2009 Volume 6 Issue 10 Pages 613-617
Air-coupled ultrasonic waves in the megahertz range are applied for noncontact detection in a pipe wall reduction model. Various widths and depths of pipe wall reductions were used, and the pipes were irradiated with 1.2MHz air-coupled ultrasonic waves. F-mode guide waves were used to detect the defects in the pipe walls. The experimental results confirmed that ultrasonic waves reflecting from areas of wall reduction in the pipes could be detected. A wall reduction of about 10mm could be deduced from the reflected waveforms. A clear correlation between the depth of the wall reduction and the amplitude of the reflected waves was found.