底面反射波の時間-周波数解析に基づく超音波探傷

抄録

A novel ultrasonic inspection method is described. The propagation characteristic of an ultrasonic echo changes when the echo passes along the flaw surface. This behavior is investigated by using ultrasonic longitudinal wave and applying the time-frequency analysis to bottom echo of a slit specimen. From the experimental results, it is found that both arrival time and phase of the echo vary with its frequency. This method is applied to estimate the slit depths of 2∼10 mm, by using an immerison technique with focusing probe. The results demonstrate good linear relations between slit depth and both phase and arrival time difference. Hence the methodology gives the new way of inspection. Unlike the conventional pulse echo method, this method utilizes the bottom echo with high intensity instead of the flaw echo. Therefore, this method can be effective as an ultrasonic testing for high attenuation materials and near surface flaws.