Molecular Dyanamic Study Of Super-Lubricity And Ultra-Thin Film Lubricantion

The rocketing development of Micro-electronic mechanic system (MEMS) and Nano machine urgently required more fundamental and deep research of Nano-tribology. Hence the research of origin and mechanism of friction in molecular level is very meaningful to master the nature of friction and realize super-lubricity. Meanwhile, the simulation of the property of ultra-thin film and the investigation about the dissimilarity and resemblance between it and macro continuous fluid is vital important to design future micro-flow pipe and establish micro-flow theory.In this paper, the computer simulation tool– molecular dynamic simulation (MDs) is introduced at first and its special instruction in simulation of motion is listed as well. With MDs, the dry friction is simulated under many conditions, according to the results, the condition under which super-lubricity appears is acquired and the reason why friction increases with the increase of velocity is analyzed.Moreover, The behavior of the slip between confined liquid and solid walls subject to planar shear is investigated using molecular dynamics simulations. In this simulation model, a wide range of fluid-solid interaction strength, fluid densities and fluid temperature are simulated in order to find the dominant effects on the slip length between the fluid and the solid wall, which is a key parameter for fluid dynamics. Results indicate that the slip length increases with the increase of temperature under large solid-liquid potential, while it decreases under small solid-liquid potential. An assumption about the origin of slip is proposed: structure difference between the neighboring layers of the slippage interface is responsible for the slip behavior.Finally, A Nano-bearing is simulated in this paper, the results indicate that the revised Reynolds'equation is valid under low shear rate. The load from lubricant to the bearing is proportional to the sliding rate, and the normal stress increases with the decrease of film thickness. However, under high shear rate, revised Reynolds'equation is invalid.