The development of reliable heat-resistant structural materials requires nondestructive evaluation (NDE) techniques to evaluate the damage progress during material testing at elevated temperatures. Hence, our optical fiber ultrasonic sensing system with a phase-shifted fiber Bragg grating (PSFBG) sensor was improved to a remote AE measurement system at high temperature. The optical fiber was used as an ultrasonic waveguide from an object material in a high-temperature furnace to the PSFBG sensor placed far from the furnace. As a result, AE signals at about 1000°C were successfully detected keeping their precise waveform. Therefore this method will be useful to evaluate the damage progress in heat-resistant materials under high temperature. Furthermore, the remote PSFBG ultrasonic sensing system was incorporated into the receiving part of a laser ultrasonic visualizing inspector (LUVI) for a high-temperature NDE. The LUVI can visualize the propagation behavior of ultrasonic guided waves in complex shape structures. As a result, the improved LUVI with the optical fiber ultrasonic receiver succeeded in clear visualization of the ultrasonic wave propagation in a ceramic plate at 1000°C. Then an artificial damage formed in the ceramic plate was able to be detected by the observation of reflection waves from the damage. Hence, this system has a potential as an effective and intuitive NDE method in high-temperature environments.

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