A unified approach to the implicit integration of standard, non-standard and viscous plasticity models

It is shown how modern concepts to integrate the elasto-plastic rate equations of standard plasticity via an implicit algorithm can be generalized to plasticity without an explicitly defined yield surface and to overstress-type models of viscoplasticity, where the stress point can be located outside the loading surface. For completeness, a tangent operator is derived that is consistent with the update algorithm. Copyright (C) 2002 John Wiley Sons, Ltd.