The effect of surface roughness on friction and film thickness in transition from EHL to mixed lubrication.

The purpose of this study is to reveal the connection between the film thickness and the friction for a uniform surface texture on transition from full film to mixed lubrication in non-conformal contacts. The current study tries to clarify the processes leading to the friction increase during the transition that is usually seen in the Stribeck curve. The transition to mixed lubrication and the friction increase are usually associated with a direct contact between surface irregularities. However, the experimental results showed that friction increases much earlier before the first contact was detected. It was revealed that a standard mixed friction modeling based on the area in a direct contact has significant limitations. Numerous possible explanations for this phenomenon are discussed. [ABSTRACT FROM AUTHOR]