Laser shock forming (LSF) of sheet metal is a new technique realized by applying an impulsive pressure generated by a laser-induced shock wave on the surface of metal sheet. Our objective is to examine the deformation and the surface quality of LSF. LSF of a brass metal sheet is investigated using a Q-switched Nd:YAG laser with an energy per pulse of 15 to 50 J. The microhardness, roughness, and microstructure of the processed brass specimen are examined. ABAQUS software is employed to simulate the LSF process. The central displacement of the shocked region is measured and compared with the simulation. The results reveal that the microhardness of the brass specimen increases by about 20% because of the LSP treatment, and the surface quality and the microstructure has no visible change: LSF is a mechanical process, not a thermal process, and no remarkable ablation is observed. The higher the pulse energy, the higher is the central displacement of the shocked region obtained. The deformation of the simulation matches the experiment quite well.
We theoretically investigate the evolvement of dark spatial soliton with cascading quadratic nonlinearity in quasi-phase-matched second harmonic generation. It is shown that the dark solitary wave can propagate stably when background intensity is large enough, in which diffraction of beam can be balanced by the cascading quadratic nonlinearity. We also analyze the influence of phase-mismatch on the stability of dark soliton propagation.