Mixed mode brittle fracture and fatigue in support to structural integrity assessment of laminar flaws

Due to the orientation of the defects found in the vessels of Doel 3 and Tihange 2 Belgian nuclear power plants, those defects will be loaded in mixed mode (predominantly mode II). Based on this study, it is recommended for brittle failure to use the conservative R6 failure criterion and the normal stress propagation angle. For fatigue, the normal stress propagation angle can be used. For the crack propagation rate, no consensus is found in the literature, therefore the most conservative propagation rate is recommended.