A mixed elastohydrodynamic lubrication model with asperity contact

Most machine elements, such as gears and bearings, are operated in the mixe d lubrication region. To evaluate lubrication performance for these tribolo gical components, a contact model in mixed elastohydrodynamic lubrication i s presented. This model deals with the EHL problem in the very thin film re gion where the film is not thick enough to separate the asperity contact of rough surface. The macro contact area is then divided into the lubricated area and the micro asperity contact areas by the contacted rough surfaces. In the case when asperity to asperity contact is present, Reynolds equation is only valid in the lubricated areas. Asperity contact pressure is determ ined by the interaction of two mating surfaces. The applied load is carried out by the lubricant film and the contacted asperities. FFT techniques are utilized to calculate the surface displacement (forward problem) by convol ution and the asperity contact pressure (inverse problem) by deconvolution for non-periodic surfaces. With the successful implementation of FFT and mu ltigrid methods, the lubricated contact problem can be solved within hours on a PC for the grids as large as one million nodes. This capability enable s us to simulate random rough surfaces in a dense mesh. The load ratio, con tact area ratio and average gap are introduced to characterize the performa nce of mixed lubrication with asperity contacts. Discussions are given rega rding the asperity orientation as well as the effect of rolling-sliding con dition. Numerical results of real rough topography are illustrated with eff ects of velocity parameter on load ratio, contact ratio, and average gap.