Abstract: For circumferential rod fastening rotor bearing system, the additional stiffness matrix and additional generalized moment provided by circumferential rods are obtained after simplifying the rod as massless, preloaded linear spring; the normal and tangential interface contact stiffness under different loads are obtained after finite element analysis on the cuboid contact model with rough surface; including the effects of interface contact stiffness and preloaded circumferential rods, the nonlinear dynamic model of circumferential rod fastening rotor bearing system is built using Timoshenko beam element subjected to axial force. After the system degrees of freedom are reduced based on local nonlinearity property, the nonlinear dynamic characteristics of circumferential rod fastening rotor supported by journal bearing are studied using Poincaré-Newton-Floquet method combined with prediction-correction technique, and the local stability and bifurcation behaviors of periodic motion with different speeds and mass eccentricities are obtained. The results show that the system has parameter regions corresponding to periodic motion, quasi-periodic motion and period-doubling motion. With the increase of speed, period-doubling bifurcation occurs with small eccentricity and quasi-periodic bifurcation occurs with large eccentricity. The threshold speed of system bifurcation decreases after considering interface contact stiffness, and period-doubling bifurcation occurs at lower mass eccentricity with unbalanced preload forces.

Key words: Bifurcation, Contact stiffness, Nonlinear, Rod fastening rotor, Stability