The Experts below are selected from a list of 228 Experts worldwide ranked by ideXlab platform
Edward H. Glaessgen - One of the best experts on this subject based on the ideXlab platform.
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Multiscale modeling of Intergranular Fracture in aluminum: constitutive relation for interface debonding
Journal of Materials Science, 2008Co-Authors: V Yamakov, Erik Saether, Edward H. GlaessgenAbstract:Intergranular Fracture is a dominant mode of failure in ultrafine grained materials. In the present study, the atomistic mechanisms of grain-boundary debonding during Intergranular Fracture in aluminum are modeled using a coupled molecular dynamics—finite element simulation. Using a statistical mechanics approach, a cohesive-zone law in the form of a traction–displacement constitutive relationship, characterizing the load transfer across the plane of a growing edge crack, is extracted from atomistic simulations and then recast in a form suitable for inclusion within a continuum finite element model. The cohesive-zone law derived by the presented technique is free of finite size effects and is statistically representative for describing the interfacial debonding of a grain boundary (GB) interface examined at atomic length scales. By incorporating the cohesive-zone law in cohesive-zone finite elements, the debonding of a GB interface can be simulated in a coupled continuum–atomistic model, in which a crack starts in the continuum environment, smoothly penetrates the continuum–atomistic interface, and continues its propagation in the atomistic environment. This study is a step toward relating atomistically derived decohesion laws to macroscopic predictions of Fracture and constructing multiscale models for nanocrystalline and ultrafine grained materials.
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molecular dynamics simulation based cohesive zone representation of Intergranular Fracture processes in aluminum
Journal of The Mechanics and Physics of Solids, 2006Co-Authors: V Yamakov, Dawn R. Phillips, Erik Saether, Edward H. GlaessgenAbstract:Abstract A traction–displacement relationship that may be embedded into a cohesive zone model for microscale problems of Intergranular Fracture is extracted from atomistic molecular-dynamics (MD) simulations. An MD model for crack propagation under steady-state conditions is developed to analyze Intergranular Fracture along a flat Σ 99 [1 1 0] symmetric tilt grain boundary in aluminum. Under hydrostatic tensile load, the simulation reveals asymmetric crack propagation in the two opposite directions along the grain boundary. In one direction, the crack propagates in a brittle manner by cleavage with very little or no dislocation emission, and in the other direction, the propagation is ductile through the mechanism of deformation twinning. This behavior is consistent with the Rice criterion for cleavage vs. dislocation blunting transition at the crack tip. The preference for twinning to dislocation slip is in agreement with the predictions of the Tadmor and Hai criterion. A comparison with finite element calculations shows that while the stress field around the brittle crack tip follows the expected elastic solution for the given boundary conditions of the model, the stress field around the twinning crack tip has a strong plastic contribution. Through the definition of a Cohesive-Zone-Volume-Element—an atomistic analog to a continuum cohesive zone model element—the results from the MD simulation are recast to obtain an average continuum traction–displacement relationship to represent cohesive zone interaction along a characteristic length of the grain boundary interface for the cases of ductile and brittle decohesion.
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molecular dynamics simulation based cohesive zone representation of Intergranular Fracture processes in aluminum
Journal of The Mechanics and Physics of Solids, 2006Co-Authors: V Yamakov, Dawn R. Phillips, Erik Saether, Edward H. GlaessgenAbstract:Abstract A traction–displacement relationship that may be embedded into a cohesive zone model for microscale problems of Intergranular Fracture is extracted from atomistic molecular-dynamics (MD) simulations. An MD model for crack propagation under steady-state conditions is developed to analyze Intergranular Fracture along a flat Σ 99 [1 1 0] symmetric tilt grain boundary in aluminum. Under hydrostatic tensile load, the simulation reveals asymmetric crack propagation in the two opposite directions along the grain boundary. In one direction, the crack propagates in a brittle manner by cleavage with very little or no dislocation emission, and in the other direction, the propagation is ductile through the mechanism of deformation twinning. This behavior is consistent with the Rice criterion for cleavage vs. dislocation blunting transition at the crack tip. The preference for twinning to dislocation slip is in agreement with the predictions of the Tadmor and Hai criterion. A comparison with finite element calculations shows that while the stress field around the brittle crack tip follows the expected elastic solution for the given boundary conditions of the model, the stress field around the twinning crack tip has a strong plastic contribution. Through the definition of a Cohesive-Zone-Volume-Element—an atomistic analog to a continuum cohesive zone model element—the results from the MD simulation are recast to obtain an average continuum traction–displacement relationship to represent cohesive zone interaction along a characteristic length of the grain boundary interface for the cases of ductile and brittle decohesion.
V Yamakov - One of the best experts on this subject based on the ideXlab platform.
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Multiscale modeling of Intergranular Fracture in aluminum: constitutive relation for interface debonding
Journal of Materials Science, 2008Co-Authors: V Yamakov, Erik Saether, Edward H. GlaessgenAbstract:Intergranular Fracture is a dominant mode of failure in ultrafine grained materials. In the present study, the atomistic mechanisms of grain-boundary debonding during Intergranular Fracture in aluminum are modeled using a coupled molecular dynamics—finite element simulation. Using a statistical mechanics approach, a cohesive-zone law in the form of a traction–displacement constitutive relationship, characterizing the load transfer across the plane of a growing edge crack, is extracted from atomistic simulations and then recast in a form suitable for inclusion within a continuum finite element model. The cohesive-zone law derived by the presented technique is free of finite size effects and is statistically representative for describing the interfacial debonding of a grain boundary (GB) interface examined at atomic length scales. By incorporating the cohesive-zone law in cohesive-zone finite elements, the debonding of a GB interface can be simulated in a coupled continuum–atomistic model, in which a crack starts in the continuum environment, smoothly penetrates the continuum–atomistic interface, and continues its propagation in the atomistic environment. This study is a step toward relating atomistically derived decohesion laws to macroscopic predictions of Fracture and constructing multiscale models for nanocrystalline and ultrafine grained materials.
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molecular dynamics simulation based cohesive zone representation of Intergranular Fracture processes in aluminum
Journal of The Mechanics and Physics of Solids, 2006Co-Authors: V Yamakov, Dawn R. Phillips, Erik Saether, Edward H. GlaessgenAbstract:Abstract A traction–displacement relationship that may be embedded into a cohesive zone model for microscale problems of Intergranular Fracture is extracted from atomistic molecular-dynamics (MD) simulations. An MD model for crack propagation under steady-state conditions is developed to analyze Intergranular Fracture along a flat Σ 99 [1 1 0] symmetric tilt grain boundary in aluminum. Under hydrostatic tensile load, the simulation reveals asymmetric crack propagation in the two opposite directions along the grain boundary. In one direction, the crack propagates in a brittle manner by cleavage with very little or no dislocation emission, and in the other direction, the propagation is ductile through the mechanism of deformation twinning. This behavior is consistent with the Rice criterion for cleavage vs. dislocation blunting transition at the crack tip. The preference for twinning to dislocation slip is in agreement with the predictions of the Tadmor and Hai criterion. A comparison with finite element calculations shows that while the stress field around the brittle crack tip follows the expected elastic solution for the given boundary conditions of the model, the stress field around the twinning crack tip has a strong plastic contribution. Through the definition of a Cohesive-Zone-Volume-Element—an atomistic analog to a continuum cohesive zone model element—the results from the MD simulation are recast to obtain an average continuum traction–displacement relationship to represent cohesive zone interaction along a characteristic length of the grain boundary interface for the cases of ductile and brittle decohesion.
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molecular dynamics simulation based cohesive zone representation of Intergranular Fracture processes in aluminum
Journal of The Mechanics and Physics of Solids, 2006Co-Authors: V Yamakov, Dawn R. Phillips, Erik Saether, Edward H. GlaessgenAbstract:Abstract A traction–displacement relationship that may be embedded into a cohesive zone model for microscale problems of Intergranular Fracture is extracted from atomistic molecular-dynamics (MD) simulations. An MD model for crack propagation under steady-state conditions is developed to analyze Intergranular Fracture along a flat Σ 99 [1 1 0] symmetric tilt grain boundary in aluminum. Under hydrostatic tensile load, the simulation reveals asymmetric crack propagation in the two opposite directions along the grain boundary. In one direction, the crack propagates in a brittle manner by cleavage with very little or no dislocation emission, and in the other direction, the propagation is ductile through the mechanism of deformation twinning. This behavior is consistent with the Rice criterion for cleavage vs. dislocation blunting transition at the crack tip. The preference for twinning to dislocation slip is in agreement with the predictions of the Tadmor and Hai criterion. A comparison with finite element calculations shows that while the stress field around the brittle crack tip follows the expected elastic solution for the given boundary conditions of the model, the stress field around the twinning crack tip has a strong plastic contribution. Through the definition of a Cohesive-Zone-Volume-Element—an atomistic analog to a continuum cohesive zone model element—the results from the MD simulation are recast to obtain an average continuum traction–displacement relationship to represent cohesive zone interaction along a characteristic length of the grain boundary interface for the cases of ductile and brittle decohesion.
Erik Saether - One of the best experts on this subject based on the ideXlab platform.
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Multiscale modeling of Intergranular Fracture in aluminum: constitutive relation for interface debonding
Journal of Materials Science, 2008Co-Authors: V Yamakov, Erik Saether, Edward H. GlaessgenAbstract:Intergranular Fracture is a dominant mode of failure in ultrafine grained materials. In the present study, the atomistic mechanisms of grain-boundary debonding during Intergranular Fracture in aluminum are modeled using a coupled molecular dynamics—finite element simulation. Using a statistical mechanics approach, a cohesive-zone law in the form of a traction–displacement constitutive relationship, characterizing the load transfer across the plane of a growing edge crack, is extracted from atomistic simulations and then recast in a form suitable for inclusion within a continuum finite element model. The cohesive-zone law derived by the presented technique is free of finite size effects and is statistically representative for describing the interfacial debonding of a grain boundary (GB) interface examined at atomic length scales. By incorporating the cohesive-zone law in cohesive-zone finite elements, the debonding of a GB interface can be simulated in a coupled continuum–atomistic model, in which a crack starts in the continuum environment, smoothly penetrates the continuum–atomistic interface, and continues its propagation in the atomistic environment. This study is a step toward relating atomistically derived decohesion laws to macroscopic predictions of Fracture and constructing multiscale models for nanocrystalline and ultrafine grained materials.
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molecular dynamics simulation based cohesive zone representation of Intergranular Fracture processes in aluminum
Journal of The Mechanics and Physics of Solids, 2006Co-Authors: V Yamakov, Dawn R. Phillips, Erik Saether, Edward H. GlaessgenAbstract:Abstract A traction–displacement relationship that may be embedded into a cohesive zone model for microscale problems of Intergranular Fracture is extracted from atomistic molecular-dynamics (MD) simulations. An MD model for crack propagation under steady-state conditions is developed to analyze Intergranular Fracture along a flat Σ 99 [1 1 0] symmetric tilt grain boundary in aluminum. Under hydrostatic tensile load, the simulation reveals asymmetric crack propagation in the two opposite directions along the grain boundary. In one direction, the crack propagates in a brittle manner by cleavage with very little or no dislocation emission, and in the other direction, the propagation is ductile through the mechanism of deformation twinning. This behavior is consistent with the Rice criterion for cleavage vs. dislocation blunting transition at the crack tip. The preference for twinning to dislocation slip is in agreement with the predictions of the Tadmor and Hai criterion. A comparison with finite element calculations shows that while the stress field around the brittle crack tip follows the expected elastic solution for the given boundary conditions of the model, the stress field around the twinning crack tip has a strong plastic contribution. Through the definition of a Cohesive-Zone-Volume-Element—an atomistic analog to a continuum cohesive zone model element—the results from the MD simulation are recast to obtain an average continuum traction–displacement relationship to represent cohesive zone interaction along a characteristic length of the grain boundary interface for the cases of ductile and brittle decohesion.
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molecular dynamics simulation based cohesive zone representation of Intergranular Fracture processes in aluminum
Journal of The Mechanics and Physics of Solids, 2006Co-Authors: V Yamakov, Dawn R. Phillips, Erik Saether, Edward H. GlaessgenAbstract:Abstract A traction–displacement relationship that may be embedded into a cohesive zone model for microscale problems of Intergranular Fracture is extracted from atomistic molecular-dynamics (MD) simulations. An MD model for crack propagation under steady-state conditions is developed to analyze Intergranular Fracture along a flat Σ 99 [1 1 0] symmetric tilt grain boundary in aluminum. Under hydrostatic tensile load, the simulation reveals asymmetric crack propagation in the two opposite directions along the grain boundary. In one direction, the crack propagates in a brittle manner by cleavage with very little or no dislocation emission, and in the other direction, the propagation is ductile through the mechanism of deformation twinning. This behavior is consistent with the Rice criterion for cleavage vs. dislocation blunting transition at the crack tip. The preference for twinning to dislocation slip is in agreement with the predictions of the Tadmor and Hai criterion. A comparison with finite element calculations shows that while the stress field around the brittle crack tip follows the expected elastic solution for the given boundary conditions of the model, the stress field around the twinning crack tip has a strong plastic contribution. Through the definition of a Cohesive-Zone-Volume-Element—an atomistic analog to a continuum cohesive zone model element—the results from the MD simulation are recast to obtain an average continuum traction–displacement relationship to represent cohesive zone interaction along a characteristic length of the grain boundary interface for the cases of ductile and brittle decohesion.
R O Ritchie - One of the best experts on this subject based on the ideXlab platform.
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on the toughening of brittle materials by grain bridging promoting Intergranular Fracture through grain angle strength and toughness
Lawrence Berkeley National Laboratory, 2008Co-Authors: J W Foulk, G C Johnson, Patrick A Klein, R O RitchieAbstract:The structural reliability of many brittle materials such as structural ceramics relies on the occurrence of Intergranular, as opposed to transgranular, Fracture in order to induce toughening by grain bridging. For a constant grain boundary strength and grain boundary toughness, the current work examines the role of grain strength, grain toughness, and grain angle in promoting Intergranular Fracture in order to maintain such toughening. Previous studies have illustrated that an Intergranular path and the consequent grain bridging process can be partitioned into five distinct regimes, namely: propagate, kink, arrest, stall and bridge. To determine the validity of the assumed Intergranular path, the classical penentration/deflection problem of a crack impinging on an interface is reexamined within a cohesive zone framework for Intergranular and transgranular Fracture. Results considering both modes of propagation, i.e., a transgranular and Intergranular path, reveal that crack-tip shielding is a natural outcome of the cohesive zone approach to Fracture. Cohesive zone growth in one mode shields the opposing mode from the stresses required for cohesive zone initiation. Although stable propagation occurs when the required driving force is equivalent to the toughness for either transgranular or Intergranular Fracture, the mode of propagation depends on the normalized grain strength, normalized grain toughness, and grain angle. For each grain angle, the intersection of single path and multiple path solutions demarcates strong grains that increase the macroscopic toughness and weak grains that decrease it. The unstable transition to Intergranular Fracture reveals that an increasing grain toughness requires a growing region of the transgranular cohesive zone be at and near the peak cohesive strength. The inability of the body to provide the requisite stress field yields an overdriven and unstable configuration. The current results provide restrictions for the achievement of substantial toughening through Intergranular Fracture.
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on the toughening of brittle materials by grain bridging promoting Intergranular Fracture through grain angle strength and toughness
Journal of The Mechanics and Physics of Solids, 2008Co-Authors: J W Foulk, G C Johnson, Patrick A Klein, R O RitchieAbstract:Abstract The structural reliability of many brittle materials such as structural ceramics relies on the occurrence of Intergranular, as opposed to transgranular, Fracture in order to induce toughening by grain bridging. For a constant grain boundary strength and grain boundary toughness, the current work examines the role of grain strength, grain toughness, and grain angle in promoting Intergranular Fracture in order to maintain such toughening. Previous studies have illustrated that an Intergranular path and the consequent grain bridging process can be partitioned into five distinct regimes, namely: propagate, kink, arrest, stall, and bridge. To determine the validity of the assumed Intergranular path, the classical penetration/deflection problem of a crack impinging on an interface is re-examined within a cohesive zone framework for Intergranular and transgranular Fracture. Results considering both modes of propagation, i.e., a transgranular and Intergranular path, reveal that crack-tip shielding is a natural outcome of the cohesive zone approach to Fracture. Cohesive zone growth in one mode shields the opposing mode from the stresses required for cohesive zone initiation. Although stable propagation occurs when the required driving force is equivalent to the toughness for either transgranular or Intergranular Fracture, the mode of propagation depends on the normalized grain strength, normalized grain toughness, and grain angle. For each grain angle, the intersection of single path and multiple path solutions demarcates “strong” grains that increase the macroscopic toughness and “weak” grains that decrease it. The unstable transition to Intergranular Fracture reveals that an increasing grain toughness requires a growing region of the transgranular cohesive zone be near the cohesive strength. The inability of the body to provide the requisite stress field yields an overdriven and unstable configuration. The current results provide restrictions for the achievement of substantial toughening through Intergranular Fracture.
Dawn R. Phillips - One of the best experts on this subject based on the ideXlab platform.
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molecular dynamics simulation based cohesive zone representation of Intergranular Fracture processes in aluminum
Journal of The Mechanics and Physics of Solids, 2006Co-Authors: V Yamakov, Dawn R. Phillips, Erik Saether, Edward H. GlaessgenAbstract:Abstract A traction–displacement relationship that may be embedded into a cohesive zone model for microscale problems of Intergranular Fracture is extracted from atomistic molecular-dynamics (MD) simulations. An MD model for crack propagation under steady-state conditions is developed to analyze Intergranular Fracture along a flat Σ 99 [1 1 0] symmetric tilt grain boundary in aluminum. Under hydrostatic tensile load, the simulation reveals asymmetric crack propagation in the two opposite directions along the grain boundary. In one direction, the crack propagates in a brittle manner by cleavage with very little or no dislocation emission, and in the other direction, the propagation is ductile through the mechanism of deformation twinning. This behavior is consistent with the Rice criterion for cleavage vs. dislocation blunting transition at the crack tip. The preference for twinning to dislocation slip is in agreement with the predictions of the Tadmor and Hai criterion. A comparison with finite element calculations shows that while the stress field around the brittle crack tip follows the expected elastic solution for the given boundary conditions of the model, the stress field around the twinning crack tip has a strong plastic contribution. Through the definition of a Cohesive-Zone-Volume-Element—an atomistic analog to a continuum cohesive zone model element—the results from the MD simulation are recast to obtain an average continuum traction–displacement relationship to represent cohesive zone interaction along a characteristic length of the grain boundary interface for the cases of ductile and brittle decohesion.
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molecular dynamics simulation based cohesive zone representation of Intergranular Fracture processes in aluminum
Journal of The Mechanics and Physics of Solids, 2006Co-Authors: V Yamakov, Dawn R. Phillips, Erik Saether, Edward H. GlaessgenAbstract:Abstract A traction–displacement relationship that may be embedded into a cohesive zone model for microscale problems of Intergranular Fracture is extracted from atomistic molecular-dynamics (MD) simulations. An MD model for crack propagation under steady-state conditions is developed to analyze Intergranular Fracture along a flat Σ 99 [1 1 0] symmetric tilt grain boundary in aluminum. Under hydrostatic tensile load, the simulation reveals asymmetric crack propagation in the two opposite directions along the grain boundary. In one direction, the crack propagates in a brittle manner by cleavage with very little or no dislocation emission, and in the other direction, the propagation is ductile through the mechanism of deformation twinning. This behavior is consistent with the Rice criterion for cleavage vs. dislocation blunting transition at the crack tip. The preference for twinning to dislocation slip is in agreement with the predictions of the Tadmor and Hai criterion. A comparison with finite element calculations shows that while the stress field around the brittle crack tip follows the expected elastic solution for the given boundary conditions of the model, the stress field around the twinning crack tip has a strong plastic contribution. Through the definition of a Cohesive-Zone-Volume-Element—an atomistic analog to a continuum cohesive zone model element—the results from the MD simulation are recast to obtain an average continuum traction–displacement relationship to represent cohesive zone interaction along a characteristic length of the grain boundary interface for the cases of ductile and brittle decohesion.