Fracture of metallic glasses at notches: Effects of notch-root radius and the ratio of the elastic shear modulus to the bulk modulus on toughness

The Anand-Su theory for large elastic-plastic deformations of metallic glasses is modified to account for the strongly nonlinear and eventually softening dilatational volumetric elastic response of these materials. Using this theory, we have conducted finite-element simulations of fracture initiation at notch tips in a representative metallic glass under Mode-I, plane-strain, small-scale-yielding conditions. We show that our theory predicts three important experimentally observed phenomena: (a) fracture initiates ahead of the notch root, where the mean normal stress reaches a maximum value; (b) the fracture toughness increases linearly with the square-root of the notch-tip radius; and (c) the fracture toughness decreases as the ratio of the elastic shear modulus to the bulk modulus increases. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.