Detection of multiple active yield conditions for Mohr Coulomb elasto-plasticity

Abstract Singularity indicators that detect if multiple yield surfaces are active and include isotropic hardening/softening for associated Mohr-Coulomb elasto-plasticity are derived. These indicators identify corner and apex singularity regions of the Mohr-Coulomb surface and can be easily incorporated in computer codes. If multiple yield surfaces are seen to be active, a multivector stress return can be initiated. A novel inverted pyramid for the apex singularity region is proposed. Implications of strain and work hardening hypotheses are discussed. Illustrative examples are included.