Fundamental experiment for inspection of cooling pipes in operation by using ultrasonic technique

Shear horizontal (SH) wave propagation characteristics were evaluated as a method for identifying defects in stainless steel, with the potential application of developing technology for inspecting defects during operation of nuclear reactors. Defects were positioned between a transmitter and receiver, and the propagation angle of the ultrasonic wave was varied by changing the transmission frequency. Next, the waveform from a defect was compared to reference waveform data for the case of no defects. The results showed that the differential signal had maximum amplitude at 500 and 700 kHz in the case of defects in the front surface, and at 560 kHz for defects at the bottom surface. We found that the transmission frequency yielding maximum signal amplitude was equal to the propagation direction of the ultrasonic wave, that is, the frequency determined from the direction angle, acoustic velocity and width of the permanent magnet. Further, from a study of the transmission and received frequencies, we found that in the case where the received frequencies were different from the transmission frequencies, the received frequency varied with the depth of defects.