Magnetic compatibility of magnetic induction transducers with a moving object

Different technical solutions are proposed to solve the problem of magnetic compatibility of magnetic induction transducers with a moving object. The solutions are based on measuring the difference between magnetic induction vectors due to the object and the external magnetic field at selected points in space and by finding the Poisson parameters of the object at the transducer location. Translated from Izmeritel'naya Tekhnika, No. 9, pp. 44–46, September, 1997.     

Determining the angular position of a moving object

The angular position of a moving object may be determined from the measured vector for the acceleration due to gravity, the external magnetic field induction, and the magnetic induction from a source of alternating magnetic field. __________ Translated from Izmeritel’naya Tekhnika, No. 9, pp. 13–17, September, 2006.     

Remote determination of the position of an object in the coordinate system of a mobile platform

This article examines three variants of the solution of the problem of remotely determining the position of an object in the coordinate system of a mobile platform on the basis of projections of vectors of magnetic induction measured on the platform. The induction is created by transmitting antennas located on the object. There is no contact coupling between the platform and the object, and the solution eliminates the effect of the position error due to the nonorthogonality of the direction of the radiation and the direction of reception of the magnetic fields by the transmitting and receiving antennas. Translated from Izmeritel'naya Tekhnika, No. 3, pp. 25–30, March, 2000.     

Determining the coordinates and angular position of an object in the presence and absence of contact with it

This article discusses methods of determining the coordinates and angular position of an object in the presence and absence of contact with the object. The methods are based on measurement of the components of magnetic induction at chosen points in space and measurement of absolute values of magnetic flux density. The induction is created by sources that form a variable magnetic field. Translated from Izmeritel'naya Tekhnika, No. 2, pp. 30–34, February, 1998.     

Numerical Solution of the Problem of Limiting the Space for the Determination of the Coordinates and Angular Position of an Object

We consider the solution of the problem of limiting the space for the determination of the coordinates and the angular position of an object, using the magnetic induction vectors measured at three and four spatial points. The induction is produced by one and three transmitting antennas.     

Calculation of an electromagnetic field in a three-phase inductionpump with a compensating winding

A three-phase inductor which generates a magnetic traveling field is often used in induction liquid metal pumps. Due to the finite length of the inductor an alternating magnetic field component occurs, which should be compensated. An analysis of the electromagnetic field of an induction pump with a rectangularly shaped transport channel and a flat three-phase inductor possessing a compensating winding is presented. It is based on a computational model which takes into account the finite length and width of an inductor winding and nonuniform velocity distribution along the liquid metal depth. The calculations of magnetic flux density distributions in liquid zinc were carried out for an induction pump with and without compensating winding     

Simulation of the Magnetic Induction Vector of a Magnetic Core to be Used in FFC NMR Relaxometry

This paper is a contribution for the assessment and comparison of magnet properties based on magnetic field characteristics particularly concerning the magnetic induction uniformity in the air gaps. For this aim, a solver was developed and implemented to determine the magnetic field of a magnetic core to be used in Fast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) relaxometry. The electromagnetic field computation is based on a 2D finite-element method (FEM) using both the scalar and the vector potential formulation. Results for the magnetic field lines and the magnetic induction vector in the air gap are presented. The target magnetic induction is 0.2 T, which is a typical requirement of the FFC NMR technique, which can be achieved with a magnetic core based on permanent magnets or coils. In addition, this application requires high magnetic induction uniformity. To achieve this goal, a solution including superconducting pieces is analyzed. Results are compared with a different FEM program.     

The contact problem of a rigid stamp with friction on a functionally graded magneto-electro-elastic half-plane

We consider in this study the frictional sliding contact problem between a functionally graded magneto-electro-elastic material and a perfectly conducting rigid punch subjected to magneto-electro-mechanical loads. The problem is formulated under plane strain conditions. Using Fourier transform, the resulting plane magneto-electro-elasticity equations are converted analytically into three coupled singular integral equations in which the unknowns are the normal contact stress, the electric displacement and the magnetic induction. These integral equations are then solved numerically to obtain the distributions of the normal contact stress, electric displacement and magnetic induction at the surface of the graded medium. The main objective of this paper is to study the effect of the non-homogeneity parameter, the friction coefficient and the elastic, electric and magnetic coefficients on the surface contact pressure, electric displacement and magnetic induction distributions for the case of flat and circular punch profiles.     

A positive column of electric discharge in a transverse magnetic field

The influence of a transverse magnetic field on the characteristics of the positive column of electric discharge was investigated in both the diffusion and nondiffusion approximations. All solutions in the diffusion approximation were derived in analytical form. It is shown that with the enhancement of the magnetic field induction, the concentration distributions of the plasma and particle fluxes to insulated walls become nonsymmetric, the concentration maximum displaces in the direction of the magnetic force action, and the ion flux concurrent with this force may exceed substantially the ion flux in the opposite direction. The dependences of discharge parameters on the induction value are defined for helium. It is demonstrated that there is a maximum value of induction which bounds from above the range of magnetic fields, where the stationary state of the positive column is possible. In the range allowed for the stationary state, a single induction value is matched by two different modes of the positive column varying in values of the electron energy, drift speed, and electric-field strength. By means of the transverse magnetic field, it is possible to vary the electron energy within wide limits (from a few electronvolts to several hundred electronvolts).     

Determination of the Geomagnetic Field Induction from a Mobile Ferromagnetic Object

The solution of the problem of determining the induction of the geomagnetic field from a mobile ferromagnetic object by measuring the angular position of the object and the projections of the magnetic-induction vectors using two three-component magnetometric sensors is considered.     

Three-dimensional multiexcitation magnetoacoustic tomography with magnetic induction

Magnetoacoustic tomography with magnetic induction (MAT-MI) is a hybrid imaging modality proposed to image electrical conductivity contrast of biological tissue with high spatial resolution. This modality combines magnetic excitations with ultrasound detection through the Lorentz force based coupling mechanism. However, previous studies have shown that MAT-MI method with single type of magnetic excitation can only reconstruct the conductivity boundaries of a sample. In order to achieve more complete conductivity contrast reconstruction, we proposed a multiexcitation MAT-MI approach. In this approach, multiple magnetic excitations using different coil configurations are applied to the object sequentially and ultrasonic signals corresponding to each excitation are collected for conductivity image reconstruction. In this study, we validate the new multiexcitation MAT-MI method for three-dimensional (3D) conductivity imaging through both computer simulations and phantom experiments. 3D volume data are obtained by utilizing acoustic focusing and cylindrical scanning under each magnetic excitation. It is shown in our simulation and experiment results that with a common ultrasound probe that has limited bandwidth we are able to correctly reconstruct the 3D relative conductivity contrast of the imaging object. As compared to those conductivity boundary images generated by previous single-excitation MAT-MI, the new multiexcitation MAT-MI method provides more complete conductivity contrast reconstruction, and therefore, more valuable information in possible clinical and research applications.     

Explicit solutions of magnetoelastic fields in a soft ferromagnetic solid with curvilinear cracks

The problem of curvilinear cracks lying on a soft ferromagnetic solid subjected to a remote uniform magnetic induction is considered. With the complex variable technique, the general solutions of both the magnetic field quantities and the magnetoelastic stresses can be obtained. In order to illustrate the effect of magnetic induction, the solutions for the problem with one arc crack and two arc cracks are presented in a closed form. The stress intensity factors in the vicinity of crack tip and the crack opening condition are also derived. Considering the magnetic stress induced by an oblique magnetic field on the crack surface, one can find that the stress intensity factors of mode-I and mode-II are related to the incident angle of magnetic induction, the crack half angle and the magnetic susceptibility as displayed with figures. It is noticed that the present work is available even for a ferromagnetic material with low susceptibility. For the limiting case of the crack half angle in the one arc crack problem approaching to zero, the stress intensity factors are also provided and analytically compared with the existing ones of the straight crack problem.     

Improvement of magnetic induction-wire sawing process using a magnetic system

Magnetic induction-free abrasive wire sawing is a hybrid process that applies a homogeneous magnetic field to transport more abrasives into the sawing channel. This causes the performance of wire sawing significantly improved. Magnetic field strength is a key factor in determining the magnetic force acting on the magnetic abrasives, then affecting the quantity of abrasives adsorbed on the saw wire surface. However, the background magnetic induction strength produced by two permanent magnets is limited in this process. To further investigate the influence of magnetic field strength on the wire sawing performance, a magnetic system, which is based on the magnetic circuit design principle and the structure of single-wire sawing machine, is designed and fabricated. The magnetic field characteristics of the designed magnetic system are investigated both by numerical simulations and experiments. An experimental setup that installs the fabricated magnetic system on the single-wire sawing machine is built to conduct the magnetic induction-wire sawing experiments. The results show that the optimal magnetic induction strength is about B₀?=?135?mT. In this case, the kerf loss is decreased by 10% compared to the free abrasive wire sawing technology without a magnetic field.     

The sensitivity mechanisms of a bipolar magnetotransistor. Part 2

Investigations of a bipolar magnetotransistor have shown that its sensitivity is determined by a concentrationre-combination mechanism, depends on the magnetic induction, and increases in weak magnetic fields. When the base-emitter voltage bias is changed, the sign of the relative current sensitivity changes, and its maximum value, when measuring a magnetic field of induction 0.3 mT, amounts to 3300 T⁻¹. __________ Translated from Izmeritel’naya Tekhnika, No. 1, pp. 55–59, January, 2007.     

A study into statistical regularities of extinction of a DC electric arc in an axisymmetric magnetic field

A statistical investigation is performed of the extinction of a 30–350 A electric arc in a vacuum gap, in which permanent magnets are used to generate an axisymmetric magnetic field with different ratios between the radial and axial components of magnetic field induction. Dependences are given of the duration of stable arcing and limiting interruption currents on the magnetic field induction and on the size of contact gap.     

The sensitivity mechanisms of a bipolar magnetotransistor. Part 1

Investigations of a bipolar magnetotransistor have shown that its sensitivity is determined by a concentration-recombination mechanism, which depends on the magnetic induction, and it increases in weak magnetic fields. When the base-emitter bias voltage changes, the sign of the relative current sensitivity changes, and its maximum value when measuring a magnetic field of induction 0.3 mT amounts to 3300 T⁻¹. __________ Translated from Izmeritel’naya Tekhnika, No. 11, pp. 39–44, November, 2006.     

退火工艺对铁基非晶薄带磁感应效应的影响

研究了频率、磁场强度以及退火工艺对Fe73.5Cu1Nb3Si13.5B9非晶薄带磁感应效应变化幅度的影响.研究结果表明:磁感应效应变化幅度随着磁场强度的增大而增大,随着频率的升高呈现先增大后减小的趋势;与淬火态非晶薄带相比,退火可以提高磁感应效应变化幅度,且经300℃×1h退火后的磁感应效应变化幅度最大.     

An experimental investigation of liquid metal flow past a cylinder in longitudinal magnetic field

The distribution of pressure on the surface of a cylinder is obtained as a result of experimental investigation; this distribution significantly varies with increasing magnetic induction compared to the flow past a cylinder in the absence of magnetic field. In so doing, the pressure drag coefficient of the cylinder significantly increases. The measurements of velocity profiles reveal that the extent of the region of stagnant flow before the cylinder (the so-called “leading” wake) increases with magnetic induction. The dependence of axial defect of velocity on the MHD interaction parameter is obtained; this dependence under conditions of flow in a strong magnetic field is unaffected by the shape of the body subjected to flow, as is confirmed by the results of experiment involving the flow past a plate.     

A theoretical study of the impact of magnetic field of Hall current on the parameters of a high-current vacuum-arc discharge

It is demonstrated that the magnetic field of Hall current in a short high-current vacuum-arc discharge significantly distorts the external axial magnetic field and affects the distribution of current density in the discharge gap. This effect decreases with increasing external magnetic field, with decreasing arc current, and with decreasing ratio of the length of discharge gap to its transverse dimension. A 2D magnetohydrodynamic mathematical model is used to calculate the discharge parameters for different values of induction of external magnetic field. The calculation results are compared with similar results obtained using a 1.5D model in which the impact made by magnetic field of Hall current is ignored. It is inferred that the simpler 1.5D model may be employed in calculations of parameters of vacuum arc in a wide range of variation of arc current and of induction of external magnetic field.     

Effect of magnetostriction on fracture of a soft ferromagnetic medium with a crack-like flaw

The magnetic‐induction field in the vicinity of an elliptical inclusion embedded in an infinite soft ferromagnetic medium is determined based on complex potential theory. By using a constitutive relation of magnetostriction for isotropic materials, the stress field in the vicinity of an elliptical flaw is obtained. Furthermore, the stress field at the tip of a slender elliptical crack is determined for the case in which only an external magnetic field perpendicular to the major axis of the ellipse is applied at infinity. The results indicate that the stress field in the neighbourhood of the tip is governed by the magnetostriction and permeability of the soft ferromagnetic material. The induction magnetostrictive modulus is a key parameter in determining which of the two mechanisms, i.e., magnetostriction and magnetic‐force‐induced deformation, is dominant in determining the stress field in the neighbourhood of the tip of a crack‐like flaw. With regard to the influence of the magnetic field on the apparent toughness of a soft ferromagnetic body with a crack‐like flaw, soft ferromagnetic materials can be roughly divided into two categories: one possesses a large induction magnetostrictive modulus and the other has a small modulus. An approximate criterion for categorizing the materials is presented. For the benefit of engineering design, the expressions of the stress‐intensity factor for these two categories of soft ferromagnetic materials are presented. The results show that the stress‐intensity factor is affected not only by the flaw geometry, but also by the permeability of the medium inside the flaw.