MODELING EFFECTS OF DISLOCATION SUBSTRUCTURE IN POLYCRYSTAL ELASTOVISCOPLASTICITY

Microheterogeneity resulting from dislocation substructure evolution i s introduced into polycrystal elastoviscoplasticity through a second r ank tensorial internal state variable. This evolving tensorial variabl e operates at the scale of the grain to capture the effects of subgrai n scale dislocation substructures. The microheterogeneity resulting fr om dislocation substructure evolution is mapped to each single crysta l slip system as kinematic hardening and also affects the higher lengt h scale of intergranular constraints in a self-consistent manner. The anisotropy from the microheterogeneity internal state variable improve s the: trends of correlation between polycrystalline calculation macro scale responses (stress-strain curve. texture, and axial stresses deve loped during fixed-end torsion) and the experimental results. Elastic moduli under finite strains were experimentally measured to corroborat e numerical predictions. Calculations with the microheterogeneity inte rnal state variable compared better with the elastic moduli measuremen ts than did the Taylor model. (C) 1998 Elsevier Science Ltd.