Simulation of Ultrasonic and Electromagnetic Wave Propagation for Nondestructive Testing of Concrete Using Image-Based FIT

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Presently, ultrasonic and electromagnetic waves are often used for the quantitative nondestructive testing of concrete. The evaluation of material deterioration and detection of defects in concrete are carried out using ultrasonic waves. On the other hand, the positions of reinforced bars can be reconstructed by using electromagnetic waves. In order to gain a better understanding of ultrasonic and electromagnetic waves in concrete, it is useful to model the wave propagation and scattering process explicitly in the time domain. This study presents a technique for numerical time domain modelings of ultrasonic and electromagnetic waves. Our simulation tool is based on a combination of the finite integration technique (FIT) and an image-based modeling approach. The FIT is a grid-based spatial discretization method that works in conjunction with a leap-frog-type explicit scheme. In the image-based modeling approach, geometries of concrete are determined using a digital image, e.g., a cross-sectional image or CT data. Then the processed pixel or voxel data are directly fed into the FIT. We demonstrate simulations of the contact ultrasonic method and electromagnetic radar method for concrete. The utility of the image-based FIT is validated with experimentally measured data.