Relationship between the molecular structure of lubricants and appearance of anomalous film shapes in elastohydrodynamic lubrication conditions

This study investigates the relationship between the molecular structure of lubricants and the appearance of anomalous film shapes in elastohydrodynamic lubrication conditions. A ball-on-disc type test rig was used, which produced a point contact area between a rotating glass disc and rotating steel ball. Several pure liquids such as alkanes, alcohols, and others with a single polar site were used as lubricants. Linear chain lubricants caused solid-like behaviour in the film formation, traction coefficient and flow out time of entrapped lubricant in shock loading tests whereas complexly shaped lubricants caused liquid-like behaviour. The clear dependence on lubricant type appears to indicate that the anomalous film shapes formed due to the solidification of the lubricant.