Investigation of cold expansion of short edge margin holes with pre-existing cracks in 2024-T351 aluminium alloy

The United States Air Force has requirements to inspect and cold expand potentially thousands of fastener holes for an aircraft fleet, and the presence of existing cracks at those fastener holes is expected. Fatigue experiments were performed to investigate the resulting fatigue crack growth life of a fastener hole that contained a representative 'unknown' crack at the time of inspection (approximately 0.050 in. in length) at a short edge margin hole that was then cold expanded and compare that to a non-cold expanded hole and a cold expanded hole with no pre-existing cracks. The United States Air Force analytical approach used to account for the benefit due to cold expansion was compared to the experimental data and does not consistently provide conservative predictions.