Uniform arrays of unequal-depth cracks in thick-walled cylindrical pressure vessels. Part II. The inter-crack stress field

In part one of this paper it was suggested that the variation of the SIF at the tip of the varying cracks reflects, in fact, the characteristics of the stress field prevailing in the inter-crack region, prior to the introduction of these cracks. Therefore, using the FE method, the inter-crack stress field is investigated for various geometrical configurations, and the dependence of its characteristic parameters on the inter-crack region aspect-ratio is determined. Under service conditions, it may sometimes occur that the penetration of the internal pressure into the crack cavity is only partial. Therefore, the effect of the actual fraction of the internal pressure, acting on the cracks faces is also analysed. Once the inter-crack stress field is characterized, its effect on the initial values of the stress intensity factor of the varying cracks is determined. Finally, based on all the results obtained in both parts of this paper, a possible scenario of the time sequence of the cracking process of the vessel is suggested and discussed.