Iterative Complex Phase Resonance Analysis.

Abstract

Experimental modal analysis has proved to be of increasing importance in many structural engineering fields. It is used more and more often, particularly as an important prerequisite for the refinement and updating of structural mathematical models on which the dynamic qualification of modern aerospace structures is based. Complete identification of structures with weak damping coupling, in the form of their normal frequencies, real modes, damping coefficients and generalized masses, is successfully performed by means of the conventional phase resonance approach. In this method, the optimal exciter locations as well as the exciter frequency and force amplitudes are chosen by means of the Mode Indicator Functions (MIF) in order to excite only one mode of the system at a time. In contrast, complete characterization of structures with strong damping coupling requires knowledge of a full modal damping matrix among the other parameters. Such knowledge can be obtained only theoretically from results of the classical phase resonance approach, while the high degree of accuracy and complexity necessary of the measurements made any effort up to now unsuccessful. The new approach presented here allows for phase resonance tests to be performed on structures with strong damping coupling and high damping for the first time, obtaining a complete identification as a result, also in characterizing damping properties. As compared to the classic methods, some new features of the approach make it interesting when applied to structures with weak damping coupling as well.