The <i>J</i> Integral as a Fracture Criterion

The path independent J integral, as formulated by Rice, can be viewed as a parameter which is an average measure of the crack tip elastic-plastic field. This together with the fact that J can be evaluated experimentally, makes a critical J value an attractive elastic-plastic fracture criterion. The JIc fracture criterion refers to crack initiation under plane strain conditions from essentially elastic to fully plastic behavior. Experiments supporting the validity of a JIc fracture criterion are presented in this paper. Values of the J integral were determined experimentally for two steel alloys, one of low and the other of intermediate strength. A review is given of the analytic support for the JIc fracture criterion. The range of applicability of the JIc concept, its limitations, and its advantages are also discussed.