Coupling vibration mechanism of multistage blisk-rotor system with blade crack

This study aims to address the issue of vibration modeling and coupling vibration mechanism analysis of multistage blisk-rotor (MBR) systems with blade cracks. First, a comprehensive coupling vibration model of the MRB system containing the flexibility of shaft and blade, the swing motion of offset blisk structure, and the nonlinear effect of blade breathing crack is developed. Then, the coupling vibration mechanism of the MRB system is systematically investigated through analytical and numerical analysis, based on which the vibration indicators for the presence of blade cracks are extracted. At last, the effects of blade crack and operating condition parameters on the coupling vibration of the MRB system are comprehensively analyzed. The comparative results indicate that the crack depth and aerodynamic force may significantly affect the crack indicators in shaft bending and torsional vibrations, while the disc unbalance mainly affects the crack indicators in shaft bending vibrations. It is also suggested that the BHM and crack detection of rotating blades should comprehensively consider different crack indicators and perform continuous condition monitoring to obtain more robust and accurate results.