Reliability of PEA Measurement in Presence of an Air Void Defect

Abstract

This paper deals with the reliability of the Pulsed Electro-Acoustic (PEA) technique in the case of a specimen containing an air layer. The first approach to this study has been proposed by the authors in previously published works. In these papers, the mathematical description, the PEA cell simulation model, and some experimental tests have been reported. In this work, a more accurate description of the acoustic wave behavior within the PEA cell and specimen with and without an air layer is given. Moreover, the comparison between simulation and experimental tests for both cases (specimen with and without air layer) allowed the validation of the previously developed PEA cell simulation model. The latter was previously validated only for a single layer specimen, here the good performances of the model have also been confirmed in the case of a multilayer specimen, also with an air layer. Experimental and simulation results show that the air layer acts as a barrier for the acoustic signal, due to the different acoustic impedance between the air and the solid dielectric material which constitute the specimen. Therefore, the aim of the present work is to demonstrate that in the case of a three-layers specimen, composed as dielectric-air-dielectric, the PEA cell is not able to provide the complete profile of the entire specimen under test.