Abnormal lubricant aggregation on roughness features in a rolling-sliding elastohydrodynamic contact

Any practical surface has some roughness which tends to decrease film thickness in concentrated contacts and increase the risk of surface failures. Surface roughness is deformed but roughness also influences the lubrication process. Therefore, it is important to understand these constrains, to predict a real performance of rough surfaces. It was already reported that roughness tends to flatten inside the contact under rolling-sliding conditions. However, this paper presents experiments showing an abnormal effect inside point contact when the additional lubricant is aggregated on the roughness feature (ridge). Enhanced roughness deformation has a protecting function against direct asperities contacts. The relationship to lubricant speed changes inside the contact, a role of thermal effect and possibility of phase transitions are discussed.