HIGH-FREQUENCY ULTRASONIC TESTING

The interest of high frequency ultrasonic testing lies in the weak wavelength of the acoustic wave, which gives a good spatial resolution, and in the high bandwidth allowing very short pulse emission. In this paper, the authors show that the high frequency technique may be used successfully in many fields like layer thickness measurement, interface characterization and detection of small defects (inclusions, delaminations, micro-cracks,...). However, the strong attenuation of high frequency waves, which varies with the square of the frequency, limits the exploration depth (a few millimeters in metals at 100 MHz). But the acoustic wavelength remains compatible with most of the industrial roughness.