Lorentz force evaluation: A new approximation method for defect reconstruction

Petković, Bojana; Haueisen, Jens; Zec, Mladen; Uhlig, Robert P.; Brauer, Hartmut; Ziółkowski, Marek

doi:10.1016/j.ndteint.2013.05.005

Cited by 25 publications

(13 citation statements)

References 22 publications

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“…The gain matrix [K]AR 3M Â S describes the linear relation between the current dipoles and the measurement points (Petkovic et al, 2013). It has to be mentioned that the conductivity distribution {s} in (7) corresponds to the DRS, i.e.…”

Section: Let: a Novel Nde-techniquementioning

confidence: 99%

Lorentz force eddy current testing: a novel NDE-technique

Brauer

Porzig

Mengelkamp

et al. 2014

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering

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Purpose -The purpose of this paper is to present a novel electromagnetic non-destructive evaluation technique, so called Lorentz force eddy current testing (LET). This method can be applied for the detection and reconstruction of defects lying deep inside a non-magnetic conducting material. Design/methodology/approach -In this paper the technique is described in general as well as its experimental realization. Besides that, numerical simulations are performed and compared to experimental data. Using the output data of measurements and simulations, an inverse calculation is performed in order to reconstruct the geometry of a defect by means of sophisticated optimization algorithms. Findings -The results show that measurement data and numerical simulations are in a good agreement. The applied inverse calculation methods allow to reconstruct the dimensions of the defect in a suitable accuracy. Originality/value -LET overcomes the frequency dependent skin-depth of traditional eddy current testing due to the use of permanent magnets and low to moderate magnetic Reynolds numbers (0.1-1). This facilitates the possibility to detect subsurface defects in conductive materials.

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Section: Let: a Novel Nde-techniquementioning

confidence: 99%

Lorentz force eddy current testing: a novel NDE-technique

Brauer

Porzig

Mengelkamp

et al. 2014

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering

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“…In order to pick up the perturbations of eddy currents due to defects, magnetic sensors are used to pick up the perturbation field [ 7 , 15 , 16 , 17 , 18 ]. Alternatively, force sensors can also be used to measure the Lorentz forces that are associated with eddy currents [ 18 , 19 ].…”

Section: Introductionmentioning

confidence: 99%

Comparison of Inspecting Non-Ferromagnetic and Ferromagnetic Metals Using Velocity Induced Eddy Current Probe

Feng

Ribeiro

Rocha

et al. 2018

Sensors

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A velocity induced eddy current probe has been used to detect cracks in both non-ferromagnetic and ferromagnetic metals. The simulation and experimental results show that this probe can successfully detect cracks in both cases, but further investigation shows that the underlying principles for inspecting non-ferromagnetic and ferromagnetic metals are actually different. For an aluminum plate, the induced eddy current density and the signal amplitude both increase with probe speed, which means the signal is caused by velocity induced eddy currents. For a steel plate, probe speed changes the baselines of the testing signals; however, it has little influence on signal amplitudes. Simulation results show that the signal for cracks in a steel plate is mainly caused by direct magnetic field perturbation rather than velocity induced eddy currents.

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“…LFE is a newly developed nondestructive testing 29 technique for detection and reconstruction of defects in laminated electrically conductive materials 30 [1,2]. A conductive specimen moves with constant velocity v with respect to a permanent magnet 31 ( Fig.…”

mentioning

confidence: 99%

“…An approximation of a complex-shaped permanent magnet with one magnetic dipole as in [1] provides 60 a sufficient solution of the magnetic field only at large distances [4]. Analytical descriptions of the 61 magnetic field are of great interest [5][6][7][8][9][10][11][12][13][14][15][16].…”

mentioning

confidence: 99%

“…In contrast to the (αo,βo)-MDMs, the optimal number 325 of layers for the (αs,βs)-MDMs can be calculated with respect to the results of a least squares fit section we investigate how the dipole optimization influences the error of the forward calculated 330Lorentz forces exerted on the permanent magnet. We embed the MDMs with optimized positions (αo-331MDMs) corresponding to NRMSE o G,min of the cuboidal permanent magnet obtained in Section 3.1 and 332 the αs-MDMs with the same (Na,Nh)-combinations into an existing approximate forward solution for 333 LFE from[1]. Further, we put the charge model (Section 2.2,Fig.…”

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confidence: 99%

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Permanent Magnet Modeling for Lorentz Force Evaluation

et al. 2015

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10Lorentz Force Evaluation (LFE) is a technique to reconstruct defects in electrically conductive materials. 11The accuracy of the forward and inverse solution highly depends on the applied model of the permanent 12 magnet. The resolution of the technique relies upon the shape and size of the permanent magnet. Further, 13 the application of an existing forward solution requires an analytic integral of the magnetic flux density. 14 Motivated by these aspects we propose a magnetic dipoles model, in which the permanent magnet is 15 substituted with an assembly of magnetic dipoles. This approach allows modeling of magnets of 16 arbitrary shape by appropriate positioning of the dipoles and the integral can be expressed by elementary 17 mathematical functions. We apply the magnetic dipoles model to cuboidal and cylindrically shaped 18 magnets and evaluate the obtained magnetic flux density by comparing it to reference solutions. We 19 consider distances of 2-6 mm to the permanent magnet. The representation of a cuboidal magnet with 20 832 dipoles yields a maximum error of 0.02 % between the computed magnetic field of the magnetic 21 dipoles model and the reference solution. Comparable accuracy for the cylindrical magnet is achieved 22 with 1890 dipoles. Additionally, we embed the magnetic dipoles model of the cuboidal magnet into an 23 existing forward solution for LFE and find that the errors of the magnetic flux density are partly 24 compensated by the forward calculations. We conclude that our modeling approach can be used to 25 determine the most efficient magnetic dipole models for LFE. 26 0018-9464 (c) component Lorentz forces exerted on the conductor. Instead of determining the Lorentz forces on the 37 moving conductor we measure the forces exerted on the fixed permanent magnet. Due to Newton's third 38 axiom they have equal magnitude but opposite direction as the Lorentz forces on the conductor. The 39 presence of a material defect of dimensions L×W×H and depth d in the conductor yields perturbations 40 in the induced eddy currents and, consequently, in the force signals. Based on the force perturbations 41 the geometry of the defect can be reconstructed by solving an inverse problem. Inverse calculations 42 require knowledge of a forward solution to calculate force signals based on a model of the permanent 43 magnet, the conductive specimen and the relative movement. An existing approximate analytic forward 44 solution is described in [1]. In this forward solution the permanent magnet is represented by one 45 magnetic dipole. 46 47 Fig. 1: Experimental setup for Lorentz Force Evaluation. A laminated conductive specimen moves with constant 0018-9464 (c)

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Lorentz force evaluation: A new approximation method for defect reconstruction

Cited by 25 publications

References 22 publications

Lorentz force eddy current testing: a novel NDE-technique

Lorentz force eddy current testing: a novel NDE-technique

Comparison of Inspecting Non-Ferromagnetic and Ferromagnetic Metals Using Velocity Induced Eddy Current Probe

Permanent Magnet Modeling for Lorentz Force Evaluation

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