Fracture Cause of Flame Tube Fairing in an Aeroengine

Fracture occurred in flame tube fairing of an aeroengine during working process. Fracture causes were analyzed by macro and micro morphology observation, surface quality inspection, metallographic inspection, fatigue test and dynamic stress test. The results show that the fracture mode of the fairing was high-cycle fatigue fracture, and the fatigue crack source was located at the corner stress concentration area of the fairing. Large grain size of original forging of the fairing decreased the fatigue strength, which was one of the main causes for fatigue fracture of the fairing. The load at the corner stress concentration area of the fairing was too large under the action of the maximum vibration stress, which was significantly higher than its dynamic strength reserve. This was another main reason for the fatigue fracture of the fairing. The abnormal axial scratches at the corner stress concentration area of the fairing further increased the stress concentration factor and promoted the initiation of fatigue cracks.