Action Of Electromagnetic Forces Research Articles

Magnetic controlled arc welding technology: a review

PurposeThe purpose of this study is to optimize and improve conventional welding using EMF assisted technology. Current industrial production has put forward higher requirements for welding technology, so the optimization and improvement of traditional welding methods become urgent needs.Design/methodology/approachExternal magnetic field assisted welding is an emerging technology in recent years, acting in a non-contact manner on the welding. The action of electromagnetic forces on the arc plasma leads to significant changes in the arc behavior, which affects the droplet transfer and molten pool formation and ultimately improve the weld seam formation and joint quality.FindingsIn this paper, different types of external magnetic fields are analyzed and summarized, which mainly include external transverse magnetic field, external longitudinal magnetic field and external cusp magnetic field. The research progress of welding behavior under the effect of external magnetic field is described, including the effect of external magnetic field on arc morphology, droplet transfer and weld seam formation law.Originality/valueHowever, due to the extremely complex physical processes under the action of the external magnetic field, the mechanism of physical fields such as heat, force and electromagnetism in the welding has not been thoroughly analyzed, in-depth theoretical and numerical studies become urgent.

Механическое взаимодействие метаемого тела со стенками канала рельсового электромагнитного ускорителя. Численное решение

The vibration of the accelerator rails under the action of electromagnetic forces, the right boundary of which is moving along with the armature along the barrel bore, is considered. The rail accelerator is simply considered as a Bernoulli-Euler beam of finite length, lying on a viscoelastic foundation, with cantilever support from the side of the accelerator breech. The rail vibration is described by a differential equation in partial derivatives of the fourth order in coordinate and the second order in time. The equation is solved numerically by combined method: finite differences in time and finite elements in coordinate. A comparison of the results of numerical calculations with an analytical solution showed that the developed code evaluates the behavior of the rail well under the influence of an EM load moving along its length along the entire trajectory of the accelerated body. Using the developed code, the influence of the current profile in the accelerator circuit and the foundation parameters on the dynamics of bending waves arising and propagating in the rail, the position and magnitude of the maximum rail deflection was studied. It is shown that it is possible to select a current profile that minimizes the rail accelerator deflection during acceleration. It is also found that the choice of the optimal current profile has no less effect on the maximum rail deflection than improving the parameters of the accelerator foundation. The calculation results may be useful in the design of an electromagnetic rail accelerator.

Механическое взаимодействие метаемого тела со стенками канала рельсового электромагнитного ускорителя. Тестовая задача

The vibration of the accelerator rails under the action of electromagnetic forces is considered. The armature and with it the right boundary of electromagnetic forces application moves along the barrel bore from the breach to muzzle. The rail accelerator is simply considered as a Bernoulli-Euler beam of finite length, lying on a viscoelastic foundation, with cantilever support from the side of the accelerator breech. The rail vibration is described by a differential equation in partial derivatives of the fourth order in coordinate and the second order in time. Using the eigenmode expansion method an analytical solution of the equation is obtained taking into account the change in the armature speed along the length of the barrel. Taking into account the peculiarities of the expression for natural vibration modes for this problem made it possible to simplify the calculations and take into account appropriate number of harmonics along the entire trajectory of the armature, which is difficult in the traditional application of the method, and thereby increase the accuracy of predicting the amplitude and nature of rail vibrations during the shot. The proposed approach allows testing and debugging numerical methods for solving complex problems, as well as more correctly designing the barrel of a rail accelerator.

Welding arc energy characteristic regulation

When welding pipes, due to the concentration of magnetic field lines in a ferromagnetic pipe with high magnetic permeability, the welding current magnetic field increases, magnetic blow, under. by the action of electromagnetic force, the arc length increases up to a break, the current and voltage on the arc fluctuate significantly, the seam dimensions change from a point to a large width, the process stability is disturbed, the welds formation and the welded joints impact toughness is reduced. Based on the study of the arc energy characteristics, according to which the voltage on the arc increases with increasing arc length, it was found that the arc moves along the tape end at a speed of 3.3 m/s, the electrode shape affects the welding arc. energy and voltage characteristics. In this case, the sum of near-electrode voltage drops depends on the work function of electrons from the cathode surface of the flux components and does not depend on the electrode shape, which confirms the main role of field emission in the arc and the arc concentration below. pinch-effect. To increase the welded joints impact toughness, it is necessary to reduce energy, heat input, crystal lattice microdistortions, microstresses, dislocation density, welding stresses, reduce the weld width, heat-affected zone, the deposited metal amount and refine the microstructure. An effective way to reduce energy is to increase the welding speed, which reduces the heat input, and reduce the arc length, arc voltage, which leads to an increase in the arc rotation speed, pinch effect, arc concentration and energy, heat input efficiency, reduce welding stresses, increase the crystallization rate, the microstructure refinement, the interatomic distance reduction and interatomic bonds increase. A process for one-sided high-speed welding of pipes for gas and oil pipelines with a low-energy composite electrode, which, due to low arc voltage, arc concentration, stability, energy reduction, heat input, welding stresses, microstructure refinement, interatomic distance reduction and interatomic bonds increase, provides an increase in the welded joints impact toughness 2-2.5 times has been developed. Minimum energy – maximum welded joints impact toughness

Multiphysics Numerical Simulation of the Transient Forming Mechanism of Magnetic Pulse Welding

Magnetic pulse welding (MPW) is widely used in the connection of dissimilar metals. The welding process involves the coupling of the electromagnetic field and structural field, which is a high-energy transient forming process. Based on the current experimental methods, it is difficult to capture the relevant data in the process of magnetic pulse welding, and the transient forming mechanism of magnetic pulse welding needs to be further studied. Taking the magnetic pulse welding of an Al-Mg sheet as an example, based on the Ansoft Maxwell and ANSYS finite element simulation platform, the loose coupling method was used to analyze an electromagnetic field generated by the discharging capacitor bank and structural field of the Al-Mg sheet under the action of electromagnetic force. The discharge period of the magnetic pulse welding capacitor bank was 62 μs. The current direction in the aluminum sheet changed once half a cycle, and the direction of the electromagnetic force was always consistent with the Z-axis. Under the skin effect, the magnetic induction intensity on the lower surface of the aluminum sheet was the largest. At 16 μs, the induced current, electromagnetic force and magnetic induction intensity in the aluminum sheet reached the peak values, which were 7.89 A/m2, 4.58 N/m3 and 12.6 T, respectively. The maximum electromagnetic force and velocity in the structural field were 2400 KN and 300 m/s. The structure field simulation reproduces the transient forming process of magnetic pulse welding, and clarifies the formation mechanism of the “intermediate zone rebound uncomposite zone-welding bonding zone-unbound zone”. Based on the numerical simulation technology, the research on the transient forming mechanism of magnetic pulse welding under multiphysics simulations can promote the development and application of magnetic pulse welding technology and better guide engineering practices.

Effects of Alternating Magnetic Field on the Hot Tearing Susceptibility and Microstructure of Al-5Cu Alloy

The influence of alternating magnetic field on hot tearing susceptibility (HTS) and microstructure of Al-5Cu alloy were studied using hot tearing test system and differential thermal analysis test. The Clyne-Davies model was used to evaluate the HTS of the alloy quantitatively under different magnetic current intensities (0A, 5A, 10A, 15A). The experimental results show that the HTS and microstructure of Al-5Cu alloy can be affected by imposing the alternating magnetic field during alloy solidification. In the range of 0–10A, with the increase of alternating magnetic field current intensity, there is strong forced convection in the molten metallic pool under the action of electromagnetic force, which leads to the fragmentation of dendrites and the grains refinement, optimizes the feeding channels between grains and reduces the HTS of the alloy. When the alternating magnetic field intensity is 15A, the grains become coarser due to the thermal effect of electromagnetic field, resulting in the deterioration of the feeding channel and the increase of HTS.

Structural design and seismic calculation of the magnetic field immunity testing system

The magnetic field immunity testing system is an important equipment for ITER (the International Thermonuclear Experimental Reactor), which is mainly used for electromagnetic compatibility test in strong magnetic field environment. Due to the large size of the system, the stability of the structure should be considered under the action of electromagnetic force and gravity. In this paper, the electromagnetic load distribution of the system under steady-state condition is analyzed by using the finite element method, and the force of each component in different directions is calculated. Then the reasonable fixed structure is designed to ensure the stable operation of the equipment, and the electromagnetic structure coupling analysis is used for the final fixed structure to study the electromagnetic force, gravity and bolt preload. Finally, the stress analysis of the equipment under the influence of seismic load is calculated. The results show that the system has enough seismic capacity.

Особенности применения теоремы вириала для магнитных систем с квазибессиловыми обмотками

The article shows that in a magnetic system with a thin-walled balanced winding close to a force-free one, a significant increase in the parameter θ=WM γ/M σМ , is possible, which, according to the virial theorem, characterizes the ratio of the energy of the magnetic system WM to the weight of equipment with a material density γ, where under the action of electromagnetic forces there appears a mechanical stress σМ. In a quasi-force-free magnetic system, the main part of the winding is in a state of local equilibrium, and only a relatively small part of the equipment is subject to stress. This part determines the weight of the entire system, and this weight can be minimized. The configurations of balanced thin-walled windings are developed, at the boundaries two boundary conditions are fulfilled simultaneously - the absence of the induction component normal to the boundary and the constancy of the product of induction and radius. The authors consider an example of a system consisting of a main part - a sequence of balanced "transverse" modules in the form of flat discs and end parts, consisting of a combination of "transverse" modules and "longitudinal" ones, having the form of rings elongated along the axis with balanced end parts. It is shown that in the system under consideration, the characteristic dimensionless parameter θ with an unlimited increase in the number of elements of the main part can reach a value of about 24, and when the number of these elements changes within 20 - 40, it changes from 6 to 9.

Features of the application of the virial theorem for magnetic systems with quasi-force-free windings

The article shows that in a magnetic system with a thin-walled balanced winding close to a force-free one, a significant increase in the parameter theta=W_Mγ/MsigmaM, is possible, which, according to the virial theorem, characterizes the ratio of the energy of the magnetic system WM to the weight of equipment with a material density γ, where under the action of electromagnetic forces there appears a mechanical stress sigmaM. In a quasi-force-free magnetic system, the main part of the winding is in a state of local equilibrium, and only a relatively small part of the equipment is subject to stress. This part determines the weight of the entire system, and this weight can be minimized. The configurations of balanced thin-walled windings are developed, at the boundaries two boundary conditions are fulfilled simultaneously --- the absence of the induction component normal to the boundary and the constancy of the product of induction and radius. The authors consider an example of a system consisting of a main part - a sequence of balanced "transverse" modules in the form of flat discs and end parts, consisting of a combination of "transverse" modules and "longitudinal" ones, having the form of rings elongated along the axis with balanced end parts. It is shown that in the system under consideration, the characteristic dimensionless parameter theta with an unlimited increase in the number of elements of the main part can reach a value of about 24, and when the number of these elements changes within 20 -40, it changes from 6 to 9. Keywords: Quasi-force-free magnetic field, field energy, mass of a magnetic system, virial theorem, minimization of the ratio of mass to energy.

The Electromagnetic and Structural Analysis of CFETR CSMC Double Current Lead

Before the formal fabrication of central solenoid coil for China Fusion Engineering Test Reactor (CFETR), the R&D of a prototypical coil namely the Central Solenoid Model Coil (CSMC) is performed to accumulate the design and fabrication experiences in the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP). As one of the most important auxiliary components, current lead plays the role of transmitting large current from power supply to CSMC winding packs. Of the total 8 sets of current lead, six of them are double current lead. Once CSMC is energized, large electromagnetic force is induced due to the interaction of current flowing in the current lead and back ground magnetic field. And the stress is generated subsequently under the action of electromagnetic force. If the maximum stress is beyond the material strength assessment threshold, the structural design of the double current lead must be redeployed. In order to check the feasibility of the current design of CSMC, the double current lead located in the high field region is selected and the electromagnetic calculation and electromagnetic-structural coupling analysis are carried out subsequently. In the end, the stress in evaluated based on analytical design. The study in the paper will provide reference for the following design optimization of double current lead.

Design and Fabrication of a Microfluidic Chip for Particle Size-Exclusion and Enrichment.

Based on the size of particles, a microfluidic chip integrating micro particles capture, controlled release and counting analysis was designed and fabricated in this paper. The chip is composed of a polydimethylsiloxane (PDMS) cover sheet and a PDMS substrate. The PDMS substrate is made of a sample inlet, microfluidic channels, a micropillar array, a three-dimensional (3D) focusing channel, and a sample outlet. The chip was fabricated by the multistep SU-8 lithography and PDMS molding method in this study. The micropillar array and channels in the chip can be molded in one step and can be replicated multiple times, which reduces the production cost and increases the practicability of the chip. Using a homemade electromagnetic drive device, the detection function of the chip was tested using a deionized water solution containing 22 μm polyethylene particles. The results showed that under the action of electromagnetic force, the chip enriched polyethylene particles; when the electromagnetic force disappeared, the enriched polyethylene particles were released by injecting buffer solution, and it was looked at as new sample solution. The flow rate of the sample solution and the sheath flow solution (deionized water) was injected into the three-dimensional focusing channel at a flow rate ratio of 1:4, and the polyethylene particles sample solution was focused, which could be used for the counting and analysis of polyethylene particles. The work of this paper can provide a reference for the subsequent detection of circulating tumor cells (CTCs).

Ascendancy of electromagnetic force and Hall currents on blood flow carrying Cu-Au NPs in a non-uniform endoscopic annulus having wall slip

This article aims to outline the characteristics of the blood flow conveying copper (Cu) and gold (Au) nanoparticles (NPs) through a non-uniform endoscopic annulus with wall slip under the action of electromagnetic force and Hall currents. The flow of blood with the suspension of hybrid nanoparticles in the annulus is induced by the peristaltic pumping. The governing equations are modeled and then simplified with the postulate of lubrication theory. The resulting non-dimensional momentum equation after simplification is solved analytically by employing the He's homotopy perturbation method (HPM) with the computational software Mathematica program (version 11). The influential role of emerging physical parameters on the physiological features related to the blood flow is inferred graphically and physically. The analytical outcomes reveal that Hall parameter has a diminishing behavior on the blood flow while the inverse impact is endured for mounting Hartmann number. Electromagnetic field and Hall currents offer a superlative mode for regulating blood flow at the time of surgery. An increment in the volume fraction of nanoparticles causes a drop in the blood temperature profile. The trapping phenomenon is also explored with the help of contours. An expansion in Hartmann number reduces the size of entrapped bolus and ultimately vanishes when Hartmann number is very large. This prospective model may be applicable in electromagnetic micro-pumps, medical simulation devices, heart-lung machine (HLM), drug carrying and drug transport systems, cancer diagnosis, tumor selective photothermal therapy, etc.

Microstructure formation and elevated temperature mechanical properties of directionally solidified Ti44Al6Nb1Cr alloy

To improve room and elevated temperature mechanical properties of high-Nb TiAl alloys, Ti44Al6Nb1Cr alloy has been prepared by cold crucible directional solidification (CCDS) technique under loaded power of 40 kW and pulling rate of 8.3 μm/s. Macro/micro-structure and phase composition have been characterized. Tensile properties have been tested at room and elevated temperature and the related mechanisms have been revealed. Results show that equiaxed grains change to columnar grains growing up along the axial direction of ingot after CCDS. Phase component is still composed of α2, γ and B2 phases. Microstructure consists of lamellar clusters and network structure. The lamellar clusters in a grain possess the same orientation. The content and size of B2 phases decrease and some casting defects with small size decrease as well due to sufficient diffusion of Nb and Cr atoms under action of electromagnetic force during CCDS. Tensile results indicate that comprehensive mechanical properties of Ti44Al6Nb1Cr alloy are improved significantly after CCDS. At room temperature, ultimate tensile strength and total strain are 523 MPa and 3.03%, respectively, which are improved by 18.1% and 64.7% compared with that of as-cast Ti44Al6Nb1Cr alloy (443 MPa and 1.84%). Moreover, fracture morphology also indicates that there are many deep ravines between cleavage steps and some similar dimples microstructure on cleavage steps. They are beneficial to improving comprehensive mechanical properties. At 973 K, ultimate tensile strength of Ti44Al6Nb1Cr alloy does not decrease at all, still reaching 530 MPa after CCDS. When service temperature rises to 1173 K, the strain is less than 4.28% showing excellent mechanical stability under tensile stress less than 436 MPa. The excellent stability for mechanical properties is due to thin lamellar phases, directional microstructure and large plastic deformation region.

Analysis of Dynamic Characteristics of Foreign Metal Objects under Electromagnetic Force in High-Power Wireless Power Transfer

Because of the noncontact structure of wireless power transfer (WPT) systems, foreign metal objects can easily enter into the coupling region—and often move under the action of electromagnetic force (EMF), instead of staying relatively static, which brings a difficult problem for foreign object detection technology. In this paper, we investigate the motion state of foreign metal objects with different properties under the action of electromagnetic force in the coupling space of WPT system. The equivalent model of the circuit parameters with the intervention of foreign metal objects and the differential equations for the motion of foreign metal objects are derived. Combined with finite-element simulation calculations, the motion characteristic of ferromagnetic and non-ferromagnetic metals under EMF was analyzed. The results show that, due to the size and properties of the metal, non-ferromagnetic foreign metal objects have four states: vibration, suspension, static and flying out. The ferromagnetic foreign metal objects will adsorb on the coil surface and rapidly heat up. By establishing an experimental prototype, the analysis uses high-speed acquisition equipment to obtain the movement of foreign metal objects which verified the correctness of the simulation. This research is also beneficial to the operational safety and reliability of the WPT.

Effect of Structural Parameters on the Startup Contact States in Revolving Armature

The revolving armature can effectively improve the firing accuracy of the railgun, which rotates at high speed under the action of electromagnetic force during the movement in the bore. However, the research on the influence of the armature structural parameters on the startup contact state between the armature and the rail is rarely involved. In this article, for a 15-mm caliber railgun, the finite-element calculation model of the revolving armature assembly process of interference is established, and the interference fit of the traditional revolving armature with different structural parameters such as crack length C_L and width C_w, interference amount $d_{1}$ , tail thickness $t$ , and length $L_{1}$ is calculated, and the influence law of the structural parameters of the rotating armature on the initial contact states–contact area, contact force, maximum equivalent stress, and plastic volume is obtained. Second, on the basis of the traditional revolving armature, an armature structure with interference at both ends leading edge and trailing edge is proposed, and the influence law of interference at the leading edge and the middle turning position on the contact ratio at both ends of the new armature is obtained. Finally, the startup contact states of the new armature, the traditional long-arm armature (tail length 18 mm), and the short-arm armature (tail length 14 mm) are compared. The results show that the new armature can significantly reduce the equivalent stress and plastic volume of the armature.

Droplet formation and motion characteristics in seven-wire rotating arc electrogas welding

This paper investigates the droplet formation and motion characteristics in seven-wire rotating arc electrogas welding. A high-speed video camera was used to observe the droplet formation and motion behaviors. The forces on the droplet in different welding parameters were analyzed to explain the droplet formation and motion processes. The results show that the small droplets at the end of six peripheral wires accumulate and grow toward the small droplet at the end of the center wire under the action of the electromagnetic force, and the coupled droplet forms under the action of electromagnetic force and surface tension at the end of the center wire. Gravity, plasma flow force, and rotating force affect the fall of the coupled droplet through the arc space and show non-axial motion and axial motion with different welding currents.

Влияние магнитного поля удлиненного соленоида на деформирование металлических кумулятивных струй

The inertial stretching of a metal shaped-charge jet in the magnetic field of a long solenoid is considered. The purpose of the magnetic field influence on the shaped-charge jet is to slow down the development of plastic instability of the jet with an increase in its ultimate elongation and penetration ability. Using a number of simplifying assumptions, an analytical description of electromagnetic processes in the jet section during its motion in the solenoid cavity and after exit from it is obtained. The induction heating of the jet section and the stress state in it under the action of electromagnetic forces are calculated in relation to the conditions of previous experiments with the influence of the magnetic field of solenoids on shaped-charge jets. The obtained results are used to substantiate the hypothesis about the possible cause of a large discrepancy in the experimental data of different authors on the increase in the penetrative action of shaped charges.

Expanding Control Range of Nonlinear Precision Tracking Systems with a Linear Electric Motor by Means of Adaptive Control

This paper considers the mathematical description of a servo drive system with a linear electric motor for the direct valve control system instead of the flapper–nozzle system. The description relies on the physical approach to determining electromagnetic parameters and electromechanical characteristics of electric motors. The obtained nonlinear traction characteristic and the resulting characteristic from the action of electromagnetic force and elasticity of the centering spring are used to determine the motor stroke limitations. The nonlinear action of counter-EMF against a rising electromagnetic time constant is substantiated. The solution proposed for the electrohydraulic tracking system is an adaptive control algorithm with an exomodel synthesized by the Lyapunov method that provides dissipativity of adaptation processes and expands the control range. The results of the practical tests of the adaptive control system are considered by the example of a servo system in the MATLAB/Simulink suite and on physical servo drive models.

Increasing efficiency of linear stepper electromagnetic engine

The rise and sustainable development of mining enterprises are inseparably linked with the search for and the introduction of progressive methods of intensification of operations and processes, among which pulsed or vibrational methods that allow one to concentrate and efficiently expend energy occupy a significant place. In the development of characteristic technologies, an important role belongs to power discrete drives with linear electromagnetic engines that allow one to abandon motion transducers and especially successfully compete with traditional electric engines in machines and installations where reciprocating movements of the working element along a linear trajectory are necessary. In this paper, we propose a new functional arrangement of a linear electromagnetic engine with a through axial channel and an integrated clamping mechanism and a calculation of the clamping force of the ball clamps in a stepped linear electromagnetic engine. Taking into account the required driving force of the working element, it is possible to calculate the necessary tractive force created by the armature during its working stroke under the action of electromagnetic force, and to select the corresponding linear electromagnetic engine for this actuator drive.

Investigation of vortex flows and electrical discharges forming under the action of external magnetic field in the system with liquid metal

Different kinds of vortices forming under the action of electromagnetic force are considered in the paper. The causes that lead to vortices generation and some attendant phenomena like appearance of electrical discharges are also discussed here.