Traction and Film Thickness Measurements Under Starved Elastohydrodynamic Conditions

Abstract

Traction measurements under starved elastohydrodynamic conditions have been obtained for a point contact geometry. Simultaneous measurements of the film thickness and the location of the inlet lubricant boundary were made optically. The thickness of a starved film for combination rolling and sliding conditions varies with the location of the inlet boundary in the same way found previously for pure rolling. A starved film was observed to possess greater traction than a flooded film for the same slide roll ratio. For a given slide roll ratio a starved film simply increases the shear rate in the Hertz region. The maximum shear rate depends on the degree of starvation and has no theoretical limit. The relative increase in traction due to starvation is influenced by thermal and fluid rheological conditions within the Hertz region. This makes the prediction of traction under starved conditions difficult. Traction measurements under starved conditions were compared with flooded conditions under equivalent shear rates in the Hertz region. When the shear rates in the Hertz region were low and the film severely starved, the measured tractions were found to be much lower than expected.