A fixed–free interface component mode synthesis method for rotordynamic analysis

A fixed–free interface component mode synthesis method has been developed for carrying out rotordynamic analysis with the gyroscopic effects being considered. This hybrid model has been developed to combine the advantages of the fixed interface method, known popularly as the Craig–Bampton approach and the free interface method, known as the Craig–Chang technique. It is shown in the paper that the proposed fixed-free interface method is able to predict the whirl frequencies accurately (like the Craig–Bampton method) and at the same time predict the unbalance response accurately (like the Craig–Chang approach). The proposed technique has been validated for two systems. (a) a cantilever rotor with a heavy disc at its free end and (b) a typical twin-spool aero-engine rotor-bearing configuration. This technique is also suitable for nonlinear analysis, when a squeeze film damper is present.