Rheological Study of Solidified Traction Oils under High Pressure by Observation of Deformed Microspheres

Abstract

The rheological properties of solidified traction oils used in continuously variable transmissions (CVTs) under pressure were evaluated by observing large plastic deformation of metal microspheres (φ about 0.07 mm), occurring due to non-hydrostatic pressurization in these oils using a diamond-anvil pressure cell. The solidification pressure values obtained by observing aluminum sphere deformation were almost equal to those extrapolated from high-pressure viscosity; thus, aluminum sphere deformation experiments are effective for evaluating solidification pressure. Shear stresses of the solidified oils could be estimated up to 5 GPa from the deformed Cu spheres based on several assumptions. The stresses were almost equal to the mean shear stress obtained from a traction test between 1.0 GPa and 1.7 GPa and were below it for pressures above 1.7 GPa. The stress values varied little among different oils.

Keywords

• lubricant
• high pressure
• solidification
• traction oil
• shear stress
• limiting shear stress