Acoustic and Eddy Current Methods of Nondestructive Testing of Thermally Expanded Graphite Sheets

Abstract

Abstract The paper presents noncontact methods for testing the density of thermally expanded graphite (TEG) sheets: acoustic shadow method, based on the evaluation of the transmission coefficient of the acoustic wave in high frequency range, and eddy current method, based on the evaluation of the complex resistance of parametric surface-mounted eddy-current transducer. Rresults of investigation of the sensitivity curves for the sheets and mats of TEG in a wide range of their density variations. According to the results of the experiment, there is a decrease in the amplitude parameter U in the implementation of the acoustic shadow method with an increase in the density of TEG sheets. Increasing the density of TEG sheets also leads to a linear decrease in the complex resistance of eddy current transducer.