Research On Effect Of Friction State On Fretting Fatigue Life Of Connecting Structure

Fretting fatigue is a kind of typical failure mode of the connecting component, and it is of great significance to improve its anti fretting fatigue properties. The present study focuses on the effect of the residual stress of surface treatment on the fretting fatigue life, but the effect of friction state change on fretting fatigue life is neglected. The experimental results show that the friction state of the fretting fatigue process can be changed with the number of fatigue load cycles. Therefore, the study on the effect of friction state change on fretting fatigue life is significant.The main content of this thesis includes the following several aspects:Firstly, a new method for predicting the fretting fatigue life is presented, in which, the variation of the friction coefficient is taken into account by using the progressive accumulated damage method.By using this method, the fretting fatigue life of the smooth specimen was predicted, and the results were within 2 times of the test error. Compared with the LAM model, the prediction accuracy is improved by 23%, which regarded the friction coefficient as const 0.5.Secondly, a test device with the aid of the strain gauge monitoring the fretting friction state in the process of fretting fatigue was developed. The test device was calibrated and the 45#/45# steel specimens were used to demonstrate the fretting fatigue test. The results show that the working section of the test device has a good linear relationship with the load. The test results are typical fretting fatigue failure and the development of the test device can carry out the fretting fatigue test.Finally, the fretting fatigue friction state monitoring test of 2 kinds of load conditions(A, B) was carried out for the TC11 titanium alloy. The results show that the friction coefficient showed a steady trend after its increase in the whole fretting fatigue process. The steady friction coefficient was 0.375 under condition A, and the friction coefficient was 0.62 under condition B. The change of friction coefficient was 1/4~1/3 of the total fretting fatigue life.Not much difference between the fretting fatigue life of condition A and B.