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Correction published on 20 September 2016, see Materials 2016, 9(9), 784.
Open AccessFeature PaperArticle

Calibration Methods of Acoustic Emission Sensors

Department of Materials Science and Engineering, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
Academic Editor: Alkiviadis Paipetis
Materials 2016, 9(7), 508;
Received: 30 May 2016 / Revised: 16 June 2016 / Accepted: 20 June 2016 / Published: 24 June 2016
(This article belongs to the Special Issue Acoustic Waves in Advanced Materials)
This study examined outstanding issues of sensitivity calibration methods for ultrasonic and acoustic emission transducers and provides workable solutions based on physically measureable quantities, laser-based displacement measurement in particular. This leads to mutually consistent determination of transmitting and receiving sensitivities of sensors and transducers. Methods of circumventing problems of extraneous vibrations on free transmitters are used, giving the foundation for face-to-face calibration methods. Working on many ultrasonic and acoustic emission transducers, their receiving and transmitting sensitivities are found to be always different, while their ratios exhibit unexpected similarity. This behavior is attributed to monopolar pulse generation and bipolar received signals due to electrical charge transfer during elastic wave motion and reflection on the back face. This is verified through a quantitative piezoelectric sensing experiment. Displacement vs. velocity calibration terminology is clarified, redefining the “V/µbar” reference for contact sensor calibration. With demonstrated differences in the transmitting and receiving sensitivities of transducers, the requirement of the Hill-Adams equation invalidates the basic premise of the currently formulated reciprocity calibration methods for acoustic emission transducers. In addition, the measured reciprocity parameter for the case of through-transmission significantly deviates from the approximate theoretical prediction. It is demonstrated that three methods provide reliable sensor calibration results that are complimentary among them. View Full-Text
Keywords: acoustic emission; sensors; transducers; calibration; face-to-face; laser interferometry; Hill-Adams equation; tri-transducer method acoustic emission; sensors; transducers; calibration; face-to-face; laser interferometry; Hill-Adams equation; tri-transducer method
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Ono, K. Calibration Methods of Acoustic Emission Sensors. Materials 2016, 9, 508.

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