How NDT Works

Non destructive testing methods

If you aren’t familiar with NDT services or Nondestructive Testing, this article should give you the basic information and description of NDT tests to help you understand a little better. It will not be very detailed or explain absolutely everything but in the short time we have, it should be able to outline NDT in a way that you will be able to comprehend and use to gain more information elsewhere if that is what you need. Understanding how nondestructive testing works is important because it can give you insight to manufacturing processes and other system function. So, let’s get started.

What is Non Destructive Testing?
Simply put, NDT is the process used in order to inspect, test and evaluate different materials without ruining their functionality and ability. Once the test and inspections are complete, the parts or systems are still usable. Most other types of tests cause at least a little damage to the product because of how they are preformed. These destructive tests are usually used in order for find out how the properties of the material react to impact resistance and to see how strong they are by testing fracture toughness and fatigue strength. However, it has been found the NDT inspection is the more effective method to find out these characteristics.

The method is used in order to ensure that the integrity and the reliability of the product is protected throughout the entire process. It also controls the process and lowers productions costs which helps to maintain quality levels. The medical field actually uses much of the same types of processes to test their medical appliances, although they do not called nondestructive testing. They use it because it is a safe and effective method that ensures that the device can still be used later.

What Kinds of Non Destructive Testing Methods are There?
There are a lot of different kinds of tests that can be used, including but not limited to:

  1. Acoustic Emission Testing
  2. Electromagnetic Testing Guided Wave Testing
  3. Ground Penetrating Radar
  4. Laser Testing Methods
  5. Leak Testing
  6. Magnetic Flux Leakage
  7. Microwave Testing
  8. Liquid Penetrant Testing
  9. Magnetic Particle Testing
  10. Neutron Radiographic Testing
  11. Radiographic Testing
  12. Thermal/Infrared Testing
  13. Ultrasonic Testing
  14. Vibration Analysis
  15. Visual Testing

Of these methods, the most commonly used at Magnetic particle testing, Liquid Penetrant testing, Radiographic testing, Ultrasonic testing, Electromagnetic testing and Visual Testing. Let’s go over a few of these to see if they gives us a better look at the testing itself.

Magnetic Particle Testing
This technique uses one or more magnetic field in order to find the surface disfigurements if ferromagnetic materials. A permanent magnet or an electromagnetic is typically used. When the magnetic field finds a discontinuity going opposite to the direction of the magnetic field, the lines make a magnetic flux. The flux doesn’t travel very well through the air so usually a dry powder is used.

Liquid Penetrant Testing
A liquid is applied to the surface of the material and if there are any cracks or fissures that are open, the liquid is sink inside. Then the excess liquid is removed. Once this is done, the liquid that was trapped will flow back out and show where the discontinuity is.

Radiographic Testing
This involves allowing the object to be exposed to radiation and examining the gamma rays that are given off. This is almost like an x-ray, showing lighter areas where less radiation passed through and darker areas where there was a void or defect in the material.

Ultrasonic Testing
Ultra high frequency sounds are used to see where the material echoes the sound different. The waves that cannot be heard by the human hear or recorded on a screen so that it becomes apparent when a difference in the surface area is detected.

Electromagnetic Testing
Alternating currents are used similarly to the magnetic field testing technique. The flow pattern of the currents are used to detect abnormalities.

Visual Testing
This is probably the most commonly used method. As the names suggests, this method is literally when the operator takes a look with his or her eyes, often using magnifying glasses or mirrors to manually check the surface of the materials for damage and cracks.

As mentioned in the beginning, this article will not be able to cover in detail, every single part of the process or tests but it gives you a foot in the front door to understanding how the whole process.

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