FEM-implementation for two-surface cyclic plastic constitutive model with non-hardening region

This paper presents a generalized return mapping algorithm for two-surface cyclic plastic constitutive model with a non-hardening region in the framework of the finite element method (FEM). A complete algorithm of the above rate-independent constitutive model is presented under the assumption of small deformation. The use of implicit backward Euler method enables us to integrate the constitutive equations to the form of a single nonlinear algebraic equation, which is solved by the Pegasus method. The consistent tangent operator is obtained by linearizing the return mapping algorithm. Two numerical examples demonstrate the cyclic hardening and softening behavior, as well as the accuracy and robustness of the present algorithm.