Improvements to dry coupled ultrasound for wall thickness and weld inspection Available to Purchase

There are many ultrasonic applications where liquid couplants are undesirable. Automated scanning systems need complex couplant delivery and recovery systems in order to prevent either contamination or degradation to the test object. Soft materials such as rubbers can be used as a shoe to dry-couple the ultrasound from a piezoelectric transducer into the part but this can have relatively poor performance, particularly at high frequency where attenuation in the shoe material is large. The present paper describes results from a dual approach to tackle the problems associated with dry coupling. Various rubbers are examined for their ultrasonic properties and additional amplification is used to compensate for high frequency losses. As a result we have established that standard rubbers can be used as dry couplant materials for zero-degree longitudinal wave applications and it has even been possible to produce dry-coupled angled shear waves transducers suitable for flaw detection.