Ultrasonic nondestructive testing, also known as ultrasonic NDT or simply UT, is a method of characterizing the thickness or internal structure of a test piece through the use of high frequency sound waves. The frequencies, or pitch, used for ultrasonic testing are many times higher than the limit of human hearing, most commonly in the range from 500 KHz to 20 MHz. One of the oldest and most basic ultrasonic testing techniques is pulse echo (also known as “reflective” or “manual” testing). In this technique, a transducer connected to a diagnostic machine sends sound waves into the material being tested. The sound waves pass through the material and bounce back to the transducer. When a defect (such as a crack in the metal) is present, the amount of sound waves returning to the transducer is reduced – thus revealing the presence of a defect in the material. In industrial applications, ultrasonic testing is widely used on metals, plastics, composites, and ceramics.
How it work
Sound waves traveling through a material will reflect in predictable ways off of flaws such as cracks and voids. An ultrasonic flaw detector is an instrument that generates and processes ultrasonic signals to create a waveform display that can be used by a trained operator to identify hidden flaws in a test piece. The operator identifies the characteristic reflection pattern from a good part, and then looks for changes in that reflection pattern that may indicate flaws. A wide variety of cracks, voids, disbonds, inclusions, and similar problems that affect structural integrity can all be located and measured with ultrasonic flaw detectors. The minimum detectable flaw size in a given application will depend on the type of material being tested and the type of flaw under consideration
- Internal Rotating Inspection System (IRIS)
- Time of Flight Diffraction (TOFD)
- Phased Array Ultrasonic Testing (PAUT)