Distribution of the induction of a quasi-stationary magnetic field created in a ferromagnet by an attachable electromagnet

Abstract

The magnetoelastic acoustic emission (MAE) method is a promising method for obtaining informa tion on the technical state of a ferromagnetic construction material [1][2][3][4][5][6]. This emission arises during the magnetization reversal of ferromagnets and is associated with the Barkhausen effect; in structural steels, the MAE is caused primarily by jumps of 90° domain walls [7][8][9][10][11][12].The implementation of the MAE method under actual operational conditions of ferromagnetic ele ments of structures provides the magnetization reversal of a certain volume of a diagnosed object. In this case, the locality and depth of the reversely magnetized region are very important. Therefore, calculating the spatiotemporal distribution of the induction of a quasi stationary magnetic field, which is created by an attachable electromagnet (AEM) in a ferromagnetic material, is an important problem. STATE OF INVESTIGATIONSSome results of experimental studies of the distribution of the induction of a stationary magnetic field that is created by an AEM in a ferromagnetic specimen are known from references [13][14][15]. Calculations that were based on the concept of an AEM-ferromagnetic specimen magnetic circuit were also carried out for a stationary case [16][17][18]. Theoretical approaches with consideration for Maxwell's equations ensure the calculation of the distribution of a stationary magnetic field, which is created by electromagnets of different configurations in a ferromagnetic system for several simple particular cases [19][20][21][22]. The results of numerical calculations of the induction of a stationary magnetic field that is created by a U shaped or solenoidal AEM in a ferromagnetic specimen are also known [23,24]. However, as was shown by the analysis of literature sources, data that contain the spatial and time distributions of the induction of a quasi stationary magnetic field that is created by an AEM in a ferromagnetic specimen are virtually absent [25].In our investigations, quasi stationary magnetic fields are considered because, in most cases, MAE is excited by using magnetization reversal frequencies ranging from fractions to units of hertz. Fields at such frequencies include the fields of electrotechnical devices that operate at commercial frequencies.In the quasi stationary electromagnetic approximation, the frequency of changes in the magnetiza tion reversing field is such that the delay effect (radiation effect) and displacement currents can be disre garded [25]. The predominant influence is exerted on electromagnetic processes by conduction currents, which also include eddy currents induced by an alternating magnetic field, in addition to currents from foreign forces that are induced by applied external stresses (as is observed in a stationary case). The value MAGNETIC METHODSAbstract-As a result of numerical calculations, the spatial and time distributions of the induction of a quasi stationary magnetic field, which was created in a studied ferromagnet by U shaped and sole noidal attachable elec...

The topography of the field and flux inside and above the surfaces of ferromagnetic plates during their contact and contactless magnetization

“…As was shown in [16][17][18][19], the spatial flux distribution predominantly depends on the shape and dimensions of the electromagnet. In particular, it was shown in [16,19] that a massive ferromagnetic object in the interpole space of a U shaped electromagnet is magnetized nonuniformly.…”

Magnetic flux distribution in a ferromagnetic material magnetized by U-shaped electromagnets of different geometric dimensions types

“…Theoretical calculations of the steadystate magnetic-flux distribution that are based on the system of Maxwell equations and the fundamental integral equation of magnetostatics have been performed only for some particular cases. Some works on the numerical modeling of flux and field distributions inside ferromagnets have been published recently [15][16][17][18]. In most experimental studies, methodological obstacles that are related to imperfection of measuring transducers impose certain restrictions on the shape of test products, and the shape, in its turn, affects the magnetic-flux distribution in these samples.…”