Abstract: Aiming at the fracture problems of the wheel flange lubrication device hangers during the service of metro vehicles, the fracture mechanism was studied by a method of combining material and dynamic stress tests with finite element simulation, and a new structural design scheme was proposed. Firstly, through the comprehensive analysis and characterization of the micro/macro fractures of the hanger, the mechanism causes of fatigue fractures were determined from the material point of view. Secondly, combined with dynamic stress tests and cumulative damage theory, the fatigue damage values at the key positions of the hanger fractures were calculated, and the structural causes of hanger fractures were determined from the perspective of line tests. Thirdly, the finite element model of the hangers was established, and the static and fatigue strength simulations were performed based on EN13749 standard. The rationality of the structural design was judged from the theoretical point of view, and compared with the results of material and line test analyses. Finally, the improvement scheme of hanger structure was proposed and verified by simulation and dynamic stress tests. The results show that the hanger fractures are due to low stress and high cycle fatigue, the source of fatigue is located inside the stiffener fillet weld, and the cumulative damage values and material utilization rates of the stiffener fillet weld are both greater than 1. The main cause of the hanger fractures is that the stiffener fillet weld bears frequent alternating loads due to unreasonable structure, and have unfazed defects. The welding quality is improved by changing the structures and materials of hangers, and the standard requirements of on-line operations for the flange lubrication devices are met.

Key words:  , metro vehicle, fatigue fracture, cumulative damage, simulation analysis, line test

摘要： 针对地铁车辆服役过程中出现的轮缘润滑装置吊架断裂问题，采用材料和动应力试验与有限元仿真相结合的方法开展断裂机理研究，提出了一种新型结构设计方案。通过对吊架断口微/宏观的全面分析与表征，从材料角度确定疲劳断裂的机理成因；结合动应力试验和累计损伤理论，计算吊架断口关键位置的疲劳损伤值，从线路试验角度确定吊架断裂的结构成因；建立吊架的有限元模型，基于EN13749标准对其进行静强度和疲劳强度仿真，从理论角度判别结构设计的合理性，并与材料和线路试验分析结果进行对比分析；最后，提出吊架结构的改进方案，并进行仿真和动应力测试验证。结果表明：吊架断裂成因为低应力高周疲劳，疲劳源位于加强筋角焊缝内部，且加强筋角焊缝的累计损伤值和材料利用率均大于1；吊架断裂的主要原因为，结构不合理导致加强筋角焊缝承受较为频繁的交变载荷且焊缝存在未熔合缺陷；通过改变吊架结构和材质，提高了焊接质量，达到了轮缘润滑装置在线运行的标准要求。

关键词: 地铁车辆, 疲劳断裂, 累计损伤, 仿真分析, 线路试验