激光冲击TC17钛合金疲劳裂纹扩展试验

为研究激光冲击强化对钛合金试件疲劳性能的影响,在标准试件的裂纹扩展路径上设计了全强化和间隔强化两种不同的强化方案,研究激光冲击强化对试件疲劳寿命和裂纹稳定扩展时速率的影响规律,利用有限元数值模拟和X射线残余应力测试获得了试件的残余应力场分布状态,并对比分析了试件的断口形貌和微观组织特征。结果表明:相比于未强化试件,激光冲击强化后试件的平均疲劳寿命分别提高了2.14倍和1.90倍,两种不同的冲击强化方法分别降低钛合金试件的裂纹扩展速率24%和15%。间隔强化后试件表面产生-512 MPa的最大残余压应力,裂纹扩展的C′值为-7.3,m值为2.6,而强化间隔区引入最大值为82.4 MPa的残余拉应力,裂纹扩展速率急剧升高,C′值减小至-13.6,m值为8.0。当裂纹扩展到强化区时,扩展速率再次降低,激光冲击强化对TC17钛合金疲劳裂纹扩展有显著的抑制作用。

Fatigue Crack Growth Behavior of TC17 Titanium Alloy with Laser Shock Peening

To study the effect of laser shock peening on the fatigue performance of the titanium alloy, the laser shock peening with full strengthened and spacing strengthed, two different area on fatigue crack behavior of TC17 titanium alloy was analyzed about the rules of crack propagation rate and the fatigue life. The residual stress field distribution of the specimens was tested using finite element numerical simulation and X-ray residual stress testing. Fracture morphology and microstructure of the specimens were comparatively analyzed. Results show that the fatigue life of samples after laser shock peening increases 2.14 times and 1.90 times compared with untreated samples, and the crack propagation rates decreases by 24% and 15%. The residual stress of the spacing strengthed specimen surface is 512 MPa after laser shock peening. The value of crack propagation is -7.3 and the m value is 2.6. The maximum residual tensile stress introduced in the strengthened spacer region is 82.4 MPa and the crack propagation rate sharply increases with value reducing to -13.6 and m value to 8.0. When the crack propagates to the strengthening region, the propagation rate decreases again. Laser shock peening significantly restrains the fatigue crack propagation of TC17 titanium alloy.