Frictional performance evaluation of newly designed brake pad materials

This work is aimed to study the tribological properties difference of potentially new designed non-commercial brake pad materials with and without asbestos under various speed and nominal contact pressure. The two fabricated non-commercial asbestos brake pad (ABP) and non-asbestos brake pad (NABP) materials were tested and compared with a selected commercial brake pad (CMBP) material using a pin-on-disc tribo-test-rig under dry contact condition. Results showed that friction coefficients for all materials were insensitive to increasing speed and pressure. NABP maintained stable frictional performance as ABP material when contact temperature elevated. Moreover, NABP proved to have greater wear resistance compared to ABP and CMBP materials. Furthermore, the SEM micrographs of brake pad surfaces showed craters which is due to disintegration of plateaus. Finally, the test results indicated that the NABP has the potential braking characteristic for a brake pad material.     

制动盘对盘形制动摩擦性能的影响

在l：l惯性力矩制动试验台上研究了蠕墨铸铁制动盘和灰铸铁制动盘与所研制的合成材料闸片配副时的摩擦磨损性能。结果表明制动盘材质对摩擦性能有很大的影响：所研制的合成材料闸片与灰铸铁盘配副的摩擦副具有较小的速度、压力敏感性，较高的摩擦系数，较低的制动盘表面温度，但闸片的磨损量较大。     

现代轨道交通刹车材料的发展与应用

分析了轨道交通车辆用盘形制动装置中闸片/制动盘组成的摩擦副的工作条件及其对材料的要求,介绍了铸铁闸片、树脂基闸片、铁基和铜基粉末冶金闸片的性能特点及适用领域,重点分析了粉末冶金闸片各组元的功能及摩擦磨损性能调控机制.基于制动盘热斑形成机理,阐明了闸片形状与排布对制动盘热源分布的影响规律.阐述了铸铁、铸钢、锻钢、金属基复合材料和C/C复合材料制动盘的研究进展,并指出了现代轨道交通刹车材料设计与制造的研究热点及研究方向.     

Effects of Mixing the Steel and Carbon Fibers on the Friction and Wear Properties of a PMC Friction Material

Friction, fade and wear characteristics of a PMC friction material containing phenolic resin, short carbon fiber, graphite, quartz, barite and steel fiber were investigated through using a small-scale friction testing machine. Four different friction materials with different relative amounts of the carbon fiber and steel fiber were manufactured and tested. Comparing with our previous work which contained only steel fiber as reinforcement, friction characteristics such as fade and recovery and wear resistance were improved significantly by adding a small amount of carbon fiber. For the mixing of carbon and steel fiber, the best frictional and wear behavior was observed with sample containing 4 weight percentage carbon fiber. Worn surface of this specimen was observed by optical microscopy. Results showed that carbon fibers played a significant role in the formation of friction film, which was closely related to the friction performance. The brake pad with Steel fibers in our previous work, showed low friction coefficient and high wear rate. In addition, a friction film was formed on the surface with a relatively poor quality. In contrast, the samples with mixing the steel and carbon fiber generated a stable friction film on the pad surface, which provided excellent friction stability with less wear.     

提速列车制动闸片的研制

以短切炭纤维、金属纤维等混杂纤维为增强材料制备了适用于我国提速列车客车车辆用的酚醛树脂基盘型制动闸片材料。用扫描电镜检测混料效果，用聚速板制订合理的热压成型工艺参数，用列车台架试验不同制动初速度时紧急制动，常规制动和洒水制动条件下闸片的制动特性。结果表明，研制的提速列车制动闸片材料的机械性能和制动特性指标都达到了我国铁道部门的相应技术要求，其摩擦性能在整个制动过程均十分平稳。     

多纤维增强重型汽车制动器摩擦材料的摩擦磨损性能研究

采用芳纶浆粕、玻璃纤维、硅灰石纤维和钛酸钾晶须多纤维混杂增强制备重型汽车制动器摩擦材料.利用XD-MSM型定速摩擦试验机,考察了摩擦材料的摩擦系数和磨损率随温度变化的情况,并且通过扫描电镜观察了摩擦材料在不同温度下磨损后的表面形貌,分析其摩擦磨损机理.研究结果表明,所研制的摩擦材料具有足够的机械性能和优异的摩擦磨损性能,热衰退小、恢复性能好、耐磨损,可满足重型汽车制动性能的要求.材料在中高温下主要是磨粒磨损和热疲劳磨损,同时伴随着粘着磨损.     

Study of the interaction between microstructure,mechanical and tribo-performance of a commercial brake lining material

The interaction between microstructure, mechanical, and frictional properties of a commercial brake lining material (BLM) was investigated in order to correlate them to braking performance. For this purpose, a Scanning Electron Microscope (SEM) with energy dispersive X-ray (EDX) mapping and spectrum were used to identify and analyze different constituents. The mechanical properties were determined using compression test. Relevant physical properties (density and porosity) were determined using standard test methods. The friction coefficient and wear behavior of the friction material on contact with the grey cast iron disc were established using a pad-on disc tribometer. The results have shown that the brake lining material contains phenol resin such as the matrix and other various ingredients, including silica, rock and mineral filler reinforcement, barium sulfate and carbon-rich particles as filler and brass particles as friction modifier. It had a varied amount and size up to 1 mm for brass particles. The density and porosity were 1.8 g cm⁻³ and 7%, respectively. The investigated material exhibited excellent mechanical properties in the normal solicitation direction. The average friction coefficient was about 0.65, whereas the friction coefficient was stable. The different actions of various ingredients in terms of their effects on the friction and wear behavior of the BLM could be related to their different bonding strengths with the resin matrix and their different abilities to form friction films (third-body layer) on the surfaces of the material and transfer films on the counterpart cast iron surface in relation to the surface temperature evolution and mechanical properties.     

Effect of Different Surface Treatment Methods on the Friction and Wear Behavior of AISI 4140 Steel

In this study,the effects of various surface treatments on the friction and wear behavior of AISI 4140 steel have been evaluated.Sample surfaces of AISI 4140 steel were treated by quenching,carburizing,boronizing and plasma transferred arc (PTA) modification.The microstructural characteristics of surface treated steel samples were examined by optical microscopy and scanning electron microscopy (SEM).The mechanical properties of the samples including the surface roughness,microhardness,and abrasive and adhesive wear characteristics were also evaluated.Wear tests were applied by using a block-on-disc configuration under dry sliding conditions.The wear behavior and friction characteristics of the samples were determined as a function of sliding distance.Each sample group was compared with the other sample groups,and it was observed that the carburized samples demonstrated the lowest weight losses;however,PTA-treated samples demonstrated the lowest coefficient of friction in comparison to the other sample groups at the same sliding distance.     

玄武岩纤维对汽车摩擦材料性能的影响

在一种成熟的配方基础上,采用热压法制备玄武岩纤维增强摩擦材料,研究了汽车摩擦材料中玄武岩纤维含量(质量分数,%)对摩擦材料物理性能、力学性能、摩擦磨损性能及制动噪音的影响。结果表明:随着玄武岩纤维含量增加,摩擦材料的气孔率和洛氏硬度增加,密度和压缩变形量降低,内剪切强度先增加后降低;名义摩擦系数与最低摩擦系数随玄武岩纤维含量的增加而提高;添加适量的玄武岩纤维有利于降低磨损和抑制制动噪音的产生,随其含量增加,磨损量和噪音发生概率先降低而后增加;玄武岩纤维含量在12%时,内剪切强度最高,磨损量最小,噪音表现最佳。     

C/C刹车盘快速致密化工艺及其性能

为了缩短C/C刹车盘制备周期并提高其性能,介绍了一种制备C/C飞机刹车盘的快速致密化工艺,即采用天然气与丙烷气的混合气体为炭源气体的等温压差CVI法。与常规致密化工艺（丙烯气为炭源气体的等温压差CVI法）相比,C/C刹车盘的CVI(Chemical vapor infiltration) 时间缩短了一半,其导热性能提高5%以上,拉伸、压缩、弯曲与剪切性能提高10%以上,摩擦磨损性能提高20%以上。      

钛酸钾含量对汽车摩擦材料性能的影响

钛酸钾是替代石棉用于摩擦材料中的一种新兴增强材料。以一种低金属陶瓷配方为基础,采用粉末冶金法制备钛酸钾增强摩擦材料,研究钛酸钾含量(质量分数,%)对摩擦材料的物理性能、力学性能、摩擦磨损性能及制动噪音的影响。结果表明,随钛酸钾含量增加,摩擦材料的气孔率增加,密度降低,pH值增加;洛氏硬度增加,压缩性及内剪切强度降低;摩擦系数稳定性增强,磨损量先降低后增加;噪音发生频次先降低后增加。钛酸钾含量为12%时,磨损量最低,噪音表现最佳。     

化学气相沉积碳／碳复合材料性能研究

分析了化学气相沉积碳／碳（Ｃ／Ｃ）复合材料的刹车力矩和刹车速度的关系曲线及影响因素，结果表明，刹车力矩一刹车速度曲线上的初始力矩峰值随着摩擦界面温度的升高而增大，提高材料的石墨化度、改变刹车盘的结构、降低刹车比压的施加速度都可以降低初始力矩峰值，改善Ｃ／Ｃ材料的摩擦性能．Ｃ／Ｃ复合材料具有良好的自润滑性能，其磨损率仅为１．２×１０－３ｍｍ／次．它们具有较高的机械性能和热物理性能，完全可以满足飞机刹车的要求．     

Preparation, Properties and Application of C/C-SiC Composites Fabricated by Warm Compacted-in situ Reaction

Carbon fibre reinforced carbon and SiC dual matrices composites (C/C-SiC) show superior tribological properties, high thermal shock resistance and good abrasive resistance, and they are promising candidates for advanced brake and clutch systems. The microstructure, mechanical properties, friction and wear properties, and application of the C/C-SiC composites fabricated by warm compacted-in situ reaction were introduced. The results indicated that the composites were composed of 50-60 wt pct carbon, 2-10 wt pct residual silicon and 30-40 wt pct silicon carbide. The C/C-SiC brake composites exhibited good mechanical properties. The value of flexural strength and compressive strength could reach 160 and 112 MPa, respectively. The impact strength was about 2.5 kJ·m^-2. The C/C-SiC brake composites showed excellent tribological performance, including high coefficient of friction (0.38), good abrasive resistance (1.10 μm/cycle) and brake steadily on dry condition. The tribological properties on wet condition could be mostly maintained. The silicon carbide matrix in C/C-SiC brake composites improved the wear resistance, and the graphite played the lubrication function, and right volume content of graphite was helpful to forming friction film to reduce the wear rate. These results showed that C/C-SiC composites fabricated by warm compacted-in situ reaction had excellent properties for use as brake materials.     

滑动速度对碳纳米管-银-石墨复合材料电磨损性能的影响

采用粉末冶金法制备了碳纳米管-银-石墨复合材料,研究了圆周速度对复合材料摩擦系数、磨损量的影响。结果表明,当压力一定时,随着速度的加快,机械磨损的摩擦系数减小,而电磨损的摩擦系数增大;复合材料的电磨损量远远大于机械磨损的磨损量,电磨损时磨损量在V=10m/s处出现最小值,而机械磨损的磨损量随速度的加快而减小。     

Sensitivity series and friction surface analysis of non-metallic friction materials

Nine non-metallic friction material formulations contained fibers, fillers and binder without strong abrasives were designed using Golden Section sequence combined with least-square method. Seven ingredients used without strong abrasives were selected based on the combinatorial approach. Wear (w) and coefficient of friction (μ) are expressed as a function of volume fraction of the ingredients selected as and . The formulations were optimized using the sensitivity series obtained from least-square method. An optimized formulation (S-10) was obtained with a total wear loss of 6.69 wt% and an average μ of 0.375. Friction surface of both brake pad and disc was observed using SEM, EDX and XRD. The non-metallic friction materials without abrasives exhibit unique friction performance and phenomena compared with the non-metallic friction materials with abrasives and semi-metallic brake linings. The temperature measured during friction is lower and the oxidation of the cast iron disc is not rigorous.     

SiC颗粒增强铝基复合材料制动盘的研究

采用半固态搅拌熔炼-液态模锻工艺制备了与Santana轿车前制动器相匹配的SiC颗粒增强铝基复合材料制动盘,对该制动盘进行了材料拉伸性能和微观结构分析,并在SCHENCK制动试验台上进行了制动性能和制动磨损试验。结果表明,复合材料的拉伸性能优于传统制动盘材料HT250铸铁;在各种制动工况条件下,复合材料制动盘对制动衬片的摩擦系数均在大众公司企业标准规定的范围之内,且较稳定;此外,复合材料制动盘质轻、耐磨,制动噪音小、温升低,运转平稳;因此,可望以其替代传统的铸铁制动盘,提高制动器的安全可靠性和服役寿命,减轻轿车悬挂系统的重量,降低油耗。      

Asbestos free friction composition for brake linings

An asbestos free friction material composite for brake linings is synthesized containing fibrous reinforcing constituents, friction imparting and controlling additives, elastomeric additives, fire retarding components and a thermosetting resin. The composite shows exemplary friction characteristics and has great resistance to wear and shows good temperature stability.     

碳/碳-碳化硅复合材料的摩擦磨损行为与机理

以液相渗硅工艺为手段制备了C/C-SiC复合材料。分别采用MMW-1A与MM-1000型试验机对复合材料的摩擦磨损性能进行了研究。结果表明: 在实验室条件下, 当压力恒定在0.48 MPa时, 转速对复合材料的摩擦磨损的性能影响甚微, 摩擦系数为0.15~0.16, 且磨损率接近; 当转速恒定在0.3 m/s时, 不同压力条件下的摩擦系数相近, 为0.13~0.15, 但磨损率存在较大差异, 材料磨损以磨粒磨损为主。在近工况条件下, C/C-SiC复合材料的摩擦系数达到0.50, 磨损率达到5.95 mg/次, 摩擦曲线表现为典型的马鞍形曲线, 试验前期材料磨损主要表现为磨粒磨损, 试验后期为粘着磨损。     

C/C/Cu及C/Cu复合材料摩擦磨损行为比较

采用无压熔渗工艺制备一种新型的具有优异耐磨性能的碳纤维整体织物/炭/铜(C/C/Cu)复合材料,在UMT23多功能摩擦磨损测试仪上考察复合材料的摩擦磨损行为,并与粉末冶金方法制备的滑板用炭/铜(C/Cu)复合材料进行了对比分析。结果表明：C/C/Cu复合材料形成了连通状的网络结构,其导电性能及力学性能明显优于传统C/Cu复合材料;2种复合材料摩擦系数相近;2种复合材料及其对偶的磨损率随载荷增大而增大;与C/Cu相比,C/C/Cu的耐磨性较优,且对对偶损伤较小,在70N载荷下更为明显。连通状的网络结构及磨损表面形成的磨屑保护层是C/C/Cu复合材料具有良好摩擦磨损特性的主要原因。     

Wear Modalities and Mechanisms of the Mining Non-asbestos Composite Brake Material

The mining brake material is generally made of composite materials and its wear has important influences on the braking performance of disc brakes. In order to improve the braking reliability of mine hoisters, this paper did some tribological investigations on the mining brake material to reveal its wear modalities and mechanisms. The mining non-asbestos brake shoe and 16Mn steel were selected as braking pairs and tested on a pad-on-disc friction tester. And a SEM was used to observe the worn surface of the brake shoe. It is shown that the non-asbestos brake material has mainly five wear modalities: adhesive wear, abrasive wear, cutting wear, fatigue wear and high heat wear. At the front period of a single braking the wear modality is mainly composed of some light mechanical wear such as abrasive, cutting and point adhesive. With the temperature rising at the back period it transforms to some heavy mechanical wear such as piece adhesive and fatigue. While in several repeated brakings once the surface temperature rises beyond the thermal-decomposition point of the bonding material, the strong destructive high heat wear takes leading roles on the surface. And a phenomenon called friction catastrophe (FC) occurs easily, which as a result causes a braking failure. It is considered that the friction heat has important influences on the wear modalities of the brake material. And the reduction of friction heat must be an effective technical method for decreasing wear and avoiding braking failures.