基于实测载荷谱的重载铁路货车车钩钩尾框剩余寿命预测

随着我国重载铁路货车运行规模及开行频次的增加, 车钩钩尾框断裂破坏问题日益严重. 本文以国产16/17型车钩钩尾框(锻造E级钢)为研究对象, 首先通过系统的材料试验获得了锻造E级钢的基本力学性能和断裂性能参数; 其次建立了含初始裂纹缺陷的钩尾框有限元模型; 最后基于实测线路载荷谱, 采用NASGRO方程开展了伤损钩尾框剩余寿命预测. 计算结果表明: 当裂纹形貌比a/c为0.8, 0.5, 0.3时计算得到的车钩钩尾框剩余寿命逐渐减小, 疲劳裂纹从深度2 mm扩展至20 mm的计算剩余寿命分别为36, 32, 26万公里, 均不足一个段修期; 3种裂纹形貌比下裂纹扩展至12 mm后的剩余寿命占比均较小, 仅为总剩余服役里程的4.7%, 4.0%, 2.2%, 因此可将12 mm作为钩尾框损伤容限止裂判据较为合理; 为研究近门槛区对裂纹扩展寿命的影响, 当裂纹形貌比为0.5且初始裂纹的尺寸降低至0.5 mm时, 裂纹将处于裂纹扩展门槛区附近, 剩余服役里程约为156万公里, 约为2 mm初始裂纹的4.9倍, 跨越了三个段修期. 论文研究结果可为重载铁路货车钩尾框检修周期的优化提供基本参考. 

REMAINING LIFE ASSESSMENT OF HOOK TAIL FRAME IN RAILWAY HEAVY-HAUL WAGON BASED ON REAL LOADING SPECTRUM

With the increase in the operation scale and frequency of China heavy-haul railroad wagons, the failure fracture problem of hook tail frame is becoming more and more serious. In this work, domestic 16/17 type hook tail frame (forged E-grade steel) was used as a research object, the basic mechanical properties and fracture performances of forged E-grade steel were firstly obtained by systematic material tests; secondly, a finite element model of the hook tail frame with initial crack defects was established; finally, the remaining life prediction of the damaged hook frame was calculated by using the NASGRO equation based on the measured loading spectrum. The results show that when the crack shape ratio of 0.8, 0.5, 0.3, the calculated remaining life of the hook tail frame gradually decreases, and the calculated remaining life of the fatigue crack propagation from 2 mm to 20 mm is 360000 km, 320000 km and 260000 km, respectively, all of which are less than one depot maintenance period; the remaining life ratios of the three profile ratios are small after crack expansion to 12 mm, which are only 4.7%, 4.0%, and 2.2% of the total remaining serviceable mileage. Therefore, it is reasonable to take 12 mm as the damage tolerance of the hook tail frame for stopping crack. To investigate the effect of near threshold area on crack propagation life, reducing the initial crack size to 0.5 mm with a shape ratio of 0.5, when the crack is near the crack propagation threshold area, the calculated remaining service mileage increases to 1.56 million km, which is 4.9 times of the initial crack of 2 mm, including three maintenance periods. These results can provide a basic reference for the optimization and strategy of the inspection interval of the hook tail frame widely used for railway heavy-haul railroad wagons.