汽车后桥行星齿轮的断裂分析

Fracture Failure Analysis of Planet Gear in Car Rear Axle

针对车桥差速器行星齿轮断裂问题,采用金相显微镜、扫描电镜分析了断裂齿轮金相组织及微观断口,测量齿轮渗碳层的硬度分布,并采用有限元法模拟了齿轮工况下的动态接触。结果表明:在最大扭矩条件下,轮齿的最大接触应力位于齿根表面位置,其最大接触应力为852 MPa;且齿根部存在的少量游离铁素体,硬度值介于合理工艺范围下限,而且根部有工艺油孔存在,降低其有效承载,导致齿轮疲劳断裂失效。

For the fracture problem of planetary gear in differential mechanism of car axle,the microstructure and micro-fracture of the fractured gear were analyzed by optical microscope and scanning electron microscope,and the hardness distribution of carburizing layer was measured. The dynamic contact under working condition was simulated by the finite element method. The results indicate that the maximum contact stress of gear is 852 MPa and located on the surface of tooth root under the condition of maximum torque,there is a few free ferrite in tooth root and its hardness value is the lower limit in the reasonable technological range,and there is the process oil hole in tooth root,which reduce the effective load to lead the gear to fatigue fracture failure.