Failure analysis of the conductive slide support rod of section insulator
applied in urban rail transport system

城市轨道交通系统的分段绝缘器导电滑动支撑杆的失效分析

Xuemei Xiang, Henglei Zhang * , Feifei Zhang, Zhongyuan Yang, Qiankun Xu, Yueying Zhang

项雪梅、张恒雷 * 、张菲菲、杨中元、徐乾坤、张月英

Abstract: The support rod of conductive slide of a section insulator which was applied in urban rail transport system fractured after operation for about 4 years. The failed section insulator was installed at the turning of the train route. Multiple failure causes had been analyzed utilizing a combination methods of chemical composition analysis, mechanical property test, metallographic examination, macro morphology and microstructure observation.The support rod is made of AISI-304/L/C stainless steel. No obvious microstructure defects are detected in crack origins or the matrix material. The mechanical properties and the chemical composition satisfy the requirement. The failure mechanism of the support rod is proved to be high cycle fatigue fracture (HCF). The main fatigue crack origin locates at the right-angle edge of the arc-shaped transition region of the support rod where stress concentration can be generated easily. In addition, arc discharge-induced cracks can be observed on the local burned surface of the support rod, and they contribute a lot to the fatigue crack initiation. Finally, the alternating load mainly results from the change of train operation direction at the turning position and this change further leads to the direction change of the contact force between pantograph and insulator section. Besides, the impact, vibration and unsmooth contact caused by pantograph also contribute to the alternating load. The conductive slide support rod is fabricated by AISI-304/L/C steel. The chemical composition and mechanical properties satisfy the standard requirement. No obvious metallographic defects are found in crack origins and the matrix material. The failure mechanism of the slide support rod is high cycle fatigue. Fatigue crack initiates at the right-angle edge of the arc transition region where stress concentration can be generated easily to facilitate crack initiation and propagation.

摘要：应用于城市轨道交通系统的一分段绝缘器的导电滑杆在运行约4年后断裂，故障区间位于列车路线的拐弯处。本实验采用了化学成分分析、力学性能测试、金相检验、宏观形貌和显微组织观察的方法进行综合分析，探究导致故障发生的成因。实验表明，导电滑轨为AISI-304/L/C不锈钢材质，断裂源或基体材料处没有明显的微观结构缺陷，且滑杆的机械性能和化学成分均符合应用要求。本实验判定支撑杆的失效机制为高周疲劳断裂( HCF )，成因可细化为以下三部分：首先，主要疲劳裂纹位于支撑杆圆弧过渡区的直角边缘处，而此处易产生应力集中；其次，支撑杆的局部烧损表面有电弧放电裂纹，这些裂纹随后发展为疲劳裂纹；最后，列车在转弯处运行方向的变化导致突变荷载，这种变化进一步改变了受电弓与分段绝缘器间接触力的方向。此外，受电弓引起的冲击、振动和不畅接触也会导致交变荷载。现将实验结论总结如下：导电滑杆为AISI-304/L/C钢制材质，化学成分和力学性能均满足标准要求，裂纹源和基体材料均未发现明显的金相缺陷；滑杆的失效机理为高周疲劳断裂；疲劳裂纹于圆弧过渡区的直角边缘处产生，由于此处易形成应力集中，裂纹因故产生与延伸。

Keywords: Section insulator; High cycle fatigue; Arc discharge-induced crack

关键词：分段绝缘子；高周疲劳断裂；电弧放电裂纹

来源：ELSEVIER

发表时间：2023-04-12

检索：孙莎莎

翻译：谢鑫飞

一审：罗阳

二审：彭莉

三审：罗玲娟

上传发布：姜浩