Plastic instabilities and yielding in amorphous solids under pure shear

Abstract

The nature of mechanical yielding in amorphous materials under external loading is investigated using computer simulation. We study the plastic instabilities and yielding transition in a model amorphous solid of a binary Lennard-Jones mixture under pure shear deformation. We carefully examine the plastic instabilities in the pre- and post-yield regime and find that these occur via the so-called saddle-node bifurcation mechanism in the athermal quasistatic limit. To quantify the yielding transition, we use the overlap order parameter Q12, which has been successfully used in various glassy models. Our results show that the yielding transition is accompanied by a dramatic change in the structure of the material. We identify this as a first-order phase transition with a significant difference in the yielding transition point compared to the simple shear protocol.