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 K _IC from this critical H, we compare K _IC with deCelis' and the Mullins' results calculated directly from MD calculation, and get good agreement.