不同表面形貌的接触线对浸金属碳滑板载流摩擦磨损性能的影响

在受电弓-接触网载流摩擦磨损过程中,接触线会产生不同的横截面形状,而接触线形貌的改变可能会影响弓网间的接触关系,进而影响弓网间的载流摩擦磨损性能。为研究不同表面形貌的接触线对浸金属碳滑板载流摩擦磨损性能的影响,利用环-块式高速载流摩擦磨损试验机,研究载流条件下常规形貌、麻点形貌、斜切形貌的接触线与浸金属碳滑板的摩擦磨损性能,比较采用不同形貌接触线时的摩擦因数、电弧能量和浸金属碳滑板的磨损量、表面形貌。试验结果表明：在直流电情况下,常规接触线与浸金属碳滑板组成的摩擦副的摩擦因数最小,滑板磨损量最低;采用斜切形貌接触线时的摩擦因数最大,滑板磨损量最大。通过SEM电镜观测浸金属碳滑板表面的磨损形貌,发现接触线为常规形貌时,滑板以氧化磨损为主,有较多的氧化物产生;接触线为麻点形貌时,滑板以电弧烧蚀和磨粒磨损为主,产生了细小裂纹和烧蚀坑,有较多的磨屑和剥落层出现;接触线为斜切形貌时,滑板以电弧烧蚀为主,有大裂纹和犁沟产生,并且烧蚀区域出现了较多的白色小球。研究表明,当接触线的形貌发生改变时,会导致滑板磨耗增加并加剧接触副电弧放电,从而恶化接触副的状态。因此,当接触线磨损变形严重时,应及时进行更换...     

地铁刚性弓网系统接触线磨损特性试验研究

为研究地铁刚性接触网系统接触线磨损的规律,以地铁刚性接触网系统常用的浸金属碳滑板/铜银合金接触线作为摩擦副,通过模拟地铁弓网系统运行参数,使用载流摩擦磨损试验机研究有、无电火花放电情况下,浸金属碳滑板与铜银合金接触线直流电滑动过程中磨损量、摩擦因数、载流效率随滑动距离的变化。试验结果表明：电火花放电会使得接触线与浸金属碳滑板磨损量显著上升,出现电火花放电时摩擦因数较小,弓网系统载流效率会明显降低同时出现大幅波动。试验后对碳滑板和接触线表面形貌的观察可知：电火花放电会使得浸金属碳滑板表面烧蚀坑数量和尺寸大小增加,同时会出现滑板材料大面积剥落和表面裂纹增多的问题,接触线表面形貌变得更加粗糙。     

电压对碳滑板磨损性能和温升的影响

在受电弓/接触网高速载流摩擦磨损试验机上试验研究恒定电流及不同电压下,纯碳滑板与铜银合金接触线载流滑动摩擦时,接触压力和相对滑动速度对纯碳滑板磨损性能和温升的影响。试验结果表明:随着试验电压的增加,弓网间的电弧放电现象更加明显,燃弧时间更长,磨损率先急剧增大后趋于平缓,纯碳滑板的磨损率与温度表现出正强相关性。分析纯碳滑板磨损后的形貌可知:随着试验电压的增加,纯碳滑板的磨损先以机械磨损为主,然后转变为以电弧烧蚀和氧化磨损为主;纯碳滑板表面的电弧烧蚀坑增多且分布较均匀,烧蚀区面积增大。     

几种受电弓滑板/接触线材料载流摩擦磨损行为的比较

在销-盘摩擦磨损试验机上研究浸金属碳/纯铜、纯碳/不锈钢、浸金属碳/不锈钢、纯碳/纯铜4种受电弓滑板/接触线的载流摩擦磨损性能。结果表明:浸金属碳/纯铜的摩擦因数比其他3对配副的摩擦因数都大,且其配副的碳滑板材料磨损量比其他3对配副的磨损量都高;4对配副的主要磨损机制是电弧烧蚀、磨粒磨损和氧化磨损,而浸金属碳/纯铜还出现黏着磨损。浸金属碳/纯铜因磨损严重,且电滑动中发出异常噪声,应避免作为受电弓滑板/接触线材料。     

不同铜含量浸金属碳滑板的载流摩擦磨损性能*

为研究不同铜含量的浸金属碳滑块的载流摩擦磨损性能,在环-块试验机上研究3种不同铜含量(铜质量分数分别为1.17%、27.8%、50.45%)浸金属碳滑板与铜银合金接触线在载流条件下的摩擦磨损性能,并比较不同电流情况下的材料磨损表面形貌的变化。结果表明:铜含量对浸金属碳碳滑板的摩擦磨损性能有不同的影响。其中铜质量分数为1.17%的材料在200 A小电流情况下整体磨耗量较小,但是在400 A大电流情况下,电弧热、焦耳热产生的500℃左右高温会导致材料气化、掉块,严重加剧材料的损耗;铜质量分数为50.45%的材料在小电流情况下磨耗最大,但材料的运行温度整体较低,即材料的散热性能较好;铜质量分数为27.8%的材料在小电流与大电流情况下综合磨损性能最好。与铜银合金线对磨时,铜含量较高的材料出现了较为明显的黏着磨损,铜含量越高的材料其黏着磨损现象越明显。     

地铁受电弓碳滑板冬季异常磨耗特点微观研究

以国内某地铁线路在冬季运行中出现异常磨耗的受电弓浸铜碳滑板为研究对象，借助多种微观测试手段，比较其表面形貌、微观组织、化学成分等与正常磨耗状态的碳滑板表面的差异，探究碳滑板出现异常磨耗的原因及机制。结果表明：与正常磨耗状态碳滑板相比，异常磨耗状态下碳滑板表面三维形貌崎岖且粗糙，其接触条件显著恶化，机械磨损、磨粒磨损、电弧烧蚀、材料转移等形式的磨损量均有增加；在进入秋冬季节后，碳滑板表面润滑条件发生改变、磨粒数量增加、直径增大、接触副温度上升，从而加剧了磨粒磨损和电弧烧蚀，造成碳滑板出现异常磨耗现象。对地铁运营过程进行跟踪监测后发现，碳滑板异常磨耗的出现与隧道内环境湿度的下降存在一定关联。     

120～170 km/h条件下碳滑板/铜接触线摩擦磨损性能试验研究

在环-块式高速摩擦磨损试验机上,试验研究电流I=100～300 A、滑动速度v=120～170 km/h和法向载荷Fn=100～200 N条件下纯碳滑板/铜接触线的摩擦磨损性能.结果表明:无电流时,碳滑板磨损率很低,一般不超过0.001 4 g/km,但摩擦因数较高,一般在0.30以上.加入电流后,碳滑板的磨损率明显增加,达到无电流时磨损率的10倍多;而摩擦因数明显降低,一般在0.24～0.30间波动.观察碳滑板磨损形貌发现,无电流时磨痕面积较小,随着电流的增加磨痕面积不断增大;且磨损面出现电弧烧蚀的黑色流线和麻点.滑动速度、法向载荷对碳滑板摩擦磨损性能影响较小,而电流作用引起的高温磨损和电弧烧蚀是导致碳滑板材料磨损加剧的主要因素.     

大电流对碳滑块/铜银合金接触线载流摩擦磨损性能的影响

在高速载流摩擦磨损试验机上研究速度为150 km/h、接触压力为60~120 N试验工况下,200~500 A大电流对纯碳滑板摩擦磨损性能的影响。结果表明:在低电压大电流的载流条件下,铜银接触线和纯碳滑板间主要以短弧放电为主,放电面积大、电弧输出能量高;碳滑块的磨损形式主要以电弧烧蚀、剥离、熔融、汽化为主,机械磨损较小;碳滑板的磨损量、电弧能量随着电流的增大而急剧上升;摩擦因数随着电流的增加先增加后减小;当电流不变时弓网间的电弧能量随着接触压力增加呈先增加后减小的趋势,磨损量则随着接触压力的增加而减小。     

接触压力对碳滑板/铜接触线载流摩擦磨损性能的影响

控制电流为250 A,滑动速度为160 km/h,在接触压力50,70,90,110,130 N下,在环-块式载流摩擦磨损试验设备上进行接触压力对碳滑板/铜接触线载流摩擦磨损性能的影响试验,用光学显微镜对滑块的磨损形貌进行观察.结果表明:随着接触压力的减小,滑块的磨损形貌由以较光滑磨损面为主过渡到以受电弧飞溅影响磨损面和多麻坑磨损面为主,主要磨损形式由磨粒磨损过渡到电弧烧蚀磨损,摩擦因数的过渡阶段逐渐明显,稳定阶段的摩擦因数逐渐增大;碳滑板的磨损率随着试验的进行进入稳定期,稳定期磨损率随着接触压力的增加先减小后增加,呈“U”形分布;接触压力的增加可以降低电弧功率和离线率;从碳滑板的磨损率和载流稳定性综合考虑,90 N为最佳接触压力.     

基于磨耗稳定态的高性能摩擦磨损实验机研制

电气化铁路中电力机车靠受电弓滑板与接触网导线的滑动接触来获取动力,它们之间的摩擦接触状态直接影响到机车的运行速度和牵引力,同时其摩擦磨损性能决定了机车连续运行的时间和接触网导线的使用寿命.实际应用中二者构成了一对机械与电气耦合的特殊摩擦副,它们之间的磨耗过程是1个非常复杂的物理化学过程.通过研究发现,机车在正常运行过程中,滑板与接触网导线在运行一段时间以后会出现1个磨耗量较低、磨耗率相对稳定的阶段,在该阶段中摩擦副表面有一层光亮的膜层,称此时为磨耗稳定态,磨耗稳定态对磨擦副的性能及运行寿命具有重要的影响.为了对受电弓滑板与接触导线的载流磨耗特性进行实验研究,分析磨耗稳定态出现的规律,制作了1台高性能摩擦磨损实验机.实验机实验参数调节范围宽,测量精度高,功能强,也可用于电刷和电机滑环等滑动电接触实验.     

A procedure for the wear prediction of collector strip and contact wire in pantograph–catenary system

The effects of friction and electrical phenomena like arcing and sparking govern the wear rate in the sliding contact between the contact wire and the collector strip, these two effects are mutually interconnected in a complex manner. A means of investigating the wear of the collector strip and the contact wire is to carry out laboratory tests that allow to perform comparative tests between different material combinations and to establish the dependence on the main parameters such as sliding speed, contact force and current intensity. A problem to be considered in the application of the laboratory test results is their extrapolation to the real operating conditions, in order to assess the effective benefit among different solutions. In this paper, a procedure that combines a wear model for the contact between collector strip and contact wire with the simulation of the dynamic interaction between pantograph and catenary is proposed. The adopted wear model is based on the wear map concept, including the effect of electrical current flow, and it is tuned by means of the results obtained on laboratory test rig.The dependence of the electrical contact resistance on the contact force between each contact strip of the pantograph and the contact wire of the overhead line is considered and the corresponding electrical current on each of the two collectors of the pantograph is evaluated. Instantaneous values of contact forces and electrical current are then fed into the wear model and the amount of the wear of the collector strips and of the contact wire along the overhead line is calculated, generating an irregular profile of the contact wire.The proposed procedure is applied to two cases: in the first one the wear of the contact wire using copper collector strips and graphite collector strips for dc line are compared. In the second one, the consequence of the variation of the mechanical tension of the contact wire on the wear levels is predicted.     

Effect of metallised carbon content of collector strip on the wear of contact wire–collector strip pair in railway systems

Among the topics related to the interaction between the contact wire of the overhead line and the collector strip, the wear that takes place at the contact interface, depending on both electrical and mechanical quantities, represents an important aspect of maintenance costs, affecting the mean lifetime of collectors, in terms of travelled kilometers (in terms of tenth of thousands), and contact line duration, in terms of years (between 15 and 40). Due to its importance in the global maintenance of both rolling stock and infrastructure, this topic deserved the attention of several regulations in the last decade. In order to investigate the effects of electro-mechanical wear on both contact wire and contact strip, a new test equipment has been designed and installed at Politecnico di Milano. A series of tests have been performed, involving different kinds of collector strip materials and contact conditions, tested at varying speeds and current intensities. This investigation concerned different collector strip configurations intended for 3kV D.C. lines. The combination of different contents of copper and metallised carbon in the collector has been found to influence the wear rate of both collector strip and contact wire. Differences in wear up to four times for the former and up to six times for the latter have been found depending on the composition of the collector. Copyright © 2006 John Wiley & Sons, Ltd.     

Effect of arc discharge on the wear rate and wear mode transition of a copper-impregnated metallized carbon contact strip sliding against a copper disk

Wear of the contact strip on the pantograph of electric railway vehicles is governed mainly by arc discharge occurring simultaneously with break of contact between the strip and trolley wire. As a step to clarify the wear mechanism of metallized carbon contact strips under the occurrence of contact break arc discharge, a detailed sliding wear test of 30 min duration was carried out for the combination of a copper-impregnated carbon strip and a copper disk at a sliding speed of 100 km/h. The worn surfaces of the strip and disk were observed every 5 min. The voltage drop and electric current were measured throughout the test, and the occurrence and energy of the arc discharge were evaluated for each revolution of the disk. The wear process is considered in terms of the wear mode transition, and the effect of arc discharge on the mode transition and wear rate of the strip is discussed.     

四环素牙摩擦磨损行为的研究

在往复滑动摩擦磨损试验台上以钛合金为对磨材料,考察了不同染色程度四环素牙的摩擦学性能,并与正 常恒牙进行了比较。结果表明:轻度四环素牙的摩擦磨损行为接近正常恒牙,磨损以擦伤和轻微犁削为主;重度 四环素牙的摩擦系数变化波动较大,稳态值较高,磨斑表面呈现显著犁沟和剥落,摩擦学特性逊于正常恒牙。四 环素牙的耐磨性随其染色程度加深而降低。     

刚性接触网中浸金属碳滑板在不同法向载荷下的载流摩擦磨损性能

为了更好地模拟浸金属碳滑板的实际应用工况,设置试验滑动距离为1 000 km,使用环-块式载流摩擦磨损试验机模拟地铁列车在刚性接触网系统中的运行条件,研究浸金属碳滑板在不同法向载荷作用下的载流摩擦磨损性能。试验结果表明：随着法向载荷的增大,摩擦因数不断增大,电弧能量下降,载流效率不断升高,滑板的温度以及磨损率都呈现出下降的趋势;随着滑动距离的增加,滑板的磨损率逐渐降低最后趋于稳定。SEM电镜观察结果表明：法向载荷较低时,浸金属碳滑板表面产生了较多烧蚀坑和裂纹,其磨损形式主要表现为电弧烧蚀以及片状剥落;随着法向载荷增大,滑板表面出现划痕和磨屑,磨粒磨损现象较为明显。研究表明：适当增大法向载荷可以有效抑制电弧的烧蚀作用,减少滑板表面的裂纹和烧蚀坑,从而降低滑板的磨损。     

Experimental study on arc ablation occurring in a contact strip rubbing against a contact wire with electrical current

A series of tests on arc discharge were carried out to better understand the wear mechanism of a contact strip rubbing against a contact wire with electrical current. The arc discharge process was recorded with a high-speed camera. The arc voltage drop and electric current were measured throughout the test. The accumulated arc discharge energy was evaluated. Experimental results show that the wear rate of the contact strip is approximately directly proportional to the accumulated arc discharge energy in logarithmic coordinates. Increasing the normal force can suppress arc discharge and decrease wear of the contact strip.     

滑板倾斜对碳滑板/纯铜接触线高速滑动摩擦磨损性能的影响

使用环-块式高速摩擦磨损试验机,试验研究在交流电场中滑板倾斜对电弧放电以及碳滑板/纯铜接触线高速滑动摩擦磨损性能的影响。结果表明,电流为100 A时,碳滑板材料的磨损量随着接触压力和滑板倾斜角度的增大而逐渐减小,试验盘每转平均放电能量也随着接触压力和滑板倾斜角度的增大而逐渐减小,碳滑板磨损率随着电弧能量的增大而增大;当滑板有倾斜角时,在弓网电滑动摩擦过程中会出现受电弓与接触线分离的状态,且滑板倾角越大,分离的时间就越长,这种现象影响列车受流质量和运行平稳性。因此实际弓网系统中要避免滑板倾斜角过大,滑板倾角应小于2°。