Cause of Fracture on Large Aluminum Alloy Fan Blade

The blade of axial flow fan in a subway tunnel fractured during operation. The causes of fracture on blade were analyzed by means of chemical composition analysis, macro and micro analysis, mechanical property test. The results show that the aluminum alloy fan blade had fatigue fracture. The main reason for the fracture was that there were a lot of coarse oxide inclusions, loose and pinhole defects in the blade, and the root of the blade was the stress concentration area of the blade, the defects on the root of blade led to the initiation of fatigue cracks. Under the action of centrifugal force and aerodynamic force, the root of blade bore tensile force, bending force and torsion force, and the fatigue crack would expand under the action of this composite stress, which eventually led to the rapid fracture of blade.