Eddy current tomography for visualization of cracks in aircraft riveted joints

The control of the subsurface areas of metal products is necessary in many technological processes. So, for example, in aerospace technology it is essential to determine the presence of defects in aircraft engines. The same problems arise in chemical, power and other industries, which are letting out the highly technological equipment one of the widely known methods for inspecting metal products in the aviation industry is the eddy current method. This method is widely used to control small microscopic defects inside conductive materials. This method allows to ensure the safety of the operation of various products and devices in many areas of modern industry. An eddy current detector (probe) is a device, which induces eddy currents into metal objects and then detects the magnetic fields produced by these eddy currents. A magnetic field is created by a coil, or set of coils, through which a time-varying electrical current is driven. The frequency regime is sufficiently low, a few hertz to a few hundred kilohertz, so the targets of interest are within the near field of the transmitter. Considering the high conductivity of study samples, we can define that used waves in metals are located in the millimeter wave band. An eddy current imaging can be considered near-field imaging and a device allowing obtaining the eddy current images as a scanning near-field microscope. The obtained experimental results showed that the proposed tomographic method is effective for studying various complex inhomogeneities under the metal surface

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An Eddy-Current Method of Flaw Detection in Nonmagnetic Metals

Journal of Applied Mechanics ◽

10.1115/1.4009085 ◽

1941 ◽

Vol 8 (1) ◽

pp. A22-A26

Author(s):

Ross Gunn

Keyword(s):

Eddy Current ◽

Eddy Currents ◽

Flaw Detection ◽

Current Method ◽

Test Sample ◽

Current Pattern ◽

Eddy Current Method ◽

Recorded Performance ◽

Alternating Magnetic Fields ◽

Nonmagnetic Metals

Abstract An equipment suitable for the location of surface or submerged flaws in nonmagnetic metals is described. A predetermined pattern of electrical eddy currents is induced in a perfect test sample by alternating magnetic fields. Sensitive pickup coils properly disposed in relation to the eddy currents measure only the departures of the eddy-current pattern from the pattern in the perfect sample. The departures are indicated on a meter or may be recorded. Performance data are given for a universal type of search unit especially adapted for general surveys.

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Investigation of welds by the method of the magneto-optical eddy current flaw detection

EPJ Web of Conferences ◽

10.1051/epjconf/201818502014 ◽

2018 ◽

Vol 185 ◽

pp. 02014 ◽

Cited By ~ 1

Author(s):

Nazar Lugovskoy ◽

Vladimir Berzhansky ◽

Dmitry Filippov ◽

Anatoliy Prokopov ◽

Alexandr Shuyskyy

Keyword(s):

Mathematical Modeling ◽

Magnetic Fields ◽

Eddy Current ◽

Eddy Currents ◽

Flaw Detection ◽

Current Method ◽

Epitaxial Films ◽

Eddy Current Method ◽

Ferrite Garnet ◽

Conducting Materials

The paper deals with the magneto-optical eddy current method of flaw detection of conducting materials, in which epitaxial films of ferrite garnet are used as sensors. In particular, the possibilities of visualization of welded seams in magnetic and non-magnetic samples, as well as the defectoscopy of the seams themselves, are considered. The second part of the work is devoted to mathematical modeling of the distribution of the magnetic fields of eddy currents near similar defects.

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Hardness assessment of induction hardened layers based on the analysis of eddy current signal

Inżynieria Powierzchni ◽

10.5604/01.3001.0013.9724 ◽

2020 ◽

Vol 24 (4) ◽

pp. 3-9

Author(s):

Dominik Kukla ◽

Mirosław Wyszkowski

Keyword(s):

Comparative Analysis ◽

Cross Sections ◽

Eddy Current ◽

Eddy Currents ◽

Induction Hardening ◽

Current Method ◽

Current Signal ◽

Eddy Current Method ◽

Lift Off ◽

Non Destructive

The work concerns the assessment of the possibility of identifying changes in hardness of carburized and induction hardened layers using the eddy current method. The tests were carried out on three sets of samples, made of AMS 6414 steel, with different layer thickness, subjected to induction hardening and tempering in a wide temperature range, to obtain differences in layer hardness for each set. The samples of each set, with the layers with a hardness in the range of 760–920 HV, were subject to testes using eddy currents which consisted in the assessment of phase angle changes obtained as a result of the lift – off effect. Standard hardness measurements on the surfaces of the hardened layers were also carried out, and microhardness profiles were made on the cross-sections of the samples. The results of hardness measurements were subject to comparative analysis with the results of non-destructive tests and on this basis it was possible to identify changes in the hardness of layers, based on the results of non-destructive tests.

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Eddy Current Method for Testing of Metals under Simultaneous Exposure to Radiation and Hydrogenation

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1084.16 ◽

2015 ◽

Vol 1084 ◽

pp. 16-20

Author(s):

Vitalii V. Larionov ◽

Andrey M. Lider ◽

Yurii S. Bordulev

Keyword(s):

Phase Composition ◽

Eddy Current ◽

Eddy Currents ◽

Current Method ◽

Metal Structure ◽

Eddy Current Method ◽

Simultaneous Exposure ◽

Metal Hydrogenation ◽

Diffusion Properties

The study demonstrated that implementation of eddy currents of different frequencies enables identification of altered phase composition, diffusion properties and metal hydrogenation extent. Using the newly developed parameters of eddy current method sensitivity, we have established that the change of a metal structure from one layer to another is identified by the currents of different frequency according to the depth of their penetration into a metal.

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Determination of the Penetration Depth of Eddy Currents in Defectoscopic Tests

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.588.64 ◽

2013 ◽

Vol 588 ◽

pp. 64-73 ◽

Cited By ~ 2

Author(s):

Leszek Dziczkowski ◽

Sławomir Zolkiewski

Keyword(s):

Magnetic Field ◽

Penetration Depth ◽

Eddy Current ◽

Eddy Currents ◽

Current Method ◽

Impedance Change ◽

Depth Of Penetration ◽

Eddy Current Method ◽

Measuring Device

In the defectoscopic tests by means of the eddy currents method only a certain superficial layer of the tested element is inspected. The reason of this phenomenon is connected with a very important feature of the eddy currents. The induced eddy currents generate its own magnetic field which obstructs penetration for the primary magnetic field. It is crucial to know the penetration depth of eddy currents. It allows planning successfully the diagnosis process. There are two cases worth mentioning: when the eddy current method is treated as the additional method complementary to the ultrasound method (because it does not detect superficial defects) and when the eddy current method is used as the main method for the thin elements diagnosis. The most frequently used evaluation method of eddy currents penetration depth is connected with determination of the e-folding decrease of electric current. The definition is convenient to use because it is simplified by using in the mathematical formula (allowing determination of the depth) frequency of eddy current and conductivity of the diagnosed elements. However the simplifications are not sufficient in practice. When we change the frequency of eddy currents during the survey or the probe then the depth of penetration is also changed, then we can measure the depth of the defects. While measuring the conductivity of a proper material element it is obligatory to prepare an adequate size of the sample that is free of defects. Knowing the value of penetration depth is then very helpful. On the other hand, when we have a sample of a specified size and we want to measure its conductivity then the knowledge of the depth of penetration of eddy currents helps us to select the proper frequency. In the paper there is described a proposal of a different definition of the penetration depth of eddy current, much more useful and accurate according to the authors. To obtain much more precise results, the new eddy current method was proposed. This method takes into account not only the parameters of the diagnosed sample and the eddy current frequency but the characteristic of the measuring device as well. The above mentioned method is based on the universal mathematical model of impact of conductive thin foil on the measuring coil impedance change. The procedure of calculations is easy to carry out online.

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