Thermal elastohydrodynamic lubrication by non-Newtonian fluids with rough surfaces: Its application to spur gear transmission

A theoretical investigation of the behavior of thermal elasto-hydrodynamic lubrication by non-Newtonian fluids under rough surfaces has been conducted. The study consists of two parts. In the first part, a general line contact elasto-hydrodynamic lubrication model is derived, which integrates several critical effects such as rheological characteristics of lubricants, roughness and temperature into one system. A more effective numerical algorithm is adopted to obtains the solutions under wide ranges of operating conditions. Observations and extensive discussions of the results lead to further understand the phenomena of the different interactions among the various factors in a elasto-hydrodynamic lubrication process.;In the second part, the forgoing theory is applied to the specific problem of the spur gear transmission. Various kinematics and dynamics features associated with the lubrication process in the spur gear have been investigated.;The results has shown that the pitch point EHL film thickness does not reliably represent the minimum EHL film thickness. The full thermal EHL calculation along the line of action is needed in order to predict the minimum film thickness and pressure peak more precisely. The actual location of the minimum film thickness along the line of action is strongly influenced by the dynamic load sharing profile. Surface roughness has the moderate effect on the gear lubrication. The effects become more significant when the roughness amplitudes approach the nominal film thickness. Non-Newtonian behavior of lubricants may significantly alter the level of the minimum film thickness and temperature distribution, but has only small effect on pressure peak.