Research On Fatigue Prediction For Fan Blade Following Foreign Object Damage

Foreign Object Damage(FOD)is a common problem that can not be avoided in the process of aeroengine.It easily leads to fatigue fracture of the blade and has a significant impact on the safety and economy of the engine.In this paper,the fatigue performance prediction and evaluation of titanium alloy fan blades following FOD were studied.The main work and conclusions are as follows:(1)The research status of FOD at home and abroad were reviewed.Review shows that: the development of accurate prediction on material fatigue property following FOD is great engineering value for the aviation industry.Theoretical analysis and predictions for FOD fatigue problems need to be studied and discussed in future,which is lack in the country.(2)Based on the critical distance theory,the fatigue strength prediction of FOD notch was analyzed,the results show that: The prediction of fatigue strength based on FOD macroscopic size has a great error with the actual test value,the overall level of prediction is high and the results are relatively scattered.The main reason for the error is that it does not consider the contour of FOD and the micro-damage caused by impact.There are some irregular defects and pits in the bottom region of FOD through structured light scanning,and the distribution of defects and pits is relatively concentrated.The superimposed notch model is proposed to characterize contour characteristics of the FOD based on the observation results.Based on the superposition notch model and the critical distance theory,the fatigue strength of FOD notch can be predicted more accurately,and the relative error is basically in plus or minus 30%.(3)Based on the weakest link theory,the fatigue life prediction of FOD notch was analyzed,the results show that: There is a large difference between actual life and predicted life by the FOD macroscopic notch,and the overall level of predicted life expectancy is relatively high.The prediction accuracy of fatigue life is improved to some extent by using the superimposed notch model,and most of the predicted life is distributed within 5 times dispersion band of the actual life.