ULTRASONIC EVALUATION OF AN INTERFACE BETWEEN A COATING LAYER AND SUBSTRATE

Ray T. Ko and Laszlo Adler Department of Welding Engineering The Ohio State University Columbus, Ohio

ABSTRACT

The interface Condition in a layered substrate is critical on the performance of this type of material. Most studies of interface conditions in a layered substrate confined to extremes and gave no details about the in-between cases. In this study the lowest order mode of the generalized Lamb wave was used to examine the interfacial properties of imperfect layered substrates. The results showed that the position of the turning point in the dispersion curve was sensitive to bond quality Variation. By incorporating an effective interface layer into a multiple layer formulation and comparing the calculated results with the experimental data, the interfacial properties of the layered substrate were evaluated. Moreover, the shape of the dispersion curve of this lowest order mode was found to be dependent on the bond quality and anisotropy, but the dominating factor was the bond quality.

INTRODUCTION

Layered 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

The elastic wave propagation in thin layers on a half space has been studied by many researchers. Farnell and Adler (1972) studied the effects of a thin solid layer in intimate mechanical contact with an infinite substrate. They examined the so called Rayleigh-like mode, or simply Rayleigh mode.

Ultrasonic Characterization and Mechanics of Interfaces ASME 1993 (AMD-Vol. 177) (Book Contents)
ISBN No. 0-7918-1043-7
Library of Congress Catalog Number 93-73596
Copyright 1993 by
THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS All Rights Reserved Printed in U.S.A.

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