激光冲击后在其金属表面形成一定形式的残余压应力,可对材料表面进行改性处理。采用ABAQUS有限元软件,研究激光功率密度、光斑形状对板料表层残余应力场分布的影响,探索残余应力场机制。结果表明,提高激光功率密度可以增加板料表层残余应力场,但随功率密度增大会产生“残余应力洞”现象;激光冲击后材料位移和表面应力动态响应分析表明,材料表面受冲击与材料弹性力作用产生振荡过程,冲击光斑边缘产生反射波(稀疏波)的反向加载,引起反向塑性变形,形成“残余应力洞”现象;光斑形状影响稀疏波向中心汇聚,造成中心残余压应力不同的缺失。该研究为工艺参数优化,减少冲击中心残余应力缺乏,获得更好的激光冲击处理强化效果提供依据。

The compressive residual stresses are generated by laser shock processing (LSP) on the metallic surface,and laser shock processing is a new surface strengthening technology which can modify material surface. With the finite element simulation software ABAQUS,the effect of the laser power densities and the spot configurations on the distribution of residual stress field of the material surface is simulated. The results indicate that the compressive residual stress field can be enhanced by increasing the laser power densities,but the “residual stress hole” may appear with the increase of the power densities. From the analysis of material displacement and the dynamic response of the surface stresses after the laser shock,it is found that the shocking on material surface and the elastic force of material together form the oscillation process,and the reflection waves (rarefaction waves) load reversely on the shocking spot edges,inducing the reverse plastic deformation,which is the so-called “residual stress hole”. The focalizing of the rarefaction waves to the center is influenced by the spot configurations,and the residual stress deletion at the shocking center is different. The results can be used to reduce the residual stress deletion at the shocking center and optimize the process parameters,which provide a basis for obtaining the better strengthened effect of the laser shock processing.