Fatigue analysis of different types of pressure vessel nozzle

This research aims at comparing two different methods for the construction of pressure vessel nozzles, designed with the same safety coefficient, according to ASME and VSR 1995 standards. It defines numerical and experimental analysis of behaviour under low-cycle fatigue for pulsating pressure. In particular, a nozzle with integral reinforcement, designed according to ASME standards, is compared to a nozzle with external reinforcement (applied reinforcement plate) designed according to VSR 1995 standards with the same safety coefficient. Strain gauge tests have been carried out on the plastic behaviour of the two structures in order to evaluate the expected fatigue life based on common criteria, using both the local strain and energetic approaches. At the same time, a FEM model of the nozzle with plate has been used to calculate numerically the expected fatigue life based on the same criteria. Finally, in order to identify the best system to exploit for design, comparisons are made of the fatigue life predictions, which are numerically and experimentally obtained and which are determined according to the standards of the two nozzle types to identify the better system.