Friction Performance of Nano-copper as a Rapeseed Oil Additive Under Electromagnetic Field

Abstract The present article explores the frictional properties of rapeseed oil containing nano-copper additives under an electromagnetic environment using an improved four-ball testing machine. The influence of nano-copper additives on frictional properties was also investigated. The results indicate that regardless of the presence of an electromagnetic field, the friction coefficient decreases with increasing rotational speed. The best antiwear and antifriction performance was achieved when 0.01 wt% nano-copper was added, with a significant decrease of ∼8.4% in average friction coefficient and 19% in average wear spot diameter (AWSD) at 0 Tesla (T). At 0.2 T, the friction coefficient decreased by ∼9.6%, while the AWSD was comparable to 0 T. However, compared to 0 wt% at 0 T, the AWSD decreased by 10%. When the electromagnetic field intensity H = 0.05 T, the friction coefficient and AWSD are relatively stable, showing that a weak magnetic field is beneficial for improving the wear resistance of lubricating oil. When H = 0.2 T, the friction coefficient and AWSD increase significantly, indicating that a strong magnetic field is not conducive to improving the antiwear and antifriction performance. Mechanism analysis shows that the physical effects of electromagnetic fields promote wear resistance at low intensities and weaken wear resistance at high intensities. Chemical effects interfere with rapeseed oil molecules and nano-copper electron clouds, disrupting synergistic lubrication and increasing the friction coefficient.