逐层剥离对激光诱导残余应力场影响的数值模拟

Numerical simulation of the effect of layer stripping on the laser-induced residual stress field

为评价激光冲击强化效果,通常采用X射线衍射法(XRD)测定工件的残余应力分布。由于X射线穿透深度一般在微米数量级,为获得工件深度方向上的残余应力分布规律,常采用电解抛光的方法逐层剥离工件表面材料。逐层剥离过程改变了工件表面的边界条件,使得残余应力分布发生了改变,导致XRD实验测得的残余应力与未剥离前不同。本文采用有限元数值模拟方法研究了剥离过程对激光诱导残余应力场分布的影响。结果表明:在残余压应力区域,剥离材料后内部的残余压应力较剥离前增大,残余压应力增加程度随着剥离深度的增大而增加;剥离表面较浅一层材料时,整体残余应力场的分布变化较小,且有利于消除激光冲击强化产生的"残余应力洞"。该研究对基于XRD实验测定的残余应力修正具有一定的指导意义。

In order to evaluate the effect of laser shock peening,the residual stress distribution of workpieces is usuallymeasured by the X -ray diffraction method（XRD）.Since the penetration depth of X -ray is in the range of microme-ter,in order to obtain the distribution of residual stress in depth,the surface materials are often stripped layer by layerby the electrolytic polishing method.Layer -stripping process changes the boundary conditions of workpiece surface,so the distribution of residual stress is changed.The residual stress value obtained by the XRD experiment is not thesame as that without layer -stripping.In this paper,finite element numerical simulation method is adopted to study theeffect of layer -stripping process on the distribution of residual stress induced by laser.The result shows that：in thecompressive residual stress region,the compressive residual stress value after stripping is greater than that withoutstripping,and compressive residual stress of the material increases with the stripping depth increases;there will be lit-tle influence on the residual stress distribution if the stripped layer is shallow.It will be conducive to the elimination ofthe ＆quot;residual stress hole＆quot;by laser shock peening.This research has theoretical significance to the correction of residu-al stress based on the XRD experiment.