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.     

超深矿井提升机制动盘热性能分析与优化

超深矿井提升机制动盘在紧急制动过程中由于受到摩擦循环热载荷的作用，内部产生较大的热应力，同时高温会导致制动盘和闸片摩擦制动性能下降甚至失效。针对制动盘制动热性能问题，根据热传导理论和有限元分析方法，建立了制动盘组件三维有限元模型，采取直接耦合方法对制动盘制动过程中的热应力场进行模拟研究，并通过实验验证了仿真参数设置的正确性。分析了闸片数量和排布方式对制动工况下制动盘温度和应力分布的影响。结果表明，在制动阶段，制动盘摩擦面温度先急剧上升，后缓慢下降，摩擦面温度呈现锯齿状波动性变化，制动过程中应力变化规律与温度变化规律相同。原制动盘在制动过程中的最高温度为134.8℃，最大应力为230.2 MPa，高温和大应力区域集中于摩擦面附近；增加闸片数量的制动盘最高温度为142.4℃，最大应力为251.1 MPa，高温和大应力区域同样集中于摩擦面附近；改变闸片排布方式的制动盘最高温度为86.5℃，最大应力为119.1 MPa，高温区域和大应力区域范围较小。由此可知，改变闸片排布方式更能显著降低制动盘温度和应力，并且温度场和应力场分布更均匀。研究结果可为制动盘热性能优化设计提供理论参考。     

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。     

超高分子质量聚乙烯纤维增强复合材料研究进展

从不同应用领域复合材料对纤维和基体树脂性能要求的角度,详细综述了近年来有关超高分子质量聚乙烯纤维增强复合材料的研究状况,对UHMWPE纤维表面改性技术、不同类型树脂基体的浸润粘合性以及其它纤维与UHMWPE纤维混杂复合特性进行了比较.     

超高分子质量聚乙烯纤维增强复合材料研究进展

从不同应用领域复合材料对纤维和基体树脂性能要求的角度，详细综述了近年来有关超高分子质量聚乙烯纤维增强复合材料的研究状况，对UHMWPE纤维表面改性技术、不同类型树脂基体的浸润粘合性以及其它纤维与UHMWPE纤维混杂复合特性进行了比较。     

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。     

制动盘早期磨损失效分析

对失效的汽车制动盘进行了扫描电镜分析、化学成分分析、金相检验和硬度检测等。结果表明，制动盘属于早期磨粒磨损失效。对进口和国产的制动盘及制动片进行了对比分析，讨论了材质及摩擦付匹配对制动盘使用性能的影响。制动盘磨损性能的影响因素不仅与制动盘材质有关，更主要是与摩擦片的材质与摩擦副匹配有关。     

混杂纤维复合材料最优纤维混杂比例及其应用研究进展

混杂纤维复合材料以其性能和低成本等优势近期取得了快速发展和应用。纤维混杂比例不仅影响构件的性能,同时关乎成本。本文介绍了混杂纤维复合材料的性能优势,分别对复合材料最佳性能和最佳成本时的纤维混杂比例的研究进展进行了综述,并介绍了混杂纤维复合材料的应用近况,提出了混杂纤维复合材料目前在发展中的不足,对其发展方向进行了展望。     

三维编织超高分子量聚乙烯纤维/碳纤维/环氧树脂混杂复合材料力学行为及混杂效应

采用复合处理工艺对三维混杂超高分子量聚乙烯纤维/碳纤维编织体进行表面处理, 通过RTM工艺制备了环氧树脂基混杂复合材料（UHMWPE/CF/ER）, 并研究了其力学性能及混杂效应。结果表明, 在纤维总体积分数一定的情况下, 随着超高分子量聚乙烯纤维/碳纤维混杂比的减小, 复合材料的弯曲强度、 弯曲模量及压缩强度增大, 而其纵向剪切强度及冲击韧性降低。三维编织混杂复合材料的断裂机制由混杂纤维的混杂比及其性质决定, 通过调节混杂比可实现对复合材料力学性能的有效调控。      

表面改性和混杂对超高分子量聚乙烯纤维/环氧树脂复合材料性能的影响

采用紫外接枝和与芳纶纤维混杂的方式改善UHMWPE纤维的缺点,详细研究了接枝单体种类、浓度和纤维混杂等对UHMWPE纤维/环氧树脂复合材料性能的影响。结果表明,以丙酮为溶剂采用一步接枝法在紫外光辐射下将丙烯酸接枝到UHMWPE纤维表面上,可显著提高UHMWPE纤维增强的复合材料的弯曲强度、冲击强度和拉伸强度;随着接枝单体浓度的提高弯曲强度和冲击强度没有明显的变化,而拉伸强度不断提高。同时,将UHMWPE纤维与芳纶纤维混杂可提高其与树脂基体生成的复合材料的耐热性。UHMWPE纤维与芳纶纤维按1∶1的质量比混杂,混杂纤维增强的复合材料在90℃的形变量比UHMWPE纤维增强的复合材料减少66.7%,显著提高了复合材料的耐热性。     

Performance evaluation of brake pads developed using two different manufacturing methods

The aim is to study the effect of several distinct manufacturing processes, parameters and ingredients on the physical, mechanical and frictional characteristics of brake pad developed using hand lay method (sample 1), brake pad developed using hot compression method (sample 2) and commercial brake pad (sample 3). The non asbestos brake pad samples were compared with the selected commercial brake pad sample using pin on disc test set up. Results showed that friction performances of all three samples were insensitive to water and oil absorption test. Sample 2 had better mechanical properties and greater wear resistance than other two samples which are attributed to use of hot press method of manufacturing the composite and selecting the carbon-based ingredients. Sample 1 maintained high coefficient of friction even though manufactured with the help of hand lay method. Both fabricated brake pads are stable upto the temperature 220 °C without any weight loss and degradation. Brake pad surfaces showed different shape wear debris and plateaus significantly affecting the friction characteristics. Finally, the test results indicated that both fabricated brake pad samples have potential braking characteristics to be used as a brake pad material.     

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。      

无钢纤维摩擦材料的振动噪声试验研究

对自行研制的无钢纤维混杂增强摩擦材料的振动噪声性能进行研究。从频域和时域多个方面,探讨材料的阻尼系数及其他因素对摩擦材料振动及制动噪声的影响;通过对信号的对比分析,研究振动和噪声的关系;探讨汽车刹车片产生振动与噪声的机理及其有效的控制途径。     

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.     

摩擦衬片包角对盘式制动器尖叫影响的仿真分析

摩擦衬片包角对制动尖叫具有重要影响。针对某通风盘式制动器,建立有限元复模态模型并通过尖叫台架试验进行了正确性验证。基于该模型针对5种包角水平的摩擦衬片,通过仿真计算分析其对制动尖叫倾向性的影响,并从制动块自由模态特性、盘块间接触压力分布、不稳定模态频率及模态耦合特性角度解释了不同摩擦衬片包角对制动尖叫的影响机制。分析表明：摩擦衬片包角的改变会同时引起制动块结构特性变化和接触压力分布的变化,进而引起不稳定模态数量、频率和模态耦合特性的改变。     

Analyzing the mechanisms of fatigue crack initiation and propagation in CRH EMU brake discs

A significant number of high-speed electric multiple units’ (EMU) brake discs, manufactured from forged steel, showed thermal cracks during work and NDT. There exist three kinds of cracks on the friction surface; namely, the crackle, radial crack and circumferential crack. Macro-morphologies of the friction surface indicate that the cracks appeared in the interior and edges of the hotspots. Crack growth methods include the single crack propagation and multiple crack connectivity. A finite element analysis (FEA) was performed to determine temperature and stress distribution in the brake disc as well as to estimate stress distribution during braking. Simulation results indicate more significant residual, circumferential tensile stress on the external friction surface after emergency braking. The maximum residual circumferential tensile stress is 200 MPa after 300 km/h emergency braking. In addition, there is only the circumferential compressive stress on a section which is a certain distance from the exterior of the friction surface, and the distance depends on braking conditions. Therefore, not taking into account thickness reduction of the friction surface due to wear, it can be concluded that when the cracks run along the thickness direction to the specified distance, they will cease to run along this direction and begin propagating mainly in the direction of the radius. In addition, based on the simulation results, a measure was presented to prevent and inhibit the crack propagation.     

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.