杆形轴锥孔开裂的失效分析

Analysis on Cracking Failure of Conical Hole of Rod Shaft

为了探究某卡车杆形轴锥孔位置开裂的原因,对其断口形貌、化学成分、力学性能和微观组织进行了检测。结果表明:杆形轴的化学成分、显微组织、力学性能符合技术要求。断裂属于明显的疲劳断裂,裂纹起源于锥孔内壁的腐蚀坑。对裂纹源进行能谱分析,发现具有较多的O、Si、Ca、Fe元素,锥孔内由于含湿的灰尘、颗粒杂质的进入形成了缝隙腐蚀,导致锥孔内壁具有较多的腐蚀坑,这些腐蚀坑割裂了基体,形成了应力集中,造成了早期的疲劳失效。相应的改进措施是在锥孔的外侧密封盖上加上自锁装置,从而解决了开裂问题。

The fracture morphology,chemical composition,mechanical properties and microstructures of the cracked conical hole of rod shaft were examined.Results showed that the chemical composition,microstructure and mechanical properties matched the technical requirements.Fracture belonged to obvious fatigue fracture.Cracks originated from corrosion pits in the inner wall of cone holes.EDS results of crack sources showed that there were more O,Si,Ca and Fe elements.Crevice corrosion formed in the inner wall of cone holes due to the entry of wet dust and particle impurities,which resulted in more corrosion pits in the inner wall of cone holes.These corrosion pits split the matrix and formed stress concentration,which resulted in early fatigue failure.In order to solve the cracking problem,the corresponding improvement measures were to add self-locking device on the outer sealing cover of the cone hole.