A glimpse at fifty-one years in acoustic emission


After 51 years continuously involved in acoustic emission (AE) testing and research, it has been interesting to look back over five decades. The equipment available in the early 1970s was primitive compared to now. At the start of that decade, only one, recently established, commercial company sold AE measurement equipment, and other useful equipment was internally built or adapted from other technologies. Further, the data that came from an AE monitored test was simply the number (counts) of penetrations of a fixed one-volt threshold expressed as an increasing total or a rate and recorded on an x-y plotter. The purpose of this “glimpse” is to present advances both within the author’s research as well as those that were adopted from others research that were viewed as moving AE technology forward. This “glimpse” is not intended to be comprehensive, instead it is limited to aspects the author was involved in. Among the topics to be covered are advances such as understanding hydraulic test machine continuous noise, true rootmean-square (RMS) voltage measurements, inclusion particle fracture or decohesion, tension versus compression testing for unflawed metal samples, the pencil lead break, an acoustic emission signal simulator, broadband sensors, digital waveform recorders, large transversedimensioned plates, absolutely calibrated flat-with-frequency AE sensors, finite element modeling (FEM) in isotropic materials, validation of FEM, computer-based digital AE systems, intensity of frequency versus time of AE signals, superposition of group velocity results and FEM beyond the case of dipoles in an isotropic plate.
