Estimation of rotor blade torsional deformations from measured blade torsion moments

The strain pattern analysis (SPA) method is applied to estimate rotor blade torsional deflections. The SPA technique requires calculated mode shapes for the tested rotor blade and strain measurements from the rotor's wind tunnel or flight test. The Holzer method is developed to calculate the required mode shapes from rotor blade stiffness and mass properties and the torsional equation of motion. The Holzer method is tested with numerous theoretical and experimental cases and is proven accurate. The strain measurements are from wind tunnel tests conducted by the Army, NASA, United Technologies Research Center (UTRC) and Sikorsky at DNW with a (1:5.73) model-scale UH-60A rotor blade with an advance ratio of 0.301, an advancing tip Mach number of 0.8224 and an average Reynolds number of 1,278,729. The SPA method predicts slightly larger torsional deflections that compare well with the overall trend and range of UTRC static method integrated deflections. The SPA method was evaluated to determine the tolerance to change in the number of measurements and the modes applied, errors in the measurements, and errors in rotor blade stiffness and mass properties. The method is tolerant to all effects except a decrease in the number of measurements and modes.
http://archive.org/details/estimationofroto109456003
Captain, U.S. Army
U.S. Army (USA) author
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