High spatial resolution imaging for damage detection in concrete based on multiple wavelet decomposition

The main challenge faced by the conventional delay and sum (DAS) damage imaging method for concrete is that the spatial resolution will be degraded when using few embedded piezoceramic transducers. To resolve this issue, an improved DAS imaging method with an adjustable spatial resolution is proposed based on multiple wavelet decomposition in this paper. First, the scattering stress waves received by the sparse embedded piezoceramic transducer array are decomposed by different mother wavelets and reconstructed according to the spectrum signature of the excitation signals. Then, the reconstructed scattering signals between each transmitter and sensor pair are combined to design the imaging function to enhance the spatial resolution of the conventional DAS method. Experimental results indicate that the proposed method can effectively achieve high spatial resolution imaging for damage detection through signal post-processing, even using few embedded transducers. Moreover, the spatial resolution of the proposed method can be adjusted by changing the number of utilized mother wavelets.