PART-THROUGH CRACKS IN PIPES UNDER CYCLIC BENDING

The propagation of a circumferential external surface crack in a metal lic round pipe under cyclic bending loading is examined through a two- parameter theoretical model. A finite element analysis is carried out to determine the stress-intensity factor distribution along the front of the flaw, which is assumed to present an elliptical-are shape with aspect ratio alpha = a(cl)/b(cl) (a(cl), b(cl) = ellipse semi-axes). T he relative depth xi of the deepest point on the front is equal to the ratio between the maximum crack depth, a, and the pipe wall thickness , t. The parameter R/t, with R = internal radius of the pipe, is made to vary from 1 to 10. The fatigue growth of the surface flaw occurs ac cording to preferred paths in the diagram of alpha against xi, (C) 199 8 Elsevier Science S.A. All rights reserved.