SAM
https://sam.ensam.eu:443
The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Tue, 05 Nov 2024 07:34:55 GMT2024-11-05T07:34:55ZLimit-point buckling analyses using solid, shell and solid–shell elements
http://hdl.handle.net/10985/8936
Limit-point buckling analyses using solid, shell and solid–shell elements
KILLPACK, Marc; ABED-MERAIM, Farid
In this paper, the recently-developed solid-shell element SHB8PS is used for the analysis of a representative set of popular limit-point buckling benchmark problems. For this purpose, the element has been implemented in Abaqus/Standard finite element software and the modified Riks method was employed as an efficient path-following strategy. For the. benchmark problems tested, the new element shows better performance compared to solid elements and often performs as well as state-of-the-art shell elements. In contrast to shell elements, it allows for the accurate prescription of boundary conditions as applied to the actual edges of the structure.
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/10985/89362011-01-01T00:00:00ZKILLPACK, MarcABED-MERAIM, Farid In this paper, the recently-developed solid-shell element SHB8PS is used for the analysis of a representative set of popular limit-point buckling benchmark problems. For this purpose, the element has been implemented in Abaqus/Standard finite element software and the modified Riks method was employed as an efficient path-following strategy. For the. benchmark problems tested, the new element shows better performance compared to solid elements and often performs as well as state-of-the-art shell elements. In contrast to shell elements, it allows for the accurate prescription of boundary conditions as applied to the actual edges of the structure.Analyse de bifurcation et critères de force maximum dans la prédiction des limites de striction des tôles métalliques étirées
http://hdl.handle.net/10985/10113
Analyse de bifurcation et critères de force maximum dans la prédiction des limites de striction des tôles métalliques étirées
PEERLINGS, Ron; GEERS, Marc; ABED-MERAIM, Farid
Cette contribution porte sur la prédiction de la striction diffuse dans le contexte des tôles métalliques sous changements biaxiaux. A cette fin, deux approches sont considérées, à savoir la théorie de bifurcation et le principe de force maximum, avec une analyse critique et une comparaison systématique de leurs prédictions respectives. L’expression bien connue du critère de striction diffuse de Swift, dont l’origine est attribuée au principe de force maximum, est montrée ici découler de l’approche de bifurcation, ce qui permet de lui donner une justification et des fondements plus solides.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/101132015-01-01T00:00:00ZPEERLINGS, RonGEERS, MarcABED-MERAIM, Farid Cette contribution porte sur la prédiction de la striction diffuse dans le contexte des tôles métalliques sous changements biaxiaux. A cette fin, deux approches sont considérées, à savoir la théorie de bifurcation et le principe de force maximum, avec une analyse critique et une comparaison systématique de leurs prédictions respectives. L’expression bien connue du critère de striction diffuse de Swift, dont l’origine est attribuée au principe de force maximum, est montrée ici découler de l’approche de bifurcation, ce qui permet de lui donner une justification et des fondements plus solides.A new locking-free formulation for the SHB8PS solid–shell element: non-linear benchmark problems
http://hdl.handle.net/10985/10454
A new locking-free formulation for the SHB8PS solid–shell element: non-linear benchmark problems
COMBESCURE, Alain; ABED-MERAIM, Farid
In this work, a new physically stabilized and locking-free formulation of the SHB8PS element is presented. This is a solid-shell element based on a purely 3D formulation. It has eight nodes as well as five integration points, all distributed along the “thickness” direction. Consequently, it can be used for the modeling of thin structures, while providing an accurate description of the various through-thickness phenomena. The reduced integration has been used in order to prevent some locking phenomena and to increase computational efficiency. The spurious zero-energy deformation modes due to the reduced integration are efficiently stabilized, whereas the strain components corresponding to locking modes are eliminated with a projection technique following the Enhanced Assumed Strain (EAS) method.
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/10985/104542007-01-01T00:00:00ZCOMBESCURE, AlainABED-MERAIM, Farid In this work, a new physically stabilized and locking-free formulation of the SHB8PS element is presented. This is a solid-shell element based on a purely 3D formulation. It has eight nodes as well as five integration points, all distributed along the “thickness” direction. Consequently, it can be used for the modeling of thin structures, while providing an accurate description of the various through-thickness phenomena. The reduced integration has been used in order to prevent some locking phenomena and to increase computational efficiency. The spurious zero-energy deformation modes due to the reduced integration are efficiently stabilized, whereas the strain components corresponding to locking modes are eliminated with a projection technique following the Enhanced Assumed Strain (EAS) method.Simulation multi-échelle du skin-pass des aciers IF : Prédiction de la texture de déformation et du comportement mécanique
http://hdl.handle.net/10985/10112
Simulation multi-échelle du skin-pass des aciers IF : Prédiction de la texture de déformation et du comportement mécanique
SOHO, Komi; LEMOINE, Xavier; ZAHROUNI, Hamid; ABED-MERAIM, Farid
L’objectif principal de cette étude est de prédire la texture de déformation et le comportement mécanique des aciers IF au cours du procédé de laminage des produits plats à faible taux de réduction. Un modèle basé sur l’homogénéisation autocohérente du comportement élastoplastique du monocristal est adopté pour modéliser le comportement de l’acier. Afin de réduire les temps de calcul dans la simulation multi-échelle, une procédure simplifiée est adoptée pour coupler le code de simulation numérique LAM3 au modèle de comportement basé sur la micromécanique.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/101122015-01-01T00:00:00ZSOHO, KomiLEMOINE, XavierZAHROUNI, HamidABED-MERAIM, Farid L’objectif principal de cette étude est de prédire la texture de déformation et le comportement mécanique des aciers IF au cours du procédé de laminage des produits plats à faible taux de réduction. Un modèle basé sur l’homogénéisation autocohérente du comportement élastoplastique du monocristal est adopté pour modéliser le comportement de l’acier. Afin de réduire les temps de calcul dans la simulation multi-échelle, une procédure simplifiée est adoptée pour coupler le code de simulation numérique LAM3 au modèle de comportement basé sur la micromécanique.Formulation of new quadratic solid-shell elements and their evaluation on popular benchmark problems
http://hdl.handle.net/10985/10459
Formulation of new quadratic solid-shell elements and their evaluation on popular benchmark problems
TRINH, Vuong-Dieu; COMBESCURE, Alain; ABED-MERAIM, Farid
Over the last decade, considerable progress has been made in the development of three-dimensional finite elements capable of modeling thin structures. The coupling between solid and shell formulations has proven to be an interesting way to provide continuum finite element models that can be efficiently used for structural applications. The current work proposes the formulation of two solid-shell elements based on a purely three-dimensional approach. These elements have numerous advantages for the analysis of various complex structural geometries that are common in many industrial applications. Their main advantage is to allow such complex structural shapes to be meshed without classical problems of connecting zones meshed with different element types (continuum and structural elements for instance). Another important benefit of solid-shell elements is the avoidance of tedious pure-shell element formulations needed for the complex treatment of large rotations. The two solid-shell elements developed are a 20-node and a 15-node element, respectively, with displacements as the only degrees of freedom. They also have a special direction called “the thickness”. Therefore, they can be used for the modeling of thin structures, while providing an accurate description of various through-thickness phenomena thanks to the use of a set of integration points in that direction. A reduced integration scheme has been introduced to prevent some locking phenomena and increase computational efficiency. To assess the effectiveness of the proposed solid-shell elements, a set of popular benchmark problems is investigated, involving linear as well as geometric nonlinear analyses. It is shown that these elements can support high aspect ratios, up to 500, and are especially efficient for elastoplastic bending behavior. The various numerical experiments in linear and nonlinear situations reveal that these solid-shell elements perform really better than standard solid elements having similar properties in terms of geometry, interpolation and degrees of freedom.
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/10985/104592010-01-01T00:00:00ZTRINH, Vuong-DieuCOMBESCURE, AlainABED-MERAIM, Farid Over the last decade, considerable progress has been made in the development of three-dimensional finite elements capable of modeling thin structures. The coupling between solid and shell formulations has proven to be an interesting way to provide continuum finite element models that can be efficiently used for structural applications. The current work proposes the formulation of two solid-shell elements based on a purely three-dimensional approach. These elements have numerous advantages for the analysis of various complex structural geometries that are common in many industrial applications. Their main advantage is to allow such complex structural shapes to be meshed without classical problems of connecting zones meshed with different element types (continuum and structural elements for instance). Another important benefit of solid-shell elements is the avoidance of tedious pure-shell element formulations needed for the complex treatment of large rotations. The two solid-shell elements developed are a 20-node and a 15-node element, respectively, with displacements as the only degrees of freedom. They also have a special direction called “the thickness”. Therefore, they can be used for the modeling of thin structures, while providing an accurate description of various through-thickness phenomena thanks to the use of a set of integration points in that direction. A reduced integration scheme has been introduced to prevent some locking phenomena and increase computational efficiency. To assess the effectiveness of the proposed solid-shell elements, a set of popular benchmark problems is investigated, involving linear as well as geometric nonlinear analyses. It is shown that these elements can support high aspect ratios, up to 500, and are especially efficient for elastoplastic bending behavior. The various numerical experiments in linear and nonlinear situations reveal that these solid-shell elements perform really better than standard solid elements having similar properties in terms of geometry, interpolation and degrees of freedom.Elasto-visco-plastic modeling of mild steels for sheet forming applications over a large range of strain rates
http://hdl.handle.net/10985/9906
Elasto-visco-plastic modeling of mild steels for sheet forming applications over a large range of strain rates
PIPARD, Jean-Marc; LEMOINE, Xavier; ABED-MERAIM, Farid ; BALAN, Tudor
A physically based elasto-visco-plastic constitutive model is presented and compared to experimental results for three different mild steels. The experiments consist of tensile tests ranging from quasi-static conditions up to strain rates of 103 s-1 as well as quasi-static simple and reverse shear tests at different amounts of pre-strain. Additional two-step sequential mechanical tests (Bauschinger and orthogonal effects) have been performed to further evaluate the ability of the model to describe strain-path changes at moderate/large strains. The model requires significantly fewer material parameters compared to other visco-plasticity models from the literature, while being able to describe some of the main features of the strain-rate sensitivity of mild steels. Accordingly, the parameter identification is simple and intuitive, requiring a relatively small set of experiments. The strain-rate sensitivity modeling is not restricted to a particular hardening law and thus provides a general framework in which advanced hardening equations can be adopted.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/99062013-01-01T00:00:00ZPIPARD, Jean-MarcLEMOINE, XavierABED-MERAIM, Farid BALAN, TudorA physically based elasto-visco-plastic constitutive model is presented and compared to experimental results for three different mild steels. The experiments consist of tensile tests ranging from quasi-static conditions up to strain rates of 103 s-1 as well as quasi-static simple and reverse shear tests at different amounts of pre-strain. Additional two-step sequential mechanical tests (Bauschinger and orthogonal effects) have been performed to further evaluate the ability of the model to describe strain-path changes at moderate/large strains. The model requires significantly fewer material parameters compared to other visco-plasticity models from the literature, while being able to describe some of the main features of the strain-rate sensitivity of mild steels. Accordingly, the parameter identification is simple and intuitive, requiring a relatively small set of experiments. The strain-rate sensitivity modeling is not restricted to a particular hardening law and thus provides a general framework in which advanced hardening equations can be adopted.Numerical integration of rate-independent BCC single crystal plasticity models: comparative study of two classes of numerical algorithms
http://hdl.handle.net/10985/10654
Numerical integration of rate-independent BCC single crystal plasticity models: comparative study of two classes of numerical algorithms
AKPAMA, Holanyo K.; BEN BETTAIEB, Mohamed; ABED-MERAIM, Farid
In an incremental formulation suitable to numerical implementation, the use of rate-independent theory of crystal plasticity essentially leads to four fundamental problems. The first is to determine the set of potentially active slip systems over a time increment. The second is to select the active slip systems among the potentially active ones. The third is to compute the slip rates (or the slip increments) for the active slip systems. And the last problem is the possible non-uniqueness of slip rates. The purpose of this paper is to propose satisfactory responses to the above-mentioned first three issues by presenting and comparing two novel numerical algorithms. The first algorithm is based on the usual return-mapping integration scheme, while the second follows the so-called ultimate scheme. The latter is shown to be more relevant and efficient than the former. These comparative performances are illustrated through various numerical simulations of the mechanical behavior of single crystals and polycrystalline aggregates subjected to monotonic and complex loadings. Although these algorithms are applied in this paper to Body-Centered-Cubic (BCC) crystal structures, they are quite general and suitable for integrating the constitutive equations for other crystal structures (e.g., FCC and HCP).
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/10985/106542016-01-01T00:00:00ZAKPAMA, Holanyo K.BEN BETTAIEB, MohamedABED-MERAIM, Farid In an incremental formulation suitable to numerical implementation, the use of rate-independent theory of crystal plasticity essentially leads to four fundamental problems. The first is to determine the set of potentially active slip systems over a time increment. The second is to select the active slip systems among the potentially active ones. The third is to compute the slip rates (or the slip increments) for the active slip systems. And the last problem is the possible non-uniqueness of slip rates. The purpose of this paper is to propose satisfactory responses to the above-mentioned first three issues by presenting and comparing two novel numerical algorithms. The first algorithm is based on the usual return-mapping integration scheme, while the second follows the so-called ultimate scheme. The latter is shown to be more relevant and efficient than the former. These comparative performances are illustrated through various numerical simulations of the mechanical behavior of single crystals and polycrystalline aggregates subjected to monotonic and complex loadings. Although these algorithms are applied in this paper to Body-Centered-Cubic (BCC) crystal structures, they are quite general and suitable for integrating the constitutive equations for other crystal structures (e.g., FCC and HCP).Investigation of advanced strain-path dependent material models for sheet metal forming simulations
http://hdl.handle.net/10985/6562
Investigation of advanced strain-path dependent material models for sheet metal forming simulations
HADDAG, Badis; ABED-MERAIM, Farid ; BALAN, Tudor
Sheet metal forming processes often involve complex loading sequences. To improve the prediction of some undesirable phenomena, such as springback, physical behavior models should be considered. This paper investigates springback behavior predicted by advanced elastoplastic hardening models which combine isotropic and kinematic hardening and take strain-path changes into account. A dislocation-based microstructural hardening model formulated from physical observations and the more classical cyclic model of Chaboche have been considered in this work. Numerical implementation was carried out in the ABAQUS software using a return mapping algorithm with a combined backward Euler and semi-analytical integration scheme of the constitutive equations. The capability of each model to reproduce transient hardening phenomena at abrupt strain-path changes has been shown via simulations of sequential rheological tests. A springback analysis of strip drawing tests was performed in order to emphasize the impact of several influential parameters, namely: process, numerical and behavior parameters. The effect of the two hardening models with respect to the process parameters has been specifically highlighted.
Sun, 01 Jan 2006 00:00:00 GMThttp://hdl.handle.net/10985/65622006-01-01T00:00:00ZHADDAG, BadisABED-MERAIM, Farid BALAN, TudorSheet metal forming processes often involve complex loading sequences. To improve the prediction of some undesirable phenomena, such as springback, physical behavior models should be considered. This paper investigates springback behavior predicted by advanced elastoplastic hardening models which combine isotropic and kinematic hardening and take strain-path changes into account. A dislocation-based microstructural hardening model formulated from physical observations and the more classical cyclic model of Chaboche have been considered in this work. Numerical implementation was carried out in the ABAQUS software using a return mapping algorithm with a combined backward Euler and semi-analytical integration scheme of the constitutive equations. The capability of each model to reproduce transient hardening phenomena at abrupt strain-path changes has been shown via simulations of sequential rheological tests. A springback analysis of strip drawing tests was performed in order to emphasize the impact of several influential parameters, namely: process, numerical and behavior parameters. The effect of the two hardening models with respect to the process parameters has been specifically highlighted.Formability prediction of thin metal sheets using various localization criteria
http://hdl.handle.net/10985/6555
Formability prediction of thin metal sheets using various localization criteria
ALTMEYER, Guillaume; ABED-MERAIM, Farid ; BALAN, Tudor
The aim of this paper is to give an overview of the theoretical basis of the most significant and commonly used localization criteria reformulated into a unified framework, and to apply these criteria to different materials in order to determine their formability domains. After giving a general material description based on a phenomenological approach, theoretical foundations of localization criteria are presented together with their advantages and drawbacks. These criteria rely on diverse theories: maximum load principle, bifurcation analysis, Marciniak-Kuczynski analysis, and stability analysis by a linear perturbation method. They are then applied to a brass and a Dual Phase steel and the predicted Forming Limit Diagrams (FLD) are discussed.
Thu, 01 Jan 2009 00:00:00 GMThttp://hdl.handle.net/10985/65552009-01-01T00:00:00ZALTMEYER, GuillaumeABED-MERAIM, Farid BALAN, TudorThe aim of this paper is to give an overview of the theoretical basis of the most significant and commonly used localization criteria reformulated into a unified framework, and to apply these criteria to different materials in order to determine their formability domains. After giving a general material description based on a phenomenological approach, theoretical foundations of localization criteria are presented together with their advantages and drawbacks. These criteria rely on diverse theories: maximum load principle, bifurcation analysis, Marciniak-Kuczynski analysis, and stability analysis by a linear perturbation method. They are then applied to a brass and a Dual Phase steel and the predicted Forming Limit Diagrams (FLD) are discussed.Localized necking predictions based on rate-independent self-consistent polycrystal plasticity: Bifurcation analysis versus imperfection approach
http://hdl.handle.net/10985/11856
Localized necking predictions based on rate-independent self-consistent polycrystal plasticity: Bifurcation analysis versus imperfection approach
AKPAMA, Holanyo K.; BEN BETTAIEB, Mohamed; ABED-MERAIM, Farid
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 elastoplasticity. 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 nonlinear 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 MarciniakeKuczynski 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.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10985/118562017-01-01T00:00:00ZAKPAMA, Holanyo K.BEN BETTAIEB, MohamedABED-MERAIM, Farid 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 elastoplasticity. 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 nonlinear 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 MarciniakeKuczynski 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.