International Journal of Applied Electromagnetics and Mechanics - Volume 59, issue 4

Authors: Theodoulidis, Theodoros

Article Type: Research Article

Abstract: An exact method is presented for calculating the impedance of a coil above a planar conductor with a conductivity profile that varies with depth. The method can be applied to arbitrary continuous profiles and in terms of accuracy or scope it is advantageous over the existing approaches, namely the analytical approach involving the solution of the relevant differential equation in terms of higher transcendental functions and the numerical approach involving the piecewise approximation of the continuous conductivity profile. The method is also very fast and in the context of eddy current nondestructive evaluation it can be readily applied to invert …conductivity profiles from coil impedance measurements. Show more

Keywords: Eddy current testing, analytical modeling, continuous conductivity profile

DOI: 10.3233/JAE-171122

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1179-1185, 2019

Authors: Wu, Jianbo | Xia, Hui | Feng, Bo | Li, Erlong | Huang, Xiaoming | Kang, Yihua

Article Type: Research Article

Abstract: In high-speed scanning MFL inspection for a steel pipe, according to Lenz’s Law, motion-induced eddy current (MIEC) is induced by relative movement between axial magnetizer and the inspected pipe. On the one hand, magnetic field generated by MIEC will change the magnetization intensity of the pipe and thereafter change the signal amplitude; on the other hand, it will also cause signal baseline shift by altering background magnetic field. In this paper, the effect of MIEC on axial MFL inspection is investigated by theoretical analysis, finite element simulations, and high-speed experiments. It is found that at different locations MIEC causes different …change trends for both the background magnetic field and magnetization intensity, leading to sensitivity difference, which should be taken into consideration in the high-speed MFL inspection for a steel pipe. Show more

Keywords: Steel pipe, high-speed magnetic flux leakage (MFL) inspection, motion-induced eddy current (MIEC) and signal characteristics

DOI: 10.3233/JAE-171101

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1187-1193, 2019

Authors: Xu, Xiaojuan | Ji, Hongli | Qiu, Jinhao | Takagi, Toshiyuki

Article Type: Research Article

Abstract: This paper presents a traditional eddy current testing (ET) method to estimate the off-axis of lay-up in the cross-ply and multidirectional carbon fiber reinforced polymer (CFRP) laminates. The transmitter receiver (TR) probe equipped with two identical circular coils was utilized to scan surface of the CFRPs with artificially induced off-axis layers in different depths. A 2D fast Fourier transform (2D-FFT) was applied to the C-scan experimental images for determining the layer orientation. It was observed that several highlighted lines are located at different directions in the Fourier transform images, which correspond to the higher energy and indicate a periodicity in …the corresponding direction. From these images, the layer orientation with a minimum −5° off-axis was measured, and the actual fibers direction 40° can be obtained by subtracted 90° from the frequency angle in the Fourier transform image. Additionally, mechanism of the output signal change caused by the off-axis lamina was analyzed using the finite element (FE) analysis. Numerical results showed that deformation of the space magnetic field occurs because of the redistribution eddy current induced in the off-axis lamina, which implies the possibility to measure and estimate the deviated fibers orientation of the CFRPs using the traditional ET method. Show more

Keywords: Eddy current testing, carbon fibers, lay-up orientation, off-axis, electrical properties

DOI: 10.3233/JAE-171060

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1195-1202, 2019

Authors: Okolo, Chukwunonso K. | Meydan, Turgut

Article Type: Research Article

Abstract: This paper reports on a quantitative technique based on the Magnetic Flux Leakage (MFL) method, for the detection and interpretation of the MFL signals caused by rectangular hairline cracks in pipeline structures. This was achieved through visualization and 3D imaging of the leakage field. This research is aimed at detecting hairline cracks caused by granular bond separation, which occurs during manufacturing, leaving pipelines and steel structures with miniature cracks. The investigation compared finite element numerical simulation with experimental data. The response of the MFL probe scanned above a hairline crack was first predicted using an optimized 3D finite element model. …The MFL signals associated with both the surface and far-surface cracks were compared. The results show that the depth, width and length of the various hairline cracks can be estimated by using the distribution pattern and strength of the (B x ), (B y ) and (B z ) components of the MFL signals. Show more

Keywords: Defects, finite element modelling, Hall Effect Sensor, magnetic flux leakage, pipeline, steel plate

DOI: 10.3233/JAE-171047

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1203-1211, 2019

Authors: Matsumoto, Takanori | Uchimoto, Tetsuya | Takagi, Toshiyuki | Dobmann, Gerd | Oozono, Shinji | Yuya, Hideki

Article Type: Research Article

Abstract: This paper describes eddy current magnetic signature (EC-MS) method that can evaluate small plastic deformation in carbon steels with high accuracy. In EC-MS method, an incremental magnetic field is superimposed on a magnetization field, and the directions of the incremental field to the magnetization field changes, depending on experimental setups. The objective of this study is to investigate the influence of the measurement conditions on experimental results of EC-MS method. Tensile test specimens are measured by EC-MS method with different directions of the incremental field parallel and perpendicular to the magnetization one. Furthermore, the dependence on the static/quasi-static magnetization field …is discussed comparing a continuous waveform of the magnetization field with a stepwise one. Show more

Keywords: Electromagnetic nondestructive evaluation, plastic deformation, magnetic incremental permeability, eddy current magnetic signature, measurement condition

DOI: 10.3233/JAE-171046

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1213-1220, 2019

Authors: Pelkner, Matthias | Casperson, Ralf | Pohl, Rainer | Munzke, Dorit | Becker, Ben

Article Type: Research Article

Abstract: The application of composite pressure vessels is of great interest due to tremendous weight saving. Nevertheless, ageing of CFRP (carbon fiber reinforced plastic) composites pressure vessels underlies complex interactions between metallic liner and composite and is not fully understood yet. One main challenge is the application of appropriate testing methods for detecting the influences of pressure cycles and creep behavior on the material. This contribution presents results achieved by using conventional eddy current testing (ET) and high frequency ET. Here, we could show that also conventional ET with low frequencies are useable to investigate pressure vessels of different material combinations …like aluminum-CFRP and synthetics-CFRP. Show more

Keywords: CFRP, eddy current, ageing, composite, pressure vessel

DOI: 10.3233/JAE-171044

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1221-1226, 2019

Authors: Kosukegawa, Hiroyuki | Kiso, Yuta | Yoshikawa, Yuki | Urayama, Ryoichi | Takagi, Toshiyuki

Article Type: Research Article

Abstract: Laminated structure (fiber orientation and boundary of adjacent layers) on scarfed surface of CFRP is characterized by eddy current testing (ECT) with differential type probe. The fiber orientation of each layer is identified by C-scanning of ECT. The peak of eddy current signal amplitude on each layer, which is shifted toward the upper side layer due to the distribution of eddy current, indicates the boundary of the adjacent layers. Because the peak of the eddy current signal is well represented by electromagnetic numerical simulation of finite element analysis, the boundary of the adjacent layers is correctly identified by combining ECT …and numerical analysis. These abilities of ECT are useful for automation of scarf adhesive repair process. Show more

Keywords: Eddy current testing, scarf adhesive repair, automation

DOI: 10.3233/JAE-171222

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1227-1238, 2019

Authors: Prémel, Denis | Granet, Gérard

Article Type: Research Article

Abstract: This paper concerns the development of a semi-analytical model dedicated to the fast computation of the response of a 3D Eddy Current (EC) probe scanning a planar conductor of complex shape. The workpiece is characterized by a finite number of complex interfaces k , 1 ≤ k ≤ N , each one being defined by any 2D arbitrary surface a k (x , y ). A previous semi-analytical model based on the Curvilinear Coordinate Method (CCM) has been presented for the computation of quasi-static fields induced by any 3D EC probe scanning a half-space of complex shape. This …paper gives a natural extension of this preliminary work. CCM consists in introducing a change of coordinates in order to be able to write analytically and easily boundary conditions separating two media. No mesh is needed, nevertheless, the covariant form of Maxwell’s equations is required due to a novel generalized metric space. Boundary conditions at multiple interfaces are efficiently implemented thanks to the S-matrix algorithm. Finally, some numerical experiments show the validity of the numerical model by some comparison between simulated data obtained by a FE commercial code and those provided by the proposed numerical model. Show more

Keywords: Covariant form of Maxwell’s equations, eddy current simulation, Eddy current nondestructive testing

DOI: 10.3233/JAE-171218

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1239-1245, 2019

Authors: Ye, Chaofeng | Rosell, Anders | Haq, Mahmoodul | Stitt, Erik | Udpa, Lalita | Udpa, Satish

Article Type: Research Article

Abstract: This paper presents an eddy current (EC) probe with orthogonal excitation coils that can change the exciting current direction electrically and tunnel magnetoresistive (TMR) sensor for inspection of stacked CFRP. As CFRP is electrically anisotropic, eddy current excited along the fiber direction is stronger than in other directions. A high sensitivity TMR sensor located at the center of the two orthogonal coils measures the z component of induced magnetic field (Bz) which constitutes the probe signal. The output of the sensor is 0 if the induced currents are symmetric about the sensor. Signals of defects in different orientations depend on …the direction of the exciting current. The operation of the probe is validated using a finite element model. A prototype was built and experimental results from CFRP sample with defects in different orientations are presented and analyzed. Show more

Keywords: Eddy current, CFRP, TMR

DOI: 10.3233/JAE-171193

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1247-1255, 2019

Authors: Rymarczyk, Tomasz | Tchórzewski, Paweł

Article Type: Research Article

Abstract: The paper presents a solution for testing the humidity of a brick wall using electrical tomography. Different prototypes of measurement systems based on the device with hybrid tomography were prepared. Prepared constructions contain 16 electrodes in a brick wall on one side and two-sided. Electrical tomography, which is based on the measurement of potential difference, can be used to check historical buildings. The way in which we can determine the condition of a wall of moisture depends on the fact that each material has a unique conductivity. The use of modern tomographic techniques in combination with topological algorithms will allow …non-destructive and non-destructive very accurate spatial assessment of the humidity level. The proposed application uses the Total Variation, Gauss–Newton and level set method to solve the inverse problem in electrical tomography. Show more

Keywords: Electrical tomography, inverse problem, level set method, hybrid methods

DOI: 10.3233/JAE-171151

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 4, pp. 1257-1265, 2019