Temperatures and friction at lubricated rolling/sliding contacts

The parameters affecting the temperatures and friction at lubricated rolling/sliding contacts of the Hertzian type are investigated and examined in relation to the failure of contacts by scuffing and their performance under traction conditions. Based on the critical temperature criterion for scuffing, an experimental technique for the direct measurement of a. lubricant's critical temperature is proposed and evaluated. Blank temperature studies are carried out and further information concerning the heat transfer coefficients of machine components made available. On the question of heat generation at the contact, a thermal analysis of the lubricant film is developed, providing complete distributions of temperature, shear rate, viscosity, and shear stress throughout the contact region. A marked dependence of these characteristics upon the physical properties of the lubricant is observed and the results assist not only in the prediction of scuffing but also in understanding the frictional behaviour of rolling/sliding contacts. By comparison with friction measurements made on a traction machine, the theory gives a reasonable estimate of the friction-sliding characteristic provided the non-Newtonian behaviour of the lubricant is represented by a suitable model in the calculations. The Maxwell fluid model is that adapted for the present investigation. The results for shear stress are considered to be of further use in the study of failure by pitting