Non destructive testing is the term used to describe the group of techniques used to analyze the properties of a material or component or even a system without any damage. No permanent alteration happens during the process of non destructive testing so the technique is becoming both highly popular and valuable. A lot of money can be saved during the evaluation and the research because of how it is done. The whole idea of NDT testing is very attractive to engineers and research analysts because of the technology it includes in its methods. Being able to fully understand and examine an object without having to change the integrity of the article in any way is a big step for technology.
How non destructive testing works
Some methods use electromagnetic radiation and sound to examine the article samples. External surfaces are examined in detail through microscopy. Internal layers are examined with radiation such as x-ray inspection. If further testing is needed, sound waves can be used for ultrasonic testing. This can all be done without the object hardly being handled at all.
Another common non destructive testing method is the use of liquid dyes that are injected into tiny cracks for penetrate testing. At times, these liquid dyes are florescent or sometimes not, depending on the material and the size of the crack being utilized.
Dry dust can also be applied to an area if it is in a magnetized state. The function here is that the dust particles will be attracted to any leakages that may be on the object and can reveal any defects that the article may contain.
The thermoelectric method is when thermal properties of an alloy are used to identify other alloys. Another way this is done is called a chemical test, which is when specific sensitive chemicals are used to identify if there are any alloying elements on or in the object itself. This method is usually only used on metal material because of the way it will oxidize in order to find out if there is any progressive damage involved.
High speed cameras also often used, recording without stopping until damage is detected. This is done using a sound detector which gives off a signal that triggers the camera. Once the damage is detected, the camera will stop recording and then images can be played back to see exactly what happened during all stages. The cameras always record on high speed but during the play back, the images can be slowed down or even stopped to reveal still shots if necessary, in order to find out the order of events leading up to the failure.
There are many more NDT methods but this should cover a few just to give you an idea of the process. Let’s go over one more NDT testing method to give you a better idea of the pros and cons of certain methods over others.
Ultrasonic testing is one of the NDT testing methods in which wave pulses are used through a transducer into whatever is being tested. Although the frequency of these waves is inaudible by the human ear, the waves will show up as particle vibration running in a straight line until their path is met by an obstacle which would show any discontinuity along the surface. Although this is a fairly advanced method, the results shown from ultrasonic testing have been fairly promising. Below are the pros and cons of this specific method of non destructive testing.
Advantages of ultrasonic testing
- Extremely small imperfections in an object can be detected.
- Results are very accurate when measuring an object.
- The process can be done on a single side.
- Results are instantaneous and immediate.
- Testing is completely non-hazardous.
Disadvantages of ultrasonic testing
- In order for the transducer to function properly the testing service has to be accessible.
- Irregular shaped objects make testing and inspection very difficult because of causing too many geometric echoes.
- Objects must be water resistant because in order for the ultrasonic waves to move effectively a thin layer of a water based medium must be used.
- If the discontinuity in the object is going the same direction as the ultrasonic sound it may not be detected.
Overall, it’s safe to say that the process of NDT testing is a very efficient and effective way of being able to examine sensitive articles.