【作者】 董霖；

【导师】 周仲荣；

【作者基本信息】 西南交通大学 ， 机械设计及理论， 2008， 博士

【摘要】 随着科学技术的进步,社会经济的发展,人类探索领域的不断扩大,遇到了众多特殊工况下的摩擦学问题,高速电气化铁路系统的受流是典型的载流条件下的特殊摩擦磨损问题,目前尚未见到地铁中使用的钢铝复合式第三轨和受电靴的载流摩擦磨损特性及机理的研究。本文通过对销-盘摩擦磨损试验机的夹具和控制部分进行改进,研制了载流摩擦磨损试验装置,并用其首次试验研究了地铁钢铝复合式第三轨与受电靴摩擦副之间的载流摩擦磨损特性。采用扫描电子显微镜(SEM)、电子能谱仪(EDX)、X射线衍射分析仪(XRD)、和表面轮廓台阶仪等微观手段,系统研究了电流、速度、极性、法向压力等对钢铝复合式第三轨与受电靴摩擦副之间的载流摩擦磨损特性,揭示了摩擦副的磨损机制;试验还在CETRUMT-2试验机上用自行设计的夹具,研究了支撑刚度对载流摩擦磨损特性的影响。研究得到的主要结论和结果如下:1、随着电流和速度的增大,磨损体积损失相应增大;电流、法向压力和速度等的综合作用导致摩擦表面的温升,是影响载流摩擦副的摩擦磨损特性的重要因素,相应于温度增大,磨损体积损失增大;表面过渡层中的水膜电解出的氧离子导致受电靴材料的结合力削弱,表面逐渐疲劳而破坏,受电靴接正极时的磨损量略大于接负极时的磨损量;表面轮廓分析表明,钢铝复合轨的磨损量随着速度的增大略有增大,但磨损量比受电靴的销试样小得多,只在微米量级。随着电流的增大,摩擦系数出现较小范围内的波动,有先增大然后减小的趋势;随着速度的增大,摩擦系数减小;不同极性条件下摩擦系数都比较接近,受电靴接正极时的摩擦系数略微较接负极时大。2、载流时摩擦系数随着法向压力的增大呈现出增大的趋势,而无电时摩擦系数随着法向压力的增大呈现出减小的趋势。载流磨损体积损失随着法向压力的增大均呈现出现先快速减小而后缓慢增大的“U”形变化趋势,发现存在一个最佳法向压力,此压力下的磨损体积损失最小,且随着速度的增大最佳法向压力相应增大。建立的磨损量-法向压力-速度三维关系模型(W-F-Vmodel)能与实际的试验结果较好的吻合,它对于载流摩擦磨损系统磨损的定量预测,对于最优磨损条件的确定等都具有积极的意义。地铁第三轨受流时,对应于一定的运行速度,最佳法向压力是最佳的工作压力,此时既能保证顺利受流,又能使得摩擦副材料总损失量较小,从而对确保行车安全,降低维护频率,节约地铁运行成本等都有一定的实用价值。3、钢铝复合轨和受电靴的受电磨损机制主要是机械磨损和电气磨损,四种机械磨损机制分别为粘着磨损、磨粒磨损、氧化磨损和疲劳磨损。电气磨损和机械磨损相互加强,电弧烧蚀导致了比机械磨损大得多的磨损,磨损过程表现为多种机制综合作用的结果。4、变支撑刚度试验结果表明:加载系统的支撑刚度对载流摩擦磨损有影响,不同的支撑刚度条件下,随着载荷降低,载荷的振幅均增大,且弹性加载的载荷振幅总体上小于刚性加载;对变形能的试验揭示了弹簧的摩擦耗能与变形能的比值越大,吸振能力越强,载流磨损量越小。实际载流工况中,采用合理的支撑刚度加载,能较好地降低载荷的振幅,减少电弧烧蚀,保证良好的受流。5、基于摩擦学的三公理,建立了载流摩擦磨损系统构成图和系统过程图,以及载流摩擦磨损电传导电路模型,为载流摩擦磨损的研究奠定了分析基础,能较好的解释电因素对摩擦磨损的作用。研究结果在很大程度上丰富对载流摩擦磨损的研究,对接续的研究工作具有重要的意义。更多还原

【Abstract】 With the progress of science and technology, the development of the economy, and the expansion of exploration field, human being comes across a lot of peculiar working condition tribology problem. Power supply of high speed electric railway is a typical peculiar tribology problem; however the research concerning tribological characteristics of aluminum-stainless steel composite conductor rail and collector shoe used in subway third rail traction system has not been reported so far.In this paper, a new tester by modifying the jigs and the control system of conventional pin-on-disc apparatus has been developed. The friction and wear characteristics of aluminum-stainless steel composite conductor rail and collector shoe have been investigated on the tester with electrical current applied across the sliding interface. The morphologies of worn surfaces have been observed and analyzed by means of scanning electron microscope (SEM) and energy dispersive x-ray spectroscopy (EDX), X-ray diffraction (XRD), and surface profilometer, etc. The tribological characteristics of aluminum-stainless steel composite conductor rail and collector shoe under different electric current, sliding speed, polarity, and normal force have been tested systematically. Effects of bracing stiffness on the friction and wear with electrical current also have been investigated on the modified rig of CETR UMT-2 tester. The main obtained results and conclusions in this dissertation are as follows:1. The results show that the wear volume loss decreases with the increase of electric current and velocity. The current, normal force and sliding speed induce the temperature rises between the friction parts, and these are the key factors influence the friction and wear characteristics. The wear volume loss increases with the rising of temperature. The electrical wear loss has bearing on polarity. Water molecule adsorbed by sliding contact surface decomposed into hydrogen and oxygen ion under the influence of electrical field. The oxidation reaction occurred bewteen positive metal ions (or carbon ions) and negative oxygen ion weakened the bond bewteen the grains in the surface layer. The wear volume loss of a positive collector shoe is larger than that of a negative collector shoe. Surface profile analyse shows that wear volume losses of aluminum-stainless steel composite conductor rail increase with the increase of sliding speed, but the losses are under micron level, which are much less than wear volume losses of the collector shoe. With the increae of current, the friction cofficients fluctate under the less range, with the trend of first enhancing and then diminishing. the friction cofficients decrease with the increase of sliding speed, and nearly equal under different polarity.2、The friction cofficients increase with the increase of normal force under the current, but decrease with the increase of nomral force without current. With the increase of normal force, the electrical wear volume loss firstly decreases greatly then increases slightly in the shape of U. The experiment results show that a optimum normal force exists in friction and wear with electric current, the wear volume loss is least under the optimum normal force, and the optimum normal force increase with the increase of sliding speed. On the basis of tests and analyses, a three demension W-F-V (Wear volume loss-Normal force-Velocity) model are established. The model is fairly fitting of actual test results, and is valuable in the prediction of wear loss under current and the choice of optimum frictional condition. In the real working condtion of three rail, working under the the optimum normal force makes electrical power supply stable and wear loss much less, reduces maintenance frequency, ensures driving safety, and saves subway running cost.3、Mechanical wear and electric wear are major wear mechanism in the friction and wear between aluminum-stainless steel composite conductor rail and collector shoe. The mechanical wear includes adhesive wear, abrasive wear, oxidative wear, and fatigue wear in the tests. Mechanical wear and electric wear enhance mutually, and wear losses caused by electric arc erosion is much larger than those caused by mechanical wear. The wear process shows the results of being a synthetical effect by various mechanisms.4、Tests show that bracing stiffness of loading system has effect on the on the friction and wear with electrical current. Under different bracing stiffness, vibration amplitude of normal force increased with decreasing of the normal force, however, vibrations from the elastic system exhibited less than those from the rigid system. Spring’s ratio of frictional energy to deformation energy has relation with the mass loss of the pair. If the ratio is larger, the wear loss is less. In working condition, selection of appropriate range of normal force and stiffness of spring is necessary to decrease the wear loss induced by arc erosion.5、Based on the three Axioms in Tribology, a system structure map, a system process map, and a electric circuit model are established. These results have established the analytical basis for research in friction and wear with electric current and are significant for the future research.更多还原