Prediction of the growth rate for fatigue cracks emanating from cold expanded holes

Fastener holes in aircraft components are routinely cold expanded to improve fatigue life, although the precise level of improvement is difficult to quantify. This paper describes an attempt to predict the growth rate of a fatigue corner crack emanating from the bore of a cold expanded hole. The prediction is made using a three-dimensional finite element model of a cold expanded hole combined with a Paris law fit to fatigue data derived from tests for corner cracks emanating from a plain hole. Residual stresses in the finite element model are calculated from a simulation of the cold expansion process. Finite element predictions of fatigue crack growth rate are compared with experimental measurements giving adequate agreement.