Finite element modelling of the interaction of residual stress with mechanical load for a crack emanating from a cold worked fastener hole

Abstract

A three-dimensional finite element simulation has been conducted for the cold working of a fastener hole in an aluminium plate. The simulation predicts the residual stress distribution resulting from the cold working process where an oversize mandrel is pulled though the fastener hole. Following the cold working simulation, unidirectional tensile mechanical load is applied to the plate and the resulting redistribution of stress predicted. Parallel through-the-thickness cracks emanating from the hole are then introduced into the model and crack opening displacements and stress intensity factors are predicted along the crack front as a function of applied mechanical load. The finite element simulation shows that cold working has a beneficial effect by reducing the stress intensity factor for a crack under applied mechanical load compared to a non-cold-worked plate. However, this improvement is less than would be expected if the cold working process is idealized as the application of a uniform radial expansion at the hole edge.