Fundamental Investigations of Fretting Fatigue : Part 2, Fretting Fatigue Testing Machine and Some Test Results

Abstract

In the present paper, the construction and features of a fretting fatigue testing machine designed by the authors are explained, and the experimental results obtained by using the testing machine are stated concerning mainly the relative slip which is considered to be one of the most significant factors affecting the fretting fatigue strength. The following are known from this investigation. In fretting fatigue, many shallow micro-cracks which seem not to propagate to a complete fracture are formed and develop somewhat obliquely from the surface of specimen because of the effect of frictional force due to fretting. Fatigue strength is reduced significantly by the effect of fretting, and the strength reduction factors, concerning both nucleation of fatigue cracks and fatigue fracture, are greatly influenced by the magnitudes of relative slips. The fatigue strength is most significantly reduced when the relative slips are about 0.015〜0.020 mm, and reduced to less than 1/5 of its strength without fretting, and if the relative slips could be kept less than 0.005 mm, a marked improvement would be expected.