界面振动对摩擦影响的实验和机理研究

Three frictional models will be established in this project on the basis of the previous theoretical and experimental studies of friction in nanoscopic and mesoscopic fields. The asperity model is the basic one and bridges the gap between nanoscopic friction and mesoscopic one. The second model is the contacting-group (CG) model which builds the connection from mesoscale to macroscale for friction. And the third macroscopic frictional model describes interfacial friction between bodies. The CG model is made up of a number of asperities and the macroscopic model is established by several CGs. The macroscopic model of multi-scales and multi-layers connecting nanoscopic field to macroscopic friction is built via theories of tribology and methods of multibody system dynamics. These frictional models will be applied to seek the intrinsic reasons why interfacial vibration can reduce friction and to achieve quantitative connection between the vibration characteristics and the static/dynamic coefficient of friction on a contacting interface. The investigation in this project is expected to provide a novel frictional model to study the dynamic behaviors of mechanical systems for actual engineering practices.

本项目在前人微观模型的理论与实验基础上，分别构建“微凸起”单元（微观与细观尺度结合）模型、“接触团”单元（细观与宏观尺度结合）模型和接触摩擦界面（宏观尺度）模型。由若干个“微凸起”整合为一个“接触团”模型，再由若干个“接触团”整合成一个完整的宏观尺度摩擦机理模型。将现代摩擦学的相关理论与多体系统动力学建模方法相结合，构建从微观到细观再到宏观的多尺度分层次的摩擦模型；并采用实验验证和理论分析的研究手段，探索界面振动对摩擦影响的内在机理，给出物体界面振动特征影响静、动摩擦系数的定量关系。为实际工程中含摩擦机械系统动力学的研究提供新型的摩擦模型。

物体接触界面上存在的振动降低了摩擦。界面振动分为切向振动与法向振动，本项目的研究表明界面上法向振动与切向振动对摩擦的影响机理是不同的。.1）界面法向振动加快了接触微凸起对断裂的频率，也就是加快了接触微凸起对正在累积的切向弹性势能的释放频率，使得切向弹性来不及积累更多的弹性势能，从而降低了切向的摩擦阻力。项目组建立了新的模型，并得到国际权威期刊上摩擦力显微镜实验的验证。.2）通过滑块-振动台的实验研究发现，面内振动引起摩擦降低的原因是界面存在stick-slip现象，如果滑动方向不变，切向振动不能使动摩擦降低。切向振动对摩擦的影响可以采用Coulomb摩擦定律进行描述。.本项目的研究有助于解决工程问题中干摩擦的“不确定性”。