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Farid Abedmeraim - One of the best experts on this subject based on the ideXlab platform.
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localized necking predictions based on rate independent self consistent polycrystal plasticity bifurcation analysis versus Imperfection approach
International Journal of Plasticity, 2017Co-Authors: Holanyo K Akpama, Ben M Bettaieb, Farid AbedmeraimAbstract:Abstract The present study focuses on the development of a relevant numerical tool for predicting the onset of localized necking in polycrystalline aggregates. The latter are assumed to be representative of thin metal sheets. In this tool, a micromechanical model, based on the rate-independent self-consistent multi-scale scheme, is developed to accurately describe the mechanical behavior of polycrystalline aggregates from that of their single crystal constituents. In the current paper, the constitutive framework at the single crystal scale follows a finite strain formulation of the rate-independent theory of crystal elasto-plasticity. To predict the occurrence of localized necking in polycrystalline aggregates, this micromechanical modeling is combined with two main strain localization approaches: the bifurcation analysis and the Initial Imperfection method. The formulation of both strain localization indicators takes into consideration the plane stress conditions to which thin metal sheets are subjected during deformation. From a numerical point of view, strain localization analysis with this crystal plasticity approach can be viewed as a strongly non-linear problem. Hence, several numerical algorithms and techniques are developed and implemented in the aim of efficiently solving this non-linear problem. Various simulation results obtained by the application of the developed numerical tool are presented and extensively discussed. It is demonstrated from these results that the predictions obtained with the Marciniak–Kuczynski procedure tend towards those yielded by the bifurcation theory, when the Initial Imperfection ratio tends towards zero. Furthermore, the above result is shown to be valid for both scale-transition schemes, namely the full-constraint Taylor model and self-consistent scheme.
Holanyo K Akpama - One of the best experts on this subject based on the ideXlab platform.
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localized necking predictions based on rate independent self consistent polycrystal plasticity bifurcation analysis versus Imperfection approach
International Journal of Plasticity, 2017Co-Authors: Holanyo K Akpama, Ben M Bettaieb, Farid AbedmeraimAbstract:Abstract The present study focuses on the development of a relevant numerical tool for predicting the onset of localized necking in polycrystalline aggregates. The latter are assumed to be representative of thin metal sheets. In this tool, a micromechanical model, based on the rate-independent self-consistent multi-scale scheme, is developed to accurately describe the mechanical behavior of polycrystalline aggregates from that of their single crystal constituents. In the current paper, the constitutive framework at the single crystal scale follows a finite strain formulation of the rate-independent theory of crystal elasto-plasticity. To predict the occurrence of localized necking in polycrystalline aggregates, this micromechanical modeling is combined with two main strain localization approaches: the bifurcation analysis and the Initial Imperfection method. The formulation of both strain localization indicators takes into consideration the plane stress conditions to which thin metal sheets are subjected during deformation. From a numerical point of view, strain localization analysis with this crystal plasticity approach can be viewed as a strongly non-linear problem. Hence, several numerical algorithms and techniques are developed and implemented in the aim of efficiently solving this non-linear problem. Various simulation results obtained by the application of the developed numerical tool are presented and extensively discussed. It is demonstrated from these results that the predictions obtained with the Marciniak–Kuczynski procedure tend towards those yielded by the bifurcation theory, when the Initial Imperfection ratio tends towards zero. Furthermore, the above result is shown to be valid for both scale-transition schemes, namely the full-constraint Taylor model and self-consistent scheme.
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Prediction of Localized Necking Based on Crystal Plasticity: Comparison of Bifurcation and Imperfection Approaches
Key Engineering Materials, 2016Co-Authors: Holanyo K Akpama, Mohamed Ben Bettaieb, Farid Abed-meraimAbstract:In the present work, a powerful modeling tool is developed to predict and analyze the onset of strain localization in polycrystalline aggregates. The predictions of localized necking are based on two plastic instability criteria, namely the bifurcation theory and the Initial Imperfection approach. In this tool, a micromechanical model, based on the self-consistent scale-transition scheme, is used to accurately derive the mechanical behavior of polycrystalline aggregates from that of their microscopic constituents (the single crystals). The mechanical behavior of the single crystals is developed within a large strain rate-independent constitutive framework. This micromechanical constitutive modeling takes into account the essential microstructure-related features that are relevant at the microscale. These microstructural aspects include key physical mechanisms, such as Initial and induced crystallographic textures, morphological anisotropy and interactions between the grains and their surrounding medium. The developed tool is used to predict sheet metal formability through the concept of forming limit diagrams (FLDs). The results obtained by the self-consistent averaging scheme, in terms of predicted FLDs, are compared with those given by the more classical full-constraint Taylor model. Moreover, the predictions obtained by the Imperfection approach are systematically compared with those given by the bifurcation analysis, and it is demonstrated that the former tend to the latter in the limit of a vanishing size for the Initial Imperfection.
S.s.e. Lam - One of the best experts on this subject based on the ideXlab platform.
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Finite strip analysis of laminated plates with general Initial Imperfection under end shortening
Engineering Structures, 2001Co-Authors: Th H. Lui, S.s.e. LamAbstract:Abstract Description of a finite strip method is given for predicting the post-buckling response of rectangular laminated plates when subjected to progressive end shortening. Initial Imperfection in very general shape is also included. Polynomial expression is used to simulate the actual Imperfection along each nodal line while the deformations are represented by trigonometric series. The analysis, under the assumption that thin plates are used, is based on the classical plate theory. Geometric non-linearity is introduced in the strain-displacement equations in the manner of the von Karman assumptions. The Newton–Raphson method is used to solve the non-linear equilibrium equations. A number of applications involving both isotropic and laminated plates are described to investigate the effects of Initial Imperfection.
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post buckling analysis of a strut with general Initial Imperfection
International Journal for Numerical Methods in Engineering, 1998Co-Authors: S.s.e. LamAbstract:Computational procedure has been presented for the post-buckling analysis of a strut with Initial Imperfection when subjected to progressive end shortening. Polynomial expression in very general form is used to simulate the actual Initial Imperfection, while the deformations are expressed by suitable trigonometric series. Geometric non-linearity is introduced into the strain–displacement relations in a manner that is consistent with the von Karman assumptions. Non-linear equilibrium equations are solved by a Newton–Raphson procedure. Results are presented for cases with symmetric and non-symmetric Initial Imperfection. Good comparison with other solutions and experimental results is obtained in all applications. © 1998 John Wiley & Sons, Ltd.
Kikuo Ikarashi - One of the best experts on this subject based on the ideXlab platform.
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elastic buckling analysis of rigidly jointed single layer reticulated domes with random Initial Imperfection
International Journal of Space Structures, 1992Co-Authors: Toshiro Suzuki, Toshiyuki Ogawa, Kikuo IkarashiAbstract:In the present paper, the effect of Imperfection on the elastic buckling load and mode shapes of externally-loaded single layer reticulated domes is investigated. The types of buckling concerned here are the general buckling, the local (dimple) buckling and the buckling of a member. As to the geometric parameter of a dome, the slenderness factor S is adopted which represents the openness and slenderness of the dome. The maximum value of the Imperfection is assumed to be the normal random variable. The buckling loads are computed by the linear and the nonlinear buckling analysis using the finite element method. The statistical values are calculated by the three-points estimates method. The main points of interest are the influence of the shape and the extent of an Imperfection on the buckling load.
Ben M Bettaieb - One of the best experts on this subject based on the ideXlab platform.
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localized necking predictions based on rate independent self consistent polycrystal plasticity bifurcation analysis versus Imperfection approach
International Journal of Plasticity, 2017Co-Authors: Holanyo K Akpama, Ben M Bettaieb, Farid AbedmeraimAbstract:Abstract The present study focuses on the development of a relevant numerical tool for predicting the onset of localized necking in polycrystalline aggregates. The latter are assumed to be representative of thin metal sheets. In this tool, a micromechanical model, based on the rate-independent self-consistent multi-scale scheme, is developed to accurately describe the mechanical behavior of polycrystalline aggregates from that of their single crystal constituents. In the current paper, the constitutive framework at the single crystal scale follows a finite strain formulation of the rate-independent theory of crystal elasto-plasticity. To predict the occurrence of localized necking in polycrystalline aggregates, this micromechanical modeling is combined with two main strain localization approaches: the bifurcation analysis and the Initial Imperfection method. The formulation of both strain localization indicators takes into consideration the plane stress conditions to which thin metal sheets are subjected during deformation. From a numerical point of view, strain localization analysis with this crystal plasticity approach can be viewed as a strongly non-linear problem. Hence, several numerical algorithms and techniques are developed and implemented in the aim of efficiently solving this non-linear problem. Various simulation results obtained by the application of the developed numerical tool are presented and extensively discussed. It is demonstrated from these results that the predictions obtained with the Marciniak–Kuczynski procedure tend towards those yielded by the bifurcation theory, when the Initial Imperfection ratio tends towards zero. Furthermore, the above result is shown to be valid for both scale-transition schemes, namely the full-constraint Taylor model and self-consistent scheme.