Nonlinear Vibrations of Bolted Rotor System Incorporating Misalignment Fault

The bolted rotor system functions as a critical component in aero-engines and gas turbines. Additionally, the misalignment fault is a typical and common fault in bolted rotor systems. Nevertheless, current research on bolted rotor systems has not covered misalignment faults. Therefore, a mathematical model of bolted rotor systems incorporating misalignment faults is established in this work. The nonlinear dynamics of bolted rotor systems involving misalignment are investigated by the comparison of the frequency amplitude responses, waterfall diagrams, rotor orbits and time-varying stiffness. Moreover, an in-depth analysis is conducted on the variations in vibration behaviors of rotor systems under different misalignment degrees. Finally, the proposed model is examined using rotor-rig tests conducted under aligned and misaligned conditions. A consistent observation from the numerical and test results is that the 2× frequency resonance speed does not equate precisely to 0.5 times the critical speed. In addition, the 2× component undergoes a sudden change as the misalignment level rises.