A model of the threshold stress intensity factor, KIH, for delayed hydride cracking of Zr–2.5Nb alloy

An analytical model to predict a threshold stress intensity factor, KIH, for delayed hydride cracking of Zr–2.5Nb alloy was developed based on a criterion to fracture hydrides: σmaxA(rc)+σh(rc)=σfh. The hydride platelet is assumed to cover a process zone ahead of the crack tip. By using the cohesive zone model and von Mises yield criterion at the boundary of the cohesive zone, the cohesive stress and the cohesive zone length (or the process zone length) were determined. The maximum stress and a critical distance in the process zone, corresponding to its occurrence, were obtained by assuming an elastic and linearly plastic materials with a constant tangent modulus, Et. The feasibility of the developed KIH model was discussed by comparing the predicted KIH with the measured one by accounting for a temperature dependence of KIH.