Improvements to dry-coupled ultrasound for wall thickness and weld inspection

This paper describes results from a dual approach to tackle the problems as sociated with dry coupling. Various rubbers are examined for their ultrason ic properties and additional amplification is used to compensate for high-f requency losses. As a result, we have established that standard rubbers can be used as dry couplant materials for zero-degree longitudinal wave applic ations. A new dry couplant material has been discovered with good high-freq uency transmission characteristics. With this material it has even been pos sible to produce dry-coupled angled shear waves transducers suitable for fl aw detection in welds. The 'dry couplant' also has a very low acoustic impe dance and can be used for matching air-coupled transducers.