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This paper presents a unique line-contact EHL test rig. One of the features of the rig is that the EHL junction is formed by a cylindrical roller in contact with the internal surface of a cylindrical ring. With this design configuration, only a very small amount of lubricant is needed even for high speed testing as the centrifugal force maintains a good oil supply to the contact region. The roller and the ring are driven separately by servomotors. The roller assembly is mounted on a platform supported by a hydrostatic air bearing to allow accurate traction measurement. With a coated sapphire ring, the EHL film thickness in the contact zone can be measured by means of optical interferometry. The control and data acquisition systems are integrated in a Labview environment, and the test sequence can be programmed and automatically carried out by the control program. The innovative design features and test parameters of the rig are presented along with a set of typical test results.

Traction machines have been frequently used to study the rheological properties of lubricants in elasto-hydrodynamic lubrication (EHL) contacts. Fundamental properties are inferred from EHL traction measurements based on the average pressures and temperatures in the contact. This average approach leads to uncertainty in the accuracy of the results due to the highly nonlinear response of fluid rheological behavior to both pressure and temperature. A non-averaging method is developed in this paper to determine the elastic and plastic properties of traction fluids operating in EHL contacts at small slide-to-roll ratios. A precision line-contact traction rig is used to measure the EHL traction at a given oil temperature and Hertz pressure. By choosing a sensible pressure-property expression, the parameters of the expression can be determined through the initial slope and peak traction coefficient of the traction measurements.