Modeling of Elastohydrodynamic Lubrication and Friction Characteristics of Real Rough Gear Surfaces

In engineering practice, gear tooth surfaces exhibit significant roughness characteristics. The complexity of rough tooth surface morphology poses challenges to the study of gear lubrication and friction mechanisms. To address this issue, a dynamic elastohydrodynamic lubrication model considering the effects of real rough gear surfaces was developed by mapping the actual microscopic topography of gear surfaces using an ultra-high-resolution microscopic system and incorporating the Reynolds equation, film thickness equation, and load balance equation. The effects of lubricant viscosity, gear speed, and mesh force on oil film pressure, thickness, and friction coefficient under rough surface conditions were investigated. The results show that as tooth surface machining quality deteriorates, oil film thickness fluctuations intensify, local film rupture occurs, and friction coefficient increases significantly. An increase in lubricant viscosity and gear speed leads to thicker oil films but lower pressure, accompanied by a rise in friction coefficient. An increase in dynamic mesh force broadens the contact area, reduces film thickness, and significantly increases film pressure. These findings provide a theoretical basis for lubrication design and efficiency optimization in high-precision gear transmissions.