Ultrasonic Thickness Testing is a method of nondestructive testing that measures the local thickness of a solid element, either metal or composite based on the time it takes for an ultrasonic wave to return to the surface.
As ultrasonic waves have been shown to travel through individual alloys at a constant speed, with only minor variations, testing is typically performed on metals and frequently used to monitor metal thickness or weld quality in industrial settings including maritime, aerospace, and automotive.
Advantages of UTT
There are many advantages to UTT:
- Non-destructive technique
- Does not require access to both sides of the sample
- Can be engineered to cope with coatings, linings, etc.
- Good accuracy (0.1 mm and less) can be achieved using standard timing techniques
- Can be easily deployed, does not require laboratory conditions
- Relatively cheap equipment
- No need to remove the coating of the metal.
- EMAT does not require the use of couplant.
- EMAT can conduct thickness measurements through corrosion and other surface coatings on metals
Disadvantages of UTT
Although UTT is a great tool, there are some things to remember:
- Usually requires calibration for each material
- Requires good contact with the material
- Cannot take measurement over rust (Does not apply to EMAT)
- Requires coupling material between the measured surface and the probe. (Does not apply to EMAT)
- Interpretation needs experience