Modelling of plastic anisotropy based on texture and dislocation structure

Abstract

Anisotropy and work hardening behaviour are the most significant material properties in sheet metal forming. Beside the initial anisotropy due to crystallographic texture, anisotropic hardening due to the evolution of the dislocation structure is observed at large prestrains. The developed model is a mixed hardening model in which the shape of the yield locus is generated from the texture and the dislocation structures are responsible for isotropic hardening and kinematic hardening. This microstructural evolution is modelled with three internal state variables and their evolution equations. Furthermore an elastoplastic tangent modulus is derived from the plasticity model. The model is constructed in the framework of dual potentials both in deviatoric stress space and plastic strain rate space. Finally, the flow stress evolution is computed for several strain-path changes.