Some influence parameters on greases lubricated rolling contacts service life

The present tendencies in miniaturizing the equipment and the machine tools, decreasing the aircraft weight, avoiding the complicated oil cooling and lubricating systems, running the ball or roller bearings in contaminated media or in the presence of the electric fields, determined a higher use of the lubricating greases in technical applications which is estimated at about 80% of the bearings assemblies. In normal grease lubricated bearings operating conditions it is considered that an acceptable film thickness is realized and the damaging phenomenon is the classic one as contact fatigue or abrasive wear. When temperatures are higher than 60–70°C and high speeds occurs greases service life is strongly decreasing, bearings service life being dependent on lubricants service life. Because we found a lack of technical information about this field in the scientific literature, in the present paper, a global approach concerning the problem of bearings greases deterioration and a lubricants service life calculating equation are presented.