Values Of Magnetic Permeability Research Articles

Influence of Magnetic Polarization on Diagrams of Inductive and Electromagnetic Logs

Abstract ––We present the results of the study of the effect of induced magnetic polarization of clay beds under the influence of an external harmonic electromagnetic field (frequencies 70 and 875 kHz). A two-stage numerical modeling procedure is proposed. At the first stage we determine the effective relative magnetic permeability of a synthetic sample with inclusions of clay particles. In this case a 3D heterogeneous mesh sample is generated. Then we numerically model a spatial distribution of an electric field. The electromotive force (EMF) induced in the measuring coil is calculated from this distribution. Relative magnetic permeability is determined by comparison with EMF of homogeneous samples with different values of magnetic permeability. It has been found that during the electric field excitation by an alternating current coil, the effect of induced magnetic polarization appears in the sample with clay particles. Its manifestation is that the effective magnetic permeability becomes complex. At the second stage we calculate the EMF diagram of the three-coil logging probe in the macro-model ‘clay cap – reservoir’. Magnetic permeability of the clay cap is given by a complex value. In the generated logs, extremes appear in the vicinity of the bottom of the clay cap; they do not correspond to the distribution of electrical conductivity and magnetic permeability in the given model. They can be incorrectly interpreted when analyzing real logs into individual formations. Numerical modeling at all stages is performed by the Vector Finite Element Method on a consistent adaptive tetrahedral partition and the first-order Webb vector basis.

Parameter Features of a Metasolenoid on a Polymer Thread with Chains of Irregular Aluminum Nanoislands

The article evaluates the possibility of presenting a polymer thread made of fibers of carbon benzene rings with chains of irregular aluminum nanoislands as a metamaterial with a negative value of magnetic permeability (MNG-materials).

Demonstration of the refraction of magnetic field lines in a magnetic material

Teaching physics needs effective educational demonstrations for each important section, which allow organising intensive learning activity of students and confirming or substantiating the theory being studied. However, in a number of cases, such demonstrations are not available for purely technical reasons: the difficulty of organisation, the lack of instruments and materials suitable for conducting simple educational experiments. The impossibility to demonstrate the effect of refraction of magnetic field lines at the boundaries of magnets is due to the absence of materials with a convenient value of magnetic permeability μ of the order of several units. This article describes a simple method for obtaining material with an effective macroscopic value of μ r ∼ 2 and provides the results of the related lecture demonstrations.

Analytical formula of the mutual impedance of a partial core transformer with conductive tapes

The present work shows a first approximation of the analytical model of the mutual impedance of a transformer with a partial cylindrical core considering the effective tensor values of magnetic permeability and electrical conductivity. This first model is based on the use of constant values to represent the effective relative permeability of the core material of this transformer. The analytical expressions obtained allow modeling the mutual impedance values for the following cases: filamentary conductor, conductors with a rectangular cross-section and for a two-coil device.

Volumetric water content estimation of concrete by particle swarm optimization of GPR data

This study investigates the Volumetric Water Content (VWC) of concrete block by inversion of Ground-penetrating radar (GPR) traces by Particle Swarm Optimization (PSO) method. PSO method was applied to GPR data set, which contains 24 days of data. PSO was used as a tool to estimate relative dielectric permittivity, relative magnetic permeability and electrical conductivity values of concrete. The relative dielectric permittivity has a direct relationship with the water content. Generally, the relative dielectric permittivity value is estimated from velocity estimation by picking reflections on radargrams. However, the picking of reflection may be erroneous and subjective. In this case, this study was aimed on PSO method as an inversion tool to estimate relative dielectric permittivity to calculate VWC of concrete instead of velocity calculation approach to avoid man-made error during first arrivals picking. Firstly, PSO application on the 3rd day data of the fresh concrete was introduced in detail. Afterwards, PSO results on all data set were presented. In order to show the accuracy of PSO calculations, the percentages of relative error (%RE) values, which indicate the fit between observed and calculated GPR traces, were estimated. %RE values were varied between 3.11% and 6.05%. After the PSO process, estimated dielectric permittivity values were used to calculate the VWC. So, the PSO application was utilized to monitor water content change of concrete. Nevertheless, besides the traditional methods, the information on the water content can be obtained with the proposed method non-destructively.

Implicit iteration calculations using 3D field analyses, to predict the power loss in powder ferromagnets, with their measurement tests

An implicit iterative calculation model with 3D magnetic field analysis has been developed to predict the power losses in the sintered ferromagnetic powders. The integral parameters of the magnetic field such as the losses due to eddy currents and hysteresis ones were calculated for different frequencies and magnetic flux density values. Such prediction of the losses is helpful as the data provided in catalogues is measured for strictly limited ranges of flux density and operation frequency. Moreover, the manufacturers don't give the electrical conductivity and magnetic permeability values of the magnetic cores from the aforesaid materials needed for 3D magnetic field analyses, where ferromagnetic particles cannot be separately included due to enormous computational efforts. The simulated losses in the cores were tested for the magnetically soft composite (SMC) called Somaloy as well as for ferrite cores. A good conformity of the simulated core losses with the measured values was obtained.

Effect of plastic deformation on the phase composition and electromagnetic characteristics of the 321N austenitic steel (08Kh18N10T)

The changes in the phase composition and electromagnetic properties of the 321N chromium-nickel austenitic steel under plastic deformation by uniaxial tension are studied. As strain increases from 0 to 0.37, the content of ferromagnetic α′-martensite in the steel increases monotonically to 60%. The electrical resistivity and the initial magnetic permeability increase monotonically by factors of 1,25 and 18, respectively. To monitor the strain state and the content of α'-martensite in products made of the 321N steel, it is preferable to use initial magnetic permeability rather than electrical resistance. The skin layer thickness of the deformed 321N steel for frequencies from 5 to 1000 kHz is calculated from the experimental values of initial magnetic permeability and electrical resistivity. Eddy current diagnostics of the state of the surface of products made of this steel, hardened by surface plastic deformation, is proposed to be performed at frequencies ranging between 100 and 200 kHz.

The use of finite elements modeling to analyze phase shifting transformer in steady-state service conditions

PurposeThe aim of this paper is to find a fast-acting numerical model of the phase shifter.Design/methodology/approachThe 3D FE model of the investigated unit is presented and compared with the results of the measurements. Due to its size, it is not suitable for transient analyses. The simplified 2D finite elements approach is discussed afterwards, with the identity of the magnetic energy stored in both models as the criterion of similarity between 2D and 3D models.FindingsThe introduction of scaling factors for the magnetic permeability values in particular volumes of the two-transformer set of the phase shifter enabled acceptable accuracy in calculations of the basic exploitation parameters of the phase shifter.Research limitations/implicationsThe developed methodology allows the analysis of the exploitation conditions of two separated transformers connected in a power grid inside the single finite elements model.Originality/valueAlthough the numerical models of power transformers are extensively discussed in the literature, the usage of the equivalent fast 2D model for the representation of two cooperating transformers at load conditions was not published yet.

Ultrasonically assisted solvohydrothermal synthesis of nanocrystalline Zn-Ni ferrite advanced material for EMI shielding

Magnetic oxides, especially Zinc-Nickel (Zn-Ni) ferrites, are used in devices that transmit and receive electromagnetic signals. We present the synthesis of Zn-Ni ferrite, Nickel ferrite and Zinc ferrite by sonochemically assisted solvohydrothermal method. The elemental analysis revealed that the content of Zn ion in the Zn-Ni ferrite is more. The VSM results displayed superparamagnetic behaviour of Zn-Ni ferrite which could be attributed to smaller particle size. Electromagnetic interference (EMI) shielding materials which dominantly shield by absorption mechanism contain both electric and magnetic dipoles. This is an intrinsic feature of Zn-Ni ferrite materials as it has both high value of magnetic permeability and dielectric constant. The higher contribution of absorption makes it a useful material for various applications such as Radar Absorbing Materials (RAMs). Total shielding efficiency of 28.5 dB for Ni-Ferrite and 30.5 dB for Zn-Ni-Ferrite in X band were obtained, all of which was dominated by shielding efficiency due to absorption. This implies more than 99.99% incident microwaves were successfully attenuated by the materials.

A Simplified 2-D Equivalent Model for Magnetic Wire Array

Demagnetization factor and corresponding apparent permeability for multiwire arrays using the 3-D finite element method (FEM) are calculated in this article. The effect of distance between magnetic wires on the demagnetization factor and apparent magnetic permeability is studied for various values of relative magnetic permeability. The simulations are compared with experimental results on arrays up to 91 wires. A novel simplified equivalent 2-D model for wire arrays is presented in this article, as a fast method for calculations. The simplified axisymmetrical model consists of a set of hollow cylinders with equivalent volume. The results of the proposed simplified 2-D model fit very well the full 3-D FEM simulations and experimental results. Two different hexagonal and square arrangements for wires are considered both for the simulations and the measurements.

Optimization of the Guiding Stability of a Horizontal Axis HTS ZFC Radial Levitation Bearing

This document presents a study on the optimization of the 3D geometry of a horizontal axis radial levitation bearing with zero-field cooled (ZFC) high-temperature superconductor (HTS) bulks in the stator, and radially magnetized permanent magnet (PM) rings in the rotor. The optimization of component dimensions and spacing to minimize the volume or cost concerning only the maximization of the levitation force was previously studied. The guidance force and guiding stability depend on the spacing between PM rings in the rotor and between the rings of HTS bulks in the stator. This new optimization study aims to find the optimum spacing that maximize the guidance force with given HTS bulk and PM ring dimensions while maintaining the minimum required levitation force. Decisions are taken using the non-dominated sorting genetic algorithm (NSGA-II) over 3D finite element analysis (FEA). A simplified electromagnetic model of equivalent relative permeability is used on 3D FEA to reduce numerical processing and optimization time. Experimental prototypes were built to measure magnetic forces and validate appropriate values of equivalent magnetic permeability. An analysis of stable and unstable geometry domains depending on the spacing between rings of HTS bulks and PM rings is also done for two HTS bulk sizes.

The effect of plasma arc discharge process parameters on the properties of nanocrystalline (Ni, Fe)Fe2O4 ferrite: Structural, magnetic, and dielectric studies

In this work, an attempt is made on optimization process parameters of the plasma arc discharge technique, including electrical current, atmosphere, and chamber pressure to synthesize nanocrystalline (Fe, Ni)Fe2O4 ferrite powders. The process was performed at the air and oxygen atmosphere with the applied arc current varying from 300 to 500 A and the chamber pressure of 1 and 2 atm. After establishing an arc between the electrodes, the as-synthesized powders were collected, and structure, magnetic, electromagnetic, and dielectric properties were examined in detail. The results show the highest value of the magnetic spinel phase (38.32 wt%) and saturation magnetization (35.1 emu/g) is obtained at the air atmosphere using an applied electrical current and chamber pressure of 400 A and 1 atm, respectively. The powders prepared in these processing conditions also exhibit the highest dielectric constant value over all the frequency ranges. Nevertheless, the powder synthesized at oxygen atmosphere in the applied electrical current of 400 A and chamber pressure of 1 atm shows the highest value of magnetic permeability over a wide range of frequency which is almost two times higher than that of the powders synthesized at the air atmosphere.

Induction Infrared Thermography for Non-destructive Evaluation of Welding-Induced Sensitization in Stainless Steels

For medium- and high-carbon stainless steels, welding can induce sensitization in the heat affected zone (HAZ) adjacent to the weld, where chromium carbide $$(\hbox {Cr}_{23}\hbox {C}_{6})$$ precipitates out of the bulk metal and accumulates at the grain boundaries. This chromium depletion and precipitate accumulation at grain boundaries makes the alloy susceptible to intergranular corrosion, environmentally assisted cracking, and broader fracture. In this paper, we investigate the efficacy of using induction infrared thermography (IIRT) as a non-destructive method for detecting welding-induced sensitization, using the AISI 440C steel as an example. We start by presenting a laboratory experiment to demonstrate this approach, using a radio frequency function generator, an induction wand, and a FLIR SC8203 infrared camera. We use traditional metallography techniques and scanning electron microscopy (SEM) to identify the location of any sensitized regions and characterize the corresponding microstructure. The IIRT experimental results reveal a distinguishable heat signature, with higher temperature observed within the sensitized regions. Next, we present a computational study to simulate the IIRT experiment and investigate the underlying physics. We adopt a three-dimensional thermo-electro-magnetic model including Fourier’s law of heat conduction and Maxwell’s equations for predicting the electromagnetic field caused by a sinusoidal excitation current flowing through the induction coil. We solve the system of governing equations using the commercial solver COMSOL Multiphysics. To numerically investigate the possible causes of the disproportionate heating within the sensitized regions, we realistically vary the values of electrical resistivity and magnetic permeability therein. The simulated results indicate that the heat signature observed in the laboratory experiment may result from the increase of both electrical resistivity and magnetic permeability in the HAZ. The possible physical relationships between sensitization and the variation of these two properties are discussed.

Can Isotropic Negative Permittivity ε and Permeability μ Metamaterials Exist?

An attempt is made to answer the question posed in the title. Periodic metamaterials, namely, cubic photonic crystals with dielectric inclusions (including those with metallic properties), methods for introducing material equations (homogenization), and the possibility of describing metamaterials by scalar permeability and permittivity (or two scalar parameters) including negative values of their real parts, are considered. For photonic crystals, the Landau conclusion about the absence of high-frequency (optical) magnetic properties is confirmed. In particular, negative values of magnetic permeability or any of its components are impossible. Configurations of metamaterials with almost isotropic properties are presented without regard for spatial dispersion.

Study of the skin depth in different metallic atoms

This study is a theoretical method for computation skin depth in different metallic atoms. A MATLAB m-file is developed and used to compute the skin depth of Gold, Copper and Silver. It was found that an inversely relationship between the skin-depth with the frequency, conductivity and square root of permeability. The depth of the skin layer depends not only on the conductivity of the material and frequency, but also on the effective value of magnetic permeability, which in turn is a function of frequency. Silver and Copper have higher conductivity than that of Gold. The most electrically conductive element is Silver, followed by Copper and Gold. Silver, Copper and Gold skin depth vs. intensity of current vector has been plotted and discussed.

Study of transmission characteristics of disk transducer in the radially propagated Rayleigh wave excitation mode

A mathematical model of a capacitive ultrasonic transducer is designed allowing to emit ultrasonic vibrations into an electrically conductive product. The influence of a polarizing electrostatic field on the Coulomb forces formation in the surface layer of a metal sample is determined. A closed solution to the electrostatics problem is obtained for a piecewise homogeneous medium in which a half-space is filled with metal having finite values of electrical conductivity and magnetic permeability. An expression is obtained for calculating the surface density of a static electric charge on the metal sample surface. As part of the mathematical model of a capacitive sensor in the mode of converting electric energy to high-frequency mechanical (ultrasonic) energy in metals, closed solutions for electrostatics and electrodynamics problems are constructed in relation to a piecewise-homogeneous medium in which a half-space is filled with metal having finite values of electrical conductivity and magnetic permeability. It is determined that a capacitive disk transducer excites forces acting normally to the surface of electrically conductive products. A quantitative assessment of the surface density of the Coulomb forces is made. The main factors determining the sensitivity of a capacitive disk transducer are specified. As an example of using the simulation results, the amplitude factor of radially propagating Rayleigh waves is calculated. The concept of the wave characteristics of the transducer in the excitation mode of ultrasonic surface waves is introduced.

Research of the properties of magnetic fillers of cylindrical shape

It has been noted that the information on magnetic properties of specific magnets available in the design and operation of magnetic separators/analyzers using magnetic fillers in the form of balls as the working body (polygradient type) is extremely limited, especially for magnets with varying sphericity coefficients (mutual ratios of characteristic sizes). Experiments using cylindrical samples (porous) as a ferromagnetic matrix rendered the induction data subsequently applied to establish the magnetic permeability, susceptibility, and magnetization values for the samples at various values of the length-todiameter ratio of φ = 1–16. The demagnetizing factor N was obtained and analyzed for the «short» samples (1 ≤ φ [φ]) in the range of magnetizing field strengths of 9–47 kA/m, taking into account the established transient value of φ = [φ] = 10–12 (when, at φ ≥ [φ], the magnetic properties of the sample correspond to the magnetic properties of its quasi-solid material). The analysis results for these data, required when assessing the actual magnetic properties of «short» working bodies, characteristic of polygradient magnetic separators/ analyzers, demonstrate the validity of the exponential dependence (decreasing with increasing) of their demagnetizing factor. The research was carried out with the financial support of the Ministry of Education and Science of the Russian Federation within the framework of the State Assignment in the field of science (project No. 0706-2020-0024) and of the Russian Foundation for Basic Research and the Royal Society of London under research project No. 20-52-10006.

Prospects for the use of ferrites with high magnetic permeability and permittivity as radio-absorbing materials

The paper presents an overview of studies on the influence of the main parameters of ferrites on their ability to absorb electromagnetic radiation in the megahertz range (more than 10 dB). The main advantage of ferrites is a high refractive index (more than 1000) in the megahertz range due to the combination of high values of magnetic and dielectric permeability, which makes it possible to produce radio-absorbing coatings of small thickness (less than 10 mm) that effectively absorb electromagnetic radiation. Studies show that the attenuation of the power of electromagnetic radiation reflected from the surface of the ferrite is due to both interference processes and the processes of dissipation of electromagnetic energy during propagation in the ferrite. The inversely proportional relationship between the refractive index and the frequency of electromagnetic radiation in the megahertz range provides the condition for the interference minimum of the reflected radiation at a constant thickness of the ferrite coatings. A high refractive index slows down the speed of propagation of electromagnetic waves in ferrites, which enhances the processes of dissipation of their energy. The paper presents studies on the influence of the basic chemical composition of ferrites, alloying additives, microstructure parameters and technological modes on their magnetic and dielectric permeability. Studies have shown that an excess of iron oxide in excess of stoichiometry, which provides the semiconducting properties of ferrite grains, significantly increases the dielectric constant. High values of the dielectric constant of ferrites are provided by a combination of the dielectric properties of grain-boundary layers and the semiconducting properties of the grains themselves, which form the barrier capacity of grain boundaries according to the Okazaki mechanism. Alloying ferrites with oxides TiO 2 , Bi 2 O 3 , CaO in an amount of up to 1 wt.% allows increasing the electrical resistance and dielectric constant of grain-boundary layers, providing an increase in the dielectric constant of ferrite as a whole. It has been established that the formation of a dense coarse-grained structure provides an increase in both the magnetic permeability and permittivity.

Microwave Method for Measuring Electrical Properties of the Materials

The article is about the development of a new non-destructive microwave method for measuring the electrophysical properties of materials, based on the method of transmission and reflection of a plane monochromatic wave through layered materials. The method has been verified by the results of numerical and field experiments. A data processing technique is described for obtaining complex values of dielectric and magnetic permeability based on an original measurement scheme. Based on the results of mathematical calculations, the laboratory model was created using an ultra-wideband antenna and a parabolic mirror. The optimal distance of the antenna from the parabolic mirror for focusing the electromagnetic field has been determined based on the simulation. Testing was carried out in the frequency range 3–13 GHz on two samples of materials (plexiglass and textolite) with known electrophysical properties. The obtained results showed the reliability of the developed method and its applicability. The measurement error was less than 2%.

NVESTIGATION OF TRANSMISSION CHARACTERISTICS OF DISC CAPACITY CONVERTER IN THE MODE OF EXCITATION OF ULTRASOUND RELAY WAVES

A mathematical model of a capacitive ultrasonic transducer is designed allowing to emit ultrasonic vibrations into an electrically conductive product. The influence of a polarizing electrostatic field on the Coulomb forces formation in the surface layer of a metal sample is determined. A closed solution to the electrostatics problem is obtained for a piecewise homogeneous medium in which a half-space is filled with metal having finite values of electrical conductivity and magnetic permeability. An expression is obtained for calculating the surface density of a static electric charge on the metal sample surface. The main influencing factors that determine the spatial distribution of the charge density on the product surface, which will form the radiation pattern and power of the emitted ultrasound field, are defined. As part of the mathematical model of a capacitive sensor in the mode of converting electric energy to high-frequency mechanical (ultrasonic) energy in metals, closed solutions for electrostatics and electrodynamics problems are constructed in relation to a piecewise-homogeneous medium in which a half-space is filled with metal having finite values of electrical conductivity and magnetic permeability. It is determined that a capacitive disk transducer excites forces acting normally to the surface of electrically conductive products. A quantitative assessment of the surface density of the Coulomb forces is made. The main factors determining the sensitivity of a capacitive disk transducer are specified.