Laser peen forming (LPF) is a novel non-contact sheet metal forming process without detrimental thermal defects. High pressure shock waves induced by a focused laser pulse are applied on the workpiece surface to generate deformations. In this study, the deformation mechanisms induced by LPF are experimentally and numerically investigated under different experimental conditions. Experiments have shown that when keeping laser parameters constant, deformation mechanisms vary depending on the sample thickness. The results show that aluminum sheet samples of 0.25 mm in thickness bend concavely for pulse energy ranging from 0.2 to 0.5 J, while 1.75 mm aluminum sheets bend convexly under the same conditions. There is a transition thickness threshold of sheet metal at which the deformation mechanism changes from concave to convex with the increase of the sample thickness with certain levels of laser parameter. This transition thickness threshold is determined to be around 0.7-0.88mm with the studied process parameters. Experiments also show that as the pulse energy increases, the transition thickness of the bending deformation mechanism increases slightly. Under the concave deformation mechanism, the workpiece is more sensitive to pulse energy, while pulse energy is not a critical factor in the convex mechanism. A finite element analysis (FEA) is performed to simulate the LPF deformation process with different specimen thicknesses and loading conditions. The simulation results agreed well with experimental results.
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