Studies of scale dependent crystal viscoplasticity models

A scale dependent crystal viscoplasticity model with a second strain gradient effect is introduced, as a simple extension of the conventional crystal plasticity theory. We confine attention to a sing e crystal undergoing slip on a single slip system under small strain conditions. Connections between this model and other existing theories are investigated in some detail. Furthermore, some basic predictions of the model, due to the second gradients and the material viscosity, are illustrated, using a constrained simple shear problem for a thin strip bounded by two rigid walls. The effect of viscosity on evolution of the boundary layer is examined, as well as the behavior of the thin strip undergoing reverse/cyclic shear loading, and the ability to predict plastic flow localization. (c) 2006 Elsevier Ltd. All rights reserved.