LAUSR

Abstract An analytical micromechanics-based yield criterion is developed to describe both void growth and coalescence under combined tension and shear, with smooth transition between growth and coalescence, thus its name unified. The model is obtained by limit analysis over a cylindrical elementary cell embedding a coaxial cylindrical void of finite height. The velocity field employed is an extended counterpart of the discontinuous, yet kinematically admissible trial field utilized in a recent work. Plasticity in the deformable matrix is modeled using rate-independent J 2 flow theory, and the effective dissipation function is calculated by exact as well as approximate integration techniques, the latter generating a simpler flow potential. The model is aimed to predict void growth as well as coalescence by internal necking or shearing. The complete yield surface, being function of normal as well as shear stresses, exhibits curved and planar parts signifying void coalescence. The transition between the curved and planar parts is cornerless. The analytical predictions are compared to results of FEM single-step cell-model calculations of limit analysis executed on an identical geometry exposed to quasi-periodic boundary conditions.