Noncontact AE measurement system using acoustic microscope

The surface of a slide glass (a specimen) with a notch was set in water at the focal region of a point-focus-beam lens to detect the AE (acoustic emission) signals radiating from cracks around the notch during a three point bending test. Output signals received by a transducer with a centre frequency around 50 MHz were amplified and A/D converted at a sampling rate of 200 MHz by a digital oscilloscope. The power spectra of the output signals were compared for the two cases with and without the weight used for the application of fracturing stress on the glass specimen. AE signals with a frequency range from a few megahertz to 100 MHz were successfully detected with this system for the glass specimen mounted on a small three point bending test bench.