Numerical and Experimental Analysis of the Aerodynamic Torque for Axle-Mounted Train Brake Discs

As the velocity of a train increases,the corresponding air pumping power consumption of the brake discs increases proportionally.In the present experimental study,a standard axle-mounted brake disc with circumferential pillars was analyzed using a 1:1 scale model and a test rig in a wind tunnel.In particular,three upstream velocities were selected on the basis of earlier investigations of trains operating at 160,250,and 400 km/h,respectively.Moreover,3D steady computational fluid dynamics(CFD)simulations of the flow field were conducted to compare with the wind tunnel test outcomes.The results for a 3-car train at 180 km/h demonstrated:(1)good agreement between the air resistance torques obtained from the wind tunnel tests and the related numerical results,with differences ranging from 0.95%to 5.88%;(2)discrepancies ranging from 3.2 to 3.8 N·m;(3)cooling ribs contributing more than 60%of the air resistance torque;(4)the fast rotation of brake discs causing a significantly different flow field near the bogie area,resulting in 25 times more air pumping power loss than that obtained in the stationary brake-disc case.

The Study of the Auto Disk Brake Air Test

In the paper weakness of air leakage system in our company is discussed firstly. Secondly the improved scheme of air leakage system including auto-control is designed. Then, the tooling with role of location and recovery is developed. At last the application of design optimization is processed. The result reveals that the system of air leakage detection is very valuable and important to manufacture.

Experimental study on the temperature evolution in the railway brake disc

Increasing operating speed of modern passenger railway vehicles leads to higher thermal load onthe braking system. Organic composite brake pads are poor thermal conductors, hence frictionalheat is absorbed mainly by the disc. In this study three brake pad types were tested on thedynamometer. Metallic fibres, steel and copper, were introduced to the formulation of twomaterials. The third was a non-metallic material - a reference case. Dynamometer test comprisedemergency brake applications to determine the frictional characteristics of the materials andconstant-power drag braking to analyse the effect of metal fibres on temperature evolution,measured by six thermocouples embedded in the brake disc. Mean friction coefficient is analysedand discussed. It is concluded that conductive fibre in the friction material formulation mayinfluence its tribological characteristics. Despite high thermal conductivity, metal fibres in theconcentration tested in this study, did not reduce temperature of the brake disc.

BRAKE TEST OF SiCp/A356 BRAKE DISK AND INTERPRETATION OF EXPERIMENTAL RESULTS

Material properties are obvious different between aluminum matrix composites and iron and steel materials. After the brake disk braked at the same speed, the average temperature of the aluminum brake disk is 1.5 times as high as one of iron and steel brake disk, the thermal expansion value of the aluminum brake disk is 2 times as big as one of iron and steel brake disk. Mechanical property of the material decreases with the temperature increasing generally during braking, on the other hand, the big thermal stress in the brake disk happens because the material expansion is constrained. Firstly, the reasons of the thermal stress generation and the fracture failure of brake disks during braking are analyzed qualitatively by virtue of three-bar stress frame and sandwich deformation principles in physic, and then the five constraints which cause the thermal stress are summarized. On the base of the experimental results on the 1：1 emergency brake test, the thermal stress and temperature fields are simulated; The behavior of the fracture failure is interpreted semi-quantitatively by finite element analysis, There is the coincident forecast for the fraction position in term of the two methods. In the end, in the light of the analysis and calculation results, it is the general principles observed by the structure design and assembly of the brake disk that are summarized.

Experimental prototyping of the adhesion braking control system design concept for a mechatronic bogie

The dynamic parameters of a roller rig vary as the adhesion level changes.The change in dynamics parameters needs to be analysed to estimate the adhesion level.One of these parameters is noise emanating from wheel–rail interaction.Most previous wheel–rail noise analysis has been conducted to mitigate those noises.However,in this paper,the noise is analysed to estimate the adhesion condition at the wheel–rail contact interface in combination with the other methodologies applied for this purpose.The adhesion level changes with changes in operational and environmental factors.To accurately estimate the adhesion level,the influence of those factors is included in this study.The testing and verification of the methodology required an accurate test prototype of the roller rig.In general,such testing and verification involve complex experimental works required by the intricate nature of the adhesion process and the integration of the different subsystems(i.e.controller,traction,braking).To this end,a new reduced-scale roller rig is developed to study the adhesion between wheel and rail roller contact.The various stages involved in the development of such a complex mechatronics system are described in this paper.Furthermore,the proposed brake control system was validated using the test rig under various adhesion conditions.The results indicate that the proposed brake controller has achieved a shorter stopping distance as compared to the conventional brake controller,and the brake control algorithm was able to maintain the operational condition even at the abrupt changes in adhesion condition.

Investigation into precision engineering design and development of the next-generation brake discs using Al/SiC metal matrix composites

Substantially lightweight brake discs with high wear resistance are highly desirable in the automotive industry.This paper presents an investigation of the precision-engineering design and development of automotive brake discs using nonhomogeneous Al/SiC metal-matrixcomposite materials.The design and development are based on modeling and analysis following stringent precision-engineering principles,i.e.,brake-disc systems that operate repeatably and stably over time as enabled by precision-engineering design.The design and development are further supported by tribological experimental testing and finite-element simulations.The results show the industrial feasibility of the innovative design approach and the application merits of using advanced metal-matrix-composite materials for next-generation automotive and electric vehicles.

Numerical Efficient Thermal Network for Calculating the Brake Disc Temperature

The simulation of the brake disc temperature is an important tool in the development of passenger cars.Nowadays thermal models of brake discs are real-time applications,running on electronic control units(ECUs)of cars to improve the vehicle safety in several ways.These models are often working with full empirical methods,leading to large deviations between calculation and measurement.To meet the requirements of automotive safety integrity levels(ASILs),these thermal models cannot rely on the state of the art ambient air temperature sensors,which causes unacceptable deviations.Focusing on numerical efficient thermal simulations,a new approach of a semi-analytical thermal network for simulating the brake disc temperature with minimal effort is proposed.The thermal network is based on lumped parameters,using two thermal capacity nodes and a constant ambient temperature.Using semi-analytical correlations,the model can be adapted to different geometries and car lines effortlessly.The empirical parameters of the model result only from two standardized tests.These parameters are used to evaluate the estimation accuracy in real driving situations.Additionally,the adaptability is tested for two different car lines and four brake disc dimensions.These tests are initially performed with unchanged parameters and afterwards with refitted parameters.The model shows a good estimation for the tested load cases.Compared to the state of the art,the proposed model is less accurate than complex finite element method(FEM)models and computational fluid dynamic(CFD)approaches,but shows a higher accuracy and better adaptability than other lumped parameter models with comparable numerical effort.Hence,possible applications can be dimensioning the brake system in the development process of new car lines or a real-time simulation on the latest ECU in the vehicle.

Numerical modeling and analysis of the mechanism of a novel shock wave regulator for impact test

Based on the concept of hydraulic dissipation of kinetic energy,a novel shock wave regulator,whichis composed of a danaper and an externally triggered valve,is presented with thorough analyses on itsworking mechanism.By establishing motion equations of each component of the regulator and simulatingthe dynamic behavior of the whole system,the shock wave regulator is demonstrated numerically to beable to change the width and amplitude of shock pulses.Prompt and easy adjustment can be achieved bychanging the equivalent flow area of damping orifices and consequently the closing velocity of the flow areaof a valve,which makes it applicable to different impact testing.

考虑前车制动意图的自动紧急制动策略及其测试评价方法

为提高车辆自动紧急制动(AEB)系统的避撞性能,提出了一种考虑前车制动意图的AEB策略及其测试评价方法。通过搭建“PreScan+Simulink+驾驶模拟器”联合仿真平台采集驾驶人制动数据,基于K-均值(K-Means)聚类方法对制动意图进行分类,采用滑动时间窗口提取了意图识别模型训练数据集;通过双层隐马尔可夫模型识别前车制动意图,主车根据不同制动意图计算临界安全距离阈值并制定避撞控制策略;建立PreScan+Simulink虚拟仿真测试环境,提出了基于层次分析法的AEB策略综合评价方法,通过与4种典型AEB控制模型进行对比,验证了所提出方法在不同制动程度场景下均可及时触发制动以避免碰撞,同时可减少过早制动造成的驾驶不适感。

电涡流缓速器优化设计与制动性能分析

文章在考虑去磁效应的基础上建立电涡流缓速器数学计算模型,采用涡流折算系数法求出闭合磁路磁感应强度,推导出电涡流缓速器电磁制动力矩表达式;在某汽车制动系统有限公司现有产品的基础上,将圆形极柱优化设计为扇形极柱,并利用Maxwell有限元仿真软件对不同长度扇形极柱的新型电涡流缓速器模型的制动力矩进行仿真分析;将最终确定的新型电涡流缓速器通过有限元仿真和台架实验与原产品进行对比验证。结果表明:新型电涡流缓速器与传统电涡流缓速器的制动扭矩在不同转速下变化的规律基本一致,制动性能有明显提升;仿真结果和实验结果最大误差小于5%,证明了新型电涡流缓速器的有效性和优化设计的正确性。

水平减速能力研究进展

水平减速能力是人体在水平方向运动过程中快速改变速度和方向的基础,对运动表现具有重要影响。对国内外相关研究进行系统梳理,归纳总结水平减速能力的测试评估、影响因素和训练策略的研究现状发现:(1)水平减速能力的测试方法主要有最大水平减速能力测试、特定距离内水平减速能力测试和变向能力测试;直接测评指标主要有减速度、制动距离和制动时间,衍生性指标包括制动力、制动冲量、制动功率、减速指数和减速赤字等;(2)水平减速能力影响因素主要包括下肢肌肉力量、肌力不对称和制动技术;(3)水平减速能力的训练策略可运用下肢离心力量训练结合向心快速力量训练提高制动力的产生与运用能力和动态姿势控制能力;采用超等长收缩训练结合离心落地控制能力训练,有效提升制动过程中的拉长-缩短周期运动能力;选择单侧和双侧力量训练,改善肢体间离心制动的不对称性;运用专门性水平减速训练,并结合抗阻训练,针对性地提高运动员面对不同外部刺激时的预测和响应能力,改善制动技术动作,显著优化制动力分配和调控能力。

试验环境的盘式制动器NVH特性研究

文中采用多体动力学和声学边界元等数值方法,研究某盘式制动器试验条件下的NVH(Noise,Vibration,Harshness)特性。首先,建立试验环境的制动器刚柔耦合模型,从结构、激励源和传递路径3个方面分析制动NVH特性影响因素;然后,运用声学边界元法仿真得到制动振动辐射的噪声,并与台架试验结果进行比较。结果表明:制动盘第2~5阶轴向模态,支架第2~3阶轴向模态,以及制动钳和连接板第1阶轴向模态等模态固有频率与台架试验噪声频率较接近,可能引起共振而产生制动噪声;在不影响制动性能的前提下,改变制动盘与摩擦衬片阻尼系数能改善制动NVH特性;悬架螺旋弹簧下端振动大,减振器与衬套对振动具有显著衰减作用;由仿真声压级云图发现,制动盘与摩擦片接触部位声压级最大,且随频率增加呈先增后减趋势,与台架试验对应测点的噪声结果进行直接比较,两者趋势一致。

基于电动汽车制动安全检测的短时工况及方法研究

常规的制动安全检测通常采用长时间、极端工况,但可能会失去准确的工作范围。针对这一不足,首先提出一种踏板稳定模式的短时工况试验方法,该方法结合了现有的测试标准,并不限于单一的极端制动模式,而是可以考虑电动汽车的快速稳态运行。在此基础上,基于机器学习对运行片段回归并通过连续拼接构建短时工况。利用短时工况提出一种改进的制动安全检测方法,该方法通过主成分分析对制动片段的特征参数进行降维,同时根据特征参数计算制动片段的重复性距离判断安全隐患。最后,通过在测试台架上跟随短时工况,验证所提出的短时工况和制动安全检测方法的有效性。

考虑多失效形式的电子制动助力器主密封圈多目标优化设计

针对电子制动助力器制动主缸主密封圈容易发生泄漏、啃噬和磨损等失效问题,进行主密封圈参数的多目标优化设计。通过台架试验分析密封圈主要失效形式,并结合用户制动工况数据进行典型工况下的仿真分析,从而确定优化目标。以主密封圈左下处角度、顶点距离、橡胶硬度和摩擦因数为变量进行正交试验设计,并利用Abaqus软件建立力学模型,得到挤入量、最大接触应力和磨损量的拟合方程。最后以密封性、抵抗啃噬和磨损为优化目标,采用多目标遗传算法,结合用户制动工况数据对密封圈材料参数、摩擦因数以及关键尺寸等进行了优化设计。仿真计算表明:优化设计后主密封圈在保证密封性的前提下,抵抗啃噬和磨损性能得到了一定改善。

基于LMS Test.lab的数控转台振动测试研究

基于LMS Test.lab测试系统,根据某成形铣齿机床的加工工艺特性和技术要求,提出与其相配套的数控转台(简称转台)振动测试方案,并进行实际加工工况下振动测试。测试表明,转台的固有频率远低于加工时的激振频率;铣齿过程中转台台面周向振动位移最大,且随着进给速度的增大而增大,随着消隙蜗杆作用力增大而减小。测试结论证明了该测试方案的可行性和有效性。

一种轻量化制动摩擦片背板样本的装调与实车测试分析

本文对一种轻量化制动摩擦片背板进行了材料的分析与选择,并利用粘接的方式进行了样本的组装。通过对不同车型进行对比,最终选定合适车型,在实车上安装调试后,进行了综合道路测试。通过对测试数据和样本实体的分析,验证该种轻量化制动摩擦片背板设计的可行性,对无人驾驶汽车的适用性,探讨了材料进一步优化的思路和未来发展前景。

面向自动紧急制动功能测试的目标物移动平台设计

为实现车辆自动紧急制动(AEB)系统功能测试中目标物移动平台的开发,针对移动平台进行了构型设计、强度分析、疲劳寿命估计、测试场景路径跟踪等研究。通过对《C-NCAP管理规则(2024年版)》规定的测试场景进行分析,提取目标物运动路径,根据边界条件得到期望轨迹,再通过动力学仿真得到轨迹跟踪结果。经过对比,仿真结果与规定要求基本一致,表明设计的移动平台能够满足AEB系统功能测试需求。

基于气动方程的列车管路充排气数学模型

智能化制动试验系统的核心是建立不同编组列车首车制动压力控制模型。从气动力学方程入手,建立了不同编组列车首车列车管充排气特性数学模型,该模型考虑了编组列车除首车之外的其余车辆充排气特性对首车列车管气压变化的影响。提出通过对制动阀有效截面积的设计计算,并带入所建立的数学模型中进行仿真试验,从而对研制新制动阀以及改进或检修制动阀提供理论基础与技术指导。利用列车制动试验台得到的试验数据与仿真结果进行对比分析,验证模型的准确性,并预测了更长编组列车首车列车管的初充气及常用制动时的气压数据。

市域列车司机制动试验方案研究

[目的]制动系统作为市域列车核心系统之一,其性能决定着车辆的运行安全;司机制动试验是市域列车制动系统必备功能,其可有效保障列车投入运营前制动系统的安全、可靠,故有必要对其进行深入研究。[方法]通过对我国市域列车车辆的情况分析,明确了司机制动试验设计思路;制定了司机制动的试验方案,并进行验证。[结果及结论]结合市域列车运营特点,阐述了适用于市域列车的司机制动试验的技术方案,为市域列车制动系统自检功能提供专业支持。

线控制动液压电磁阀气压检测动态性能分析

针对线控制动液压电磁阀测试中使用制动液会产生难以清洁、腐蚀性强等问题,采用压缩空气作为检测介质进行气检可有效地解决这一问题。此时,电磁阀液检和气检动态响应时间合格限之间的关系成为研究重点。因此,根据电磁阀的结构参数,利用ANSYS软件对电磁阀流场进行分析,计算获得流体力参数。然后,利用MATLAB/Simulink软件构建电磁阀仿真模型,从而获得电磁阀液检响应时间与气检响应时间之间关系式。最后,设计电磁阀液压测试系统和气压测试系统,对液检和气检动态响应时间合格限进行测试。结果显示:当电磁阀液检合格限为3.50 ms时,测试得到气检合格限实际值为3.33 ms,计算得到其理论值为3.125 ms,相对误差6.16%,验证了模型的准确性,对电磁阀气代液检测研究具有指导意义。