Mode I crack tip fields in amorphous materials with application to metallic glasses

Abstract

In this work, stationary crack tip fields in amorphous materials such as metallic glasses under mode I loading are studied to understand the factors that control crack tip plasticity and in turn impart toughness to those materials. For this purpose, finite element simulations under plane strain, small scale yielding conditions are performed. A continuum elastic-viscoplastic constitutive theory, which accounts for pressure sensitivity of plastic flow as well as the localization of plastic strain into discrete shear bands, is employed to represent the material behavior. The influence of internal friction and strain softening on the plastic zone, stress and deformation fields and notch opening profile is examined. It is found that higher internal friction leads to a larger plastic zone. Also, it enhances the plastic strain ahead of the notch tip but leads to a substantial decrease in the opening stress. Thus, it appears that a higher friction parameter promotes toughening of amorphous solids. The shear band patterns within the plastic zone and brittle crack trajectories around the notch root generated from the simulations match qualitatively with those observed in experiments.