Ultrasonic Evaluation of Bonding of an Elastomer to a High Impedance Material Introduction

The objective of this work was to provide a means of assessing the integrity of the bond between an elastomer and a metal when access is restricted to the metal side. Since the acoustic impedance of the metal was high, the acoustic reflectivity of the bond interface was nearly unity and varied but slightly between a good bond and a complete disbond. Consequently any acoustic inspection technique must accurately measure small changes in the acoustic signal. In addition extraneous variables such as transducer coupling and incidence angle must be either distinguished or eliminated. When an echo train from multiple backwall reflections was observed, the logarithmic decrement decreased but slightly when a disbond was encountered. Use of this signature for routine inspections would be very tedious and a more definitive indication is required.