Bending frequency of a rotating beam with an elastically restrained root

Upper and lower bounds of the fundamental bending frequency of a rotating uniform beam with an elastically restrained root are obtained by the Rayleigh's and minimum principles, respectively. It is shown that the fundamental bending frequency of the rotating uniform beam with rotational flexibility only is always higher than that of the nonrotating beam. If the setting angle is not equal to zero, the fundamental bending frequency of the rotating uniform beam with translational flexibility can be less than that of the nonrotating beam, and the phenomenon of divergence instability (tension buckling due to the centrifugal force) may occur. Finally, the influence of hub radius, setting angle, rotational speed, and elastic root restraints on the fundamental bending frequency of the beam is also investigated numerically by the transfer matrix method.