CRACKS EMANATING FROM AN EROSION IN A PRESSURIZED AUTOFRETTAGED THICK-WALLED CYLINDER - PART I - SEMICIRCULAR AND ARC EROSIONS

Erosion geometry effects on the mode I stress intensity factor (SIF) f or a crack emanating from the erosion's deepest point in an autofretta ged, pressurized, thick-walled cylinder are investigated The problem i s solved via the FEM method and knowledge of the asymptotic behavior o f short cracks. Autofrettage, based on von Mises yield criterion, is s imulated by thermal loading and SIFs are determined by the nodal displ acement method. SIFs are evaluated for a variety of relative crack len gths, a(o)/W = 0.01 - 0.45, emanating from the tip of erosions of diff erent geometries. In Part I of this paper, two configurations are cons idered: (a) semi-circular erosions of relative depths of 5 percent of the cylinder's wall thickness, W; and (b) are erosions for several dim ensionless radii of curvature, r'/W = 0.05 - 04. While deep cracks are almost unaffected by the erosion, the effective SIF for relatively sh ort cracks is found to be significantly enhanced by the presence and g eometry of the erosion and might reduce the vessel's fatigue life.