Rolling bearing lubrication with grease at low temperatures

Grease possesses a multitude of technical and economic advantages and as a result around 90% of all rolling bearings are lubricated with grease. Little is known up to now concerning the mechanisms of lubrication, especially under the influence of low temperatures. The aim of the present article is to describe some of the investigations conducted at the Institute of Machine Elements, Engineering Design and Tribology concerning rolling bearing lubrication with grease at low temperatures. First of all, the testing bench which was set up for theinvestigations is described. Using this testing bench, realistic operating conditions for the greases and rolling bearings can be simulated in terms of temperature level and temperature constancy as well as load and speed. Using two commercially available greases, the basically different behaviour of these greases under the influence of constantly low temperatures was shown. Using UV-induced fluorescence, the lubricant supply of the roller ends as a function of grease type, temperature and load was investigated, since lubrication failure generally has a damaging effect on this contact. First, the measurement set-up is described, and then the results of the experiments are presented. In these experiments, a significant difference in the greases studied was detected with regard to the lubricant supply of the contact, and this difference is in agreement with the different behaviours of the greases at constantly low temperatures.