CHARACTERIZATION OF ADHESION BY RAYLEIGH MODES GENERATED AND DETECTED BY LASERS
Résumé
Adhesion is the ability of dissimilar particles to clutch together and is used to describe the contact between two interfaces. It is often considered as the predominant factor for coating reliability in thin-film technologies. Many techniques have been established to estimate the coating-substrate adhesion intensity. In this work, laserultrasonics, as a non-destructive non-contact method, is implemented to identify the adhesion level on a structure composed of a polyvinyl chloride film in contact with an aluminum sample. For the generation of elastic waves, a doubled frequency Nd:YAG laser is used. Then, the normal displacement at the surface of the substrate is detected thanks to a heterodyne interferometer of Mach-Zehnder type. Rayleigh modes dispersion curves obtained experimentally are compared to the theoretical ones, which are analytically obtained in order to evaluate the adhesion level as an inverse problem. Moreover, the finite element method is exploited to model the propagation of the surface acoustic waves on the studied sample. Indeed, it is necessary to predict the phenomena that could happen while characterizing a layer on a substrate structure. Finally, this allows to analyze the matching between experimental and numerical results while applying different degrees of adhesion.
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