激光冲击强化“残余应力洞”的形成机制

利用ABAQUS有限元软件进行了单个圆形高斯光斑的激光冲击强化数值模拟,分析材料表面光斑中心区域形成的"残余应力洞"现象,并通过分析材料的动态力学响应特征揭示了"残余应力洞"的形成机制。结果表明:在冲击波加载时,光斑边界处会产生很强的剪切应力,形成向四周传播的表面稀疏波和向材料内部传播的剪切波。当稀疏波同时传播到光斑中心,发生相遇、汇聚,使材料产生急剧的上下位移过程,造成冲击波加载塑性变形后的二次塑性变形。二次塑性变形中形成了较大的剪切塑性应变,并降低了冲击波加载阶段产生的轴向和径向塑性应变,使残余压应力降低,从而形成"残余应力洞"。

Formation mechanism of "residual stress hole" induced by laser shock peening

Simulation of laser shock peening with one round gauss-spot was carried out by ABAQUS FEM software. A residual stress hole phenomena in the material surface was detected. The formation mechanism of residual stress hole was explained via analyzing the dynamic mechanics response of the material in the spot center. The results indicate that intense shear stress is generated during the loading of laser-induced shock wave, and rarefaction wave and shear wave are formed. Rarefaction wave spreads all around in the material surface and shear wave propagates inward. When the ambient rarefaction waves meet and converge in the spot center, the material rises and falls sharply and secondary plastic deformation is generated. Because of the secondary plastic deformation, a large shear plastic stain is formed and the axial and radial plastic strain which were formed under the laser-induced shock wave, are greatly reduced. After the secondary plastic deformation, the residual stress reducing in the spot center results in the residual stress hole.