高速/超高速弹流润滑行为与机理研究

The rolling bearings used in major equipment such as high-speed railway train, aero-engine, usually operate at high-speed or ultra-high speed conditions, which puts forward increasingly demands for rolling bearing performance. As a consequence of the increasing rotational speeds requirements, the behaviors and mechanism of elastohydrodynamic lubrication (EHL) at high/ultra-high speed condition must be systematically explored as the main lubrication mechanism of rolling bearing. To this end, this project is proposed to conduct the fundamental research on the behavior and mechanism of high/ultra-high speed EHL based on experiment and theoretical modeling. The main research includes: (1) To develop new high/ultra-high speed EHL test rig based on ball-on-glass ring mode, which can measure lubrication film thickness at speeds up to about 60~80 m/s, interfacial limit shear stress between the lubricant and the surfaces, and boundary slip. (2) To systematically investigate the distinct behaviors of EHL at high/ultra-speed conditions based on the developed test rig. (3) To develop a through-thickness velocity profile reconstruction scheme and a interfacial slip model, which are integrated to develop a complete lubrication model to investigate the effect of different factors such as starvation, boundary slippage, temperature rise and shear thinning on the high/ultra-speed lubrication and further to explore the lubrication mechanism. (4) Furthermore, to investigate the effect of the dynamics resulting from the high-speed on lubrication performance. This study will provide a new test tool for high-speed lubrication oil film measurement and a complete numerical model with the consideration of coupled effect of different factors, the outcomes from this study will provide theoretical support for the design of high-speed rolling bearing.

高铁、航空发动机等重大装备用滚动轴承多工作在高速和超高速工况，对轴承的高速性能提出了非常高的要求。为此作为滚动轴承的主要润滑机理，弹流润滑在高速和超高速工况下的行为规律和机理还有待深入揭示。本项目采用实验测量和理论建模相结合的方法，开展高速/超高速弹流润滑行为和机理的基础研究。主要研究内容包括：（1）发展球-环模式高速弹流润滑油膜测量新系统，实现线速度达60m/s~80m/s的高速润滑油膜、固液界面剪切强度和界面滑移的测量；（2）系统研究高速/超高速润滑的一般规律和行为；（3）发展沿膜厚方向速度轮廓重构方法，建立界面滑移理论模型，并集成多因素耦合润滑分析模型，揭示各种因素对高速润滑接触行为的影响规律，进而揭示高速润滑机理。（4）进一步探索系统动力学行为对高速润滑的影响规律。本项目将为高速润滑研究提供新的实验平台、构建较完备的理论分析模型；研究成果将为高速滚动轴承设计提供理论支撑。

数控机床、航空发动机等重大装备正向高速化方向发展，其主轴所用滚动轴承多工作在高速工况，对轴承的高速性能提出了非常高的要求，然而作为滚动轴承主要润滑机理的弹流润滑研究多集中在5m/s以下的研究。本项目以高速滚动轴承为主要对象，通过研发高速弹流润滑测量实验台、建立高速弹流润滑模型，系统研究了高速下弹流润滑油膜变化行为，揭示了其内在机理。（1）突破了传统球盘模式光弹流实验台限制，研制了球-环模式高速弹流润滑实验台，更真实地模拟了滚动轴承中滚动体与滚道的润滑接触和高速离心效应；（2）基于矩阵光学理论建立了球-镀膜内圆柱面接触区膜厚测量光学模型，揭示了球环模式下玻璃圆环引起的光学系统对焦不准确是导致光干涉图像模糊的原因，提出了通过增加平凹柱面透镜修正光路实现清晰成像的方法，并给出了清晰成像的条件。（3）系统开展了牵引滚动模式下的高速弹流膜厚测量实验。结果表明，低速时干涉图像为经典“马蹄形”，润滑膜厚符合Homrock-Dowson公式的预测；高速下经典弹流特征减弱，变为压缩“V”形，油膜厚度远低于预测，中心区油膜轮廓由平坦变为收敛楔形。高速牵引模式下，滑动易于发生，卷吸效应减弱导致油膜厚度减小；滑动引起接触区内的热效应，导致油膜厚度进一步减小；此外，滑动还将导致润滑油在接触表面上发生滑移，从而影响高速弹流润滑性能。（4）建立了考虑界面滑移和热效应的点接触分层滑移润滑模型，以润滑油在表面的剪应力是否超出极限剪应力作为判断滑移是否发生的标准，推导了分层润滑模型下考虑不同滑移状态的修正Reynolds方程。模型的油膜厚度计算结果与球-环弹流润滑实验匹配良好；系统研究了高速下润滑油膜厚度的变化机理和接触区内的滑移状态。结果表明界面滑移和热效应共同影响了高速弹流润滑膜厚的行为，构建了点接触区滑移状态图。（5）提出了一种结合球环弹流实验和分层滑移模型的新型极限剪应力确定方法，给出了初始极限剪应力和极限剪应力-压力系数的关系式。

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