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A new technique called Hybrid Method is proposed in the analysis of the geared rotor-bearing system. This technique combines the Finite Element Method and the Generalized Polynomial Expansion Method to formulate the system equations of motion. The compliance and shear deformation of the shaft element, flexibility and damping of the bearings, stiffness and damping and pressure angle of the gear mesh are considered. The coupling between the torsional and lateral vibrations of the gears and the effect of the location of the gear mesh are also considered in the model. The whirl speed analyses and the steady state responses due to mass unbalance and displacement transmission error excitation are then calculated. Finally, the accuracy and the efficiency of the proposed method are demonstrated. The torsional-lateral coupled modes of the system are greatly affected by the gear mesh. It is shown that the stiffness, damping, and pressure angle of the gear mesh have significant influence on these modes. The steady state responses due to the transmission error, at tooth passing frequency during gears meshing, are of high values. The proposed Hybrid Method with application to geared rotor-bearing system, multi-stepped single shaft rotor system, and dual rotor system leads to better efficiency than the Finite Element Method without losing the accuracy.
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