Effects of External Electric Field on the Tribological Properties of <scp>UHMWPE</scp> Under Dry Friction and Pure Water Lubrication Conditions: A Combined <scp>DFT</scp> and <scp>MD</scp> Simulation Study

ABSTRACT Polymer tribopair materials (such as UHMWPE) are widely used in complex environments like dry friction and pure water lubrication. However, with the rapid development of electromagnetic technology, how electric fields influence the tribological performance of UHMWPE and the underlying mechanisms remain unclear. Understanding this mechanism is crucial for enhancing the application potential of polymer tribopair materials in specialized electromagnetic working conditions. This study uses DFT and MD to investigate the effects of electric field parameters (intensity and direction) on the tribological performance of Fe/UHMWPE tribopairs under dry friction and pure water lubrication conditions. The results show that, under dry friction conditions, the electric field's effect on UHMWPE is minimal due to the lack of polar groups. Under pure water lubrication conditions, parallel electric fields in the range of −0.5 to −0.2 V/Å significantly increase the average friction forces, while vertical electric fields have little effect. DFT calculations show that X‐ and Y‐axis electric fields reduce the LUMO energy of water molecules, while Z‐axis electric fields increase the Δ E energy gap and dipole moment. This study provides guidance for optimizing the tribological performance of UHMWPE in complex electric field environments and recommends using vertical electric fields in water environments to reduce friction fluctuations and extend the service life of tribopair materials.