Abstract
Although it is possible to achieve higher resolution by conventional ultrasonic technique, it suffers from a disadvantage because testing has to be performed in a liquid medium. In contrast with the conventional technique, a dry-contact ultrasonic technique, which can be carried out without wetting the testing parts, is preferable. In a new technique that is developed by the authors, a dry-contact interface is used by inserting a membrane between water and the tested parts. Experiments were also carried out in search of membrane that can transmit higher frequency components. Dry-contact ultrasonic transmission using two kinds of plastic films and a silicone rubber sheet was performed on an acrylic resin. It was shown that the plastic films far excel in transmitting higher frequency components than the silicone rubber sheet.