A new fixed-point algorithm for hardening plasticity based on non-linear mixed variational inequalities

Moving from the seminal papers of Han and Reddy, we propose a xed-point algorithm for the solution of hardening plasticity two-dimensional problems. The continuous problem may be classi ed as a mixed non-linear non-di erentiable variational inequality of the second type and is discretized by means of a truly mixed nite-element scheme. One of the main peculiarities of our approach is the use of the composite triangular element of Johnson and Mercier for the approximation of the stress eld. The nondi erentiability is coped with via regularization whereas the non-linearity is approached with a xedpoint iterative strategy. Numerical results are proposed that investigate the sensitivity of the approach with respect to the mesh size and the regularization parameter . The simplicity of the proposed xedpoint scheme with respect to more classical return mapping approaches seems to represent one of the key features of our algorithm