Localization of Acoustic Emission Signals in a Fatigue Specimen Using Laser Ultrasonics

摘要

The geometry of a test specimen changes a measured acoustic emission waveform because of reflection, transmission and mode conversion at the interfaces and boundaries of the specimen, thus making it difficult to determine the location of a surface crack. This research develops a technique to identifiy the source location using measured acoustic emission signals. The signals are generated and detected with a repeatable, broad band acoustic emission source, a pulsed laser, and a broad band, high-fidelity sensor, a laser interferometer. The recorded signals are analyzed by wavelet transform in order to determine the arrival times of waves for several frequency levels. These arrival times are used to quantify the location of a propagating surface crack as well as the velocity of the most dominant feature, the Rayleigh wave, and the time lag between the signal generated by the crack and the recording of the signal. The accuracy of the method is demonstrated by comparing the identified source location with the exact one.