Transforming Complex Eigenmodes into Real Ones Based on an Appropriation Technique

Abstract

A new method allowing the determination of normal modes corresponding to the complex ones identified on a structure is proposed. It is based on an appropriation technique applied to forced responses computed from the identified eigensolutions. The set of applied forces is optimized with respect to an appropriation quality criterion. The knowledge of both complex and normal modes allows the full generalized damping matrix to be determined. The complex modes can then be recalculated using the normal modes and the full generalized damping matrix which provides a test of validity by comparison with the original complex modes. Simulated and experimental tests demonstrate the efficiency of this new method.