Effect of internal cracking on fatigue life of 7050 aluminium alloy treated by laser shock processing

Laser shock peening (LSP) is a promising surface treatment for fatigue life extension of metallic materials. The benefits include deeper residua; stresses (1-2 mm) and a smoother surface finishing than conventional glass bead peening. However, tests on round 7050 aluminium alloy dogbone specimens have shown that LSP may cause a reduction in fatigue life, due to the internal cracks, if the process is not optimised. A series of tests were designed to identify any technological risks such as internal cracking associated with the use of LSP in fatigue-critical aluminium aircraft structure. A numerical model was also developed to predict the damage induced by LSP process. The results of the numerical prediction well agree with the experimental results