Wear of cam mechanisms and elastohydrodynamic lubrication

Life prediction for dynamic systems is very important for machine designers in terms of technical and economical reasons. Wear of co-working surfaces is a critical factor affecting the life of the product. Although wear is definitely an ordinary event, the mechanism and theory of wear are very complex phenomenon of the system which includes material properties, operating conditions (load, speed, etc.), contact geometry, surface roughness, and environment (lubrication, temperature, etc.). However, it is not possible to deal with so many components on a mathematical model. The modelling studies which involves the wear arised surface of the cam by considering only spring forces effects are present in the literature.In this study, the mathematical model has been formed by considering inertia forces arising from the spring affecting cam mechanism and acceleration of the follower.Archard's wear equation has been adapted to the current situation and a mathematical model which reveals the depth of wear depending on the force and time variable has been established in dry conditions. For the same existing conditions, experimental studies have been performed for PTFE cam profile and then wear depth of the worn cam profile have been determined by CMM for different angles. Experimental results were compared with the theoretical data that as a mathematical model put forward and was seen a reliable model.The same studies have been also applied to cam profile that made of brass by this way the reliability of the model has been presented. Then, in the case of performing the same studies for lubricated conditions, the effect of force component on the film thickness has been investigated. Film thickness relations that obtained for a variety of elastohydrodynamic regimes were examined. Instead of the assumption of constant force in this statements the film thickness has been predicted by considering variable force in this study.The approach in this thesis study enables to predict wear depth during lifetime of the cam.