Frictional behaviour and friction mechanisms of rolling-sliding contact in mixed EHL

•A mixed EHL friction prediction model is presented.•Solid-to-solid interaction dominates the friction in boundary lubrication.•Contact ratio dominates the frictional behaviour in mixed EHL.•Boundary film friction has a limited influence on overall frictional behaviour.

Frictional behaviour of mixed Elasto-hydrodynamic lubrication (EHL) arises from the coupling of the lubricant fluid and asperity interaction frictions. Due to the difficulties in modelling asperity interaction friction, existing approaches often use a constant friction coefficient obtained in boundary lubrication to approach the asperity interaction friction coefficient in mixed EHL. In this study, the asperity interaction friction is, for the first time, considered to result from either the boundary film friction or solid-to-solid ploughing and adhesion friction depending on the local contact and deformation conditions. The friction of mixed EHL was predicted by the combination result of lubricants fluid, boundary film, and solid-to-solid frictions. This development provides an alternative and cost effective method to estimate friction coefficient in mixed EHL.