Development of flaw evaluation system for large civil structures by using low frequency ultrasonic wave and scattered waveforms

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The research about the technique of ultrasonic flaw reconstruction in elastic materials based on inverse scattering methods are carried out to develop a non-destructive evaluation system for large civil structures made by concrete materials.In this project, two and three dimensional elastodynamic inverse scattering methods are developed. The scattered wave measurement and the attenuation and phase velocity measurement were carried out for utilization of measured wave data. And, the comparison of reconstructed shapes by Born and Kirchhoff inverse scattering methods brought flaw characterization system.The shape reconstruction of flaws in the concrete materials by Born and Kirchhoff inverse scattering method is investigated. In this method, the angular and frequency diversities of the scattered waves are superposed in the form of the Fourier transform in the polar coordinate. An efficient method to accelerate the inversion process is proposed by rearranging the scattered wave data from the polar coordinate to the rectangular coordinate.The concrete specimens, that contain flaw models and has flat surface, are prepared and the scattered waveforms are acquired from the pulse-echo measurement. The performance of the shape reconstructions is shown for flaw models is the prepared specimens.As the result, the possibility of this method to reconstruct the shape of flow in concrete materials is shown.