Tribological surfaces of organic brake pads

Despite the enormous amount of testing and development of automotive brakes and brake pad materials, rather little is known about their tribological contact situation on a microscopic level. The sliding of an organic brake pad against a grey cast iron rotor is very different from most tribological systems. When worn against the rotor, the complex structure and very inhomogeneous composition of the pads results in a particular surface structure, with large contact plateaus rising a few micrometers above the rest of the surface [Wear 232 (1999) 163; Wear 2000 (submitted for publication); Proceedings of the Nordtrib 2000, vol. 2 (2000), 358]. The present investigation involves a more comprehensive study of the formation, mechanical properties and composition of the tribological surfaces of such pads, using high resolution scanning electron microscopy, nanoindentation, energy dispersive X-ray analysis and three-dimensional profilometry using white light optical interferometry. The observations are discussed and correlated to observed friction phenomena.     

硼酸酯型汽车制动液的研制和开发

以硼酸酯为主体,含有润滑剂、黧剂和添加剂的ＨＺ３、ＨＺ４型汽车制动液,具有优良的高温抗气阻性、良好的低温流动性,对金属无腐蚀,对橡胶不溶胀,能保证汽车行驶安全。     

SF3102C型108t矿用自卸车制动气路研究分析

分析了矿用自卸车的四套制动气路的工作原理,并根据不同环境温度下压缩空气中水蒸气因饱和而凝结成水并结冰的程度大小,找出了在中国北方矿山里矿用自卸车制动气路在严冬发生堵塞的原因;最后,为了使制动气路能被更好地执行制动过程,作者给予了合理的建议和解决办法。     

ZSQ型弹簧制动松闸器的开发

在介绍松闸系统的设计原则、主要结构特点的基础上 ,阐述了其试验及应用效果 ,指出该技术是一项新的高效松闸技术     

Effect of advanced injection timing on the performance of rapeseed oil in diesel engines

Combustion studies on both diesel fuel and vegetable oil fuels, with the standard and advanced injection timing, were carried out using the same engine and test procedures so that comparative assessments may be made. The diesel engine principle demands self-ignition of the fuel as it is injected at some degrees before top dead centre (BTDC) into the hot compressed cylinder gas. Longer delays between injection and ignition lead to unacceptable rates of pressure rise with the result of diesel knock because too much fuel is ready to take part in premixed combustion. Alternative fuels have been noted to exhibit longer delay periods and slower burning rate especially at low load operating conditions hence resulting in late combustion in the expansion stroke. Advanced injection timing is expected to compensate these effects. The engine has standard injection timing of 30°C BTDC. The injection was first advanced by 5.5°C given injection timing of 35.5°C BTDC. The engine performance was very erratic on this timing. The injection was then advanced by 3.5°C and the effects are presented in this paper. The engine performance was smooth especially at low load levels. The ignition delay was reduced through advanced injection but tended to incur a slight increase in fuel consumption. Moderate advanced injection timing is recommended for low speed operations.     

Effect of reinforcement volume fraction and size distribution on the tribological behavior of Al-composite/brake pad tribo-couple

Tribological behavior of aluminium matrix composite (AMC)/brake pad tribo-couple under dry sliding conditions was studied using Pin-on-Disc machine. Brake pad material was used as pins while the AMC formed the rotating disc. Series of experiments were performed to characterize the tribological nature of the tribo-couple. Load and sliding speeds were varied over a range to represent actual braking conditions in passenger cars. Effect of volume fraction and size distribution of reinforcement on wear and friction coefficient has been studied. It was observed that a heterogeneous tribo-layer was formed over the worn surfaces during the wear tests. Presence of tribo-layer was believed to cause two effects: acting as a lubricant layer and acting as a source of wear debris. Morphology and topography of worn surfaces and debris were studied using scanning electron microscope (SEM), electron probe micro analyzer (EPMA), and X-ray diffraction (XRD) techniques. When the reinforcement in the matrix has wide size distribution, wear rate and friction coefficients are found to be higher compared to composite containing mono-size reinforcement.     

双绕组电动机能耗制动接线方式、直流磁势分析

通过对双绕组电动机能耗制动与普通三相异步电动机能耗制动的对比,在定子绕组中通入相同数值的直流电流条件下,得出结论：在通入大小相等的直流电流,双绕组电动机产生的直流磁通势是普通三相异步电动机直流磁通的两倍。介绍了双绕组电动机能耗制动两套绕组的4种不同的电气接线方式,每种电气接线的直流磁通势大少不同,两套绕组的等效电阻也不同。生产实践中可以根据生产工艺对制动转矩大小和制动时间长短的不同要求,选择一种理想的电气接线。     

BRAKE TEST OF SiCp/A356 BRAKE DISK AND INTERPRETATION OF EXPERIMENTAL RESULTS

Material properties are obvious different between aluminum matrix composites and iron and steel materials. After the brake disk braked at the same speed, the average temperature of the aluminum brake disk is 1.5 times as high as one of iron and steel brake disk, the thermal expansion value of the aluminum brake disk is 2 times as big as one of iron and steel brake disk. Mechanical property of the material decreases with the temperature increasing generally during braking, on the other hand, the big thermal stress in the brake disk happens because the material expansion is constrained. Firstly, the reasons of the thermal stress generation and the fracture failure of brake disks during braking are analyzed qualitatively by virtue of three-bar stress frame and sandwich deformation principles in physic, and then the five constraints which cause the thermal stress are summarized. On the base of the experimental results on the 1:1 emergency brake test, the thermal stress and temperature fields are simulated; The behavior of the fracture failure is interpreted semi-quantitatively by finite element analysis. There is the coincident forecast for the fraction position in term of the two methods. In the end, in the light of the analysis and calculation results, it is the general principles observed by the structure design and assembly of the brake disk that are summarized.     

煤矿带式输送机运行中的问题研究

分析研究了煤矿带式输送机运行中存在的问题,并指出如何采取相应的措施,以保证带式输送机的正常运行.     

Utilization of unattended methyl ester of paradise oil as fuel in diesel engine

Engine tests have been carried out with the aim of obtaining the performance, emission and combustion characteristics of a diesel engine running on methyl ester of paradise oil (MEPS) and its diesel blends. From the emission analysis it was found that there was a significant reduction in smoke and hydrocarbon emissions by 33% and 22% respectively for MEPS 50 blend and 40% and 27% reductions for MEPS 100. However, there was an increase of 5% and 8% NO_x emission for MEPS 50 and MEPS 100 respectively. Brake thermal efficiencies of MEPS and its diesel blends are slightly lower than that of std. diesel. From the engine analysis, it was found that the performance of MEPS and its diesel blends were similar to that of std. diesel.