Effect Of Longitudinal Magnetic Field Research Articles

Optimization Methods for HTS DC and AC Cables With Longitudinal Magnetic Field Effect

Optimization Methods for HTS DC and AC Cables With Longitudinal Magnetic Field Effect

Исследование изменения геометрических параметров образцов, наплавленных методом GMAW при воздействии на электрическую дугу продольного магнитного поля

Introduction. The paper presents the results of research of additive manufacturing process by electric arc with axial feeding of steel filler wire in protective gas environment (GMAW technology) with additional influence of external longitudinal magnetic field on electric arc. Purpose of work: an experimental study of the effect of a longitudinal magnetic field during additive manufacturing by an electric arc with axial feed of filler wire made of structural steels in a protective gas environment on the change in the geometrical characteristics of the layers being surfaced. Research Methods. The manufacturing of specimens was carried out on a 5-axis additive machine based on a CNC machine. Surfacing was carried out in the following modes: voltage 17.5 V; current 55–65 A; wire diameter 1.2 mm; wire material Sv-08G2S; wire feed rate 2,267 mm/min; approximate roll diameter 3.0 mm; roll length 50 mm; number of wires per one roll 312.5 mm; number of layers when surfacing the wall 5; magnet operation mode: alternating current with frequency 50 Hz, voltage 30 V; measured magnetic induction 5.7 mTl; initial height of the magnet above the substrate 10 mm; electrode stickout 10 mm; shielding gas: welding mixture CO2-Ar; gas pressure (flow rate) 0.15 MPa. Results and discussion. The conducted experimental study showed that the effect of longitudinal magnetic field had a statistically significant effect on the change in the dimensions of the singular, namely an increase in the width of the layers being surfaced by 34.1 %, with a calculated significance index close to zero, and a decrease in height by 20.2 %, with a calculated significance index equal to 2.7105. The effect of longitudinal magnetic field had a statistically significant effect on the change of the overall dimensions of the specimens consisting of five layers, namely, the width of the specimens increased by 11.2 % with a calculated significance index of 4.3103, and the height of the specimens decreased by 10.3 % with a calculated significance index of 6.3105. The effect of longitudinal magnetic field had no statistically significant effect on the change of the vertical deviation from straightness for the side walls of the specimens, with a calculated significance index of 0.3277, and had no statistically significant effect on the change of the error of the width of the walls of the specimens, with a significance index of 0.098.

The effect of longitudinal static magnetic field on the radiation efficiency of high harmonics from overdense plasma

The effect of the magnetic field applied along the laser propagation direction on the radiation efficiency of high-order harmonics generated from laser-irradiated overdense plasma is investigated theoretically and numerically. We find that the external magnetic field can increase the transmittance of the overdense target, thereby dramatically enhancing the energy coupling between the laser and target. While for high-order harmonics of the laser reflected from the oscillating target, the radiation efficiency reaches the maximum when the cyclotron frequency of the electrons in the magnetized target approaches the laser frequency. This conclusion applies only to overdense plasmas targets. For targets with low reflectivity, the application of the magnetic field reduces the harmonic radiation efficiency due to the decrease of both the oscillating coherence and opacity of the target. This work provides a reasonable approach to improving the radiation efficiency of high-order harmonics and a method to estimate the magnitude of the self-generated magnetic field during intense laser–plasma interactions.

Effect of external longitudinal magnetic field on the dynamics of pulsed plasma stream

A spectroscopic study is carried out to investigate pulsed plasma stream produced in a coaxial plasma accelerator under the influence of an external longitudinal magnetic field. The dynamics of Argon plasma stream that includes the excitations and emissions of plasma species and its different parameter variations on the application of an external longitudinal magnetic field are reported in this work. The behavior of the ionized and neutral species of argon plasma is studied from their intensity distribution profiles which indicate the occurrence of faster recombination as compared to the field-free case. The variation of pressure reveals a significant influence on the recombination and diffusion process of the plasma species. Moreover, the variation of cathode voltage leads to variation in input energy to the system which influences the ionization and excitation processes of the plasma species. A plasma density (Ne) jump is achieved from 1021–1022 m−3 at a relatively higher pressure ∼8 bar plenum pressure in presence of the magnetic field. Saturation of the emissions and excitations of plasma species are revealed from the intensity profile and electron excitation temperature (Texc) profile which occur at different pressure and voltage both for field and field-free cases. The electron temperature (Te) is estimated using the FLYCHK code by comparing the simulated charge state distributions with the experimental findings. Using known parameters in the code, the different estimated Te shows a linear and an exponential decrement respectively in the absence and presence of the magnetic field. Maximum Te of 2.2 eV is reported which decreases to 1.51 eV at a significant increase of plasma density of 1022 m−3.

Effect of auxiliary longitudinal magnetic field on overlapping deposition of wire arc additive manufacturing

Effect of auxiliary longitudinal magnetic field on overlapping deposition of wire arc additive manufacturing

Effect of Longitudinal Magnetic Field on the Microstructure and Properties of A-TIG Welding with Different TiO2 Coating Amounts

In order to improve the poor weldability and low quality of welded joints during the welding of magnesium alloys, a longitudinal magnetic field is introduced in the welding process of A-TIG welding with a fixed magnetic field frequency (30 Hz) and magnetic field current (1.5 A). Experimental analysis is performed on the effect of the magnetic field on the microstructure and mechanical properties of welded joints under different TiO2 active agent coating amounts. The results show that the grain size tends to decrease and then increase with the increase in the active agent coating under the magnetic field. This is mainly because the active agent changes the arc morphology, which in turn affects the melt pool motion. The Lorentz force generated by the longitudinal magnetic field acts on the molten pool and will have an agitating effect on the pool. Both the magnetic field and the active agent are convective to the melt pool, and when the magnetic field and the active agent act together will further enhance the convective effect. However, when the active agent is too thick, it will affect the fluidity of the molten pool during welding and reduce the quality of the welded joint. Under the action of magnetic field, when the active agent coating amount is 3 mg/cm2, the grain size is the finest and the mechanical properties are the best. At this time, the tensile strength was 292 MPa, elongation was 11.2%, and hardness was 78.9 HV in the weld zone and 77.8 HV in the heat-affected zone. Further analysis of the melt pool change and grain refinement mechanism under the combined effect of the magnetic field and active agent revealed that the magnetic field promotes the solidification of the second phase in the weld tissue, but the effect on the heat-affected zone is not obvious. The addition of the magnetic field was found to refine the grains by EBSD testing, reducing the average grain size by 1.43 μm. This indicates that the introduction of the magnetic field in the A-TIG welding process improves the mechanical properties and microstructure of the welded joint, which is conducive to solving the problem of poor weldability in the welding process of magnesium alloys.

Effect of longitudinal magnetic fields on the grain growth of hollow stud welded joints

In this study, a drawing arc stud welding method combined with a longitudinal magnetic field was used for welding a 30CrNi3MoV low-alloy super strong steel substrate and Q235 hollow steel, and the effects of a longitudinal magnetic field on the microstructure growth process and mechanical properties of stud welds were studied. The results show that an arc controlled by a longitudinal magnetic field stirred the molten pool continuously, reducing the number of coarse proeutectoid ferrite, increasing the proportion of acicular ferrite, and smoothing the transition of alloyed elements near the weld joint fusion line within a certain range of excitation current. Under the action of the magnetic field, the weld grain size was refined from 4.30 μm to 3.14 μm, and the proportion of large-angle grain boundaries in the weld area increased from 24.27% to 34.2%. After the magnetic field application, the toughness of the welded joint was significantly improved. With an increase in the excitation current, the shear strength of the joint first increased and then decreased to 312 Mpa. Similarly, the impact toughness of the joint first increased and then decreased to 31.88 J·cm−2

Effect of longitudinal magnetic field annealing process on the properties and structures of soft magnetic Fe73.7Si15.3Cu1Nb3B7 nanocrystalline alloys

Effect of longitudinal magnetic field annealing process on the properties and structures of soft magnetic Fe73.7Si15.3Cu1Nb3B7 nanocrystalline alloys

Wave propagation analysis in viscoelastic Timoshenko nanobeams under surface and magnetic field effects based on nonlocal strain gradient theory

In this work, wave propagation in viscoelastic Timoshenko nanobeam under surface stress and magnetic field effects is studied. The governing equations of the non-local strain gradient theory are reformulated incorporating the Kelvin-Voigt visco-elastic constitutive model under the effect of surface stress and longitudinal magnetic field. The effect of longitudinal magnetic field on the behavior of single walled carbon nanotubes is modeled using the Lorentz magnetic forces. Gurtin-Murdoch’s surface elasticity is used to account for the surface stresses. The closed-form solutions are developed for the reformulated governing equations. The results obtained agree well with the existing literature in the limiting case of no surface and magnetic field effects. It is observed that with the introduction of surface stress values, the damping ratio of both flexural and shear waves increases. The effect of magnetic field, non-locality and strain gradient on phase velocity of flexural and shear waves, threshold and blocking diameters of carbon nanotubes is also presented.

Study of magnetization and specific heat of Heisenberg model on Lieb nanolattice: Anisotropic effects

We study the effects of longitudinal magnetic field and temperature on the thermodynamic properties of two dimensional Heisenberg antiferromagnet on the line-centered square lattice in the presence of anisotropic Dzyaloshinskii–Moriya interaction. We have studied the temperature dependence of specific heat and longitudinal magnetization of Lieb lattice for various physical parameters in the model Hamiltonian. Using a hard core bosonic representation, the behavior of thermodynamic properties has been studied by means of excitation spectrum of mapped bosonic gas. The effect of Dzyaloshinskii–Moriya interaction term on thermodynamic properties has also been studied via the bosonic model by exploiting Green’s function approach. Furthermore we have studied the magnetic field dependence of specific heat and magnetization for various Dzyaloshinskii–Moriya coupling strength. At low temperatures, the specific heat is found to be monotonically increasing with temperature for magnetic fields in the gapped field induced phase region. We have found the magnetic field dependence of specific heat shows a monotonic decreasing behavior for various magnetic fields due to increase of energy gap in the excitation spectrum. Also we have studied the dependence of magnetization on Dzyaloshinskii–Moriya interaction strength for different magnetic field values. • The study of thermodynamic properties of Lieb lattice in the context of Heisenberg model. • The study the temperature dependence of specific heat of Lieb lattice. • The study of magnetization with spin orbit coupling. • The study of specific heat of Lieb lattice.

The Feasibility Design Study and Cold Test of the First Model of HTS Cable With the Longitudinal Magnetic Field Effect

Since the 1970’s the effect of the increase of the critical current of superconductors in the longitudinal external magnetic field has been known. The critical current density of a Nb-Ti wire at low longitudinal magnetic fields demonstrated several times the larger value compared with that in a transverse magnetic field. The same phenomenon has been observed for 2G HTS tapes. It is natural to try to use this phenomenon to increase the critical current in DC HTS power cables. In this paper, we present the analysis of feasibility to use the longitudinal magnetic field effect to increase critical currents in practical HTS power cables. The experimental model of the HTS DC cable has been developed, produced, and tested in liquid nitrogen. The increase of the critical current observed when the longitudinal magnetic field generated. This increase coincides with the calculations.

A study of longitudinal magnetic field effect on critical buckling loads of SWCNT embedded in Kerr medium using nonlocal Euler-Bernoulli theory

A study of longitudinal magnetic field effect on critical buckling loads of SWCNT embedded in Kerr medium using nonlocal Euler-Bernoulli theory

Influence of longitudinal control magnetic field on efficiency of the arc process

Problematic. When surfacing and welding with the action of a longitudinal magnetic field (LMF), the productivity of melting of the electrode metal increases, it is possible to control the geometric dimensions of the cross-section of the surfaced beads and welds, the structure of the surfaced metal and welds is refined, the hardness increases, the strength and ductility of the weld metal increases, and the resistance of the welds hot cracking. 
 Research objective. Analyze the literature data on the effect of LMF on the efficiency of the arc surfacing process of worn-out surfaces of parts and structures, taking into account the magnetic properties of electrode wires and base metal to increase the efficiency of this process.
 Realization technique. Experiments were performed on submerged-arc surfacing with Sv-08A wire with a diameter of 5 mm with the action of an alternating LMF. Investigated the effect of the LMF frequency on the depth of penetration of the base metal and the width of the surfaced beads. 
 The results of research. It has been established that at frequencies of the LMF within the range f = 5...50 Hz, the penetration depth is less, and the width of the bead is greater than in surfacing without the action of the LMF. In the future, it is necessary to carry out studies on the effect of LMF during surfacing with flux-cored wires and strips on the metal structure of the surfaced beads and their service characteristics. 
 Conclusions. It has been established that for grinding the structural components of the metal surfaced with the action of LMF, it is necessary to ensure effective mixing of the liquid metal in the weld pool, that is, along its entire length. In this case, it is necessary to ensure the optimal parameters of the control magnetic fields. There is no theory that would explain the mechanism of refinement of the weld structure during arc surfacing with the action of LMF, and the existing views on this mechanism are contradictory. The data presented in the literature refer to the process of arc surfacing and welding with solid wire, there are no data on surfacing using flux-cored wires and strip electrodes.

Magnetic field induced rotation of the polarization plane of hydroxyl radical free induction decay in the terahertz region

Effect of the external longitudinal magnetic field on the optical free induction decay (FID) of the hydroxyl radical was investigated in detail. The experiments were performed on a rotational transition of OH (2Π3/2(J = 5/2) ← 2Π3/2(J = 3/2) at 83.8 cm−1) using the terahertz free electron laser. The rotation of the plane of polarization of FID as a function of time after the excitation of the radical was measured for various magnetic fields. The effect of nonmonotonic rotation of FID polarization plane in magnetic field was experimentally discovered. Numerical simulation of FID of the hydroxyl radical in a magnetic field has been carried out.

A non-local modeling for the influence of fluid forces on vibration characteristics of carbon nanotubes

This paper studies the effects of fluid forces and magnetic fields on the vibration characteristics of single-walled carbon nanotube (SWCNT). The force of the fluid on the SWCNT tube wall is derived by using the Hamilton’s variation principle, and the Lorentz magnetic force obtained from Maxwell's relationship. The governing equations of motion are based on the non-local beam model under the action of fluid and longitudinal magnetic field. Moreover, in the present investigation, an analytical approach is also proposed to study the effect of fluid, small-scale effect and longitudinal magnetic field on the vibration frequency of single-walled fluid-conveying carbon nanotube. The numerical results show that the fluid has a significant influence on the vibration characteristics of SWCNTs, and the effect of the high-speed fluid on the carbon nanotube (CNT) wall cannot be neglected.

Design and evaluation of 10-kA class superconducting DC power cable based on longitudinal magnetic field effect

In this study, we designed a power cable based on the longitudinal magnetic field (LMF) effect using an iterative approximation method. An evaluation of the cable shows that it is more efficient than conventional-design power cables. A cable with four inner layers and four shield layers and a maximum winding angle of 30° had a current capacity of more than 10 kA. Based on calculation results, we fabricated a 2-m-long LMF power cable and a conventional-design power cable. Experimental results show that the proposed power cable can carry more current (8.8% more current per tape and 18% more current overall) than a conventional-design power cable due to the LMF effect. These results well agree with the theoretical calculation results.

On the Effect of Longitudinal Magnetic Field on Electron Diffusion during Drift in Neon

On the Effect of Longitudinal Magnetic Field on Electron Diffusion during Drift in Neon

Effect of longitudinal magnetic field to the linear particle-beam track on yields of hydroxyl radical and hydrogen peroxide in water

Effect of longitudinal magnetic field to the linear particle-beam track on yields of hydroxyl radical and hydrogen peroxide in water

Effect of Longitudinal Magnetic Field on CMT Welding of Al-Alloy

A longitudinally varying magnetic field (MF) was applied during cold metal transfer (CMT) welding of Al alloys. The effect of MF on the welding process, macrostructure, microstructure and properties of weld beads was studied. The results showed that the application of MF led to arc expansion and rotation, the droplet transfer frequency decreased, the droplet volume became larger, and the droplets deflected. When the coil current was between 0 and 5 A, the weld beads porosity decreased from 4.47 to 0.26%. And when the coil current was increased to 8 A, the porosity of weld beads also increased to 2.84%. MF reduced the weld depth, wetting angle and weld reinforcement, and increased weld width. With the increase of coil current, the width of primary dendrite arms decreased from 7.75 to 5.01 μm. The area occupied by the Al–Si eutectic was enlarged, and the eutectic was refined. It was also found that the MF slightly increased the hardness of the weld beads, and the hardness distribution was more uniform.

Effects of probe ellipticity and longitudinal magnetic field on the polarization rotation in a coherently prepared atomic medium

The dependencies of the polarization rotation on the probe ellipticity and the longitudinal magnetic field have been studied both experimentally and theoretically in a V-type electromagnetically induced transparency for 87Rb vapour. The angle of rotation varies periodically with the change in the probe ellipticity and non-linearly with the variation of the magnetic field. We have observed that the plane of polarization is rotated maximum for linearly polarized light and have obtained angle of rotation 0.32° ± 0.01° for B = 0.036 ± 0.001 mT while it was 0.0267° ± 0.0002° without magnetic field. Thus our measurement becomes sensitive to the low magnetic field. A four-level system is considered and the corresponding density matrix equations have been solved analytically to explain these observations theoretically with the help of degenerate and non-degenerate magnetic sub-levels.