Effect of cold expansion on fatigue performance of open holes

In this paper, residual stress measurements were made on aluminium alloy 2A12T4 open holes after cold expansion. By contrast, a finite element method (FEM) was also used to analyze the residual stress distribution around cold expansion hole. Then a series of uniaxial fatigue tests were carried out using specimens containing non-cold expanded holes and cold expanded holes to assess the effect of direct cold expansion process on fatigue performance of open hole. At last the fracture morphology of the specimens after fatigue test was examined by scanning electron microscopy. The results reveal that direct cold expansion technique could elevate about six times fatigue life. After cold expansion, fatigue crack of open holes always initiates on entrance face.