Two-Step Exact Solution for Modified Mohr-Coulomb Viscoplastic Consistency Model with Linear Hardening/Softening: A Proof with Maple Software

It has been observed numerically that the viscoplastic consistency model by Wang (1997) with a linear yield surface and a linear hardening/softening rule converges, using the standard stress return mapping, with two steps. In this paper this numerical observation is proved analytically using the Maple software. The proof is carried out for the Modified Mohr-Coulomb viscoplastic consistency model in the corner plasticity situation, i.e. when both the Rankine and Mohr-Coulomb criteria are violated.