NON DESTRUCTIVE ULTRASONIC TESTING OF BONDING QUALITY IN TRI-LAYER STRUCTURES USING REFLECTION COEFFICIENT SPECTRA

This paper deal with non destructive ultrasonic testing technique of bonding quality of sheets. We present a method based on the spectral analysis of the reflection coefficient of tri-layer structure composed of two aluminium sheets bonded by an adhesive layer. The boundary conditions between the three layers are those introduced by Pilarski [1]. A computer code of high accuracy is developed to calculate, in normal incidence, the reflection coefficient of this structure. The obtained numerical results are in perfect agreement with the experimental ones founded by Faiz and al [2]. A new interpretation of the evolution of the reflection coefficient minimums from the perfect bonding case to the bad bonding case is proposed. It shows clearly the possibility of testing of the bonding quality from this coefficient.