A model-based approach for inspection of aeronautical multi-layered structures by eddy currents

2019 ◽  
Vol 38 (1) ◽  
pp. 382-394 ◽  
Author(s):  
Long Thanh Cung ◽  
Nam Hoang Nguyen ◽  
Pierre Yves Joubert ◽  
Eric Vourch ◽  
Pascal Larzabal
Keyword(s):  
Least Squares ◽  
Layer Thickness ◽  
Eddy Current ◽  
Eddy Currents ◽  
Metal Layer ◽  
Estimation Error ◽  
Eddy Current Method ◽  
Content Type ◽  
Model Based ◽  
Inversion Technique

Purpose The purpose of this paper is to propose an approach, which is easy to implement, for estimating the thickness of the air layer that may separate metallic parts in some aeronautical assemblies, by using the eddy current method. Design/methodology/approach Based on an experimental study of the coupling of a magnetic cup core coil sensor with a metallic layered structure (consisting of first metal layer/air layer/second metal layer), which is confirmed by finite element modelling simulations, an inversion technique relying on a polynomial forward model of the coupling is proposed to estimate the air layer thickness. The least squares and the nonnegative least squares algorithms are applied and analysed to obtain the estimation results. Findings The choice of an appropriate inversion technique to optimize the estimation results is dependent on the signal-to-noise ratio of measured data. The obtained estimation error is smaller than a few percent, for both simulated and experimental data. The proposed approach can be used to estimate both the air layer thickness and the second metal layer thickness simultaneously/separately. Originality/value This model-based approach is easy to implement and available to all types of eddy current sensors.

An Eddy-Current Method of Flaw Detection in Nonmagnetic Metals

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.

A MSFEM to simulate the eddy current problem in laminated iron cores in 3D

2019 ◽  
Vol 38 (5) ◽  
pp. 1667-1682 ◽  
Author(s):  
Karl Hollaus
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Eddy Current ◽  
Eddy Currents ◽  
Three Dimensional ◽  
Harmonic Balance Method ◽  
Three Dimensions ◽  
Magnetic Vector Potential ◽  
Content Type ◽  
Element Method

Purpose The simulation of eddy currents in laminated iron cores by the finite element method (FEM) is of great interest in the design of electrical devices. Modeling each laminate by finite elements leads to extremely large nonlinear systems of equations impossible to solve with present computer resources reasonably. The purpose of this study is to show that the multiscale finite element method (MSFEM) overcomes this difficulty. Design/methodology/approach A new MSFEM approach for eddy currents of laminated nonlinear iron cores in three dimensions based on the magnetic vector potential is presented. How to construct the MSFEM approach in principal is shown. The MSFEM with the Biot–Savart field in the frequency domain, a higher-order approach, the time stepping method and with the harmonic balance method are introduced and studied. Findings Various simulations demonstrate the feasibility, efficiency and versatility of the new MSFEM. Originality/value The novel MSFEM solves true three-dimensional eddy current problems in laminated iron cores taking into account of the edge effect.

scholarly journals 3D harmonic modeling of eddy currents in segmented conducting structures

2019 ◽  
Vol 38 (1) ◽  
pp. 2-23 ◽  
Author(s):  
C.H.H.M. Custers ◽  
J.W. Jansen ◽  
M.C. van Beurden ◽  
E.A. Lomonova
Keyword(s):  
Finite Element ◽  
Eddy Current ◽  
Eddy Currents ◽  
Three Dimensional ◽  
Spatial Period ◽  
Content Type ◽  
Current Distributions ◽  
Wide Range ◽  
Conductivity Function ◽  
Electromagnetic Quantities

PurposeThe purpose of this paper is to describe a semi-analytical modeling technique to predict eddy currents in three-dimensional (3D) conducting structures with finite dimensions. Using the developed method, power losses and parasitic forces that result from eddy current distributions can be computed.Design/methodology/approachIn conducting regions, the Fourier-based solutions are developed to include a spatially dependent conductivity in the expressions of electromagnetic quantities. To validate the method, it is applied to an electromagnetic configuration and the results are compared to finite element results.FindingsThe method shows good agreement with the finite element method for a large range of frequencies. The convergence of the presented model is analyzed.Research limitations/implicationsBecause of the Fourier series basis of the solution, the results depend on the considered number of harmonics. When conducting structures are small with respect to the spatial period, the number of harmonics has to be relatively large.Practical implicationsBecause of the general form of the solutions, the technique can be applied to a wide range of electromagnetic configurations to predict, e.g. eddy current losses in magnets or wireless energy transfer systems. By adaptation of the conductivity function in conducting regions, eddy current distributions in structures containing holes or slit patterns can be obtained.Originality/valueWith the presented technique, eddy currents in conducting structures of finite dimensions can be modeled. The semi-analytical model is for a relatively low number of harmonics computationally faster than 3D finite element methods. The method has been validated and shown to be computationally accurate.

Experimental Measurements of Eddy Current Signal From SG Tubes of Fast Breeder Reactor Covered by a Thin Sodium Layer Using a SG Mock-Up

2009 ◽  
Author(s):  
Toshihiko Yamaguchi ◽  
Ovidiu Mihalache ◽  
Masashi Ueda ◽  
Shinya Miyahara
Keyword(s):  
Layer Thickness ◽  
Eddy Current ◽  
Eddy Currents ◽  
Material Surface ◽  
Straight Tube ◽  
Tube Surface ◽  
Experimental Conditions ◽  
Water Steam ◽  
Sodium Layer ◽  
Before And After

In Fast Breeder Reactors (FBR) which are sodium cooled, the steam generator (SG) heat exchanger tubes separate the low pressure sodium flowing in the SG vessel with the high pressure water-steam in tubes. During In-Service Inspection (ISI), sodium is first drained and then SG tubes are cooled down to the room temperature. After sodium draining, due to the high temperature (more than 500 °C), sodium adheres to SG tubes and structures around (SG support plates, welds) in a thin layer, filling eventually the gaps between SG support plates and tubes. During ISI, SG tubes are inspected for cracks and corrosions using differential eddy currents (EC) probes. Due to the high electrical conductivity of sodium adhering to the outer SG tube surface, the eddy current testing (ECT) signal modifies, in accord with sodium layer thickness or sodium deposits located on the outer SG tube surface. The sodium wetting properties depends on several factors as: material surface, temperature and sodium wetting time. The effect of sodium adhering to the outer SG tube on ECT signals were measured using a small mock-up tank (2 m high and 0.7 m in diameter) in which were introduced two SG tubes similar with the ones used in the Monju FBR (one tube is ferromagnetic and made of 2.25Cr–1Mo alloy, while the other one is made of SUS321 and is austenitic). Defects, SG support plates (on both helical and straight part of the tube) and welds were added to tubes and the ECT signal was measured before and after sodium draining. Variations in the sodium layer thickness and consequently its effect on ECT signals were measured by filling and draining the tank three times in order to recreate each time new layers of sodium. The paper describes the experimental conditions and the ECT results for both types of SG tubes by comparing the defects, SG support plates and weld signals before and after draining of sodium. Additionally, sodium structures were examined visually using a VideoScope camera, confirming the recorded ECT signals. The paper also presents details about sodium layer thickness measurements in several parts of SG tubes (near defect, SP, weld, bend, helical tube, straight tube) by scratching and collecting the sodium on a small area of 20mm×20mm. The volume of sodium drops is also estimated. The measurement results showed that there are significant differences in the sodium layer thickness depending on the SG tube material.

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

2018 ◽  
Vol 185 ◽  
pp. 02014 ◽  
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.

Labelling additively manufactured parts by microstructural gradation – advanced copy-proof design

2016 ◽  
Vol 22 (4) ◽  
pp. 630-635 ◽  
Author(s):  
Thomas Niendorf ◽  
Florian Brenne ◽  
Mirko Schaper ◽  
Andre Riemer ◽  
Stefan Leuders ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Additive Manufacturing ◽  
Eddy Current ◽  
Computer Aided Design ◽  
Current Method ◽  
Eddy Current Method ◽  
Content Type ◽  
Current Technique ◽  
Manufacturing Techniques ◽  
Electro Magnetic

Purpose As additive manufacturing techniques, such as selective laser melting, allow for straightforward production of parts on basis of simple computer-aided design files only, unauthorized replication can be facilitated. Thus, identification and tracking of individual parts are increasingly vital in light of globalized competition. This paper aims to overcome the susceptibility of additive manufacturing techniques for product piracy by establishing a method for introducing and reading out product identification markers not visible by naked-eye inspection. Design/methodology/approach Lasers of different nominal power were used for altering the solidification mechanisms during processing in distinct areas of the samples. The resulting local microstructural characteristics and mechanical properties, respectively, were determined by scanning electron microscopy and hardness measurements. The applicability of an advanced eddy current technique for reading out local differences in electro-magnetic properties was examined. Findings The findings show that distinct microstructural features are obtained in dependence of the locally applied laser power. These features manifest themselves not only in terms of grain morphology, texture and hardness but also induce changes in the local electro-magnetic properties. The inscribed pattern can be non-destructively visualized by using an advanced eddy current technique. Originality/value Conventional copy protection basically consists in supplementary labelling or surface modification. In the present study, a new method is proposed for additively manufactured parts, overcoming the drawbacks of the former methods through process-induced microstructure manipulation. Slight alterations in the electro-magnetic material properties can be detected by advanced eddy current method allowing for identification of arbitrary and inimitable component information in additively manufactured parts.

3D-FEM computation and experimental study of eddy currents for characterization of surface cracks

2017 ◽  
Vol 8 (5) ◽  
pp. 603-610 ◽  
Author(s):  
Salaheddine Harzallah ◽  
Mohamed Chabaat
Keyword(s):  
Finite Element ◽  
Eddy Current ◽  
Eddy Currents ◽  
Research Work ◽  
Main Idea ◽  
Shape Reconstruction ◽  
Finite Element Discretization ◽  
3D Fem ◽  
Element Discretization ◽  
Content Type

Purpose The purpose of this paper is to present a new approach for computing by measuring and testing related 3D Eddy currents. In the process, a magnetic vector is formulated from the theoretical setup and obtained results from relevant applications are checked for the consistency of the theory. Besides, cracks detection as well as its propagation is studied through the two parameters: SIF and J-integral. A simulation by a numerical approach using finite-element discretization of 3D governing equations is employed to detect damaged zones and cracks. This approach has been used in the aircraft industry to control cracks. Besides, it makes it possible to highlight the defects of parts while preserving the integrity of the controlled products. Obtained results are compared and agreed with those of other researchers. Design/methodology/approach Finite-element discretization of 3D for solving problem in eddy current testing is presented in this paper. The main idea is the introduction of categorization for the shape reconstruction using the non-destructive testing by 3D-EC. The results are presented for a simple eddy current problem using the finite-element method as an experimental support. Findings In this research work, results of the various cases of simulation have been obtained. From these results of various boxes of simulation, one can conclude that the calculation of the impedance in only one point is not enough to confirm the presence or the absence of a defect for materials. Then, this confirmation leads us to the calculation of the impedance along the plate. The detection of an external defect requires the energy of the sensor by high frequencies .The position of defect (internal, in the middle, external) has a large effect on the impedance. The use of this sensor type in industrial application is frequent because of its precision (minimal error) and its low costs. The major disadvantage of this type of sensor lies in the fact that it is unable to detect a defect. Originality/value This paper fulfills an identified need to detect cracks in materials and eventually to study their propagation.

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

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.

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

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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