Papers by Anastassios Skarlatos
International audienceA 2D numerical model for the solution of the eddy-current induction problem... more International audienceA 2D numerical model for the solution of the eddy-current induction problem in non-linear hysteretic media is presented. The convergence of the iterative algorithm for the inversion of the non-linear operator is discussed. The numerical results are compared with simulations carried our using a commercial finite elements solver. Finally, an experimental procedure for obtaining the input material curves is presented
Sensors, Mar 12, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Proceedings of The Royal Society A: Mathematical, Physical and Engineering Sciences, Feb 29, 2012
The eddy-current induction problem in a conducting half-space with a vertical borehole is studied... more The eddy-current induction problem in a conducting half-space with a vertical borehole is studied and a solution based on modal techniques is presented. Owing to the particular characteristics of the specific geometry, the straightforward application of the truncated region eigenfunction expansion method (a well-established tool for the analytical solution of such problems) presents significant difficulties. Therefore, a modified truncation approach has been adopted that treats the problem in two steps, each one based on the superposition principle. The approach proves to be very efficient and numerically robust. Results for the coil impedance are in excellent agreement with those obtained with the finite-element method. From the engineering point of view, the geometry simulates the eddy-current inspection of fastener holes in aircraft structures when coil scanning is performed from the surface. The presented solution constitutes an important step towards the development of a complete model for fastener hole crack inspections.
arXiv (Cornell University), Sep 25, 2017
The non-linear induction problem in an infinite ferromagnetic pate is studied theoretically by me... more The non-linear induction problem in an infinite ferromagnetic pate is studied theoretically by means of the truncated region eigenfunction expansion (TREE) for the 2D case. The non-linear formulation is linearised using a fixed-point iterative scheme, and the solution of the resulting linear problem is constructed in the Fourier domain following the TREE formalism. The calculation is carried out for the steady-state response under harmonic excitation and the harmonic distortion is derived from the obtained spectrum. This article is meant to be the theoretical part of a study, which will be complemented by the corresponding experimental work in a future communication.
HAL (Le Centre pour la Communication Scientifique Directe), Dec 6, 2017
Product Uniformity Control (PUC): How 15 European research institutes contribute to improve the i... more Product Uniformity Control (PUC): How 15 European research institutes contribute to improve the in-line characterisation of microstructure and mechanical properties in the manufacturing of steel strip
Research and Review Journal of Nondestructive Testing
Weight savings in mobility and transport are mandatory in order to reduce CO 2 emissions and ener... more Weight savings in mobility and transport are mandatory in order to reduce CO 2 emissions and energy consumption. The steel industry offers weight saving solutions by a growing portfolio of Advanced High Strength Steel (AHSS) products. AHSS owe their strength to their largely refined and complex microstructures, containing multiple metallurgical phases. Optimal control of the thermo-mechanical processing of AHSS requires inline sensors for real-time monitoring of evolution and consistency of microstructure and material properties. To coordinate and accelerate European development activities in this domain, the project ”Online Microstructure Analytics (OMA)” was established in 2019, constituting of a consortium of 14 specialised research organisations. The EU-funded OMA project, with a total budget exceeding 6 MEU, focuses on inline sensing techniques to monitor the consistency and homogeneity of microstructure, texture and mechanical properties for automotive steels and in particular...
IEEE Transactions on Instrumentation and Measurement
Magnetic losses in a ferromagnetic lamination can be separated into three contributions. Bertotti... more Magnetic losses in a ferromagnetic lamination can be separated into three contributions. Bertotti theoretically assessed this distribution at the end of the 20th century in the Statistical Theory of Losses (STL), triggering significant progress in understanding the dissipation mechanisms. Recent studies have shown the possibility of reconstructing a hysteresis cycle from the high-frequency Barkhausen noise signal. Applying STL to the Barkhausen noise cycles has never been done before. Still, it could help establish a parallel with the measurement of the magnetization cycle versus frequency and the energy loss. However, STL analysis in its ultimate description requires sinusoidal flux density, while Barkhausen noise measurements are usually done with a constant excitation slope. Multiple magnetic flux density control methods were described in the literature and are reviewed in this manuscript. However, the Barkhausen noise context, requiring high-frequency sampling during the magnetization cycle, is more constraining. Therefore, specific performance criteria were considered, followed by numerical tests to determine the most adapted method to a Barkhausen STL description. Eventually, the Proportional Iterative Learning Control (P-ILC) gave the highest satisfaction rate and was chosen for experimental tests. Some of these experimental results are provided in the manuscript discussion together with suggestions for convergence speed improvement. It is, for instance, recommended to increase the gain near saturation, where the system response is poor.
IEEE Transactions on Magnetics
IET Science, Measurement & Technology, 2021
Materials Science and Engineering: B, 2022
AIP Advances, 2021
Non-destructive magnetic controls are increasing in the industrial field. In this domain, the exp... more Non-destructive magnetic controls are increasing in the industrial field. In this domain, the expectation for simulation tools able to anticipate the magnetic signature, improve the understanding and avoid fastidious and uncertain experimental pre-characterizations is high. Among different methods, the magnetic Barkhausen noise (MBN) control is one of the most popular. MBN raw signal is stochastic, not reproducible, and complex to exploit. MBNenergy, which is obtained by integrating the square of the MBN voltage signal with respect to the time axis is a much more stable indicator. Although the so-called MBNenergy is not, strictly speaking, an energy, it is connected to the domain wall motions and to their kinetic energy. By plotting MBNenergy as a function of H (the tangent surface excitation field), hysteresis cycles are observed. After a rescaling step, B(H) and MBNenergy(H) hysteresis cycles can be compared. They look similar for materials with high magnetocrystalline anisotropy ...
IEEE Transactions on Magnetics, 2020
A combination of the mesh-based finite integration technique with a modal expansion is proposed f... more A combination of the mesh-based finite integration technique with a modal expansion is proposed for the solution of the eddy-current induction problem in geometries involving workpieces with translational or rotational symmetry and an arbitrary 3-D current excitation. The solution is expanded in a series of modes along the symmetry axis, and thus, the reduced Helmholtz equation is discretized and solved independently for each mode in the transversal plane. Finally, the impedance variation of the eddy-current probe is evaluated by means of the reciprocity theorem. The main advantage of the proposed decomposition relies on the use of a 2-D instead of the 3-D grid with the consequent reduction of the numerical noise and the smaller size of the resulting linear system, which allows the simultaneous treatment of different sources.
The uniformity of the microstructure of steel strip over the entire coil length and between diffe... more The uniformity of the microstructure of steel strip over the entire coil length and between different coils of the same grade is key to stable and consistent material behaviour in steel manufacturers’ proprietary processes, like rolling and levelling, and customers’ processes, like pressing and deep-drawing. In particular for high-strength steels, like dual phase and complex phase steels, the microstructure is very sensitive to processing variations resulting in a potentially larger spread in the mechanical properties of the product. In July 2013, a large European consortium consisting of 15 institutes started an RFCS [1] – funded project called “Product Uniformity Control” (PUC) with the primary objective to achieve enhanced and sustained product uniformity of steel strip by improved interpretation of data from inline measurement methods that aim 2 for real-time and non-destructive characterisation of microstructure and technomechanical parameters. Commonly, these techniques are ba...
A fast model for the eddy-current signal calculation of thin cracks at the vicinity of a conducti... more A fast model for the eddy-current signal calculation of thin cracks at the vicinity of a conducting tube edge is presented. The model is based on the surface integral equation formalism using a dedicated Green's function. The approach followed for the construction of the Green's kernel and the primary field is the Truncated Region Eigenfunction Expansion (TREE) method.
This communication presents a first development aiming at efficientlysimulating configurations of... more This communication presents a first development aiming at efficientlysimulating configurations of eddy current thermography for nondestructive applications.The numerical method proposed here is based on the Finite IntegrationTechnique for both electromagnetic and thermal problems a hand. Simulation resultsobtained with two materials are compared and discussed, with respect to thepresence of a flaw affecting the piece under test.
A European consortium consisting of four major steel manufacturers and ten academic technology in... more A European consortium consisting of four major steel manufacturers and ten academic technology institutes has conducted a research and development project, called “Product Uniformity Control“ (PUC) in the period 2013 to 2017. This project aimed to develop and improve non-destructive (inline) measurement techniques to characterise the (uniformity of the) microstructure of steel strip products. In this project, a multitude of strip steel samples from various stages of production have been collected from the four participating steel manufacturers. The samples have been characterised in various ways, namely on their (1) non-destructive measurement parameters using different techniques suited for inline evaluation, (2) fundamental ultrasonic and electromagnetic properties (wave speed, ultrasonic attenuation, magnetisation loops, coercive field), (3) tensile properties (stress-strain curves) and (4) microstructure (by optical micrographs and EBSD images). The correlations between these di...
Induction thermography has become increasingly important for the inspection of stratified metalli... more Induction thermography has become increasingly important for the inspection of stratified metallic structures thanks to its peculiarity of assembling a number of attractive features from the two techniques that it combines, namely the eddy-current testing (ECT) and the infrared thermography (IT). It is contactless, fast and it provides direct (infrared) images. In addition, eddy-current heating through the Joule effect is a very effective and a robust way to thermally excite the medium under consideration without the need of special equipment or couplants. It can be used to detect both surface and volumetric defects like cracks, disbond, delamination and corrosion. The proposed semi-analytical solution is based on the truncated region eigenfunction expansion (TREE) method. The problem is transformed in Laplace domain with respect to time, and the temperature distribution is approximated by its expansion on a tensor product modal basis. This approach, limited to canonical pieces geom...
Thermographic inspection is a popular nondestructive testing (NDT) technique that provides direct... more Thermographic inspection is a popular nondestructive testing (NDT) technique that provides direct images of temperature distribution over large areas at the surfaces of inspected objects. A major application of this method is the inspection of composite materials during manufacturing or in service, in view of detecting delaminations possibly appearing between the layers of the structure [1]. Simulation of these inspections proves useful to complement experimental studies, evaluate the performance of a given setup in terms of detection and support model based algorithms aiming at characterizing flaws. This communication presents a 3D semi-analytical model to address the special case of planar stratified media.
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Papers by Anastassios Skarlatos