Collinear nonlinear guided wave mixing for debonding detection in reinforced concrete beam using longitudinal and torsional wave modes

Abstract

Nonlinear guided wave (GW) mixing of longitudinal wave is proposed to detect and locate debonding damage between rebar and concrete in the reinforced concrete beam. Two wave mode pairs are chosen based on phase matching and synchronism conditions for observing sum combinational harmonics, and longitudinal GW as the excitation signal while the longitudinal and torsional wave as the receiving signal. The study is carried out numerically and experimentally for bonded and debonded reinforced concrete specimens. For bonded specimens, second-order combinational harmonics are absent in all bonded cases. The contact effect due to debonding can generate second and higher-order combination harmonics. The indication of debonding damage is determined in debonded specimens by the presence of sum combinational harmonics. The use of the phase reversal approach in this study clearly observes the increase in the amplitude of the sum combinational harmonics in the debonded cases. By utilizing the phase reversal approach and wavenumber frequency analysis, the dominant longitudinal GW modes can be used to accurately determine the location of debonding. The amplitude of the nonlinear parameter of longitudinal and torsional GW modes increases with debonding length. In this study, the results show that the torsional GW modes have better performance than longitudinal GW modes for debonding detection because the torsional GW modes have larger amplitudes than the longitudinal GW modes.