Evaluation of J Integral for Center-Cracked Plate under Gross and General Yieldings and Its Application to Fatigue Crack Growth

Abstract

Several proposed procedures of J integral estimate for center-cracked plates under gross and general yielding conditions were examined based on the finite element analysis. The J values derived through the compliance method, the simple method proposed by Rice et al. and its modified method were compared with those determined by the line integral method. The compliance method was applicable for the case where the energy in load vs. load-point displacement curve changed large with respect to crack length. Rice's method was not applicable for the region of the crack length relative to the specimen width a/W less than 0.4. The best evaluation method that was applicable for a wide range of a/W was found to be the modified Rice's method in which the crack-center opening displacement was used instead of the load-point displacement. The mechanical foundation for the modified method was clarified and the limitations of other methods were discussed.
Fatigue crack growth tests in center-cracked specimens of a low-carbon steel under general yielding were conducted to confirm applicability of each estimate method to fatigue crack growth. The relation between the crack growth rate and the J integral range obtained by each estimate procedure was examined experimentally, and it was found that the midified Rice's method yielded the best correlation for a wide range of the crack length relative to the specimen width.