A new approach is utilized to determine the effects of surface roughness on partially lubricated contacts. An average Reynolds equation for rough surfaces is defined in terms of pressure and shear flow factors, which are obtained by numerical flow simulation. Through the use of measured or numerically generated rough surfaces, any three dimensional roughness structure can be analyzedwith this method. The average Reynolds equation is obtained for isotropic surfaces, and for surfaces with directional patterns. The flow factors for these surfaces are expressed as empirical relations in terms of hi a and a surface characteristic y defined as the ratio of x and y correlation lengths. A new approach is utilized to determine the effects of surface roughness on partially lubricated contacts. An auerage Reynolds equation for rough surfaces is defined in terms of pressure and shear flow factors, which are obtained by numerical flow simulation.Through the use of measured or numerically generated rough surfaces, any three dimensional roughness structure can be analyzed'with this method. The auerage Reynolds equation is obtained for isotropic surfaces, and for surfaces with directional patterns. The flow factors for these surfaces are expressed as empirical relations in terms of hi r'f and a surface characteristic ' Y defined as the ratio of x and y correlation lengths.Transactions of the ASME Downloaded From: http://tribology.asmedigitalcollection.asme.org/ on 09/17/2013 Terms of Use: http://asme.org/terms

The Average Flow Model introduced in an earlier paper is extended to include sliding contacts by deriving the shear flow factor for various roughness configurations. Similar to the pressure flow factors, the shear flow factor is obtained through numerical flow simulation on a model bearing having numerically generated roughness. The flow factors for isotropic and directional surfaces are expressed as empirical relationships in terms of h/σ, a surface pattern parameter γ defined as the ratio of x and y correlation lengths, and the variance ratio Vr1 which is the ratio of variance of surface 1 to that of the composite roughness. Expressions for the mean shear stress and horizontal force components due to local pressure in rough bearings are derived through the definition of shear stress factors, also obtained through simulation. The application of the average Reynolds equation to analyze roughness effects in bearings is demonstrated on a finite slider. The effects of the operating parameters as well as the roughness parameters on mean hydrodynamic load, mean viscous friction and mean bearing inflow are illustrated.

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