ON ANISOTROPIC FINITE DEFORMATION PLASTICITY .1. A 2-BACK STRESS MODEL

Based on the scale-invariance approach to finite plasticity, a two-bac k stress model is proposed to describe phenomenologically the evolutio n of substructure or texture development. Each back stress obeys its o wn evolution and rotational rules. Different types of hardening rules are obtained on the basis of crystal slip and a scale invariance argum ent to account for different types of substructure evolution. An aniso tropic yield surface is used to consider directional hardening/softeni ng and distortion of the yield surface. The extension to include visco plastic effects is straightforward within the scale invariance approac h. The model is applied to analyze experimental data for uniaxial load ing, torsion of cylindrical specimens with fixed ends, and unconstrain ed torsion. The agreement between model predictions and experimental d ata is very good, despite the small number of adjustable parameters us ed.