变参数激光冲击TC17钛合金疲劳裂纹扩展特性

Fatigue crack propagation property of TC17 titanium alloy by laser shock peening

研究采用两种不同变能量参数激光冲击TC17钛合金,通过疲劳试验分析变能量参数激光冲击对其疲劳裂纹扩展寿命和扩展速率的影响规律,通过X射线残余应力测试仪分析激光冲击后试件表面残余应力分布状态。结果表明:相比于未强化试件,在高数值残余压应力作用下的强化后试件疲劳寿命分别提高了2.14倍和1.74倍,稳定扩展初期疲劳裂纹扩展速率分别降低了21%和16%;在裂纹稳定扩展前期区域,LP-1试件扩展速率发生明显减小的现象,C'值最大,m值为最小,减为负数;LP-2试件C'值增大,m值减小。残余应力场分布是疲劳裂纹扩展的主要影响因素,两种强化方案对TC17钛合金疲劳裂纹扩展均产生抑制作用,激光能量越大,产生残余压应力值越大,激光冲击对裂纹扩展前期区域的强化作用大于对裂纹扩展中后期区域的强化作用。

After TC17 titanium alloy surface is processed by laser shock peening in two different changed energy parameters,the influence of changed energy parameters laser shock on fatigue life and propagation rate is analyzed by fatigue experiment,and then residual stress distribution on the surface of the specimen after laser shock is analyzed by X-ray residual stress equipment. The experimental results show that compared with untreated samples,the fatigue life of samples after laser shock peening in high numerical residual compressive stress respectively increases 2. 14 times and 1. 74 times. In the early of stable propagation,the fatigue crack propagation rate respectively decreases 21 % and16 %. In the early stage of crack propagation,the propagation rate of LP-1 sample decreases obviously,and it has the maximum C＇ value,the minimum m value; C＇ value of LP-2 sample increases and m value decreased. Residual stress distribution is the main influence factor of fatigue crack propagation. Two schemes of laser shock peening both have inhibitory effect on fatigue crack propagation of TC17 titanium alloy. The laser energy increases with the increase of the residual compressive stress. The strengthening effect of laser shock on crack propagation is stronger in the early stage than that in the later stage.