Reliability of PEA Measurement in Presence of an Air Void Defect

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.

Quantifying the thickness of each color material in multilayer transparent specimen based on transmission image

Combing the color transmission image and the Beer–Lambert law shows a great application prospect in quantifying each material in multilayer specimen. Here, a novel, low-cost, and efficient optical algorithm is proposed to predict the thickness of each color material in a multilayer specimen from the color transmission image based on the Beer–Lambert Law. In this work, a normal scanner is employed to achieve the color transmission image of the monochrome transparent films. RGB values represent the transmitted intensity. A linear relationship between the optical depth and physical thickness is observed under different monochromatic lights. It is supposed that for a multilayer transparent film which consisted of different monochrome transparent films, the optical depth is related to the physical thickness of each monochrome transparent component. Therefore, an estimating equation is proposed to predict the thickness of each color material in the multilayer specimen. According to the result, the standard deviation of predicted thickness and practical thickness of each color film in the multilayer specimen is 0.93%. Fairly good agreement and high accuracy are obtained between the practical and predicted values, and the validity of this method is confirmed.