INTEGRATION OF PLASTICITY EQUATIONS FOR THE CASE OF ZIEGLER KINEMATIC HARDENING

An integration scheme is presented, aimed at obtaining accurate solutions of the equations of flow plasticity with general yield functions in the presence of Ziegler's kinematic hardening. The elastic-plastic rate problem is formulated within the Mathematical Programming framework introduced by Maier, the integration algorithm consists of a sequence of variable amplitude steps, each subdivided into a stable loading and a neutral loading substeps. The algorithm allows the error admissible on the yield condition and flow rule satisfaction to be prescribed a priori, thus incorporating an automatic criterion for subincrementation. Numerical results, providing indications about the accuracy and effectiveness of the integration scheme, are presented, mostly in the error contour plot method employed by Krieg and Krieg.