Non-destructive testing (NDT) examines components or workpieces for their quality and structure that does not damage or impair them.
Fremont, CA: Non-destructive testing (NDT) examines components or workpieces for their quality and structure that does not damage or impair them. It is governed by the international standard DIN EN ISO 9712 and is employed in industrial sectors such as plant engineering, mechanical engineering, steel, power plant, or vehicle construction.
NDT is subject to a strict certification method to prevent personal injury and harm to property. In this respect, one also talks about finding and evaluating supposed discontinuities or imperfections since the actual assessment of whether a fault is present is subject to the testing regulations.
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What types of non-destructive testing exist?
The five most important types of NDT are the following; they differ in the tools used and the evaluation, e.g., imaging techniques.
- VT – Visual Testing
- MT – Magnetic Particle Testing
- PT – Penetrant Testing
- UT – Ultrasonic Testing
Other types are, for instance, eddy current testing (ET), leak testing (LT), acoustic emission testing (AT), or thermographic testing (TT).
VT - Visual Testing
Visual Testing (VT) is an optical way to check objects for discrepancies. You can check with the naked eye and with tools like magnifying glasses or mirrors.
Many flaws, like external cracks, can already be found with visual testing, making this type of inspection a simple but powerful procedure. In addition, it can be used to check some imperfections of welds, fractured surfaces, corrosion phenomena, or grinding.
MT - Magnetic Particle Testing
Magnetic particle testing (MT) is a means for testing magnetizable materials within a minimum of time. First, magnetic particles test the object with a liquid or powder. Inconsistencies are then shown by a change in the magnetic field, which causes the particles to be aligned diversely from the ‘good’ part of the object.
Like this, cracks or inclusions of non-magnetic materials can be quickly detected. Specifically remarkable is the detection of small cracks with a width of 0.001 mm and a depth of 0.01 mm. For resemblance: human hair has a thickness of 0.04 mm or more.
PT - Penetrant Testing
Penetrant testing (PT) is a pliant procedure that uses the capillary forces of cracks or pores. For this purpose, color or fluorescent penetrant (contrasted) is applied to a cleaned component, e.g., with a spray can be followed by a ‘developer.’ The penetrant then ‘creeps’ into the smallest cracks and reveals the imperfections.
environmental aspects, storage, disposal, and correct transport are important for handling the substances. The colors red and white (contrasted-developer) are usually used for dye penetrant testing. Careful should be with rough or brittle surfaces, as this can cause false readings or color intensity, as these do not need to indicate the depth of a crack.
UT - Ultrasonic Testing
Ultrasonic testing (UT) enables a view into the inside of a component. Here, a probe is moved over the surface of a component, and the ultrasonic waves ejected by it or their reflections are trailed on a screen. A phased-array imaging test can also be carried out, enabling easier interpretation.
Both flat and voluminous imperfections can be checked. Speaking of surface imperfections, it is always superior to radiographic testing (RT). It is employed, for illustration, of wall thickness measurement with vertical probes and simple geometries with angle probes.
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