A new elastic-wave-based imaging method for scanning the defects inside the structure

In this paper, a new nondestructive testing method using elastic waves for imaging possible voids or defects in concrete structures is proposed. This method integrates the point-source/point receiver scheme with the synthetic aperture focusing technique (SAFT) process to achieve the effect like scanning with a phase array system. This method also is equipped with large functioning depth because of the high-energy feature that elastic waves usually possess over traditional ultrasound. Both numerical simulations and experimental tests were carried out to explore the capabilities of this method in revealing single or multiple defects implied in a matrix material. The results from numerical simulations indicate that this method can clearly reveal the number of the voids or defects, their locations, and front-end profiles. The influence of the accuracy of the wave velocity determination on the resultant image also was evaluated in this study. Furthermore, the effects of the types of the responses to be recorded and the wavelength of the introduced waves also were evaluated so that very good resultant images may be obtained. Both the results from the numerical simulations and the experimental tests indicate that this elastic-wave-based method exhibits high potential in inspecting the defects of in-situ concrete structures by imaging.