Low Temperature Tribology - A Study of the Influence of Base Oil Characteristics on Friction Behaviour under Low Temperature Conditions

摘要

A literature review of tribology at temperatures below zero degrees centigrade suggests that very little work has been done in this field. Publications in this field are mainly focussed on lubricants for refrigerant compressors, space and aeromotive applications. In the Northern hemisphere there are numerous applications which are subjected to sustainably low temperatures such as automotive transmissions and hydraulic systems for outdoor use etc. for extended periods during the winter season. This study aims to increase the understanding of low temperature tribology. It relates tribological phenomena to test data from rheology measurements and data from calorimetric studies of phase transitions at different temperatures. Results indicate that there indeed is a connection between these three quite different methods of characterizing oils at low temperatures. Studies have been made on six different base oils and one additive. The measured coefficient of friction (μ) as a function of the sliding speed and temperature show different behaviour for the base fluids, depending on the applied temperature and the sliding speed. At low sliding speeds, μ is rather constant for all the samples, whereas at higher speeds some of them show both increased and decreased μ depending on parameters such as the rheological behaviour of the fluid.