Ultrasound interferometry for the evaluation of thickness and adhesion of thin layers

Abstract

A simulation work has been carried out to characterise thin layers by a technique called ultrasound interferometry, which is based on the resonance and anti-resonance of ultrasound waves verified in the presence of some interfaces having different acoustical impedances. Normal incidence ultrasonic reflection measurements have been considered. The reflection coefficients were calculated against frequency, velocity and thickness. A graphical user interface (GUI), developed in Matlab environment was used to simulate the calculation of several coating thicknesses (velocities) over different substrates, like iron and aluminium. The results are based on the representation of reflection or transmission coefficients against frequency, thickness and velocity in the coatings. The developed GUI is a very important tool to predict the behaviour of thin layers embedded between two thicker media, like mechanical properties providing the calculation of its thickness and ultrasonic velocity, in fast and easy way.