Development of Interferometer for Acoustic Emission Testing

The characterization of the exact response of an acoustic emission sensor is of fundamental importance for the quantitative nondestructive evaluation of engineering components. To effectively determine an acoustic emission source, the influence of the sensor on the measured waveform must be determined. A heterodyne interferometer is developed and tested for the detection of acoustic emission signals. This optical device makes localized absolute measurements of out-of-plane surface velocities with very high fidelity. An important feature of this system is that a linear frequency modulation (FM) discriminator is used to demodulate the carrier signal; as a result, the interferometer behaves as a Doppler-shift detector. A series of experiments was performed to test the response of commercially available, piezoelectric acoustic emission transducers in order to understand their potential influence on a measured acoustic emission waveform.