Nondestructive evaluation of surface coating adhesion using model studies and ultrasonic goniometer experiments

A general-purpose model for studying the reflection of acoustic plane waves or line-focused beams from a stratified medium is presented. Loss of adhesion between one or more pairs of layers is taken into account by assuming a partial layer tangential-displacement slip between the layers. Measurements of the reflection of focused ultrasonic beams from an aluminum plate covered by a thin self-adhesive aluminum foil, whose adhesion to the aluminum plate locally is decreased, are presented. The measured reflection coefficients are compared to calculated beam-reflection coefficients, and the numerical model is used for interpreting the measured results