胎面橡胶摩擦机理及复杂工况下轮胎力学特性研究

Tire mechanical characteristics have significant effects on the vehicle driving stability and safety. The friction between the tire and road surface is the key to study the tire characteristics. Especially when driving under complicated conditions, where the lateral and longitudinal slips are combined together, and the variation of the tire properties due to different speeds, loads, road conditions and temperatures are closely related to the friction characteristics. Therefore, this proposal is intended to study the tread rubber friction mechanism by utilizing the fractal geometry theory and contact mechanics theory, and then the theoretical and experimental research of tire mechanical characteristics under complicated driving conditions will be carried out based on the flexible carcass discrete tread modeling theory and semi-empirical modeling methods. The objective of this study is to reveal the rubber-road friction mechanism and build a practical semi-empirical tire model which not only gives consideration to both the high accuracy and efficiency, but can be also suitable for various and complex vehicle driving conditions. The main research contents of this project are listed as follows: (1) study of the rubber-road friction mechanism, considering the real rubber viscoelasticity, fractal characteristics of the road surface and the influences of different contact pressures, sliding velocities and temperatures; (2) developing a detailed theoretical tire model under complicated conditions containing the microscopic rubber-road friction characteristics, and then building the relationship between the microscopic rubber friction and the macroscopic tire friction; (3) developing a practical semi-empirical tire model considering macroscopic tire friction model on the whole tire contact patch. Three major contributions are expected in this research. The first is to reveal the essence of the tread rubber friction in the contact patch, and building a microscopic analytical friction model considering the influences of pressure, velocity and temperature, which is the necessary theoretical foundation for the further application of tire modeling. In addition, build a detailed theoretical tire model to demonstrate the expression and predictive ability of tire characteristics under the influence of complex factors. The third one is to develop a semi-empirical tire model with satisfactory accuracy and efficiency to provide a practicable method for vehicle dynamics simulation and real-time control under complicated vehicle driving conditions.

轮胎力学特性对车辆行驶稳定性和安全性有重大影响。而轮胎-路面摩擦特性是研究轮胎力学特性的关键，复杂工况下，侧偏纵滑相互耦合，不同速度、载荷、路面及温度条件下轮胎力学特性的变化都与摩擦特性密切相关。本项目拟利用分形几何与接触力学理论，研究胎面橡胶摩擦机理，结合柔性胎体离散胎面建模理论和半经验建模方法，针对复杂工况下轮胎力学特性进行理论和试验研究。重点包括：（1）表征橡胶粘弹性和硬路面分形特性，考虑压力、速度及温度影响的橡胶-路面摩擦机理；（2）考虑橡胶-路面摩擦特性的复杂工况下轮胎精细理论模型，建立微观橡胶摩擦特性与宏观轮胎摩擦特性的关系；（3）考虑接地印迹宏观摩擦特性的实用半经验轮胎模型。本研究的科学意义在于揭示轮胎印迹内胎面橡胶摩擦机理；实现复杂因素影响下轮胎力学特性的表达和预测；建立兼顾精度和效率，且适于车辆复杂行驶工况的实用半经验轮胎模型，为整车动力学仿真分析及车辆实时控制奠定基础。

轮胎力学特性对车辆行驶稳定性、平顺性以及安全性等均有重大影响。而轮胎-路面摩擦特性是研究轮胎力学特性的关键，复杂环境工况和行驶工况下，不同速度、路面及环境因素等条件下轮胎力学特性的变化都与摩擦特性密切相关。.本课题利用分形几何与接触力学等理论，研究胎面橡胶摩擦机理，并结合柔性胎体离散胎面建模理论和半经验建模方法，针对不同速度、路面等复杂工况轮胎力学特性进行相关理论和试验研究。主要研究内容和重要结果如下：.首先，研究橡胶摩擦机理，建立了胎面橡胶微观解析摩擦模型。利用橡胶变形中能量守恒以及分子的表面能相关理论，分析研究了粘性、滞后摩擦产生机理，利用Persson接触理论，建立了胎面橡胶微观解析的一般摩擦理论模型，该模型中，包括橡胶的超弹性、粘弹性、时温转换等物理参数以及路面的功率谱、分形理论等因素；然后，进行了相关试验研究与验证，该模型中各参数具有明确的物理意义，便于准确把握橡胶摩擦力学特性的宏观规律，对湿滑、冷冰路面同样具有较好的表达效果。.其次，建立了考虑微观橡胶摩擦特性和胎体弹性的复杂工况下轮胎侧偏精细理论模型。重点分析讨论印迹内复杂的胎体胎面的应力应变、滑移速度、摩擦等分布情况，及对不同速度、路面等因素下轮胎力学差异的影响。解释并剖析了几种典型复杂工况下轮胎力学特性，结果表明所建立的精细理论模型能够准确表达不同速度、路面及冰面不同温度等复杂因素对轮胎关键力学特性的影响。.最后，以理论模型为基础，建立了能够反映车辆复杂运行工况的UniTire实用半经验模型。引入等效压力分布与平均摩擦系数概念，证明了考虑一般摩擦特性的轮胎模型具有与常摩擦系数时相同的无量纲形式，从而保证了UniTire半经验模型中理论框架的正确性；推导并证明了其同样具有高阶理论边界条件。建立了考虑微观解析摩擦模型的不同复杂工况下UniTire扩展模型，并通过台架测试获取的试验数据对所建立的扩展模型进行验证，结果显示模型具有很好的表达能力和精度。