Vibrations which occur in a geared - rotor system operated at high speed are commonly classified into the torsional vibration and flexural vibration. The former is principally due to the resonance of the mesh frequency and natural frequency of the system. The latter is mainly due to the unbalanced mass of rotors. There are many papers which deal only with the torsional vibration or flexural vibration in a geared - rotor system seperately. However since the force between gears along the path of contact is determined by the relative lateral and torsional displacement of the gears and the force of flexural vibration at the same time. In this study, a finite element analysis program is developed to calculate the modal parameter of geared rotor bearing system. In order to optimize the performance of the program, modal transform technique is used and the effectiveness of the present method is demonstrated from the two numerical examples. In addition, the effects of the rotor parameter change on it's dynamics are also disscued.
