Looking to quickly and accurately locate internal defects in materials while strictly controlling inspection costs? Ultrasonic Testing (UT) is your ideal solution!
If you want a comprehensive understanding of UT inspection, this blog is a must-read.
What is UT Inspection?
UT Inspection full name is Ultrasonic testing .It is a kind of non-destructive testing technology that uses sound waves (i.e., ultrasonic waves) with frequencies higher than the human auditory range (typically > 20,000Hz) to detect the internal structure of objects, measure distances, or identify the properties of objects.
Its basic principle is: emit ultrasonic waves to the object under test, then receive its reflected, transmitted or scattered echoes, and through analyzing these echoes’ features to get the objective’s information (such as changes in propagation time, amplitude, frequency, etc.).
How Does It Work?
Ultrasonic testing principle: Imitating the “echolocation” of bats, the ultrasonic test core thought is similar to bats and dolphins use echolocation in nature.
- Emit: A probe can be named a transducer (core is a piezoelectric wafer) under the excitation of electrical pulses producing high-frequency mechanical vibration, thereby emitting ultrasonic.
- Dissemination: Ultrasonic dissemination in medium (such as air, water, metal, human body, etc.).
- Reflected: When it encounters interfaces with different acoustic impedances (such as defects, bubbles, or another object), a part of ultrasonic will be these interfaces reflected back.
- Receive: The same one or another transducer receives these reflected echoes, and returns them to an electrical signal.
- Process and display: Instrumental analysis of these electrical signals, through calculating the time of the ultrasonic from emitted to received. It can precisely calculate the distance to the obstacle. At the same time, the strong, etc., information of echoes can frame pictures or oscillograms, supply operating personnel can read.
Simple formula: Distance = (speed of sound × time)/2
The Applications of UT Inspection
UT inspection applications are very widely, below are common fields:
- Non-destructive testing for Industry
Flaw detection: to test if there are defects like cracks, bubbles, inclusions, etc., in the internal of metal, composite material, etc.
Measure thickness: it can precisely measure the thickness of container wall, pipe, hull, etc. Especially, the solution can only be touched on one side (like testing pipe corrosion).
- Medical diagnosis (ultrasound imaging)
B-mode ultrasonography: it’s the commonest application, used for prenatal check-ups, focusing on fetal development, examining abdominal organs (liver, gallbladder, kidneys), heart (echocardiogram), blood vessels, etc.
Doppler ultrasound: using the Doppler effect to measure speed and direction of blood. Used for check vascular disease like thrombosis, arteriosclerosis, etc.
- Ranging and Remote Sensing
Reversing radar: the ultrasonic sensor of car detection obstacle’s distance on back.
Robot obstacle avoidance: helps robots to feel the surrounding environment.
Liquid level measurement: measure the liquid height in the container.
Sonar: the underwater detection system, used for ship navigation, fishing, seabed mapping, search for underwater objects, etc.
- Clean
Ultrasonic cleaning machine: uses ultrasonic to produce micron bubbles in liquid, these bubbles break and produce the impact force that can clean the seam of precise parts, jewelry, glasses and other complex-shaped things.
UT Inspection for Titanium Products
UT inspection is an important non-destructive testing technology (NDT) for the titanium industry. It’s like making a B-mode ultrasonography for titanium material, which can be highly effective and precise to find defects of the material internal. It’s protecting the key link of products’ quality and safe.
The sheet below summarizes the ultrasonic test mainly application scenarios and features in the titanium industry.
It is convenient for you to understand quickly
| Application scenarios | Mainly test object | Common method |
| Titanium Ingot | Shrinkage cavities, cracks, gas holes, porosity | Longitudinal wave pulse reflection method (water immersion method or contact method) |
| Titanium Plate/Bar | Internal defects such as cracks, pores and porosity | Longitudinal wave pulse reflection method (water immersion method or contact method) |
| Titanium Pipe | Longitudinal and transverse defects on the inner and outer surfaces | Multi-channel automated ultrasonic testing |
| Titanium Weld Seam | Welding defects such as porosity, incomplete penetration and incomplete fusion | Ultrasonic phased array technology (PA), time difference of diffraction (TOFD) |
| Special Titanium Product | Internal defects in as-cast titanium alloys | Conventional ultrasonic testing |
Common Ultrasonic Testing Methods
- Pulse-echo method
Principle: this is the commonest and basest method. The same probe emits ultrasonic and receives echoes from defects or workpiece.
Advantage: just needs to be close to one side of the workpiece, easy to operate.
Application: most of conventional ultrasonic testing, such as thickness test, flaw detection, etc.
- Penetration transmission method
Principle: use two probes put two sides of workpiece respectively. One probe for emit, and another for receive. Through measure ultrasonic energy attenuation to judge whether the materials’ internal has defects or not.
Advantage: to some kinds of defects (such as loose and mixed) more sensitive.
Limited: it needs close to workpiece two sides, can’t precisely position defect’s depth.
Application: commonly used for more attenuation material such as plastic, composite materials, rubber, etc.
- Diffraction time difference method (TOFD)
Principle: use two probes, one probe for emit, and another for receive. Put them on two sides of weld seam symmetry.
Advantage:
Through-wall extent precision is very high.
Fast test speed, small blind spot.
The results can be recorded and reproduced
Application: mainly used for the weld seam test, especially the precise quantification of critical defects.
- Phased array technology (PA)
Principle: this is the most advanced ultrasonic technology. It uses a probe composed of multiple tiny chips (up to 128 or more). Through computer precise control every chip emits the pulse’s time difference (electronic delay), it can achieve the deflection, focusing and scanning of the sound beam.
Advantage:
Electronic scan: it doesn’t need move probe can achieve big range test and fast speed.
Dynamic focus: It can keep best resolution in different depth.
Versatility: One phased array probe can replace multiple traditional probes.
Intuitive imaging: It can generate real-time, high-resolution two-dimensional and three-dimensional images (S-scan, C-scan), and the results are easier to interpret and archive.
Applications: the test of complex parts such as aerospace parts, weld seam test, and corrosion mapping. It has become to high-end mainstream application.
Advantages of UT Inspection
Good directionality: Due to its high frequency and short wavelength, ultrasonic waves are not easy to diffuse and can propagate in the direction of beams, thus making precise directional emission easy.
Strong penetration: When propagating in most media (especially solids and liquids), the energy attenuation is small, so it can detect the interior of very deep objects.
Non-destructive testing: It usually couldn’t damage the structure and performance of the object being inspected.
Safe to human body: It is radiation-free and far below the power level that could cause damage to tissues
Disadvantages of Ultrasonic Testing
The coupling agent is needed: Ultrasonic waves attenuate very rapidly in the air. Therefore, in industrial inspection and medical applications, it is necessary to apply coupling agents (such as engine oil or gel) between the probe and the object under test to expel air and ensure the effective propagation of ultrasonic waves.
It’s hard to test some material: It is rather difficult to detect some irregular, non-uniform or highly sound-absorbing materials, such as wood, concrete and certain composite materials.
Blind spots exist: For objects that are very close or very far away, the detection accuracy will decline.
The generated images or data usually need to be interpreted by professionally trained personnel.
Conclusion
All in all, ultrasonic tests don’t need broken inspected object, widely used for fields such as industrial flaw detection, medical imaging (such as B-ultrasound), and distance measurement. This technology is safe and highly effective, and is the best non-destructive assessment method.
FAQ
Q: What is ultrasonic weld testing equipment?
A: It has ultrasonic welding machine, ultrasonic weld flaw detector, ultrasonic spot welder, portable ultrasonic thickness gauge etc.
Q: What is ultrasonic titanium pipe wall thickness testing?
A: The pipe thickness is calculated based on the time and sound velocity of the acoustic waves reflected from the inner and outer pipe, as measured by the emitted ultrasonic waves.
Q: What is available ultrasonic testing of materials?
A: Ultrasonic testing is used to test metallic materials such as carbon steel, stainless steel, and titanium, as well as non-metallic materials including composite materials, ceramic materials, and plastic products.
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