基于波纹状变形发生与演化的制动器摩擦热斑机理研究

This project aims at the critical frictional hot spot that seriously effects the service effectiveness of vehicle brakes, and selects the disc waviness distortion accompanying frictional hot spot as the clue and study point, and proposes a new idea to investigate into the mechanism of frictional hot spot from the occurrence and evolution of disc waviness distortion..The way to apply the mechanical load and thermal load is chosen as the breakthrough, and the actual friction load is equivalent to three levels of loading form, including the irregular disc with thermal loading, the mechanical and thermal loads combining but not coupling, and the mechanical and thermal loads coupling. Under these conditions, the experiments and analysis of disc waviness distortion will conduct by using the mechanical loading device, the oxyacetylene thermal loading device, and the friction loading device with adjustable contact area and pressure. The dynamic models of disc waviness distortion will be established by using the modeling methods of moving load, thermal buckling, and thermo-mechanical coupling and so on. The evolution characteristics of disc waviness distortion will be discussed and verified by the test results. Then the influence law of initial geometric feature and initial stress and strain, loading form and braking operation parameters will be studied in detail..It is expected to find out the mechanism and the key factors interaction of disc waviness distortion induced by friction load, as well as its internal relationship with the brake friction hot spot. The nonlinear dynamic theory of brake disc under complex mechanical and thermal loads is also expected to be established. The research achievement will provide theoretical support for revealing the mechanism of brake frictional hot spot.

本项目针对严重影响汽车制动器服役效能的摩擦热斑问题，以制动盘摩擦热斑并存的波纹状变形为线索和切入点，提出从波纹状变形发生与演化过程揭示摩擦热斑机理的新思路。. 以机械载荷与热载荷的施加方式与作用形式为突破口，将实际摩擦载荷等效为不规则制动盘加载热载荷、机械与热载荷联合且不耦合、机械与热载荷耦合3个层次，综合利用独立机械载荷、氧乙炔热载荷、接触面积与压力可调的摩擦载荷等加载装置，开展制动盘波纹状变形试验与分析；借鉴移动载荷、热屈曲和热机耦合等建模方法，建立摩擦载荷下制动盘波纹状变形动力学模型，分析波纹状变形演化特性，研究初始几何特征和应力/应变、载荷作用形式、工况参数的影响规律。. 期望探明摩擦载荷诱发的制动盘波纹状变形发生机理、关键因素作用机制及其与摩擦热斑的内在联系，建立复杂机械与热载荷作用下制动盘非线性动力学理论体系，为揭示制动器摩擦热斑机理提供理论支撑。

制动器摩擦热点是业界公认的汽车制动器难点问题，但是制动器摩擦热点的产生机理尚不清晰。本课题采用载荷分离→载荷综合的新思路，从制动盘波纹状变形与摩擦热斑的关系出发，以机械载荷与热载荷的施加方式与作用形式为突破口，揭示制动盘波纹状变形与热点的发生机理。. 在试验研究方面，开展了热载荷作用下不规则制动盘特性试验、机械与热载荷联合及耦合作用下制动盘特性试验，发现具有初始端面跳动或厚薄差的制动盘，在热载荷作用下会发生4阶波纹状变形，未出现热点现象，说明初始端面跳动或厚薄差对制动盘变形具有重要作用。但是，在热与机械载荷联合作用下，制动盘的变形模式改变为5阶波纹状变形，同时盘面出现了热点，说明热点是通过盘面变形与摩擦作用联合作用产生的。在热与机械载荷耦合作用下，会产生明显的机械挤压与热变形两种变形，制动盘通风槽结构对热点数量和分布具有重要的影响。. 在理论与仿真分析方面，建立了基于弧长法的不规则制动盘非线性热屈曲模型、基于移动载荷法的制动盘机械-热-结构非线性耦合仿真模型、制动盘机械-热-结构线性瞬态耦合仿真模型，发现初始端面跳动是制动盘非线性热屈曲的重要因素，可以使制动盘5阶波纹状变形变为4阶波纹状变形；机械载荷的介入，又可以使4阶的波纹状变形变为5阶变形模式，进而综合分析了热点的发生机理。. 在关键因素研究方面，研究了初始端面跳动、载荷非对称性、摩擦块与制动盘初始间距等因素的影响规律，发现初始变形的阶次对热载荷作用下制动盘波纹状变形阶次具有决定作用，初始变形幅值越大制动盘屈曲的临界温度越低，热载荷径向非对称越强制动盘越容易出现波纹状变形，转速越高、摩擦块与制动盘初始间距越小制动盘越容易出现热点。. 本项目发表SCI/EI论文7篇，授权发明专利2项，获得2019年上海市科技进步一等奖1项，研究了制动器热点发生过程中的摩擦系统耦合动力学行为，是摩擦学领域前沿学术问题，项目成果在我国汽车行业内得到推广应用。