Schematic of an ultrasonic inspection, showing the transducer over a plate, with the resulting signals displayed on a detector screen.
Ultrasonic inspection (UT) uses high frequency sound waves in a component and monitors how they travel in the material. A transducer converts electrical energy into mechanical energy to send signals into the test piece, working in reverse for returned signals. A contact transducer may be used with a coupling gel on the surface of the part, or immersion transducers if the sample is in a water bath. During an ultrasonic test, sound waves travel through the material and are reflected back from surfaces or flaws. Reflected sound energy is displayed versus time, and the inspector can visualize a cross div of the specimen revealing the depth of various features.
Advantages of Ultrasonic Inspection
- Used for detection of a wide array of defects
- Portable equipment for immediate results
- Inspect complex shapes, large sizes and many materials
- Only single sided access may be required
- Inspection can be automated
- Minimum part preparation
- Superior penetrating power
Limitations of Ultrasonic Inspection
- Contact with couplant or immersion in water is typically required
- Extensive skill and training required
- Surface finish and roughness can interfere with inspection
- Thin parts may be difficult to inspect
- Reference standards are typically needed