A self-calibrating piezoelectric transducer with integral sensor for in situ energy calibration of acoustic emission

Abstract

Piezoelectric transducers are used as both transmitters and sensors in acoustic emission (AE) testing applications. However, the transducer outputs are significantly affected by the coupling between the transducer and the structure. This means that the coupling must be very carefully controlled or assessed if reliable AE calibration sources are to be generated, and be considered in the AE system calibration if reliable AE measurements are to be made. The paper shows that by integrating a piezoelectric AE sensor to the backing of a conical piezoelectric transducer acting as the transmitter, a self-calibrating AE energy point source can be obtained. There is a negative linear relationship between the AE signal energy from the backing sensor and the coupling efficiency for a constant electrical input to the transmitter over the frequency range of interest in AE measurements (100 kHz to around 1 MHz). This should enable the strength of the simulated AE point source to be determined using the AE measurement from the backing sensor, and hence to facilitate in situ energy calibration of AEs in structures.