What is Ultrasonic Tetsing?
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 characterise the material or for flaw detecting. 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 very small flaws
- 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 depth of internal flaws and the thickness of parts with parallel surfaces
- Able to estimate 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 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 for 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 required for tests that use conventional UT
- UT may have reduced sensitivity for volumetric flaws, particularly metal inclusions, than radiographic testing