Diffuse instability of slightly disordered quasi rate-independent anisotropic viscoplastic FCC-polycrystals

Geometry and kinematics of intragranular as well as intergranular plastic deformation of polycrystals are briefly discussed. Elastic strain is covered by the effective medium homogenization method inside a representative volume element (RVE). Evolution equation formed by tensor representation is derived from very simple micro-evolution equation. It has an incremental quasi rate-independent (QRI) form obtained by Vakulenko's concept of thermodynamic time. The rate dependence takes place by means of stress rate dependent value of the initial yield stress. In accordance with Zorawski's communication about free macro rotations in intermediate reference configuration, strain geometry is based on constrained micro rotation within a representative volume element (RVE). The theory is applied to slightly disordered fcc-polycrystals. A comparison between QRI and classic diffuse instability equations is presented for transversely isotropic polycrystals. (C) 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ECF22 organizers.