应力水平下的激光冲击小孔构件疲劳扩展研究

Research on fatigue growth of laser peening hole specimen under stress level

激光冲击强化可以降低小孔构件裂纹扩展速率,提高疲劳寿命。疲劳扩展是疲劳寿命的主要组成部分,不同的应力水平会影响疲劳扩展,其对未强化试样和强化试样的影响是不同的。为此通过激光冲击强化TC4-DT钛合金双联小孔试样,然后进行疲劳试验,研究应力水平下的激光冲击小孔构件疲劳扩展。研究结果表明:应力水平提高会导致疲劳条带宽度增大,同时强化端同比增大尺寸大于未强化端,未强化端(I_0)和强化端疲劳条带宽度(I_1)差值(I_0-I_1)与未冲击端疲劳条带宽度(I_0)的比值也有降低的趋势。因此,增大应力水平会增大疲劳条带宽度,应力水平的变化对激光冲击强化后试样的疲劳扩展影响更大,应力水平增大降低激光冲击强化疲劳寿命增益;在激光冲击强化参数一定时,应该规定适用的应力水平范围。

Laser peening can improve the fatigue life of the pore structure effectively,while fatigue growth is the main part of the fatigue life. Different stress levels affect the fatigue growth,so the effects of no shocked sample and shocked sample are different. Laser peening experiments are used to analyze fatigue growth of TC4-DT titanium alloy hole specimen under stress level. Results show that the increase of stress levels will lead to the increase of fatigue striation width. The change of stress level has greater effect on fatigue growth of specimens after laser peening,but the increase of stress level will reduce the gain of laser peening fatigue life. The applicable stress level should be controlled when laser shock processing parameters are constant.