Research on Fatigue Fracture Failure Mechanism of C2 Pump Connection Head in Aircraft Hydraulic System

This article analyzes the reasons for the failure of the C2 pump connection head in aircraft hydraulic systems. During the flight, the crew reported a low fuel level indication in the system, but there was still a pressure indication before safely landing. Upon inspection, it was found that the hose connecting the C2 pump and pressure component in the middle system was broken at the outlet end of the C2 pump. Through macroscopic observation and analysis, it was found that the fracture occurred at the connection point of the hose outlet joint, where there were changes in the diameter of the pipe wall and stress concentration. Microscopic morphology analysis shows that the fracture surface has fatigue fracture characteristics, divided into flat areas and areas with large fluctuations, with fatigue stripes and dimple structures, indicating low cycle fatigue fracture. The energy spectrum analysis confirmed that the connector material may be Ti6Al4V titanium alloy, and the metallographic structure and hardness analysis further confirmed that the composition and hardness distribution of the material were uniform. Comprehensive analysis suggests that the failure of the connector is caused by fatigue fracture, with the crack originating from the inner side of the pipe wall, propagating along the circumferential direction, and ultimately breaking instantly. The cause of failure may be related to local stress concentration caused by vibration. The conclusion of this article is that the failure of the connector is fatigue fracture. It is recommended to optimize the design and usage environment of the connector to reduce vibration and stress concentration, and improve the reliability and safety of the equipment.