New Developments in Complex Phase Resonance Analysis: The Direct Method.

Abstract

Complete identification of struvtures 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 so-called phase resonance algorithms. In these methods, the optimal exciter location as well as the exciter frequency and force amplitudes are chosen in order to excite only one mode of the system at a time. Until now, phase resonance methods were unable to completely identify structures with high damping coupling, because the mode indicator functions that make direct control of modal tuning possible can only be used for the identification of real modes. The Complex Phase Resonance Analysis (COMPRA) methods presented allow for phase resonance tests to be performed for the first time on structures with high damping coupling obtaining a complete identification as a result. The technique presented in this paper is based on the direct solution of the fundamental relations of the Complex Phase Resonance Analysis. The first COMPRA method developed, based on iterative solution of the equations, is described in detail. The method introduced here was first applied on a simulated lumped-parameter system and then on the CLUMOD test structure. Also presented are the results of the transformation of complex into real mode parameters of a structure, applied to both sets of modes obtained from the application of the method, confirming the theoretical validity of the transformation.