Relative Magnetic Permeability Research Articles

Study on the influence of high permeability magnetic iron on energy consumption reduction in high gradient magnetic separator

The green processing of weakly magnetic iron ore is inseparable from high-intensity and high-gradient magnetic separator (HGMS), which is one of the most energy-intensive magnetic separation equipment. Iron (Fe) armor serves as the key primary structure for enhancing magnetic field conduction efficiency within the magnetic system. The order of magnetic properties of commonly used magnetic yoke materials is: ordinary carbon structural steel < Q235 steel < DT4 electrical pure iron. But the utilization cost of DT4 electrical pure iron is the highest, especially the magnetic properties of DT4C super electrical pure iron are unstable and the yield is low. On the basis of ordinary pure iron materials, this article has developed a new type of 411 pure iron (411) upon controlling the levels of harmful elements, while increasing the concentration of beneficial elements.intensity Furthermore, through the utilization of magnetic field simulation software, the impact of 411 on the background magnetic field intensity of HGMS was analyzed. The results indicated that the newly developed 411 pure Fe exhibited a coercivity of 24.07 A/m, a saturation magnetization intensity of ∼ 1.69 T, a maximum relative magnetic permeability of 24.38 × 10-3H/m, demonstrating superior magnetic properties in comparison with Q235 and DT4C. When using 411 pure iron as the magnetic yoke material, the background magnetic field intensity of the HGMS can be increased by 6.85 % − 14.64 % compared with using DT4C super pure iron under the same excitation current conditions. The magnetic yoke with better magnetic conductivity will enhance the magnetic field utilization efficiency of the magnetic system, a reduce the excitation energy consumption, and improve the sorting performance of HGMS.

Monitoring of relative magnetic permeability variation during cyclic bending testing of austenitic steel grade 10Kh18n10t samples

Cyclic bending testing of austenitic chromium-nickel steel grade 10Kh18N10T samples was carried out. Evalution of relative magnetic permeability showed its noticeable increase when the samples became fractured. This increase is related to deformation martensite appearance. Additional experiment showed, that deformation martensite formation starts before the actual destruction of the sample.

Studies of Phase Transformation Kinetics in the System of Nanocrystalline Iron/Ammonia/Hydrogen at the Temperature of 350 °C by Means of Magnetic Permeability In Situ Measurement

The kinetics of phase transformations in the nitriding process α-Fe → γ’-Fe4N → ε-Fe3-2N of the pre-reduced iron ammonia synthesis catalyst was investigated under in situ conditions (atmospheric pressure, 350 °C) by measuring changes of mass, gas phase composition, and magnetic permeability in a differential tubular reactor. The iron nanocrystallite size distribution according to their specific active surface areas was measured, and it was found that the catalyst is bimodal as the sum of two Gaussian distributions, also differing in the value of the relative magnetic permeability. Relative magnetic permeability of small α-Fe crystals in relation to large crystals is higher by 0.02. In the area of α → γ’ transformation, the magnetic permeability dependencies change, proving the existence of two mechanisms of the α-Fe structure change in the α-Fe → γ’-Fe4N transformation. In the first area, a solution of α-Fe (N) is formed with a continuous and insignificant change of the crystal lattice parameters of the iron lattice. In the second area, there is a step, oscillatory change in the parameters of the iron crystal lattice in FexN (x = 0.15, 0.20, 0.25 mol/mol). In the range of γ’-Fe4N → ε-Fe3-2N transformation, a solution is formed, with nitrogen concentration varying from 0.25–0.45 mol/mol. During the final stage of the nitriding process, at a constant value of the relative magnetic permeability, only the concentration of nitrogen in the solution εr increases. The rate of the phenomenon studied is limited by a diffusion rate through the top layer of atoms on the surface of iron nanocrystallite. The estimated value of the nitrogen diffusion coefficient varied exponentially with the degree of nitriding. In the area of the solution, the diffusion coefficient is approximately constant and amounts to 5 nm2/s. In the area of oscillatory changes, the average diffusion coefficient changes in the range of 3–11 nm2/s, and is inversely proportional to the nitrogen content degree. The advantage of the research method proposed in this paper is the possibility of simultaneously recording, under reaction conditions, changes in the values of several process parameters necessary to describe the process. The research results obtained in this way can be used to develop such fields of knowledge as heterogeneous catalysis, materials engineering, sensorics, etc.

A Novel High Entropy FeCoNi(GaCu)1.0 Alloy with Attractive Soft Magnetic Properties.

The new FeCoNi(GaCu)1.0 alloy has interesting soft magnetic properties at room temperature compared to other high entropy magnetic alloys (HEMAs). It is a single-phase material with high saturation magnetization Ms = 114 Am2⋅kg-1, high relative magnetic permeability 1675, and low coercive field 320 A⋅m-1. In addition, it presents a TC = 591 °C. The spin wave stiffness is D = 85.21 meV Å2. This value is 3 times smaller than in pure Fe, thus exchange interaction among Fe, Co, and Ni atoms is smaller than those between Fe-Fe atoms, causing TC to decrease. The saturation magnetostriction λs is 5.7×10-6 and is as small as others λs values also found in other based FeCoNi HEMAs. Those small λs may be caused by the diffuse distortions of the lattice, a known effect on HEAs, which may be interfering in the magnetoelastic interaction between μ and the lattice.

On-load magnetic field calculation for linear permanent-magnet actuators using hybrid 2-D finite-element method and Maxwell–Fourier analysis

PurposeThe purpose of this study is to present a novel extended hybrid analytical method (HAM) that leverages a two-dimensional (2-D) coupling between the semi-analytical Maxwell–Fourier analysis and the finite element method (FEM) in Cartesian coordinates.Design/methodology/approachThe proposed model is applied to flat permanent-magnet linear electrical machines with rotor-dual. The magnetic field solution across the entire machine is established by coupling an exact analytical model (AM), designed for regions with relative magnetic permeability equal to unity, with a FEM in ferromagnetic regions. The coupling between AM and FEM occurs bidirectionally (x, y) along the edges separating teeth regions and their adjacent regions through applied boundary conditions.FindingsThe developed HAM yields accurate results concerning the magnetic flux density distribution, cogging force and induced voltage under various operating conditions, including magnetic or geometric parameters. A comparison with hybrid finite-difference and hybrid reluctance network methods demonstrates very satisfactory agreement with 2-D FEM.Originality/valueThe original contribution of this paper lies in establishing a direct coupling between the semi-analytical Maxwell–Fourier analysis and the FEM, particularly at the interface between adjacent regions with differing magnetic parameters.

Design and study of novel square electromagnetic sensing based on stepped eddy current thermography

Nondestructive testing of internal corrosion defects is a key task to evaluate whether the material is repaired and replaced. In this paper, a novel square ferrite magnetic open sensing structure is designed for detecting volumetric corrosion defects on the inner surface of oil and gas storage tanks. A theoretical model of the structure is developed and the characteristics of the guided distribution of the electromagnetic field are resolved. The proposed model provides a region of interest with a uniform magnetic field. This greatly improves the detectability and thermal comparison of corrosion defects on the inner surface. In addition, the inspection is performed under weak excitation conditions and in the full open field of view of the infrared camera. This configuration greatly improves the portability and efficiency of workpiece inspection. Several open architecture sensors are evaluated and compared regarding temperature rise uniformity, model passability, and lightweight level. Meanwhile, the geometrical parameters of the square sensor, the operating parameters, and the material properties of the detected samples are investigated, including the coil height, the cross-arm length, the lifting distance, the operating frequency, the relative magnetic permeability of the sample, and the electrical conductivity of the sample. Finally, the detection capability of the sensors was verified through experiments with different steel plate thicknesses and defect morphologies.

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.

Magnetic Characterization of MR Fluid by Means of Neural Networks

Magnetorheological and electrorheological fluids manifest a change in rheological behavior when subjected to a magnetic or electric field, respectively, such that they require electrical and magnetic characterization. In this paper, a simple and accurate mathematical model based on a small number of parameters provides the relative magnetic permeability of magnetorheological fluids as a function of the applied magnetic field. Furthermore, for the testing and magnetic characterization of magnetorheological fluids, a new metering equipment setup is implemented. Starting with the achieved experimental data, the mathematical relation μr=f(B) is represented by means of a radial basis function neural network, with neurons having a Gaussian activation function; by means of post-training pruning procedures, the trained neural network is applied using the proposed data. Therefore, the obtained mathematical relation μr=f(B) is in good agreement with the experimental data, with an approximate error of 8%.

Non-destructive evaluation of the steel fibre content and anisometry in thin UHPFRC elements

The tensile response of ultra-high performance fibre-reinforced composites (UHPFRC) is decisive in many applications and depends on the steel fibre content and orientation. These vary troughout the structural element and may differ from those in the laboratory specimens used to characterize the material behaviour. This work presents the developments on a non-destructive test method based on the measurement of the magnetic inductance, substantiating its use for the determination of the fibre content and orientation in thin UHPFRC elements and allowing the estimation of the directionally dependent post-cracking tensile strength of the material in the structure. Starting from a probabilistic description of the fibre orientation, an existing physical model of the magnetic circuit composed of a U-shaped inductor and the composite is generalized and is used to derive the relations between the magnetic inductance measurements, the fibre volumetric fraction and the fibre orientation factor. A second-order tensor approximation of the relative magnetic permeability of the composite is proposed to determine the in-plane fibre orientation factor along any direction based on any three non-collinear measurements. Experimental evidence is presented supporting the theoretical developments. The factors that may affect the measurements are experimentally quantified. The paper concludes with an application example.

High-performance Fe–6.5wt.%Si/CaCO3 soft magnetic composites prepared via the thermal decomposition of calcium acetate

Recent studies on inorganic salt compounds are predominantly directed towards their utilisation as reinforcements for resins. However, the use of salt compounds besides phosphates as insulating layers has not been widely explored. Therefore, this study focuses on using salt compounds as insulating layers for soft magnetic composites (SMCs), revealing their numerous potential advantages. Fe–6.5 wt%Si/(CH3COO)2Ca composite powders were successfully synthesised using a hydrothermal method. Then, SMCs powders of Fe–6.5 wt%Si/CaCO3 and Fe–6.5 wt%Si/CaO, along with their corresponding SMCs, were prepared using powder heat treatment and cold press moulding techniques. The effects of calcium acetate ((CH3COO)2Ca) addition on the structure and electromagnetic properties of Fe–6.5 wt%Si/CaCO3 SMCs were further explored via an in-depth investigation of the formation mechanism of CaCO3 and CaO insulating layers on the surface of the Fe–6.5 wt%Si matrix. Results showed that (CH3COO)2Ca, as a precursor, decomposed into CaCO3 at 300 °C and CaO at 900 °C during heat treatment. Compared with the CaCO3 insulating layer on the surface of the Fe–6.5 wt%Si matrix, the CaO insulating layer exhibited a tendency for flocculent agglomeration, with lower homogeneity and integrity. Furthermore, the addition of (CH3COO)2Ca considerably influenced the thickness of the CaCO3 insulating layer in the Fe–6.5 wt%Si/CaCO3 SMCs, thereby effectively modulating the magnetic properties of the materials. The prepared Fe–6.5 wt%Si/CaCO3 SMCs had optimal magnetic properties when 4 wt% (CH3COO)2Ca was added. Under the conditions of a 25 mT external magnetic field and 100 kHz frequency, the material exhibited a relative magnetic permeability as high as 37.2, a total loss of merely 125.06 kW/m³, a saturation magnetic induction intensity of 178.15 emu/g and an electrical resistivity of 125.4 Ω∙m. The innovative material design and the proposed preparation method considerably enhanced the comprehensive magnetic properties of Fe–6.5 wt%Si-based SMCs, opening up a new avenue for the research and development of high-frequency SMCs.

Effect of Annealing Temperature and Time on the Magnetic Properties and Magnetic Anisotropy of a Temper-Rolled, Semi-processed Non-oriented Electrical Steel

The effect of final annealing temperature and time on the core loss, magnetic permeability, and magnetic anisotropy of a temper-rolled, semi-processed 0.5 wt.% Si non-oriented electrical steel was investigated. The magnetic properties of the steel sheets at 50–400 Hz and 0.5–1.50 T were measured by the Epstein frame method on strips cut along both the rolling (RD) and transverse directions (TD). Optimal magnetic properties were obtained when the annealing temperature was at 800–825°C, and the annealing time was 2–4 h. Relatively large magnetic anisotropy between the RD and TD was observed in samples after recrystallization (~ 10% in core loss and ~ 70% in relative permeability), while deformed and non-recrystallized samples showed small anisotropy in magnetic properties. Regardless of the processing state of the steel, i.e., temper-rolled, recovered, or recrystallized, the core loss followed quadratic polynomial functions with respect to both the frequency and magnetic flux density, while the relative magnetic permeability followed cubic polynomial functions with respect to both the frequency and magnetic flux density. The microstructure and texture of selected samples were characterized by electron backscatter diffraction, which revealed the correlations between the magnetic properties of the steel and the microstructure and texture.

The Two-Domain Model Utilizing the Effective Pinning Energy for Modeling the Strain-Dependent Magnetic Permeability in Anisotropic Grain-Oriented Electrical Steels.

This paper presents a newly proposed domain wall energy-based model of the 2D strain dependence of relative magnetic permeability in highly grain-oriented anisotropic electrical steels. The model was verified utilizing grain-oriented M120-27s electrical steel sheet samples with magnetic characteristics measured by an automated experimental setup with a magnetic yoke. The model's parameters, identified in the differential evolution-based optimization process, enable a better understanding of the interaction between stress-induced anisotropy and magnetocrystalline anisotropy in electrical steels. Moreover, the consequences of the simplified description of grain-oriented magnetocrystalline anisotropy are clearly visible, which opens up the possibility for further research to improve this description.

Electromagnetic and microwave properties of single-layer thermoplastic natural rubber (TPNR)/yttrium iron garnet (Y3Fe5O12)/magnetite (Fe3O4) composites backed by a perfect conductor

The use of a single-layer material for microwave applications continues to attract many researchers due to materials’ homogeneity in an acceptable range of thickness. This study outlines the microwave electromagnetic characteristics and interpretation of results based on a single-layer material backed by a perfect conductor. Data from three different laboratory prepared thermoplastic natural rubber (TPNR)/yttrium iron garnet (Y3Fe5O12)/magnetite (Fe3O4) composites were presented. The microwave relative complex dielectric permittivity (ε r*) and magnetic permeability (µ r*) were measured using a microwave vector network analyser (MVNA) in the frequency range of 0.1846–10.0104 GHz. The specular material model backed by a perfect conductor was used to obtain the frequency-dependent reflection loss (R L) assuming a normal incident of electromagnetic (EM) wave. The real and imaginary components of ε r* (ε r′ and ε r″) and µ r* (µ r′ and µ r″) for the three samples show a similar trend of frequency dependent. TPNR/Y3Fe5O12 reflected the EM wave less when its thickness (t) equals a quarter of the propagating wavelength (λ m/4) inside the material. Interestingly, in the presence of Fe3O4, multiple minimal reflections occur at smaller thicknesses (e.g. t = λ m/32). For both cases, this is the condition where the reflected wave at the surface of the material is in a 180°-phase difference from the wave reflected earlier at the material-conductor interface. Destructive interference occurs when these two waves meet and is visualized as the dip on the reflection loss (R L) vs. frequency plot. The number of dips increases with thickness. The lowest frequency dip occurs at a lower frequency for a thicker material. For TPNR/Y3Fe5O12/Fe3O4 and TPNR/Fe3O4, as the material gets thicker, the high-frequency dips on the R L plot become smaller and the use of the material in microwave application is no longer practical due to the increase in its weight and a smaller reflection loss.

Determination of the Curie temperature of structural alloys by analyzing the electrical characteristics of wires

The Curie temperature for many structural multicomponent alloys can only be estimated approximately, for example, from state diagrams. The necessity of an operational assessment of this parameter arises in the design of technologies for processing and controlling structural materials, in mathematical modeling of physical processes. The paper describes an experimental method for determining the temperature of magnetic transformation by measuring the temperature dependences of inductance and electrical resistance of wire samples. Verification of the procedure was carried out by determining the Curie temperature of nickel and comparing it with data obtained by other methods. We established the dependence of the Curie temperature of nickel on the carbon content and determined the Curie temperatures for alloys of Fe-Cr and Fe-Ni systems. Using numerical modeling and experimental data, temperature dependences of the relative magnetic permeability of materials were obtained. The results show the presence of the Hopkinson effect in the materials under study and the presence of inflection points on the electrical resistance curves.

Computations and measurements of the magnetic polarizability tensor characterisation of highly conducting and magnetic objects

PurposeThe ability to characterise highly conducting objects, that may also be highly magnetic, by the complex symmetric rank–2 magnetic polarizability tensor (MPT) is important for metal detection applications including discriminating between threat and non-threat objects in security screening, identifying unexploded anti-personnel landmines and ordnance and identifying metals of high commercial value in scrap sorting. Many everyday non-threat items have both a large electrical conductivity and a magnetic behaviour, which, for sufficiently weak fields and the frequencies of interest, can be modelled by a high relative magnetic permeability. This paper aims to discuss the aforementioned idea.Design/methodology/approachThe numerical simulation of the MPT for everyday non-threat highly conducting magnetic objects over a broad range of frequencies is challenging due to the resulting thin skin depths. The authors address this by employing higher order edge finite element discretisations based on unstructured meshes of tetrahedral elements with the addition of thin layers of prismatic elements. Furthermore, computer aided design (CAD) geometrical models of the non-threat and threat object are often not available and, instead, the authors extract the geometrical features of an object from an imaging procedure.FindingsThe authors obtain accurate numerical MPT characterisations that are in close agreement with experimental measurements for realistic physical objects. The assessment of uncertainty shows the impact of geometrical and material parameter uncertainties on the computational results.Originality/valueThe authors present novel computations and measurements of MPT characterisations of realistic objects made of magnetic materials. A novel assessment of uncertainty in the numerical predictions of MPT characterisations for uncertain geometry and material parameters is included.

Eddy Current False Indications in Austenitic Steel and Titanium Alloys Heat Exchanger Tubes Activated by Stress

Eddy current non-destructive examination with the internal bobbin type probes is a mandatory test for heat exchanger tube manufacturing due to its high sensitivity to the different type discontinuities. In this paper, we want to highlight the problems related to the false indications in the nonmagnetic austenitic steel and titanium alloys due to magnetic inclusions. There are known origins for magnetic inclusions in stainless steel like chips or filings as a result of ferrous tool application, alloy depletion concerned with oxidation or corrosion, and magnetite deposits. The little-known origin of magnetic inclusions is concerned with stress induced martensitic transformation is shortly analyzed in this report as a possible mechanism for the creation of the magnetic inclusion in austenitic steel as in titanium alloy tubes. The phase transformation and as the result the presence of magnetic inclusions is generated by the activation of the spin magnetic moments of the free electrons under stress influence. These inclusions can radically influence the eddy current signal due to quite large difference in relative magnetic permeability but can be differentiated from real defects by re-inspection of the suspicious tubes at reduced operational frequency. During the eddy current examinations of stainless steel and titanium tubes by an internal probe, the false indications in tubes have been detected. The presence of these isolated indications is located always in the same length of the tested tube. The indications were detected in each tube and the signal amplitude was estimated in the range of 40-50% of the acceptance reference level. In stainless steels, the false indications generated are higher than in titanium alloys.

Calculation and analysis of the unbalanced magnetic thrust for the linear motor drive motion system

AbstractThe unbalanced magnetic thrust caused by the mover eccentricity for the linear motor drive motion system is analytically represented. Firstly, the relative complex magnetic permeability function is introduced to represent the effects of the mechanical installation errors and vibrations on the mover eccentricity. Then, the distortion of the magnetic field caused by the mover eccentricity is represented based on the Maxwell equation. The spectrum characteristics of the unbalanced magnetic thrust force is analytically calculated taking into account the harmonics in the drive circuit. Finally, the validity of the theoretically analysis is verified by the experiments. The results show that the static eccentricity caused by the mechanical installation error will produce the unbalanced magnetic thrust, affecting the thrust characteristics of the linear motor. In particular, the dynamic mover eccentricity caused by the mechanical vibration will produce paired unbalanced magnetic thrust harmonics on both sides of the original thrust harmonics, deteriorating the dynamic precision and efficiency of the direct drive motion system.

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.

The Effect of Heat Treatment on The Magnetic Properties of The (Fe-Mn) Alloys Prepared by Powder Metallurgy Method

This research studied the magnetic series of (Fe1-xMnx) which included the preparation alloys with weight ratios (X=25,50,70,80) by using Powder technology method . This study aimed to determine the Magnetic properties through the magnetic hestress loop . Number of magnetic properties have been found such as Remained force (Br), Coerecive force (Hc), Magnetic Relative permeability (µr) , and Magnetic Susceptibility (χm) for all study Samples . This experimental results were found a ferromagnetic behavior and sensitive to the heat treatment , which shows rapidity changeable to the paramagnetic behavior with the increasing the temperature degrees . The suitable heat treatment degree determined to get magnetic properties through the magnetic manufacturing operations . The results were explained due to the motion relation of magnetic spins with temperature degrees of heat treatment.

The effect of Cadmium Substitution on the structural and magnetic properties of Nickel Ferrite

Nickel – Cadmium ferrites having the chemical formula (Ni1-xCdxFe2O4), (0 ≤ X ≤ 0.5) were prepared by using powders technology method. The particle size of the ferrite samples were estimated from X-ray diffraction studies after the confirmation of the formation of single phase spinel structure of the ferrites. We found that the Lattice constant and density (ρx-ray) increased with Cd content while the porosity was noticed to decrease. Also the magnetic testing showed decreases in values the Coercive Force from (0.408 KA/m) to (0.384 KA/m) and the Remnant Magnetization from (0.056 Tesla) to ( 0.048 Tesla) and the Magnetic Relative permeability is the within range (0.137 ~ 0.125) with increasing of the Cadmium concentration while the Magnetic Susceptibility was noticed to increase from (0.862) to (0.875).