粉煤灰粒径对树脂基摩擦材料性能的影响

采用热压成型的方法制备不同粒径粉煤灰增强酚醛树脂基摩擦材料,研究掺杂不同粒径粉煤灰后摩擦材料的摩擦因数、磨损率和物理力学性能的变化情况,借助扫描电子显微镜观察摩擦材料的磨损表面微观形貌。研究表明:随着粉煤灰颗粒粒径的减小,填充的摩擦材料密度逐渐增加,硬度、抗弯强度、最大应变均呈现出先减小后增加的趋势;摩擦材料的摩擦因数变得较高且稳定,磨耗较低,当中位径小于等于4.70μm时,粉煤灰增强效果比较好。     

The Role of Transfer Layers on Friction Characteristics in the Sliding Interface between Friction Materials against Gray Iron Brake Disks

The effect of transfer layer formation on friction performance was studied using a brake friction material containing 15 ingredients. Based on a base formulation, 13 friction material specimens containing different relative amounts of ingredients were produced and they were tested on gray iron disks using a small-scale friction tester. A non-destructive four-point probe technique to measure electrical resistance of the thin film was used to estimate the transfer layer thickness. Results showed that the transfer layer formation was highly dependent on the relative amount of ingredients in the friction material and temperature. Among various ingredients, solid lubricants and iron powders increased the transfer layer thickness but no apparent correlation between transfer layer thickness and the coefficient of friction was found. Strong influence from individual ingredients was observed, dominating the friction characteristics during sliding. On the other hand, the thick transfer layers on the disk surface tended to reduce the friction material wear and the amplitude of the friction coefficient oscillation during sliding.     

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。     

Lubricant Additives Based on Carbon Nanotubes Produced from Carbon-Rich Fly Ash

Carbon-rich fly ash has been reported to be a suitable precursor and catalyst for carbon nanotube (CNT) growth. In this work, CNTs grown from carbon-rich fly ash were evaluated as a lubricant oil additive to reduce the friction coefficient of metallic surfaces using a ball-on-disk tribometer. Different concentrations of the as-grown CNTs in the range 0.005–0.5 wt% were dispersed in a base sunflower oil. The value of the friction coefficient was also investigated as a function of load. Excellent results were obtained for the value of the friction coefficient, where it drastically decreased to around 58% of its original value without additives. This was achieved at a very low concentration of CNTs; that is, 0.1 wt%. The obtained result was compared with that of a commercial multiwalled CNT at the same concentration and found to be superior. This superiority of CNTs produced from fly ash could be attributed to the existence of active radical sites on their side wall. Moreover, the friction coefficient value was observed to decrease with increasing load, which might be due to the formation of protective graphitic carbon layers on antagonist surfaces. The viscosity of pure and 0.1 wt% CNTs-impregnated base oil was also studied in the 25–100°C temperature range. No significant changes are observed in the viscosity of the CNTs-impregnated base oil. These results suggest that the low-cost CNTs produced from fly ash are excellent nanomaterials as additives for lubricant oil.     

基于人工神经网络的摩擦材料性能评价和预测

基于3种典型的人工神经网络,即Elman(反馈)、BP(前馈)和RBF(径向),分别建立3种制动摩擦材料摩擦性能的评价预测模型,采用[240,8]的数据样本对3种模型进行训练,同时采用贝叶斯正则化训练函数进一步优化。结果表明,Elman网络预测实验数据的精度最高,能较为准确地预测摩擦材料的升温摩擦因数和降温摩擦因数,尤其适用于磨料含量较低的情况。     

四种车辆制动闸瓦材料摩擦特性试验研究

使用MM-1000型摩擦试验机,在不同的压力和速度下作了4种铁路车辆制动闸瓦材料与车轮钢的摩擦试验,测试它们的制动摩擦特性。试验结果表明,闸瓦材质对制动摩擦性能有较大的影响。高磷铸铁A、B两种材料的摩擦因数比较不稳定,在制动过程中摩擦因数出现了较大的波动,而且易受制动压力和速度的影响。高分子树脂复合材料C的摩擦因数比较稳定,受制动速度的影响较小但是受压力的影响较大。高分子树脂复合材料D的摩擦因数受制动速度的影响较大,但是受制动压力的影响则较小。     

Effects of Resin Type and Fiber Length on the Mechanical and Tribological Properties of Brake Friction Materials

In this study, the effects of resin type and fiber length on mechanical properties and friction characteristics of automotive brake materials were studied. Three types of resin, viz. straight phenolic resin (SR), cashew nut shell liquid modified resin (CR), and melamine resin (MR) were used as matrix material. Lapinus with different lengths was used as inorganic fiber. Three series of friction composites composed of nine composites in the form of brake materials were manufactured. Physical, mechanical, and tribological properties of all composites were investigated. The friction tests were performed using a Chase type friction tester. The results showed that both resin type and fiber length played an important role on the mechanical and tribological properties of the friction materials. The highest and the lowest friction coefficient for resin types were recorded for SR and MR composites, respectively, while MR and CR composites showed the highest and the lowest wear resistance, respectively. For the fiber length considered, increasing the fiber length increased the wear resistance of the composites. The coefficient of friction, in general, showed a good correlation with the wear resistance of the composites. But, there was no clear correlation with the mechanical and tribological properties of the composites. The morphological features of worn surfaces and wear debris of the composites were analyzed in order to understand the friction and wear mechanisms of this tribosystem.     

多纤维增强汽车制动器摩擦材料的摩擦磨损特性研究

制备一种多纤维增强汽车制动器摩擦材料。为了解多纤维增强摩擦材料各组分在制动摩擦过程中所起的作用,采用XD-MS定速式摩擦试验机测定所制备的摩擦材料的摩擦磨损性能,通过扫描电镜观测在不同温度下磨损后的表面形貌。结果表明:摩擦材料的摩擦因数比较稳定且在高温时摩擦因数没有显著下降,磨损率也在规定范围内;摩擦材料在低温下主要是磨粒磨损,高温下树脂分解产生热磨损,同时伴随着磨粒磨损和疲劳磨损。     

粉煤灰空心微珠粒径对树脂基复合材料力学与摩擦学性能的影响*

粉煤灰空心微珠具有空心圆球结构,将其用于充填树脂基复合材料,可减少树脂用量、提升复合材料性能,同时促进粉煤灰排放废弃物的高附加值利用。采用不同粒径的粉煤灰空心微珠充填树脂基复合材料,研究不同粒径的粉煤灰空心微珠对复合材料密度、力学性能和摩擦磨损性能的影响。结果表明：随着粉煤灰空心微珠粒径的减小,复合材料的密度呈先降低后增加的趋势,硬度和冲击强度呈先增加后减少的趋势;粉煤灰空心微珠粒径为120~140目时,复合材料密度最小,粒径小的空心微珠更有利于降低复合材料的密度;粒径为80~100目时,复合材料冲击强度最大;采用较大粒径粉煤灰空心微珠充填树脂基复合材料,更有利于提高复合材料的高温摩擦因数,改善树脂基复合材料的抗热衰退性能;粒径20~40目和60~80目粉煤灰空心微珠复合材料具有良好的综合摩擦磨损性能。     

现代制动用刹车材料的应用研究和展望

阐述了现代制动用刹车材料的应用研究现状,分析了现代制动用刹车材料研究和应用中存在的问题,提出了现代制动用刹车材料的研究和应用方向。     

Tribological Characteristics of Binder Resins for Brake Friction Materials at Elevated Temperatures

The heat resistance of the multiphase friction materials made with straight phenolic resin (ST), boron–phosphorous (B–P)-modified phenolic resin (BP), or polyimide (PI) was investigated using a Krauss-type friction tester. Thermal analysis of the cured resins was also carried out to examine the chemical and mechanical properties of the resin and their effects on the wear rate and the coefficient of friction. The results showed that the fade and wear of the friction materials were closely related to the thermal decomposition of the binder resin and durability of the contact plateaus, which were produced by the compaction of wear debris around hard ingredients on the rubbing surface. The friction material containing the B–P modified resin was more resistant to wear and fade than the other binder resins. On the other hand, the friction material with polyimide showed good fade resistance but exhibited excessive wear despite its good thermal resistance.     

Influence of Thermal Fatigue on the Wear Behavior of Brake Discs Sliding against Organic and Semimetallic Friction Materials

ABSTRACT

In this article, brake discs are exposed to high thermal stress, causing thermal fatigue damage. The aim of this work is to study the evolution of the wear behavior of brake disc materials, such as cast iron, chromium steel, and metal matrix composites, under the influence of thermal fatigue. The brake disc specimens are heated and then cooled rapidly. Then, wear tests are carried out using a pin-on-disc-type tribometer. Organic and semimetallic friction materials are used for all wear tests. The results show that thermal fatigue affects the structure of the contact surfaces of all of the disc specimens by increasing their roughness. Furthermore, the wear rate of the friction materials increased, except a reduction of the wear rate is noted for the semimetallic friction material rubbing against cast iron. Moreover, thermal fatigue has no significant influence on the coefficient of friction. The worn surface of the metal matrix composite sliding against semimetallic friction material is characterized by abrasive and adhesive wear mechanisms.     

仿生密度激励的摩擦振动对摩擦学特征的影响

利用ABAQUS仿真模拟往复式摩擦副干摩擦特性,提取摩擦过程中的速度特征,以振动烈度来量化摩擦振动,分析了仿生密度所激励出的摩擦振动对摩擦学特征值的影响。结果表明,由同一种密度的仿生副所产生的摩擦振动、温度、摩擦应力、磨损深度都具有相同的效果,振动烈度—摩擦学特征值曲线呈递增趋势,合理的仿生密度可以起到减振、消磨、降温的作用。     

硼酸酯与聚醚复配水溶液的摩擦学性能研究

水的润滑性能较差,因此需要选取性能良好的水溶性添加剂对其摩擦性能进行改善。研究选取椰油酰胺聚氧乙烯醚(CPOE)和三乙醇胺硼酸酯(BN)作为添加剂,分别对CPOE和CPOE-BN水溶液的摩擦学性能进行研究。使用NGY-6纳米级膜厚测量仪测试两种溶液的成膜性能,结果表明两种溶液在低浓度下均具有良好的成膜能力。利用四球试验机对两种溶液的减摩抗磨性能、稳定性能和极压性能进行了研究,结果表明两种溶液在低浓度下均具有良好且稳定的减摩抗磨性能,BN的加入可以大大提高CPOE水溶液的减摩性能和高载荷下的抗磨性能。利用XPS技术对CPOE-BN磨痕表面的化学元素进行了分析,结果表明在磨痕的表面生成了氮化硼、硼化铁等化合物,起到了良好的减摩抗磨效果。研究表明,CPOE和BN具有良好的协同润滑效果,是一种具有良好工业应用前景的绿色水基润滑添加剂。     

Tribological Properties of Potassium Titanate in the Brake Friction Material; Morphological Effects

The tribological characteristics of brake friction materials containing different shapes of potassium titanate were investigated. They contain typical ingredients of a non-asbestos organic based friction material, including potassium titanate in the shapes of whiskers, platelets, and splinters. A Krauss type friction tester is used to obtain thermal stability and wear resistance of the friction materials at elevated temperatures. The results showed that the morphology of potassium titanate plays an important role in the formation of contact plateaus and transfer films on the rubbing surfaces, which are closely associated with tribological properties. The friction material with splinter shape potassium titanate shows better friction stability and improved wear resistance compared to those containing other types of potassium titanate due to larger contact plateaus and stable friction films at the sliding interface. On the other hand, the transfer films produced by the friction materials with platelet or whisker potassium titanate are not sustainable at elevated temperatures since they are easily detached during sliding, resulting in poor wear resistance.     

高压飞灰过滤器的制造与检验

介绍了煤气化 /煤代油项目中关键设备之一———高压飞灰过滤器的主要结构、主要技术参数及制造检验标准和注意事项 ,并对其主要零部件的加工、制造过程及装配工艺要点进行了重点阐述。     

惯性制动条件对铜-石墨材料摩擦性能及第三体的影响

采用粉末冶金技术制备铜-10%石墨烧结材料,通过GF150D型摩擦试验机,在干摩擦状态及制动压力为0.51 MPa的条件下,研究不同制动方式对材料摩擦磨损性能的影响。结果表明,采用从高速到低速分段制动方式(摩擦方式A)时,随着制动速度降低,摩擦表面形成的致密第三体破碎、剥落,机械啮合力增加,摩擦因数提高;同时,摩擦表面温度下降,基体强度提高,磨损率降低。采用从高速到低速连续制动方式(摩擦方式B)的摩擦因数和磨损量均大于摩擦方式A。     

基于飞灰比电阻检测的烟尘治理管理手段

介绍了某电厂通过飞灰比电阻检测手段加强烟尘治理的经验,提供了国内十多种典型煤种燃烧后的飞灰比电阻检测数据。提出了避免采购高飞灰比电阻煤炭、高飞灰比电阻煤与低飞灰比电阻煤掺烧、利用飞灰比电阻检测手段综合诊断除尘设备缺陷等烟尘治理的精细化管理手段。     

Role of Al2O3 in Semi-Metallic Friction Materials and its Effects on Friction and Wear Performance

In this work the semi-metallic friction composites with moderately increased content of Al₂O₃ (0, 3.4, 5.6, 9.0, and 14.6 vol%) were successfully fabricated by casting technology and their tribological properties were evaluated. The character of friction surfaces was confirmed by SEM. The sample with 5.6 vol% of Al₂O₃ offers the best tribological property among the prepared formulations, and is characterized by high and steady friction coefficient (about 0.45) and low wear. With the temperature increasing, the stibnite patches population on friction surface increases and individual steel fibers spread due to their plastic deformation to form larger primary contact plateaus. The area covered by contact primary plateaus decreases with the alumina content increasing.     

利用钢渣和粉煤灰制备微晶玻璃

以钢渣和粉煤灰为主要原料，采用烧结工艺，制得以透辉石为主晶相的微晶玻璃；介绍了烧结法制备微晶玻璃的过程；通过热分析、X射线衍射、收缩率的测定等分析方法，阐述了烧结法制备微晶玻璃的优越性。此试验为钢渣和粉煤灰等固体废物资源化利用或者提高其利用的附加值开辟了新的途径。