铜基复合制动材料摩擦磨损性能研究进展*

我国高速列车的不断提速,对制动盘材料的性能提出了更高的要求。铜基复合制动盘材料由于具有高比刚度、高比强度、优良的高温性能,以及良好的摩擦磨损性能等优点,被认为是最有应用前景的制动盘材料。在介绍高速列车制动盘材料发展的基础上,进一步论述了铜基复合制动盘材料的构成组元、制备方法及发展历程;阐述了铜基复合制动盘材料摩擦磨损性能的研究现状;最后展望了铜基复合制动盘材料的发展趋势,为高性能铜基复合制动盘材料的研制提供参考。     

一种铝基复合材料制动盘用树脂基摩擦材料

研制了一种适用于铝基复合材料制动盘的树脂基摩擦材料,测试了其物理力学性能及摩擦磨损性能。结果表明：所研制的摩擦材料具有较好的物理力学性能,各项指标达到了相应的技术要求;与用于铸铁制动盘的摩擦材料相比,具有更高的摩擦因数,更小的磨耗,制动力矩曲线平稳,能更好地适应铝基复合材料制动盘。另外,台架试验结果表明：摩擦副的摩擦磨损性能能够满足200km／h高速列车的要求。     

Al2O3增强粉末冶金铜基摩擦材料摩擦磨损性能研究

为提高铜基粉末冶金摩擦材料的耐磨性及制动效果,使用粉末冶金法（PM）制备氧化铝增强铜基摩擦材料,采用布氏硬度计、扫描电子显微镜（SEM）、能量色散光谱仪（EDS）等测试手段以及摩擦磨损实验,研究氧化铝的掺杂对摩擦材料微观组织和摩擦行为的影响。结果表明：在制备的铜基摩擦材料中,氧化铝硬质颗粒在铜基体中分布均匀,由于硬质相的存在所形成位错钉扎效应对复合材料的硬度有大幅的提升,而对材料的密度有一定的消极作用。摩擦实验结果显示,氧化铝可以提高材料的摩擦因数并增强其耐磨性;且随着载荷的增大Al2O3-Cu复合材料的摩擦因数较高且稳定性较好,磨损率有明显的降低,表明氧化铝的掺杂对铜基材料有显著的增强效果。通过光学显微镜以及EDS分析得出,Cu基材料的主要磨损机制为氧化磨损和黏着磨损,而Al2O3-Cu材料的磨损机制为氧化磨损和磨粒磨损组成的混合磨损。     

固体润滑剂改善摩擦衬片性能的考察

摩擦衬片和制动衬片一样必须具备一些摩擦学性能。这些性能——尤其是高而稳定的摩擦和低磨损率十分重要，因为这些衬片大多是保险部件。人们发现一些无机固体润滑剂和固体协同混合物在许多状况下对改善磨损物和摩擦系数之类的摩擦学性能起着重要作用。除含石棉的摩擦衬片外，无石棉的摩檫衬片还需要添加其它添加剂。本文对试验结果进行了讨论。     

碳纤维改性热塑性聚酰亚胺材料摩擦磨损性能

通过正交实验设计和方差分析,系统考察了工况（温度、速度及载荷）对碳纤维改性热塑性聚酰亚胺（TPI）摩擦磨损行为的影响。用电子显微镜（SEM）观察其磨损面形貌分析材料磨损机制。研究表明：随着温度升高,分子链相对滑移增强,体现出良好的自润滑特性,材料的摩擦因数和磨损率均有所下降;排除摩擦热的干扰,方差分析表明载荷、速度及其交互作用对材料摩擦磨损行为影响不显著。根据粘着摩擦理论,载荷的改变对材料抗剪切强度无明显作用,表现为材料摩擦磨损性能稳定。随速度的增加,材料抗剪切强度呈现下降趋势,同时考虑到受力中的塑形硬化现象,摩擦因数出现先增后减的变化。     

低温环境下制动参数对列车制动材料摩擦性能的影响

利用销-盘式摩擦磨损试验机与温度控制装置模拟低温环境下列车的制动行为,研究了低温环境(-20℃)下制动压力、制动速度对制动盘与制动闸片摩擦磨损性能的影响.研究结果表明,低温环境(-20℃)下制动盘与闸片之间的摩擦因数和磨损率均比室温环境(20℃)下略微提高.在低温环境下,制动压力和制动速度对制动材料摩擦磨损与损伤行为有明显影响.制动盘与闸片之间的摩擦因数随制动压力的增大呈现先减小后趋于稳定的变化趋势;随制动速度增加,摩擦因数呈现先减小后增加的变化趋势.制动盘和闸片的磨损率随制动压力的增大均呈现先增大后趋于稳定的变化趋势,且闸片材料的磨损率均大于制动盘材料的磨损率;随制动速度的增大,制动盘磨损率呈现快速减小的趋势而闸片磨损率呈现先减小后趋于稳定的趋势.随制动压力和制动速度的增大,闸片磨损表面第三体层分布更加均匀,表面剥落坑数量与面积呈减小趋势.     

二硫化钼改性热塑性聚酰亚胺材料稳定摩擦磨损性能

改进MPX-2000摩擦磨损试验机，实现了在线测定材料摩擦磨损性能。实验测定载荷、滑动速度和对偶面粗糙度等工况条件对二硫化铝改性热塑性聚酰亚胺（TPI）基复合材料摩擦磨损性能的影响，结合低真空扫描电子显微镜（FESEM）观察其磨损面形貌的结果分析材料磨损机理。研究表明：在线测定法与传统称重法测定的材料磨损情况基本一致。在线测定结果发现：在材料稳定磨损状况下，随着载荷的增大，材料磨损率增加而摩擦因数降低；随着滑动速度的增大，材料磨损率增加，但其对摩擦因数影响不明显。高速下磨损机理主要是严重的粘着磨损和疲劳磨损：同时发现磨损率与对偶面粗糙度呈非线性关系，经颗粒直径为46um氧化铝砂纸打磨过对偶面，其材料磨损率最低。     

干滑动条件下45CrNi材料摩擦磨损规律研究

以某自行火炮底座传动箱摩擦副所用材料45CrNi为研究对象，考察了该材料在不同热处理状态下（530℃回火、380℃回火、830℃淬火及原始状态）组成摩擦副时的干滑动摩擦磨损特性。试验结果表明：530℃回火盘和摩始销组成摩擦配副时结合最好，具有较好的摩擦磨损性能，销试样磨损率最小；在较低速度下载荷是影响材料摩擦因数的主要因素，而速度对摩擦因数的影响较小；粘着磨损是材料配副磨损的主要形式。     

润滑油添加剂对聚合物材料摩擦磨损性能的影响研究

利用MM－200型磨损试验机考察了ZDDP对聚合物材料（PTFE、PI及MCPA）－GCr15轴承钢摩擦副摩擦磨损性能的影响。研究发现，液体石蜡及含ZDDP的液体石蜡润滑均可大幅度改善聚合物材料的摩擦磨损性能，且使其摩擦系数比干摩擦时降低一个数量级，摩擦副表面的ZDDP吸附膜均在不同程度上提高聚合物材料的耐磨性，但其对聚合物材料的摩擦性能影响不大。     

摩擦因数对鼓型组合密封圈密封性能的影响

采用ANSYS有限元软件对聚氨酯和丁腈橡胶组成的鼓型密封圈进行数值模拟,研究密封圈材料摩擦因数对鼓型组合密封圈及其密封性能的影响,得到不同工况下鼓型组合密封圈的Von Mises应力、剪切应力和接触应力分布。结果表明:在给定的正常工作条件下鼓型密封圈可以保证良好的密封;密封圈材料摩擦因数的大小对动密封影响较大,较大的摩擦因数会使密封面磨损加快,鼓型密封圈最优的摩擦因数为0.1左右。     

Advanced Friction–Wear Behavior of Organic Brake Pads Using a Newly Developed System

The objective of this study was to investigate the influence of an advanced performance system on the tribological behavior of brake pad material using a specially designed brake pad tester system following standard SAE J-661. The tribological behavior and friction and wear characteristics of the organic brake pad samples were evaluated. During braking tests, the samples, in contact with a cast iron disk, were studied at different disc speeds, temperatures, and braking cycles under a constant pressure. In order to understand the friction and wear behavior, the unworn surfaces, worn surfaces, and wear debris were characterized by means of scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX). Furthermore, the surface characteristics and differences in the wear modes of the brake pad samples were examined. Wear debris was permitted to deform the brake pad surfaces, leading to friction layers and enabling the estimation of the friction behavior of the brake pads. The results showed that the best friction–wear behavior was obtained with lower braking cycles at low speeds and temperature. Thus, the newly developed brake pad tester system proved very effective in evaluating the performance of the brake pad samples.     

Simulation of Temperature Distribution in Disk Brake Considering a Real Brake Pad Wear

This paper presents a methodology for the modeling of the transient thermal behavior of the disk brake of the vehicles using finite element methods. The influence of the wear properties of friction materials on thermoelastic behaviors is investigated to facilitate the conceptual design of the model. The coupled characteristics of the friction heat flow between the disk and pad as well as the effects of the brake disk thermal stress because of the variable applied pressure was considered. At the same time, the model was optimized by the experiment. Repeated brake processes with varying load, sliding speeds and temperature are applied in the simulation of the disk brakes. Experimental dependencies of the coefficient of friction and wear rate on the temperature of brake pad were approximated and applied to the model. The temperature and pressure on the contact surface of the pad/disk brake system obtained for constant and speed/pressure sensitivity applications were confronted and compared. The thermo-distribution is operated to visualize the disk temperature.     

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.     

干摩擦条件下树脂刹车片磨损机制研究

为了优化拖缆机刹车部件的设计参数,同时进一步提高刹车片的耐磨性能,采用MPV-600型磨粒磨损试验机研究无石棉树脂摩擦片和黄铜试样与45#钢配副在干摩擦条件下的摩擦学性能,利用体式显微镜观察试样的磨损形貌并分析其磨损机制。结果表明:摩擦热引起的温升导致的硬度下降及磨损机制的改变是干摩擦条件下摩擦片磨损的主要原因;树脂刹车片的耐热性能、耐磨性能均好于黄铜试样,树脂刹车片与钢配副的摩擦因数主要是由树脂刹车片中的铜纤维材料决定的;干摩擦条件下树脂摩擦片的磨损机制是以磨粒磨损和氧化磨损为主,而黄铜试样以磨粒磨损和黏着磨损为主。     

石油钻机盘式刹车副材料的摩擦磨损性能研究

为提高深井石油钻机盘式刹车副的摩擦学性能和使用寿命,研制开发了新型刹车盘表面堆焊材料和无石棉刹车块摩擦材料,并通过变温摩擦磨损性能实验,研究了刹车副的摩擦学性能。研究表明,刹车副具有良好的变温摩擦特性和高温抗热衰退性能,高温下的摩擦因数比较稳定;刹车块和刹车盘的磨损率均随温度的升高而增大,但刹车盘表现出相对稳定的耐磨性能。载荷对刹车副的摩擦因数影响不大,变化比较平稳;刹车块和刹车盘的磨损率均随载荷的增大而增大,但刹车块表现出相对稳定的耐磨性。刹车副的摩擦因数随滑动速度的增加而增大,并趋向平稳;但速度对刹车块和刹车盘的磨损率影响不大,变化相对稳定。研制的刹车副材料能够满足石油矿场钻机作业的要求。     

Wear mechanism of disc-brake block material for new type of drilling rig

To improve friction and wear performance and service life of the disc-brake pair material of a drilling rig, a new type of asbestos-free frictional material with better performance for disc-brake blocks is developed, and its wear mechanism is investigated by friction and wear experiments. Topography and elementary components of the brake block’s wear surface are analyzed by employing SEM and EDAX patterns, revealing its tribological behaviour and wear mechanism. When the frictional temperature is lower, the surface film of the brake block is thinner, dense, smooth with plasticity, and divided into the mixture area, Feabundant area, carbon-abundant area and spalling area. The mixture area consists of various constituents of frictional pairs without ploughing and rolling trace. The Fe-abundant area mainly consists of iron and other constituents. The carbon-abundant area is the zone where graphite and organic fibre are comparatively gathered, while the spalling area is the zone where the surface film is spalled and its surface is rough and uneven, with a loose and denuded state. During the period of high frictional temperature, the frictional surface is also divided into the mixture area, Feabundant area and spalling area. In this case, the mixture area consists of abrasive dust from friction pairs, and the surface film is distributed with crumby hard granules, exiguous oxide, carbide granules and sheared slender fibre. The Fe-abundant area is mostly an oxide layer of iron with a flaky distribution. Fracture and spalling traces as well as an overlapping structure of multilayer surface films can be easily found on the surface film. The components of the spalling area are basically the same as that of the matrix. At the beginning of wear, the hard peaks from the friction surface of the disc-brake plough on the surface of the brake block. With increasing frictional temperature, the friction surface begins to soften and expand, and oxidized wear occurs at the same time. During the high-temperature wear period, severely influenced by friction heat, obvious softening and plastic flow can be found on the friction surface of the brake block, its anti-shearing ability is weakened, and adhesive wear is intensified. Thermal decomposition of cohesive material in the brake block is simultaneously strengthened, so that constituents shed due to loss of adhesion. Organic fibre is in a flowing state and obviously generates drawing, shearing, carbonization and oxidization. In addition, thermal cracking, thermal oxidization, carbonization and cyclization of organic substances on the surface of brake block can make the friction surface produce pores or cracks, thus fatigue wear occurs.     

Wear mechanism of disc-brake block material for new type of drilling rig

To improve friction and wear performance and service life of the disc-brake pair material of a drilling rig, a new type of asbestos-free frictional material with better performance for disc-brake blocks is developed, and its wear mechanism is investigated by friction and wear experiments. Topography and elementary components of the brake block’s wear surface are analyzed by employing SEM and EDAX patterns, revealing its tribological behaviour and wear mechanism. When the frictional temperature is lower, the surface film of the brake block is thinner, dense, smooth with plasticity, and divided into the mixture area, Fe-abundant area, carbon-abundant area and spalling area. The mixture area consists of various constituents of frictional pairs without ploughing and rolling trace. The Fe-abundant area mainly consists of iron and other constituents. The carbon-abundant area is the zone where graphite and organic fibre are comparatively gathered, while the spalling area is the zone where the surface film is spalled and its surface is rough and uneven, with a loose and denuded state. During the period of high frictional temperature, the frictional surface is also divided into the mixture area, Fe-abundant area and spalling area. In this case, the mixture area consists of abrasive dust from friction pairs, and the surface film is distributed with crumby hard granules, exiguous oxide, carbide granules and sheared slender fibre. The Fe-abundant area is mostly an oxide layer of iron with a flaky distribution. Fracture and spalling traces as well as an overlapping structure of multilayer surface films can be easily found on the surface film. The components of the spalling area are basically the same as that of the matrix. At the beginning of wear, the hard peaks from the friction surface of the disc-brake plough on the surface of the brake block. With increasing frictional temperature, the friction surface begins to soften and expand, and oxidized wear occurs at the same time. During the high-temperature wear period, severely influenced by friction heat, obvious softening and plastic flow can be found on the friction surface of the brake block, its anti-shearing ability is weakened, and adhesive wear is intensified. Thermal decomposition of cohesive material in the brake block is simultaneously strengthened, so that constituents shed due to loss of adhesion. Organic fibre is in a flowing state and obviously generates drawing, shearing, carbonization and oxidization. In addition, thermal cracking, thermal oxidization, carbonization and cyclization of organic substances on the surface of brake block can make the friction surface produce pores or cracks, thus fatigue wear occurs.     

摩擦副组合对摩擦磨损性能的影响

在1：1惯性力矩制动试验台上研究了两种不同石墨形态的铸铁制动盘与两种混杂纤维增强的酚醛基制动闸片配副时的摩擦磨损性能。结果表明，对于某一配方的制动闸片，使用灰口铸铁盘的摩擦副具有较高的摩擦系数，但制动盘表面温度较高，闸片磨损量较大；对于某一种制动盘，使用B配方制动闸片时，制动盘表面的温度较高，但闸片的磨损量较小；在所有四种组合中，B配方制动闸片与灰口铸铁盘配副的瞬时摩擦系数能够完全满足有关技术要求。     

On the dynamics of the friction coefficient

The paper deals with the principal wear mechanism in brake systems and introduces a new dynamical model of the friction coefficient, where necessarily both friction and wear are taken into account. This model explains many open questions on the principal functionality of brake systems.In brake systems, characteristic structures are formed in the contact area by the flow of wear particles. Modulated by the friction power the wear particles are used by the system to build up hard contact patches on the brake pad. Nearly all energetic dissipation of the system is concentrated on these patches. By wear, these contact patches are destroyed after some time.So the friction coefficient is given by the equilibrium of flow of birth and death of contact patches. The resulting dynamical model describes the dynamical behaviour of the friction coefficient and the dependence of the temperature in the friction layer.This theory explains the fading effect of brake systems as well as complex hysteretic effects in the diagram of the friction coefficient versus the velocity, known from instationary measurement procedures.The structure of this theory seems to be quite general to describe other frictional systems too.