High cycle fatigue fracture of the extension was proved by means of examination of metallurgical quality, heat treatment, fitting clearance as well as macro-and micro-aralysis of the fracture.

• 通过对断裂叶片的材质、热工艺、装配间隙的复查和断口的宏观、微观分析，证明叶片延伸段的断裂属于高周疲劳断裂；