Research on imaging and localisation of concrete crack damage based on Lamb wave and multi-channel signal alignment fusion algorithm

Concrete structures find extensive applications across a wide range of fields. Long-term stress and environmental factors induce crack damage, endangering structural safety and making detection highly significant. Existing Lamb wave methods suffer from stringent positioning requirements, heavy full-matrix data loads, and dispersion sidelobe interference. This paper proposes a multi-channel signal alignment and fusion method based on a Lamb wave square array to identify concrete structural crack damage. This method designs a single excitation square array, reducing the amount of data processingand providing multi-channel signals from different orientations. Multi-channel signals are aligned in the time domain by calculating flight times for discrete pixels. Moreover, a time of flight calculation method suitable for the square array presented is proposed. To address the issue of indistinct focusing of signals, this paper selects the excitation signal and conducts time-frequency analysis. Transformed wavelet coefficients are used for signal alignment and fusion. This approach can not only better match the square array but also effectively reflect the energy change information of the signal, thereby avoiding the problem of artefacts. Ultimately, crack damage is localized by the maximum pixel value. Simulation and experimental results confirm the feasibility of this approach for concrete crack damage identification.