Three dimensional erosion geometry effects on the mode I stress intensity factor (SIF) of an inner crack emanating from an erosion's deepest point in an autofrettaged, pressurized, thick-walled cylinder are investigated. The three dimensional problem is solved via a standard FEM code. Autofrettage, employing the Von-Mises yield criterion based on Hill's model, is simulated by the code's thermal analysis capability and SIFs are determined by the nodal displacement method. Cracks with crack depth to wall thickness ratio, ȧ/W=0.5 to 0.25, whose ellipticity, a/c, varies between 0.5 and 1.5, and which emanates from an elliptical erosion are studied. The erosions studied are: a) semi-circular of 1-10% wall thickness, b) of varying curvature but with 5% depth, or c) have a 5% depth with ellipticity, d/h, varying from 0.3 to 2.0. In general, cracks at the cylinder bore have their SIFs reduced through autofrettage. The crack's 3-D character affects all cracks, but the erosion curvature and depth affect short crack SIFs. Circular erosions or cracks do not always produce the highest SIFs; thus, they should not always be used to determine the SIFs for fatigue life calculations.
|Number of pages||7|
|Journal||American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP|
|State||Published - 1 Dec 1998|