Effects of surface topography on lubrication film formation within elastohydrodynamic and mixed lubricated non-conformal contacts

This article focuses on the effects of surface topography modifications on lubrication film thickness within non-conformal lubricated contact. An optical test rig is used to study lubricant film behaviour between the flat surface of a chromium-coated glass disc and a steel ball. An array of micro-dents was produced on the ball surface to be able to demonstrate the effect of surface topography on lubrication film formation. Experiments were carried out under elastohydrodynamic and mixed lubrication using steady-state and transient operational conditions (start-up and reversal motion). The obtained results showed that surface texturing could represent a method of increasing the lubrication efficiency of rolling/sliding non-conformal contacts under operational conditions when the lubrication film is not able to separate rubbing surfaces. Lubricant emitted from the micro-dent helps in reducing asperities interaction. Moreover, the effect of surface micro-cavities has been observed within starved non-conformal contact under pure rolling conditions. An increase in film thickness within severe starved contact was localized upstream of the micro-dents, and was recently predicted numerically. This effect was further amplified as lubricant released from micro-dents remains on the ball surface and again enters into contact after the ball turns round.