Analysis of phase transformation in orthotropic elastoplastic materials under tension and shear

This study aims to investigate the possibility and features of stress-induced phase transformation in orthotropic elastoplastic materials with strain-softening behavior under complex stress state. The theory on multi-phase equilibrium is applied. Two-phase deformations in strips under tension and shear are analyzed for sixteen loading states. The features of the solutions are described in detail. It is shown that locally plastically deformed bands can indeed form in such materials and can spread along the length of the strips whilst the stresses in both phases remain unchanged, but, for thin-walled tubes under torsion, no localized bands can be observed and only homogeneous phase transformation on the whole tubes can occur. Influence of the values of the shear stress on inclination angles of the bands is revealed. All the predicted results are consistent with experimental observations.