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https://sam.ensam.eu:443
The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Sat, 24 Feb 2024 07:50:42 GMT2024-02-24T07:50:42ZDétermination des diagrammes de perte d’ellipticité par une approche micromécanique
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.Semi phenomenological modelling of the behavior of TRIP steels
http://hdl.handle.net/10985/8336
Semi phenomenological modelling of the behavior of TRIP steels
KUBLER, Régis; BERVEILLER, Marcel; BUESSLER, Pascal
A new semi-phenomenological model is developed based on a mean-field description of the TRIP behavior for the simulation of multiaxial loads. This model intends to reduce the number of internal variables of crystalline models that cannot be used for the moment in metal forming simulations. Starting from local and crystallographic approaches, the mean-field approach is obtained at the phase level with the concept of Mean Instantaneous Transformation Strain (MITS) accompanying martensitic transformation. Within the framework of the thermodynamics of irreversible processes, driving forces, martensitic volume fraction evolution and an expression of the TRIP effect are determined for this new model. A classical self-consistent scheme is used to model the behavior of multiphased TRIP steels. The model is tested for cooling at constant loads and for multiaxial loadings at constant temperatures. The predictions reproduce the increase in ductility, the dynamic softening effect and the multiaxial behavior of a multiphased TRIP steel
The authors are grateful to ArcelorMittal R&D for supporting this research.
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/10985/83362011-01-01T00:00:00ZKUBLER, RégisBERVEILLER, MarcelBUESSLER, PascalA new semi-phenomenological model is developed based on a mean-field description of the TRIP behavior for the simulation of multiaxial loads. This model intends to reduce the number of internal variables of crystalline models that cannot be used for the moment in metal forming simulations. Starting from local and crystallographic approaches, the mean-field approach is obtained at the phase level with the concept of Mean Instantaneous Transformation Strain (MITS) accompanying martensitic transformation. Within the framework of the thermodynamics of irreversible processes, driving forces, martensitic volume fraction evolution and an expression of the TRIP effect are determined for this new model. A classical self-consistent scheme is used to model the behavior of multiphased TRIP steels. The model is tested for cooling at constant loads and for multiaxial loadings at constant temperatures. The predictions reproduce the increase in ductility, the dynamic softening effect and the multiaxial behavior of a multiphased TRIP steelStrain 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.Distribution des contraintes dans l’acier bainitique 16MND5. Analyse expérimentale et modélisation polycristalline
http://hdl.handle.net/10985/10134
Distribution des contraintes dans l’acier bainitique 16MND5. Analyse expérimentale et modélisation polycristalline; Stress distribution in the 16MND5 bainitic steel. Experimental analysis and polycrystalline modeling
PESCI, Raphaël; INAL, Karim; BERVEILLER, Marcel; MASSON, Renaud
La nature biphasée de l’acier bainitique 16MND5 (ferrite/cémentite) fait de la Diffraction des Rayons X (DRX) l’outil privilégié pour déterminer les états de contrainte dans la phase ferritique (méthode des sin2 ψ). Couplés aux observations réalisées lors d’essais de traction (surface des éprouvettes et faciès de rupture), ces derniers ont permis d’établir des critères décrivant le comportement et l’endommagement du matériau à l’échelle cristallographique, aux points bas de la transition fragile-ductile ainsi qu’aux basses températures [−196 ◦C;−60 ◦C]. Au cours du chargement, l’endommagement est observé au Microscope Electronique à Balayage, tandis que les contraintes internes sont déterminées par DRX : l’état de contrainte dans la ferrite est inférieur à celui de la bainite (contrainte macroscopique), l’écart n’excédant pas 150 MPa. Un modèle polycristallin à plusieurs échelles est développé parallèlement aux mesures expérimentales : une formulation de type Mori–Tanaka est utilisée pour décrire le comportement élastoplastique d’un monocristal ferritique renforcé par des précipités de cémentite, le passage au polycristal étant réalisé par une approche autocohérente. La modélisation développée prend en compte l’influence de la température sur les états de contrainte dans chaque phase et inclut un critère de clivage (valeur critique de la contraite normale aux plans {100}), qui traduit l’endommagement du matériau : elle permet ainsi de prédire le comportement réel de l’acier 16MND5 en fonction de la température, et de prendre en compte le mode de rupture qui est fragile à partir de −120 ◦C. En outre, il est également possible de calculer les déformations des plans diffractants εϕψ, qui peuvent être comparées à celles mesurées par DRX : cela permet d’évaluer les déformations par orientation cristallographique.; The 16MND5 bainitic steel being a two-phase material (ferrite/cementite), the X-Ray Diffraction (XRD) is the most efficient tool to determine the stress states into the ferritic phase (sin2 ψ method). The latter, coupled to the observations realized during tensile tests (specimen surface and facies), have permitted to establish criteria to describe the behavior and the damaging processes of the material on a crystallographic scale, in the lower part of the ductile-to-brittle transition region and at lower temperatures [−196 ◦C;−60 ◦C]. During the loading, the damage is observed with a Scanning Electron Microscope, while the internal stresses are determined by XRD: the stress states are less important in ferrite than in bainite (macroscopic stress), the difference not exceeding 150 MPa. A multi-scale polycrystalline model is developed concurrently with the experimental measurements: a Mori–Tanaka formulation is used to describe the elastoplastic behavior of a ferritic single crystal reinforced by cementite precipitates, while the transition to the polycrystal is achieved by a self-consistent approach. The developed modeling takes into account the temperature effects on the stress states in each phase and includes a cleavage criterion (critical value of the stress normal to {100} planes), which expresses the damage of the material: thus, it enables to predict the actual experimental behavior of the 16MND5 steel in relation to temperature, and to take into account the failure process which is fragile from −120 ◦C. Besides, it is also possible to calculate the strains of the diffracting planes εϕψ, which can be compared to those measured by XRD: this enables to evaluate the heterogeneity of the strains for each crystallographic orientation.
Wed, 01 Jan 2003 00:00:00 GMThttp://hdl.handle.net/10985/101342003-01-01T00:00:00ZPESCI, RaphaëlINAL, KarimBERVEILLER, MarcelMASSON, RenaudLa nature biphasée de l’acier bainitique 16MND5 (ferrite/cémentite) fait de la Diffraction des Rayons X (DRX) l’outil privilégié pour déterminer les états de contrainte dans la phase ferritique (méthode des sin2 ψ). Couplés aux observations réalisées lors d’essais de traction (surface des éprouvettes et faciès de rupture), ces derniers ont permis d’établir des critères décrivant le comportement et l’endommagement du matériau à l’échelle cristallographique, aux points bas de la transition fragile-ductile ainsi qu’aux basses températures [−196 ◦C;−60 ◦C]. Au cours du chargement, l’endommagement est observé au Microscope Electronique à Balayage, tandis que les contraintes internes sont déterminées par DRX : l’état de contrainte dans la ferrite est inférieur à celui de la bainite (contrainte macroscopique), l’écart n’excédant pas 150 MPa. Un modèle polycristallin à plusieurs échelles est développé parallèlement aux mesures expérimentales : une formulation de type Mori–Tanaka est utilisée pour décrire le comportement élastoplastique d’un monocristal ferritique renforcé par des précipités de cémentite, le passage au polycristal étant réalisé par une approche autocohérente. La modélisation développée prend en compte l’influence de la température sur les états de contrainte dans chaque phase et inclut un critère de clivage (valeur critique de la contraite normale aux plans {100}), qui traduit l’endommagement du matériau : elle permet ainsi de prédire le comportement réel de l’acier 16MND5 en fonction de la température, et de prendre en compte le mode de rupture qui est fragile à partir de −120 ◦C. En outre, il est également possible de calculer les déformations des plans diffractants εϕψ, qui peuvent être comparées à celles mesurées par DRX : cela permet d’évaluer les déformations par orientation cristallographique.
The 16MND5 bainitic steel being a two-phase material (ferrite/cementite), the X-Ray Diffraction (XRD) is the most efficient tool to determine the stress states into the ferritic phase (sin2 ψ method). The latter, coupled to the observations realized during tensile tests (specimen surface and facies), have permitted to establish criteria to describe the behavior and the damaging processes of the material on a crystallographic scale, in the lower part of the ductile-to-brittle transition region and at lower temperatures [−196 ◦C;−60 ◦C]. During the loading, the damage is observed with a Scanning Electron Microscope, while the internal stresses are determined by XRD: the stress states are less important in ferrite than in bainite (macroscopic stress), the difference not exceeding 150 MPa. A multi-scale polycrystalline model is developed concurrently with the experimental measurements: a Mori–Tanaka formulation is used to describe the elastoplastic behavior of a ferritic single crystal reinforced by cementite precipitates, while the transition to the polycrystal is achieved by a self-consistent approach. The developed modeling takes into account the temperature effects on the stress states in each phase and includes a cleavage criterion (critical value of the stress normal to {100} planes), which expresses the damage of the material: thus, it enables to predict the actual experimental behavior of the 16MND5 steel in relation to temperature, and to take into account the failure process which is fragile from −120 ◦C. Besides, it is also possible to calculate the strains of the diffracting planes εϕψ, which can be compared to those measured by XRD: this enables to evaluate the heterogeneity of the strains for each crystallographic orientation.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.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.Impact of microstructural mechanisms on ductility limits
http://hdl.handle.net/10985/10108
Impact of microstructural mechanisms on ductility limits
FRANZ, Gérald; ABED-MERAIM, Farid; BEN ZINEB, Tarak; LEMOINE, Xavier; BERVEILLER, Marcel
In order to investigate the effects of microstructure and deformation mechanisms on the ductility of multiphase steels, 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 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/10985/101082011-01-01T00:00:00ZFRANZ, GéraldABED-MERAIM, FaridBEN ZINEB, TarakLEMOINE, XavierBERVEILLER, MarcelIn order to investigate the effects of microstructure and deformation mechanisms on the ductility of multiphase steels, 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 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.Effect of microstructural and morphological parameters on the formability of BCC metal sheets
http://hdl.handle.net/10985/10060
Effect of microstructural and morphological parameters on the formability of BCC metal sheets
FRANZ, Gérald; ABED-MERAIM, Farid; BERVEILLER, Marcel
The determination of forming limit strains in sheet metal forming industry is a useful way for quantifying metals in terms of formability. However, such forming limit diagrams (FLDs) remain very difficult to obtain experimentally. Therefore, the numerical prediction of forming limit strains represents a convenient alternative to replace this time consuming and expensive experimental process. Moreover, a combined theoretical-numerical model allows investigating the impact of essential microstructural aspects (e.g., initial and induced textures, dislocation density evolution, softening mechanisms, ...) and deformation mechanisms on the ductility of polycrystalline aggregates. In this paper, the impact of microstructural and morphological parameters, particularly the mean grain size, on the formability limit of BCC materials is investigated. To this end, an elastic-plastic self-consistent (EPSC) polycrystalline model, coupled with a bifurcation-based localization criterion, is adopted to numerically simulate FLDs. The FLDs thus determined using the Bifurcation-EPSC model for an IF-Ti single-phase steel are compared to the FLDs given by ArcelorMittal, demonstrating the predictive capability of the proposed approach in investigations of sheet metal formability. The role of the averaging scheme is also shown to be significant by comparing the critical limit strains predicted with the self-consistent scale-transition scheme to those obtained with the more classical full-constraint Taylor model. Finally, numerical simulations for different values of mean grain size are provided in order to analyze the impact of mean grain size on the formability of BCC metal sheets. In this study, an elastic-plastic self-consistent (EPSC) polycrystalline model is coupled with a bifurcation-based localization criterion to investigate relationships between microstructural and morphological properties and formability of single-phase BCC steels. The interest in such a combined theoretical-numerical prediction tool is to classify materials in terms of ductility and to optimize material properties or to design new grades of steel with enhanced in-use mechanical properties.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/10985/100602014-01-01T00:00:00ZFRANZ, GéraldABED-MERAIM, FaridBERVEILLER, MarcelThe determination of forming limit strains in sheet metal forming industry is a useful way for quantifying metals in terms of formability. However, such forming limit diagrams (FLDs) remain very difficult to obtain experimentally. Therefore, the numerical prediction of forming limit strains represents a convenient alternative to replace this time consuming and expensive experimental process. Moreover, a combined theoretical-numerical model allows investigating the impact of essential microstructural aspects (e.g., initial and induced textures, dislocation density evolution, softening mechanisms, ...) and deformation mechanisms on the ductility of polycrystalline aggregates. In this paper, the impact of microstructural and morphological parameters, particularly the mean grain size, on the formability limit of BCC materials is investigated. To this end, an elastic-plastic self-consistent (EPSC) polycrystalline model, coupled with a bifurcation-based localization criterion, is adopted to numerically simulate FLDs. The FLDs thus determined using the Bifurcation-EPSC model for an IF-Ti single-phase steel are compared to the FLDs given by ArcelorMittal, demonstrating the predictive capability of the proposed approach in investigations of sheet metal formability. The role of the averaging scheme is also shown to be significant by comparing the critical limit strains predicted with the self-consistent scale-transition scheme to those obtained with the more classical full-constraint Taylor model. Finally, numerical simulations for different values of mean grain size are provided in order to analyze the impact of mean grain size on the formability of BCC metal sheets. In this study, an elastic-plastic self-consistent (EPSC) polycrystalline model is coupled with a bifurcation-based localization criterion to investigate relationships between microstructural and morphological properties and formability of single-phase BCC steels. The interest in such a combined theoretical-numerical prediction tool is to classify materials in terms of ductility and to optimize material properties or to design new grades of steel with enhanced in-use mechanical properties.