... EN RELATION AVEC LES MICRO-STRUCTURES DE DISLOCATIONS Hakim Bougrab* et Karim Inal LPMM UMR C... more ... EN RELATION AVEC LES MICRO-STRUCTURES DE DISLOCATIONS Hakim Bougrab* et Karim Inal LPMM UMR CNRS 7554 - Ecole Nationale Supérieure d'Arts et Métiers, 4, rue Augustin Fresnel - 57078 Metz Cedex 3 - France * [email protected] ...
Dans certains procédés de mise en forme, tel que le laminage, l'apparition des contraintes résidu... more Dans certains procédés de mise en forme, tel que le laminage, l'apparition des contraintes résiduelles est inévitable et peut engendrer le flambage qui se traduit en défauts géométriques. Ceci exige la modélisation de ce phénomène d'instabilité mécanique afin de bien définir la forme et l'amplitude de ces défauts. Cela nécessite un modèle complet ayant des capacités pour le calcul du post-flambage. Dans le présent article, on présente un modèle de flambage possédant la faculté de détecter la charge critique du flambage et la forme post-flambée d'une plaque sous contraintes résiduelles. Des applications à des cas académiques et un cas de laminage seront aussi traités.
The paper deals with flatness defects prediction in thin plates which appear during rolling. Thei... more The paper deals with flatness defects prediction in thin plates which appear during rolling. Their origin is the roll stack thermo-elastic deformation. The combination of the elastic deflection, the thermal crown and the roll grinding crown results in a non-parallel bite. If the transverse roll profile is not an affinity of the incoming strip profile, differential elongation results and induces high stresses in the outgoing strip. The latter combine with the imposed strip tension force, resulting in a net post-bite stress field which may be sufficiently compressive locally to promote buckling. A variety of non-developable shapes may result, generally occurring as waviness, and classified as flatness defects (center waves, wavy edges, quarterbuckles…). The purpose of the present paper is to present a coupled approach, following [1] : a simple buckling criterion is introduced in the FEM model of strip and roll deformation, LAM3 / TEC3 [2]. The postbite stress field is in much better agreement with experiments if this treatment is used, as will be demonstrated.
* Corresponding author : Laboratoire de Physique et Mécanique des Matériaux - Ile du Saulcy - 570... more * Corresponding author : Laboratoire de Physique et Mécanique des Matériaux - Ile du Saulcy - 57045 Metz cedex 01 France, Tel : +33 (0)3 87 31 53 82, Fax : +33 (0)3 87 31 53 66, email address : [email protected] ... COUPLED AND UNCOUPLED APPROACHES ...
Abstract Assuming an equi-incremental mechanical work in each constituent in an intermediate mixt... more Abstract Assuming an equi-incremental mechanical work in each constituent in an intermediate mixture law, this article shows how this assumption avoids any arbitrary fitting parameter on the contrary of classical variants and focuses on the interest of this approach ...
ABSTRACT This paper describes the application of a steady state elastic–viscoplastic finite eleme... more ABSTRACT This paper describes the application of a steady state elastic–viscoplastic finite element model to the prediction of strip flatness and out of bite buckling during cold rolling of thin strips. This model is applied here to the last stand of a tinplate tandem cold mill. Results show that strip buckling reshuffles the non-homogeneous strip velocity profile just at the roll bite exit; strip stresses inside the roll bite are little impacted, so that roll stack deformation and roll force profile are not modified. The paper focuses on 'latent strip flatness', i.e. the profile in the transverse direction of the stress in the rolling direction. The profile predicted by the model far downstream the roll bite is in good agreement with shapemeter measurements only if strip buckling (i.e. manifest flatness) just at the roll bite exit and its interaction with the roll bite are considered, using a strong coupling of bite model and post-bite buckling model.
ABSTRACT A review of works on modelling of hot and cold rolling in the European area during the l... more ABSTRACT A review of works on modelling of hot and cold rolling in the European area during the last few years is presented. First, the mechanical and mathematical features of the papers reviewed are presented (rheological assumptions; friction law and contact treatment; time integration schemes; thermomechanical coupling; methods of solutions). Then the results obtained by the various research groups are presented. First hot rolling is investigated; the major problems addressed are then product geometry and thermal evolution with some applications to metallurgical evolution. Finally, papers about cold strip rolling are discussed; these mainly analyze elastic roll deformation (flattening by plane strain approaches, 3D roll bending studies) and its consequences on strip profile and flatness.
is an open access repository that collects the work of Arts et Métiers ParisTech researchers and ... more is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible.
International Journal of Mechanical Sciences, 2011
The paper presents a predictive model of the flatness defects, which appear during rolling of thi... more The paper presents a predictive model of the flatness defects, which appear during rolling of thin plates, the origin of which is the roll stack thermo-elastic deformation. The combination of the elastic deflection, the thermal crown and the roll grinding crown results in a non-parallel bite, and if the deformed roll transverse profile is not an affinity of the incoming strip profile, differential elongation results and induces high stresses in the outgoing strip. The latter, combined with the imposed strip tension force, result in a net post-bite stress field which may be sufficiently compressive locally to promote buckling. A variety of non-developable shapes may result, generally occurring as waviness (centre waves, wavy edges, quarter-buckles, etc.). This problem is most of the time addressed in a decoupled way, i.e. as a post-processing of the residual stresses computed by a strip rolling model; the present paper on the contrary describes a fully coupled approach of in-bite plastic deformation and post-bite buckling. For this purpose, a simple buckling criterion has been introduced in a FEM model of strip and roll deformation, Lam3/Tec3; its implementation is documented in details. The capabilities and limits of the present approach are described and discussed. Characterised by its coupled approach, it is primarily devoted to cases where on-line (under tension) manifested defects occur. It is shown that the impact of the post-bite, post-buckled stress field on the in-bite stress and strain fields is quite small in the cases investigated; however, subtle changes appear in the velocity field at bite exit, and this is sufficient to transform completely the post-bite stress field, which is found in much better agreement with measurements if such a coupled treatment is used.
Abstract: A technique for computing free surfaces by a steady state approach has been included in... more Abstract: A technique for computing free surfaces by a steady state approach has been included in the hot rolling code ROLL3. It has been described in a previous paper, along with applications to some simple rolling passes. In the present text, new developments are ...
Mechanical behaviour modelling of the heterogeneous materials is one of important fields of physi... more Mechanical behaviour modelling of the heterogeneous materials is one of important fields of physical metallurgy. The available solving methods can be classified in three main families. The first one is based on classical mixture rule widely used because very simple but it is not realistic or needs arbitrary fitting parameter to improve the prediction. The second one is based on homogenisation techniques like self-consistent method. The third one is based on finite element description of either a unit cell or a representative microstructure. It is able to be more accurate but much more difficult and heavy to perform, and therefore less used. To keep easy running mixture law modelling but to avoid any fitting parameter and improve prediction accuracy, an equi-incremental mechanical work has been assumed in each constituent in stressstrain mixture law.
ABSTRACT A semi-phenomenological model is developed based on a mean-field description of the TRIP... more ABSTRACT A semi-phenomenological model is developed based on a mean-field description of the TRIP behaviour for the simulation of metal forming processes [1]. Within the metastable austenitic phase exhibiting martensitic transformation, a mean field approach is introduced at the phase level with the concept of Mean Instantaneous Transformation Strain (MITS) accompanying transformation. Within the framework of the thermodynamics of irreversible processes, a transformation criterion and martensitic volume fraction evolution are determined. A multiscale scheme is used to model the behaviour of TRIP steels. The model reproduces the increase in ductility and the multiaxial behaviour of a multiphased TRIP steel. In this study, this new model is implemented in the finite element code Abaqus Explicit for metal forming simulations. The simulations are compared to experimental data. KeywordsTRIP steel-martensitic transformation-metal forming-finite element
ABSTRACT Many kinds of high strength thin steel wires are involved in so many applications. Most ... more ABSTRACT Many kinds of high strength thin steel wires are involved in so many applications. Most of the time, these wires are made of a pearlitic steel grade. The current developments mainly concern the wire last drawing operation: after a patenting treatment several reduction passes are performed on a slip-type multipass drawing machine. This paper focuses on modeling this multipass drawing process: a constitutive law based on the wire microstructure evolutions is created, a mechanical study is performed, a set of experiments which enables determining the process friction coefficients is suggested and finally the related analytical model is introduced. This model provides several general results about the process and can be used in order to set the drawing machines.
... EN RELATION AVEC LES MICRO-STRUCTURES DE DISLOCATIONS Hakim Bougrab* et Karim Inal LPMM UMR C... more ... EN RELATION AVEC LES MICRO-STRUCTURES DE DISLOCATIONS Hakim Bougrab* et Karim Inal LPMM UMR CNRS 7554 - Ecole Nationale Supérieure d'Arts et Métiers, 4, rue Augustin Fresnel - 57078 Metz Cedex 3 - France * [email protected] ...
Dans certains procédés de mise en forme, tel que le laminage, l'apparition des contraintes résidu... more Dans certains procédés de mise en forme, tel que le laminage, l'apparition des contraintes résiduelles est inévitable et peut engendrer le flambage qui se traduit en défauts géométriques. Ceci exige la modélisation de ce phénomène d'instabilité mécanique afin de bien définir la forme et l'amplitude de ces défauts. Cela nécessite un modèle complet ayant des capacités pour le calcul du post-flambage. Dans le présent article, on présente un modèle de flambage possédant la faculté de détecter la charge critique du flambage et la forme post-flambée d'une plaque sous contraintes résiduelles. Des applications à des cas académiques et un cas de laminage seront aussi traités.
The paper deals with flatness defects prediction in thin plates which appear during rolling. Thei... more The paper deals with flatness defects prediction in thin plates which appear during rolling. Their origin is the roll stack thermo-elastic deformation. The combination of the elastic deflection, the thermal crown and the roll grinding crown results in a non-parallel bite. If the transverse roll profile is not an affinity of the incoming strip profile, differential elongation results and induces high stresses in the outgoing strip. The latter combine with the imposed strip tension force, resulting in a net post-bite stress field which may be sufficiently compressive locally to promote buckling. A variety of non-developable shapes may result, generally occurring as waviness, and classified as flatness defects (center waves, wavy edges, quarterbuckles…). The purpose of the present paper is to present a coupled approach, following [1] : a simple buckling criterion is introduced in the FEM model of strip and roll deformation, LAM3 / TEC3 [2]. The postbite stress field is in much better agreement with experiments if this treatment is used, as will be demonstrated.
* Corresponding author : Laboratoire de Physique et Mécanique des Matériaux - Ile du Saulcy - 570... more * Corresponding author : Laboratoire de Physique et Mécanique des Matériaux - Ile du Saulcy - 57045 Metz cedex 01 France, Tel : +33 (0)3 87 31 53 82, Fax : +33 (0)3 87 31 53 66, email address : [email protected] ... COUPLED AND UNCOUPLED APPROACHES ...
Abstract Assuming an equi-incremental mechanical work in each constituent in an intermediate mixt... more Abstract Assuming an equi-incremental mechanical work in each constituent in an intermediate mixture law, this article shows how this assumption avoids any arbitrary fitting parameter on the contrary of classical variants and focuses on the interest of this approach ...
ABSTRACT This paper describes the application of a steady state elastic–viscoplastic finite eleme... more ABSTRACT This paper describes the application of a steady state elastic–viscoplastic finite element model to the prediction of strip flatness and out of bite buckling during cold rolling of thin strips. This model is applied here to the last stand of a tinplate tandem cold mill. Results show that strip buckling reshuffles the non-homogeneous strip velocity profile just at the roll bite exit; strip stresses inside the roll bite are little impacted, so that roll stack deformation and roll force profile are not modified. The paper focuses on 'latent strip flatness', i.e. the profile in the transverse direction of the stress in the rolling direction. The profile predicted by the model far downstream the roll bite is in good agreement with shapemeter measurements only if strip buckling (i.e. manifest flatness) just at the roll bite exit and its interaction with the roll bite are considered, using a strong coupling of bite model and post-bite buckling model.
ABSTRACT A review of works on modelling of hot and cold rolling in the European area during the l... more ABSTRACT A review of works on modelling of hot and cold rolling in the European area during the last few years is presented. First, the mechanical and mathematical features of the papers reviewed are presented (rheological assumptions; friction law and contact treatment; time integration schemes; thermomechanical coupling; methods of solutions). Then the results obtained by the various research groups are presented. First hot rolling is investigated; the major problems addressed are then product geometry and thermal evolution with some applications to metallurgical evolution. Finally, papers about cold strip rolling are discussed; these mainly analyze elastic roll deformation (flattening by plane strain approaches, 3D roll bending studies) and its consequences on strip profile and flatness.
is an open access repository that collects the work of Arts et Métiers ParisTech researchers and ... more is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible.
International Journal of Mechanical Sciences, 2011
The paper presents a predictive model of the flatness defects, which appear during rolling of thi... more The paper presents a predictive model of the flatness defects, which appear during rolling of thin plates, the origin of which is the roll stack thermo-elastic deformation. The combination of the elastic deflection, the thermal crown and the roll grinding crown results in a non-parallel bite, and if the deformed roll transverse profile is not an affinity of the incoming strip profile, differential elongation results and induces high stresses in the outgoing strip. The latter, combined with the imposed strip tension force, result in a net post-bite stress field which may be sufficiently compressive locally to promote buckling. A variety of non-developable shapes may result, generally occurring as waviness (centre waves, wavy edges, quarter-buckles, etc.). This problem is most of the time addressed in a decoupled way, i.e. as a post-processing of the residual stresses computed by a strip rolling model; the present paper on the contrary describes a fully coupled approach of in-bite plastic deformation and post-bite buckling. For this purpose, a simple buckling criterion has been introduced in a FEM model of strip and roll deformation, Lam3/Tec3; its implementation is documented in details. The capabilities and limits of the present approach are described and discussed. Characterised by its coupled approach, it is primarily devoted to cases where on-line (under tension) manifested defects occur. It is shown that the impact of the post-bite, post-buckled stress field on the in-bite stress and strain fields is quite small in the cases investigated; however, subtle changes appear in the velocity field at bite exit, and this is sufficient to transform completely the post-bite stress field, which is found in much better agreement with measurements if such a coupled treatment is used.
Abstract: A technique for computing free surfaces by a steady state approach has been included in... more Abstract: A technique for computing free surfaces by a steady state approach has been included in the hot rolling code ROLL3. It has been described in a previous paper, along with applications to some simple rolling passes. In the present text, new developments are ...
Mechanical behaviour modelling of the heterogeneous materials is one of important fields of physi... more Mechanical behaviour modelling of the heterogeneous materials is one of important fields of physical metallurgy. The available solving methods can be classified in three main families. The first one is based on classical mixture rule widely used because very simple but it is not realistic or needs arbitrary fitting parameter to improve the prediction. The second one is based on homogenisation techniques like self-consistent method. The third one is based on finite element description of either a unit cell or a representative microstructure. It is able to be more accurate but much more difficult and heavy to perform, and therefore less used. To keep easy running mixture law modelling but to avoid any fitting parameter and improve prediction accuracy, an equi-incremental mechanical work has been assumed in each constituent in stressstrain mixture law.
ABSTRACT A semi-phenomenological model is developed based on a mean-field description of the TRIP... more ABSTRACT A semi-phenomenological model is developed based on a mean-field description of the TRIP behaviour for the simulation of metal forming processes [1]. Within the metastable austenitic phase exhibiting martensitic transformation, a mean field approach is introduced at the phase level with the concept of Mean Instantaneous Transformation Strain (MITS) accompanying transformation. Within the framework of the thermodynamics of irreversible processes, a transformation criterion and martensitic volume fraction evolution are determined. A multiscale scheme is used to model the behaviour of TRIP steels. The model reproduces the increase in ductility and the multiaxial behaviour of a multiphased TRIP steel. In this study, this new model is implemented in the finite element code Abaqus Explicit for metal forming simulations. The simulations are compared to experimental data. KeywordsTRIP steel-martensitic transformation-metal forming-finite element
ABSTRACT Many kinds of high strength thin steel wires are involved in so many applications. Most ... more ABSTRACT Many kinds of high strength thin steel wires are involved in so many applications. Most of the time, these wires are made of a pearlitic steel grade. The current developments mainly concern the wire last drawing operation: after a patenting treatment several reduction passes are performed on a slip-type multipass drawing machine. This paper focuses on modeling this multipass drawing process: a constitutive law based on the wire microstructure evolutions is created, a mechanical study is performed, a set of experiments which enables determining the process friction coefficients is suggested and finally the related analytical model is introduced. This model provides several general results about the process and can be used in order to set the drawing machines.
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