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Massive Laser Shock Peening of an Aluminium Alloy and the Effects of Overlapping Rate on Residual Stress Relaxation when Under Cyclic Loading
K.Y. Luo, Y.J. Zhu, T. Lin and J.Z. Lu

To investigate the effects of overlapping rate on the residual stress relaxation following laser shock peening (LSP) of LY2 Al-alloy, a three-dimensional (3-D) finite element analysis (FEA) model using ABAQUS software is developed to simulate the residual stress relaxation under three kinds of applied cyclic loadings. Special attention is paid to the residual stress relaxation process of the LY2 Al-alloy sheet with different overlapping rates. Results show that residual stress relaxation is strongly dependent of overlapping rate of massive laser shock peening treatment, and the fluctuation rate decreases with increasing overlapping rate. For all overlapping rates, the most drastic relaxation exists at a depth of 0.40 mm away from the top surface. With the overlapping rate being greater than 50%, the surface residual stress exhibits a better uniformity, and a maximum of in-depth residual stress after relaxation remains unchanged for a given cyclic loading. In addition, the influence mechanism of overlapping rate on stress relaxation after the first cycle is revealed.

Keywords: Nd:YAG laser, LY2 aluminium alloy, laser shock peening (LSP), finite element analysis (FEA), residual stress relaxation, cyclic loading

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