Analysis of EHL Circular Contact Start Up: Comparison With Experimental Results

In this paper, the start up condition in elastohydrodynamic lubrication was studied on a steel ball on glass disc contact lubricated with a mineral oil, using a previously developed mixed phase lubrication contact model. The numerical simulation demonstrated the contact geometry change in the transition from initial solid contact to final fully lubricated contact, as well as the load sharing variation between lubricated and solid contacts during the start up. The numerical results of contact geometry was then compared with an experimental study of the same start up situation published by Glovnea and Spikes [1]. The film thickness variations and the propagation of the solid-lubricated contact interface during the start up were compared. Furthermore, an analytical result of the propagation of the solid-lubricated contact interface was also generated by assuming the dominance of the wedge and squeeze terms in the Reynolds Equation, and was also compared with the numerical and experimental results. Good agreement exists among the analytical, numerical and experimental results. The good agreement proves the numerical model as a valid tool in studying the start up condition in elastohydrodynamic lubrication as the transition from solid contact to lubricated contact is of great importance when investigating the start up process and its effects on the overall lubrication performance.