Forced Response Assessment of Cracked Aerospace Structures Using VIBRANT

This study presents an assessment of forced vibration responses of cracked beam-type aerospace structures using VIbration BehaviouR ANalysis Tool (VIBRANT), a high-fidelity time-marching analysis platform. The methodology captures contact-induced nonlinearities arising when crack surfaces intermittently open and close during vibration, producing time-varying stiffness and damping. Frequency-domain behaviour is extracted from time-domain simulations of beams representing aero-engine blades and wing structures under various crack configurations. Results reveal that a crack-induced nonlinearity is strongly configuration-dependent: only specific combinations of crack depth, position relative to the moment distribution, and excitation amplitude produce detectable nonlinear signatures, whilst other configurations—including cracks representing significant structural compromise—exhibit quasi-linear response that would evade conventional vibration-based detection. The deeper crack configuration activates breathing behaviour at higher forcing levels, leading to rightward resonance frequency shifts and amplitude reductions due to impact and frictional contact damping, whereas the baseline and repositioned crack configurations maintain a quasi-linear response across all forcing levels examined. This configuration-dependent character of the breathing crack nonlinearity—and in particular the conditions under which nonlinear signatures are absent despite active damage—represents a critical finding for structural health monitoring and maintenance planning in aerospace applications.