On the influence of state of stress on ductile failure initiation in high strength steels

Abstract

The effect of stress state on the effective plastic strain to initiate ductile failure in three high strength steels is investigated. Circumferentially notched tension specimens were used, and failure initiation strains were correlated with a parameter which is a measure of the “triaxiality” of the stress state. Results are given for both in-plane and through-thickness directions in rolled plate. The failure initiation data, together with appropriate stress-strain fields, and estimates of characteristic lengths over which failure initiates, have been used to predict failure initiation at notches and at crack tips; conventional fracture mechanics parameters, such as K I at crack extension in small scale yielding are estimated for one of the high strength steels.