Correlation between friction and flow of lubricating greases in a new tribometer device

摘要

A tribometer requires speed and normal force control, as well as a torque measurement, to acquire tribological data. An air bearing-supported rotational rheometer allows the measurement of the same variables, but in a broader range and with better accuracy. This and the intension to measure Stribeck curves, as well as the static friction with one single instrument, led to the idea to design an accessory turning a rheometer into a high-resolution tribometer based on a ball on pyramid principle. Speed ramp and static friction measurements of oil-lubricated systems illustrate the performance of the rheo-tribometer. The flow behaviour of greases is more complex, and extensive rheological and tribological testing was performed on three greases of the American National Lubrication Grease Institute classes 0, 1 and 2 at the temperatures of 25 and -40℃. The influence of temperature could be monitored, and a correlation between rheology and tribology was found. To link the model system with real applications for greases, a ball bearing fixture for the tribological accessory has been designed for which first results are presented.