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Abstract

This paper experimentally validates the feasibility of an on-line damage detection capability for helicopter main rotor blades. A previously developed modal-based damage detection methodology is implemented to detect, locate and characterize simulated ballistic damage. The damage detection algorithm is based on an extension to eigenstructure assignment methods which were developed for non-rotating structures. Validation is performed on two separate test structures. The first is a long slender beam rotated in a vacuum. This captures the centrifugal effects while eliminating the aerodynamic loads that are found on an actual blade. The second involves a non-rotating test of full-scale main rotor blades from a Hughes TH-55A helicopter. The combined results demonstrate the possibilities and limitations of a modal-based approach for damage detection of a helicopter rotor blade. In general, it is shown that it is possible to detect damage in the blade if the damage occurs in a region of high modal energy. However, damage in regions of low modal energy are not easily detected with a modal-based approach.

Keywords

eigenstructure assignment damage detection rotorcraft rotor blade modal health monitoring

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Experimental validation of a damage detection technique for helicopter main rotor blades

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