SAM
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http://hdl.handle.net/10985/10376
Détermination des diagrammes de perte d’ellipticité par une approche micromécanique
FRANZ, Gérald; ABED-MERAIM, Farid; BEN ZINEB, Tarak; BERVEILLER, Marcel; LEMOINE, Xavier
La striction et la rupture au cours de l’opération d’emboutissage figurent parmi les principaux phénomènes limitant les déformations maximales admises par les métaux. Ces phénomènes sont liés à la microstructure des matériaux ainsi qu’aux conditions de sollicitation. Afin de caractériser l’aptitude au formage d’un matériau, et ce pour différents modes de déformations, Keeler (1965) et Goodwin (1968) ont introduit la notion de Courbe Limite de Formage (CLF). L'inconvénient de cette représentation est sa forte dépendance au chemin de déformation, ce qui suppose qu’elle doit être déterminée pour chaque type de trajet de déformation. L’idée d’Arrieux (1982) fut de rechercher une représentation indépendante du trajet de chargement, ce qui donna naissance aux courbes limites de formage en contraintes. Les diagrammes de perte d'ellipticité (PDE) représentés dans l’espace des déformations principales dans celui des contraintes principales à partir d’une approche micromécanique sont présentés dans ce poster. Ces diagrammes sont qualitativement similaires aux CLF mais beaucoup plus restrictifs. L’influence de certains paramètres sur le tracé de ces courbes est étudiée.
Sun, 01 Jan 2006 00:00:00 GMThttp://hdl.handle.net/10985/103762006-01-01T00:00:00ZFRANZ, GéraldABED-MERAIM, FaridBEN ZINEB, TarakBERVEILLER, MarcelLEMOINE, XavierLa striction et la rupture au cours de l’opération d’emboutissage figurent parmi les principaux phénomènes limitant les déformations maximales admises par les métaux. Ces phénomènes sont liés à la microstructure des matériaux ainsi qu’aux conditions de sollicitation. Afin de caractériser l’aptitude au formage d’un matériau, et ce pour différents modes de déformations, Keeler (1965) et Goodwin (1968) ont introduit la notion de Courbe Limite de Formage (CLF). L'inconvénient de cette représentation est sa forte dépendance au chemin de déformation, ce qui suppose qu’elle doit être déterminée pour chaque type de trajet de déformation. L’idée d’Arrieux (1982) fut de rechercher une représentation indépendante du trajet de chargement, ce qui donna naissance aux courbes limites de formage en contraintes. Les diagrammes de perte d'ellipticité (PDE) représentés dans l’espace des déformations principales dans celui des contraintes principales à partir d’une approche micromécanique sont présentés dans ce poster. Ces diagrammes sont qualitativement similaires aux CLF mais beaucoup plus restrictifs. L’influence de certains paramètres sur le tracé de ces courbes est étudiée.A Multiscale Model Based On Intragranular Microstructure: Influence Of Grain-Scale Substructure On Macroscopic Behaviour Of An IF-Steel During Complex Load Paths
http://hdl.handle.net/10985/10249
A Multiscale Model Based On Intragranular Microstructure: Influence Of Grain-Scale Substructure On Macroscopic Behaviour Of An IF-Steel During Complex Load Paths
FRANZ, Gérald; ABED-MERAIM, Farid; BEN ZINEB, Tarak; LEMOINE, Xavier; BERVEILLER, Marcel
A microstructural model, based on Peeters' works, is implemented into a large strain self-consistent scheme, leading to the multiscale model which achieves, for each grain, the calculation of slip activity, with help of regularized formulation drawn from the visco-plasticity framework, and the dislocation microstructure evolution. This paper focuses on the relationship between macroscopic hardening/softening effects and induced microstructure during monotonic and two-stage strain paths.
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/10985/102492007-01-01T00:00:00ZFRANZ, GéraldABED-MERAIM, FaridBEN ZINEB, TarakLEMOINE, XavierBERVEILLER, MarcelA microstructural model, based on Peeters' works, is implemented into a large strain self-consistent scheme, leading to the multiscale model which achieves, for each grain, the calculation of slip activity, with help of regularized formulation drawn from the visco-plasticity framework, and the dislocation microstructure evolution. This paper focuses on the relationship between macroscopic hardening/softening effects and induced microstructure during monotonic and two-stage strain paths.Strain localization analysis using a large strain self-consistent approach
http://hdl.handle.net/10985/10435
Strain localization analysis using a large strain self-consistent approach
FRANZ, Gérald; ABED-MERAIM, Farid; BEN ZINEB, Tarak; LEMOINE, Xavier; BERVEILLER, Marcel
The development of a relevant constitutive model adapted to sheet metal forming simulations requires an accurate description of the most important sources of anisotropy, i.e. the slip processes, the intragranular substructure changes and the texture development. During plastic deformation of thin metallic sheets, strain-path changes often occur in the material resulting in macroscopic effects. These softening/hardening effects must be correctly predicted because they can significantly influence the strain distribution and may lead to flow localization, shear bands and even material failure. The main origin of these effects is related to the intragranular microstructure evolution. This implies that an accurate description of the dislocation patterning during monotonic or complex strain-paths is needed to lead to a reliable constitutive model. A crystal plasticity model coupled with an intragranular microstructure description, inspired by Peeters' works, is used to determine the single crystal behaviour and to describe the dislocation cells evolution. The scale transition between the local behaviour and the polycrystalline one is realized thanks to a large strain self-consistent approach. Moreover, the introduction of a ductility loss criterion, first introduced by Rice, based on the ellipticity loss of the elastic-plastic tangent modulus, is used to plot Ellipticity Loss Diagrams (ELD). Qualitative comparisons are made with experimental Forming Limit Diagrams (FLD) for ferritic steel for simple and complex loading paths. In particular, it is shown that numerical ELD have a shape close to experimental FLD and reproduce qualitatively the effects due to complex loading paths.
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/10985/104352007-01-01T00:00:00ZFRANZ, GéraldABED-MERAIM, FaridBEN ZINEB, TarakLEMOINE, XavierBERVEILLER, MarcelThe development of a relevant constitutive model adapted to sheet metal forming simulations requires an accurate description of the most important sources of anisotropy, i.e. the slip processes, the intragranular substructure changes and the texture development. During plastic deformation of thin metallic sheets, strain-path changes often occur in the material resulting in macroscopic effects. These softening/hardening effects must be correctly predicted because they can significantly influence the strain distribution and may lead to flow localization, shear bands and even material failure. The main origin of these effects is related to the intragranular microstructure evolution. This implies that an accurate description of the dislocation patterning during monotonic or complex strain-paths is needed to lead to a reliable constitutive model. A crystal plasticity model coupled with an intragranular microstructure description, inspired by Peeters' works, is used to determine the single crystal behaviour and to describe the dislocation cells evolution. The scale transition between the local behaviour and the polycrystalline one is realized thanks to a large strain self-consistent approach. Moreover, the introduction of a ductility loss criterion, first introduced by Rice, based on the ellipticity loss of the elastic-plastic tangent modulus, is used to plot Ellipticity Loss Diagrams (ELD). Qualitative comparisons are made with experimental Forming Limit Diagrams (FLD) for ferritic steel for simple and complex loading paths. In particular, it is shown that numerical ELD have a shape close to experimental FLD and reproduce qualitatively the effects due to complex loading paths.A finite-element based numerical tool for Ni47Ti44Nb9 SMA structures design application to tightening rings
http://hdl.handle.net/10985/10100
A finite-element based numerical tool for Ni47Ti44Nb9 SMA structures design application to tightening rings
PIOTROWSKI, Boris; BEN ZINEB, Tarak; EBERHARDT, André; PATOOR, Etienne
This paper deals with the design of Ni47Ti44Nb9 Shape Memory Alloy (SMA) tightening components. The tightening of an SMA ring on an elastic pipe is analyzed using the finite element code ABAQUS® and a UMAT subroutine developed in our group to model the specific behavior of Ni47Ti44Nb9 SMA. Main features of the thermomechanical model implemented in this UMAT routine are briefly recalled. Numerical predictions are validated using experimental tightening pressures obtained on a test bed developed in this work. The validation strategy is documented and the results for different ring thicknesses are presented. This finite element tool is then applied to a parametric study of the influence of ridges on the tightening pressure. Eventually, geometrical defects like out of roundness are considered.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/10985/101002012-01-01T00:00:00ZPIOTROWSKI, BorisBEN ZINEB, TarakEBERHARDT, AndréPATOOR, EtienneThis paper deals with the design of Ni47Ti44Nb9 Shape Memory Alloy (SMA) tightening components. The tightening of an SMA ring on an elastic pipe is analyzed using the finite element code ABAQUS® and a UMAT subroutine developed in our group to model the specific behavior of Ni47Ti44Nb9 SMA. Main features of the thermomechanical model implemented in this UMAT routine are briefly recalled. Numerical predictions are validated using experimental tightening pressures obtained on a test bed developed in this work. The validation strategy is documented and the results for different ring thicknesses are presented. This finite element tool is then applied to a parametric study of the influence of ridges on the tightening pressure. Eventually, geometrical defects like out of roundness are considered.Strain localization analysis using a multiscale model
http://hdl.handle.net/10985/10445
Strain localization analysis using a multiscale model
FRANZ, Gérald; ABED-MERAIM, Farid; BEN ZINEB, Tarak; LEMOINE, Xavier; BERVEILLER, Marcel
The development of a relevant constitutive model adapted to sheet metal forming simulations requires an accurate description of the most important sources of anisotropy, i.e. the slip processes, the intragranular substructure changes and the texture development. During plastic deformation of thin metallic sheets, strain-path changes often occur in the material resulting in macroscopic effects. These softening/hardening effects must be correctly predicted because they can significantly influence the strain distribution and may lead to flow localization, shear bands and even material failure. The main origin of these effects is related to the intragranular microstructure evolution. This implies that an accurate description of the dislocation patterning during monotonic or complex strain-paths is needed to lead to a reliable constitutive model. First, the behaviour at the mesoscopic scale (which is the one of the grain or the single crystal) is modelled by a micromechanical law written within large strain framework. Hardening is taking into account by a matrix whose internal variables are the mean dislocation densities on each slip system. This crystal plasticity based model is implemented into a large strain self-consistent scheme, leading to the multiscale model which achieves, for each grain, the calculation of plastic slip activity, with help of regularized formulation drawn from viscoplasticity. An improvement of this model is suggested with the introduction of intragranular microstructure description. The substructure of a grain is described taking into account the experimental observations as stress-strain curves and TEM micrographs. Following Peeters’ approach, three local dislocations densities, introduced as internal variables in the multiscale model, allow representing the spatially heterogeneous distributions of dislocations inside the grain. Rate equations, based on the consideration of associated creation, storage and annihilation, are used to describe the dislocation cells evolution. The coupling of the substructure to the critical shear stresses is performed thanks to the concepts of isotropic hardening, latent hardening and polarity. Moreover, a ductility loss criterion, first introduced by Rice, based on the ellipticity loss of the elastic-plastic tangent modulus, is used in these two models to plot Ellipticity Loss Diagrams (ELD). Qualitative comparisons are made with experimental Forming Limit Diagrams (FLD) for ferritic steel involving simple and complex loading paths. In particular, it is shown that numerical ELD have a shape close to experimental FLD and reproduce qualitatively the effects due to complex loading paths. The impact of intragranular microstructure on strain localization is studied thanks to comparisons between ELD plotted with the two models.
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/10985/104452007-01-01T00:00:00ZFRANZ, GéraldABED-MERAIM, FaridBEN ZINEB, TarakLEMOINE, XavierBERVEILLER, MarcelThe development of a relevant constitutive model adapted to sheet metal forming simulations requires an accurate description of the most important sources of anisotropy, i.e. the slip processes, the intragranular substructure changes and the texture development. During plastic deformation of thin metallic sheets, strain-path changes often occur in the material resulting in macroscopic effects. These softening/hardening effects must be correctly predicted because they can significantly influence the strain distribution and may lead to flow localization, shear bands and even material failure. The main origin of these effects is related to the intragranular microstructure evolution. This implies that an accurate description of the dislocation patterning during monotonic or complex strain-paths is needed to lead to a reliable constitutive model. First, the behaviour at the mesoscopic scale (which is the one of the grain or the single crystal) is modelled by a micromechanical law written within large strain framework. Hardening is taking into account by a matrix whose internal variables are the mean dislocation densities on each slip system. This crystal plasticity based model is implemented into a large strain self-consistent scheme, leading to the multiscale model which achieves, for each grain, the calculation of plastic slip activity, with help of regularized formulation drawn from viscoplasticity. An improvement of this model is suggested with the introduction of intragranular microstructure description. The substructure of a grain is described taking into account the experimental observations as stress-strain curves and TEM micrographs. Following Peeters’ approach, three local dislocations densities, introduced as internal variables in the multiscale model, allow representing the spatially heterogeneous distributions of dislocations inside the grain. Rate equations, based on the consideration of associated creation, storage and annihilation, are used to describe the dislocation cells evolution. The coupling of the substructure to the critical shear stresses is performed thanks to the concepts of isotropic hardening, latent hardening and polarity. Moreover, a ductility loss criterion, first introduced by Rice, based on the ellipticity loss of the elastic-plastic tangent modulus, is used in these two models to plot Ellipticity Loss Diagrams (ELD). Qualitative comparisons are made with experimental Forming Limit Diagrams (FLD) for ferritic steel involving simple and complex loading paths. In particular, it is shown that numerical ELD have a shape close to experimental FLD and reproduce qualitatively the effects due to complex loading paths. The impact of intragranular microstructure on strain localization is studied thanks to comparisons between ELD plotted with the two models.Numerical tool for SMA material simulation: application to composite structure design
http://hdl.handle.net/10985/16041
Numerical tool for SMA material simulation: application to composite structure design
CHEMISKY, Yves; DUVAL, Arnaud; PIOTROWSKI, Boris; BEN ZINEB, Tarak; TAHIRI, Vanessa; PATOOR, Etienne
Composite materials based on shape memory alloys (SMA) have received growing attention over these last few years. In this paper, two particular morphologies of composites are studied. The first one is an SMA/elastomer composite in which a snake-like wire NiTi SMA is embedded into an elastomer ribbon. The second one is a commercial Ni47Ti44Nb9 which presents elastic–plastic inclusions in an NiTi SMA matrix. In both cases, the design of such composites required the development of an SMA design tool, based on a macroscopic 3D constitutive law for NiTi alloys. Two different strategies are then applied to compute these composite behaviors. For the SMA/elastomer composite, the macroscopic behavior law is implemented in commercial FEM software, and for the Ni47Ti44Nb9 a scale transition approach based on the Mori–Tanaka scheme is developed. In both cases, simulations are compared to experimental data.
Thu, 01 Jan 2009 00:00:00 GMThttp://hdl.handle.net/10985/160412009-01-01T00:00:00ZCHEMISKY, YvesDUVAL, ArnaudPIOTROWSKI, BorisBEN ZINEB, TarakTAHIRI, VanessaPATOOR, EtienneComposite materials based on shape memory alloys (SMA) have received growing attention over these last few years. In this paper, two particular morphologies of composites are studied. The first one is an SMA/elastomer composite in which a snake-like wire NiTi SMA is embedded into an elastomer ribbon. The second one is a commercial Ni47Ti44Nb9 which presents elastic–plastic inclusions in an NiTi SMA matrix. In both cases, the design of such composites required the development of an SMA design tool, based on a macroscopic 3D constitutive law for NiTi alloys. Two different strategies are then applied to compute these composite behaviors. For the SMA/elastomer composite, the macroscopic behavior law is implemented in commercial FEM software, and for the Ni47Ti44Nb9 a scale transition approach based on the Mori–Tanaka scheme is developed. In both cases, simulations are compared to experimental data.A multiscale model based on intragranular microstructure - Prediction of dislocation patterns at the microscopic scale
http://hdl.handle.net/10985/10476
A multiscale model based on intragranular microstructure - Prediction of dislocation patterns at the microscopic scale
FRANZ, Gérald; ABED-MERAIM, Farid; BEN ZINEB, Tarak; LEMOINE, Xavier; BERVEILLER, Marcel
A large strain elastic-plastic single crystal constitutive law, based on dislocation annihilation and storage, is implemented in a new self-consistent scheme, leading to a multiscale model which achieves, for each grain, the calculation of plastic slip activity, with help of regularized formulation drawn from visco-plasticity, and dislocation microstructure evolution. This paper focuses on the relationship between the deformation history of a BCC grain and induced microstructure during monotonic and two-stage strain paths.
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/10985/104762007-01-01T00:00:00ZFRANZ, GéraldABED-MERAIM, FaridBEN ZINEB, TarakLEMOINE, XavierBERVEILLER, MarcelA large strain elastic-plastic single crystal constitutive law, based on dislocation annihilation and storage, is implemented in a new self-consistent scheme, leading to a multiscale model which achieves, for each grain, the calculation of plastic slip activity, with help of regularized formulation drawn from visco-plasticity, and dislocation microstructure evolution. This paper focuses on the relationship between the deformation history of a BCC grain and induced microstructure during monotonic and two-stage strain paths.Effect of microstructural and physical mechanisms on mechanical properties of single-phase steels
http://hdl.handle.net/10985/10061
Effect of microstructural and physical mechanisms on mechanical properties of single-phase steels
FRANZ, Gérald; ABED-MERAIM, Farid; BEN ZINEB, Tarak
The current work aims to investigate the impact of microstructural and physical mechanisms on the macroscopic behavior and ductility of single-phase steels. For this purpose, an advanced multiscale model, accounting for intragranular microstructure development and evolution, is coupled with a formability limit criterion based on bifur- cation theory. The overall response for polycrystalline aggregates is obtained from a large-strain elastic-plastic single crystal constitutive law, using a self-consistent scale-transition scheme. This approach takes into account essential microstructural aspects such as initial and induced textures, dislocation densities, softening mecha- nisms so that the behav uring complex loading paths is properly described. Focus will be placed here on the relationship between intragranular microstructure of B.C.C. steels and their ductility. The model allows interesting qualitative study in terms of formability limits for various dislocation networks, during monotonic loading tests applied to single-phase steels, with the aim of helping in the design of new materials.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/100612013-01-01T00:00:00ZFRANZ, GéraldABED-MERAIM, FaridBEN ZINEB, TarakThe current work aims to investigate the impact of microstructural and physical mechanisms on the macroscopic behavior and ductility of single-phase steels. For this purpose, an advanced multiscale model, accounting for intragranular microstructure development and evolution, is coupled with a formability limit criterion based on bifur- cation theory. The overall response for polycrystalline aggregates is obtained from a large-strain elastic-plastic single crystal constitutive law, using a self-consistent scale-transition scheme. This approach takes into account essential microstructural aspects such as initial and induced textures, dislocation densities, softening mecha- nisms so that the behav uring complex loading paths is properly described. Focus will be placed here on the relationship between intragranular microstructure of B.C.C. steels and their ductility. The model allows interesting qualitative study in terms of formability limits for various dislocation networks, during monotonic loading tests applied to single-phase steels, with the aim of helping in the design of new materials.Impact of intragranular microstructure development on ductility limits of multiphase steels
http://hdl.handle.net/10985/10107
Impact of intragranular microstructure development on ductility limits of multiphase steels
FRANZ, Gérald; ABED-MERAIM, Farid; BEN ZINEB, Tarak; LEMOINE, Xavier; BERVEILLER, Marcel
In this paper, the effects of microstructure and deformation mechanisms on the ductility of multiphase steels are investigated. To this end, a formability criterion based on loss of ellipticity of the boundary value problem is coupled with an advanced multiscale model accounting for intragranular microstructure development and evolution. The spatially heterogeneous distribution of dislocations inside the grain is represented by three types of local dislocation densities. The resulting large strain elastic-plastic single crystal constitutive law (based on crystal plasticity) is incorporated into a self-consistent scale-transition scheme. The present contribution focuses on the relationship between the intragranular microstructure of B.C.C. steels and their ductility. The model allows interesting comparisons in terms of formability limits for different dislocation networks, during monotonic loading tests applied to polycrystalline aggregates.
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/10985/101072011-01-01T00:00:00ZFRANZ, GéraldABED-MERAIM, FaridBEN ZINEB, TarakLEMOINE, XavierBERVEILLER, MarcelIn this paper, the effects of microstructure and deformation mechanisms on the ductility of multiphase steels are investigated. To this end, a formability criterion based on loss of ellipticity of the boundary value problem is coupled with an advanced multiscale model accounting for intragranular microstructure development and evolution. The spatially heterogeneous distribution of dislocations inside the grain is represented by three types of local dislocation densities. The resulting large strain elastic-plastic single crystal constitutive law (based on crystal plasticity) is incorporated into a self-consistent scale-transition scheme. The present contribution focuses on the relationship between the intragranular microstructure of B.C.C. steels and their ductility. The model allows interesting comparisons in terms of formability limits for different dislocation networks, during monotonic loading tests applied to polycrystalline aggregates.Modeling of niobium precipitates effect on the Ni 47Ti 44Nb 9 Shape Memory Alloy behavior
http://hdl.handle.net/10985/10098
Modeling of niobium precipitates effect on the Ni 47Ti 44Nb 9 Shape Memory Alloy behavior
PIOTROWSKI, Boris; BEN ZINEB, Tarak; PATOOR, Etienne; EBERHARDT, André
Commercial Ni 47Ti 44Nb9 Shape Memory Alloy (SMA) is generally adopted for tightening applications thanks to its wide transformation hysteresis, compared with classical NiTi. Its sensibility to thermo-mechanical treatments allows it to be either martensitic or austenitic in a wide range of temperature, between -60 °C and 80 °C. A modeling of niobium precipitates effects on Ni 47Ti 44Nb9 SMA behavior is proposed. For this object, a two phase thermo-mechanical model is developed. It describes the global effective behavior of an elastoplastic inclusion (niobium precipitates) embedded within an SMA matrix. The constitutive law developed by Peultier et al. (2006) and improved by Chemisky et al. (2011) is adopted to model the matrix shape memory behavior. The elastoplastic constitutive law for inclusion is the one proposed by Wilkins with Simo and Hughes's radial return algorithm. The Mori-Tanaka scale transition scheme is considered for the determination of the effective constitutive equations. Obtained results highlight the effect of niobium precipitates on the thermomechanical behavior of Ni47Ti 44Nb9, and particularly on the corresponding hysteresis size. It appears that the niobium plasticity increases this hysteresis size. The developed constitutive law has been implemented in the ABAQUS Finite Element code and considered for the numerical prediction of the tightening pressure in a connection application
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/10985/100982012-01-01T00:00:00ZPIOTROWSKI, BorisBEN ZINEB, TarakPATOOR, EtienneEBERHARDT, AndréCommercial Ni 47Ti 44Nb9 Shape Memory Alloy (SMA) is generally adopted for tightening applications thanks to its wide transformation hysteresis, compared with classical NiTi. Its sensibility to thermo-mechanical treatments allows it to be either martensitic or austenitic in a wide range of temperature, between -60 °C and 80 °C. A modeling of niobium precipitates effects on Ni 47Ti 44Nb9 SMA behavior is proposed. For this object, a two phase thermo-mechanical model is developed. It describes the global effective behavior of an elastoplastic inclusion (niobium precipitates) embedded within an SMA matrix. The constitutive law developed by Peultier et al. (2006) and improved by Chemisky et al. (2011) is adopted to model the matrix shape memory behavior. The elastoplastic constitutive law for inclusion is the one proposed by Wilkins with Simo and Hughes's radial return algorithm. The Mori-Tanaka scale transition scheme is considered for the determination of the effective constitutive equations. Obtained results highlight the effect of niobium precipitates on the thermomechanical behavior of Ni47Ti 44Nb9, and particularly on the corresponding hysteresis size. It appears that the niobium plasticity increases this hysteresis size. The developed constitutive law has been implemented in the ABAQUS Finite Element code and considered for the numerical prediction of the tightening pressure in a connection application