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Failure analysis of fractured motor bolts in high-speed train due to cardan shaft misalignment
Engineering Failure Analysis ( IF 4 ) Pub Date : 2021-01-22 , DOI: 10.1016/j.engfailanal.2021.105246
Yongxu Hu , Andy Chit Tan , Chen Liang , Yanping Li

Motor of high-speed train is normally connected with suspending devices through bolts. This paper presents an investigation of six motor connecting bolts, based on GB/T 3077 standard and strength grade of 8.8, which fractured at the thread close to the contact surface of motor and suspending device before the designed service life. The investigation includes macro examination, chemical compositions analysis, tensile tests, hardness tests, metallographic examinations were used to analyze the cause of fracture. The results revealed that the strength and material of bolts met the standard, no metallurgical defect was found in examination, and the bolts fractured were due to alternating load. According to the spectrum of acceleration signal measured by the sensor mounted on the motor housing and subsequent inspection of the cardan shaft and rotor of motor, revealed the alternating load is caused by misaligned cardan shaft. Further dynamic analysis shows that the rotation of misaligned cardan shaft resulted in huge unbalance force. To confirm the findings, finite element analysis on the bolts subjected to pre-tensile load reveals that the materials at the bottom surface of the first thread suffered high alternating stress and reaches the fatigue limit. From the above findings, this paper proposes an innovative strategy to avoid similar accidents of high-speed train suspending devices.



中文翻译:

万向轴未对准导致高速列车电动机螺栓断裂的故障分析

高速火车的电动机通常通过螺栓与悬挂装置连接。本文根据GB / T 3077标准和强度等级8.8对六种电机连接螺栓进行了研究,这些螺栓在设计使用寿命之前在靠近电机和悬挂装置接触面的螺纹处断裂。调查包括宏观检查,化学成分分析,拉伸试验,硬度试验,金相检查,以分析断裂原因。结果表明,螺栓的强度和材料均符合标准,经检查未发现冶金缺陷,螺栓在交变载荷作用下断裂。根据安装在电动机外壳上的传感器测得的加速度信号频谱,以及随后对万向轴和电动机转子的检查,发现交变载荷是由万向轴未对准引起的。进一步的动力学分析表明,万向轴不对中的旋转导致巨大的不平衡力。为了证实这一发现,对承受预拉伸载荷的螺栓进行的有限元分析表明,第一根螺纹底表面的材料承受高交变应力并达到疲劳极限。基于以上发现,本文提出了一种创新的策略来避免高速列车悬挂装置发生类似事故。进一步的动力学分析表明,万向轴不对中的旋转导致巨大的不平衡力。为了证实这一发现,对承受预拉伸载荷的螺栓进行的有限元分析表明,第一根螺纹底表面的材料承受高交变应力并达到疲劳极限。基于以上发现,本文提出了一种创新的策略来避免类似的高速列车悬挂装置事故。进一步的动力学分析表明,万向轴不对中的旋转导致巨大的不平衡力。为了证实这一发现,对承受预拉伸载荷的螺栓进行的有限元分析表明,第一根螺纹底表面的材料承受高交变应力并达到疲劳极限。基于以上发现,本文提出了一种创新的策略来避免高速列车悬挂装置发生类似事故。

更新日期:2021-02-15
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