表面形性演变对动态橡胶密封性能的影响研究

Successful seal products need to have three functions: sealing, lubrication and pumping action simultaneously, which are accomplished through the contact interface between the seal and counterpart. During running process of dynamic rubber seals, the contact interface is subjected to heat, lubricant medium and friction stress. This will lead the surface morphology features and properties to change due to molecular structure change, microvoid appearance resulted from particle shedding, wear stripe formation and asperities distribution change of rubber surface, which affects the lubrication, friction and wear behavior of the contact interface. Consequently, the sealing performances are reduced. The method of theoretical analysis combined with experimental measurement is used in this study. The quantitative description method and evolution rule with running time of the rubber surface morphology features and properties are established. The influence of surface morphology features and properties on the friction and wear behavior is studied, and the main wear patterns are also determined. Based on the thermal-liquid-solid simulation model considering the interface slip characteristic, the variation of dynamic seals’ performances with running time is analyzed. According to the variation results, the seal failure criterion is proposed, and the failure mechanism is also investigated. Two means to delay the seal failure are presented, which are surface texturing on the shaft and surface modification on the rubber. Anticipated research results can effectively avoid considerable economic losses and personal safety accidents due to environmental pollution, equipment damage and halt resulted from the seal failure. So, this study is undoubtedly of great theoretical value and practical significance.

良好的密封设计需要具备密封、润滑和泵送三重功能，实现这些功能的行为均发生于密封件与对偶件之间的接触界面。动态橡胶密封服役过程接触界面在温度、润滑介质、摩擦应力的作用下，橡胶密封表面分子结构改变、颗粒脱落产生微孔、形成磨损纹理以及粗糙峰分布变化等，从而改变表面形貌特征和表面性能影响界面润滑、摩擦和磨损行为，导致密封性能衰减。本申请采用理论分析和实验测量相结合的方法，建立表征表面形貌和性能的定量描述方法以及演变规律，并分析对界面摩擦磨损行为的影响机制，明确主要磨损形式，通过建立考虑界面滑移特性的热流固耦合仿真模型，研究对动态橡胶密封性能的影响规律，提出密封失效判据，探索失效机理；并通过轴表改形和橡胶表面改性技术手段，延缓密封失效。预期研究成果可有效避免密封失效导致的环境污染、设备损坏和停机等带来的巨大经济损失以及人身安全事故，因此具有重要的理论价值和现实意义。

本项目采用理论分析和实验测量相结合的方法对构成橡胶密封的丁腈橡胶-金属界面摩擦学行为和机理进行了研究，得到不同表面形貌下稳态摩擦系数与摩擦温升、润滑条件、法向载荷和滑动速度的关系，分析了摩擦副的表面形貌、表面分子结构的变化规律。建立了基于界面滑移理论的唇封仿真计算模型，能够更精确、更可靠地预测橡胶密封的使用性能。从材料物理化学性能与摩擦磨损性能出发，研究了丁腈橡胶在使用过程中各项性能指标随着老化温度和老化时间的变化规律，提出了以交联密度为主要参数的橡胶材料老化理论。研究结果表明动态橡胶密封服役过程接触界面在温度、润滑介质、摩擦应力的作用下，橡胶密封表面分子结构改变、颗粒脱落产生微孔、形成磨损纹理以及粗糙峰分布变化等，从而改变表面形貌特征和表面性能影响界面润滑、摩擦和磨损行为，导致密封性能衰减。在此基础上，本项目以典型的旋转轴唇形密封为例，以减小摩擦力矩同时增大泵送率为优化目标，提出在轴表面设计微观织构的延寿方案，研究了橡胶表面初始形貌对界面摩擦行为的影响，为改善密封性能提供了创新的思路同时也奠定了坚实的理论基础。