Use Of Electromagnetic Force Research Articles

Prerequisites for the use of electromagnetic forces in technologies for refining aluminum alloys from nonmetallic inclusions

Prerequisites for the use of electromagnetic forces in technologies for refining aluminum alloys from nonmetallic inclusions

Effects of process configuration and sheet thickness on the deformation behaviour in multi-step electromagnetic forming of aluminium alloy sheet

Multi-step electromagnetic forming is a novel sheet metal forming approach which makes use of electromagnetic force acting on sheet metal incrementally to cause local deformation and further accumulate a final shape. The effects of process configurations including incremental interval and discharge voltage as well as sheet thickness on the radius of curvature and deformation height are investigated by conducting experiments on 2524-T3 aluminium alloy sheet. It is found that the deformation curvature of the workpiece increases with decreasing incremental interval initially, then tends to be saturated. In addition, the enhancement of the discharge voltage proves to be an efficient method for increasing the ultimate curvature and deformation height. However, the pit defect induced by the large discharge voltage has a significantly negative influence on the surface integrity of the fabricated part when discharge voltage exceeds a critical value of 7500 V. Furthermore, the deformation height decreases with increasing sheet thickness under the other same process parameters.

Probing Magnetic Pulse Welding of Thin-Walled Tubes

Magnetic pulse welding is a solid-state joining technology, based on the use of electromagnetic forces to deform and to weld workpieces. Since no external heat sources are used during the magnetic pulse welding process, it offers important advantages for the joining of dissimilar material combinations. Although magnetic pulse welding has emerged as a novel technique to join metallic tubes, the dimensional consistency of the joint assembly due to the strong impact of the flyer tube onto the target tube and the resulting plastic deformation is a major concern. Often, an internal support inside the target tube is considered as a solution to improve the stiffness of the joint assembly. A detailed investigation of magnetic pulse welding of Cu-DHP flyer tubes and 11SMnPb30 steel target tubes is performed, with and without an internal support inside the target tubes, and using a range of experimental conditions. The influence of the key process conditions on the evolution of the joint between the tubes with progress in time has been determined using experimental investigations and numerical modelling. As the process is extremely fast, real-time monitoring of the process conditions and evolution of important responses such as impact velocity and angle, and collision velocity, which determine the formation of a metallic bond, is impossible. Therefore, an integrated approach using a computational model using a finite-element method is developed to predict the progress of the impact of the flyer onto the target, the resulting flyer impact velocity and angle, the collision velocity between the flyer and the target, and the evolution of the welded joint, which are usually impossible to measure using experimental observations.

The Use of Electromagnetic Forces of the Earth in Manual and Physiotherapy

Physiotherapists usually ignore the electric polarization of human bodies that occurs under the influence of the electromagnetic forces of the Earth. This is irrational, since the positive or negative electrification of human tissues has the opposite effect on both their properties and functional activity. How physiotherapists must take into account the polarizing effect of the electromagnetic forces of the Earth when analysing the functional states of the tissues of the human body is shown here. It also shows how these electromagnetic forces can be used by manual and physiotherapists.

Method to Measure Electric Conductivity and Thermal Diffusivity Simultaneously by Use of Electromagnetic Force at High Temperatures

Method to Measure Electric Conductivity and Thermal Diffusivity Simultaneously by Use of Electromagnetic Force at High Temperatures

Device Design for Electric Arc Electromagnetic Constriction

Abstract: The difference of potential between two electrodes results in electric current breaking the dielectric barrier of the gas in this space causing a plasma discharge called electric arc. As a result, there is luminosity and an increase in temperature. Electric arc is used for welding and usually one of the electrodes is cylindrical with small diameter and the other with large area. Because of this configuration, the side section of the electric arc has a bell shape and forms a circular impression in contact with the work piece (the weld pool). With the use of electromagnetic forces, it is possible to change this circular impression, completely changing the behavior and consequently the geometry of the weld pool. This article presents the development and construction of a device for the electromagnetic constriction of the electric arc, capable of changing the cross section of the impression from circular to elliptical. The steps performed in the article were the simulation of the electromagnetic fields generated to change the electric arc shape, the development of the arc constriction device and the application of this electromagnetic constriction in beads on plate. The results show that the electromagnetic forces change the transverse profile of the arc from circular to elliptical, enabling the increase in specific power and a more precise orientation of the electric arc. Also, changing the orientation of the ellipse results in different penetration and width of the bead.

Cladding of aluminum alloy 6061-T6 to mild steel by an electromagnetic tube bulging process: finite element modeling

Bimetal tubes have useful applications in various industries where service conditions demand more different requirements in the tube core than its outside surface. The recent use of electromagnetic forces to deform or join metallic workpieces at high speeds has undergone rapid growth for materials processing. However, to date, no sufficient systematic understanding of the underlying principles of a subsequent high-speed electromagnetic tube bulging process to manufacture bimetal tubes has been gained. In this work, magnetic pulse cladding of Al/Fe clad bimetal tubes was analyzed by finite element modeling (FEM) using ANSYS software. The validity of FEM analyses was first confirmed by experiments in terms of the deformed shape. Second, the effect of cladding parameters (such as axial feeding being the dominant factor in the multi-step process) on the bulging and thinning behavior of the Al clad tube was presented in detail. Both the numerical simulation and experimental results show that no more than 70% of the bulging-coil length is an appropriate amount for the feeding length to prevent defects from being introduced by non-uniform deformation in the transition zone of the Al clad tube. The distributions of the magnetic flux line, magnetic force, and plastic strain in different cladding steps were then analyzed. It was concluded that during the multi-step cladding process, there was an uneven distribution of the magnetic field force along the transition zone. Consequently, inharmonious plastic deformation behavior occurs, which results in a limited acceleration of the transition zone to a certain impact velocity.

Contrôle électromagnétique des interfaces libres

In metallurgy, controlling shape and stability of an interface between a liquid metal and a covering fluid layers as well as possible mass transfers through this interface is needed. The use of electromagnetic forces which allows to operate without physical contact with the metal is a flexible and effective means of control. In this article, basic mechanisms of induction are introduced. Actions of magnetic fields on the behavior of liquid metals free surfaces are illustrated using experimental examples.

Active Control Method for Passing Through Critical Speeds of Rotating Superconducting Rotor by Changing Stiffness of the Supports With Use of Electromagnetic Force

This paper describes a method of supporting stiffness control of a rotating spherical superconducting rotor for passing through critical speeds. In this method, the vibration of the superconducting rotor due to rotation is controlled by changing the supporting stiffness. In the analysis, the exact solution of the rotation system controlled by this method is derived. Numerical calculations have been performed and experimental tests also carried out to verify the present control method and the theoretical results.

Finite Element Analysis of Electromagnetic Compression Forming of Steel Tubes

Electromagnetic Forming (EMF) is a non conventional metal working process that relies on the use of electromagnetic forces to deform metallic materials at high speeds. The electromagnetic compression forming simulations have been carried out on steel tubes of 76.2mm outer diameter and 2.3mm wall thickness using 9 turn helical actuator by varying energy levels using finite element analysis. In this paper, the experimental values of electromagnetic formed tubes available in literature [7] has been simulated using ANSYS and its results were studied for correlation. The results of simulation of the deformation shows good agreement with the values available experimental in the literature.

Electromagnetic forming process: estimation of magnetic pressure in tube expansion and numerical simulation

Electromagnetic forming (EMF) is a non conventional metal working process that relies on the use of electromagnetic forces to deform metallic workpieces at high speeds. This study is divided out into three parts. The first part presents a method for calculating the process parameters; namely the electromagnetic problem. An in-house code written in FORTRAN is developed for the electromagnetic tube expansion. In the second part, the results obtained from the in-house code are compared with those obtained from the free finite element magnetic software FEMM. In addition to this verification, the results of the in-house code are compared with the experimental ones available in the literature. The in-house code is then introduced in the finite element commercial code ABAQUS/ Explicit. The third part presents the simulation of the electromagnetic tube bulging forming process for metal tubes using ABAQUS/Explicit with an axi-symmetric model. The simulations have been carried out for Al 1050 aluminium tubes of 1.0mm thickness. This part also provides the comparison between the numerical simulations and the available experimental studies in the literature. Finite element simulations of the tube expansion predicted the experimental trends.

Development of Device to Evoke Stretch Reflexes by Use of Electromagnetic Force for the Rehabilitation of the Hemiplegic Upper Limb after Stroke

Development of Device to Evoke Stretch Reflexes by Use of Electromagnetic Force for the Rehabilitation of the Hemiplegic Upper Limb after Stroke

Electromagnetic force-assisted imprint technology for fabrication of submicron-structure

This paper reports a novel imprint technique for fabrication of polymeric submicron-scale structures. In use of electromagnetic force to press the magnetic stamp written with submicron-scale structures into a UV-curable resist on the substrate, the liquid photopolymer can be patterned at room temperature. In this study, an electromagnetic force assisted imprinting facility with UV exposure capacity has been designed, constructed and tested. Under the proper processing conditions, the polymeric submicron-scale structure with feature size of 500 nm across a 150 mm 2 area can be successfully fabricated. Scanning electron microscopy (SEM) and atomic force (AFM) observations confirm that the submicron-scale polymer structures are produced without defects or distortion and with good pattern fidelity over a large area. This technique shows the potential for efficient fabrication of submicron-scale structures at room temperature and low pressure on large substrates with high productivity at low cost.

Effects of electromagnetic force on melt flow and porosity prevention in pulsed laser keyhole welding

Porosity formation in pulsed laser keyhole welding was found to be affected by two competing factors: (1) the solidification rate of molten metal and (2) the back filling speed of molten metal during the keyhole collapse process. Porosity (pores/voids) was found in welds when the solidification rate of molten metal exceeds the back filling speed of molten metal. In this study, the use of electromagnetic force was proposed to control the back filling speed of molten metal, and a mathematical model was developed to investigate the effects of electromagnetic force on the transient melt flow, keyhole dynamics, and porosity formation. The results demonstrate that porosity in pulsed laser welding can be prevented by an applied electromagnetic force. Parametric studies to determine the desired strength of the electromagnetic force and its duration were also conducted to achieve quality welds.

Numerical simulation of the electromagnetic sheet metal bulging process

Electromagnetic forming (EMF) is an uncommon metal working process that relies on the use of electromagnetic forces to deform metallic workpieces at high speeds. It is expected to overcome some formability barriers of materials. EMF process analysis is the foundation of theoretical analysis. However, the electromagnetic sheet metal process is very difficult to describe, because of the complexity of magnetic pressure distribution. In this paper, a numerical modeling of the electromagnetic sheet metal process is performed using a finite element method, and a series of simulations on free bulging are carried out using the FEA program ADINA. The dynamic deformation process of sheet metal is investigated. At last, some experiments are made and those simulations agree well with the experimental results.

Refining of Si by the Solidification of Si-Al Melt with Electromagnetic Force

Aiming at the development of Si solidification refining process with Si-Al melt, investigations on separation method of Si grains solidified from Si-Al melt and the laboratory scale refining test were carried out. By the use of electromagnetic force under the fixed alternating magnetic field, solidified Si grains were successfully agglomerated in the Si-Al alloy and the high Si density part was obtained, although the use of gravity force was not effective. Furthermore, the refining test with induction heating revealed the high purification ability of this refining.

Application of electromagnetic forces to reduce tundish nozzle clogging

This paper considers the problem of oxide build-up within a tundish nozzle when casting aluminum killed steel. Water model studies have shown that the clogging problem may be very dependent on the flow pattern in the nozzle entry region. In particular, the studies show that the flow can separate within the entrance region of the nozzle, leading to the development of a stagnation zone that can trap oxide particles. This paper proposes that the stagnation zone can be substantially reduced, if not eliminated, through the use of electromagnetic forces. To generate the required electromagnetic force, two systems are considered. The first is based on injecting a DC current; the second by using electromagnetic induction. Both methods are described in this paper. Order of magnitude calculations are provided to illustrate that both methods are essentially feasible. The performance of each method in terms of modifying the turbulent flow characteristics in the nozzle entry region is then examined using a numerical model. It is shown that both methods can greatly reduce the recirculation zone. A cylindrical nozzle was chosen for the model studies since it represents a worst case situation. On the basis of the model studies, it can be concluded that whereas both of the proposed methods have the potential to reduce the troublesome recirculation zone, the induction method appears to be simpler in terms of practical implementation.

電磁力によるチャンネル内における２液層の混合と分離

電磁力によるチャンネル内における２液層の混合と分離

Microactuators with moving magnets for linear, torsional or multiaxial motion

Various types of actuators have been fabricated that make use of electromagnetic forces within micromachined silicon devices. An NdFeB permanent magnet is bonded to a movable silicon plate suspended by thin silicon beams. Planar coils are integrated monolithically on the chip to generate the driving magnetic field. Using a thick photoresist, gold lines with a thickness of 26 μm are electroplated. Different actuators for vertical, torsional and multiaxial motion have been investigated. Vertical and torsional deflections of the order of 100 μm and 10 degrees, respectively, have been obtained using a magnet with a typical dimension of 1 mm.

Fundamental Investigation of an Electromagnetic Degasser.

Fluidic devices for space experiments require an effective degasser to remove gas from gas-liquid two-phase flow. To meet this requirement, a new type of degasser has been developed. The degasser is composed of a vacuum chamber, magnets and a hydrophobic membrane, and removes gas through the use of electromagnetic force instead of gravitational forte: The ground experiment reveals the degassing performance, which indicates the possibility of gas removal under the micro-gravity conditions.