基于弹流润滑反常摩擦现象的界面滑移机理研究

The boundary slippage condition is crucial in the analysis of liquid flow on the micro-nano scale. The related research is considered to be one of the promising direction of the mechanical development in the near future. However, it is still unknown whether the slippage occurs at the solid-liquid interface or the fluid inside under high pressure conditions.The uplifting news is that an anomalous Elastohydrodynamic Lubrication Film(EHL) shape characteried by an inlet dimple is experimentally obtained by our team group and find that friction coefficient curve deviates from the classical Stribeck curve when taking the inlet dimple into consideration. We conjecture that some observed abnomal EHL films and friction behavious under large slidings could be tentatively related to boundary slippage. Unfortunately these proposed boundary slippage could not be confirmed because of the lack of theoretical analysis.So this project aims to study the mechanism based on the slippage phenomena of highly pressurized EHL.Equivalent ultra-low viscosity pseudo boundary slippage model instead of limit shear stress rheological model and continuous conditions is set with the aid of viscosity-temperature relationship interface.Contact beam interferometry technology with impact oil technology, a new method is expected to design in order to measure the occurrence of boundary slippage,so that the influences of the influences of pressure, surface energy, entrainment velocity will be explored.The influence of boundary slippage will be refered to design the friction measurement system and solve the effect of bearing revolute pair on the friction measurement results. A new model is built by the experiment observed the abnormal friction change.So it can reveal the abnormal friction mechanism and correct the classical Stribeck curve and provide some references on lubrication problems in engineering.

界面滑移对微纳米尺度下流体动力学行为有重要影响，其相关研究被认为是今后力学发展的新方向之一。在高压条件下滑移产生在固液界面处还是流体内部一直存在争议，申请人所在课题组在实验中成功地观测到带有入口凹陷的弹流油膜，发现当入口凹陷出现时摩擦系数曲线偏离了经典Stribeck曲线，推测归因于界面滑移，但缺少理论分析支持。基于此本项目研究高压条件下界面滑移机理，以等效超低粘度的伪界面滑移模型代替极限剪应力流变模型，借助粘温关系建立界面连续条件，设计有效数值方法求解。结合光干涉技术和冲击封油技术测量界面滑移的发生位置，分析压力、表面能、卷吸速度等对界面滑移的影响。设计摩擦力测量系统，解决轴承转动副对摩擦力测量结果的影响，根据实验观察到的反常摩擦力变化建立新的滑移模型，揭示反常摩擦力产生机理。并对经典Stribeck曲线做补充修正，为工程实际中通过改进润滑方式来减小摩擦力提供参考。

针对实验系统玻璃盘支撑轴承转动副对摩擦力测试的影响进行了系统的研究，结果表明轴承转动副的阻力对摩擦力测试有不可忽视的影响，通过实验得到了摩擦力测量的修正公式。.对界面滑移条件下弹流接触副的摩擦力特性进行了研究。为实现界面滑移条件下弹流接触副摩擦系数的精确测量，开发了专用的摩擦力测力系统。通过机器视觉系统实时跟踪观察发生界面滑移时的油膜形状变化，同时采集摩擦力。实验研究了入口凹陷的产生与消失过程中，点接触润滑副摩擦系数的变化规律。通过实验揭示了卷吸速度、载荷以及不同润滑油对摩擦系数变化趋势的影响。在考虑界面滑移的影响下，对经典Stribeck 曲线做补充修正，可以给工程中的摩擦力与摩擦系数的应用提供参考。.基于“同一油品相同的密度对应相同的黏度”这一假说，通过引入广义黏度，把润滑油的Eyring流动处理为广义牛顿流动，在不同赫兹接触压力和卷吸速度下，在滑滚比宽广的变化范围内开展了定量的热弹流数值仿真. 仿真得到的摩擦系数与实验结果良好的吻合程度证实了所用的密度与黏度关系假说的合理性。提出了一种不需要黏温系数而得到热条件下润滑油黏度值的算法，并用之得到了合理的广义牛顿热弹流解..研究钢球的横向振动对热弹流润滑的影响，从而用时变热弹流理论解释凹陷的移动现象，解决了国内外专家对移动凹陷现象的猜测。建立了卷吸与滑动正交的热弹流润滑理论模型，研究了对固体表面间速度夹角的变化对润滑膜形成的影响，揭示此类传动界面的润滑机理。