Analytical and numerical modelling of plasticity‐induced crack closure in cold‐expanded holes

Abstract

ABSTRACTThe aim of this research was the development of an analytical model for plasticity‐induced fatigue crack closure for cold expanded holes. This paper extends Nowell's plane stress model of plasticity‐induced crack closure for a plate with a circular hole and two radial symmetric cracks. The possibility of existence of an initial residual stress field is also taken into account. This model has potential to be applied to other cracked geometries and arbitrary residual stress fields, although the paper is focused on the study of cold‐expanded holes. Hole cold‐expansion is widely used in aircraft industry, for improving the fatigue performance of rivet holes by delaying fatigue crack propagation. This paper shows that the residual stress field due to cold‐expansion has a strong influence on the closure behaviour and therefore on fatigue crack propagation. The analytical model developed, was compared with finite element analyses of plasticity‐induced crack closure with and without residual stresses. Finally, the model was used to predict fatigue lives for some experiments recently reported in the literature for fatigue crack propagation from cold‐expanded holes. Predicted fatigue lives correlate well with experimental data.