进气道拉紧螺栓断裂分析

机务检查发现飞机左侧进气道横向拉杆的拉紧螺栓发生断裂。对失效拉紧螺栓的宏微观特征和金相组织进行检查，并对其硬度和化学成分进行检测。结果表明:拉紧螺栓断裂性质为疲劳断裂，断裂原因与异常装配预紧力叠加进气道载荷有关。同时针对性提出调整工序顺序、增加专用工装、完善工艺规程等改进措施。通过监控20架飞机的装配过程，并收集部队1年多的飞行反馈信息，未发生同类故障。

Fracture Analysis of Draw-in Bolt in Inlet

A draw-in bolt of the lateral rod at the left inlet of an aircraft was found to have fractured during ground inspection. Macro and micro observation, metallographic examination, hardness testing and chemical composition analysis have been performed to find out the failure cause. The results show that the fracture of the draw-in bolt is fatigue facture, and the fracture was mainly caused by the coeffect of abnormal assembly pretightening load and the load in the inlet. Accordingly, three improvement suggestions were put forward:adjusting procedure, adding special tools, and perfecting process regulations. By monitoring the assembly process of the 20 aircrafts and collecting more than one year's flight feedback, no similar failure has occurred in the outfield.