Regulation of lubricant supply by wettability gradient in rolling EHL contacts

Starvation often occurs in elastohydrodynamic lubricated (EHL) contacts due to limited lubricant replenishment at high speeds or restricted fresh oil charging. This work presents several conceptual studies for regulating lubricant replenishment/supply by means of wettability gradient, which is generated by an oleophilic track bounded by two oleophobic zones on solid surface. It was demonstrated that when the EHL contact was within the central oleophilic track, the wettability gradient on the two sides could drive the lubricant to form a stable oil reservoir leading to thick EHL films. Nevertheless, if there was a single step wettability gradient, the lubricant could be driven away easily from the lubrication track, leading to starvation despite a large amount of lubricant provided.