提速客车转向架安全吊座疲劳失效机理与改进方法

分析了提速客车转向架安全吊座孔附近产生的疲劳裂纹特征, 提出共振现象造成的结构振动疲劳是该部位产生裂纹最主要原因的假设; 通过有限元仿真得到安全吊杆的前110阶模态振型, 分析了各阶模态频率; 进行线路实测加速度与动应力试验, 得到等效应力、加速度及其主频, 并与有限元仿真结果进行对比分析; 在掌握了安全吊座失效机理的基础上, 通过结构改进与调整连接方式优化安全吊杆结构及其固定方式; 对新结构进行线路实测试验, 并对其安全性与经济性进行评估。研究结果表明: 受普通客车运行线路条件影响, 安全吊杆振动频率(加速度主频为91.78 Hz, 动应力主频为91.00Hz) 与有限元计算的第4阶模态频率(95.79Hz) 相近而产生共振; 安全吊杆的纵向加速度功率谱密度远大于其横向值与垂向值, 这与列车的运行方向相吻合, 因此, 振动疲劳使得安全吊座孔边产生裂纹; 在螺栓孔两侧增加5mm厚垫片, 并且将安全吊杆由钢板折弯结构更改为钢丝绳柔性结构能够最大程度降低螺栓孔处等效应力幅值, 减少疲劳损伤累积; 改进后的安全吊杆满足1 200万公里的使用要求, 取得较好的经济效果。 

Fatigue failure mechanism and improvement method of safety suspender mounting base of speed-up passenger car bogie

The fatigue crack characteristics in the vicinity of bolt hole on the safety suspender mounting base of speed-up passenger car bogie were analyzed.A hypothesis was proposed that the structural vibration fatigue caused by resonant phenomena is the most important reason of the crack initiation in the position.The first 1-10 order modes' vibration shapes of safety suspender were obtained by using finite element simulation.The frequency of each order mode was analyzed.Field tests on acceleration and dynamic stress were conducted.The equivalent stresses and accelerations as well as their dominant frequencies were obtained.Field test results were compared and analyzed with FE simulation result.Based on the command of failure mechanism of safety suspender mounting base, the structure of safety suspender and the way of connection were optimized by using structure improvement and connection adjustment.Field line tests were applied to the new structures, and the safety and economy were evaluated.Analysis result showsthat because of the influence of track line conditions of normal passenger car, the vibration frequency of safety suspender, which is 91.78 Hz for acceleration and 91 Hz for dynamic stress, is very similar to the fourth order mode frequency (95.79 Hz) calculated by FE simulation, so that the resonance occurs.The longitudinal acceleration power spectral density of safety suspender is much higher than its lateral value and vertical value, which corresponds to the running direction of train, so crack initiation in the vicinity of safety suspender mounting base is resulted from vibration fatigue.The equivalent stress amplitudes can reduce effectively while placing 5 mm shims on both sides of bolt hole and altering the steel plate bending structure with flexible wire rope structure, and less fatigue damage accumulates.The improved safety suspender can meet the application requirement of running 12 million kilometers, and economic benefit is better.