What is the function of a couplant in ultrasonic testing?

The function of a couplant in ultrasonic testing is primarily to facilitate the passage of ultrasonic waves. In this testing method, sound waves are generated and transmitted into the material being tested to detect flaws or assess material properties. However, for these ultrasonic waves to effectively travel from the transducer into the test material, there must be a medium that helps bridge any air gap between them.

Air is a poor conductor of ultrasonic waves, leading to significant signal loss if there isn’t a suitable couplant in place. The couplant, often a gel or liquid, reduces the impedance mismatch between the transducer and the material, allowing for more efficient energy transfer and propagation of the ultrasonic waves. This is essential for achieving accurate and reliable test results.

The other answers relate to aspects of testing but do not address the core function of the couplant, which is directly linked to wave transmission.