Effects of laser shock peening on the microstructure and fatigue crack propagation behaviour of thin AA2024 specimens

Laser shock peening (LSP) was performed on aluminium alloy AA2024 with a thickness of 2.0 mm. Microstructural studies using the electron back scatter diffraction (EBSD) technique were performed toquantify the micro-texture changes in the material through LSP. A residual stress analysis was performedusing synchrotron radiation and a hole drilling technique. Fatigue crack propagation (FCP) tests were performedto investigate the retardation effect of LSP residual stresses. Load versus crack opening displacementcurves were analysed to obtain the corrected values of load opening levels considering the effects ofthe residual stresses. Specimens with the LSP treatment reveal a significant retardation of the FCP. Thepresence of compressive residual stresses caused the crack closure effect, which increased the level ofcrack opening load and therefore reduced the effective load range. An original methodology to considerLSP-induced residual stresses on the FCP behaviour was proposed.