Ultrasonic Evaluation of Interfacial Properties in Layered Substrate

Abstract

INTRODUCTIONLayered substrate is a very important type of material. The layer, such as the paint on metal, has been used widely for the purpose of corrosion prevention. The use of a layer as part of surface acoustic wave devices also has been found to have important applications in such high-tech environments as the semiconductor industry. The performance of layered substrate is critically dependent on the bonding conditions between layer and substrate.Most of the research on the bond quality of layered substrates was confined to two extremes: perfect bond and complete misbond. For example, many studies of the interface problems assumed intimate mechanical contact between the two surfaces that constitute the interface. However, this assumption only applies to the perfect bond. The results of these studies provide a range of possible variations, but give no details about the in-between cases. In reality, bond quality could exist in a wide spectrum. How to evaluate the imperfect substrates is, thus, a challenging area of study. BACKGROUND

Ultrasonic Characterization of Nickel-Chromium-Base Anticorrosive Coatings

“…A B-scan of the surface waves, shown in figure 3, shows a shift in phase precisely in those areas. This effect is somehow expected since the density of the coating is smaller than the density of the metal base, which causes the surface velocity to drop with the thickness of the coating [5].…”

The Application of Angular Profile of Ultrasonic Backscattering on the Layered Substrate

“…Generalized Lamb waves propagate with velocities determined not only by the elastic properties and densities of material but also by layer thickness and frequency of the waves [5]. Furthermore, the presence of imperfections in layered materials can also affect the velocity dispersion of Lamb waves [6]. At a given frequency and layer thickness, several modes may exist with different velocities or at a given velocity several modes can be excited provided that the ultrasonic wave contains several frequencies (or a broadband pulse).…”

Ultrasonic guided waves in composite plates: a study of interface bond condition and material properties determination with broadband focused air-coupled ultrasounds

“…Applying these boundary conditions to the displacements and stresses we can solve for the reflection coefficient. Upon solving that equation, we obtain the following expression [36], [54], [75], [22] -tsf …”