Coupled vibration characteristics analysis and experimental study of a blade-disk-shaft system with breathing cracks

The blade-disk-shaft system (BDSS) is an essential aero-engine assembly. The emergence of fatigue cracks on blades significantly alters its dynamic characteristics, inducing complex nonlinear coupled vibrations that are notably difficult to detect. In this study, numerical models of a BDSS with blade root open crack and blade loss corner faults were developed and validated through impact hammer tests. A finite element model (FEM) of a BDSS with breathing cracks was developed to study the influence of crack parameters on its vibration characteristics, including the crack distribution pattern (adjacent or spaced blades), location (root or tip), and propagation direction (axial or radial). Furthermore, key vibration-sensitive features were extracted to identify early damage. Results suggest that cracks produce a detuning effect in the BDSS, leading to frequency splitting and modal localization phenomena. Breathing cracks reduce the peak amplitude of the blade’s time-domain (TD) response and introduce superharmonic nonlinear components in the frequency-domain (FD) response. The orientation of fatigue crack propagation is shown to significantly influence the vibration characteristics, where frequency splitting and frequency change rate can serve as a potential indicator of crack presence. This work provides a theoretical basis for crack identification and the prognosis of fatigue crack propagation trends.