Towards an accurate description of the anisotropic behaviour of sheet metals under large plastic deformations: Modelling, numerical analysis and identification

On the basis of the microstructural evolution after two-stage non proportional loading at finite strains, a so-called microstructural model was developed by Teodosiu and Hu (1995) that accurately describes the macroscopic anisotropic behaviour such as the Bauschinger effect, the work-hardening stagnation and the work-softening of polycrystalline metals. Many intragranular deformation mechanisms, corresponding to the formation and the evolution of persistent dislocation structures, have been taken into account in choosing the scalar and tensorial internal variables of the elastoplastic model and postulating their evolution equations. In the work discussed here, after a detailed description of Teodosiu-Hu model, several rheological tests and their numerical simulations on different polycrystalline materials are performed in order to evaluate the accuracy and the efficiency of the proposed model. To this aim, a sensitivity study of the material parameters is first carried out in order to show their different effects on the macroscopic behaviour. Therefore, a strategy for their identification is discussed. Regarding to the respective mechanical response of several materials, two simplifications of the proposed model are presented in order to take into account their specific behaviour. Finally, identification of the proposed models is performed and compared to more classical anisotropic work-hardening phenomenological models. (c) 2006 Elsevier Ltd. All rights reserved.