Track replenishment by lateral vibrations in grease-lubricated EHD contacts

Greases are attractive solutions to lubrication problems due to certain advantages over oils, such as easier manipulation, no need of resupply and filtering systems and lower lubricant losses. They are widely used in various machine components which work in the elastohydrodynamic lubrication regime. Many experimental studies have revealed that, in the absence of mechanisms to replenish the track grease lubricated contacts suffer of starvation which translates in poor lubrication and thin film thickness. In the present paper the lubrication performance of greases in contacts subjected to lateral oscillations is analyzed. The contact under study is formed between a flat disc and a ball. The ball is driven in an oscillatory motion in a direction transverse to the rolling direction. The thickness of the EHD film was measured with the optical interferometry technique. It has been found that, in the conditions of the tests, lateral oscillations have a beneficial effect, improving grease's lubrication performance even at large rolling speeds.