Electromagnetic acoustic transducer for NDE

Non-contacting electromagnetic acoustic transducer (EMAT) has been under development. The EMAT could generate and receive ultrasonic waves through the Lorentz force. It may be possible to simplify preparation works such as pipe coating removal and surface polishing, because the EMAT could conduct ultrasonic testing (UT) without the EMAT contacting to the test surface. The EMAT 's sensitivity is lower than that of the conventional piezoelectric transducer. Also the EMAT's sensitivity becomes lower as the lift-off between the EMAT and the test surface increases. To detect the ultrasonic wave echo with high signal-to-noise ratio, it is necessary to increase the transmitting energy and reduce the receiver noise. A high-energy transmitter was developed and the crack detection tests were conducted. As a results, it was confirmed that the EMAT could detect 0.5 mm deep notch out. The maximum lift-off was 0.6 mm, which was 3 times larger than that of the existing EMAT