Abstract
Acoustic emission (AE) method is a powerful tool to monitor in-situ damage in materials because elastic waves are generated due to brittle cracking or frictions. Conventional AE techniques use a piezoelectric ceramic element and attach it to samples in order to detect AE signals at the surface of samples. Microfractures in materials are quantitatively analyzed by the detected waveforms such as location, size and fracture mode. However, conventional AE transducer cannot be used at elevated temperature or severe environment. Laser based ultrasonic (LBU) technique has been developed to characterize materials properties and detect flaws in materials. We have developed a non-contact AE technique to detect AE signals in various environments where conventional AE technique cannot be applied. AE during sintering of alumina ceramics and thermal spying of alumina powder on steel substrates were successfully measured by laser interferometers. The effect of processing parameters on AE behavior was clearly observed by analyzing AE waveforms.
