What is Ultrasonic Testing?
Ultrasonic testing (UT) comprises a range of non-destructive testing (NDT) techniques that send ultrasonic waves through an object or material. These high-frequency sound waves are transmitted into materials to characterize the material or for flaw detection. Most UT inspection applications use short pulse waves with frequencies ranging from 0.1-15 MHz, although frequencies up to 50 MHz can be used.
Advantages
The advantages of ultrasonic testing include:
- High penetration power, allowing for flaw detection deep within a part
- High sensitivity, allowing for the detection of tiny flaws
- It can be used to test when only one side of an object is accessible
- Greater accuracy, when compared to other non-destructive testing methods, for determining the depth of internal flaws and the thickness of parts with parallel surfaces
- Able to estimate the size, shape, orientation, and nature of defects
- Able to estimate alloy structures of components with differing acoustic properties
- Non-hazardous to nearby personnel, equipment, or materials
- Highly automated and portable operations are possible
- Immediate results can be obtained, allowing for immediate decisions to be made
Limitations
There are, however, a few limitations to ultrasonic testing, as follows:
- Requires experienced technicians for inspection and data interpretation
- False positive results, also known as spurious signals, may result from tolerable anomalies as well as the component geometry itself
- Objects that are rough, irregularly shaped, very small or thin, or not homogeneous are difficult to inspect
- Loose scale or paint will need to be removed before testing can commence, although clean, properly bonded paint can be left in place
- Couplants are required for tests that use conventional UT
- UT may have reduced sensitivity for volumetric flaws, particularly metal inclusions, than radiographic testing.