Effect of oil starvation on the surface dimple in elastohydrodynamic lubrication contact under opposite sliding conditions

Optical interferometry experiments were performed to investigate the dimple phenomena in starved elastohydrodynamic lubrication of point contacts under opposite sliding condition by using a high viscosity polybutene (PB) lubricant. The effects of the bilateral starvation, left starvation, and right starvation on the variation of the oil film under a high slide-to-roll ratio were investigated. It was found that oil starvation could generate a starved constriction, which would make the shape of the oil film resemble the one in pure-rolling or rolling-sliding contact. However, the film thickness at the starved constriction is much lower. In addition, the influence of the applied load on the variation of the surface dimple in fully flooded and starved conditions was explored. It was found that the effect of oil starvation depended on the way the net mass flow through the contact zone. When the net mass flow was from left to right, a major constriction was formed on the right side, and vice versa. When symmetrically increasing the degree of oil starvation, the classical big dimple shrunk and became centralized before eventually disappearing and the contact approximated the nominally flat state of a heavily starved or almost dry contact.