Impact and Bending of a Rigid-Plastic Fan Blade

Abstract

A rigid-plastic fan blade is subjected to a transverse impact force at the tip in addition to radial centrifugal forces caused by fan rotation. Large and small deflection formulations for inplane bending of the cantilevered blade are calculated and compared. If the effects of centrifugal force are completely considered, the difference between these calculations is shown to be small within the beam. Most of the deflection originates from plastic deformation far from the tip so the large deflection effects near the tip have little influence. The largest curvature is inversely proportional to the centrifugal force, directly proportional to the third power of impact force, and always occurs near the point of impact.