A model of the mechanics of shear-crack propagation in tearing for amorphous metals I. Critical shear stress for inhomogeneous flow

Abstract

A model of the mechanics of shear-crack propagation in tearing is proposed, from which the critical shear stress (τ) of inhomogeneous flow of an amorphous metal can be determined. Rivlin and Thomas energy-balance approach for the tear energy (γ) associated with shear-crack extension, combined with the two assumptions of a slip-hand separation mode of an ideal elastic-plastic solid and a constant applied force criterion for tearing, provide a basis for the new formula Γ/2 = τt, where t is the plate thickness. Predictions based on the proposed mechanics have been experimentally validated. The tear energy measured for an amorphous Pd₈₀Si₂₀ alloy was found to he proportional to the plate thickness. The deformation mode ahead of a shear-crack tip on the specimen surface appears as a single shear band. The characteristics of the derived critical shear stress are discussed in terms of yield criteria.