Abstract
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∆) and proportion of super/sub-harmonic amplitudes (Dd) 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.
Highlights
Structural health monitoring (SHM) system plays an important role in ensuring bridge structural safety
It can be observed that natural frequency of cantilever beam with same crack location decreases with the increase of damage severity
The influences of excitation frequency, damage severity and location on harmonic vibration response of structure are analyzed, and the damage identification indexes based on harmonic excitation response is proposed and verified
Summary
Structural health monitoring (SHM) system plays an important role in ensuring bridge structural safety. The difference between local stiffness reduction and fatigue crack damage is significant in structural damage identification. DAMAGE IDENTIFICATION FOR NONLINEAR FATIGUE CRACK OF CANTILEVER BEAM UNDER HARMONIC EXCITATION. Cui et al [11] proposed a damage identification method for beam structure with single and multi-damage cases under different degrees and locations of damage based on strain modes and operational modal analysis, where cracks were introduced by high-precision electric tools. Perera et al [14] used the reduction of bending stiffness to simulate damage and realized damage identification through numerical simulation These methods did not consider the nonlinear effect of fatigue crack, which lead to the inappropriate conclusions. Currents research results revealed that nonlinear characteristics of the forced vibration responses of structure with fatigue crack must be considered in damage identification. Response of cracked beam simulated through contact model and bilinear model were compared
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