Effect of Variable Stress Amplitude on Fretting Fatigue Crack Initiation at Press-Fitted Axle Assembly/Effects of Stress Cycle Ratio, Number of Load Levels and Axle Size

摘要

The objective of the present paper is to evaluate the effect of variable stress amplitude, particularly those of the stress cycle ratio, number of load levels and axle size on the fretting fatigue crack initiation at press-fitted axle assembly. The rotational bending fatigue tests with two-level, three-level and ten-level loadings were conducted on the induction hardened press-fitted axles of 40mm in diameter.It was found that the modified Miner's damage (D) under the two-level variable load decreases as the stress ratio increases, but D becomes constant when higher, lower and equivalent stress levels are the same respectively. For the size effect, D of 40mm diameter axle is less than 1.0, whereas D of full-scale axle is larger than 1.0. This size effect is caused by the fact that the locations of maximum stress, where cracks initiate, for respective load levels do not coincide in the full-scale axle.