A molecular dynamics-aided fracture mechanics parameter and its application to a tensile problem

Abstract

To evaluate fracture by a single parameter like J integral in molecular dynamics (MD) calculation, we propose a parameter derived by extending Ĵ integral to atomic model, being referred to as H-sum. To examine the path independence of H, we first apply H to a simple tensile problem of two dimensional model of α-iron by using molecular dynamics method. As a result, we confirm that H has the path independence within an accuracy of 8.5%. In addition, the validity of the proposed parameter is clarified by analyzing a problem of microscopic crack initiation and propagation process. H increases with increasing tensile stress and reaches a critical value when a crack initiates, and subsequently decreases with the crack growth. Calculating KIC from this critical H, we compare KIC with deCelis' and the Mullins' results calculated directly from MD calculation, and get good agreement.