INFLUENCE OF EXTERNAL DAMPING ON THE STABILITY AND RESPONSE OF A HORIZONTAL ROTOR WITH ANISOTROPIC BENDING STIFFNESS

Design features, such as keyways of blind holes, produce noncircular c ross-sections which introduce anisotropies in the bending stiffness ch aracteristics of rotor shafts. Rotors with appreciable stiffness aniso tropy have been found to exhibit vibrations at one-half the synchronou s frequency. In horizontal single-disk rotors with anisotropic bending stiffness characteristics, gravity induces vibrations at one-half the synchronous frequency. Previous studies have neglected the damping ef fect of the surrounding medium and have Predicted the operation of the rotor in between the two critical speeds to be unstable. This investi gation examines the influence of external damping on rotor response to imbalance of gravity excitations and shows that sufficient amount of damping can suppress the reported instability caused by anisotropic be nding stiffness characteristics.