Overlay Model

Abstract

So far, only linear kinematic hardening, Prager–Ziegler hardening, has been considered in the Simplified Theory of Plastic Zones (STPZ). Before the STPZ can be expanded in Chap. 7 to account for nonlinear kinematic hardening, some preliminary work is required to provide a suitable material model. In this chapter a material model is considered with multilinear kinematic hardening, the overlay model of Besseling. In the literature this model is often based on the idea of a material consisting of several layers, each of non-hardening material, but this is not purposeful in terms of the STPZ. Instead, several layers, each with linear kinematic hardening, are now coupled in a suitable manner. For this purpose, it is shown how the material parameters of the individual layers can be identified from a given multilinear stress–strain curve. A method is also proposed for trilinearizing a given arbitrary nonlinear stress–strain curve.