Reliability Sensitivity Analysis for Drum Brake on Modal Stress

A reliability sensitivity analysis based on modal stress is presented and applied to predict the influence factors of parameters on drum brake.Firstly,the first 10 modes of prestress of the brake drum are performed in the software ANSYS Workbench.According to the results of brake noise research,it can be detected whether the drum brake meets the results that the noise frequency range of 500-1000 Hz.The reliability sensitivity design of mechanical parts based on the normal distribution parameters for complex mechanical system is discussed.Secondly,according to the first order second moment(FOSM)theory on reliability,the reliability sensitivity of drum brake is analyzed and calculated,and compared with the Monte Carlo(MC)numerical simulation results,The variation rules of reliability sensitivity is given,which provides a theoretical basis for the design of drum brake.

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.

Non-linear 2-DOF model and centre manifold theory to study limit cycle oscillations caused by drum-brake judder

This paper presents the research on the laws of systematic-parameter dependent variation in the vibration amplitude of drum-brake limit cycle oscillations (LCO). We established a two-degree non-linear dynamic model to describe the low-frequency vibration of the drum brake, applied the centre manifold theory to simplify the system, and obtained the LCO amplitude by calculating the normal form of the simplified system at the Hopf bifurcation point. It is indicated that when the friction coefficient is smaller than the friction coefficient at the bifurcation point, the amplitude decreases; whereas with a friction coefficient larger than the friction coefficient of bifurcation point, LCO occurs. The results suggest that it is applicable to suppress the LCO amplitude by changing systematic parameters, and thus improve the safety and ride comfort when applying brake. These findings can be applied to guiding the design of drum brakes.

SOME MECHANISMS OF DRUM BRAKE OSCILLATION AND SQUEAL

Drum brake squeal is usually due to the unstable oscillation excited by the dry friction between the drum and linings. In order to understand the mechanisms of drum brake squeal, a new drum brake dynamics model in closed form is presented for analyzing the modes and stability of drum brake vibration, so as to judge whether a squeal will happen or not. Then, a non contact experimental vibration analysis procedure based on nearfield acoustical holography technique is developed for measuring the operating deflection shape of drum. The measured ODS of drum is nearly the same as the unstable oscillation with the largest real component of eigenvalue among all the complex modes of brake drum.

Effects of cooling rate on vermicular graphite percentage in a brake drum produced by onestep cored wire injection

In this research, a vermicular graphite cast iron brake drum was produced by cored wire injection in a one-step method. Silica sand and low-density alumina-silicate ceramic were used as molding materials in order to investigate the effect of cooling rate on percentage of vermicular graphite and mechanical properties of the brake drum casting. Several thermocouples were inserted into the casting in the desired positions to measure the temperature change. By means of one-step cored wire injection, the two residual concentrations of Mg and RE were effectively controlled in the ranges of 0.013%-0.017% and 0.019%-0.025%, respectively, which are crucial for the production of vermicular graphite cast iron and the formation of vermicular graphite. In addition, the cooling rate had a significant effect on the vermicular graphite percentage. In the case of the silica mold brake drum casting, there was an obvious difference in the cooling rate with the wall change, leading to a change in vermicular graphite percentage from 70.8% to 90%. In the low-density alumina-silicate ceramic mold casting, no obvious change in temperature was detected by the thermocouples and the percentage of the vermicular graphite was stable at 85%. Therefore, the vermicular graphite cast iron brake drum with a better combination of mechanical properties could be obtained.

基于转鼓转速传感的中低速新能源汽车联合制动系统控制方法

中低速新能源汽车是常见的交通工具,但是其制动控制存在响应时间长、控制效果差的问题,设计一种基于转鼓转速传感的中低速新能源汽车联合制动系统控制方法。首先,构建基于转鼓转速传感的中低速新能源汽车动力学方程,采集传感信息,然后,考虑开环控制容易导致控制系统的稳定性和鲁棒性差的问题,基于转鼓转速传感的联合制动系统传递函数推导出开环、闭环双传递函数,最后,根据系统传递函数,设计PID控制器的参数,通过PID控制器输出电-液联合制动控制信号,实现汽车联合制动系统控制。实验结果表明:所提方法的速度-位移曲线与现实速度-位移曲线基本一致,加速误差在-0.5 m/s2~0.5 m/s2范围内,平均制动控制响应时间为0.075 s,具有良好的制动控制能力。

极端状态下周盘式制动器热应力耦合特性

鼓式制动器在制动过程中,由于其密封的结构,制动鼓温度过高,热应力变大,散热较难。这些因素会对制动器的制动性能产生较大影响,从而影响汽车的安全行驶。针对一种新型的周盘式制动结构,分析其在极端状态下的热应力耦合特性。以外径193 mm周制动盘为例,采用有限元仿真与实验,得出温度场、应力场、最大位移量等参数对制动性能影响的一般规律。结果显示:周盘式制动器制动过程中最大温度为153.65℃,最大应力为92.644 MPa,最大变形量为4.5562 mm,相比同类尺寸的鼓式制动器的最高温度可以降低6%,最大应力可以降低23%和最大变形量可以减小8%,其综合性能指标明显优于鼓式制动器,具有较高的工程应用价值。

卡车刹车鼓温度及差速器油温监控预测系统设计

为防止卡车在长时间刹车后,刹车鼓温度过热或高负载情况下差速器油温过高而发生事故,文章设计一种基于STM32F429和STM32F103单片机协同工作的卡车刹车鼓温度、差速器油温监控与预测系统。该系统以STM32F429单片机为主处理器,利用控制器局域网(controller area network,CAN)总线和以STM32F103为核心的从处理器进行及时数据传输和存储,并融入STemWin系统设计人机交互界面,基于自回归求积移动平均理论建立温度预测模型。仿真结果表明:该系统稳定可靠、预测精准,能有效减少因刹车鼓温度或差速器油温过高而引起的事故。

重卡制动鼓铸件结疤缺陷的工艺对策

重卡制动鼓铸件具有外廓尺寸较大、轴向较高、壁厚较大等特点。生产过程中制动鼓法兰内圆角处易出现结疤缺陷,严重时导致铸件报废,造成生产成本的增加。通过生产全工序跟踪、纵向和横向综合分析,推测出采用湿型粘土砂机器造型生产制动鼓时法上述缺陷产生的机理,并结合实际生产提出了控制型砂质量、合理调整型砂参数指标、缩短浇注时间以及增大排气量等工艺措施。经过一系列的生产测试和验证,成功地消除了制动鼓法兰内圆角处结疤缺陷。

钇基重稀土蠕化线在蠕墨铸铁制动鼓上的应用

介绍了蠕墨铸铁制动鼓的技术要求,详细阐述了制动鼓铸件喂丝相关参数的设定和铈基轻稀土蠕化线生产制动鼓铸件的过程控制以及产生的蠕化衰退问题。在其他化学成分基本不变的情况下,通过采用具有更强的蠕化效果和抗衰退能力的钇基重稀土替代铈基轻稀土蠕化线的措施,使铸件的金相组织符合要求,即:石墨以蠕虫状为主,蠕化率≥50%,没有片状石墨存在,基体以珠光体+铁素体为主,游离碳化物体积分数≤1%,游离碳化物+磷共晶的体积分数≤4%,且力学性能合格。

灰铸铁制动鼓石墨钝化生产工艺探讨

针对商用车在反复刹车时频繁的冷热循环易造成制动鼓开裂失效的问题,提出一种利用稀土元素、氮元素及钝化处理工艺钝化片状石墨端部的方法。在高碳当量成分条件下(CE≥3.9%),探讨灰铸铁制动鼓石墨钝化材质及生产工艺,提高制动鼓的常规力学性能和抗热疲劳性能,为商用车耐热及抗热疲劳制动鼓铸件的生产提供技术支持。

覆砂铁型工艺生产制动鼓的过程质量控制

介绍了使用覆砂铁型铸造工艺生产汽车制动鼓铸件的优缺点,详细阐述了覆砂铁型铸造生产线各工序过程质量控制要点,列举了多种覆砂铁型铸造生产线生产的汽车制动鼓铸件的铸造缺陷,对缺陷产生的原因进行了初步分析并制定了相应的防止措施。最后指出:细节决定质量,生产中要严格控制原材料质量、操作质量、过程参数以及工艺细节制定等内容,从而获得稳定的高质量铸件。

智能化制动鼓铸造车间设计实践

主要论述了制动鼓生产车间工艺及物流的规划设计,项目从规划设计、设备采购、建设到生产实施,充分考虑了自动化、智能化、绿色化,打造成本类产品生产的先进车间,成为行业典范。

电梯杠杆鼓式制动器松闸顶杆磁化摆动机理研究及案例分析

分析典型杠杆鼓式制动器结构特征,并刨析电磁铁内部结构。建立电磁铁有限元仿真分析模型,并分析松闸顶杆磁化摆动现象。介绍几种常见的防止松闸顶杆磁化摆动措施,并结合具体检验案例进行分析。

设计参数对鼓式磁流变液制动器传动性能的影响

针对传统圆筒式磁流变液制动器制动转矩小的缺点,提出了一种鼓形间隙磁流变液制动的方法。鼓式磁流变液制动器的磁流变液工作体积比圆筒式的更大,从而制动性能显著提升。通过有限元法对装置进行磁场分析,得到了两种间隙形状和鼓形张角对磁场的影响以及不同电流下磁感应强度与轴向距离的关系;建立了鼓式磁流变液制动器转矩与磁感应强度、半径、角速度等参数的关系。结果表明,鼓形的张角对磁流变液的工作体积影响显著;制动器转矩随电流增大而增大,在3 A时输出转矩为10.56 N·m,比圆筒式磁流变液制动器提高了23.6%。

铁型覆砂灰铸铁件氮气孔缺陷分析与改善措施

针对铁型覆砂铸造工艺生产灰铸铁件时产生的氮气孔缺陷,通过使用EDS能谱仪对氮气孔缺陷进行定性和定量分析,并结合铸件生产工艺对氮气孔的形成原因进行分析,通过在原材料上更换覆膜砂、提高新砂加入量、分开管理壳型线和铁型线回用砂,生产工艺上采取增加排气塞和提高铁型温度、固化时间、浇注温度等措施降低缺陷风险。改进后的工艺连续生产超过10万件产品,未再出现氮气孔缺陷。

鼓式制动器接触分析

通过建立鼓式制动器的理论模型 ,并运用工程分析软件ANSYS对摩擦衬片和制动鼓之间的摩擦接触进行分析 ,得出接触压力的分布特性及制动器的应力分布场 ,强化了理论设计 .

鼓式制动器瞬态温度场数值模拟计算

依据传热学理论和鼓式制动器的结构特点,分析了鼓式制动器的生热和散热过程,并用有限元法建立了制动鼓瞬态温度场数值模拟计算模型。以EQ1092货车后轮鼓式制动器为研究对象,运用ANSYS软件对其制动鼓在持续制动工况下的温升过程进行了数值模拟计算,得出了制动鼓的温度场的三维分布状况,分析了瞬态温度场的变化情况。经过试验验证,计算结果与实测值误差在20%以内。

鼓式制动器刚柔耦合虚拟样机

提出了鼓式制动器刚柔耦合虚拟样机的建立方法。将制动器中的凸轮和滚轮视为刚性体,将制动鼓、制动蹄和摩擦片视为柔性体,联合运用多刚体动力学分析和有限元方法,构建了刚柔耦合虚拟样机。以初速度为30、50和65 km/h的满载制动过程为典型工况进行了分析,将分析结果与台架实验值进行了对比。结果表明,仿真值与实验值的制动效能曲线变化趋势一致,最大制动力矩相对差值百分比小于10%。

双向自增力鼓式制动器有限元模型的建立与分析

通过对双向自增力鼓式制动器的受力分析 ,建立了其关键受力部件后蹄板的力学模型。应用大型的机械CAD/CAE/CAM软件I -DEAS建立了某一国产双向自增力鼓式制动器的有限元模型 ,对其强度进行有限元方法的计算和分析 ,求解它在工作状态下的应力情况。结果表明 ,该制动器蹄板在强度设计上满足不了要求 ,需在蹄板的两侧焊接加强板 ,这为该制动器的改进设计提供了理论基础。