What is the primary purpose of a couplant in ultrasonic testing?

The primary purpose of a couplant in ultrasonic testing is to facilitate effective sound transmission between the transducer and the test material. In ultrasonic testing, sound waves generated by the transducer need to travel into the material being tested in order to detect any internal flaws or assess thickness. Air is a poor conductor of sound, and without a couplant, there would be significant loss of ultrasonic energy at the interface between the transducer and the test material.

The couplant, which could be a gel, liquid, or paste, fills the air gap between the transducer and the material. This allows for better contact and more efficient transfer of sound waves. The use of a coupling medium maximizes the transmission of ultrasonic energy into the material, ensuring that accurate and reliable results are obtained during testing. Consequently, the effectiveness of the ultrasonic testing process relies heavily on the proper choice and application of the couplant.