Brake pad taper wear on brake moan noise

Automotive brake systems today have many factors that can contribute to brake noise. Modern approaches to reduce the propensity of brake noise mostly target high frequency brake squeal. A more difficult constituent of brake noise to address is low frequency moan, which is typically caused when the brake system excites a suspension member with a constrained natural frequency in the range of excitation. Although most modern CAE techniques utilized to diagnose and solve brake noise issues focus on new brake pad condition, this paper will show the benefit of understanding a common wear mechanism “Taper Wear,?and attempt to correlate its effects on brake moan. In order to study this phenomenon, a finite element model of a disc brake is established, and a complex eigenvalue analysis (CEA) of the brake system is performed. The propensity of brake moan noise is evaluated on basis of damping ratio of a dynamic brake system model. By using the finite element model, effects of the brake pad taper wear on brake moan noise is studied. The results show that the brake pad taper wear is a significant factor for generating the instability causing the brake moan noise. The study is performed at various levels of brake pad taper wear. When the brake pad taper wear is more than 0.5 mm, the value of negative damping ratio rapidly increases, and the propensity of brake moan noise is greatly magnified. In this study, the simulation result correlated well with the test result, which provides the theory and guidance for brake moan noise control.     

Vibration path analysis and optimal design of the suspension for brake judder reduction

Brake judder is abnormal vibration, which is mainly generated by uneven contact between the brake disc and pad. The abnormal vibration from BTV (Brake Torque Variation) is transferred to the suspension and the steering system during braking. In this paper, judder simulation is carried out using a multi-body dynamic analysis program to analyze the relationship between judder and the transfer mechanism, which consists of the suspension and the steering system. In order to verify the analytical model, test results are compared with the simulation results. A sensitivity analysis is also carried out. In addition, an optimization method is presented for judder reduction, using the design of experiments.     

Model-based analysis of the mechanical subsystem of an air brake system

Most commercial vehicles such as buses and trucks use an air brake system, often equipped with an S-cam drum brake, to reduce their speed and/or to stop. With a drum brake system, the clearance between the brake shoe/pad and the brake drum may increase because of various reasons such as wearing of the brake shoe and/or brake drum and drum expansion caused by high heat generation during the braking process. Hence, to ensure proper functioning of the brake system, it is essential that the clearance between the brake shoe and the brake drum is monitored. In this paper, we present a mathematical model for the mechanical subsystem of the air brake system that can be used to monitor this clearance. This mathematical model correlates the push rod stroke transients and the brake chamber pressure transients. A kinematic analysis and a dynamic analysis of the mechanical subsystem of the air brake system were performed, and the results are corroborated with experimental data.     

Investigation of influential factors of a brake corner system to reduce brake torque variation

This paper investigates the brake corner system to reduce brake torque variation in the brake judder problem. A numerical model for determining brake torque variation was constructed using the multi-body dynamics model. Using this model, the brake torque variation for a given disc thickness variation was obtained in the time domain. The multi-body dynamics model was verified by a dynamometer test via the comparison of brake torque variation and load distribution patterns of the pad. To reduce the simulation time and cost required to determine factors that influence the reduction in brake torque variation, a simple mathematical model was constructed and used to determine both the brake torque variation and influential factors. The multi-body dynamics model and dynamometer test were modified on the basis of the results of the simple mathematical model and deformed shape of the multi-body dynamics model. These influential factors were verified to reduce the brake torque variation.     

Hot judder simulation of a ventilated disc and design of an improved disc using sensitivity analysis

In a disc brake system, thermal expansion of the material is caused by friction energy that is generated by the sliding contact between a disc and pad during braking. This phenomenon, thermo-elastic instability, can lead to hot spots on the disc surface and a hot judder phenomenon. Transient finite element analysis has been used to simulate this phenomenon. Three dimensional finite element models of a disc, pad, and cylinder were created. Each part was connected by a joint. Contact condition was applied to the disc and pad with a friction coefficient (μ) of 0.4. A convective heat transfer coefficient was set as 40 W/m²K. Using a commercial program SAMCEF, the simulation of the thermo-mechanically coupled system was performed. In order to find the sensitive parameters of brake judder, sensitivity analysis was carried out with consideration for disc design parameters. As a result, the hot spot phenomenon was confirmed and hot judder was predicted. Moreover, the more sensitive parameters of the hot judder phenomenon were presented. Finally, an improved disc model and an analysis technique were verified by comparison to dynamo test results.     

Analysis of automotive disc brake squeal considering damping and design modifications for pads and a disc

The squeal noise occurring from the disc brakes of passenger cars has been analyzed by using the complex eigenvalue method numerically. The contact between a disc and two pads was analytically modeled as many linear springs and dampers in an effort to develop the improved equation of motion derived on the basis of Lagrange’s equation and the assumed mode method. The finite element modal analysis results for disc brake components constitute an eigenvalue matrix in the analytical equation of motion. The complex eigenvalue analyses based on the equations of motion are able to examine the dynamic instability of a brake system, which is an onset of squeal, by considering the disc rotational effect. Numerical analyses showed that the modes unstable in an undamped analysis became stable in a damped case, which illustrates the important effect of damping on the squeal instability in a brake squeal simulation. Then several modified brake models were suggested and investigated how effectively they suppressed the occurrence of squeal noise. The brake parts such as a pad chamfer and a disc vane were modified and the influence of pad chamfer and vane shapes on squeal occurrence was proved to be significant. The numerical results showed that proper structural modification of a disc brake system can suppress the brake squeal to some extent.     

载重子午轮胎与路面相互作用的分析

根据全钢载重子午线轮胎12.00R20的实际结构,考虑轮胎的几何非线性、材料非线性、接触非线性以及大变形等力学特性,应用有限元的方法建立轮胎的三维模型,橡胶材料采用Yeoh模型,橡胶-帘线复合材料采用加强筋模型,并通过轮胎径向刚度的测试验证了模型的有效性.在数值模拟中分析了轮胎在一定充气压力时,在不同垂直载荷和牵引速度的作用下,与地面在接触区域的变形情况、应力分布、摩擦应力分布等滚动接触规律.结果表明,轮胎与地面接触应力分布存在明显的非均匀性,轮胎的接地面积和地面总反力随着滚动速度的升高而增大.     

缸套-活塞环三维润滑状态模拟分析

以发动机缸套-活塞环摩擦副为对象,研究润滑表面粗糙度、润滑油的变黏度效应以及气缸套圆周方向的形变等因素对润滑状态的影响。运用三维瞬态平均Reynolds方程与微凸体接触模型,建立缸套-活塞环三维瞬态动压润滑模型,并使用Fortran语言编制了润滑状态计算程序,得出行程内的最小油膜厚度、压力分布、摩擦力等曲线。结合实际工况对计算结果进行分析,表明在活塞环圆周方向上的油膜压力及油膜厚度分布都是不均匀的,有明显变化;在压缩冲程上止点附近,微凸体摩擦力数倍于流体摩擦力,是引起摩擦磨损的主要原因。     

非均布轮载下钢桥面铺装力学响应分析

为了对非均布轮栽作用于不同钢桥面系的效应进行预估,在构造理想传力垫层建立三维有限元接触分析模型的基础上,计算了均匀分布、凸形分布、凹形分布3种荷栽分布下铺装层的力学响应。计算分析表明,构造传力垫层加栽的接触分析方法是分析正交异性桥面系作用复杂荷栽模式的一种有效方法,特别是当要考虑多种复杂荷栽模式、多个作用位置时。不同荷栽下铺装层力学响应的对比显示：3种荷栽模式下横向拉应变沿横断面的分布规律相当一致,但凸形分布的计算结果最大、均匀分布次之、凹形分布的计算结果最小;轴载一定时,高胎压轮胎服从凸形分布,所以高压轮胎对铺装层有更大的破坏作用。     

Development of aluminum metal matrix composites (Al-MMC) brake rotor and pad

Improvement in fuel consumption rate requires a reduction in vehicle weight. Research and development for materials substitution in the brake rotor, from the conventional cast iron to aluminum, has been undertaken. In this study, we developed aluminum metal matrix composites brake rotor and pads, which have equivalent braking effects and wear resistance to those of the conventional cast iron rotor, by optimization of the quantities and the particle diameter ratio of hard particles used for the rotor and the pad.     

基于典型道路谱的汽车制动摩擦片寿命预测

文章基于能量磨损机理提出了一种汽车制动摩擦片磨损寿命预测的方法,对车辆制动安全性以及摩擦材料利用率的提升具有一定的现实意义。以车辆制动系统中的摩擦片为研究对象,在制动盘冷却试验基础上建立制动摩擦副热力学模型,旨在探明不同工况下摩擦副热力学特征的变化规律。根据能量磨损机理研究制动温度对材料磨损量的影响关系,结合温度分布特征与摩擦材料磨损率提出摩擦片磨损量的评价标准,建立制动摩擦片的磨损寿命预测模型。基于典型公路道路试验路谱的动力学参数进行摩擦片磨损寿命预测,与试验结果相比其磨损寿命预测具有较好的一致性,为汽车制动系统参数设计及制动摩擦材料寿命研究提供了指导依据。     

基于ANSYS/LS-DYNA的鼓式制动器接触仿真分析

利用显式动力分析软件ANSYS/LS-DYNA,进行瞬态动力学仿真分析,模拟制动器在制动过程中接触摩擦情况与接触应力的分布以及制动过程中制动鼓的变形和速度的变化情况。     

山区高速公路坡面荷载的动态效应与实测研究

为了获取公路陡坡路段荷载对路面结构的动态效应,为理论计算分析和试验分析提供可靠的参数,利用自主开发的轮胎对地压力动态分布实时测量装置,进行了不同车型、不同载重、不同车速和不同纵坡条件下坡面轮胎接地压力的动态测量,得出了不同速度下坡面轮胎接地压力的分布及其变化规律。结果表明,高速运动状态下,重载货车轮胎接地形状近似于矩形,车速越高接地形状接近矩形的相似程度愈高;随着车速提高,接地压力的分布形式从凸起型分布逐渐向鞍型分布演变,接地压力峰值逐渐减小;运动状态下,车辆轮胎接地压力在行进方向上呈半正弦波分布,在横向上表现为非均匀分布。     

A two-dimensional tire model on uneven roads for vehicle dynamic simulation1

This study proposes a comprehensive analytical tire model for handling and ride comfort in low frequency ranges. A contact algorithm that is developed in this study provides a two-dimensional contact pressure distribution on even and uneven road surfaces with reasonable computational cost. Shear stresses and strains during cornering and braking are estimated by direct measurement of tread deformations. The model is validated against experimental force and moment data for general handling simulations. Cleat tests are also conducted and validated under different forward velocity and vertical load conditions for a tire vibration study.     

盘式制动器制动尖叫的有限元分析与试验

建立了产生制动尖叫的钳盘式制动器各主要零件的有限元模型,并通过集成构建了制动器总成的接触摩擦耦合有限元模型,计算了制动器振动系统的复特征值分布和模态,分析了可能产生制动尖叫的不稳定模态,并与制动噪声台架试验统计结果进行了对比,结果表明所建模型能够较好地预测出制动器发生制动尖叫的倾向;分析了各零件的振动模态对产生制动尖叫不稳定模态的贡献大小,揭示出有尖叫倾向的不稳定模态是由子结构未耦合时的多阶振动模态叠加而成;分析讨论了摩擦因数、摩擦片结构及其背板阻尼对制动尖叫的影响,为控制制动尖叫提供了途径。     

Measurement of the disc-pad friction coefficient for mechanical brakes using direct and indirect methods

It is necessary to guarantee the proper brake force to stop a train safely in a limited distance and o adjust its speed. Currently, most trains are run by electrical power and have a combined electrical and mechanical (friction) braking system. The mechanical brake force is determined by many parameters, such as the friction coefficient of the brake disc and pad, the pressure in the brake cylinder, the brake cylinder’s cross sectional area and the brake linkage ratio. In general, the friction coefficient data of the brake disc and pad have been taken through a dynamo-test in a laboratory, but these data might not be well matched with real data under operating conditions because of the difference in data acquisition conditions. The present study examined two methodologies that can measure the friction coefficient of the brake pad and disc based on a train’s real operating conditions. The first method was the direct method, which measured the brake force and clamping force applied on the mechanical brake by using strain gauges installed on the brake to calculate the friction coefficient. The second was an indirect method that obtained the friction coefficient by using the weight of the train and the equivalent brake force. Those variables were calculated from the longitudinal dynamic characteristics, such as resistance to motion, gradient resistance and curved resistance. These two methodologies were used to obtain the disc-pad friction coefficient for the mechanical brakes of a Korean high-speed train (HSR350x).     

某型轿车盘式制动器制动噪声的控制

对某型轿车盘式制动器进行了台架试验,发现该制动器主要制动噪声频率在3kHz附近。采用有限元FEA分析手段对制动盘、制动钳壳体、制动钳支架和摩擦片进行了振动特性分析。结果表明,制动钳支架的7阶振动模态是导致制动噪声产生的原因之一。对制动钳支架结构设计进行了改进,并对装有改进后制动钳支架的盘式制动器进行了台架试验。结果表明,制动器冷态制动噪声从100.5 dB下降为73.4 dB,达到了该车型对制动器噪声的限值要求。     

A novel fuzzy logic correctional algorithm for traction control systems on uneven low-friction road conditions

The traction control system (TCS) might prevent excessive skid of the driving wheels so as to enhance the driving performance and direction stability of the vehicle. But if driven on an uneven low-friction road, the vehicle body often vibrates severely due to the drastic fluctuations of driving wheels, and then the vehicle comfort might be reduced greatly. The vibrations could be hardly removed with traditional drive-slip control logic of the TCS. In this paper, a novel fuzzy logic controller has been brought forward, in which the vibration signals of the driving wheels are adopted as new controlled variables, and then the engine torque and the active brake pressure might be coordinately re-adjusted besides the basic logic of a traditional TCS. In the proposed controller, an adjustable engine torque and pressure compensation loop are adopted to constrain the drastic vehicle vibration. Thus, the wheel driving slips and the vibration degrees might be adjusted synchronously and effectively. The simulation results and the real vehicle tests validated that the proposed algorithm is effective and adaptable for a complicated uneven low-friction road.     

Model-based control of an electropneumatic brake system for commercial vehicles

A properly functioning brake system is critical for ensuring the safe operation of any vehicle on roadways. Commercial vehicles such as trucks, tractors-trailers and buses are equipped with an air brake system that uses compressed air as the energy transmitting medium. This paper presents a model-based control scheme for an electropneumatic brake system for use in commercial vehicles. A mathematical model for an electropneumatic brake system was developed and corroborated with experimental data. A control scheme was developed based on this model and was used to regulate the pressure of air inside the brake chamber according to a desired pressure trajectory. This control scheme was implemented on an experimental test bench, and its performance was studied for various values of the controller parameter. The control scheme was tested for various desired pressure trajectories reflecting actual brake operation.     

A simplified model of wheel/rail contact mechanics for non-Hertzian problems and its application in rail vehicle dynamic simulations

The presented model assumes semi-elliptical normal pressure distribution in the direction of rolling. The contact area is found by virtual penetration of wheel and rail. The normal pressure is calculated by satisfying contact conditions at the geometrical point of contact. The calculation is non-iterative, fast and completely reliable. It may be carried out on-line in MultiBody Systems (MBS) computer codes. The tests using the programme CONTACT by Kalker and experience from application in MBS codes show that the model is suitable for technical applications. The creep forces have been calculated with the FASTSIM algorithm, adapted for a non-elliptical contact area. Some applications in rail vehicle dynamics and wear simulation have been outlined.