CRACKS EMANATING FROM AN EROSION IN A PRESSURIZED AUTOFRETTAGED THICK-WALLED CYLINDER - PART II - EROSION DEPTH AND ELLIPTICITY EFFECTS

In Part I of this paper. the effects of constant depth erosion on the mode I stress intensity factor (SIF) were determined for a crack emana ting from the erosion deepest point in a pressurized, autofrettaged th ick-walled cylinder. The erosion geometries investigated included semi -circular erosions and several arc erosions of various radii of curvat ure. Due to the trends found in that portion of the study, erosion dep th and ellipticity are believed to have equally important impact on th e SIFs. The present paper delves further into these two parameters usi ng the following configurations: (a) semi-circular erosions of relativ e depths of 1-10 percent of the cylinder's wall thickness, W; and (b) semi-elliptical erosions with ellipticities of d/h = 0.3 - 2.0. Deep c racks are found to be practically unaffected by the erosion, similar t o the results presented in Part I of the paper The effective SIF for r elatively short cracks is found to be dramatically enhanced by the str ess concentration factor (SCF), which encompasses the depth of the ero sion as well as its radius of curvature at the tip. As a result of the increased effective SIF, a significant decrease in the vessel's fatig ue life of up to an order of magnitude may occur.