Molecular Dynamics Simulation for Effect of Nanoparticle Additives on Boundary Lubrication

The boundary lubrication behavior of Cu nanoparticles in n-hexadecane was investigated under different loads by experiments and simulations herein. Boundary lubrication model with sinusoidal rough peaks was established. The density distribution of the lubricant along the film thickness with and without Cu nanoparticles were simulated at different loads using MD respectively. The shear velocity in the opposite direction was applied to the upper and lower solid walls of the system, and the stress between the wall atoms and the copper particle atoms, the friction force of the solid-liquid interface, the normal pressure and the friction coefficient were calculated. The friction coefficient of the lubricant containing nano-copper particles was measured with a micro-nano scratch meter. The results show that the base oil n-hexadecane in the two lubrication systems is stratified under different pressures. There arc still a small amount of n-hexadecane molecules at the contact interface when the nano-rough peaks are directly contacted, and the arrangement direction of the molecular main chain is the same as the shear direction. Cu nanoparticles may reduce the maximum stress of solid wall by 35.3% and improve the bearing capacity of lubrication system at 200 MPa. The lubricating oil film of lubrication system without Cu nanoparticles breaks at 50 MPa, while that of lubrication system with Cu nanoparticles breaks at 200 MPa. The friction coefficient of two lubrication system under boundary lubrication is simulated, which is in accordance with the experimental measurement. © 2023 China Mechanical Engineering Magazine Office. All rights reserved.