A mixed finite element model for plane strain elastic-plastic analysis Part I. Formulation and assessment of the overall behaviour Original Research Article

The plane strain problem for elastically isotropic materials with a plastic behavior governed by von Mises condition is examined. By exploiting previous results, a mixed finite element formulation is established in this context. It is shown that if the trial functions for different fields comply with some conditions, the resulting finite element model not only is stable in the Babuska-Brezzi sense, but also retains the same stress redistribution capability of the equivalent displacement model, even if the inclusion relationships for which limitation principles apply are avoided. In particular, it is shown that locking does not occur when, as plasticity spreads, strains become nearly deviatoric and that collapse is correctly predicted in the perfectly plastic case.