Mixed mode fracture analyses for corner cracks in nuclear reactor pressure vessel

In real engineering structures and machine parts, manufacturing defects, structural defects, unpredictable environmental effects, multi-axial stress conditions, and overloads cause micro cracks formation in the structure, and micro cracks propagate over time and turn into macro cracks. When the crack reaches a critical size, it suddenly becomes unstable and fracture occurs. Knowing how a cracked structure will behave under different load and boundary conditions is essential to prevent possible disasters and accidents. In this thesis, mixed mode fracture analyses for three-dimensional semi-elliptical corner cracks with different sizes and different inclination and deflection angles in the nozzle-cylinder region of the AP1000 reactor pressure vessel were performed, and stress intensity factors, KI, KII and KIII, along the crack front were obtained. Empirical equations were developed using the obtained stress intensity factor values. The developed empirical equations were applied to the studies in the literature, and the verification of the developed equations and numerical analysis results was carried out.