Cold Expansion and Interference for Extending the Fatigue Life of Multi- Layer Metal Joints

Abstract : The influences of both hole cold expansion and interference-fit fasteners for extending the fatigue life of multi-layer aluminium alloy joint specimens under variable-amplitude loading have been examined experimentally. Improvements in fatigue life were markedly dependent on the degree of load transfer in the specimen joint. The cold expansion of fastener holes enhanced fatigue life in low-load-transfer joints but not in 100%-load-transfer joints. The use of interference-fit fasteners, especially at high degrees of interference, was an effective means of life improvement irrespective of proportion of load transfer. Interfacial fretting limited the improvement in fatigue life of low-load-transfer joints to a factor of about 6, and, although some fretting occurred in 100%-load-transfer joints it was not determinative, and a 40-fold increase in fatigue life was obtained with a combination of hole cold expansion and interference-fit fastener. Joints, Expansion, Aluminum alloys, Cold working, Fatigue life, Interference fit devices, Holes(Opening), Fasteners