Modal identification of nonlinear systems using successive approximation model

Early studies have shown that normal modes of nonlinear systems are dependent on response level. Amplitude-dependent model should be used to represent this nonlinear modal property. An amplitude-dependent model of nonlinear modal equation is proposed and a corresponding identification procedure is presented in this paper. Modal equations, modal frequencies and mode shapes of nonlinear systems can be determined using the proposed method from measured response data. The method is verified through a 3DOF nonlinear system and is shown to be effective.