Size-Dependent Fracture Toughness of Nanoscale Structures: Crack-Tip Stress Approach in Molecular Dynamics

Abstract

By adopting the local virial stress, the authors overcome the barrier of ambiguous crack-tip stress field in molecular dynamics (MD) simulations and perform direct calculations of fracture toughness. Both MD and corresponding continuum finite-element method (FEM) solutions indicate that fracture toughness measured in stress intensity factor (or energy release rate) decreases with the decreasing crack length. Accordingly, fracture toughness cannot be treated as a material constant when the crack length is several nanometers. The size-dependent behavior of fracture toughness is explained in terms of the size of the singular stress zone (the