Nonlinear harmonic wave-guided interfacial debonding identification in RC beams

Interfacial debonding identification within reinforced concrete (RC) structures is an ongoing and critical issue in structural health monitoring. In this paper, a novel nonlinear harmonics-based method for identifying, localizing, and quantifying interfacial debonding in RC beams is presented. The mode conversion phenomenon and contact acoustic nonlinearity of guided waves at interfacial debonding region are thoroughly examined using a combined theoretical, numerical, and experimental investigation, which sheds light on the propagation behavior of the first and second harmonics in RC beams with single interfacial debonding. Inspired by the phase-reversal approach, the temporal separation of the second harmonic is achieved by integrating the excitation results from both the original and phase-reversed signals. The theoretical investigation is conducted to correlate the arrival time of harmonics with structural damage, and its accuracy is validated by the numerical group velocity inversion and wavenumber-frequency analysis. The experimental evaluation, involving six RC beam specimens with varying debonding length, further demonstrates the validity of the method for precise interfacial debonding identification. The experimental and numerical evidence confirms the effectiveness of the proposed method, highlighting its potential for practical application.