The effect of magnetic field and electric current on the friction coefficient displayed by rolling bearing greased by lithium grease dispersed by solid lubricants such as graphite, molybdenum disulphide, talc and polymeric particles is investigated.
It was shown that the magnetic field had no effect on friction coefficient observed for lithium grease without additives. Addition of talc showed significant increase in friction coefficient. This increase was influenced by magnetic field. No significant effect on friction coefficient was observed for grease dispersed by molybdenum disulphide. Generally molybdenum disulphide displayed relatively lower friction coefficient than graphite and talc. Copper particles dispersed in grease displayed the lowest friction values. Friction coefficient displayed by grease significantly decreased with increasing electric voltage due to decrease of grease viscosity as the voltage increased. In the presence of graphite and talc, friction coefficient increased up to maximum then decreased with increasing voltage. Slight friction increase was observed for grease dispersed by copper. The lowest friction coefficient was displayed by molybdenum disulphide dispersing grease. The highest friction coefficient was displayed by grease dispersed by graphite and talc, while the lowest friction was shown for molybdenum disulphide dispersing grease.
Grease dispersed by high density polyethylene showed friction decrease. The lowest friction reduction was observed for polymethyl methacrylate. The strong adhesion of polytetrafluroethylene particles into the sliding surfaces significantly increased friction coefficient. It seems that polytetrafluroethylene particles were adhered to surfaces of inner and outer races as well as the balls. Changing the terminal of the voltage applied to the rotating shaft cased significant friction decrease for polymethyl methacrylate. Viscosity of the grease decreased with increasing the voltage. Friction coefficient decreased for high density polyethylene and polytetrafluroethylene. The lowest friction values were observed at 6 volts which indicated that increasing voltage across the sliding surface could significantly decrease friction coefficient.