen
International Journal of Mechanical Sciences, 2012Co-Authors: I.a. Khan, Vivek Bhasin, Jayanta Chattopadhyay, A.k. GhoshAbstract:Abstract In-service inspections of many nuclear power plants have revealed that cracks are most likely to occur in or the regions near the weld. Interfacial cracks under elastic as well as in elastic–Plastic Conditions have already been extensively discussed in literature. However, the problem of crack lying at the centre of weld is less understood. Though several detailed numerical studies have been performed to investigate the influence of weld strength mismatch on crack-tip stress fields till date, however, the detailed insight of the structure of stress fields under large scale Plasticity is still lacking. The present article is intended to bridge that gap. In this work, detailed structure of the global Plastic fields which occur in a deeply cracked (a/W>0.3) mismatch welded pure bending specimen, under Fully Plastic Condition, is presented. Aspects related to the state of stress at the interface of two materials are discussed. It is shown that a family of five fields proposed in this work is adequate to cover all practical cases of weld mismatch. Proposed fields were confirmed by detailed full-field finite element analyses. Excellent agreement is observed between the proposed theoretical solutions and the numerical results.
I.a. Khan - One of the best experts on this subject based on the ideXlab platform.
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An insight of the structure of stress fields for stationary crack in strength mismatch weld under plane strain mode-I loading – Part II: Compact tension and middle tension specimens
International Journal of Mechanical Sciences, 2014Co-Authors: I.a. Khan, Vivek Bhasin, Jayanta Chattopadhyay, R. K. Singh, K. K. Vaze, A.k. GhoshAbstract:Abstract In-service inspections of many nuclear power plants have revealed that cracks are most likely to occur in a weld or in the regions near the weld. In part-I, the problem of a stationary crack lying at the centre of a weld in a pure bending specimen SE(PB) was analysed. The detailed structure of the global Plastic fields for a deep crack, under Fully Plastic Condition, was presented. Aspects related to the state of stress at the base-weld interface were discussed. To enhance our understanding of the weld strength mismatch effects, other commonly used fracture specimens, that is, compact tension C(T) and middle tension M(T) specimens having a weld centre crack were analysed in the present investigation. The influence of weld mismatch on the structure of global stress fields (leading to Plastic yielding of the ligament) as well as on the crack tip constraint was studied. It is demonstrated that, when a crack is postulated at the centre of a weld, a family of stress fields proposed in part-I for a SE(PB) specimen is applicable to a C(T) specimen also. The studies performed in this article, along with part-I, have established that in comparison to slip line field analysis, the modified upper bound theorem is simple and more general. It is applicable to macroscopically homogeneous materials and can also account for weld mismatch effects.
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An insight of the structure of stress fields for stationary crack in strength mismatch weld under plane strain mode-I loading—Part I: Pure bending specimen
International Journal of Mechanical Sciences, 2012Co-Authors: I.a. Khan, Vivek Bhasin, Jayanta Chattopadhyay, A.k. GhoshAbstract:Abstract In-service inspections of many nuclear power plants have revealed that cracks are most likely to occur in or the regions near the weld. Interfacial cracks under elastic as well as in elastic–Plastic Conditions have already been extensively discussed in literature. However, the problem of crack lying at the centre of weld is less understood. Though several detailed numerical studies have been performed to investigate the influence of weld strength mismatch on crack-tip stress fields till date, however, the detailed insight of the structure of stress fields under large scale Plasticity is still lacking. The present article is intended to bridge that gap. In this work, detailed structure of the global Plastic fields which occur in a deeply cracked (a/W>0.3) mismatch welded pure bending specimen, under Fully Plastic Condition, is presented. Aspects related to the state of stress at the interface of two materials are discussed. It is shown that a family of five fields proposed in this work is adequate to cover all practical cases of weld mismatch. Proposed fields were confirmed by detailed full-field finite element analyses. Excellent agreement is observed between the proposed theoretical solutions and the numerical results.
Fernando Labbe - One of the best experts on this subject based on the ideXlab platform.
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Modeling of a shallow surface crack in a nuclear pressure pipe by a three-term asymtotic solution
2016Co-Authors: Fernando LabbeAbstract:When a shallow crack exists (depth crack-to-thickness wall ratio less than 0.2) and/or Fully Plastic Condition develops around the crack, the J-integral alone does not describe completely the crack tip stress field. In this paper, an application of the J-A2 methodology is presented to analize the stress field in the vicinity of a three-dimensional shallow crack in a pressurized pipe. The J-A2 methodology is based on a three-term asymptotic stress field around the crack tip. The material is modeled with a flow thery of Plasticity and a finite deformation theory was included to account for the highly nonlinear behavior aroud the crack tip. Numerical finite element results shows that a three-term asymptotic solution describes accurately the stress field in the vicinity of the crack tip in a 3-D shallow crack
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On the Quantification of the Constraint Effect Along a Three-Dimensional Crack Front
International Journal of Mechanical Engineering and Applications, 2016Co-Authors: Fernando LabbeAbstract:Elbows with a shallow surface cracks in nuclear pressure pipes have been recognized as a major origin of potential catastrophic failures. Crack assessment is normally performed by using the J-integral approach. Although this one-parameter-based approach is useful to predict the ductile crack onset, it depends strongly on specimen geometry or constraint level. When a shallow crack exists (depth crack-to-thickness wall ratio less than 0.2) and/or a Fully Plastic Condition develops around the crack, the J-integral alone does not describe completely the crack tip stress field. In this paper, we report on the use of a three-term asymptotic expansion, referred to as the J-A 2 methodology, for modeling the elastic-Plastic stress field around a three-dimensional shallow surface crack in an elbow subject to internal pressure and out-of-plane bending. The material, an A 516 Gr. 70 steel, used in the nuclear industry, was modeled with a Ramberg-Osgood power law and flow theory of Plasticity. A finite deformation theory was included to account for the highly nonlinear behavior around the crack tip. Numerical finite element results were used to calculate a second fracture parameter A 2 for the J-A 2 methodology. We found that the used three-term asymptotic expansion accurately describes the stress field around the considered three-dimensional shallow surface crack.
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J-Q Characterization of Constraint Effects of a Three-Dimensional Cracked Specimen
Journal of Materials Engineering and Performance, 2008Co-Authors: Fernando Labbe, Juan R. DonosoAbstract:Failure assessment of the integrity of a ductile flawed structural component is done currently by a one-parameter fracture mechanics approach. The J -integral is the one-parameter used; it has proven to be useful in order to predict ductile crack initiation. However, when tension loading dominates and/or a Fully Plastic Condition develops around the crack, the J -integral alone does not describe completely the crack-tip stress field and a second parameter is needed. In this work, an accurate modeling of the elastic-Plastic stress field around a deep crack in a three-dimensional three-point bend specimen is carried out. Numerical results for the crack-tip stress field are used to evaluate a crack-tip constraint parameter Q , in terms of applied loading, from contained Plasticity to large-scale yielding. The parameter Q , measures the degree of stress triaxiality and constraint around the crack-tip. In order to obtain the stresses in the near-crack-tip field with high accuracy, a detailed mesh with higher order three-dimensional finite elements is located around the crack front. The modeling of crack-tip blunting deformation is performed by using a small notch radius in the crack-tip. Large-strain and finite-rotation nonlinear behavior effects around the crack-tip are included. The material, an ASTM A 516 steel, is modeled with incremental theory of Plasticity. Numerical results of the Q triaxiality parameter are presented for increasing level loads to obtain an extended yield Condition. Additional results of J -integral parameter and crack-tip opening displacement, for different load ratios and for different position across the specimen thickness are shown.
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Three-term Asymptotic Stress Field Expansion for Analysis of Surface Cracked Elbows in Nuclear Pressure Vessels
Journal of Materials Engineering and Performance, 2007Co-Authors: Fernando LabbeAbstract:Elbows with a shallow surface cracks in nuclear pressure pipes have been recognized as a major origin of potential catastrophic failures. Crack assessment is normally performed by using the J-integral approach. Although this one-parameter-based approach is useful to predict the ductile crack onset, it depends strongly on specimen geometry or constraint level. When a shallow crack exists (depth crack-to-thickness wall ratio less than 0.2) and/or a Fully Plastic Condition develops around the crack, the J-integral alone does not describe completely the crack-tip stress field. In this paper, we report on the use of a three-term asymptotic expansion, referred to as the J – A _2 methodology, for modeling the elastic-Plastic stress field around a three-dimensional shallow surface crack in an elbow subjected to internal pressure and out-of-plane bending. The material, an A 516 Gr. 70 steel, used in the nuclear industry, was modeled with a Ramberg–Osgood power law and flow theory of Plasticity. A finite deformation theory was included to account for the highly nonlinear behavior around the crack tip. Numerical finite element results were used to calculate a second fracture parameter A _2 for the J – A _2 methodology. We found that the used three-term asymptotic expansion accurately describes the stress field around the considered three-dimensional shallow surface crack.
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Modeling of a 3D shallow surface crack in a nuclear pressure pipe by a three-term asymptotic solution: J-A2 methodology
Computational Fluid and Solid Mechanics 2003, 2003Co-Authors: Fernando Labbe, J.r. DonosoAbstract:Publisher Summary When a shallow crack exists (depth crack-to-thickness wall ratio less than 0.2) and/or a Fully Plastic Condition develops around the crack, the J-integral alone does not describe completely the crack-tip-stress field. This chapter presents an application of the J-A2 methodology to analyze the stress field in the vicinity of a three-dimensional shallow crack in a pressurized pipe. The J-A2 methodology is based on a three-term asymptotic stress field around the crack tip. The material is modeled with a flow theory of Plasticity and a finite deformation theory is included to account for the highly nonlinear behavior around the crack tip. Numerical finite element results shows that a three-term asymptotic solution describes accurately the stress field in the vicinity of the crack tip in a 3D shallow crack.
Vivek Bhasin - One of the best experts on this subject based on the ideXlab platform.
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An insight of the structure of stress fields for stationary crack in strength mismatch weld under plane strain mode-I loading – Part II: Compact tension and middle tension specimens
International Journal of Mechanical Sciences, 2014Co-Authors: I.a. Khan, Vivek Bhasin, Jayanta Chattopadhyay, R. K. Singh, K. K. Vaze, A.k. GhoshAbstract:Abstract In-service inspections of many nuclear power plants have revealed that cracks are most likely to occur in a weld or in the regions near the weld. In part-I, the problem of a stationary crack lying at the centre of a weld in a pure bending specimen SE(PB) was analysed. The detailed structure of the global Plastic fields for a deep crack, under Fully Plastic Condition, was presented. Aspects related to the state of stress at the base-weld interface were discussed. To enhance our understanding of the weld strength mismatch effects, other commonly used fracture specimens, that is, compact tension C(T) and middle tension M(T) specimens having a weld centre crack were analysed in the present investigation. The influence of weld mismatch on the structure of global stress fields (leading to Plastic yielding of the ligament) as well as on the crack tip constraint was studied. It is demonstrated that, when a crack is postulated at the centre of a weld, a family of stress fields proposed in part-I for a SE(PB) specimen is applicable to a C(T) specimen also. The studies performed in this article, along with part-I, have established that in comparison to slip line field analysis, the modified upper bound theorem is simple and more general. It is applicable to macroscopically homogeneous materials and can also account for weld mismatch effects.
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An insight of the structure of stress fields for stationary crack in strength mismatch weld under plane strain mode-I loading—Part I: Pure bending specimen
International Journal of Mechanical Sciences, 2012Co-Authors: I.a. Khan, Vivek Bhasin, Jayanta Chattopadhyay, A.k. GhoshAbstract:Abstract In-service inspections of many nuclear power plants have revealed that cracks are most likely to occur in or the regions near the weld. Interfacial cracks under elastic as well as in elastic–Plastic Conditions have already been extensively discussed in literature. However, the problem of crack lying at the centre of weld is less understood. Though several detailed numerical studies have been performed to investigate the influence of weld strength mismatch on crack-tip stress fields till date, however, the detailed insight of the structure of stress fields under large scale Plasticity is still lacking. The present article is intended to bridge that gap. In this work, detailed structure of the global Plastic fields which occur in a deeply cracked (a/W>0.3) mismatch welded pure bending specimen, under Fully Plastic Condition, is presented. Aspects related to the state of stress at the interface of two materials are discussed. It is shown that a family of five fields proposed in this work is adequate to cover all practical cases of weld mismatch. Proposed fields were confirmed by detailed full-field finite element analyses. Excellent agreement is observed between the proposed theoretical solutions and the numerical results.
Jayanta Chattopadhyay - One of the best experts on this subject based on the ideXlab platform.
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An insight of the structure of stress fields for stationary crack in strength mismatch weld under plane strain mode-I loading – Part II: Compact tension and middle tension specimens
International Journal of Mechanical Sciences, 2014Co-Authors: I.a. Khan, Vivek Bhasin, Jayanta Chattopadhyay, R. K. Singh, K. K. Vaze, A.k. GhoshAbstract:Abstract In-service inspections of many nuclear power plants have revealed that cracks are most likely to occur in a weld or in the regions near the weld. In part-I, the problem of a stationary crack lying at the centre of a weld in a pure bending specimen SE(PB) was analysed. The detailed structure of the global Plastic fields for a deep crack, under Fully Plastic Condition, was presented. Aspects related to the state of stress at the base-weld interface were discussed. To enhance our understanding of the weld strength mismatch effects, other commonly used fracture specimens, that is, compact tension C(T) and middle tension M(T) specimens having a weld centre crack were analysed in the present investigation. The influence of weld mismatch on the structure of global stress fields (leading to Plastic yielding of the ligament) as well as on the crack tip constraint was studied. It is demonstrated that, when a crack is postulated at the centre of a weld, a family of stress fields proposed in part-I for a SE(PB) specimen is applicable to a C(T) specimen also. The studies performed in this article, along with part-I, have established that in comparison to slip line field analysis, the modified upper bound theorem is simple and more general. It is applicable to macroscopically homogeneous materials and can also account for weld mismatch effects.
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An insight of the structure of stress fields for stationary crack in strength mismatch weld under plane strain mode-I loading—Part I: Pure bending specimen
International Journal of Mechanical Sciences, 2012Co-Authors: I.a. Khan, Vivek Bhasin, Jayanta Chattopadhyay, A.k. GhoshAbstract:Abstract In-service inspections of many nuclear power plants have revealed that cracks are most likely to occur in or the regions near the weld. Interfacial cracks under elastic as well as in elastic–Plastic Conditions have already been extensively discussed in literature. However, the problem of crack lying at the centre of weld is less understood. Though several detailed numerical studies have been performed to investigate the influence of weld strength mismatch on crack-tip stress fields till date, however, the detailed insight of the structure of stress fields under large scale Plasticity is still lacking. The present article is intended to bridge that gap. In this work, detailed structure of the global Plastic fields which occur in a deeply cracked (a/W>0.3) mismatch welded pure bending specimen, under Fully Plastic Condition, is presented. Aspects related to the state of stress at the interface of two materials are discussed. It is shown that a family of five fields proposed in this work is adequate to cover all practical cases of weld mismatch. Proposed fields were confirmed by detailed full-field finite element analyses. Excellent agreement is observed between the proposed theoretical solutions and the numerical results.
