Based on the analysis of structural and dynamic characteristics

a dynamic model of flexible rotor systems under misalignment and unbalance excitations in aero-engines was developed by Lagrange equations.It described the mechanism and effect factors of nonlinear properties of response in misaligned rotors.The numerical results show that the rotor system and its coupling may behave in a complex and nonlinear way with the excitation of misalignment and unbalance.The response of the system presents nonlinear properties

including 1 and 2 harmonics

and the amplitude and spectrum signature closely relate to the amount of misalignment and the distribution of unbalance.