Weight function method to determine stress intensity factor for semi-elliptical crack with high aspect ratio in cylindrical vessels

Failure of cylindrical vessels can be caused by stress singularity at pitting corrosion induced cracks. Literature suggests that most of research focuses on stress intensity factors for surface cracks with low aspect ratios, i.e., a/c < 1.0. Situation may well arise where the aspect ratio of cracks is larger than one. This paper attempts to propose a weight function method to determine stress intensity factors for high aspect ratio semi-elliptical cracks in cylindrical vessels. The weight functions are derived based on three dimensional finite element analysis. The proposed weight function method is verified both numerically and analytically. It is found that the higher the aspect ratio of cracks the larger the stress intensity factors at the surface point, and that the aspect ratio of cracks tends to change the distribution of stress intensity factor along the cracks which can alter the failure mode of cylindrical vessels. The paper concludes that the proposed weight function method can serve as a useful tool for the accurate and efficient prediction of stress intensity factors for longitudinal surface cracks with various aspect ratios in cylindrical vessels subjected to arbitrary loads.