Speed characteristics of disk-shaft system with rotating part looseness

This study focuses on the looseness fault of rotating parts in rotor systems. A dedicated experimental setup is designed to induce looseness faults. Two particular phenomena of looseness faults are observed in the experiments under different torsional loads: when the torsional load is low, a constant difference in the rotational speed between the disk and shaft can be observed; when the torsional load is high, the rotational speed of the disk will dissociate with the rotational speed of the shaft and finally fluctuate within a range. The dynamic equations of the disk-shaft system are established, and a novel contact model of rotating part looseness is proposed. In the contact model, looseness contact stress may exist in the contact area and is described as a form with bilinear stiffness. Simulations using the equations are performed to explain the experiment results. The two phenomena, namely speed difference and speed dissociation, are satisfactorily explained by the simulation results. The results of this study may be helpful for the diagnosis of looseness faults in practical engineering. (C) 2019 Elsevier Ltd. All rights reserved.