Papers by Keyword: Magnetic Field

Abstract: The paper considers the study of the electromagnetic force (EMF) of a synchronous generator based on the three-phase induction machine. The stand includes: a frequency converter, an induction motor, a synchronous generator, a three-phase rectifier, an active load resistance, power protection and inclusion industrial electrical network. The study provides an analytical solution to one of the main objectives within theoretical foundations of electrical engineering, formulated so to reflect the decision making while designing new types of synchronous generators with permanent magnets.

Abstract: An impact of a weak magnetic field on changes in the dislocation substructure of commercially pure copper exposed to stressing up to destruction under creep conditions was investigated. It was established that a magnetic field action on a metal exposed to creep resulted in the formation of a band dislocation substructure. In some cases grains with the dislocation chaos structure or cellular and grid substructures were revealed. In addition, quantitative differences in the dislocation substructure characteristics were also identified. A gradient nature of changes in the number of stress concentrators when moving away from the failure surface was defined. It was shown that the density of bend extinction contours characterizing the number of stress concentrators in the material decreased when moving away from the failure surface.

Abstract: The effect of magnetic fields on the swelling of liquid crystal elastomers (LCE) dissolved in liquid crystal (LC) solvent have been studied. The Flory-Huggins model used to calculate the free energy of an isotropic mixing and the Maier-Saupe model used to calculate the free energy of a nematic mixing. Numerical integration method used to calculate the orientational order parameter and the total free energy of system (consists of : nematic free energy, elastic free energy, isotropic mixing free energy and magnetic free energy) and the calculation results graphed as a function of temperatures for various magnetic fields and as function of magnetic fields for various of temperatures. We find that the magnetic field shifts the transition points towards higher temperatures, increases the energy transition, and induces an isotropic phase to paranematic phase.

Abstract: The constant magnetic field effect (B≤0.6 T) on creep of polycrystalline copper and its dislocation substructure has been established. The correlation of creep rate to time up to failure has been determined. The magnetic field effect on change of dislocation substructure parameters depending on the distance to the surface of failure (at a distance of 2, 4, 7, 10 and 20 mm from the surface of failure) under creep has been studied. It has been shown that magnetic field affects greatly the redistribution of dislocation substructure types and their scalar density of dislocations. The magnetic field effect on polycrystalline copper is connected with magneto-induction relaxation of dislocation structure.

Abstract: Recent research on grain boundary migration is reviewed. Novel in-situ measuring techniques based on orientation contrast imaging and the experimental results obtained on specially grown bicrystals are presented. Particularly, the investigated faceting and migration behavior of low angle grain boundaries under the curvature force in aluminum bicrystals was addressed. In contrast to the pure tilt boundaries, which remained straight/flat and immobile during annealing at elevated temperatures, mixed tilt-twist boundaries readily assumed a curved shape and steadily moved under the capillary force. Computational analysis revealed that this behavior is due to the inclinational anisotropy of grain boundary energy, which in turn depends on boundary geometry. The migration of planar grain boundaries induced by a magnetic field was measured in bismuth and zinc bicrystals. Various structurally different boundaries were investigated. The results revealed that grain boundary mobility essentially depends on the misorientation angle and the inclination of the boundary plane. Stress driven boundary migration in aluminium bicrystals was observed to be coupled to a tangential translation of the grains. The activation enthalpy of high angle boundary migration was found to vary non-monotonously with misorientation angle, whereas for low angle boundaries the migration activation enthalpy was virtually the same. The motion of the mixed tilt-twist boundaries under stress was observed to be accompanied by both the translation of adjacent grains parallel to the boundary plane and their rotation around the boundary plane normal.

Abstract: We consider a heavy, incompressible, homogenous, isothermal magnetic fluid between two coaxial cylinders in case of wetting. There is a current-carrying straight wire on the axis of these cylinders. The magnetic fluid is immersed in a non-magnetic liquid with the same density (the case of hydroimponderability). We apply the Langevin law to describe a magnetic fluid magnetization. Using the general analytical solution for any axially symmetric shape of the magnetic fluid free surface in any axisymmetric magnetic field, we investigate the break-up and the rebuilding of the magnetic fluid bridge in case of wetting.

Abstract: In the present work we report the investigation of heat exchange processes at stationary boiling regime of magnetic fluid on a horizontal surface under magnetic field H ≤ 4.2 kA/m. In the presence of uniform magnetic field the specific thermal flow arriving to boiling magnetic fluid increases by 1.5 - 2 times. We offer the mechanism of magnetic field influence on heat exchange intensity in boiling magnetic fluid. The volume, shape and contact area of steam bubbles in horizontal heating surface in magnetic field is studied. The equation, connecting a specific thermal flow, magnetic field gradient and magnetic fluid magnetization in bubble boiling regime of magnetic fluid is written.

Abstract: In this paper mathematical model is developed for the study of metal melt flows general regularities in non-uniform alternating magnetic field, in which cylindrical area filed with paramagnetic conducting melt is considered, the symmetry axis is directed vertically. The model include the equations describing spatial magnetic field distribution, the equations for induced currents, the equation of heat energy transfer that includes movement of media and volume heat sources, the equation of melt convection in Boussinesq’s approximation including of Lorentz force action to the melt. The boundary conditions for the melt velocities, magnetic fields and heat fluxes are described detail. The governing equations and boundary conditions are given in dimensionless form. The results of numerical experiments with different magnetic Reynolds number are given.

Abstract: In the present study, nonlinear free vibration behavior of nanobeam subjected to magnetic field is investigated based on Eringen's nonlocal elasticity and Euler–Bernoulli beam theory. The Hamilton's principle is adopted to derive the governing equations together with Euler–Bernoulli beam theory and the von-Kármán's nonlinear strain–displacement relationships. An approximate analytical solution is obtained for the nonlinear frequency of the nanobeam under magnetic field by using the Galerkin method and He's variational method. In the numerical results, the ratio of nonlinear frequency to linear frequency is presented. The effect of nonlocal parameter on the nonlinear frequency ratio is studied; furthermore, the effect of magnetic field on the nonlinear free vibration behavior of nanobeam is investigated.

Abstract: In this study the analysis of the magnetic field distribution of an electromagnet is presented. This electromagnet is used as an actuator in a semi-active vibration control of the three-layer beam with MR fluid. Two separate numerical methods are used for the purpose of calculating the magnetic field distribution. The first method is based on the Finite Element Method and implemented using ANSYS software. The second, simplified one is based on the assumption that the electromagnet can be substituted by a simple magnetic circuit divided into separate paths, with each sub-path defined by the value of reluctance of the corresponding electromagnet part. The comparison of the results from both methods with the ones obtained from an experiment is also presented and analyzed in the paper.