Effects of Cycle Frequency on Fretting Fatigue Life of Carbon Steel

抄録

The bending and twisting fretting fatigue tests of carbon steels are carried out and the effects of cycle frequency are studied in comparison with the corrosion fatigue. The behaviors of the frictional force with progress of fretting cycles are observed. The results obtained are as follows : The fretting fatigue strength is decreased with lower frequency. The fretting damage is saturated in the early period of the total fatigue life, and the subsequent crack propagation period constitutes the most part of the life. The lower the frequency is, the shorter the saturation period. The frictional force increases initially and then decreases after showing a peak value. These changes at various frequencies well correspond to the extents of the fretting damage. Consequently, this shows that the fretting damage is attributed to cracks initiated under the frictional stresses at the initial stage simultaneously applied with the repeated stresses in the surface layers. The fretting corrosion without the repeated stresses hardly reduces the fatigue strength though the depth of wear scars is the same as that under fretting fatigue. The greater reduction of the fatigue strength by fretting under bending than under twisting may be also explained with the combined stresses.