3次元逆散乱イメージング法の実験的検証と複数素子の遅延付き励振によるS/N比向上の試み

抄録

Ultrasonic array transducers are widely used in nondestructive testing of structural components. Recently, not only a linear array transducer but also a matrix array transducer is introduced to evaluate the position and shape of flaws. In this study, an inverse analysis method is developed by means of a matrix array transducer in order to reconstruct three dimensional (3D) shape of flaws. The method is based on the linearized inverse scattering method in the frequency domain and can perform shape reconstruction of flaws by fast inversion algorithms with the 3D FFT. The 3D inverse scattering imaging method (ISIM) is validated by an immersion ultrasonic measurement which imitates the matrix array ultrasonic testing. Since the size of an element of the matrix array transducer is small in general, the enhancement of the signal to noise ratio is required for the application of the 3D ISIM to actual fields. Here, ultrasonic beams generated by delayed excitations with multi-elements are applied to amplify the incident spherical wave, and its performance is checked by numerical simulations and experimental measurements.