Nonlinear dynamic behaviors of circumferential rod fastening rotor under unbalanced pre-tightening force

A nonlinear dynamic model of the rod fastening rotor bearing system is established considering nonlinear oil-film force, unbalanced mass, unbalanced rod pre-tightening force, etc. The motion equation of the system has been deduced from Lagrange’s equations. The nonlinear dynamic and bifurcation characteristic is investigated using fourth-order Runge–Kutta method. Bifurcation diagram, vibration waveform, frequency spectrum, phase trajectory and Poincare map are applied to analyze the nonlinear dynamic phenomena of the rod fastening rotor. The numerical results indicated that the initial deflection caused by the unbalanced pre-tightening force, nonlinear oil-film force and rotational speed has a great influence on the nonlinear dynamic characteristics of the rod fastening rotor bearing system. The corresponding results can provide the guidance for the fault diagnose of a rod fastening rotor with unbalanced pre-tightening force; meanwhile, the study may contribute to the further understanding of the nonlinear dynamic characteristics of a rod fastening rotor with unbalanced pre-tightening force.