汽车后悬架纵臂开裂原因分析

Analysis on Cause for Cracking of Automotive Rear Suspension Longitudinal Arm

某汽车在试验场行驶2796 km后发现其QSTE420TM钢后悬架纵臂断裂。对断裂的纵臂进行了宏观检验、化学成分分析、金相检验、硬度检测及有限元模拟。结果表明:后悬架纵臂是多源疲劳断裂,裂纹始于纵臂与轮毂支架的安装面;汽车在运行中紧固螺栓发生了松动,裂纹源处产生应力集中,应力接近材料的屈服强度,从而导致后悬架纵臂开裂。

An automobile was found cracking of its rear suspension longitudinal arm made from QSTE420TM steel after running for 2796 km in a test ground.The macro check,chemical composition analysis,metallographic examination,hardness test,and finite element simulation were performed on the cracked longitudinal arm.The results indicated that(a)the rear suspension longitudinal arm belonged to amulti-source fatigue fracture,the crack originated from mounting surface of the longitudinal arm and hub bracket;and(b)the fastening bolts came loose during the automobile running,and the stress concentrated to such a degree in crack source that the stress approximated to yield strength of the material,thus resulting in cracking of the rear suspension longitudinal arm.