The forced vibration of turbomachinery blading induced by torsional vibration of the rotor shaft is investigated. Torsional shaft vibrations, caused for example by disturbances in the electrical network, jeopardize the long blades in low pressure stages of steam and gas turbine generator rotors. A simple finite element model consisting of beam elements is used to calculate free and forced vibration. A parameter study has been performed to show the influence of design parameters like mass relation and eigenfrequency relation of the uncoupled system parts. The vibration analysis of a large steam turbine generator rotor is presented.

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