Laser Interferometric Characterization of Acoustic Emission Transducers

by Douglas A. Bruttomesso, Georgia Inst of Technology, Atlanta, United States,
Laurence J. Jacobs, Georgia Inst of Technology, Atlanta, United States,

Abstract: The characterization of the exact response of commercially available, piezoelectric and thin film, acoustic emission transducers is of fundamental importance for the nondestructive evaluation of in-service engineering components. An experimental procedure is developed that uses a laser interferometer to make localized, absolute measurements, with very high fidelity without acoustically loading the specimen. The heterodyne interferometer is operated by splitting a single frequency laser light into two components using an acousto-optic modulator. An important feature of the system is that a linear FM discriminator is used to demodulate the carrier; as a result, the interferometer behaves as a doppler shift detector. An ultrasonic transducer is used to create a repeatable source function on an elastic half-space. The interferometer's response is verified with analytical results, and used to characterize the response of commercially available transducers.

Subject Headings: Acoustic techniques | Measuring instruments | Emissions | Lasers | Material properties | Piezoelectricity | Load factors | Linear functions

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