The Experts below are selected from a list of 117 Experts worldwide ranked by ideXlab platform
Maosong Huang - One of the best experts on this subject based on the ideXlab platform.
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regularized finite element modeling of progressive failure in soils within nonlocal Softening Plasticity
Computational Mechanics, 2018Co-Authors: Maosong HuangAbstract:By solving a nonlinear complementarity problem for the consistency condition, an improved implicit stress return iterative algorithm for a generalized over-nonlocal strain Softening Plasticity was proposed, and the consistent tangent matrix was obtained. The proposed algorithm was embodied into existing finite element codes, and it enables the nonlocal regularization of ill-posed boundary value problem caused by the pressure independent and dependent strain Softening Plasticity. The algorithm was verified by the numerical modeling of strain localization in a plane strain compression test. The results showed that a fast convergence can be achieved and the mesh-dependency caused by strain Softening can be effectively eliminated. The influences of hardening modulus and material characteristic length on the simulation were obtained. The proposed algorithm was further used in the simulations of the bearing capacity of a strip footing; the results are mesh-independent, and the progressive failure process of the soil was well captured.
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Numerical solutions of strain localization with nonlocal Softening Plasticity
Computer Methods in Applied Mechanics and Engineering, 2009Co-Authors: Xilin Lu, Jean-pierre Bardet, Maosong HuangAbstract:Abstract Softening Plasticity, when it is deprived of a characteristic length, often leads to boundary value problems that are ill-posed and produce unreliable numerical solutions. As meshes are refined, plastic strains localize into bands that become narrower and narrower, and generate load–displacement responses with excessive Softening, which may even degenerate into unrealistic snapbacks. In the case of discrete systems, the underlying reasons for this poor numerical performance can be examined using a spectral analysis of the tangential stiffness matrix derived from incremental equilibrium equations. In one-dimensional boundary-valued problems, the introduction of a weak Softening element into a mesh of elasto-plastic elements produces a dominant eigenvector that clearly exhibits a strain localization width directly related to the weak element size. The dominant eigenvector that controls the incremental solution varies spuriously when the mesh is refined, which results in mesh dependency. Over-nonlocal Softening Plasticity introduces a length scale, forces more elements to become plastic, and preserves the width of the plastic zone when the mesh is refined. When one-dimensional meshes are refined, spectral analysis shows that the dominant eigenvector does not vary erratically, and that its deformation patterns are smooth and display a constant localization width. This explains why the spatial distribution of plastic strains and the global load–displacement responses converge to analytical solutions in one dimension. The generalization to higher dimensions will be the object of future studies.
Paulo B Lourenco - One of the best experts on this subject based on the ideXlab platform.
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a plane stress Softening Plasticity model for orthotropic materials
International Journal for Numerical Methods in Engineering, 1997Co-Authors: Rene De Borst, Paulo B Lourenco, J G RotsAbstract:A plane stress model has been developed for quasi-brittle orthotropic materials. The theory of Plasticity, which is adopted to describe the inelastic behaviour, utilizes modern algorithmic concepts, including an implicit Euler backward return mapping scheme, a local Newton-Raphson method and a consistent tangential stiffness matrix. The model is capable of predicting independent responses along the material axes. It features a tensile fracture energy and a compressive fracture energy, which are different for each material axis. A comparison between calculated and experimental results in masonry shear walls shows that a successful implementation has been achieved. © 1997 John Wiley & Sons, Ltd.
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multisurface interface model for analysis of masonry structures
Journal of Engineering Mechanics-asce, 1997Co-Authors: Paulo B Lourenco, J G RotsAbstract:The performance of an interface elastoplastic constitutive model for the analysis of unreinforced masonry structures is evaluated. Both masonry components are discretized aiming at a rational unit-joint model able to describe cracking, slip, and crushing of the material. The model is formulated in the spirit of Softening Plasticity for tension, shear and compression, with consistent treatment of the intersections defined by these modes. The numerical implementation is based on modern algorithmic concepts such as local and global Newton-Raphson methods, implicit integration of the rate equations and consistent tangent stiffness matrices. The parameters necessary to define the model are derived from microexperiments in units, joints, and small masonry samples. The model is used to analyze masonry shear-walls and is capable of predicting the experimental collapse load and behaviour accurately. Detailed comparisons between experimental and numerical results permit a clear understanding of the walls structural behavior, flow of internal forces and redistribution of stresses both in the pre- and post-peak regime.
J G Rots - One of the best experts on this subject based on the ideXlab platform.
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a plane stress Softening Plasticity model for orthotropic materials
International Journal for Numerical Methods in Engineering, 1997Co-Authors: Rene De Borst, Paulo B Lourenco, J G RotsAbstract:A plane stress model has been developed for quasi-brittle orthotropic materials. The theory of Plasticity, which is adopted to describe the inelastic behaviour, utilizes modern algorithmic concepts, including an implicit Euler backward return mapping scheme, a local Newton-Raphson method and a consistent tangential stiffness matrix. The model is capable of predicting independent responses along the material axes. It features a tensile fracture energy and a compressive fracture energy, which are different for each material axis. A comparison between calculated and experimental results in masonry shear walls shows that a successful implementation has been achieved. © 1997 John Wiley & Sons, Ltd.
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multisurface interface model for analysis of masonry structures
Journal of Engineering Mechanics-asce, 1997Co-Authors: Paulo B Lourenco, J G RotsAbstract:The performance of an interface elastoplastic constitutive model for the analysis of unreinforced masonry structures is evaluated. Both masonry components are discretized aiming at a rational unit-joint model able to describe cracking, slip, and crushing of the material. The model is formulated in the spirit of Softening Plasticity for tension, shear and compression, with consistent treatment of the intersections defined by these modes. The numerical implementation is based on modern algorithmic concepts such as local and global Newton-Raphson methods, implicit integration of the rate equations and consistent tangent stiffness matrices. The parameters necessary to define the model are derived from microexperiments in units, joints, and small masonry samples. The model is used to analyze masonry shear-walls and is capable of predicting the experimental collapse load and behaviour accurately. Detailed comparisons between experimental and numerical results permit a clear understanding of the walls structural behavior, flow of internal forces and redistribution of stresses both in the pre- and post-peak regime.
Michael Kaliske - One of the best experts on this subject based on the ideXlab platform.
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a nonlocal Softening Plasticity based on microplane theory for concrete at finite strains
Computers & Structures, 2020Co-Authors: Bobby Rio Indriyantho, Imadeddin Zreid, Michael KaliskeAbstract:Abstract Parts of the irreversible response of materials can be described by a Plasticity approach. For modelling quasi-brittle materials such as concrete, the microplane approach is a powerful method. In order to predict the load–displacement as well as the stress–strain relation, numerous constitutive models developed for small strains have been used successfully. Nevertheless, for example, at high hydrostatic pressure, extremely large deformations occur even in concrete materials with no damage or voids. As consequence, the microplane-Plasticity model at small strains needs to be extended to the finite strain framework for largely deformed structures. The elastoplastic microplane approach based on the kinematic constraint of the volumetric-deviatoric split and the Drucker-Prager yield criterion at finite strains are implemented in the present work. Furthermore, due to strain localisation, an implicit gradient enhanced approach is applied in here to obtain stable and mesh insensitive solutions. Numerical examples including the comparison of simulated results to existing experimental data are provided to validate the proposed formulation.
M E Barkey - One of the best experts on this subject based on the ideXlab platform.
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a strain space nonlinear kinematic hardening Softening Plasticity model
International Journal of Plasticity, 1999Co-Authors: Haiyang Wang, M E BarkeyAbstract:Abstract A strain space Plasticity theory based on the nonlinear kinematic hardening and Softening rule is developed in order to accommodate work-hardening, work-Softening, and elastic-perfectly plastic materials with one set of constitutive equations, and to facilitate strain controlled calculations. A generalized hardening/Softening parameter is proposed, and the potential of linking the parameter to micro-mechanical material changes is discussed. The theory is used to investigate work-Softening materials numerically and highlights a need for additional experimental results in this area.