Boundary Lubrication in Transient Elliptical Contact: Part 1—Theoretical Formulation and Results

Abstract

The transient elliptical contacts in boundary lubrication widely exist in modern mechanical systems with high durability. However, little attention has been paid to the squeeze effect of fluid film in this condition. A deterministic model which combines the contact mechanics with the pure squeeze lubrication model has been developed with the aim of understanding the squeeze effect of fluid film under the transient boundary lubrication. The leakage coefficient was introduced to capture the fluid leakage of rough surfaces. The squeeze effect of trapped fluid film was confirmed through comparing the fluid film stiffness in boundary lubrication with that of the elastohydrodynamic lubrication. Additionally, the effects of fluid film entrapment/leakage on the boundary lubrication performance were numerically analyzed during transients. The load capacity of the squeeze films is built up due to the trapped fluid film in the micro-valleys, which can be significantly affected by the interfacial shear coefficient of the boundary films. The simulation results show a good agreement with the experiments and justify the present numerical model is feasible in the boundary lubrication regime.