Initiation of shear bands near a stress concentration in metallic glass

Instrumented contact experiments are performed on three metallic glasses to systematically study shear band formation near a stress concentration. The results suggest that high local stresses at a point in the glass are insufficient to initiate a shear band. Rather, the yield strength must be exceeded along the entire length of a viable shear path in order for a shear band to form. Because of this, conventional analyses to extract shear yield stresses from Hertzian contact experiments overestimate the glass strength by a factor of three or more. In contrast, the interpretation of shear band initiation as yield on a plane agrees with recent experimental observations on metallic glasses that pertain to the slip-line field, and can rationalize the experimental contact load measurements as well as the shear band path. 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.