A molecular-dynamics study of ductile and brittle fracture in model non-crystalline solids

TL;DR

This study uses molecular dynamics to explore how small changes in interatomic potentials affect ductile and brittle fracture behaviors in non-crystalline solids, revealing that fracture toughness can vary independently of flow stress.

Contribution

It introduces a simple model linking interparticle potential changes to strain rate sensitivity and shear transformation zone susceptibility in metallic glasses.

Findings

Fracture toughness varies with interatomic potential changes.

Flow stress remains unaffected despite embrittlement.

Strain rate sensitivity correlates with shear transformation zone behavior.

Abstract

Molecular-dynamics simulations of fracture in metallic glass-like systems are observed to undergo embrittlement due to a small change in interatomic potential. This change in fracture toughness, however, is not accompanied by a corresponding change in flow stress. Theories of brittle fracture proposed by Freund and Hutchinson indicate that strain rate sensitivity is the controling physical parameter in these cases. A recent theory of viscoplasticity in this class of solids by Falk and Langer further suggests that the change in strain rate sensitivity corresponds to a change in the susceptibility of local shear transformation zones to applied shear stresses. A simple model of these zones is develped in order to quantify the dependence of this sensitivity on the interparticle potential.