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为研究激光冲击7050铝合金薄板试样形成残余应力洞的机制,分别使用功率密度为1.98 GW/cm~2和2.77GW/cm~2的激光冲击7050铝合金试样。采用ANSYS/LS-DYNA有限元分析软件模拟分析了在功率密度为1.98GW/cm~2的激光束冲击下的薄板试样。实验中利用X射线应力分析仪测量薄板试样和厚板试样的残余应力分布,利用压电薄膜传感器测量激光冲击时试样的动态应变,并利用三维显微系统观察激光冲击区域的表面微结构。实验结果表明,功率密度为1.98GW/cm~2和2.77GW/cm~2的激光束冲击7050铝合金薄板试样后均产生了残余应力洞现象。反射边界条件下的模拟结果与实验数据具有较好的一致性,表明稀疏波在光斑中心的会聚是产生残余应力洞现象的主要原因。由残余应力分布和动态应变可知,在试样内来回反射的冲击波对残余应力洞的影响不容忽视;功率密度为2.77GW/cm~2的激光束冲击加载后,薄板、厚板试样冲击区域中心的厚度分别比临近区域的厚度大10.800μm和8.150μm;在表面稀疏波与冲击波的共同作用下,试样表面均产生了残余应力洞现象。
In order to study the mechanism of laser induced residual stress in 7050 aluminum alloy thin plate, 7050 aluminum alloy was impacted by laser with power density of 1.98 GW / cm ~ 2 and 2.77GW / cm ~ 2, respectively. ANSYS / LS-DYNA finite element analysis software was used to simulate the thin plate specimen under laser beam impact with a power density of 1.98GW / cm ~ 2. In the experiment, the X-ray stress analyzer was used to measure the residual stress distribution of the thin plate specimen and the thick plate specimen. The piezoelectric thin film sensor was used to measure the dynamic strain of the specimen during the laser shock. The surface micro- structure. The experimental results show that the laser induced laser beam with power density of 1.98GW / cm ~ 2 and 2.77GW / cm ~ 2 impact the residual stress cavity in 7050 aluminum alloy thin plate. The simulation results under the reflection boundary conditions are in good agreement with the experimental data, indicating that the convergence of the sparse wave in the center of the spot is the main reason for the residual stress cave phenomenon. From the residual stress distribution and dynamic strain, we can see that the influence of the shock wave reflected back and forth within the sample on the residual stress can not be ignored. After the impact of laser beam with power density of 2.77GW / cm ~ 2, The thickness of the center is 10.800μm and 8.150μm thicker than the adjacent area, respectively. Under the combined effect of the surface sparse wave and the shock wave, residual stress caves are formed on the specimen surface.