Fretting fatigue in JIS S45C steel under two-step block loading.

Abstract

The fretting fatigue strength of a low strength medium carbon steel (JIS S45C) under two-step block loading was examined by using contact pads of the same material. The linear cumulative damage rule did not always hold for fretting fatigue under two-step block loading, while it held for plain fatigue. when the number of cycles in the block were large enough and the number of blocks to failure were smaller than 5 or 6, tow-step block loading reduced the fretting fatigue life by a factor of five to ten. The coefficient of friction and the relative 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 proposed in a 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.