After the sinking of the Titanic in 1912, the first ultrasonic thickness gauge was created. Researchers wanted to determine a way for ships to find icebergs before they saw them, and to do this they began testing sound waves.
Following these tests, sonic testing was further developed during the First World War as a method of finding submarines.
It was not until 1928 that scientists began testing UT for industrial use when a Soviet researcher named Sergei Sokolov discovered that sound waves could be used to identify defects in metallic materials. Over the next few decades, the technique was widely adopted and since then it has become one of the more common NDT methods.
Electromagnetic Ultrasonic Thickness Gauge
What is ultrasonic testing?
More specifically, an ultrasonic test is performed on the material to determine the presence of defects by measuring the thickness using high-frequency sound waves (typically 500kHz-20Mhz).
In ultrasonic testing, inspectors will use a probe or other type of transducer to send sound waves through the material they want to inspect. If there is no defect in the material, the sound waves will pass through it, but if the sound waves hit the defect they will bounce off it, indicating its presence.
The inspector can use the signal from the sound waves to create a 3-dimensional visualization of the material and determine the distance between the different defects found in it.
The following are the main benefits of using ultrasonic thickness measurement in inspections.
Immediate results
requires little preparation
It can detect defects on and under the surface of the material
it can be done on one side of the material (i.e. it can be performed even if you do not have access to the other side of the material)
It can be automated
Test results can be shared fairly simply
HS 1020 Ultrasonic Bolt Stress Detector
Ultrasonic inspection methods
There are three main ultrasonic inspection methods.
1. By Transmission
Pass-by transmission uses two transducers, each placed on opposite sides of the material being tested. One of the transducers generates a pulse and the other receives it. If the pulse is interrupted, the inspector will know that there is a defect in the path between the two transducers.
2. Pulse echo
Pulse echo is more sensitive than transmission. It is used to identify defects by measuring the time it takes for the amplitude signal to propagate between different points or surfaces of the material.
3. Resonance
Resonance is similar to pulse echo, with the difference that the regularity of transmission can be altered by resonance testing. Resonance testing is mainly used when only one side of the material can be accessed.
Where is ultrasonic testing used?
The basic principle of ultrasonic testing is to use sound to detect the thickness of a material at different points.
Ultrasonic thickness measurement can help inspectors find tiny cracks, gaps, corrosion or other defects in the material that are too small to be seen by other NDT methods. It can also be used to detect corrosion - if one area is thinner than another, it may indicate that the area is corroded and may need maintenance.
In addition to metals, ultrasonic thickness testing can be used to test plastics, composites and ceramics. It can also be used to test concrete, but the results may not be as reliable.
The following are some of the assets that are commonly tested using ultrasonic thickness gauges.
flare stacks
Wind turbines
Large storage tanks
The following are industries that typically use ultrasonic testing as part of their inspection procedures.
Aerospace
Automotive
Electronics and batteries
Metals and Casting
Oil and gas
Power Generation
Railways
