IDENTIFICATION OF NONLINEARITY FROM ANALYSIS OF COMPLEX MODES

In many engineering applications, structural nonlinearity needs to be identified while measured modes are complex. In this paper, a new method for the identification of nonlinearity from analysis of complex modes is presented. The existence of complexity of vibration modes is discussed and the theoretical basis of the method is introduced. The extension of the method to frequency response function data measured from nonlinear multi-degree-of freedom systems is attempted and ways of minimizing/eliminating the residual effect (influence of other modes) on the analysis accuracy are discussed. The practical applicability of the method is assessed based on its application to the data measured from analog computer circuits as well as practical nonlinear structures.