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http://hdl.handle.net/10985/10440
Investigation of ductility limits based on bifurcation theory coupled with continuum damage mechanics
BOUKTIR, Yasser; CHALAL, Hocine; HADDAD, Moussa; ABED-MERAIM, Farid
The ductility limits of an St14 steel are investigated using an elastic‒plastic‒damage model and bifurcation theory. An associative J2-flow theory of plasticity is coupled with damage within the framework of continuum damage mechanics. For strain localization prediction, the bifurcation analysis is adopted. Both the constitutive equations and the localization bifurcation criterion are implemented into the finite element code ABAQUS, within the framework of large strains and a fully three-dimensional formulation. The material parameters associated with the fully coupled elastic‒plastic‒damage model are calibrated based on experimental tensile tests together with an inverse identification procedure. The above-described approach allows the forming limit diagrams of the studied material to be determined, which are then compared with experimental measurements. A main conclusion of the current study is that the proposed approach is able to provide predictions that are in good agreement with experiments under the condition of accurate material parameter calibration. The latter requires a careful identification strategy based on both calibrated finite element simulations of tensile tests at large strains and appropriately selected necking measurements. The resulting approach represents a useful basis for setting up reliable ductility limit prediction tools as well as effective parameter identification strategies.
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/10985/104402016-01-01T00:00:00ZBOUKTIR, YasserCHALAL, HocineHADDAD, MoussaABED-MERAIM, FaridThe ductility limits of an St14 steel are investigated using an elastic‒plastic‒damage model and bifurcation theory. An associative J2-flow theory of plasticity is coupled with damage within the framework of continuum damage mechanics. For strain localization prediction, the bifurcation analysis is adopted. Both the constitutive equations and the localization bifurcation criterion are implemented into the finite element code ABAQUS, within the framework of large strains and a fully three-dimensional formulation. The material parameters associated with the fully coupled elastic‒plastic‒damage model are calibrated based on experimental tensile tests together with an inverse identification procedure. The above-described approach allows the forming limit diagrams of the studied material to be determined, which are then compared with experimental measurements. A main conclusion of the current study is that the proposed approach is able to provide predictions that are in good agreement with experiments under the condition of accurate material parameter calibration. The latter requires a careful identification strategy based on both calibrated finite element simulations of tensile tests at large strains and appropriately selected necking measurements. The resulting approach represents a useful basis for setting up reliable ductility limit prediction tools as well as effective parameter identification strategies.Evaluation of a new solid-shell finite element on the simulation of sheet metal forming processes
http://hdl.handle.net/10985/10071
Evaluation of a new solid-shell finite element on the simulation of sheet metal forming processes
CHALAL, Hocine; SALAHOUELHADJ, Abdellah; ABED-MERAIM, Farid
In this paper, the performance of the solid-shell finite element SHB8PS is assessed in the context of sheet metal forming simulation using anisotropic elastic-plastic behavior models. This finite element technology has been implemented into the commercial implicit finite element code Abaqus/Standard via the UEL subroutine. It consists of an eight-node three-dimensional hexahedron with reduced integration, provided with an arbitrary number of integration points along the thickness direction. The use of an in-plane reduced integration scheme prevents some locking phenomena, resulting in a computationally efficient formulation when compared to conventional 3D solid elements. Another interesting feature lies in the possibility of increasing the number of through-thickness integration points within a single element layer, which enables an accurate description of various phenomena in sheet forming simulations. A general elastic-plastic model has been adopted in the constitutive modeling for sheet forming applications with plastic anisotropy. As an illustrative example, the performance of the element is shown in the earing prediction of a cylindrical cup drawing process.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/10985/100712012-01-01T00:00:00ZCHALAL, HocineSALAHOUELHADJ, AbdellahABED-MERAIM, FaridIn this paper, the performance of the solid-shell finite element SHB8PS is assessed in the context of sheet metal forming simulation using anisotropic elastic-plastic behavior models. This finite element technology has been implemented into the commercial implicit finite element code Abaqus/Standard via the UEL subroutine. It consists of an eight-node three-dimensional hexahedron with reduced integration, provided with an arbitrary number of integration points along the thickness direction. The use of an in-plane reduced integration scheme prevents some locking phenomena, resulting in a computationally efficient formulation when compared to conventional 3D solid elements. Another interesting feature lies in the possibility of increasing the number of through-thickness integration points within a single element layer, which enables an accurate description of various phenomena in sheet forming simulations. A general elastic-plastic model has been adopted in the constitutive modeling for sheet forming applications with plastic anisotropy. As an illustrative example, the performance of the element is shown in the earing prediction of a cylindrical cup drawing process.Quadratic solid‒shell elements for nonlinear structural analysis and sheet metal forming simulation
http://hdl.handle.net/10985/17477
Quadratic solid‒shell elements for nonlinear structural analysis and sheet metal forming simulation
WANG, Peng; CHALAL, Hocine; ABED-MERAIM, Farid
In this paper, two quadratic solid‒shell (SHB) elements are proposed for the three-dimensional modeling of thin structures. These consist of a twenty-node hexahedral solid‒shell element, denoted SHB20, and its fifteen-node prismatic counterpart, denoted SHB15. The formulation of these elements is extended in this work to include geometric and material nonlinearities, for application to problems involving large displacements and rotations as well as plasticity. For this purpose, the SHB elements are coupled with large-strain anisotropic elasto-plastic constitutive equations for metallic materials. Although based on a purely three-dimensional approach, several modifications are introduced in the formulation of these elements to provide them with interesting shell features. In particular, a special direction is chosen to represent the thickness, along which a user-defined number of integration points are located. Furthermore, for efficiency requirements and for alleviating locking phenomena, an in-plane reduced-integration scheme is adopted. The resulting formulations are implemented into the finite element software ABAQUS/Standard and, to assess their performance, a variety of nonlinear benchmark problems are investigated. Attention is then focused on the simulation of various complex sheet metal forming processes, involving large strain, anisotropic plasticity, and double-sided contact. From all simulation results, it appears that the SHB elements represent an interesting alternative to traditional shell and solid elements, due to their versatility and capability of accurately modeling selective nonlinear benchmark problems as well as complex sheet metal forming processes.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10985/174772017-01-01T00:00:00ZWANG, PengCHALAL, HocineABED-MERAIM, FaridIn this paper, two quadratic solid‒shell (SHB) elements are proposed for the three-dimensional modeling of thin structures. These consist of a twenty-node hexahedral solid‒shell element, denoted SHB20, and its fifteen-node prismatic counterpart, denoted SHB15. The formulation of these elements is extended in this work to include geometric and material nonlinearities, for application to problems involving large displacements and rotations as well as plasticity. For this purpose, the SHB elements are coupled with large-strain anisotropic elasto-plastic constitutive equations for metallic materials. Although based on a purely three-dimensional approach, several modifications are introduced in the formulation of these elements to provide them with interesting shell features. In particular, a special direction is chosen to represent the thickness, along which a user-defined number of integration points are located. Furthermore, for efficiency requirements and for alleviating locking phenomena, an in-plane reduced-integration scheme is adopted. The resulting formulations are implemented into the finite element software ABAQUS/Standard and, to assess their performance, a variety of nonlinear benchmark problems are investigated. Attention is then focused on the simulation of various complex sheet metal forming processes, involving large strain, anisotropic plasticity, and double-sided contact. From all simulation results, it appears that the SHB elements represent an interesting alternative to traditional shell and solid elements, due to their versatility and capability of accurately modeling selective nonlinear benchmark problems as well as complex sheet metal forming processes.Linear and Quadratic Solid-Shell Elements for Quasi-Static and Dynamic Simulations of Thin 3D Structures: Application to a Deep Drawing Process
http://hdl.handle.net/10985/17479
Linear and Quadratic Solid-Shell Elements for Quasi-Static and Dynamic Simulations of Thin 3D Structures: Application to a Deep Drawing Process
WANG, Peng; CHALAL, Hocine; ABED-MERAIM, Farid
A family of prismatic and hexahedral solid–shell (SHB) elements, with their linear and quadratic versions, is proposed in this work to model thin structures. The formulation of these SHB elements is extended to explicit dynamic analysis and large-strain anisotropic plasticity on the basis of a fully three-dimensional approach using an arbitrary number of integration points along the thickness direction. Several special treatments are applied to the SHB elements in order to avoid all locking phenomena and to guarantee the accuracy and efficiency of the simulations. These solid-shell elements have been implemented into ABAQUS standard/quasi-static and explicit/dynamic software packages. A number of static and dynamic benchmark problems, as well as a simulation of the deep drawing of a cylindrical cup, have been conducted to assess the performance of these SHB elements.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10985/174792017-01-01T00:00:00ZWANG, PengCHALAL, HocineABED-MERAIM, FaridA family of prismatic and hexahedral solid–shell (SHB) elements, with their linear and quadratic versions, is proposed in this work to model thin structures. The formulation of these SHB elements is extended to explicit dynamic analysis and large-strain anisotropic plasticity on the basis of a fully three-dimensional approach using an arbitrary number of integration points along the thickness direction. Several special treatments are applied to the SHB elements in order to avoid all locking phenomena and to guarantee the accuracy and efficiency of the simulations. These solid-shell elements have been implemented into ABAQUS standard/quasi-static and explicit/dynamic software packages. A number of static and dynamic benchmark problems, as well as a simulation of the deep drawing of a cylindrical cup, have been conducted to assess the performance of these SHB elements.Quadratic solid–shell finite elements for geometrically nonlinear analysis of functionally graded material plates
http://hdl.handle.net/10985/17476
Quadratic solid–shell finite elements for geometrically nonlinear analysis of functionally graded material plates
CHALAL, Hocine; ABED-MERAIM, Farid
In the current contribution, prismatic and hexahedral quadratic solid–shell (SHB) finite elements are proposed for the geometrically nonlinear analysis of thin structures made of functionally graded material (FGM). The proposed SHB finite elements are developed within a purely 3D framework, with displacements as the only degrees of freedom. Also, the in-plane reduced-integration technique is combined with the assumed-strain method to alleviate various locking phenomena. Furthermore, an arbitrary number of integration points are placed along a special direction, which represents the thickness. The developed elements are coupled with functionally graded behavior for the modeling of thin FGM plates. To this end, the Young modulus of the FGM plate is assumed to vary gradually in the thickness direction, according to a volume fraction distribution. The resulting formulations are implemented into the quasi-static ABAQUS/Standard finite element software in the framework of large displacements and rotations. Popular nonlinear benchmark problems are considered to assess the performance and accuracy of the proposed SHB elements. Comparisons with reference solutions from the literature demonstrate the good capabilities of the developed SHB elements for the 3D simulation of thin FGM plates.
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/10985/174762018-01-01T00:00:00ZCHALAL, HocineABED-MERAIM, FaridIn the current contribution, prismatic and hexahedral quadratic solid–shell (SHB) finite elements are proposed for the geometrically nonlinear analysis of thin structures made of functionally graded material (FGM). The proposed SHB finite elements are developed within a purely 3D framework, with displacements as the only degrees of freedom. Also, the in-plane reduced-integration technique is combined with the assumed-strain method to alleviate various locking phenomena. Furthermore, an arbitrary number of integration points are placed along a special direction, which represents the thickness. The developed elements are coupled with functionally graded behavior for the modeling of thin FGM plates. To this end, the Young modulus of the FGM plate is assumed to vary gradually in the thickness direction, according to a volume fraction distribution. The resulting formulations are implemented into the quasi-static ABAQUS/Standard finite element software in the framework of large displacements and rotations. Popular nonlinear benchmark problems are considered to assess the performance and accuracy of the proposed SHB elements. Comparisons with reference solutions from the literature demonstrate the good capabilities of the developed SHB elements for the 3D simulation of thin FGM plates.Elastic-plastic analyses using the solid-shell finite element SHB8PS and evaluation on sheet forming applications
http://hdl.handle.net/10985/10338
Elastic-plastic analyses using the solid-shell finite element SHB8PS and evaluation on sheet forming applications
SALAHOUELHADJ, Abdellah; CHALAL, Hocine; ABED-MERAIM, Farid; BALAN, Tudor
In this contribution, the formulation of the SHB8PS continuum shell finite element is extended to anisotropic elastic-plastic behavior models with combined isotropic-kinematic hardening at large deformations. The resulting element is then implemented into the commercial implicit finite element code Abaqus/Standard via the UEL subroutine. The SHB8PS element is an eight-node, three-dimensional brick with displacements as the only degrees of freedom and a preferential direction called the thickness. A reduced integration scheme is adopted using an arbitrary number of integration points along the thickness direction and only one integration point in the other directions. The hourglass modes due to this reduced integration are controlled using a physical stabilization technique together with an assumed strain method for the elimination of locking. Therefore, the element can be used to model thin structures while providing an accurate description of the various throughthickness phenomena. Its performance is assessed through several applications involving different types of non-linearities: geometric, material and that induced by contact. Particular attention is given to springback prediction for a Numisheet benchmark problem.
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/10985/103382011-01-01T00:00:00ZSALAHOUELHADJ, AbdellahCHALAL, HocineABED-MERAIM, FaridBALAN, TudorIn this contribution, the formulation of the SHB8PS continuum shell finite element is extended to anisotropic elastic-plastic behavior models with combined isotropic-kinematic hardening at large deformations. The resulting element is then implemented into the commercial implicit finite element code Abaqus/Standard via the UEL subroutine. The SHB8PS element is an eight-node, three-dimensional brick with displacements as the only degrees of freedom and a preferential direction called the thickness. A reduced integration scheme is adopted using an arbitrary number of integration points along the thickness direction and only one integration point in the other directions. The hourglass modes due to this reduced integration are controlled using a physical stabilization technique together with an assumed strain method for the elimination of locking. Therefore, the element can be used to model thin structures while providing an accurate description of the various throughthickness phenomena. Its performance is assessed through several applications involving different types of non-linearities: geometric, material and that induced by contact. Particular attention is given to springback prediction for a Numisheet benchmark problem.Strain-path dependent hardening models with rigorously identical predictions under monotonic loading
http://hdl.handle.net/10985/19682
Strain-path dependent hardening models with rigorously identical predictions under monotonic loading
YANG, Yanfeng; VINCZE, Gabriela; BAUDOUIN, Cyrille; CHALAL, Hocine; BALAN, Tudor
Accurate sheet metal simulation often requires advanced strain-path dependent material models, in order to predict the material response under complex loading conditions, including monotonic, reverse and orthogonal paths. More and more flexible models imply higher and higher costs in terms of parameter identification, computer implementation and simulation time, and robust comparison is often compromised by the inconsistent predictions of advanced models under monotonic loading. In this paper, a simple and general approach is proposed for the alteration of advanced hardening models in order to make them rigorously identical to each other under monotonic loading. This objective was reached without any drawback other than the addition of the corresponding equations. On the contrary, the flexibility and accuracy of the selected models was improved, and the parameter identification procedure became simpler, more accurate and more robust. Three material models of increasing complexity were selected to demonstrate the interest of this approach with respect to a complete set of characterisation experiments for a DP600 sheet steel.
Fri, 01 Jan 2021 00:00:00 GMThttp://hdl.handle.net/10985/196822021-01-01T00:00:00ZYANG, YanfengVINCZE, GabrielaBAUDOUIN, CyrilleCHALAL, HocineBALAN, TudorAccurate sheet metal simulation often requires advanced strain-path dependent material models, in order to predict the material response under complex loading conditions, including monotonic, reverse and orthogonal paths. More and more flexible models imply higher and higher costs in terms of parameter identification, computer implementation and simulation time, and robust comparison is often compromised by the inconsistent predictions of advanced models under monotonic loading. In this paper, a simple and general approach is proposed for the alteration of advanced hardening models in order to make them rigorously identical to each other under monotonic loading. This objective was reached without any drawback other than the addition of the corresponding equations. On the contrary, the flexibility and accuracy of the selected models was improved, and the parameter identification procedure became simpler, more accurate and more robust. Three material models of increasing complexity were selected to demonstrate the interest of this approach with respect to a complete set of characterisation experiments for a DP600 sheet steel.Quadratic prismatic and hexahedral solid‒shell elements for geometric nonlinear analysis of laminated composite structures
http://hdl.handle.net/10985/17481
Quadratic prismatic and hexahedral solid‒shell elements for geometric nonlinear analysis of laminated composite structures
WANG, Peng; CHALAL, Hocine; ABED-MERAIM, Farid
The current contribution proposes two quadratic, prismatic and hexahedral, solid–shell elements for the geometric nonlinear analysis of laminated composite structures. The formulation of the proposed solid–shell elements is based on a fully three-dimensional approach combining the assumed-strain method and the reduced-integration technique. In particular, only translational degrees of freedom are considered in the formulation and a preferential direction is chosen as the thickness direction, along which an arbitrary number of integration points are arranged. Making use of different physical local frames, these elements are coupled with fully three-dimensional orthotropic constitutive equations, which allows modeling multilayered composite structures with only a single element layer through the thickness. A series of popular nonlinear benchmark tests for laminated composite structures is performed to assess the performance of the proposed SHB elements. Compared to reference solutions taken from the literature, the results provided by the SHB elements show excellent agreement. Moreover, on the whole, the proposed SHB elements perform better than state-of-the-art ABAQUS elements, which have the same geometry and kinematics, using comparable mesh discretizations.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10985/174812017-01-01T00:00:00ZWANG, PengCHALAL, HocineABED-MERAIM, FaridThe current contribution proposes two quadratic, prismatic and hexahedral, solid–shell elements for the geometric nonlinear analysis of laminated composite structures. The formulation of the proposed solid–shell elements is based on a fully three-dimensional approach combining the assumed-strain method and the reduced-integration technique. In particular, only translational degrees of freedom are considered in the formulation and a preferential direction is chosen as the thickness direction, along which an arbitrary number of integration points are arranged. Making use of different physical local frames, these elements are coupled with fully three-dimensional orthotropic constitutive equations, which allows modeling multilayered composite structures with only a single element layer through the thickness. A series of popular nonlinear benchmark tests for laminated composite structures is performed to assess the performance of the proposed SHB elements. Compared to reference solutions taken from the literature, the results provided by the SHB elements show excellent agreement. Moreover, on the whole, the proposed SHB elements perform better than state-of-the-art ABAQUS elements, which have the same geometry and kinematics, using comparable mesh discretizations.Numerical Predictions of the Occurrence of Necking in Deep Drawing Processes
http://hdl.handle.net/10985/17482
Numerical Predictions of the Occurrence of Necking in Deep Drawing Processes
CHALAL, Hocine; ABED-MERAIM, Farid
In this work, three numerical necking criteria based on finite element (FE) simulations are proposed for the prediction of forming limit diagrams (FLDs) for sheet metals. An elastic–plastic constitutive model coupled with the Lemaitre continuum damage theory has been implemented into the ABAQUS/Explicit software to simulate simple sheet stretching tests as well as Erichsen deep drawing tests with various sheet specimen geometries. Three numerical criteria have been investigated in order to establish an appropriate necking criterion for the prediction of formability limits. The first numerical criterion is based on the analysis of the thickness strain evolution in the central part of the specimens. The second numerical criterion is based on the analysis of the second time derivative of the thickness strain. As to the third numerical criterion, it relies on a damage threshold associated with the occurrence of necking. The FLDs thus predicted by numerical simulation of simple sheet stretching with various specimen geometries and Erichsen deep drawing tests are compared with the experimental results.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10985/174822017-01-01T00:00:00ZCHALAL, HocineABED-MERAIM, FaridIn this work, three numerical necking criteria based on finite element (FE) simulations are proposed for the prediction of forming limit diagrams (FLDs) for sheet metals. An elastic–plastic constitutive model coupled with the Lemaitre continuum damage theory has been implemented into the ABAQUS/Explicit software to simulate simple sheet stretching tests as well as Erichsen deep drawing tests with various sheet specimen geometries. Three numerical criteria have been investigated in order to establish an appropriate necking criterion for the prediction of formability limits. The first numerical criterion is based on the analysis of the thickness strain evolution in the central part of the specimens. The second numerical criterion is based on the analysis of the second time derivative of the thickness strain. As to the third numerical criterion, it relies on a damage threshold associated with the occurrence of necking. The FLDs thus predicted by numerical simulation of simple sheet stretching with various specimen geometries and Erichsen deep drawing tests are compared with the experimental results.Finite element simulation of sheet metal forming processes using non-quadratic anisotropic plasticity models and solid-Shell finite elements
http://hdl.handle.net/10985/20268
Finite element simulation of sheet metal forming processes using non-quadratic anisotropic plasticity models and solid-Shell finite elements
YOUNAS, Nabeel; CHALAL, Hocine; ABED-MERAIM, Farid
During the last decades, a family of assumed-strain solid-shell finite elements has been developed with enriched benefits of solid and shell finite elements together with special treatments to avoid locking phenomena. These elements have been shown to be efficient in numerical simulation of thin 3D structures with various constitutive models. The current contribution consists in the combination of the developed linear and quadratic solid-shell elements with complex anisotropic plasticity models for aluminum alloys. Conventional quadratic anisotropic yield functions are associated with less accuracy in the simulation of forming processes with metallic materials involving strong anisotropy. For these materials, the plastic anisotropy can be modeled more accurately using advanced non-quadratic yield functions, such as the anisotropic yield criteria proposed by Barlat for aluminum alloys. In this work, various quadratic and non-quadratic anisotropic yield functions are combined with a linear eight-node hexahedral solid-shell element and a linear six-node prismatic solid-shell element, and their quadratic counterparts. The resulting solid-shell elements are implemented into the ABAQUS software for the simulation of benchmark deep drawing process of a cylindrical cup. The predicted results are assessed and compared to experimental ones taken from the literature. Compared to the use of conventional quadratic anisotropic yield functions, the results given by the combination of the developed solid-shell elements with non-quadratic anisotropic yield functions show good agreement with experiments.
Wed, 01 Jan 2020 00:00:00 GMThttp://hdl.handle.net/10985/202682020-01-01T00:00:00ZYOUNAS, NabeelCHALAL, HocineABED-MERAIM, FaridDuring the last decades, a family of assumed-strain solid-shell finite elements has been developed with enriched benefits of solid and shell finite elements together with special treatments to avoid locking phenomena. These elements have been shown to be efficient in numerical simulation of thin 3D structures with various constitutive models. The current contribution consists in the combination of the developed linear and quadratic solid-shell elements with complex anisotropic plasticity models for aluminum alloys. Conventional quadratic anisotropic yield functions are associated with less accuracy in the simulation of forming processes with metallic materials involving strong anisotropy. For these materials, the plastic anisotropy can be modeled more accurately using advanced non-quadratic yield functions, such as the anisotropic yield criteria proposed by Barlat for aluminum alloys. In this work, various quadratic and non-quadratic anisotropic yield functions are combined with a linear eight-node hexahedral solid-shell element and a linear six-node prismatic solid-shell element, and their quadratic counterparts. The resulting solid-shell elements are implemented into the ABAQUS software for the simulation of benchmark deep drawing process of a cylindrical cup. The predicted results are assessed and compared to experimental ones taken from the literature. Compared to the use of conventional quadratic anisotropic yield functions, the results given by the combination of the developed solid-shell elements with non-quadratic anisotropic yield functions show good agreement with experiments.