A simplified impact microviscometer

The flow properties of liquid lubricants at high pressures have been investigated by optical measurements of the elastohydrodynamic contact between impacting bodies. For pressures greater than about 0.2 GPa it is necessary for the optical system to utilize two separate laser beams in order to be able to determine the refractive index and density of the lubricant directly. In examining the effectiveness of the method for measuring viscosities at low-moderate pressures, using low-modulus materials or small curvatures for the striker, it has been found that a much simplified instrument can be used which is of acceptable accuracy under many circumstances. The essential features of such a viscometer are described together with typical experimental results. It is concluded that a simple commercial instrument could be developed along the lines discussed. © 1992.