Molecular Dynamics Simulations On The Lubricating Properties Of The Nano-scale Oil Film

Focus on the long-term sustainable development, lubrication design has become an inevitable trend of mechanical science. It’s used for saving energy and raw materials, thereby improving the life and reliability of machinery and equipment. Lubrication technology is to form a lubricating film by applying lubrication between the friction surfaces, so as to avoid direct contact with the friction surface and reduce friction and wear. In this paper, the structure and lubrication properties of the nanometer diesel oil films were studied. Due to the complexity of the diesel oil components, there is little study on its nature in the simulation up to now.The structures and potential parameters of the main organic molecules in0#diesel oil were calculated by using quantum mechanics according to its component analysis test results in this paper firstly. After that, a molecular model of Fe substrate/diesel oil/Fe substrate was established, ensuring that the proportion of alkanes to cycloparaffin in the diesel oil films is4:1. Molecular dynamics (MD) simulations were performed to investigate the structural properties of diesel oil films confined between two solid Fe substrates under the different film thicknesses. To characterize the molecular conformations in the interfacial region, the distributions of atoms and chain ends in the diesel oil films during a lubrication process have been analyzed in a detail. The results showed the solid-like phenomenon and bridging conformation in the thin films during the lubrication process.At last, the friction and equivalent shear viscosity properties of the diesel oil films under different film thicknesses were analyzed and discussed. The results showed that the friction force of the diesel oil decreased as the thickness of the diesel film increased. It’s similar to the situation in the macroscopic state. So it also has some help to the study of the macroscopic states. But in the same time, the equivalent shear viscosity of the lubricating oil films is also reduced, which is opposite to the macroscopic state.It shows that situations in the microscopic and macroscopic have some similar points and different aspects. These results may have some guidance for future research of nano-scale lubrication.