An Efficient Return Algorithm for Non-Associated Mohr-Coulomb Plasticity

An efficient return algorithm for stress update in numerical plasticity computations is presented. The yield criterion must be linear in principal stress space, and can be composed of any number of yield planes. Each of these yield planes can have an associated or non-associated flow rule. The stress return and the formation of the constitutive matrix is carried out in principal stress space, where the manipulations simplify and rely on geometrical arguments. The singularities arising at the intersection of yield planes are dealt with in a straightforward way also based on geometric considerations. The method is exemplified on non-associated Mohr-Coulomb plasticity throughout the paper.