高速重载密封环热粘弹性失稳及热致损伤定量识别与评价

The problem of the thermal instability between sealing faces has gained considerable attention for floating lubricating sealing rings. These sealing rings are assembled in the high energy density transmission system of a heavy load vehicle. Predicting thermal effects and failure behavior of seals under high speed and heavy load is a key issue in order to improve the sealing stability and reliability. This research begins as the generation of local high temperature on the sealing faces, and then the thermal effect and lubrication unified model is proposed. The competition mechanism between the hydrodynamic pressure lubrication and thermal effects is built, by which can clarify the balance relationship between the oil film bearing capacity and the pressure drop caused by thermal effects. Mechanical calculation method of nonlinear viscoelastic contact for composite sealing rings is developed, which is introduced to the feedback process between the viscoelastic contact and thermal instability. On this basis, the new model and analytic technique of thermal viscoelastic instability for seals are presented. We can recognize the rules of thermal viscoelastic instability formation, transmission and evolution of composite sealing rings. Based on the above contents, the interrelated mechanism model of the thermal viscoelastic instability and wear, coupled with the time-varying surface morphology and temperature distribution, is established, and the methods of the interconnected analysis are proposed to explain the varying characteristics of local high temperature positions. Finally, the tests are conducted to verify the actual performances of the thermal viscoelastic instability and thermally induced damage. This project is aimed to solve the key problems of quantitative description of the thermal viscoelastic instability and thermally induced damage under high speed and heavy load, which can provide theoretical basis for the sophisticated design of the sealing ring with long service life.

重载车辆高能量密度传动系统中，浮动液体密封环的热失稳现象明显。为提高密封的稳定性与可靠性，必须重视密封环非稳态热效应及其失效行为。项目以密封环局部高温的形成模式为出发点，建立密封环热效应与润滑的统一模型，阐明密封润滑成膜与热效应的竞争机制，以此判断油膜承载力变化情况与热效应引起压力降的平衡关系，并发展复合材料密封环粘弹性非线性接触的力学计算方法，引入到粘弹性接触与热失稳的反馈过程中，由此提出密封环热粘弹性失稳的理论模型与求解模式，掌握复合材料密封环热粘弹性失稳的形成、传播与演变规律。在此基础上，考察热失稳与热损伤相互作用机制，耦合时变的接触形貌和温度分布，提出密封热致损伤与热失稳的关联计算方法，并解释局部高温位置的时变特征。最后完成密封环热失稳与热损伤的台架试验验证。本项目旨在解决高速重载密封环热失稳及其热致损伤的定量化描述和科学评价的关键问题，为高服役寿命密封环的精良设计提供理论依据。

车辆传动系统密封环性能影响传动系统的动力性和稳定性，是评价总体传动性能的一个重要指标。在大功率密度的传动工况下，密封热失稳现象凸显，为提高密封的稳定性与可靠性，必须重视密封环局部高温生成的定性构建与定量描述的问题。项目首先考察了密封环局部高温热带形成与性能影响因素，基于伽辽金有限元算法，构建了密封系统的热传导、热流密度、温度场扰动等非均匀特性的物理模型，及其各物理场之间的耦合关系，将密封环局部高温热带的热不稳定问题转化为矩阵行列式，自主编程并进行求解，可以获得在不同的摩擦条件下，发生局部高温热带的临界速度值。定量表达了弹性模量、导热系数、热膨胀系数和密封环尺寸对局部高温热带发生的影响。在上述内容的基础上，根据密封材料的使用特点，建立了密封环局部高温热点的热失稳分析模型，耦合热流体、摩擦热的变化，提出了密封环局部高温热点的热失稳生成模式与模拟技术，分析密封材料参数、密封尺寸等对发生密封环局部高温热点临界速度的影响。再次，研究分析了密封环热失稳与热致磨损相互影响机制，建立了磨损模型并联合热-结构耦合计算，更新表面几何形状以反映给定时间内的磨损程度。在循环反复过程中观察局部高温热带的变化规律。在复杂的磨损状态下，热带会呈现更加复杂的变化，如热带的分裂和合并，模拟了密封环从局部材料热损伤到整体磨损破坏的服役规律。最后，利用自主设计的密封环综合性能试验台开展了车辆传动系统密封性能试验，提出了密封环热失稳试验方法。进行了热失稳的试验及其验证，选取不同材料的密封环为试验对象，观察试验中密封环温度的扰动情况，获取不同工况参数下密封热失稳的变化情况，以及密封磨损规律。项目实现对真实工况下密封热效应发生、发展与失效表现的有效预测，揭示了高速重载密封环服役性能形成与演变规律，获得了高能量密度密封环的关键技术原型，为车辆传动系统的高服役寿命密封环的精良设计提供理论支撑。