On the simplified modelling of front shapes of fatigue cracks

Abstract

A direct three-dimensional (3D) finite element modelling of fatigue crack growth in structural components still represents a formidable task due to a complex singular behaviour of the stress field along the crack front as well as strong non-linearities associated with material plasticity and the change of contact conditions between crack faces during the loading cycle. The complexity of the 3D numerical modelling of fatigue crack growth largely motivates the development of simplified approaches. This paper describes several possible approaches for the evaluation of front shapes of fatigue cracks. These approaches are based on the (1) elimination of the corner singularity effect, (2) predictions based on the first-order plate theory, (3) the equivalent thickness concept, and (4) the Iso-K criterion. This paper briefly outlines these simplified approaches and presents some theoretical predictions for the case of through-the-thickness cracks propagating in plates under quasi-steady-state conditions. The theoretical predictions are also compared with experimental observations.