Approximate Determination of J Integral for Cracked Structures

Abstract

A method, designated as the GSM method, for the assessment of the J integral of cracked components subjected to uniform normal stress is compared with the J_s procedure of the French RCC-MR construction code, designated here as the FC method, for centre cracked plates, single edge cracked plates, double edge cracked plates produced from X52 and X70 steels, and for longitudinally cracked pipe produced from X70 steel. The "reference" values of the J integral for cracked plates were calculated using the EPRI method. The main objective of the study was to show that the GSM method provides reliable predictions of the J integral for cracked plates and pipes. A comparison of results obtained using the GSM and FC methods shows that both methods provide similar results, although in most cases, the GSM method results are slightly more conservative than those predicted by the FC method. Both techniques yield conservative results for most fracture configurations when compared to the "reference" values of the J integral, while estimates for cracks with a relative length less than 1/8 were not found to be as conservative. External longitudinal semielliptical part-through cracks in X70 steel pipe were likewise predicted using the two approaches. When compared to FEM calculations and experimentally determined burst pressures, the magnitudes of the projected burst pressures were extremely similar to each other and were conservative.