Influence of Surface Roughness Wave on Thermal Elastohydrodynamic Lubrication of Involute Spur Gears

Abstract

There is no perfect smooth surface in project.The elastohydrodynamic lubrication(EHL) oil film thickness between the two meshing gear teeth has the same order of magnitude with the cutting tooth surface roughness height in most cases.So the influence of surface roughness on the EHL of gears should not be ignored in engineering project.A series of sinusoidal waves are assumed on the tooth surface and the lubricant is assumed to be a Newtonian fluid.Based on the multi-grid(MG) method for solving the pressures, the multi-level multi-integration(MLMI) approach for evaluating the elastic deformations, a sequential column sweeping scheme for solving the energy equations, a numerical method for solving the pressures, film thicknesses, and temperatures in the lubricated regions is developed, and the full numerical solutions of involute spur gears are obtained.The influence of tooth surface roughness, thermal effects and transient effects on the EHL is taken into account.The influence of the roughness wave profile on the EHL is discussed.The results show that the tooth surface roughness has strong influence on the oil film pressure distribution and the temperature rise between the contact teeth.A series of roughness waves make oil film pressure and film thickness oscillating, and make the minimum film thickness thinner, the maximum pressure larger and the maximum oil temperature rise higher.So it is more likely to bring out the fatigue failure of the gear teeth.