Fast Computation Technique of Forces Acting on Moving Permanent Magnet (original) (raw)
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International Journal of Applied Electromagnetics and Mechanics
Lorentz force eddy current testing is a novel nondestructive testing technique which can be applied preferably to the identification of internal defects in non-ferromagnetic moving conductors. This paper describes the comparison of this new technique with well-known eddy current testing. Measurements and numerical simulations have been done for both techniques for artificial subsurface defects in a test specimen made of Aluminum alloy moving with constant velocity.
Fast Analytical Modeling of Eddy Current Non-Destructive Testing of Magnetic Material
Journal of Nondestructive Evaluation, 2013
This article presents the modeling of non-destructive testing systems containing magnetic materials using a fast numerical method. Its main aim consists of correcting the half analytical expression of the impedance variation, formulated by some authors, caused by the presence of a conducting plate below of an absolute ferrite core probe. The obtained results of this correction are found to be consistent and satisfactory comparatively to those of finite element method. It also deals with the study the method rapidity by comparing its simulation time to that of the finite element method. As result, the proposed method is found to be very fast and a very short simulation time is required to calculate the sensor impedance. Indeed, for the studied system the coupled circuit simulation time is lower than 1.09 s. This study is appreciable, since it permits to solve quickly the inverse problem by expressing the physical and geometrical features of the material or defect according to the measured parameters. More importantly, this method is applicable to any axi-symmetric systems and can be adapted for the simulation of three-dimensional configurations.
Oscillatory Motion of Permanent Magnets Above a Conducting Slab
IEEE Transactions on Magnetics, 2015
The present paper provides the 3-D time-dependent analytical solution of the electromagnetic fields and forces emerging if a coil or a permanent magnet moves with a sinusoidal velocity profile relative to a conducting slab of finite thickness. The results can be readily used in application scenarios related to electromagnetic damping, eddy current braking, energy harvesting or nondestructive testing in order to efficiently analyze diffusion and advection processes in case of harmonic motion. The study is performed for rectangular and circular coils as well as for cuboidal and cylindrical permanent magnets. The back reaction of the conductor and therewith associated inductive effects are considered. The solutions of the governing equations and the integral expressions for the time-dependent drag-and lift-force are provided. The analytical results are verified by a comparison to numerical simulations obtained by the finite-element method. The relative difference between the analytically and numerically evaluated force profiles was < 0.1%. Exemplary calculations show that the waveforms of both force components strongly depend on the level of constant nominal velocity v0, the magnitude of the velocity oscillation amplitude v1 and the underlying oscillation frequency fv. His current research interests include numerical simulations and visualization of electromagnetic fields, with applications to forward/inverse problems in nondestructive evaluation, bioelectromagnetics, small electrical machines, and magnetic fluid dynamics.
Lorentz force eddy current testing (LET) is a novel nondestructive testing technique which can be applied preferably to the identification of internal defects in nonmagnetic moving conductors. The paper describes the comparison with established eddy current testing technique. The investigation of the performance of LET has been performed providing a qualified comparison (similar testing conditions) with the classical eddy current testing (ECT). Additionally, numerical simulations have been done. The results are compared with measurements to test the feasibility of defect identification.
Dynamic diagnostics of moving ferromagnetic material with the linear induction motor
ITM Web of Conferences, 2017
The paper presents the application of a three-phase induction motor as a sensor measuring the force of the electromagnetic field connection between the engine and produced sheet steel. The force interaction between the engine and the manufactured sheet metal treated as a treadmill for a linear motor may be an indicator of damage to the material. Detection of places where the sheet does not meet the quality requirements may be very useful in the production process. FEM calculations were performed in the ANSYS MAXWELL environment. The results suggest the possibility of using this type of construction to test the quality of produced materials. The computational results and their analysis are presented in this article.
Numerical Model of Eddy Current Inspection with DC Magnetic Field Associated
Journal of Material Science and Technology Research, 2021
Most non-destructive techniques can be well represented in a virtual environment, in particular, eddy current testing (ECT) simulation is a useful and well-established tool to predict and represent real inspection situations permitting testing customization in a fast, cheap and efficient way. Conventional ECT generally works with low-intensity magnetic fields, however, for advanced variations of the technique, where external DC magnetic fields can be applied to locally decrease the magnetic permeability, there is no Finite Element Method (FEM) packages available to deal with such nonstandard model. Many authors [1] and [2] have presented this ECT solution for different industrial applications using external DC magnetization to carry nonlinear ferromagnetic materials to the saturation level of the magnetization curve to increase the ECT depth penetration. In general, ECT modelling calculation is benefited by properties of steady-state regime where all magnetic fields are oscillating at the same frequency not permitting through multi-frequency calculation. The present work proposes a simulation solution for such a case where DC magnetic field is associated with ECT. A theoretical model is presented together with experimental results validation.
Extended Version of Weak Reaction Approach in Lorentz Force Eddy Current Testing
The Weak Reaction Approach (WRA) represents a technique for numerical calculation of the Lorentz force acting on a permanent magnet moving relatively to a solid electrically con-ducting body. In WRA only the conducting domain is considered, which significantly reduces computational cost. However, the magnetic field of the permanent magnet has to be calculated in advance, preferably analytically. In this paper WRA is extended to cylindrical permanent magnets. A solution is presented for open problem of analytical modeling of cylindrical permanent magnets needed for defect detection in non-magnetic electrical conductors with Lorentz Force Eddy Current Testing (LET). The method of Arithmetic Geometric Mean (AGM) is offered as a fast converging solution to the complete elliptic integrals of first and second kind involved in the solution. Results are presented that verify the accuracy of the AGM method and calculations for the magnetic flux density are performed. Finally, the extended version of WRA is verified with the already well established Quasi Static Approach (QSA) that uses a Finite Element Method (FEM) solution for the magnetic field distribution rather then an analytical one.
Magnetic sensors assessment in velocity induced eddy current testing
This paper presents an enhancement in the probes to be used on a new nondestructive testing method with eddy currents induced by velocity. In this method, a permanent magnet that is attached to a moving carriage creates eddy currents in the conductive material to be inspected. By measuring the opposing magnetic field generated by the eddy currents, it is possible to obtain information regarding the presence of defects. Different magnetic field sensors, such as, differential pick-up coils, giant magneto resistors (GMR) and Hall sensors have been used and compared. A permanent magnet moving above a plate was studied using a numerical model to allow further improvements to be made in the probe. Depending on each sensor's geometry, sensing axis and range, its position and orientation must be strategically chosen in order to increase defect sensitivity. The best probe's position is the one that guarantees the highest sensibility to the defects' presence.