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某公司生产的汽车发动机悬置支臂安装成车后运行20公里发生断裂,对断口进行宏观观察和扫描电镜观察,分析了材料的化学成分和金相组织。结果表明:断口分为平坦区、细区和粗区三个部分。其中平坦区为疲劳裂纹起始和扩展区,属于疲劳区;细区和粗区为断裂区,粗区的断裂速度比细区更快。因此,支臂断裂属于疲劳破坏。从支臂断件上取样做疲劳模拟实验,再现了实物断口上的平坦区特征,进一步证实了平坦区属于疲劳断裂。
A company’s car engine mount arm installed into the car after 20 km of rupture, macroscopic observation of the fracture and scanning electron microscopy, analysis of the chemical composition and microstructure of the material. The results show that the fracture is divided into three parts: flat area, fine area and coarse area. The flat areas are the fatigue crack initiation and extension area, belonging to the fatigue area; the fine area and the coarse area are the fracture areas, and the coarse area is faster than the fine area. Therefore, arm breakage is fatigue damage. Fatigue simulation experiments were taken from the specimen of the arm and the flat area characteristics of the physical fracture were reproduced, further confirming that the flat area belongs to the fatigue fracture.