Research On The Effect Of Dent-Type FOD On High Cycle Fatigue Strength Of TC4 And Prediction Method

Foreign Object Damage(FOD)is a common failure or problem of fan / compressor blades used in aero-engine applications,which may result in fatigue fracture of the blade.Therefore,more complete blade design standards and service specifications for FOD are required.In this paper,a series of common dent-type FOD damage in FOD damage was studied.The effect on high cycle fatigue(HCF)of the TC4 titanium alloy blade was studied.HCF prediction method of dent-type damage blade has been developed The main research work and conclusions are as follows:(1)The macroscopic features of the dent-type damage were analyzed and a simplified geometric model of the damage was established.The degree of influence of characteristics and stress concentration factor on the strength of HCF of TC4 titanium alloy was analyzed.The results show that the macroscopic size and stress concentration factor of damage can not accurately measure the effect of damage on HCF performance of TC4 titanium alloy.(2)Based on the Bammann model,the formation process of dent-type damage was simulated.The damage of macroscopic model and geometry of simulated damage in laboratory were compared.The accuracy of the numerical simulation method was verified.Then the pit-type damage under different impact conditions The macroscopic geometric features and residual stress distribution.The results show that the Bammann model can simulate the macroscopic geometric characteristics of the pit-shaped damage accurately.The macroscopic geometric characteristics and residual stress distribution of the dent-shaped damage under different impact conditions are different.(3)Based on the critical distance theory,the HCF strength of simulated damage was predicted,and the residual stress was used to correct the prediction of HCF strength.The results were compared with those of the traditional empirical formula.The accuracy and practicability of this method.The results show that compared with the traditional empirical formula,the critical distance theory can more accurately predict the HCF strength of the dent-shaped damage blade.By considering the residual stress,the accuracy and reliability of the prediction result can be further improved.