Implicit non locality in the framework of viscoplasticity

Abstract

The considerations are addressed to the notion of implicit nonlocality in mechanical models. The term implicit means that there is no direct measure of nonlocal action in a model (like classical or fractional gradients, etc. in explicit nonlocal models), but some phenomenological material parameters can be interpreted as one that maps some experimentally observed phenomena responsible for the scale effects. The overall discussion is conducted in the framework of the Perzyna Theory of Viscoplasticity where the role of the implicit length scale parameter plays the relaxation time of the mechanical disturbance. In this sense, in the viscoplastic range of the material behavior, the deformation at each material point contributes to the finite surrounding. The important consequence is that the solution of the IBVP described by Perzyna's theory is unique - the relaxation time is the regularizing parameter.