To date, most acoustic emission (AE) testing has been undertaken without a proper means of calibration for AE sensors in situ. The detected AE signals are significantly affected by the positioning of the sensor on a structure, machine or process, and by the variability of the sensor-structure interface. The result is AE measurements with poor repeatability and no traceability. All that is being actually measured is the voltage (or the voltage in dB with reference to 1 μV) of the AE sensor system output, whereas what is often desired is the measurement of the actual AE source or sources; these may be some distance away from the position of the AE sensor. This paper outlines a possible hierarchy of traceability for AE energy measurements through in situ calibration of the AE sensors using artificial AE energy sources: an elastic ball impact, a thermoelastic pulsed laser irradiation, and a self-calibrating conical piezoelectric transducer.
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