Showing papers on "Tip-speed ratio published in 1953"
TL;DR: In this article, the role of resonant bending, particularly in the second and third bending modes, has been observed to play in determining the beam bending moments experienced by the test blades, and the contribution of higher mode bending to the total bending moment may be as great as the sum of the steady, first and second harmonic terms usually considered in current blade analysis methods.
Abstract: Results obtained from flight tests of a family of main rotor blades, similar in all respects except flapwise bending stiffness, are reviewed with the objective of pointing out the role that resonant bending, particularly in the second and third bending modes, has been observed to play in determining the beam bending moments experienced by the test blades. I t has been found that in certain critical conditions the contribution of higher mode bending to the total bending moment may be as great as the sum of the steady, first and second harmonic terms usually considered in current blade analysis methods. The source of the forces exciting the resonance has not been determined; however, it appears to be of aerodynamic origin. The results call attention to the influence resonant bending may have in determining, from the fatigue point of view, the structural life of rotor blades. Since the blade resonant frequency in the second mode will, in general, lie between four and five times rotor speed and in the third mode between six and nine times rotor speed, the number of stress cycles experienced by the rotor blades will include corresponding multiples of the rotor rotation.
7 citations