Revisiting the effect of aspect ratio on shear band evolution by hydrostatic-stress embedded free-volume theory

The shear band evolution process induced by different aspect ratios was investigated by experiments and hydrostatic-stress embedded free-volume theory. It was found that specimen with lower aspect ratio displayed a higher compressive plasticity since the shear band propagation was confined by the machine head in a way of preventing the sample from fracturing along one major shear band. Hydrostatic-stress embedded free-volume theory was incorporated into ABAQUS as a user material subroutine UMAT. Numerical method was performed to reveal the shear band evolution caused by different aspect ratios. There was a good agreement between experiments and simulations. Furthermore, simulations demonstrated that sample with smaller aspect ratios yielded a relatively lower strain localization level, leading to a correspondingly stable plastic deformation process. Compared with the viscoelastic model, it showed that the current model could better describe shear band evolution history.