Non-destructive testing (NDT)
What are non-destructive testing (NDT)?
The term non-destructive testing (NDT) is derived from the English language. The purpose of conducting non-destructive testing is to detect surface and subsurface defects during quality control or the operational process.
Non-destructive testing has found its application in industries such as aerospace, automotive, defense, petrochemical, machinery, railway, and construction. The most popular non-destructive testing methods include: ET, RT, UT, MT, PT, VT, XRD, and BNA. Thanks to NDT testing, material defects such as pores, blowholes, lack of fusion, thinning, delamination, cracks, and corrosion can be detected.
During the NDT test, no damage whatsoever occurs to the tested sample
The advantage of non-destructive testing is the absence of changes in the functional properties of the tested components
Ultrasonic testing (UT)
This testing method enables the detection of material discontinuities inside a product. The test involves introducing ultrasonic waves into the object, which then reflect off any discontinuities, lack of fusion in welded, bonded, or soldered joints, as well as potential cracks. This type of testing is most commonly applied to metals and their alloys, as well as plastics.
Visual testing (VT)
In the case of visual testing, optical instruments are used, enabling the detection of irregularities and weak points on the exterior of products. VT testing is mandatory for castings, welded joints, and steel structures. The visual method enables the detection of surface, through-thickness, and welding discontinuities.
Radiographic testing (RT)
This type of testing involves introducing gamma radiation or X-rays into a given object. After recording the radiometric image of the object, the test results are obtained in the form of a radiogram. This is one of the most effective forms of NDT testing, enabling the detection of discontinuities resulting from the operation of objects and structures. RT radiographic testing is applied to both metals and their alloys, as well as non-metals.
Penetrant testing (PT)
This method, also known as the dye technique, involves applying colored penetrants and fluorescent liquids to the object. In the case of detecting surface or welding discontinuities or material leaks, the liquid will turn a specific color. Penetrant testing is applicable to all metals and their alloys, as well as non-metals.
Ultrasonic thickness measurement (UTT)
UTT non-destructive testing enables the measurement of the structural thickness of an object or item using longitudinal ultrasonic waves. During the test, the travel time of the ultrasonic wave through the given object is measured, which allows for the exclusion or confirmation of potential discontinuities and irregularities. Ultrasonic thickness measurements enable the examination of the thickness of pipes, sheets, plates, tanks, pipeline walls, and many others.
Magnetic particle testing (MT)
The MT magnetic particle method enables the detection of surface and subsurface discontinuities. This method is most commonly used for materials such as cobalt, nickel, or ferromagnetic steels. Magnetic particle testing involves magnetizing objects or structures with a pulsed, alternating, or constant magnetic field, and then detecting magnetic flux leakage using magnetic powders. When the magnetic field exhibits such a flux, it indicates the detection of irregularities in the material.
Eddy current testing (ET)
In the case of electrically conductive materials. The test utilizes the phenomenon of electromagnetic induction, and the penetration depth of eddy currents depends primarily on the magnetic permeability and electrical conductivity of the material, the excitation frequency of the eddy currents, as well as the shape and dimensions of the object. ET non-destructive testing enables the detection of wall thickness losses resulting from corrosion, cracks, deformations, or inclusions of other materials in the examined surface.
Other non-destructive testing methods
In addition to those mentioned above, non-destructive testing also includes thermographic testing, chemical testing, leak testing, measurements of pipeline ovalization and creep, ultrasonic testing using TOFD and Phased Array methods, and many others.
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