Fatigue growth rate of laser shock processed metal sheet

Compact tension(CT) specimens of superalloy with thickness of 1.5mm and a high strength steel sheet with thickness of 1.7mm are processed by laser shock,with three spots with diameter of 6mm overlapped along the extension line of precut crack.The fatigue crack growth rates of laser shock processed specimens are compared with those without LSP.The results show that effects of laser shock strengthening have much difference along the crack growth line,the fatigure growth rates can not be fitted by the Paris formula,but laser shock processing can decrease the fatigue crack growth rate in whole distincctly.