Automated non-contact NDT by ultrasonic surface waves

An automated ultrasonic scanner based on the non-contact air-coupled technique is designed and developed in order to perform nondestructive characterization of the surface of different structures and to detect the surface defects. The measurement is carried out without any contact with the examined part. The paper presents the scanner and several examples of its applications: the on-site characterization of concrete walls; the inverse analysis of concrete wall cover and the detection of surface defects on a steel sample and along old used railway rail.