Dynamic modeling and stability analysis of a rotor-bearing system with bolted-disk joint

In large rotating machines, the rotor system involves multistage disks, where bolted joints are the basic form to connect the adjacent disks. Those bolted joints, subjected to unbalanced forces and moments during normal operation, influencing the rotor dynamics and giving rise to different motion states, which are of interest for investigations focusing on vibration signatures and dynamic stability. However, little research has been done on the rotor vibration characteristics considering dynamic parameters of bolted-disk joints. Thus, the bolted-disk joint element with two nodes is proposed by characterizing the mechanical relationship between the adjacent disks in this paper. Then, in terms of the proposed joint element and lumped mass modeling method, the dynamic model for the rotor system with a bolted-disk joint is established. After that, the responses of the system are solved numerically using the Newmark-β method, and bifurcation diagram, three-dimensional spectral plots, Poincare maps as well as spectral plots are used to analyze the dynamic behaviors under different tangential stiffness and transition point of bending stiffness of the bolted joint. Additionally, the influences of the bending stiffness of bolted-disk joint on system response are also examined. Finally, utilizing the rotor dynamic responses experiment performed at a bolted-joint rotor-bearing test rig with an electric tightening wrench, some of the results from the simulation study are verified. The present work provides a theoretical basis for detecting the performance of the bolted joint of the rotor-bearing system, and prevent failure caused by changes in the stiffness of the bolted joint.