ANALYSIS OF THERMAL ELASTOHYDRODYNAMIC LUBRICATION IN ROLLING / SLIDING CONTACTS

A two dimensional numerical solution to the problem of thermal elastohydrodynamic lubrication of rolling/sliding contacts was obtained using a finite difference formulation. The technique involves the simultaneous solution of the thermal Reynold's equation, the elasticity equation, and the two dimensional energy equation. A pressure and temperature dependent viscosity for a synthetic paraffinic hydrocarbon (XRM-109F) was considered in the solution of the Reynold's and energy equations.;Approximate solutions for the sliding friction force and the mid-film temperature are also developed. The results indicate excellent correlation between the measured and calculated sliding friction force obtained from the finite difference analysis and approximate analytical model.;Two methods for specifying the pressure and surface temperature boundary conditions are presented. For the first method experimental pressure and surface temperature measurements in the elastohydrodynamic lubrication regime for pure rolling and slip conditions obtained by Dow and Kannel 1 were used as the boundary values to evaluate the temperature field within the lubricant film. For the second method the values of pressure and surface temperature were estimated from analysis. The high pressure region of the experimental pressure data 1 closely resembles the elliptical Hertzian pressure equation of dry contact. However, the Hertz pressure equation is only valid for dry contacts. It was modified to account for the pressure rise in the inlet zone of a lubricated contact. Theoretical surface temperature equations were developed. The modified Hertzian and surface temperature equations were used as the boundary conditions to obtain the numerical solution to the theoretical temperature distribution within the lubricant film. The temperature fields as determined by using the experimentally measured data, and as determined from the theoretical equations are presented. The results for both methods show considerable agreement and indicate that for pure rolling conditions the temperature rise in the lubricant film is moderate; whereas for the slip conditions this rise is quite significant.