ON THE DYNAMIC ANALYSIS OF ROTORS USING MODAL REDUCTION

A finite element dynamic model for a rotor-bearing system is developed . The model accounts for the gyroscopic moments and anisotropic bearin gs. For dynamic response analysis, a reduced order model using modal t runcation is obtained. Two modal truncation schemes are invoked; one w ith planar (undamped) modes, and the other with complex (damped) modes . Both the modal characteristics and the dynamic responses of two roto r systems are evaluated using the two reduction schemes. Simulation re sults are presented to demonstrate the validity and accuracy of the re duced order form. The question of whether to use planar or complex mod es in establishing the modal transformation is addressed.