Plastic Deformations of Microspheres by Solidified Lubricants and Lubricants' Shear Characteristics under Very High Pressure (Part 1): Observation of Plastically Deformed Microspheres

摘要

In order to grasp the possibility of evaluating shear properties for solidified lubricants under high pressure, plastic deformations of microspheres in pressurized solidified lubricants were observed employing a diamond-anvil pressure cell. Large deformations (two or three times larger than the original dimensions) of gold sphere and copper sphere were observed for traction oil SN100 at about 5 GPa, which is far higher than the solidified pressure (about 0.5 GPa). The degree of sphere deformation depended on the material of the pressure chamber. A copper chamber whose strength is lower than that of beryllium-copper enabled large deformation of spheres. Most of the spheres deformed in an elliptical shape. The sphere deformations for an ester oil, dioctylsebacate, were small, which was due to high solidification pressure (2.6 GPa). Those for traction CVT oil were larger than SN100, which possibly contributes to high traction performance. The pressure of starting deformation of gold sphere agreed with the estimated solidified pressure from high-pressure viscosity for all the lubricants. These deformations caused by the non-hydrostatic pressure (shear resistance appeared) for solidified lubricants and the possibility of estimating their shear properties was confirmed.