Numerical analysis of experimental observations of a single transverse ridge passing through an elastohydrodynamic lubrication point contact under rolling/sliding conditions

Abstract

Recent experimental observations by Félix-Quiñonez, Ehret and Summers ( Trans. ASME, J. Tribology, 2003, 125, 252–259) for a single, flat-top transverse ridge passing through an elastohydrodynamic lubrication (EHL) point contact under various slide-roll ratios have revealed some unexpected features. In particular, under sliding conditions the ridge was observed to sustain additional deformations in the high-pressure region of the contact and an entrapped amount of lubricant was seen to accompany the ridge during its passage through the conjunction and, contrary to current knowledge, appeared not to move at the entraining velocity. This paper analyses the experimental observations by means of a direct comparison with numerical simulations. The numerical results show that the main contributing factor towards the experimentally observed accumulation of lubricant is a reduced lubricant viscosity via shear thinning effects. For the operating conditions considered in this study, internal heating of the lubricant is found to be negligible. In addition, it is shown that the amount of lubricant accumulation is dependent on the geometry of the ridge. Compared to a defect with a Gaussian shape, it is further shown that a greater accumulation of lubricant occurs with the flat-top ridge due to the generation of larger pressure gradients.