Damage identification for nonlinear fatigue crack of cantilever beam under harmonic excitation

In order to accurately simulate structural fatigue crack damage, the non-linear contact model was selected and verified to be suitable for the fatigue crack simulation in cantilever beam. The influence of damage severity and location on harmonic vibration responses were revealed. Moreover, the damage identification indexes based on harmonic excitation response were constructed, and the effectiveness used to identify fatigue crack damage was validated. The results reveal that contact model is effective in simulating fatigue crack and sensitive to nonlinear fatigue crack through the comparative analysis of harmonic vibration response of intact structure and damaged one. For the vibration responses of beam with different damage severities and locations, the greater the damage severity is, and the closer the damage location is to the fixed end, the more obvious the non-linear vibration characteristics presents. Two damage indicators including distortion value of phase spectrum (h(Delta)) and proportion of super/sub-harmonic amplitudes (D-d) are applied, which can effectively characterize the change of fatigue crack with different damage location and severity. Furthermore, contact model presents stronger non-linear information compared with bilinear model, which is more suitable for fatigue damage simulation.