A non-averaging method of determining the rheological properties of traction fluids

Traction machines have been frequently used to study the rheological respon ses of lubricants in elastohydrodynamic lubrication (EHL) contacts. Fundame ntal properties are inferred from EHL traction measurements based on the av erage pressures and tempera tures in the contact. This average approach lea ds to uncertainty in the accuracy of the results due to the highly nonlinea r resonse of the fluid such as viscosity to both pressure and temperature. A non-averaging method is developed in this paper to study the elastic and plastic properties of traction fluids operating in EHL contacts at small sl ide-to-roll ratios. A precision line-contact traction rig is used to measur e the EHL traction at a given oil temperature and Hertz pressure. By choosi ng a sensible pressure-property expression, the parameters of the expressio n can be determined through the initial slope and peak traction coefficient of the traction measurements. The elastic shear modulus and the limiting s hear stress of the lubricant corresponding to a single pressure can then be calculated for a range of pressures and temperatures of practical interest . Two high-traction fluids are studied, and their elastic moduli and limiti ng shear stresses presented. (C) 2000 Elsevier Science Ltd. All rights rese rved.