Film thickness interrelationship of base oil and grease lubricated compliant and hard non-conformal contacts

Abstract

The interfaces of plastic components are often operated as self-lubricating or lubricated with greases close to the piezoviscous-elastic lubrication regime. However, current basic tribological knowledge about grease-lubricated compliant contacts is still very limited. This experimental study provides insight into relations between film thicknesses of grease and its base oil in compliant polymethylmethacrylate–steel and stiff glass–steel point contacts at different speeds and loads. The results are compared with predictions. The ratio between grease and its base oil film thickness was found to be significantly influenced by the interplay of load and the non-Newtonian response of grease, especially for the compliant contact, while the effect of speed and the slide-to-roll ratio was considerably lower. The role of viscoelasticity and grease thickener concentration is discussed.