Oil Film Characterization of PTFE During EHL Point Contact and Pure Rolling Tribology Tests

A polymer additive blended with commercial engine oil to have enhanced film-forming ability has been developed and studied using optical interferometry. An experimental study was carried out on the impact of polymer additives (Polytetrafluoroethylene – PTFE) in an oil film between a steel ball and a flat glass surface in non-conformal contact. The contact region was studied by means of optical interferometry using monochromatic two-beam interferometry, a microscope and a high-speed video recording device. A new method of determining the interference grade of the central film thickness was developed and used in this study. The interference intensities of the central point of contact at various speeds were captured by the high-speed video recording device and the central interference gray values were determined. These values were then used in new method to obtain the film thickness of the modeled lubricants, and compared with the rectangular SLIM fit and the LINE fit methods film thickness determination. Hamrock and Dawson calculations for EHL film thickness formation was also used for comparative analysis. The film thickness stability was simulated under both steady state and rolling state conditions. The lubricant film thickness stability obtained confirmed the beneficial effect of PTFE on film thickness behavior under pure rolling conditions. The regime observed by the profile of the film thickness suggest the transition between the hydrodynamics and elastohydrodynamic lubrication.