An Investigation of Friction Force in Fretting Fatigue

Fretting fatigue limit of mechanical joints is effected by various parameters but most important of them are friction force, relative slip, and clamping pressure which appear in the area of contacting surfaces. Unfortunately these three parameters are mutually influencing each other and their individual effect is not easy to be established. In this paper a stress model of fretting fatigue is presented according to which the fretting fatigue limit depends only on the stress distribution around the fatigue cracks developing in fretting fatigue process. That hypothesis has been proved by investigations carried out on carbon steel in ambient conditions and in an oxygen-free environment. For the last research, a special chamber has been designed and built in which the fretting junction has been investigated in an argon environment. The friction force and the relative slip between the specimen and the fretting pads have been measured by means of strain gauges. The results of the investigation are in good agreement with the theoretical formula developed by the author in previous works and prove predominant influence of friction force on the fretting fatigue limit of a mechanical joint.