重型汽车后桥轴头断裂分析

FRACTURE ANALYSIS OF THE REAR AXLE END OF HEAVY AUTOMOBILE

某重型汽车后桥轴头发生断裂。通过对失效轴头的断口分析,发现其有明显的疲劳断裂特征。疲劳源出现在零件受力的中性层附近,并且呈多疲劳源。中性层是正常工作条件下受力最小的区域。进一步对样品进行金相检验、化学分析和扫描电镜分析,发现在轴头材料的中性层附近存在着大量的残余缩孔和氧化物夹杂等缺陷,可观察到多处由残余缩孔和夹杂物为起裂源的特征形貌,表明残余缩孔等缺陷是引起材料疲劳断裂的主要原因。

The fracture occurred on the rear axle end of heavy automobile. By means of fracture analysis, we found there are clearly morphology of fatigue fracture. The sources of the fracture are take place from the nearby regions of neutral layer. And it is many sources curvature fatigue fracture feature. But the neutral layer frequently bear the smallest force. So we further made the metaloscopy examination, chemical analysis and electron microscope analysis to the axle end, the results showed there are lots of residual shrinkege cavities and inclusion of oxides in the neutral layer of the raw material. Through SEM we found many places from there the residual shrinkege cavities and inclusion of oxides taken place the sourecs of fatigue fracture. It is indicated that the sources are taken from the middle part of the material. It is the defects such as residual shrinkege cavities and inclusion of oxides in the neutral layer nearby of the raw material made the axle end breakdown.