Fracture behaviour simulation of flawed full scale pressure vessel

Abstract

In 1985 a four year research programme in elastic-plastic fracture mechanics was initiated within the Nordic countries. The aim of the programme was to verify the methods used for fracture analysis of real structures. A large cylindrical pressure vessel, having dimensions resembling those of a nuclear reactor pressure vessel, was tested in 1986. An artificial sharp axial surface flaw was made on the inner wall of the vessel. One of the circumferential welds intersected the crack at its midpoint. Failure of the vessel occurred as local rupture in the weld area. A maintenance deck, which was located around the midsection of the pressure vessel, was partially removed so as to prevent interference with the expected vessel deformations upon pressurization. After the test, two three-dimensional nonlinear finite element analyses were performed taking into account the existence of the circumferential weld in the ligament. In the first case, the original flawed structure was modelled allowing for different stress-strain curves of the base and weld material. In the second analysis, the model included a short through-the-wall crack in the weldment. Additionally, a simple two-dimensional analysis was made assuming the crack to be infinitely long in the axial direction. A three-dimensional analysis was repeated without considering the effect of the maintenance deck. For fracture mechanics evaluation, J- integrals along the crack front were calculated. In this paper, results of the three-dimensional analyses are reported and compared to experimental findings.