鼓式制动器摩擦尖叫的复模态模型与影响因素研究

针对某型号鼓式制动器,应用ABAQUS软件建立了摩擦尖叫有限元模型,通过零部件自由模态试验和制动尖叫台架试验验证了模型的正确性。在此基础上,进行了制动蹄摩擦衬片弹性模量、制动压力和摩擦系数对摩擦尖叫倾向性的影响分析;引入制动鼓与制动蹄间的接触压力分布特性,结合复模态理论,探索了前述因素对摩擦尖叫的影响的内在机制。     

鼓式制动器动态应变和温度特性试验研究与分析

鼓式制动器的工作过程存在着强烈的摩擦学-传热学-机械学耦合行为,其动态受载状态研究是分析制动器制动特性、进行疲劳寿命评估和结构优化设计的重要基础。该文以某重型卡车的鼓式制动器动态特性为研究对象,设计试验获得了两种制动工况下制动鼓外表面的动态应变和摩擦表面的温度变化,并采用有限元软件ABAQUS进行了考虑磨损的热机耦合仿真分析。结果表明,制动鼓局部与制动蹄不同位置接触时应变呈现极度不均匀的特征,且相似的一组四个波峰在随制动鼓的旋转重复出现。随着温度升高,热应变对制动鼓的平均应变状态影响显著。     

摩擦衬片包角对盘式制动器尖叫影响的仿真分析

摩擦衬片包角对制动尖叫具有重要影响。针对某通风盘式制动器,建立有限元复模态模型并通过尖叫台架试验进行了正确性验证。基于该模型针对5种包角水平的摩擦衬片,通过仿真计算分析其对制动尖叫倾向性的影响,并从制动块自由模态特性、盘块间接触压力分布、不稳定模态频率及模态耦合特性角度解释了不同摩擦衬片包角对制动尖叫的影响机制。分析表明：摩擦衬片包角的改变会同时引起制动块结构特性变化和接触压力分布的变化,进而引起不稳定模态数量、频率和模态耦合特性的改变。     

基于Kriging代理模型鼓式制动器稳定性的优化设计

针对鼓式制动器出现的制动噪声问题,引入Kriging代理模型,对鼓式制动器稳定性进行优化设计。采用最优拉丁超立方设计(optimal Latin hypercube design, Opt LHD)生成样本点数据,代入鼓式制动器有限元模型进行求解,生成Kriging代理模型和进行代理模型的精度检验。以摩擦衬片、制动鼓和制动蹄的杨氏模量为设计变量,以加权不稳定倾向系数为目标函数,建立了鼓式制动器稳定性的优化设计数学模型。采用多岛遗传算法(multi-island genetic algorithm, MIGA)进行优化设计。结果表明:引入Kriging代理模型可以大大提高鼓式制动器稳定性优化的求解效率;通过优化设计能够提高鼓式制动器的稳定性,抑制制动噪声。     

基于台架NVH试验环境的制动器虚拟样机分析

针对NVH台架试验时某汽车鼓式制动器产生的制动抖动现象,在ADAMS软件中建立该鼓式制动器各部件模型、边界和载荷条件,以及NVH实验台相关模型,得到包含试验环境的虚拟样机模型。仿真分析拖滞制动工况时低频振动的激励源和传递特性。结果表明:制动抖动现象是因为摩擦衬片各部位和制动鼓接触不同步所致的低频振动,与制动压力和转速等因素有关;悬架的螺旋弹簧下端振动最大,减振器和衬套都起到了对振动衰减的作用。     

盘式制动器制动尖叫热机耦合特性仿真分析

利用试验和仿真相结合的方法,对某车型前通风盘式制动器进行研究。基于多功能制动器动力学试验台架,分别对两套同型号制动器试件进行制动尖叫试验,基于有限元建立制动器热机耦合分析模型,在拖滞制动模式下进行仿真计算。分析研究表明,拖滞制动模式是一个明显的热机耦合过程,其热机耦合效应与减速制动模式具有很多共同点。热机耦合效应对制动尖叫影响较大,考虑热机耦合效应有利于提高尖叫预测精度,并能够反映制动尖叫的时变特性。     

复模态分析在盘式制动器制动异响抑制上的应用

为解决某SUV车型在行驶过程中盘式制动器产生的制动异响问题,采用行业界内主流的复模态分析方法,利用Abaqus计算制动器系统的复特征值分布,通过对比分析不稳定模态下子结构的模态振型与其本身的模态振型间的关系,揭示系统不稳定模态是由于各子结构模态耦合振型叠加而导致的,结合SAE J2521试验结果及路试实际情况对比发现,仿真分析能够较为准确地预测出系统产生制动异响的趋势,且不稳定系数是否大于0.01不是作为评判系统稳定与否的唯一标准。结合实际工程经验提出一种"不对称倒角"结构对摩擦片的形状进行优化,试验结果显示这种特殊结构能够有效地抑制制动异响,有效地解决了实际工程问题,为制动异响问题的解决提供了另一条途径。     

基于复特征值分析的某盘式制动器制动尖叫问题改进

以某车型出现2000 Hz制动尖叫问题的盘式制动器为研究对象,建立制动器的有限元模型。通过试验模态对有限元模型进行修正,应用复特征值分析技术,获取系统的复特征值和振型,并通过ODS测试确认与制动尖叫频率对应的不稳定模态。然后针对此不稳定模态,通过相关性分析量化制动器零件对系统不稳定模态的贡献,采用优化具有最大贡献量的零件几何结构来改善制动尖叫。最后通过SAE J2521台架试验验证此方法可行。     

消声片对汽车盘式制动器摩擦尖叫特性影响研究

建立某车型浮钳式盘式制动器有限元模型,通过有限元软件ABAQUS中的复特征值分析法,对比分析有/无消声片状态下制动系统的稳定性,探讨通过消声片改善制动摩擦尖叫的作用机理,并对消声片结构与制动摩擦尖叫之间的关系进行研究。结果表明,制动器的不稳定振动模态主要表现为制动盘的面外模态,同时伴随有制动卡钳、保持架以及摩擦片等的弯曲与扭转运动,制动尖叫噪声具有多频耦合的特性。在制动器中引入具有特定结构与材料形式的消声片能够有效降低系统的尖叫倾向和强度,尤其是在抑制低频尖叫方面效果显著。消声片基板存在一个最佳厚度值（0.5 mm）,使得减振降噪的效果达到最佳,过度增大或减小消声片基板厚度可能导致降噪效果减弱,使尖叫强度开始上升。对消声片表面进行开沟槽处理能够改变制动力的传递特性,使得制动界面接触应力分布更加均匀,界面能量堆积现象被削弱,从而改善制动系统的稳定性。以上分析结果对认识消声片的减振降噪特性以及其结构优化设计具有一定的工程指导意义。     

基于模态频率特征的浮钳盘式制动器盘块间法向接触刚度辨识方法

盘式制动器广泛应用于交通工具和工业装备,在制动过程中出现的摩擦振动噪声和制动盘与制动块之间的接触摩擦作用有密切关系。由于受到多种因素影响,建立准确的制动器关键零件接触关系仍是当前制动器振动噪声研究的难点。基于接触刚度能够影响系统刚度从而改变制动盘模态频率的动力学特性,针对乘用车浮钳盘式制动器,提出一种基于模态频率特征的制动器盘块间法向接触刚度辨识方法。应用锤击模态试验测得不同制动压力条件下制动盘各模态的频率特征;基于ABAQUS软件建立约束条件下制动盘与制动块装配体的有限元模型,在1~10 kHz范围内对该模型进行前7阶面外模态频率分析,辨识得到制动盘与制动块之间的法向接触刚度,并对接触刚度变化原因进行了分析。结果表明,随着制动压力的增加,由于制动块摩擦材料的孔隙度减小,接触刚度增大;随着制动盘模态阶次的提高,由于制动盘与制动块在谐振状态时其接触面积发生变化,接触刚度会先增大然后基本保持不变。该方法可用于建立准确的制动器盘块间接触关系,以开展制动器振动噪声仿真分析,能够提高计算精度,保证分析结果的可靠性。     

Thermomechanical Behavior of Brake Drums Under Extreme Braking Conditions

Braking efficiency is characterized by reduced braking time and distance, and therefore passenger safety depends on the design of the braking system. During the braking of a vehicle, the braking system must dissipate the kinetic energy by transforming it into heat energy. A too high temperature can lead to an almost total loss of braking efficiency. An excessive rise in brake temperature can also cause surface cracks extending to the outside edge of the drum friction surface. Heat transfer and temperature gradient, not to forget the vehicle's travel environment (high speed, heavy load, and steeply sloping road conditions), must thus be the essential criteria for any brake system design. The aim of the present investigation is to analyze the thermal behavior of different brake drum designs during the single emergency braking of a heavy-duty vehicle on a steeply sloping road. The calculation of the temperature field is performed in transient mode using a three-dimensional finite element model assuming a constant coefficient of friction. In this study, the influence of geometrical brake drum configurations on the thermal behavior of brake drums with two different materials in grey cast iron FG200 and aluminum alloy 356.0 reinforced with silicon carbide (SiC) particles is analyzed under extreme vehicle braking conditions. The numerical simulation results obtained using FE software ANSYS are qualitatively compared with the results already published in the literature.     

超深矿井提升机制动盘热性能分析与优化

超深矿井提升机制动盘在紧急制动过程中由于受到摩擦循环热载荷的作用，内部产生较大的热应力，同时高温会导致制动盘和闸片摩擦制动性能下降甚至失效。针对制动盘制动热性能问题，根据热传导理论和有限元分析方法，建立了制动盘组件三维有限元模型，采取直接耦合方法对制动盘制动过程中的热应力场进行模拟研究，并通过实验验证了仿真参数设置的正确性。分析了闸片数量和排布方式对制动工况下制动盘温度和应力分布的影响。结果表明，在制动阶段，制动盘摩擦面温度先急剧上升，后缓慢下降，摩擦面温度呈现锯齿状波动性变化，制动过程中应力变化规律与温度变化规律相同。原制动盘在制动过程中的最高温度为134.8℃，最大应力为230.2 MPa，高温和大应力区域集中于摩擦面附近；增加闸片数量的制动盘最高温度为142.4℃，最大应力为251.1 MPa，高温和大应力区域同样集中于摩擦面附近；改变闸片排布方式的制动盘最高温度为86.5℃，最大应力为119.1 MPa，高温区域和大应力区域范围较小。由此可知，改变闸片排布方式更能显著降低制动盘温度和应力，并且温度场和应力场分布更均匀。研究结果可为制动盘热性能优化设计提供理论参考。     

湿热环境对碳纳米管复合材料界面应力传递的影响

基于碳纳米管的热膨胀系数及弹性模量分别为温度变化的函数,基体的热、湿膨胀系数及弹性模量分别为温度变化和湿度变化的函数,应用连续介质力学的经典弹性壳理论及传统纤维拉拔模型,分析了湿热环境对碳纳米管复合材料界面应力传递的影响。数值计算表明,湿度、温度的效应及碳纳米管的层数等参数对界面应力的传递均有显著影响。     

Analyzing the mechanisms of thermal fatigue and phase change of steel used in brake discs

Thermal cracks on the friction surface of railway brake discs can develop during their lifespan. Cracks often initiate after severe braking conditions along with the occurrence of hot spots. The cyclic thermal and mechanical loads causes high temperature, plastic strain and even phase change of the brake disc steel. In this paper, full scale emergency braking tests were conducted and the peak temperature of localized area was found exceeding the austenitizing temperature of the steel. Thermal cyclic tests was performed to simulate the temperature variation during braking. Volume change of the steel caused by microstructure transformation was taken into consideration in numerical simulation. Combining with the fracture behavior of brake disc steel in low cycle fatigue (LCF) tests in different temperature level, the simulation results show a good consistency with the results of microstructure observation and crack initiation. The occurrence of embedded crack could be well explained according to the simulation results and low cycle fatigue test results.     

Thermal seizures in automotive drum brakes

In automotive industry, drum brake system is used on two types of wheels: cast and spoke. Brake drum, brake panel and brake drum liner are important components of the brake system. Failures of these components observed during high-g braking on spoke wheels of a motorcycle are reported and systematically analyzed in this paper. The brake drum and the panel were found to have seized during high speed brake applications. Excessive wear on the drum liner made of cast iron was also observed. Metallurgical analysis (chemical analysis, hardness test and microstructure analysis) of the liner revealed that excessive wear on the liner was not due to any change in material properties. Hence, further steps were taken to investigate the problem. An experimental testing methodology was developed to simulate these failures. For the same material, testing conditions, and design specifications of cast and spoke wheels, no failure was observed in the cast wheels. This unusual failure was further investigated using three-dimensional steady state finite element analysis (FEA) of both cast and spoke wheels. The methodology adopted for determining the thermal and structural boundary conditions have been described in detail. Energy balance methodology was employed to determine the heat flux values on the drum liner. The structural boundary conditions are determined experimentally and validated with FEA. The predicted temperature from FEA for cast and spoke wheels compares reasonably well with the experiments. It was found that the failure of the brake system in the spoke wheels was due to excessive thermal expansion of the brake panel and the drum beyond the specified limit. An optimum range of labyrinth clearance between the brake drum and the brake panel was recommended for the brake system of cast and spoke wheels.     

A reliability-based robust optimization design for the drum brake using adaptive Kriging surrogate model

To decrease random parameters’ influence on the drum brake reliability, the reliability-based robust optimization design (RBROD) of the electric vehicle brake is proposed. Based on the assumption that the maximum temperature of the brake cannot exceed the allowable temperature, a performance function model of thermal–mechanical coupling reliability of drum brakes is established by the adaptive Kriging method, and the analysis of reliability sensitivity and RBROD are conducted. The accuracy of the proposed model is verified by temperature measurement experiment under emergency braking condition. The robust optimization design improves the drum brake reliability to 0.99998 and reduce the influence of the design parameters on the reliability, with the absolute values of the reliability sensitivity and the weight of the drum brake are significantly smaller. Therefore, the objectives of reliability design, robustness design, and optimization design are simultaneously achieved by the proposed methods. Besides, the relative error of the proposed method is 0.373%, the number of function evaluations is 39, and the comparison with four meta-model methods show that the proposed method holds high-accuracy and high-efficiency. This study provides a high-precision theoretical explanation for the robust optimization design of drum brake.     

制动工况参数对制动盘摩擦温度场分布的影响

车用盘式制动器是车辆中的重要零件。在紧急制动过程中,制动压力、整车参数以及轮胎与路面间附着系数之间的关系对制动器摩擦温度场分布有重要的影响。通过有限元仿真,探讨不同制动工况参数对瞬时温度场分布的影响。结果表明：如果忽略制动过程中摩擦热流强度的变化,会给温度场模拟带来较大的偏差。制动初始动能和摩擦力增长过程是影响盘表面温度场的关键因素。     

飞机刹车用长寿命高摩擦特性炭/炭复合材料制备技术(英文)

以针刺炭纤维准三向结构整体毡为预制体,经丙烯气体狭缝定向流的"外热内冷"、"内热外冷"径向热梯度CVI工艺致密技术,优化组合的热解炭/树脂炭双元炭基体技术,通过调控高温处理技术等三大关键技术制备了A320系列飞机炭刹车盘材料。与现用的A320系列飞机进口炭刹车盘进行了地面台架对比试验和装机应用。结果表明:自主开发的炭刹车盘其设计着陆能量和超载着陆能量的摩擦特性与国外相当,但在高能载(RTO)刹车时,其摩擦系数提高了21%～48%,静摩擦系数提高了28%;装机应用寿命平均达到2700次以上,比国外产品寿命提高了23%,凸现出长使用寿命和高摩擦特性的特色。     

Effects of metal coating on the fiber Bragg grating temperature sensing characteristics

Effects of the metal coatings on the fiber Bragg grating (FBG) temperature sensing characteristics were simulated and experimentally investigated. Temperature sensitivity of the coated FBG as a function of the coating material properties was simulated using MATLAB software based on the temperature sensing model. The simulation results show that the elastic modulus, Poisson’s ratio, thermal expansion coefficient and coating thickness of the coatings have noticeable impacts on the sensing characteristics of the coated FBG. It is noted that (i) there is an extreme value for the influence of the elastic modulus on temperature sensitivity; (ii) temperature sensitivity increases with the increase of Poisson’s ratio and thermal expansion coefficient; (iii) with the increase of the coating thickness, the temperature sensitivity increases first then reaches a plateau asymptotically. To validate the simulation results, several FBGs were coated with copper, nickel, cobalt, copper–zinc, and Ni–ZrO₂, and subsequently the associated temperature sensitivities were measured using a network analyzer as well as a water bath. The results show that the simulation results agree well with that of the experiments, with the errors up to 5.49%.