Study on residual stress distribution of laser shock forming metal-sheet
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摘要: 为了研究激光冲击成形后残余应力对板料性能的影响,采用高功率Nd:glass激光器对金属薄板激光冲击成形,使用X射线衍射法对激光冲击成形后的金属薄板的表面残余应力分布分析研究。薄板成形后的凹面分布存在较大的残余压应力,而凸面边缘存在较小的残余拉应力;残余应力随着激光能量的增加而增加,但当到达一定值时,凹面残余压应力达到最大值;在冲击凹面中心点处的残余应力值最大,周围处的残余应力以中心点为圆心向外呈非线性递减。在不同的凹模孔径下采用8mm光斑、30J激光能量单次冲击,发现存在一个凹模孔径阈值,小于阈值时,残余应力随着孔径的增大而增大;大于阈值时,随着孔径的增大而减小,阈值大小大约为20mm。结果表明,该研究对进一步研究残余应力的控制有重要作用,且对材料的抗疲劳性能、抗应力腐蚀、表面性能研究有很重要的理论和工程价值。Abstract: 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.
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