Fretting fatigue in S 45 C steel under two-step block loading.

Abstract

The fretting fatigue strength of low strength medium carbon steel (S 45 C) under two-step block loading was examined by clamping the contact pads of the same material. The linear cumulative damage rule did not always hold good for fretting fatigue under two-step block loading, while it held good for plain fatigue. When the number of cycles in the block was large enough and the number of blocks to failure was smaller than 5 or 6, the two-step block loading reduced the fretting fatigue strength by a factor of five or ten. The coefficient of the friction and the slip amplitude reached constant values within a few hundred cycles after changing the stress level. Prediction of fatigue life was made on the basis of the analysis in the previous paper, where the frictional force between the fretting pad and the specimen was taken into consideration. The predicted lives were in good agreement with the experimental results.