抄録
Nondestructive inspection of a high temperature structure is required to guarantee the safety of it. However, there are not any useful sensors for high-temperature structure. Some of them can't work at high temperature over 50℃. Another one is too expensive to use it. Therefore, the sensing system which can transmit and receives an ultrasonic wave which travel long distance by using a long waveguide has been studied. It means that an ultrasonic sensor could be drive at atmospheric temperature. We could confirm that a guided ultrasonic wave generated by a trial electromagnetic acoustic transducer (EMATs) can travel more than 10m for using a thin bar with a 2mm - diameter as a wave guide. However, we had a difficulty to receive a reflected ultrasonic wave from the bottom surface of a test specimen. We tried to improve the trial inspection system by using an ultrasonic horn. Finally an experiment that the temperature of a test block was heated up to about 300℃ has been done and reflected ultrasonic wave from the bottom surface of it has been detected successfully by using the long waveguide and the wave horn.
