Detection of subsurface cracks in mesostructure models of concrete using Rayleigh wave propagation

Abstract Subsurface cracks may remain undetected until significant harm occurs, which often lead to their neglect in conventional nondestructive evaluations. In addition, the scattering of the elastic waves may affect the detection results. This study investigates the impact of the presence of aggregates on the identification and quantification of subsurface cracks using Rayleigh wave propagation. To achieve this purpose, concrete mesostructure models that integrate absorbing boundaries using the stiffness reduction method and subsurface cracks are constructed. The expected arrival times of the waves are derived and compared with the B-scans to examine the propagation path of the mode-converted body waves. Furthermore, we introduce a novel signal extraction technique using the energy spectrum based on wavelet coefficients and a knowledge-based rule to assess the depth of subsurface cracks. Finally, attempts are made to demonstrate and validate the far-field signal enhancement phenomenon of subsurface cracks using mode conversion theories and the proposed area ratio index. The results show that the theoretical curves and B-scan maps are well aligned, suggesting that the analysis of the waveform propagation path is accurate. The proposed method is quite robust for both homogeneous and heterogeneous material configurations. The crack parameters can be obtained using the fitted curve obtained by determining the peak frequency of the transmitted signal.