Dynamic characteristics of an aero-engine rotor system with crack faults

Here, nonlinear dynamic characteristics of an aero-engine high-pressure rotor system with a breathing crack on a hollow shaft were investigated. Using the finite element method, the equations of motion for the rotor system were established considering the weight and unbalanced excitation. The cracked rotor system's stiffness matrix was derived considering its time-varying features. Using the harmonic balance method, the equations were solved approximately. 3D amplitude-frequency charts were obtained under different crack depths. It was shown that lateral vibration response peaks occur at critical speeds and subcritical ones; a deep crack located at the middle of the shaft has the most significant influence on the system's vibration responses; 3D amplitude-frequency charts calculated during the rotor rotating speed rising have obvious super-harmonic resonant components of 2X, 3X and 4X. Finally, the correctness of numerical computation was verified with the results obtained using Newmark-β method. The proposed modeling method for the rotor system with a breathing crack on its hollow shaft provided a theoretical guidance for the nonlinear dynamic analysis of aero-engine rotor systems with crack faults.