A Three-parameter model for fatigue behaviour of circumferential surface flaws in pipes

A three-parameter model, recently proposed by the authors for part-through-cracked round bars, is employed herein to examine the shape evolution of a circumferential external surface defect in a metallic round pipe under fatigue loading. The elliptical-arc #aw presents an aspect ratio a"a%-/b%- (a%- , b%-"ellipse semi-axes) and a relative crack depth m"a/t, where a and t are the depth of the deepest point on the crack front and the pipe wall thickness, respectively. The third parameter of the model is the ellipse shifting s"a%- /a, which de"nes the distance of the ellipse centre from the external boundary of the pipe cross-section. Thick- and thin-walled pipes are considered. Fatigue crack propagation paths in the diagram of a against s and m are numerically obtained for di!erent initial #aw con"gurations under cyclic bending loading. ( 2000 Elsevier Science Ltd. All rights reserved.