某航空电机球轴承过热失效分析与改进研究

Overheat failure mechanism and improvement scheme of ball bearing for aero electromotor

某航空电机在运转实验过程中出现异常噪音,拆解后发现电机轴系两端支撑球轴承已发生过热失效,出现润滑脂碳化、保持架断裂和内外套圈磨损等现象。为了解决某航空电机球轴承出现过热失效的问题,对电机轴系两端轴承进行了失效分析,并提出了改进方案。首先,根据经验对电机轴系两端球轴承进行了故障分析,并提出了多个结构改进方案;然后,采用COBRA AHS软件建立了热-应力耦合的航空电机轴承-转子仿真分析模型,分别对不同的改进方案进行了接触应力和温度场分析;最后,对比了不同条件下的仿真分析结果,得到了轴承过热失效机理,并提出了相应改进方案,结合实验对改进方案进行了验证。研究结果表明:转轴受热变形是导致该航空电机球轴承过热失效的主要原因,转轴受热变形后挤压两端轴承,使得滚动体与滚道之间最大接触应力可达2512.0 MPa;过载条件下,加剧了轴承摩擦生热,导致温度急剧上升,最高可达219.2℃,润滑脂因高温碳化失效,不良的润滑条件使轴承早期失效;将电机两端支撑轴承由深沟球轴承更换为角接触球轴承后,两端轴承最高温度为96.6℃,最大接触应力为1866.1 MPa,即降低了轴承工作温度,提高了轴承轴向承载能力,电机运转寿命超过1200 h。

During the aero electromotor s test operation,abnormal noise was detected.Upon disassembly,it was discovered that the ball bearings at both ends of the electromotor shaft system had suffered from overheating failure,grease carbonization,cage fracture,as well as wear on the inner and outer rings,among other issues.To address the overheating failure problem in the ball bearings of an aero electromotor,a failure analysis of the bearings at both ends of the electromotor shaft system was conducted,and an improvement plan was formulated.Firstly,a failure analysis of the ball bearings at both ends of the electromotor shaft system was carried out based on experience,and several structural improvement options were proposed.Subsequently,a thermal-stress coupled aero electromotor bearing-rotor simulation analysis model was established using COBRA AHS software,and contact stress and temperature field analyses were performed for different improvement schemes.Finally,the results of the simulation analyses under various conditions were compared to derive the overheating failure mechanism of the bearings.A corresponding improvement plan was developed and validated through experiments.The results show that the heat deformation of the rotating shaft is the main cause of overheating failure of the ball bearing of the aero electromotor.The heat deformation of the rotating shaft compresses the bearings at both ends,making the maximum contact stress between the rolling element and the raceway up to 2512.0 MPa.Under overload conditions,the bearing friction heat generation is intensified,resulting in a sharp rise in temperature up to 219.1℃,grease carbonization failure due to high temperature,poor lubrication conditions make the bearing early failure.By replacing the supporting bearings at both ends of the electromotor with angular contact ball bearings,the maximum temperature of both ends of the bearing is 96.6℃,and the maximum contact stress is 1866.1 MPa,which reduces the operating temperature of the bearing,improves the axial bearing capacity of the bearing,and makes the operating life of the electromotor more than 1200 h.