Acceleration of Frequency Sweeping in Eddy-Current Computation

The inductance/impedance due to thin metallic structures in non-destructive testing (NDT) is difficult to evaluate. In particular, in Finite Element Method (FEM) eddy current simulation, an extremely fine mesh is required to accurately simulate skin effects especially at high frequencies, and this could cause an extremely large total mesh for the whole problem, i.e. including, for example, other surrounding structures and excitation sources like coils. Consequently, intensive computation requirements are needed. In this paper, an equivalent-effect phenomenon is found, which has revealed that alternative structures can produce the same effect on the sensor response, i.e. mutual impedance/inductance of coupled coils if a relationship (reciprocal relationship) between the electrical conductivity and the thickness of the structure is observed. By using this relationship, the mutual inductance/impedance can be calculated from the equivalent structures with much fewer mesh elements, which can significantly save the computation time. In eddy current NDT, coils inductance/impedance is normally used as a critical parameter for various industrial applications, such as flaw detection, coating and microstructure sensing. Theoretical derivation, measurements and simulations have been presented to verify the feasibility of the proposed phenomenon.INDEX TERMS Eddy current testing, electrical conductivity, non-destructive testing (NDT), skin effects, thickness measurement.

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“…For the thin structure, with 1 0 <<1 holds, the term −2 0 1 can be substituted with 1 − 2 0 1 ≈ 1 . Then, equation (19) can be approximated as,…”

Section: Figure 2 Geometric Series Of Te Wave Reflection and Transmimentioning

confidence: 99%

An Equivalent-Effect Phenomenon in Eddy Current Non-Destructive Testing of Thin Structures

et al. 2019

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“…There are a number of 3D tetrahedron finite elements meshing softwares, including Cog, Geom Pack90, Grid Gen, Qhull, Tmg, Mesh Maker, and Tet Gen. Tet Gen is easy to compile and has a fast and stable algorithm [27] written in the standard C++ program with good portability.…”

Section: Tetrahedron Meshing For Femmentioning

confidence: 99%

Three-Dimensional Electromagnetic Mixing Models for Dual-Phase Steel Microstructures

et al. 2018

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Linking the ferrite fraction in a dual-phase (DP) steel microstructure and its electromagnetic properties is critical in the effort to develop on-line measurement techniques for phase transformation using electromagnetic (EM) sensors. This paper developed a seamlessly integrated method for generating 3D microstructures and evaluating their equivalent permeability values. Both the generation of 3D microstructures and evaluation of equivalent permeability have been achieved through custom modelling packages developed by the authors. Voronoi modelling based on the random close packing of spheres (RCPS-VM) was used to precisely control the ferrite fraction in DP steel microstructure, and an equivalent uniform field method for 3D finite element simulation was developed for efficient analysis.

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“…LECTROMAGNETIC eddy current testing (ECT) has been commonly used for diverse applications of the sample checking, including measuring the properties inhomogeneity, surface inspection in order to further improve the product quality [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Besides the ECT method, other non-destructive testing techniques like ultrasonic have been wildly used [21], which is more preciously on the surface inspection of metals.…”

Section: Introductionmentioning

confidence: 99%

Thickness Measurement of Metallic Film Based on a High-Frequency Feature of Triple-Coil Electromagnetic Eddy Current Sensor

Lü¹,

Chen²,

Meng³

et al. 2020

Preprint

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Previously, various techniques have been proposed for reducing the lift-off effect on the thickness measurement of the non-magnetic films, including the peak-frequency feature and phase feature in the Dodd-Deed analytical formulation. To realise a real-time feedback response on the thickness monitoring, the phase term in the Dodd-Deeds formulation must be taken off the integration. Previous methods were based on the slow change rate of the phase term when compared to the rest of the term – the magnitude term. However, the change rate of the phase term is still considerable for a range of working frequencies. In this paper, a high-frequency feature has been found. That is, the ratio between the imaginary and real part of the phase term is proportional to the integral variable under high frequencies. Based on this proportion relationship, the phase term has been taken out; and a thickness algorithm has been proposed. By combing the measured impedance from the custom-built sensor (three coils), the thickness of the metallic film can be reconstructed. Experiments have been carried out for the verification of the proposed scenario. Results show that the thickness of the metal film can be reconstructed with a small error of less than 2 %, and immune to a reasonable range of lift-offs.

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Acceleration of Frequency Sweeping in Eddy-Current Computation

Cited by 63 publications

References 20 publications

An Equivalent-Effect Phenomenon in Eddy Current Non-Destructive Testing of Thin Structures

An Equivalent-Effect Phenomenon in Eddy Current Non-Destructive Testing of Thin Structures

Three-Dimensional Electromagnetic Mixing Models for Dual-Phase Steel Microstructures

Thickness Measurement of Metallic Film Based on a High-Frequency Feature of Triple-Coil Electromagnetic Eddy Current Sensor

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