Study on residual stress distribution of laser shock forming metal-sheet

In order to study the effect of residual stress on the laser shock forming metal sheet,a high power Nd:glass laser was used to form the metal-sheet and then the residual stress distribution on the surface of metal sheet was tested by means of Xray diffraction method.It was found that there was large residual compress stress on the concave surface of metal-sheet,but low residual tensile stress on the fringe of convex surface.The residual stress increased with the increase of laser energy.When the laser energy came to a certain value,the residual compress stress reached its maximization.On the shock surface,the residual compress stress of shock point was maximal,the other compress stress decreased in a nonlinear way along the shock point and ultimately to zero.For laser shocking different aperture of mold with a laser beam in 8mm diameter,30J energy,there was a threshold for the aperture of the mould.The residual stress increased with the increase of aperture when the aperture was smaller than the threshold.However,it decreased with the increase of aperture when the aperture was larger than the threshold.The threshold aperture was about 20mm.The results are very important for study of the distribution and control of residual compress stress,play an important theoretical and engineering role in studying the material fatigue,stress corrosion resistance and capability of the surface.