An Internal Line-Contact EHL and Traction Test Rig

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. This test rig can produce accurate EHL traction and film thickness data in a line contact. It may be used to facilitate fundamental studies of lubricant rheology and development of rheological models.