滑动轴承两极润滑状态下润滑行为的自适应调控新方法

To meet the different requirements on the surface wettability of the sliding bearing for lubrication property improvement in the two extreme lubrication regimes, a novel method is proposed for friction and drag reduction through dynamically tuning the wettability of the the bearing surface. Based on eletrowetting theory, the bearing drag reduction is realized as a result of the silp at fluid-solid interface due to surface lyophobicity in hydrodynamic lubrication regime and the bearing friction reduction is also realized at the same time as a result of the relatively thick adsorption film due to surface lyophilicity in boundary lubrication regime. The the mechanism of the influence of the complex three-phase contact lines on the electric field boundary effect under microscopic rough surface and incomplete wetting conditions is investigated, which provides the fundamental theory for the reversible switching of the surface wettability. Considering the cavitation, the theoretical model is presented to calculate lubrication properties. The mechanism and the way of the surface micro-nano structure and the various surface wettability influencing the lubrication properties are investigated, which results in the foundation for surface micro-nano structures planning and wettability transition magnitude determining. The controllable fabrication technics for engineered surface structures with prescribed morphology and its influencing way on conformal insulation film quality have been investigated and typical fabrication process for surface film with reversible wetting transition property is expected. The surface microscopic morphology effects on lubrication properties and reversible wettability attainability are highlighted, based on which, the design rules of the geometrical structure in micro-scale on reversible switching wetting surface are proposed. Implementations of this project will result in the establishment of the relatively complete theoretical basics and fundamental techniques for the design and fabrication of sliding bearing with reversible switching wetting property surface and then present an effective method for the lubrication of spindle bearing system to reduce the fluid drag and then decrease its heat generation.

针对滑动轴承两极润滑状态下润滑行为对表面浸润性的不同要求，提出一种通过轴承表面浸润特性动态调控实现减阻的新方法：基于电润湿理论，实现流体润滑状态下表面疏液滑移减阻和边界润滑状态下表面亲液减小摩擦。研究部分润湿条件下微观粗糙表面复杂三相接触线影响电润湿电场边缘效应的机理，为表面浸润性转变的可逆实现提供理论基础；考虑空化效应建立理论计算模型，研究表面微观结构及不同浸润特性影响两极润滑状态下润滑行为的方式和机理，为表面微观结构设计和可逆浸润转变量化要求的确定提供理论依据；研究规定表面微观形貌可控制备工艺及其影响随形介电层成膜质量的规律，形成一组可逆浸润表面制备的典型工艺。重点揭示微观形貌与润滑特性及可逆浸润实现的相关性，提出可逆浸润特性表面微结构形式设计准则。本项目的研究将为可逆浸润表面轴承的设计和构造提供较为完备的理论基础和技术体系，为减小主轴-轴承系统流体内摩擦从而降低温升提供一种有效方法。

表面润湿性影响流体在表面的铺展及流动行为从而影响摩擦副间的润滑特性，动轴承处于不同润滑状态时对表面润湿性有着不同的要求，边界润滑时要求亲水以形成液膜，流体动压润滑状态时要求疏水以通过界面滑移减小流体内摩擦阻力。本项目针对不同润滑状态下对表面润湿性的不同要求，提出根据润滑状态动态调控表面浸润特性的减阻方法。重点研究表面微观形貌特征与润滑特性以及润湿状态转变的相关性，在润湿状态转变及其影响润滑特性机理方面探索基础理论，为表面微观结构形式设计及润湿状态转变的实现提供理论依据。为了达到上述目标，开展了以下研究：对微观粗糙表面润湿状态转变的热力学过程进行了系统的理论和试验研究，结合力学平衡和微观几何结构特征的研究成果，确定了合理的能垒计算方法及疏水性失稳的判定条件。基于能量最小化方法和电动力学的方法对外加电场条件下润湿状态转变的动力学过程进行了数值模拟，给出了不同表面微观特性条件及电场激励作用下润湿状态转变的条件。适应润湿性转变定量试验验证、PIV观测及摩擦润滑试验耐磨性要求，研究开发了多种基底材料表面微米结构、纳米结构及微纳复合结构制备方法，为项目试验研究及工程化应用奠定了基础。搭建了轴承润滑µ-PIV观测系统和平面微通道测量滑移特性的实验装置，对不同润湿性表面的滑移特性进行了定性对比和定量测量计算，得出了界面滑移与滚动角相关以及微结构的方向性影响界面滑移的结论。进行了不同润滑状态下表面织构及润湿性影响润滑性能的数值模拟：考虑空化效应及界面滑移，建立了具有不同微观结构特征及织构滑移区分布形式的有限元计算模型，得出了表面织构几何形式、特征尺寸及织构滑移区分布对流体润滑性能影响的影响规律；基于平均雷诺方程对织构化表面的润滑性能进行了数值计算，给出了不同表面微织构参数影响混合润滑状态下润滑性能的规律，通过摩擦磨损试验，对理论计算结果进行了验证。