Ultrasonic NDT (UT)
Ultrasonic testing remains the most popular non-destructive testing method after visual testing.
In this method, a high-frequency sound wave generated by a transmitter travels through the object under test. The frequency of this wave is usually between 1 and 10 MHz.
The wave distorts when encountering a change in the density of the material. This change in the transmitted wave is captured by a receiver.
The equipment then measures and analyses the received wave to understand the nature and depth of the defect. The equipment can also calculate the thickness of the specimen by dividing the wave speed in the material by the time taken for travel.
There are many types of ultrasonic testing available each with its own nuances and field of application. These are pulse-echo testing, immersion testing, guided wave testing and phased array ultrasonic testing to name a few.
We can identify defects such as cracks, abrasions, thinning, pitting and corrosion using ultrasonic inspection.
Advantages of ultrasonic testing:
- Safe and easy to use
- Highly accurate and sensitive
- Ability to gauge dense materials
- Detection of surface and subsurface defects
- Identifications of minor defects not visible to the naked eye
Disadvantages of ultrasonic testing:
- Requires training
- Needs a smooth surface
- Difficult to use with thin materials
- Part geometry may create complications
- Wave propagation speed in tested material must be known for accurate results
- Couplants are required for smooth wave transfer from the transmitter to the specimen