Analysis of a Crotch corner crack in the shell-nozzle junction of a cylindrical pressure vessel under internal pressure using the J-integral method

This paper implements the J-integral method to numerically analyze a crotch corner crack in the shell-nozzle junction of an internally pressurized cylindrical pressure vessel, which is used in oil and gas industry. Firstly, by using the three-dimensional domain integral method and for linear elasticity, the equations to calculate the J-integral have been derived. The distinct advantage of using this integral in fracture mechanics is its ability to accurately estimate the stress intensity factor of the crack at points far from its tip, where the stress and strain gradients are high. Secondly, the implementation of the methodology in Abaqus software is described in detail. The methodology can be extended to other locations of vessels and various types of cracks. In order to verify the model, numerical results have been compared with the analytical ones, and a good conformity between them was observed. In fact, the largest difference of 30% is due to correction and safety factors which are considered in WRCB-175. The path independence of the J-integral was also observed for all contours with the error less than 0.15%. In general, the outputs of this research will help inspectors and safety engineers involved in the oil, gas and petrochemical industry to make a more accurate assessment of the safety and health status of equipment.