Assessing friction characteristics of liquid lubricants

Abstract

A reduction in friction in tribological contacts will lead to reduced energy requirements. It is therefore important to be able to measure the frictional characteristics of various liquid lubricants. Current laboratory tests measure friction, but the test rigs invariably induce wear between the mating contacts. A new test rig, the wire-on-capstan rig, is presented which measures friction without inducing wear between the wire and the rotating capstan. All seven lubricants tested (three without additives and four proprietary hydraulic oils) exhibit a reducing coefficient of friction with increasing temperature. Temperatures ranged from 25 degrees Celsius to 100 degrees Celsius. The mineral-based oil showed the lowest friction coefficient and the three synthetic ester based oils produced the highest friction coefficient over the complete temperature range. Future testing will extend the range of operating conditions and product types.