TC4钛合金激光冲击强化与喷丸强化的残余应力模拟分析

目的 通过对激光冲击强化和喷丸强化后的试样进行残余应力测试分析,得出两种工艺在残余应力形成机理、残余应力层深以及残余应力均匀性等方面的差异.方法 一方面采用有限元方法 模拟激光冲击强化及喷丸强化的过程,将材料在两种强化冲击下的响应进行对比,研究残余应力的形成过程,并对残余应力场的分布规律进行总结分析.另一方面,分别用两种强化技术处理TC4钛合金的表面,并用剥层X射线衍射实验测试材料表层的残余应力.最后将实验结果 与测试结果 进行对比,验证有限元模拟的有效性.结果 当这两种强化效果产生-500 MPa的表面平均残余应力时,激光冲击强化后的TC4钛合金表层残余压应力层深度可达0.6 mm以上,而喷丸强化后的TC4钛合金表层残余压应力层深度只有0.15 mm左右.结论 由于诱发材料塑性变形的机制不同,激光冲击强化往往能获得比喷丸强化更好的残余压应力深度,同时激光冲击强化的材料的表面残余应力分布也比喷丸强化的材料更均匀.

Simulation Analysis of the Residual Stress Field of TC4 Ti Alloy under Laser Shock Peening and Shot Peening

Objective By measure of the residual stress of Laser shock peening (LSP) and shot peening (SP) tests, the differences between LSP and SP in formation mechanism, depth layer and uniformity of residual stress were found out. Methods On one hand, finite element method (FEM) was used to simulate the process of LSP and SP. The mechanical behaviors of TC4 under LSP and SP were compared. In addition, the formulation of residual stress was studied and the law of the residual stress was summarized. On the other hand, the residual stress of TC4 which had been treated with SP and LSP was measured using the 2-D X-ray method. Eventually, the result of experiment was compared with the result of simulation, and the effectiveness of FEM simulation was confirmed. Results The results showed that when both methods caused -500 MPa residual stress on the surface of TC4, the depth of compressed residual stress caused by LSP could reach 0. 6 mm, while the depth of compressed residual stress caused by SP was only 0. 15 mm. Conclusion Because the mechanism of causing plastic deformation was different, LSP could cause deeper compressed residual stress. Meanwhile, the distribution of residual stress caused by LSP was more uniform than that caused by SP when the fraction of coverage was 100% .