TC4钛合金外物损伤疲劳极限及预测研究

Fatigue Limit and Predication of Foreign Object Damage of TC4 Titanium Alloy

关键词:  航空发动机  外物损伤  模拟叶片  高周疲劳极限  有限元仿真  残余应力  预测

Key words:  Aircraft engine  Foreign object damage  Simulated blades  High cycle fatigue limit  Finite element simulation  Residual stress  Prediction

摘要:

为研究外物损伤对航空发动机TC4叶片高周疲劳极限的影响，以模拟叶片为研究对象，采用空气炮法，预制不同工况下钢球冲击模拟叶片前缘外物损伤，为获得损伤叶片的疲劳极限，对损伤叶片开展了高周疲劳试验，在此基础上，通过有限元仿真探究了缺口残余应力分布对疲劳裂纹的萌生以及疲劳极限的影响，最后通过修正Peterson公式对叶片疲劳极限进行预测研究。结果表明，冲击所造成的缺口尺寸随冲击能量的增大而增大；叶片的高周疲劳极限随冲击能量增大而降低，其中缺口深度对疲劳极限的影响较大；缺口底部残余拉应力可能对叶片疲劳极限有一定影响；Peterson公式对疲劳极限进行预测所得结果误差较大，修正后预测结果误差从-30%~30%降至-15%~15%。

Abstract:

In order to study the effects of foreign object damage （FOD） on the high-cycle fatigue limit of aero-engine TC4 blade， the simulated blade was taken as the research object. The air gun method was used to simulate the foreign object damage of the leading edge of the blade under the impact of prefabricated steel balls under different working conditions. In order to obtain the fatigue limit of the damaged blades， the high-cycle fatigue test was carried out on the damaged blades. On this basis， the effects of notch residual stress distribution on the initiation of fatigue cracks and the fatigue limit were explored by finite element simulation. Finally， the fatigue limit of the blade was predicted by modifying the Peterson formula. The results show that the notch size caused by impact increases with the increase of impact energy. The high-cycle fatigue limit of the blades decrease with the increase of impact energy， and the notch depth has a great influence on the fatigue limit. The residual tensile stress at the bottom of notch may have some effect on the fatigue limit of blade. The error of Peterson formula in predicting the fatigue limit is large， and the error of prediction result after correction decreases from -30%~30% to -15%~15%.