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J W Ju - One of the best experts on this subject based on the ideXlab platform.
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a micromechanical damage model for effective elastoPlastic behavior of partially debonded ductile matrix composites
International Journal of Solids and Structures, 2001Co-Authors: J W JuAbstract:Abstract A micromechanical damage model considering progressive partial debonding is presented to investigate the effective elastoPlastic-damage behavior of partially debonded particle reinforced ductile matrix composites (PRDMCs). The effective, evolutionary elastoPlastic-damage responses of three-phase composites, consisting of perfectly bonded spherical particles, partially debonded particles and a ductile matrix, are micromechanically derived on the basis of the ensemble-volume averaging procedure and the first-order effects of eigenstrains. The effects of random dispersion of particles are accommodated. Further, the evolutionary partial debonding mechanism is governed by the internal stresses of spherical particles and the statistical behavior of the interfacial strength. Specifically, following Zhao and Weng (1996) , a partially debonded elastic spherical isotropic inclusion is replaced by an equivalent, transversely isotropic yet perfectly bonded elastic spherical inclusion. The Weibull's probabilistic function is employed to describe the varying probability of progressive partial particle debonding. The proposed effective yield criterion, together with the assumed overall associative Plastic Flow Rule and the hardening law, forms the analytical framework for the estimation of the effective elastoPlastic-damage behavior of ductile matrix composites. Finally, the present predictions are compared with the predictions based on Ju and Lee's (2000) complete particle debonding model, other existing numerical predictions, and available experimental data. It is observed that the effects of partially debonded particles on the stress–strain responses are significant when the damage evolution becomes rapid.
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a micromechanical damage model for effective elastoPlastic behavior of ductile matrix composites considering evolutionary complete particle debonding
Computer Methods in Applied Mechanics and Engineering, 2000Co-Authors: J W JuAbstract:A micromechanical damage model is presented to predict the overall elastoPlastic behavior and damage evolution in ductile matrix composites. The effective elastic moduli of three-phase composites are predicted by a micromechanical formulation. To estimate the overall elastoPlastic-damage responses, an effective yield criterion is derived based on the ensemble-volume averaging process and the first-order effects of eigenstrains due to the existence of spherical inclusions. The effects of random dispersion of inclusions are accommodated. The proposed effective yield criterion, together with the assumed overall associative Plastic Flow Rule and the hardening law, constitutes the analytical foundation for the estimation of effective elastoPlastic behavior of ductile matrix composites. An evolutionary interfacial particle debonding model is subsequently considered in accordance with the Weibull's statistical function to describe the varying probability of complete particle debonding. The interfacial debonding process is controlled by internal stresses of particles and a Weibull interfacial strength parameter. The completely debonded particles are regarded as voids for simplicity. The proposed elastoPlastic-damage model is applied to the uniaxial, biaxial and triaxial tensile loadings to predict the various stress–strain responses. Efficient step-by-step iterative computational algorithms are also presented to implement the proposed damage model. Furthermore, the present predictions under various loading conditions are compared with other theoretical predictions and some available experimental data with modest particle concentrations.
Jian-fu Shao - One of the best experts on this subject based on the ideXlab platform.
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a micromechanics based elastoPlastic damage model for rocks with a brittle ductile transition in mechanical response
Rock Mechanics and Rock Engineering, 2018Co-Authors: Qizhi Zhu, Jian-fu Shao, Liang Chen, Jian LiuAbstract:As confining pressure increases, crystalline rocks of moderate porosity usually undergo a transition in failure mode from localized brittle fracture to diffused damage and ductile failure. This transition has been widely reported experimentally for several decades; however, satisfactory modeling is still lacking. The present paper aims at modeling the brittle–ductile transition process of rocks under conventional triaxial compression. Based on quantitative analyses of experimental results, it is found that there is a quite satisfactory linearity between the axial inelastic strain at failure and the confining pressure prescribed. A micromechanics-based frictional damage model is then formulated using an associated Plastic Flow Rule and a strain energy release rate-based damage criterion. The analytical solution to the strong Plasticity-damage coupling problem is provided and applied to simulate the nonlinear mechanical behaviors of Tennessee marble, Indiana limestone and Jinping marble, each presenting a brittle–ductile transition in stress–strain curves.
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A micromechanics-based elastoPlastic damage model for granular materials at low confining pressure
International Journal of Plasticity, 2010Co-Authors: Qizhi Zhu, Jian-fu Shao, M. MainguyAbstract:This paper is devoted to the formulation of a micromechanics-based constitutive model for granular materials under relatively low confining pressure. The constitutive formulation is performed within the general framework of homogenization for granular materials. However, new rigorous stress localization laws are proposed. Some local constitutive relations are established under the consideration of irreversible thermodynamics. Macroscopic Plastic deformation is obtained by considering local Plastic sliding in a limit number of families of contact planes. The Plastic sliding at each contact plane is described by a non-associated Plastic Flow Rule, taking into account pressure sensitivity and normal dilatancy. Nonlinear elastic deformation related to progressive compaction of contacts is also taken into account. Material softening is described by involving damage process related to degradation of microstructure fabric. The proposed model is applied to some typical granular materials (sands). The numerical predictions are compared with experimental data.
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a coupled elastoPlastic damage model for semi brittle materials and extension to unsaturated conditions
Mechanics of Materials, 2006Co-Authors: Jian-fu Shao, Djimedo Kondo, Yun Jia, Annesophie ChiarelliAbstract:In this paper, a coupled elastoPlastic damage model is proposed for semi-brittle materials. This model is applied to a specific semi-brittle sedimentary rock material. A brief account of experimental investigations is presented in the first part. The data obtained show an important Plastic deformation coupled with stress-induced damage corresponding to initiation and growth of microcracks. Influences of mineral compositions and water content on the mechanical behaviour are also investigated. Based on these experimental evidences, the general formulation of the model is presented in the second part of the paper. The effective elastic properties of isotropic damaged material are determined based on relevant considerations from micromechanics. Damage evolution law and Plastic damage coupling are described by using the framework of irreversible thermodynamics. A non-associated Plastic Flow Rule is used. The model is extended to partially saturated conditions in order to study coupled hydromechanical behaviours in drying–wetting processes. Comparisons between numerical simulations and test data are performed for various loading paths. It is shown that the proposed model is able to describe the main features of mechanical behaviour observed in this class of materials.
Djimedo Kondo - One of the best experts on this subject based on the ideXlab platform.
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Limit analysis and homogenization of porous materials with Mohr-Coulomb matrix. Part I: theoretical formulation
Journal of the Mechanics and Physics of Solids, 2016Co-Authors: Kokou Anoukou, Franck Pastor, Philippe Dufrenoy, Djimedo KondoAbstract:The present two-part study aims at investigating the specific effects of Mohr-Coulomb matrix on the strength of ductile porous materials by using a kinematic limit analysis approach. While in the Part II, static and kinematic bounds are numerically derived and used for validation purpose, the present Part I focuses on the theoretical formulation of a macroscopic strength criterion for porous Mohr-Coulomb materials. To this end, we consider a hollow sphere model with a rigid perfectly Plastic Mohr-Coulomb matrix, subjected to axisymmetric uniform strain rate boundary conditions. Taking advantage of an appropriate family of three-parameter trial velocity fields accounting for the specific Plastic deformation mechanisms of the Mohr-Coulomb matrix, we then provide a solution of the constrained minimization problem required for the determination of the macroscopic dissipation function. The macroscopic strength criterion is then obtained by means of the Lagrangian method combined with Karush-Kuhn-Tucker conditions. After a careful analysis and discussion of the Plastic admissibility condition associated to the Mohr-Coulomb criterion, the above procedure leads to a parametric closed-form expression of the macroscopic strength criterion. The later explicitly shows a dependence on the three stress invariants. In the special case of a friction angle equal to zero, the established criterion reduced to recently available results for porous Tresca materials. Finally, both effects of matrix friction angle and porosity are briefly illustrated and, for completeness, the macroscopic Plastic Flow Rule and the voids evolution law are fully furnished.
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a coupled elastoPlastic damage model for semi brittle materials and extension to unsaturated conditions
Mechanics of Materials, 2006Co-Authors: Jian-fu Shao, Djimedo Kondo, Yun Jia, Annesophie ChiarelliAbstract:In this paper, a coupled elastoPlastic damage model is proposed for semi-brittle materials. This model is applied to a specific semi-brittle sedimentary rock material. A brief account of experimental investigations is presented in the first part. The data obtained show an important Plastic deformation coupled with stress-induced damage corresponding to initiation and growth of microcracks. Influences of mineral compositions and water content on the mechanical behaviour are also investigated. Based on these experimental evidences, the general formulation of the model is presented in the second part of the paper. The effective elastic properties of isotropic damaged material are determined based on relevant considerations from micromechanics. Damage evolution law and Plastic damage coupling are described by using the framework of irreversible thermodynamics. A non-associated Plastic Flow Rule is used. The model is extended to partially saturated conditions in order to study coupled hydromechanical behaviours in drying–wetting processes. Comparisons between numerical simulations and test data are performed for various loading paths. It is shown that the proposed model is able to describe the main features of mechanical behaviour observed in this class of materials.
Farid Abed-meraim - One of the best experts on this subject based on the ideXlab platform.
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An elasto-Plastic self-consistent model for damaged polycrystalline materials: Theoretical formulation and numerical implementation
Computer Methods in Applied Mechanics and Engineering, 2020Co-Authors: Joseph Paux, Farid Abed-meraim, Mohamed Ben Bettaieb, Houssem Badreddine, Carl Labergere, Khemais SaanouniAbstract:Elasto-Plastic multiscale approaches are known to be suitable to model the mechanical behavior of metallic materials during forming processes. These approaches are classically adopted to explicitly link relevant microstructural effects to the macroscopic behavior. This paper presents a finite strain elastoPlastic self-consistent model for damaged polycrystalline aggregates and its implementation into ABAQUS/Standard finite element (FE) code. Material degradation is modeled by the introduction of a scalar damage variable at each crystallographic slip system for each individual grain. The single crystal Plastic Flow is described by both the classical and a regularized version of the Schmid criterion. To integrate the single crystal constitutive equations, two new numerical algorithms are developed (one for each Plastic Flow Rule). Then, the proposed single crystal modeling is embedded into the self-consistent scheme to predict the mechanical behavior of elasto-Plastic polycrystalline aggregates in the finite strain range. This strategy is implemented into ABAQUS/Standard FE code through a user-defined material (UMAT) subroutine. Special attention is paid to the satisfaction of the incremental objectivity and the efficiency of the convergence of the global resolution scheme, related to the computation of the consistent tangent modulus. The capability of the new constitutive modeling to capture the interaction between the damage evolution and the microstructural properties is highlighted through several simulations at both single crystal and polycrystalline scales. It appears from the numerical tests that the use of the classical Schmid criterion leads to a poor numerical convergence of the self-consistent scheme (due to the abrupt changes in the activity of the slip systems), which sometimes causes the computations to be prematurely stopped. By contrast, the use of the regularized version of the Schmid law allows a better convergence of the self-consistent approach, but induces an important increase in the computation time devoted to the integration of the single crystal constitutive equations (because of the high value of the power-law exponent used to regularize the Schmid yield function). To avoid these difficulties, a numerical strategy is built to combine the benefits of the two approaches: the classical Schmid criterion is used to integrate the single crystal constitutive equations, while its regularized version is used to compute the microscopic tangent modulus required for solving the self-consistent equations. The robustness and the accuracy of this novel numerical strategy are particularly analyzed through several numerical simulations (prediction of the mechanical behavior of polycrystalline aggregates and simulation of a circular cup-drawing forming process).
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Formability prediction of substrate-supported metal layers using a non-associated Plastic Flow Rule
Journal of Materials Processing Technology, 2020Co-Authors: Mohamed Ben Bettaieb, Farid Abed-meraimAbstract:When manufacturing flexible devices, it is quite common that localized necking appears due to the low ductility of the metal sheets used. To delay the inception of such localized necking, several industrial companies have proposed a promising technical solution based on the bonding of elastomer substrates to the metal sheets used in the manufacturing processes. In this context, the comprehensive numerical understanding of the impact of such substrate coating on the improvement of the ductility of elastomer-supported metal layers still remains a challenging goal. To achieve this goal, the bifurcation approach as well as the Marciniak and Kuczynski model are used to predict the occurrence of localized necking. The mechanical behavior of the metal layer is modeled by a non-associated anisotropic Plasticity model. The adoption of non-associated Plastic Flow Rule allows separating the description of the Plastic potential from that of the yield function, which is essential to accurately model strong Plastic anisotropy characterizing cold-rolled sheets. As to the elastomer substrate, its mechanical behavior is described by a neo-Hookean law. The paper presents a variety of numerical results relating to the prediction of Plastic strain localization in both freestanding and elastomercoated metal layers. The effects of the non-associativity of the Plastic Flow Rule for the metal layer and the addition of an elastomer substrate on the predictions of localized necking are especially underlined. It is shown that the ductility limits predicted by the non-associated elasto-Plastic model are lower than their counterparts determined by an associated Plasticity model. It is also proven that adhering an elastomer layer to the metal layer can substantially delay the initiation of Plastic strain localization.
Khemais Saanouni - One of the best experts on this subject based on the ideXlab platform.
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An elasto-Plastic self-consistent model for damaged polycrystalline materials: Theoretical formulation and numerical implementation
Computer Methods in Applied Mechanics and Engineering, 2020Co-Authors: Joseph Paux, Farid Abed-meraim, Mohamed Ben Bettaieb, Houssem Badreddine, Carl Labergere, Khemais SaanouniAbstract:Elasto-Plastic multiscale approaches are known to be suitable to model the mechanical behavior of metallic materials during forming processes. These approaches are classically adopted to explicitly link relevant microstructural effects to the macroscopic behavior. This paper presents a finite strain elastoPlastic self-consistent model for damaged polycrystalline aggregates and its implementation into ABAQUS/Standard finite element (FE) code. Material degradation is modeled by the introduction of a scalar damage variable at each crystallographic slip system for each individual grain. The single crystal Plastic Flow is described by both the classical and a regularized version of the Schmid criterion. To integrate the single crystal constitutive equations, two new numerical algorithms are developed (one for each Plastic Flow Rule). Then, the proposed single crystal modeling is embedded into the self-consistent scheme to predict the mechanical behavior of elasto-Plastic polycrystalline aggregates in the finite strain range. This strategy is implemented into ABAQUS/Standard FE code through a user-defined material (UMAT) subroutine. Special attention is paid to the satisfaction of the incremental objectivity and the efficiency of the convergence of the global resolution scheme, related to the computation of the consistent tangent modulus. The capability of the new constitutive modeling to capture the interaction between the damage evolution and the microstructural properties is highlighted through several simulations at both single crystal and polycrystalline scales. It appears from the numerical tests that the use of the classical Schmid criterion leads to a poor numerical convergence of the self-consistent scheme (due to the abrupt changes in the activity of the slip systems), which sometimes causes the computations to be prematurely stopped. By contrast, the use of the regularized version of the Schmid law allows a better convergence of the self-consistent approach, but induces an important increase in the computation time devoted to the integration of the single crystal constitutive equations (because of the high value of the power-law exponent used to regularize the Schmid yield function). To avoid these difficulties, a numerical strategy is built to combine the benefits of the two approaches: the classical Schmid criterion is used to integrate the single crystal constitutive equations, while its regularized version is used to compute the microscopic tangent modulus required for solving the self-consistent equations. The robustness and the accuracy of this novel numerical strategy are particularly analyzed through several numerical simulations (prediction of the mechanical behavior of polycrystalline aggregates and simulation of a circular cup-drawing forming process).