Experimental and Numerical Investigation of the Dynamic Characteristics of a Cracked Blisk Under Variable Operating Conditions

Blisk, as a critical component of aero-engines, is prone to fatigue cracks that can severely impair its dynamic performance and operational safety. This paper develops a finite element model of a blisk with breathing cracks to investigate the effects of crack distribution (adjacent blades vs. separated blades) and blade twist angle on natural frequencies, frequency-veering and mode localization, and response localization under varying operating conditions. Resonance vibration tests are conducted on blisk and cracked blisk specimens using the frequency dwell method to obtain natural frequencies and vibration responses, thereby experimentally validating the numerical model. The results indicate that cracks reduce the global stiffness, leading to a decrease in natural frequencies and modal localization phenomena. Furthermore, in the frequency-domain responses, nonlinear components such as sub-harmonics, ultra-sub-harmonics, and super-harmonics are observed in addition to the harmonics of the excitation frequency. Moreover, the cracked blisk with a 45° blade twist angle exhibits typical nonlinear vibration behaviors and the most pronounced response localization. This study provides a basis for crack monitoring and resonance fatigue warning.