Fretting Fatigue Life Model And Experiments Of TC11 Alloy At Different Temperatures

Fretting fatigue is a common phenomenon in aviation field.Compared with normal fatigue,it can significantly reduce the life of components.Since the temperature of compressor varies greatly from low-pressure section to high-pressure section,it is very important to study fretting fatigue behavior of titanium alloy components at different temperatures in order to ensure engine safety.Therefore,the fretting fatigue tests at different temperatures are carried out,and the model of fretting fatigue life prediction considering temperature is established.The main research work and conclusions are as follows:Firstly,a fretting fatigue test device for high temperature is designed.The device adopts transverse loading of stress ring,heating of high temperature barrel resistance furnace and combined cooling of water cooling and air cooling.The test device has the following advantages: the convex platform and trapezoidal thread of the stress ring can play a good role in preventing loosening,the stress ring can meet the transverse loading requirement of high temperature fretting fatigue test by strength check.The alignment holding and stiffness strengthening device can solve the problems of alignment inaccuracy and clamping stiffness decline caused by single clamp head fretting pad to the stress ring device.The temperature of high temperature barrel resistance furnace can be controlled by temperature controller to ensure the stability of heating temperature.Secondly,fretting fatigue tests were carried out with titanium alloy TC11 as fretting fatigue test material at different temperatures.It was found that the fretting fatigue crack initiation period accounted for the vast majority of the total life.Fretting fatigue crack initiation occurred at the lower edge of the contact area between the fretting pad and the test specimens.The wear of the test specimens increased significantly with the increase of temperature.There are obvious fretting blackspots on the contact surface.The test results show that fretting fatigue life of TC11 specimen decreases with the increase of temperature and normal load,and both temperature and normal load have great influence on fretting fatigue life.Finally,based on continuum damage mechanics,a fretting fatigue life prediction model considering temperature is established to analyze fretting fatigue life at different temperatures.Based on the existing fretting fatigue life prediction model based on non-linear fatigue damage accumulation theory,temperature-dependent damage rate factor is introduced to consider the effect of temperature on fretting fatigue behavior of structures.The finite element model of the contact between test piece and flat indenter with circular arc section is established.The parameters of material-related life prediction model are fitted by single-clamp fretting fatigue test results to establish the full fretting fatigue life prediction model,and the numerical simulation of fretting fatigue life at different temperatures was carried out.The fretting fatigue test life of a titanium alloy TC11 dovetail structure simulator was used to verify the validity of the model.The results show that the comparison of predicted life and test life is within 2 times error band,and the predicted location of crack initiation coincides with the location of crack initiation in the test,which verifies the effectiveness of the life prediction model.