KEYWORDS

Lubricant Physical Analysis: Rheology, Lubricant Physical Analysis: Viscosity, Surfaces:Coatings, Friction-Reducing

MEASUREMENT OF LUBRICANT VISCOSITY AND DETECTION OF BOUNDARY SLIP AT HIGH SHEAR RATES

Rheological property of lubricants at high shear rates is essential for tribological design of high speed machine components such as bearings and gyroscopes. A novel rheometer with the maximum shear rate of 1000000/s has been fabricated. The gap width between the parallel plates is controlled in the range from 20 to 500 μm by a piezo actuator. The viscous shear torque is measured with a feed-backed laser reflection technique. Some preliminary experiments of low viscosity liquids have been conducted on the rheometer compared with those obtained on commercial rheometer. To investigate the effect of surface energy of the testing plate, a PFPE film is coated on the stainless steel upper plate by dip coating process. Test results of the PFPE coated sample indicated that the viscous shear resistance is reduced by about 10% to 20% compared with the bare plate, implying that possible boundary slip occurred at the liquid/solid interface.

AUTHORS 

Xiang Yu, Yu Tian, Jun Zhang, State Key Laboratory of Tribology, Tsinghua University, Beijing, China and Weibin Liang, Department of Precision Instrument, Tsinghua University, Beijing, China