某推流器耦合架联接螺栓在运行过程中发生断裂；通过断口形貌观察、化学成分分析、硬度测试、显微组织分析、强度校核及有限元模拟分析了螺栓断裂的原因。结果表明：螺栓发生了疲劳断裂；在螺栓和螺母联接部位第一道螺纹根部的应力集中明显，在交变拉伸载荷作用下，该部位萌生裂纹并发生扩展，直到螺栓断裂；螺栓材料中镍和钼含量偏低、硬度偏高、组织中存在孔洞和夹杂物等缺陷、螺纹根部应力集中明显以及交变应力幅较大是导致螺栓疲劳断裂的主要因素。

A flow booster coupling bracket joint bolt fractured during operation. The reason for fracture of the bolt was investigated by fracture morphology observation, chemical composition analysis, hardness testing, microstructure analysis, intensity check and finite element simulation. The results show that the bolt failed in fatigue fracture. The stress concentration at the root of the first thread at the joint of the bolt and nut was obvious. Under the alternating tension loading, cracks initiated at the spot and propagated until the bolt fractured. The low content of nickel and molybdenum in the bolt material, the high hardness, the defects such as holes and inclusions in the structure, the obvious stress concentration at the root of the thread and the large alternating stress amplitude were the main factors leading to the fatigue fracture of the bolt.