Elastic-plastic analysis of a nozzle corner crack by finite element method

Abstract

The paper presents the results of an elastic-plastic three-dimensional finite element analysis for a nozzle corner crack in a pressurised reactor test vessel. The calculations were performed by the finite element program ADINA incorporating von Mise's yield condition and isotropic hardening. The crack plane was taken parallel to the axis of the vessel and the crack front straight and perpendicular to the symmetry line of the nozzle corner in order to obtain the worst position for a nozzle corner crack. The calculations were performed up to that pressure level where general yield of the ligament in the nozzle corner section takes place. For the chosen crack length, which is relatively small in comparison to the ligament, the crack opening stress as well as the crack opening displacement have a maximum in the centre of the crack. The differences between the maximum and minimum values along the crack front increase rapidly in the plastic range when the pressure load is raised above half of the general yield pressure. The results of the finite element analysis are compared with figures obtained from analytical procedures of elastic-plastic fracture mechanics.