U型螺栓断裂失效分析  

Fracture Analysis of U-shaped Bolt

作　　者：梁成成 王斌 李海波 LIANG Cheng-cheng;WANG Bin;LI Hai-bo(Department of Mechanical Engineering,Shanxi Engineering Vocational College,Taiyuan 030009,China;Shanxi Provincial Inspection and Testing Center(Shanxi Institute of Standard Metrology Technology),Taiyuan 030009,China)

机构地区：[1]山西工程职业学院机械工程系,太原030009 [2]山西省检验检测中心(山西省标准计量技术研究院),太原030009

出　　处：《失效分析与预防》2024年第2期134-137,148,共5页Failure Analysis and Prevention

基　　金：山西省高等学校科技创新项目(2023L565);山西省教育科学规划课题(GH-220519)。

摘　　要：新开发车型平衡悬架和车桥固定用U型螺栓在整车路试一段时间后发生断裂。基于理化检验的方法,从断裂螺栓断口宏观形貌和微观特征、化学成分、力学性能、硬度、金相组织、断口表面成分等方面进行分析,确定螺栓断裂性质和机理,进而分析断裂原因。结果表明:该U型螺栓断裂性质为高周疲劳断裂。U型螺栓R角与垫板干涉导致R角处表面应力集中,而U型螺栓表面的脱碳使R角处萌生微裂纹缺陷,在交变应力作用下逐渐扩展,最终导致U型螺栓断裂。通过修改模具,优化U型螺栓R角尺寸,严格控制并改善热处理工艺以防止脱碳,以避免裂纹形成。The U-shaped bolt for fixing the balance suspension and axle of a newly developed vehicle broke after a period of road test.Based on the method of physical and chemical inspections,the analyses were performed on the macroscopic morphologies,microscopic characteristics,chemical compositions,mechanical properties,hardness,metallographic structures,and elements on the fractured bolts surface to determine the type and mechanism of bolt fracture,and then explore the cause of fracture.The results indicate that the fracture type of the U-shaped bolt is high cycle fatigue fracture.The interference between the R angle of the U-shaped bolt and the backing plate led to the surface stress concentration at the R angle.The decarburization on the surface of the U-shaped bolt caused the initiation of micro crack defects at the R angle.Under the action of alternating stress,the cracks gradually expanded,and ultimately led to the fracture and failure of the U-shaped bolt.Hence,the formation of cracks could be avoided by repairing the mold,optimizing the R-angle size of the U-bolt,and strictly controlling and improving the heat treatment process to prevent decarburization.

关 键 词：U型螺栓 疲劳断裂 干涉 热处理 脱碳 

分 类 号：TG115.5[金属学及工艺—物理冶金]