INHERENT VIBRATION DAMPING OF HELICOPTER BLADES.
Interim Technical rept. Jan 68-May 69,
SOUTHWEST RESEARCH INST SAN ANTONIO TEX
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Results are presented of extensive experiments on damping of vibrations in helicopter main rotor blades and compare these results with theoretical and semiempirical methods of predicting blade damping. The feasibility of numerical solution of blade vibration equations which include complex damping effects is demonstrated. Air damping is shown to be relatively unimportant for all but the fundamental bending vibration mode. Structural damping is essentially independent of amplitude but varies significantly with frequency. For much of the experimental data, internal damping of the blade material is the primary source of damping. Author