Abstract: The influence of surface roughness is generally not considered when the micropolar fluid lubrication of bearings is studied. To deal with bearing lubrication under heavy load conditions. Establishing a mathematical model that comprehensively considers the combined effects of surface roughness and micropolar fluid is necessary. The generalized average Reynolds equation for any three-dimensional rough surface bearing is derived based on the average flow method. The variation of dimensionless maximum average film pressure with eccentricity ratio, dimensionless micropolar fluid characteristic length, and coupling coefficient under different combined roughness root mean square and surface pattern parameters are analyzed. The results show that the combined roughness root mean square parameter has strong coupling characteristics with the dimensionless characteristic length and coupling coefficient of the micropolar fluid. With the decrease of the dimensionless characteristic length of the micropolar fluid or the increase of the coupling coefficient, the larger the root mean square value of the combined roughness of the bearing, the larger the dimensionless maximum average film pressure of the bearing. And the surface pattern parameters also have similar characteristics. The proposed generalized average Reynolds equation supplements the existing micropolar fluid lubrication theory. It can be conveniently used for the micropolar fluid lubrication analysis of any three-dimensional rough surface bearing. In addition, the proposed generalized average Reynolds equation applies not only to the friction pairs such as journal bearing and thrust bearing in the field of hydrodynamic lubrication but also to the friction pair such as piston ring-cylinder in the field of mixed lubrication.

Key words: journal bearing, micropolar fluid, surface roughness, average flow method