【作者】 蒋开；

【导师】 陈云飞；

【作者基本信息】 东南大学 ， 机械设计及理论， 2005， 硕士

【摘要】 微电子机械系统以及纳米机械的迅速发展对于分子尺度下器件摩擦、润滑和磨损特性的研究提出了迫切的要求。因此从分子层面上研究摩擦的起源对于掌握摩擦的本质以及实现超滑零摩擦有着重要的意义。同时,模拟分析超薄膜流体的性质,寻找其与宏观连续体模型的联系与区别,对于未来微流管设计,建立微观流体的基础理论有一定的指导意义。本文首先介绍纳米摩擦、润滑研究的计算机模拟工具-分子动力学,并对于本文固体、流体滑动过程的模拟给出了特别的说明。在此基础上,对干摩擦进行了模拟,根据模拟结果并结合Tomlinson模型,分析了在微观情况下,超滑现象的产生条件以及在低速时动摩擦力随滑动速度增加而增加的机理。然后,构建Couette流模型,用分子动力学模拟超薄膜润滑的边界条件,着重模拟了温度对于滑移长度的影响,结果显示:在固液作用势较强的情况下,滑移长度随着温度的增加而增加;在其较弱的情况下,随着温度的增加,滑移长度反而下降。对于这种现象,提出了滑移界面上下的层状有序化差异程度是导致滑移的主要原因。最后模拟了纳米轴承的流体动压润滑现象,结果表明:在低速滑移情况下,经过边界条件修正的雷诺方程仍然可以使用,润滑膜的承载量随着滑移速率的增加而增加;然而在高速下,雷诺方程失效。更多还原

【Abstract】 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.更多还原