A Simulation Study of Running-in Wear Effect and Its Influence on Average Flow Factors

Abstract

The profile of a new rough surface continuously varies under a running-in condition. A small change in the distribution of the asperity heights can have a significant effect on the hydrodynamic lubrication performance as the film thickness varies. For a realistic understanding of the thin-film lubrication phenomenon, it becomes imperative to consider the effect of “running-in wear.” To consider its effect on the hydrodynamic lubrication performance of tribological elements using an average flow model approach, a theoretical simulative study of running-in wear and its effect on pressure and shear flow factors has been presented that is based on numerical flow simulation of isotropic flattened rough surfaces. An average Reynolds equation for flattened rough surfaces is expressed in terms of pressure and shear flow factors. The flow factors have been computed by solving the conventional Reynolds equation using FEM on a model bearing of rough surfaces for various stages of running-in wear. The computation is performed by numerically generating the isotropic flattened rough surfaces for the different value of η, a normalized factor that is a measure of magnitude of running-in wear. The pressure and shear flow factors are expressed as a function of dimensionless parameters h/σ and η. The study shows that the value of pressure flow factors increases whereas that of shear flow factors decreases with the increase in the magnitude of η. The governing equations for flow factors and the curves presented in the paper are useful as these are required for the solution of an average Reynolds equation for studying the effect of running-in wear in lubrication problems using an average flow model approach.