Evaluation of the Potential of Laser Shock Peening Compared with Cold Expansion for Improving Fatigue Resistance of Riveted Lap Joints of Aerospace Grade 7175 Al Alloy

Cold expansion is widely used in repairing and manufacturing rivet lap joints inthe aerospace industry. However, it bears inherent disadvantages such asnonsymmetrical residual stress, considerable surface deformation, and tensilezones that may initiate cracks. Limited process flexibility makes it challenging tofully overcome these issues. Given its high penetration depth and flexibleparameter adjustments, laser shock peening (LSP) may offer a promisingalternative for treating rivet areas. To investigate the effects of LSP parameters onresidual stresses, a systematic parameter study is conducted, involving extensiveX-ray diffraction residual stress analyses and fatigue testing. Upon determiningan optimal parameter matrix, fatigue tests are conducted on laser-peened, cold-expanded, and untreated samples. Subsequently, an energy dispersive syn-chrotron X-ray investigation is performed in order to understand the effect of LSPon residual stress evolution and the local material behavior in rivet lap joints. Forthis experiment, laser-peened, cold-expanded, and untreated samples are sub-mitted to fatigue tests at defined cycles. The residual stress distribution aroundthe rivet area is then analyzed for each sample to evaluate residual stress stabilityand changes post-loading. As a final step, fracture surface analyses are performedvia optical and scanning electron microscopy.RESEARCH ARTICLEwww.aem-journal.comAdv. Eng. Mater. 2025, e202501335 e202501335 (1 of 18)