Approach of failure assessment of pressure vessels containing tilted cracks

According to existing failure assessment codes of structures containing defects, tilted cracks in pressure vessels are assessed by projecting the cracks onto principal planes and then analyzing the projections on the planes as I mode cracks. However, the projecting approach was developed on the basis of mixed mode fracture criteria of LEFM, so the applications in pressure vessels are beyond the confine of brittle fracture that seldom occurs in ductile materials. A theoretical explanation of two-criteria approach of failure assessment of flawed structures of materials hardening arbitrarily was generalized from that of materials hardening by Ramberg-Osgood's law which was given by EPRI. Assimilating the features and advantages of CEGB report R6-Res3, a failure assessment diagram of structures containing tilted cracks was proposed based on the recent advances in research of I-II mixed mode fracture in China using meso-mechanics of ductile metals.