6. Ultrasonic inspection

Ultrasound is emitted by means of "transducers", most of which operate using the piezoelectric effect (figure 5 ). We analyze the propagation of high-frequency mechanical waves (usually a few Megahertz) within the material making up the part to be inspected.

At the frequencies used (1 to 10 MHz), ultrasound does not propagate in air. To ensure their passage between the transducer and the part to be inspected, a coupling medium must be placed between the two. Two techniques are available to ensure this coupling: contact testing and immersion testing.