Three-dimensional mixed-mode stress intensity factors for deflected external surface cracks in thin and midsize-thick-walled spherical pressure vessels

Abstract

Normalized three-dimensional mixed-mode stress intensity factor (SIF) distributions are presented for deflected external surface cracks in thin- and midsize-thick-walled spherical pressure vessels. With an aim to build a library of SIF solutions, values of the governing parameters of the problem, namely crack deflection angle, normalized crack depth and crack shape aspect ratio, are changed within their practical ranges. The obtained results show that for a given case, increasing the deflection angle yields a decrease in mode-I SIFs and increases in mode-II and mode-III SIFs. It is also observed that as the normalized crack depth increases, SIFs generally increase along the crack front. The results also show that magnitudes of the normalized mixed mode stress intensity factors at the depth location for midsize-thick-walled vessels are lower than those of thin-walled spherical vessels. The crack deflection angle has the highest effect among all parameters, emphasizing the importance of this study. It is concluded that the presented SIF solutions can be used to assess damage tolerance of a spherical vessel with a deflected external surface crack.