Fretting Fatigue Strength under High Local Contact Pressure and Its Fracture Mechanics Analysis
Kunio ASAI
Abstract:Fretting fatigue fractures of industrial machines often occur at the point where high contact pressure occurs due to an uneven contact. In this study, fretting fatigue tests were performed under high contact pressure applied by line-contact conditions using 12-Cr steel with parameters of the mean stress and the material strength. It was shown that the fretting fatigue strength decreased slightly with increasing the contact pressure and became minimum when Hertz's average contact pressure is about 1.5 times of 0.2 % proof stress, ƒÐ0.2. I also showed that test results concerning the fretting fatigue strength and the non-propagating crack length can be successfully explained by the micro-crack propagation model in which a micro-crack can propagate when its stress intensity factor range, ƒ¢K is greater than the threshold value, ƒ¢Kth considering small crack size effects and mean stress effects. Key Words:Fretting fatigue, Fracture mechanics, Small crack, Crack propagation, Mean stress