The influence of the preload on the nonlinear dynamic performance of the rod-fastened Jeffcott rotor system

For a rod-fastened Jeffcott rotor (RFJR) system, this paper establishes a nonlinear dynamic model considering contact interface, preload, unbalanced mass, nonlinear oil film force, and gives the dynamic equation of the rotor system. Then the fourth-order Runge–Kutta method is applied to study the nonlinear dynamics and bifurcation characteristics of the RFJR system. The bifurcation diagram, time-domain vibration waveform, frequency spectrum, phase trajectory, and Poincare section are applied to investigate the influence of the preload on the nonlinear dynamic performance of the rotor system. The results show that the preload affects the instability speed of the synchronous periodic solution of the RFJR system, the rotor system’s first critical speed, and the rotor system’s vibration amplitude passing the first critical speed. Whether the preload of the rotor is saturated or not has a very different effect on the vibration characteristics of the RFJR system. Assuming the fastening force of the tie rods is uneven, it will make the combined rotor have a certain initial bending deformation. At this time, the detuning rate of the tie rod will affect the rotor system’s nonlinear dynamic performance. In addition, the phase angle between the initial bending deformation and the mass eccentricity of the rotor also has a certain impact on the nonlinear dynamic characteristics of the combined rotor. The results obtained in this paper will provide a reference for understanding the nonlinear dynamics of the combined rotor and further research.