Failure analysis of generator rotor fan blades

The failure analysis of a generator rotor fan blade was investigated by mechanical analysis and metallurgical examination of fracture surface. Fracture took place at the airfoil root, surface examination showed that the blade had cracked by a high cycle fatigue mechanism. However, there was no evidence of material defect. A series of analytical, finite element and experimental analysis was utilized to determine the steady-state stresses and dynamic characteristic of the blade. Possibly the failure was due to aerodynamical disturbances that resulted in a state of resonant condition of vibration. The simulation of blade with final crack showed the stress intensity factor (SIF) under these condition exceed the critical SIF and final fracture could be occurred under analyzed stresses.