What is the primary type of wave analyzed in Ultrasonic Testing (UT)?

In Ultrasonic Testing (UT), the primary type of wave that is analyzed is sound waves. Ultrasonic testing utilizes high-frequency sound waves—typically above 20 kHz, which is higher than the upper limit of human hearing—to detect imperfections and measure material thickness. The sound waves are transmitted into a material and reflected back from interfaces such as flaws or the back wall of the tested component.

The selection of sound waves as the primary focus in UT is crucial because these waves can travel effectively through solids and liquids, allowing for the identification of discontinuities that can indicate weaknesses in materials. The reflection and transmission of these waves are interpreted to provide information about the internal structure of the material being tested.

Other types of waves, such as electromagnetic waves or seismic waves, do not have the same interaction with solid materials in the context of nondestructive testing. Electromagnetic waves are used in other NDT methods, like radiography, while seismic waves pertain to geological studies and are not relevant to material inspection through ultrasonic techniques. Water waves are also not applicable as they pertain primarily to liquids and would not be used in solid material testing scenarios. Thus, sound waves are fundamentally critical in the process of ultrasonic testing.