EXTENDING THE FATIGUE LIFE OF MULTI-LAYER METAL JOINTS

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. Secondary bending in the joint also had a major influence, reducing the effectiveness of these life improvement techniques. Depending on the joint configuration, improvements in fatigue life ranged from nothing at all to a factor of about 40. Fretting appeared to be involved in the initiation of all cracks and where this occurred on faying surfaces only small, if any, improvements in fatigue life were obtained.