Influence of Flaw Shapes on Stress Intensity Factors for Pressure Vessel Surface Flaws and Nozzle Corner Cracks

Abstract

The influence of the flaw shape on the variation of stress-intensity factors along the crack front is examined for longitudinal inner surface flaws in pressure vessels, and for corner cracks present at the intersection of a pressure vessel and a nozzle. For the inner surface flaw problem, the geometry of the pressure vessel considered is that of a commercial pressure vessel. The analyzed flaw shapes are those recommended by the ASME Boiler and Pressure Vessel Code (Section III, App. G, 1977). In the case of corner cracks at nozzle-pressure vessel junctions, natural flaw shapes obtained through experiments are considered. A fully three-dimensional linear elastic hybrid displacement finite element procedure was used to analyze these problems of practical interest in pressure vessel analysis and design. The obtained solutions are compared with those in the literature using other numerical and/or experimental procedures, and a discussion of noted discrepancies is presented.