U型螺栓失效断裂原因分析  

Causes analysis of failure and fracture for U-shaped bolt

作　　者：郑建军 樊子铭 乔欣 ZHENG Jianjun;FAN Ziming;QIAO Xin(Inner Mongolia Power Research Institute,Hohhot Inner Mongolia 010020,China)

机构地区：[1]内蒙古电力科学研究院,内蒙古呼和浩特010020

出　　处：《宁夏电力》2022年第4期66-69,共4页Ningxia Electric Power

基　　金：内蒙古电力科学研究院2020年自筹科技项目(510241200003)。

摘　　要：某汽轮机组在运行过程中空冷岛风叶U型螺栓发生断裂,利用宏观形貌观察、化学成分检测、金相组织观察、断口微观形貌观察及力学性能测试等方法对U型螺栓的断裂原因进行综合性失效分析。研究结果表明,由于螺栓的规格选用存在问题,导致U型螺栓的弯曲半径小于风叶轮毂半径,从而使螺杆内弧侧与风叶轮毂的接触部位因长期磨损而形成应力集中,并诱发疲劳源。同时,U型螺栓1的螺杆内弧与直杆过渡处存在一定程度的弯制残余应力,最终,在拉应力、弯制残余应力及风叶振动所产生的交变应力的综合作用下,疲劳裂纹源加速扩展,导致螺栓的断裂失效。The U-shaped bolts used in fan blade of air cooling island were fractured during the operation of a steam turbine unit,the fracture causes of U-bolts were comprehensively analyzed by means of macro morphology observation,chemical composition detection,metallographic structure observation,fracture micro morphology observation and mechanical properties test.The results show that the bending radius of the U-bolt was less than that of the fan blade due to the problems in specification selection,thus the stress concentrations were formed in the contact site between the inner arc side of the bolt and the fan blade due to long-term wearing,and inducing fatigue source.With the combined action of tensile stress,bending residual stress and alternating stress caused by wind blade vibration,the fatigue crack sources were accelerated expansion and resulted in the fracture failure of U-bolts.

关 键 词：U型螺栓 风叶 应力 疲劳 断裂 

分 类 号：TM621[电气工程—电力系统及自动化]