50CrVA电机轴断裂原因的分析

利用体视显微镜、光学显微镜（OM）、扫描电镜（SEM）及能谱分析（EDS）等对某厂机车电机轴断裂原因进行了综合分析。结果表明：电机轴非金属夹杂物在2.0级以上，并且裂纹发生部位均发现非金属夹杂物，非金属夹杂物促进了疲劳裂纹的萌生，使得电机轴在交变应力作用下发生了疲劳断裂；电机轴两端内花键同心度较差，致使电机轴在传递扭矩的同时受到较大弯曲应力，是电机轴失效的外在因素。

Analysis on fracture cause of 50CrVA motor shaft

The fracture reason of electric motor shaft in one factory was analyzed by means of stereoscopic microscope， optical microscope （OM）， scanning electron microscope （SEM） and energy dispersive X-ray spectroscopy （EDS）. The results showed that the nonmetallic inclusions of motor shaft were above Grade 2.0. The nonmetallic inclusions were found in all sites of cracking， which accelerated the initiation of fatigue crack. As a result， the fatigue fracture of electric motor shaft occurred under the action of alternating stress. The concentricity of internal spline of motor shaft at both ends was poor， leading to large bending stress while transmitting torque， which was the external factor for motor shaft failure.