Observation and Analysis of Simulated Ultrasonic Acoustic Emission Waves in Plates and Complex Structures
SourceExperiments have been performed with the Panametrics acoustic emission simulation test set which show that acoustic emission signals in plates and shells travel in the plate modes supported by these shapes. The first longitudinal plate mode has the highest group velocity in its low-frequency limit, and signals in that mode and frequency range arrive first, followed by strong signal at the velocity of the first flexural mode in its nondispersive region. In some cases the flexural signal is much stronger than the longitudinal signal. In general, the received signals are dispersed. The time-frequency-energy output matrix tends to be complicated, as energy of different frequencies is spread over time by the various dispersive modes. Special transducers can be used to discriminate against certain particle motions, suppressing the reception of certain modes, and may be useful in triangulation studies.