An analysis of ductile fracture initiation toughness in iron, its binary alloys and nickel

Abstract

The ductile crack initiation toughness (J_IC) data, obtained for a number of single phase, essentially particle-free materials, have been analysed in light of the existing models for J_IC developed for engineering alloys having a substantial volume fraction of second phase particles. The mechanism of void nucleation ahead of the blunted crack and also the characteristic distance (l_C) of the void from the crack tip in single phase materials have been determined through a careful examination of the interrupted fracture toughness test specimens. The paper presents an approach to the calculation of J_IC in terms of the critical strain criterion model originally developed by Rice & Johnson and Ritchie & Thompson. This approach not only incorporates the experimentally measured l_C values but also the plastic flow related energy dissipation in the Hutchinson-Rice-Rosengren (HRR) zone beyond the process zone. It is shown that the suggested approach is capable of estimating J_IC for a number of single phase materials with a wide range of measured J_IC values.