Tangential Magnetic Field Research Articles

Dynamic Magnonic Crystals for Measuring the Dispersion of Bulk Magnetostatic Spin Waves Caused by Magnetic Anisotropy in YIG Films

A dynamic magnonic crystal created by a surface acoustic wave that propagates in a GGG–YIG structure (gallium–gadolinium garnet–yttrium–iron garnet) is used to measure the dispersion of bulk magnetostatic waves due to the magnetic anisotropy in the YIG film. Such waves, which are called anisotropic-dipole magnetostatic waves (ADMSWs), can propagate together with surface spin waves in YIG films that are placed in a tangential magnetic field. It is shown experimentally that ADMSWs with a positive dispersion law occur in films that are grown by the liquid-phase epitaxy technique and not subjected to additional processing,. In the films that were subjected to additional processing the ADMSW dispersion law is negative when applying a piezoelectric zinc oxide film or bombarded with boron ions.

Electromagnetic Field Imaging in Arbitrary Scattering Environments

In this article, we propose a method to reconstruct the total electromagnetic field in an arbitrary two-dimensional scattering environment without any prior knowledge of the incident field or the permittivities of the scatterers. However, we assume that the region between the scatterers is homogeneous and that the approximate geometry describing the environment is known. Our approach uses field measurements and a compressive sensing inspired algorithm to estimate the incident field and the tangential electric and magnetic fields on the scatterers' surfaces. These estimates are then used to predict the field everywhere using Huygens' principle. Further, we identify the best measurement locations in the environment, which reduces the estimation error to approximately half of the error obtained when using random locations. We show that in an indoor scenario with up to four scattering objects, the total electric field is recovered with less than 10% error when the number of measurements is just 0.3 times the number of unknowns in which the problem is formulated. The formulated problem is solved using `Total field - Compressive sensing based subspace optimization method' - an algorithm that leverages the sparsity of the tangential fields in known transformation domains to obtain an optimal solution.

A new magnetic modeling method for magnetic levitation rotary table

Precision machining fields require the worktable to have a large-scale multi-degree-of-freedom motion capability. In order to provide a more accurate magnetic model for the control strategy decoupling process and the size parameter optimization design process of the maglev rotary table. This paper proposes a new magnetic modeling method based on the Two-Dimensional Harmonic method. Different from the existing harmonic method, this method simultaneously considers the tangential and radial magnetic field changes of circumferential magnetic array. And it eliminates the edge effect of the magnetic flux density distribution in the radial aperiodic direction. The magnetic force and torque are solved by the Lorenz integral formula and the Gaussian quadrature method. In order to verify the accuracy of the TDH method, the boundary element software RadiaTM is used for simulation, and a prototype is made for measurement. The experimental results shown that this method reduced the maximum error of the radial edge magnetic field from 104.19% to 3.29%. And it improved the calculation accuracy of magnetic force and torque by 60.74% and 84.39% respectively. This method does not rely on special example, and is beneficial to cross-platform applications. It is more suitable for realizing the magnetic modeling of the maglev rotary table with both rotational motion and large-stroke translational motion.

Effect of secondary electrons on SGEMP response

It is difficult to effectively shield the system generated electromagnetic pulse (SGEMP), which can significantly affect the performance of important electronic devices and infrastructure, such as low-orbit spacecraft. Numerical simulation is an essential way to study the SGEMP response. However, many previous studies ignored or simplified the effect of secondary electron emission in their models. In this paper, a three-dimensional electromagnetic particle-in-cell numerical simulation model is developed to evaluate the effect of secondary electrons on the SGEMP response of two typical structures (external SGEMP and cavity SGEMP, respectively) under different current densities (0.1–100 A/cm<sup>2</sup>) and different materials (Al, Cu and Au). A right cylinder or cylindrical cavity with a length of 100 mm is used. The photoelectrons produced by the interaction between the X-ray photon and metal are emitted from one end of the system and assumed to be monoenergetic. The photoelectron pulse follows a sine-squared distribution, and its full width at half maximum is 1 ns. Some important parameters of secondary electrons are discussed and summarized, including the emission coefficients of elastically and inelastically backscattered electrons, as well as the probability density functions of emission angles and energies. The results show that ignoring the secondary emission in the simulation model leads the peak electric field to be underestimated by twice-thrice, and the duration of electric field response by more than 10%. The oscillation frequency and the amplitude of the second peak of the tangential magnetic field are also increased, with the secondary electrons considered. Among various types of secondary electrons, backscattered electrons have a dominant effect on the change of SGEMP. The effect of true secondary electrons is about 1/5 of that of backscattered electrons. The effect of secondary electrons on SGEMP response increases with a higher atomic number of the material used in the system, mainly due to higher backscattering emission coefficient and a high ratio of high energy inelastically backscattered electrons. The secondary electrons will influence the response of the external SGEMP only when the space charge effect is strong (high X-ray fluence). While the response of the cavity SGEMP is more easily affected by the secondary electrons even at a relatively low X-ray fluence. This paper helps to better obtain the SGEMP response of a specific device under strong radiation through numerical simulation.

Analytical Calculation of Complex Relative Permeance Function and Magnetic Field in Slotted Permanent Magnet Synchronous Machines

In order to analyze accurately the airgap magnetic field of the slotted permanent magnet synchronous machine (PMSM) taking into account the influence of slotting effects, this article proposes an analytical method for calculating the complex relative permeance function. Based on one tooth pitch of the machine as the solution model, the governing Laplace field equation of the airgap region is solved analytically in the polar coordinate system. According to the boundary conditions between the slot and airgap region, the analytical expressions of the radial and tangential components of the complex relative permeance function are derived. With this complex permeance, the no-load radial and tangential airgap magnetic fields of the internal and external slotted PMSM with different slot/pole combinations are obtained. The accuracy of the analytical model is validated by the results of finite element analysis. With good simplicity and generality, this model can be an effective means for further study of motor performance.

Scattering and diffraction of a uniform complex-source beam by a slit in a perfectly conducting plane screen

Abstract. A new multipole solution in plane-polar coordinates for the scattering of an arbitrary TE- or TM-polarized incident field by an infinitely extended slit in a plane screen is derived. To this end a classical three-domain problem with a complete multipole expansion in each of the domains is formulated. The unknown multipole amplitudes are found from the continuity conditions of the tangential electric and magnetic field components. Finally an infinite system of linear equations is derived which can be approximated by a numerically tractable finite one leading to a solution with an arbitrary accuracy. The results are numerically successfully compared to those ones obtained by classically solving the strip problem using Mathieu functions and by a subsequent application of the rigorous form of the Babinet principle. Numerical results include the comparison of the scattered fields obtained for an incident uniform complex-source beam and for an incident plane wave.

Effects of Filling Material Roughness on Scattering from a Rectangular Groove

This study investigated the effects of filling material roughness on the H-polarized scattering signatures of a two-dimensional (2D) rectangular groove embedded on an infinite ground plane. Under the assumption of a weakly rough surface on the groove, simplifying suppositions can be used to estimate Green’s functions inside and outside the groove. Enforcing continuity in the tangential magnetic field on the rough surface enables the construction and resolution of a Fredholm’s integral equation with logarithmic singularity. The results were verified via two full-wave electromagnetic field simulations carried out using the finite element method and the method of moments. The findings showed that even a weakly rough surface, such as a polished exterior with weak residual roughness, can considerably affect and change 2D scattering patterns.

Calming the waves, not the storm: measuring the Kelvin–Helmholtz instability in a tangential magnetic field

Abstract

Identifying Interference From Multiple Noise Sources Using Only Magnetic Near Fields

As electronic products become increasingly more complicated, multiple noise sources are likely to simultaneously interfere with the radio frequency (RF) receiver. It will be very helpful if the dominant noise source can be identified when solving the RF interference issue in a complex system. This article proposes a method to separately calculate the contributions from multiple noise sources at their overlapped frequencies so that the worse noise source could be identified even when multiple sources radiate simultaneously. The proposed method creatively employs the decomposition method based on the reciprocity theory to calculate the interference contribution from different sources. Furthermore, in the interest of reducing the near-field scanning time and complexity, the magnetic field only scanning method is developed by using the finite-element method (FEM). In the proposed method, Huygens's surface is established for each source. The tangential magnetic near fields on each Huygens's surface were then applied to solve the corresponding tangential electric fields by the FEM. Subsequently, the sources are removed while the corresponding Huygens's surfaces are maintained. The victim structure is excited under these conditions to obtain the tangential magnetic fields on Huygens's surfaces, and a novel FEM procedure is applied to obtain the tangential electric fields. Finally, based on the electric and magnetic fields, the interference from each noise source can be separately estimated based on the reciprocity theory. This method is validated by a numerical example and measurement. This approach can assist engineers in identifying the contribution of coupling from different sources and in efficiently resolving electromagnetic interference issues.

In Search of an Interface between Warm and Hot Gas within the Local Bubble

Abstract We have examined UV spectra recorded by the Space Telescope Imaging Spectrograph on the Hubble Space Telescope for three stars, HD32309, 41 Ari, and η Tel, that are located well inside the boundary of the Local Hot Bubble in our search for absorption features of Si iv, C iv, and N v that could reveal the presence of an interface between the local warm (T ∼ 7000 K), neutral medium, and a more distant hot (T ∼ 106 K) interstellar medium. In all cases, we failed to detect such ions. Our most meaningful upper limit is that for log N(C iv) 11.86 toward HD32309, which is below the expectation for a sight line that penetrates either a conductive/evaporative interface or a turbulent mixing layer. We offer conjectures on the reasons for these negative results in terms of either a suppression of a conductive layer caused by the shielding of the local cloud by other clouds, which may make it more difficult for us to sense discrete absorption features from gases at intermediate temperatures, or by the presence of a tangential magnetic field at most locations on the surface of the local cloud.

A unified model to study the effects of elasticity, viscosity, and magnetic fields on linear Richtmyer–Meshkov instability

A unified analytical approach to study the effects of elasticity, viscosity, and magnetic fields on the Richtmyer–Meshkov (RM) instability by using the impulsively accelerated model is presented. This model clarifies the discontinuity in the oscillation periods and yields the asymptotic decaying rate in elastic solids. It reveals that the complex eigenvalues produce better results compared with the numerical simulations for RM instability in viscous fluids and resolves the standing controversy between the analytical theory and numerical simulations at a vacuum/fluid interface. At last, it easily retrieves the results when the normal or tangential magnetic field is present. Those good agreements, between numerical simulations and theoretical analysis, would enable the model to be valuable in more complex situations such as in the elastic–plastic slabs with or without the presence of magnetic fields, as well as in the nonlinear regime.

Quantitative evaluation of residual stress and surface hardness in deep drawn parts based on magnetic Barkhausen noise technology

In this study, the method of magnetic Barkhausenn noise (MBN) and tangential magnetic field (TMF) was employed for achieving simultaneous, quantitative prediction of residual stress and surface hardness in box-shape deep drawn parts of SPCC steel. Bi-directional MBN and TMF signals, profiles of surface hardness and residual stress were experimentally measured. Pearson correlation analysis results show that the averaged amplitude of MBN in one magnetization cycle and Root mean square of MBN signal demonstrates approximate linear dependency on residual stress (or surface hardness) in both the measured directions. Three-layer BP models are established after input nodes screening and optimization of neurons’ number in the middle hidden layer. BP models are marked corresponding to scanning or magnetization directions. For each direction, two independent models are established and they are combined to use for realizing high accuracy and simultaneous evaluation of the residual stress and surface hardness.

Magnetotelluric Soundings on a Stratified Earth with Two Transitional Layers

Theoretical magnetotelluric (MT) soundings are investigated for a stratified (five-layered) Earth model consisting of two transitional layers with conductivity varying linearly with depth, and three homogeneous layers with constant conductivity. The analytical expressions for the tangential electric and magnetic fields as well as the surface impedance are derived in terms of Airy functions. The effect of the thicknesses of the two transitional layers and the interlayer between them on the MT responses (apparent resistivity and impedance phase) is examined in detail.

Experimental Research of Induction Heating in Inner Hollow of Cylindrical Solenoid

Purpose. Experimental determination of the dependence of the magnetic field strength distributions and the density of induced currents in the metal of the tubular blank from its position in the cylindrical inductor internal hallow. Methodology. The electrodynamic problem solution using mathematical apparatus for analytical calculations. To describe the processes that arise in the material under processing, expressions for fields and currents flowing in non-magnetic metals under the action of a multi-turn cylindrical solenoid that derived from the system of Maxwell's equations. Accepted mathematical assumptions and simplifications do not affect the correctness of the results. Carrying out an experiment to determine the intensity of the magnetic field in the solenoid inner hollow and the induced currents density on the surface of the nonmagnetic blank. Results. The obtained experimental distributions of the magnetic field strength and induced currents with the full blank placement in the cylindrical inductor hollow correspond to the analytical relations derived earlier and coincide with the fundamental physical concepts of the processes taking place in the system. When the billet is partially placed in the inner hollow of the inductor, there is a sudden increase in the tangential magnetic field strength component. In this case, an extremum is observed in the end zone of the billet. This is explained by the concentration of induced currents in this region, as well as on the cylindrical surface of the billet. Originality. The average induction heating speeds correspond to the calculated values for the materials of the processed samples used in the experiment, which indicates the effectiveness of using this processing technology in equal measure, both non-magnetic metals and magnetic. The practical value of the results consists in the possibility of estimating the qualitative indices of the concentration of induced currents and heat release in the end part of nonmagnetic cylindrical preforms with their partial overlapping by an inductor to perform heating operations.

Experimental Research of Induction Heating in Inner Hollow of Cylindrical Solenoid

Purpose. Experimental determination of the dependence of the magnetic field strength distributions and the density of induced currents in the metal of the tubular blank from its position in the cylindrical inductor internal hallow. Methodology. The electrodynamic problem solution using mathematical apparatus for analytical calculations. To describe the processes that arise in the material under processing, expressions for fields and currents flowing in non-magnetic metals under the action of a multi-turn cylindrical solenoid that derived from the system of Maxwell's equations. Accepted mathematical assumptions and simplifications do not affect the correctness of the results. Carrying out an experiment to determine the intensity of the magnetic field in the solenoid inner hollow and the induced currents density on the surface of the nonmagnetic blank. Results. The obtained experimental distributions of the magnetic field strength and induced currents with the full blank placement in the cylindrical inductor hollow correspond to the analytical relations derived earlier and coincide with the fundamental physical concepts of the processes taking place in the system. When the billet is partially placed in the inner hollow of the inductor, there is a sudden increase in the tangential magnetic field strength component. In this case, an extremum is observed in the end zone of the billet. This is explained by the concentration of induced currents in this region, as well as on the cylindrical surface of the billet. Originality. The average induction heating speeds correspond to the calculated values for the materials of the processed samples used in the experiment, which indicates the effectiveness of using this processing technology in equal measure, both non-magnetic metals and magnetic. The practical value of the results consists in the possibility of estimating the qualitative indices of the concentration of induced currents and heat release in the end part of nonmagnetic cylindrical preforms with their partial overlapping by an inductor to perform heating operations.

A Mode-Matching Solution for TE-Backscattering from an Arbitrary 2D Rectangular Groove in a PEC

In this paper, the simple yet effective mode-matching technique is utilized to compute TE-backscattering from a 2D filled rectangular groove in an infinite perfect electric conductor (PEC). The tangential magnetic fields inside and outside of the groove are represented as the sums of infinite series of cosine harmonics (half-range Fourier cosine series). By applying the continuity of the tangential magnetic field, these modes are matched on the groove to obtain the series coefficients by solving a system of linear equations. For this purpose, some oscillatory logarithmic singular integrals involving Hankel and trigonometric functions are solved numerically, starting by removing the logarithmic singularity via integration by parts. In the following, the new well-behaved highly oscillatory integrals are computed using efficient methods, and several comparisons are made to demonstrate the validity and ability of the presented procedure.

Magnetic field effect on piezo-thermoelastic wave propagation in a half-space within dual-phase-lag

The current work is concerned with the study of wave propagation in a half-space of a piezo-thermoelastic material under a bias tangential magnetic field within dual-phase-lag (DPL). This is relevant to the design and performance of piezoelectric devices working under a bias magnetic field, for example, the DC magnetic field piezoelectric sensors widely used in various areas of technology. The characteristic time for the problem under consideration is in the range of picoseconds, which is comparable to the thermal relaxation times in many metals. Exact analytic expressions for the mechanical displacement, temperature, stress, electric potential, electric displacement, electric current and induced magnetic field are obtained using normal mode analysis. Plots are provided and discussed for rather large intensities of the magnetic field. Comparison is carried out between the results predicted by DPL and Lord–Shulman theory (LS) in the presence or absence of magnetic field. The presented results clearly indicate that the effect of magnetic field is more pronounced for LS than for DPL. It was found that for magnetic field intensities of $$10^7$$ Tesla, both theories give almost identical results. Beyond this threshold value, sensible deviations between the theories start to appear and grow with the intensity of the magnetic field. In connection with experimental measurements, the present investigation may help in calculating numerical values of different material parameters and in assessing the efficiency of the two considered theories.

Hybrid Model for Electromagnetic Vibration Synthesis of Electrical Machines Considering Tooth Modulation and Tangential Effects

With the development of vibration mechanism research on electrical machines, the tooth modulation effect was found recently. Besides, the tangential effect, which contains both the air-gap tangential force's effect and the influence of tangential magnetic field on the radial force, was also proved to be of great importance. Nevertheless, these effects are still not found to be considered in the analytical or hybrid vibration synthesis methods, which are quite efficient for machine vibration analysis. Hence, this article proposes a hybrid vibration synthesis method for electrical machines taking both these two effects into account to improve the accuracy. The electromagnetic force processing and transfer function construction processes of the proposed method are presented in detail. By applying this hybrid model to a permanent magnet machine and conducting an experimental study, the accuracy of this method is validated. Moreover, based on the proposed method, the influences of tooth modulation and tangential effects on the machine's vibration are analyzed. The result proves the significance of these two effects and highlights the contribution of this article.

STUDY ON THE CHARACTERISTICS OF MAGNETIC MEMORY SIGNALS AT FERROMAGNETIC MATERIAL DEFECTS

In order to study the effect of defects on the surface magnetic field of specimen, a series of stepwise loading tensile tests were carried out on 30Cr alloy steel. Defects were artificially prefabricated in advance on the surface of specimens. The magnetic field signal was collected by a TSC-1M-4 magnetic detector and the characteristics of magnetic field signals were studied. It shows that the tangential magnetic field is more sensitive to the local yield of specimen. The surface magnetic memory signal changes significantly at the edge of defects. Thus, it is an feasible method to evaluate the state of stress concentration by surface magnetic memory signal.

Magnetic effects on the solvability of 2D MHD boundary layer equations without resistivity in Sobolev spaces

In this paper, we are concerned with the magnetic effect on the Sobolev solvability of boundary layer equations for the 2D incompressible MHD system without resistivity. The MHD boundary layer is described by the Prandtl type equations derived from the incompressible viscous MHD system without resistivity under the no-slip boundary condition on the velocity. Assuming that the initial tangential magnetic field does not degenerate, a local-in-time well-posedness in Sobolev spaces is proved without the monotonicity condition on the velocity field. Moreover, we show that if the tangential magnetic field of shear layer is degenerate at one point, then the linearized MHD boundary layer system around the shear layer profile is ill-posed in the Gevrey function space provided that the initial velocity shear flow is non-degenerately critical at the same point.