Analysis of thermomechanical phenomena in multidisc clutches and brakes

The paper presents a model of transient thermomechanical phenomena occurring in a pack of friction discs of a multidisc wet clutch or a brake. Account is taken of the couplings between phenomena appearing on various friction surfaces. Numerical methods permitting an effective investigation of these are described.

Results of calculations are presented for the case when the thermoelastic instability effect appears. A mechanism for the growth of non-uniformities in normal pressure distributions on friction surfaces as well as couplings between phenomena occurring on various surfaces are discussed. It is also shown that the phenomena arising on friction surfaces strongly affect the thermal stresses inside the discs.     

ANALYSIS OF FAILURE MECHANISM IN MULTIPLE DISC WET BRAKES

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风力发电机刹车元件摩擦系数测量装置的研制

风力发电机刹车装置的刹车盘与刹车片的摩擦系数直接影响到刹车效率和刹车片的使用寿命。基于我国风力发电机的设计、制造现状和风力发电机的特殊工况,设计研制球盘式摩擦系数测量装置。该装置利用力矩平衡原理间接测量摩擦力。采用高灵敏度传感器采集平衡摩擦力、压紧力、相对滑动速度,并通过数据采集卡、计算机等硬件搭建基于虚拟仪器技术的测试系统,LabVIEW软件开发数据采集分析系统实现信号的数据采集、数据预处理、波形信息分析,得出摩擦系数在各影响因素下的变化情况,从而对刹车材料的摩擦性能进行分析,明确材料的性质,为估算出风力发电机刹车元件的寿命、风力发电机的设计提供依据。     

CRH2盘形制动系统制动尖叫噪声研究

为了研究高速动车组的制动尖叫噪声,建立CRH2拖车盘形制动系统的摩擦耦合有限元模型,对其进行运动稳定性和制动自激振动的瞬态动力学分析,研究了摩擦因数、闸片以及制动盘弹性模量对制动系统尖叫噪声的影响。结果表明：随着摩擦因数μ的增大,盘形制动系统发生制动尖叫噪声的趋势增加;随着闸片弹性模量的增大,制动系统发生制动尖叫噪声的趋势增加,并且激发的噪声频率也明显变大;随着制动盘弹性模量增大,制动系统发生制动尖叫噪声的趋势先降低后增大。     

Friction and wear of sintered metallic brake linings on a C/C-SiC composite brake disc

The friction and wear of sintered metallic brake linings on a C/C-SiC composite brake disc were studied. This paper reports on the friction and wear properties of sintered metallic (MMC) brake linings, which appear to combine well with a C/C-SiC brake disc. The friction characteristics were examined with a dynamometer on two different commercial motorcycle brake systems, differing in terms of the brake caliper and the dimensions of the disc. The influence of the components, such as graphite, and the abrasives in the metallic matrix on the formation of the friction layer was investigated using a scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX). The friction layer formed on the pad's sliding surface by oxidation wear, which consisted mostly of iron and copper oxides, was confirmed. The friction properties of the sintered metallic brake pads were determined and related to the composition and structure of the brake lining. This investigation of the friction characteristics of a brake couple comprising (MMC) brake linings and a C/C-SiC composite disc will increase our understanding of this material, which works in a completely different way to classical brakes based on metallic discs.     

A reduced-scale brake dynamometer for friction characterization

Friction behavior is a critical factor in brake system design and performance. For up-front design and system modeling it is desirable to describe the frictional behavior of a brake lining as a function of the local conditions such as contact pressure, temperature, and sliding speed. Typically, frictional performance is assessed using brake dynamometer testing of full-scale hardware, and the average friction value is then used for the remaining brake system development. This traditional approach yields a hardware-dependent, average friction coefficient that is unavailable in advance of component testing, ruling out true up-front design and leading to redundant lining screening tests. To address this problem, a reduced-scale inertial brake dynamometer was developed to determine the frictional characteristics of lining materials. Design of a reduced-scale dynamometer began with the choice of a scaling relation. In this case, the energy input per unit contact area was held constant between full-scale and reduced-scale hardware. All linear variables were thereby scaled by the square root of the scaling factor, while the pressure, temperature, sliding velocity, and deceleration were kept constant. Experimental validation of the scaling relations and the reduced-scale dynamometer focused on comparisons with full-scale dynamometer data, particularly the friction coefficient. If similar trends are observed between reduced-scale and full-scale testing, the reduced-scale dynamometer will become an important tool in the up-front design and modeling of brake systems.     

制动过程中闸片材料与制动盘温度关系试验研究

为探讨碳/陶制动盘与不同闸片材料的匹配性,对碳/陶制动盘分别与碳/陶复合闸片、铜基粉末冶金闸片和铁基粉末冶金闸片组成的摩擦副进行制动试验,研究了在制动过程中盘面各点瞬时温度、最高温度、闸片温度与制动工况的关系。结果表明：碳/陶制动盘与碳/陶复合闸片摩擦副温度及温度梯度均高于其他2种摩擦副,其温度梯度在低速制动时随压力的增加而明显增加,当制动速度较高时,温度梯度并没有随压力的增加而增加;对于碳/陶制动盘与铜基和铁基粉末冶金闸片摩擦副,随制动速度和压力的提高,盘面温度梯度变化不明显。原因在于材料导热性和起始摩擦因数决定了盘面的散热能力和制动功率,碳/陶制动盘与碳/陶复合闸片摩擦副因较高的起始摩擦因数以及较低的导热性,其制动功率高和散热能力低,导致盘面温度持续升高。     

Neural network prediction of disc brake performance

An automotive brake's performance results from the complex interrelated phenomena occurring at the contact of the friction pair. These complex braking phenomena are mostly affected by the tribochemical properties of the friction material's ingredients, the brake disc properties, and the brake's operating regimes. In this paper, the synergistic effects of the friction material's properties, defined by its composition and manufacturing conditions, and the brake's operating regimes on the disc brake factor C variation have been modelled by means of artificial neural networks. The influences of 26 input parameters, determined by the friction material composition (18 ingredients), its manufacturing conditions (5 parameters), and the brake's operating regimes (3 parameters) on the brake factor C variation, have been predicted. The neural model of the disc brake cold performance has been developed by training 18 different neural network architectures with the five different learning algorithms. The optimal neural model of disc brake operation has been shown to be valid for predicting the brake factor C variation of the cold disc brake over a wide range of brake's operating regimes and for different types of friction material.     

盘式制动系统参数对制动颤振的影响分析

为了研究盘式制动系统参数对制动颤振的影响,建立了二自由度的动力学模型,利用Matlab进行数值仿真,分别研究了制动初速度、制动压力、阻尼和刚度等因素对制动系统动力学特性的影响。根据得到的位移曲线和相图可以看出:随着制动初速度的增大,系统黏滞阶段持续时间减少,并逐渐进入稳定运动状态;制动压力相对较小时,制动系统处于稳定状态,随着制动压力的增大,摩擦片和制动盘的振动幅值也随之增大,振动强度变大;在阻尼增大的过程中,摩擦片和制动盘均由起初的纯滑动运动状态进入稳定运动状态,且达到稳定运动状态的时间也逐渐缩短;摩擦片在相对较小的制动刚度下即可达到稳定状态,而制动盘则需要有较大的刚度才能达到稳定状态。     

Development of a systematic process for hydraulic brake system design and for hot judder characteristic estimation

This paper presents a systematic process for the design of hydraulic brake systems of automotives and for the one-way estimation of hot judder characteristics. The systematic process was programmed by using MATLAB, and the variation of the hot judder characteristics of disc brakes attributed to the change in the design parameters of hydraulic components can be calculated by using the same program. The brake pressure transfer process was mathematically derived. A finite element analysis model of a ventilated disc brake was created. The friction coefficient between disc and pad and the convection coefficient on the disc surface were applied as functions of temperature. The reliability of the simulation results were verified through a comparison with dynamo test results.     

重型车辆织构化刹车系统热力学行为与摩擦学性能研究

重型车辆刹车系统受瞬态高温和雨水异常侵入的影响,易引起热力学行为与摩擦性能退化。为研究表面织构对刹车系统热力学行为和摩擦学特性的影响,基于有限元法开展刹车系统热力学分析,考虑大量雨水侵入的液体润滑极端情况,提出一种动压润滑与织构集成模型的摩擦学性能分析方法。结果表明：水平凹槽织构可使制动盘温度场及应力场分布较均匀,进而避免接触区域局部瞬态高温引起的车辆制动失效;随着凹槽织构倾斜角度增大,承载力增大,摩擦因数减小;不同组合型织构中,圆柱与椭球组合型织构表面承载力最大、摩擦因数最小,圆锥与椭球组合型织构表面承载力最小、摩擦因数最大。研究发现重型车辆刹车系统表面构筑合适倾斜角度凹槽织构和组合型织构有助于提升其工作性能。     

汽车盘制动器优化设计热和机械特性的研究(一)

由于热量集中于制动盘的表面造成热弹不稳定性(TEI)而引起热变形.这样可能发生大家知道的低频强烈振动.因为在盘和衬块的接触面间的摩擦系数变化,在摩擦衬决发生尖叫声.通过对热聚集和尖叫现象的联合分析,对高热和机械特性可设计一最佳的盘和摩擦衬块.本文同时考虑了热和机械不稳定性按照盘的厚度,卡钳的加压方式,衬片弧长进行了数值...     

重型汽车新技术应用——发动机缓速器

随着汽车物流业的发展，车辆的载重量越来越大，所有这些负荷最终都要加到鼓／盘式制动器、轮边减速器上，车辆越重，惯性力越大，需要的制动摩擦力也越大，产生热量越大，如果频繁地使用刹车，就会造成刹车片的过热，甚至发软、燃烧，最后失效。本文着重介绍运用在重型卡车上的发动机缓速装置，解决重型卡车烧刹车片的问题。     

On the dry and wet sliding performance of potentially new frictional brake pad materials for automotive industry

In this work, dry and wet continuous sliding performances of newly developed four different non-commercial frictional brake pad materials (NF1, NF2, NF4, and NF5) were evaluated and compared with other two chosen commercial brake pad materials (CMA and CMB) using a small-scale tribo-tester of pad-on-disc type.Results showed that under dry continuous braking, friction coefficients for all non-commercial brake pad materials including the CMB were insensitive to the type of brake pad materials. In addition, all brake pad materials showed a slight increase in the friction coefficients (5–19%) with increasing pressure or speed. Meanwhile, the wear rates were substantially dependent on the type or ingredient of brake pad materials and the pressure. Conversely, under wet sliding condition, the friction coefficients were decreased by a factor of 2. Moreover, no evidence of HD water film could be evidenced as the measured friction coefficient values were in the order of dry friction. Thus, the wet results suggested that the friction behaviour was influenced by factors other than HD film, and the values of friction coefficient were in the range of dry friction, mixed and boundary lubrication friction. Qualitative assessment of the SEM morphologies of brake pad surfaces showed that tribofilms were easily formed in dry braking and hardly formed in wet braking. Besides, all brake pad rubbing surfaces showed contact plateaus “patches” and disintegrations of various sizes and locations depending on the braking condition. Furthermore, the removal of material was associated with either mechanical crushing action performed by entrapped wear debris or due to disintegration of plateaus which were accelerated by spraying the water.     

混合法多目标优化盘式制动器

介绍盘式制动器混合多目标优化问题数学模型的建立。提出以制动摩擦力矩和制动时间为主要优化目标的多目标函数 ,并采用 2种直接优化方法 (采用惩罚函数的SEEK和ADRANS子程序 )相结合进行优化。结果表明 ,该方法简便可靠、收敛速度快。     

基于接触压力分布和非均匀热流密度的列车制动盘热机耦合分析

针对铁路列车制动闸片摩擦块排布方式对制动盘热机耦合响应状态影响显著的问题，提出了一种考虑接触压力分布和非均匀热流密度的热机耦合仿真分析方法。通过在轨道车辆制动性能试验台上进行的制动台架试验，从温度的角度验证了所提方法的正确性。在此基础上，建立了列车全尺寸盘型制动系统有限元仿真分析模型，对现有铁路列车制动闸片摩擦块的排布方式进行了优化分析。结果表明，合理的制动闸片摩擦块排布方式可以显著降低制动盘面的温度和应力峰值，在改善制动盘面温度和应力分布的同时，提供较为优异的制动性能。研究成果可为铁路列车盘型制动系统热机耦合分析提供一种快速有效的仿真分析方法，同时可为铁路列车制动闸片摩擦块的排布优化提供指导方向。     

汽车风冷盘式制动器摩擦学特性试验研究

为得出制动参数对汽车风冷盘式制动器摩擦学特性的影响机理,考虑空气流动和车辆惯性因素,基于噪声、振动与声振粗糙度（NVH,Noise Vibration and Harshness）台架试验机精确模拟制动工况,研究摩擦副表面在不同制动压力（1.0~3.0 MPa）、行驶速度（5~30 m/s）以及温度（100~350  ℃）条件下平均摩擦系数与摩擦稳定系数的变化规律。试验结果表明：制动压力增大时,摩擦力矩并非一定随之增大,尤其是较高行驶速度条件;当制动盘表面温度超过300 ℃时,低速条件下的平均摩擦系数和摩擦稳定系数急剧减小。     

Liquid-cooled disc brakes

The conventional disc brake can reach very high temperatures that seriously impair the brake performance despite the continuing development of better materials used as friction pairs. Lower temperatures can be obtained by using a fluid to remove much of the heat generated by friction. This paper analyses the thermal behaviour of oil-immersed brakes and discusses the factors that influence the friction surface temperature and performance. Finally consideration is given to the use of wet brakes in road vehicles.     

摩托车盘形制动器摩擦片材料磨损形貌分析

采用XDZ-A型摩擦材料制样机将有机石棉摩擦片材料制备成试验所需的标准试样,用X-DM型调压变速摩擦试验机模拟摩托车制动实际工况,对标准试样开展不同压力、滑动速度和温度下的组合试验.对扫描电子显微镜(SEM)观测到的有机石棉摩擦片材料与灰铸铁HT250摩擦盘对磨后的磨损形貌进行了分析.分析结果表明:无论是正压力、速度的增大还是温度的升高,都使得摩擦片磨损越来越严重,形貌越来越复杂.     

摩擦副结构与制动盘温度关系的试验与模拟研究

摩擦副结构是影响制动盘温度分布的重要因素之一。针对闸片形状为圆形、三角形和六边形三种结构的摩擦副,采用制动试验台进行了速度为50～250 km/h的制动试验,并利用ABAQUS软件数值模拟了三种摩擦副不同工况条件下制动盘温度场的变化过程。结果表明：数值模拟温度场与试验测试结果具有良好的相似性。摩擦副结构对盘面温度分布的影响程度与制动条件密切相关,其结构形式对制动盘面温度的影响程度在制动初期最为明显,且随制动初速度和制动压力的增加而增加。这缘于闸片结构的不同导致了摩擦面摩擦弧长分布的不同,随制动速度升高和压力增加,摩擦弧长的差异起到了放大能量差别的作用,从而表现制动盘温度分布对闸片结构的敏感程度增加。