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 Fe lix-QuinÄ onez, Ehret and Summers (Trans. ASME, J. Tribology, 2003, 125, 252±259) for a single,¯at-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¯at-top ridge due to the generation of larger pressure gradients.

A Quantitative Solution for the Full Shear-Thinning EHL Point Contact Problem Including Traction

“…In this article, the combined 2nd-order backward differential scheme is used to discretize the Couette flow on the right side of the Reynolds Eq. (20), whilst the 2nd-order central differential scheme is used to process the left side, the Poiseuille flows. At each mesh point, the values of / x , / y , and e are computed from the initial values of film thickness and pressure at current point.…”

“…The only closed form of the two-dimensional generalized Newtonian Reynolds equation was presented by Greenwood [17] for the well-known but restrictive Rabinowitsch model. Numerical simulations usually use a sinh-law for the sliding case and the Newtonian assumption for pure rolling [18][19][20][21]. As shear thinning is ignored, film thickness reduction cannot occur under the pure rolling condition in these simulations.…”

Theoretical analysis of a rolling-sliding elastohydrodynamic lubrication line contact with a subsurface inclusion

“…Unlike the effects of a surface feature, however, an important difference is observed on the film fluctuation here in that a lubricant accumulation appears to take place behind the location of the inclusion rather than in front of it, as it is found in the case of a surface ridge. 32,33 This result may be attributed to the slope of the displacements caused by the inclusion having a sign opposite to the slope of the displacements introduced by a surface ridge. As expected for pure rolling conditions where the lubricant and the bounding solids move at the same speed, both the pressure and film fluctuations appear at the same x-axis location than the inclusion.…”

Effect of changing geometrical characteristics for different shapes of a single ridge passing through elastohydrodynamic of point contacts

“…Glovnea et al (2003) and Armando et al (2003) investigated experimentally, using optical interferometry technique, the behavior of a single transverse ridge in a circular elastohydrodynamic contact. Felix-Quinonez et al (2004) investigated numerically and experimentally the behavior of passage of a single flat-top transverse ridge through an elastohydrodynamic point contact under rolling/sliding conditions. They found that the geometrical characteristics of the ridge play an important role in the formation of lubricant film thickness.…”