A modified damage potential to predict crack initiation: theory and experimental verification

Mesh dependency of cavity growth model due to Rice and Tracey has been overcome by integrating it over a process zone surrounding the crack tip. This integral represents a modified damage potential. The critical value of the integral for crack initiation in SA333Gr.6 material has been determined analysing a CT specimen and comparing the computed J with the experimentally measured J-initiation value. The critical value of the integral was then used to compute J-initiation in other fracture specimens having different crack-tip constraints. The critical value was also used to predict crack initiation loads in three 8 in. straight pipes and three 8 in. elbows having different measure of through-wall circumferential flaws. The computed values have been compared with the experimentally measured values. A close agreement between the computed crack initiation loads with the experimentally measured values justified the usefulness of the present modified damage potential.