To make up the deficiency of the finite element method in predicting dynamic characteristics of the dual-rotor system with local nonlinear

high-dimensional nonlinear dynamic model of dual-rotor system was established with finite element software and fixed interface modal synthesis method; subsequently an implicit time-domain method was presented to solve the problem using the Newmark algorithm ideas

and the computational efficiency of this method was largely dependent on the number of degrees of freedom at nonlinear forces' location. Considering the nonlinear forces of squeeze film damper and inter-shaft bearing

the nonlinear dynamic response characteristics of the counter-rotating dual rotor system under dual imbalance force were studied. The study shows that there are some combinations of these two rotation frequencies in system response

in addition to rotation frequencies of the internal and external rotors. Besides

bifurcation and chaos emerge in system speed bifurcation diagram and the critical speeds decrease slightly with the increasing inter-shaft bearing radial clearance. The axis orbit of the system will be of a petal shape

which is basically consistent with the experimental results.