Normal stress effect on plastic yielding of notched metallic glass: a finite element simulation study

Abstract

The pressure or normal stress effect on the plastic yielding of metallic glasses (MGs) is still poorly understood due to their complex nature of deformation process. A knowledge on the internal stress distribution and evolution around the plastic shearing plane holds the key for understanding the above issue. In this study, we studied the plastic deformation process of a notched bulk metallic glass by finite element simulation using the von-Mises yielding criterion and Mohr-Coulomb yield criterion, respectively. The internal shear stress distribution and evolution on the notched shear plane was analyzed, and the yielding strength is extracted by averaging the shear stress on the shear plane. It was found that the plastic flow of MGs is greatly influenced by the pressure/normal stress effect as captured by Mohr-Coulomb yielding criterion, and the strength extracted with the criterion agrees well with that obtained from experiments. The effect of pressure/normal stress on the plastic flow of MGs are also discussed from the mechanistic viewpoint. Our results may help for understanding the underlying origin for the pressure/normal stress effect on the plastic flow of MGs.