Critical Study of Constitutive Relations for Finite Strain Inelasticity

摘要

A unique set of experiments has been conducted to study the response of three FCCalloys to abrupt changes of loading direction at finite strain using large strain compression and torsion experiments, as well as sequences of the two. Evolution of grain morphology, substructure and texture have been experimentally quantified. It was observed that in spite of differences in dislocation substructures and mechanisms of inelastic deformation, the nonproportional straining response of the two alloys which exhibited homogeneous deformation at the macroscale, type 3O4L stainless steel and OFHC Cu, was very similar. These experiments and complementary modelling effort have led to improved understanding of the relative roles of dislocation substructure and texture development in establishing anisotropy of the flow stress. Neither state-of-the-art internal state variable theories for finite inelasticity which employ only plastic spin to accountt for textural anisotropy or polycrystal continuum slip plasticity models which employ the Taylor assumption of uniform deformation gradient among grains are able to correlate the observed behavior. A macroscale internal state variable model was developed to address the anisotropic hardening associated with dislocation substructure development and texturing, consistent with experimental observations and with the physics of deformation processes. The model has been generalized to viscoplasticity with void growth effects. (MM).