HXD1机车牵引电机转轴组件断裂失效分析

HXD1型电力机车的牵引电机转轴和小齿轮轴采用圆锥过盈配合传动结构(下称转轴组件),使用中该组件出现了早期断裂失效.本文通过理化检测、断口和配合面宏/微观形貌观察等失效分析技术对失效组件进行了分析.结果表明,材料成分、组织和显微硬度正常,小齿轮轴和电机转轴的失效形式分别为高周疲劳断裂和微动疲劳断裂.造成组件失效的原因和过程是,小齿轮轴近齿端油槽-油孔交界线处有较大的结构应力集中,油槽底部周向加工刀痕造成附加应力集中,在应力集中和旋转弯曲疲劳载荷作用下油孔边两个应力集中点萌生了疲劳裂纹并扩展;随小齿轮轴裂纹的不断扩展转轴组件结构刚度减小,继而诱发了与小齿轮轴匹配的电机轴配合面的微动疲劳,电机轴疲劳裂纹萌生于微动区的边缘处;电机转轴先于小齿轮轴完全断裂.基于本文的分析结果提出了提高组件抗疲劳断裂的技术措施.

Fracture failure analysis of the pulling motor revolving shaft subassembly of HXD1 locomotive

The pulling motor revolving shaft subassembly of HXD1 locomotive produced early fracture failure, which is interference fits composed of a gear shaft and a motor shaft. Physical test, chemical test, macroscopical morphology and microcosmic morphology analysis for the fractured surfaces and interference fit surfaces are performed. It shows that, with proper chemical composition, microstructure, and micro?hardness, the gear shaft is high cycle fatigue fracture and the motor shaft is fretting fatigue. The failure causation and procedure are that, the structure stress concentration at the inter?spot of the oil groove and oil hole close to the gear conjunction with the additional stress concentration due to hoop machine mark on the oil groove surface contributed to the fatigue crack initiation at the both stress concentration points of the gear shaft;and then, the increased fatigue cracks of gear shaft reduced the coupling stiffness of subassembly, which gave rise to fretting between the surfaces of crack?corresponding interference fits, hence, fretting brought fatigue cracks nucleation sites at the micro?cracks induced fretting at the edges of bedding;the motor shaft fractured clearly prior to the gear shaft. Recommendations for improving anti?fatigue performance of subassembly were suggested based on the failure analysis conclusion.