Influence Of Longitudinal Magnetic Field Research Articles

Investigation of weld formation and porosity in 5052 aluminium alloy laser-GMA hybrid welding assisted by magnetic field with different orientations

Steady magnetic field with both orientations including longitudinal magnetic field (LMF) and transverse magnetic field (TMF) was used. The influence of LMF and TMF on weld formation, porosity and mechanical property of 5052 aluminium alloy laser-gas metal arc (GMA) hybrid welding was investigated. The shielding effect of hybrid plasmas on laser energy was weakened by TMF, leading to an increase in weld depth under TMF. Porosity rate was significantly reduced to 2.61% under TMF, because keyhole stability was improved, escaping channels for bubbles were increased, and solidification time of molten pool was prolonged. As a result, the highest tensile strength (174.7 MPa) of hybrid weld was obtained at TMF, owing to the lowest porosity rate.

Influence of longitudinal magnetic field on the Kelvin--Helmholz instability for two layers of ferrofluid at relative horizontal motion

Influence of longitudinal magnetic field on the Kelvin--Helmholz instability for two layers of ferrofluid at relative horizontal motion

Dynamical Spin Structure Factors of Anisotropic Spin Ladder in a Longitudinal Magnetic Field

We have addressed the magnetic excitations of quasi-one-dimensional two-leg anisotropic antiferromagnetic spin ladder under the influence of longitudinal magnetic field. Such excitations can be obtained via the study of frequency behavior of dynamical spin structure factors. The original spin model hamiltonian can be transformed to a hard core bosonic gas using a generalized bond operator formalism. We have used the linear response theory within Green’s function approach to obtain the frequency behavior of both longitudinal and transverse dynamical spin structure factor in the gapful regime. The results show energy gap vanishes at critical magnetic field which depends on anisotropic parameters. We have also found the longitudinal spin structure factor shows a sharp single peak at a particular frequency. The position of this peak moves to lower frequencies with increase of both intersite and local anisotropy parameters. However, the effect of intersite anisotropy on the position of peak in the longitudinal structure factor is more remarkable compared to another one. Also the change of magnetic field shows no considerable effect on the behavior of longitudinal spin structure factor. Furthermore, we have studied the dependence of the transverse structure factor on frequency for different magnetic field and anisotropy parameters. Unlike longitudinal case, two separate peaks appears in the transverse spin structure. The enhancement of magnetic field causes that the peaks in the transverse structure factor become far away from each other. Also, the influences of both anisotropies on the spin excitation spectrum of transverse spin components have been discussed.

Influence of Frequency and Induction of Longitudinal Magnetic Field on The Electrode Metal Loss and its Spattering During MAG-Welding

It is possible to increase the MAG-welding efficiency by controlling the electrode metal mass transfer at the reduction of discharge coefficient on spattering by influence of longitudinal magnetic field on the arc. The paper identifies a range of longitudinal magnetic field frequencies and induction which provide the discharge coefficient reduction of the electrode metal; it has also been found the characteristics of their mutual influence on electrode metal mass transfer process; mathematical models correlating the frequency and induction of longitudinal magnetic field length with loss coefficient of electrode metal on spattering are presented; technological recommendations, the implementation of which will allow to improve the efficiency of MAG-welding in industrial environments, are given.

The Influence of Longitudinal Magnetic Field on the CO2 Arc Shape**supported by National Natural Science Foundation of China (No. 51275314) and the Program of Science and Technology Foundation of Shenyang, China (F13-316-1-04)

The CO2 arc welding was carried out under a longitudinal magnetic field, and the arc shape has been studied by using a high-speed camera. From the camera images, we know that under the action of the longitudinal magnetic field, the upper end of the arc will constrict and the lower end of the arc will expand. It would become a bell-type shape and rotate at a high-speed in the optimum range of magnetic field parameters. The arc shape was simulated using a mathematical model, which was established based on experiment data and theoretical knowledge, and mechanism analysis has been carried out regarding the effect of longitudinal magnetic field on CO2 welding arcs.

Longitudinal magnetic field influence on depth of fusion in arc welding of butt joints

This paper investigates the influence of welding modes and longitudinal magnetic field on the butt joints, formation of welds of low carbon steel of 3...4 mm thickness. The influence of longitudinal magnetic field frequency on the depth of base metal penetration was studied. The investigations on welding joints of low carbon steel with4 mmthickness on the reverse polarity under the AN-348A flux were conducted. Welding of the fluxcopper lining of the C4 connection type was studied. It is shown that the depth of metal penetration increases with the increase of the longitudinal magnetic field frequency from 2 to 50 Hz. The values of the longitudinal magnetic field induction are 20...30 mT by 2...12 Hz frequency at magnetizing force of at least 2000 ampere-turns. The possibility of metal welding of3 mmthickness in a longitudinal magnetic field is shown. All these operations listed below are provided at longitudinal magnetic field with indicated parameters: formation of high-quality welds, complete penetration without burning-through metal, formation of the reverse bead which matches the requirements of GOST 8713-79 and absence of porosity in the welds. The research results can be applied to the welding of single-sided butt joints of 3...4 mm metal thickness.

Dynamics of multiple viscoelastic carbon nanotube based nanocomposites with axial magnetic field

Nanocomposites and magnetic field effects on nanostructures have received great attention in recent years. A large amount of research work was focused on developing the proper theoretical framework for describing many physical effects appearing in structures on nanoscale level. Great step in this direction was successful application of nonlocal continuum field theory of Eringen. In the present paper, the free transverse vibration analysis is carried out for the system composed of multiple single walled carbon nanotubes (MSWCNT) embedded in a polymer matrix and under the influence of an axial magnetic field. Equivalent nonlocal model of MSWCNT is adopted as viscoelastically coupled multi-nanobeam system (MNBS) under the influence of longitudinal magnetic field. Governing equations of motion are derived using the Newton second low and nonlocal Rayleigh beam theory, which take into account small-scale effects, the effect of nanobeam angular acceleration, internal damping and Maxwell relation. Explicit expressions for complex natural frequency are derived based on the method of separation of variables and trigonometric method for the “Clamped-Chain” system. In addition, an analytical method is proposed in order to obtain asymptotic damped natural frequency and the critical damping ratio, which are independent of boundary conditions and a number of nanobeams in MNBS. The validity of obtained results is confirmed by comparing the results obtained for complex frequencies via trigonometric method with the results obtained by using numerical methods. The influence of the longitudinal magnetic field on the free vibration response of viscoelastically coupled MNBS is discussed in detail. In addition, numerical results are presented to point out the effects of the nonlocal parameter, internal damping, and parameters of viscoelastic medium on complex natural frequencies of the system. The results demonstrate the efficiency of the suggested methodology to find the closed form solutions for the free vibration response of multiple nanostructure systems under the influence of magnetic field.

Magnetically affected single-walled carbon nanotubes as nanosensors

The influence of longitudinal magnetic fields on the nanomechanical sensing behavior of single-walled carbon nanotubes (SWCNTs) is of interest. To this end, a nonlocal mathematical model is proposed to study alteration of the fundamental flexural frequency of a magnetically affected SWCNT due to an arbitrarily added nanoparticle. The explicit expressions for the frequency shift of magnetically affected cantilevered and bridged SWCNTs due to the addition of a nanoparticle at the tip and midspan points are obtained. The predicted results reveal that the mechanical sensing of SWCNTs is generally enhanced by application of the longitudinal magnetic field.

The influence of longitudinal magnetic field on recombination radiation of low-pressure glow discharge in hydrogen and helium

We study the influence of longitudinal magnetic field on the radiation of low-pressure glow discharges in hydrogen and helium. We conducted experiments under a pressure in a discharge chamber of 10–20 Pa and a discharge current of 10–20 mA. A 0–1600 G magnetic field influenced only the cathode parts of the discharge, negative glow, and the dark Faraday space. The electron temperature and density were measured by the two-probe method as a function of magnetic field. We studied the dependence of the intensity of radiation in the spectral lines and continuous spectrum on magnetic field induction. We discovered that, under the action of magnetic field, discharge in hydrogen and helium is compressed and its glow volume increases by a factor of 20–25. In contrast, the radiation intensity in the lines and continuous spectrum increase by a factor of 100–200. We found a strong discrepancy in the measured intensity of the continuous spectrum into spectral ranges with calculation of electron-ion recombination.

Electron beam transport in the presence of a strong, axial magnetic field.

An analytical model is presented that describes the effects of an applied longitudinal magnetic field and energy loss on the transport of relativistic electrons in a medium. By using a modified Fermi equation we derive analytical solutions for the distribution function of electrons. The obtained results can be used to predict the influence of longitudinal magnetic fields on the lateral spread of electrons in both coordinate space and velocity space.

Influence of longitudinal magnetic field on current distribution and AC loss in twisted multifilamentary high Tc superconducting tapes

The AC longitudinal magnetic field that is parallel to the tape axis couples with the twisted filament bundle in multifilamentary high T c superconducting tapes to change their current distribution. The temporal evolution of the current distribution in the tape cross-section was calculated numerically to study the influence of the longitudinal magnetic field on AC loss characteristics. The change in the current distribution by the longitudinal magnetic field results in the increase in the AC loss. The AC loss due to the longitudinal magnetic field increases with decreasing twist pitch, while the AC loss due to the transverse magnetic field decreases with decreasing twist pitch. In practical conditions where high T c superconducting tapes carry their AC transport current in an AC external magnetic field with transverse and longitudinal components, the optimum twist pitch to reduce the total AC loss must be selected.

Influence of longitudinal magnetic field on thermomagnetic instabilities in a.c. superconducting cables

As the critical current of a single a.c. superconducting wire cannot be more than several tens of amperes, such single wires (strands) are bundled and twisted to make cables with a large current capacity. As the result of the twisting and bundling, a longitudinal magnetic field parallel to a strand axis is produced in the cables and windings by the transport current. It is shown theoretically and experimentally in this paper that the a.c. longitudinal magnetic field influences the current distribution in multifilamentary superconductors with an a.c. transport current and can induce thermomagnetic instabilities in them. A longitudinal magnetic field of the order of 10 −1 T is easily produced in these cables. It is shown that thermomagnetic instabilities induced by the longitudinal magnetic field in the cables cause a.c. quench current degradation in multiply-twisted a.c. superconducting cables. A way of twisting to decrease these instabilities is also proposed.

Prebreakdown Currents and Breakdown Potentials in Longitudinal Magnetic Fields

The influence of longitudinal magnetic field on breakdown potentials in dry air with plane parallel geometry has been investigated experimentally. The pressure range was from 0.364 to 0.5 torr and the range of the magnetic field was from 0 to 2050 G. It was found that the introduction of the magnetic field decreased the breakdown potentials at all the pressures studied. Prebreakdown currents were measured with and without the magnetic field. It was observed that the prebreakdown current changed significantly with the introduction of the magnetic field in the breakdown region.

439. The influence of longitudinal magnetic field on discharge with hollow cathode: R G Karimov and V M Klimkin, Izv VUZ Fiz, No 6, 1973, 154–155 ( in Russian).

439. The influence of longitudinal magnetic field on discharge with hollow cathode: R G Karimov and V M Klimkin, Izv VUZ Fiz, No 6, 1973, 154–155 ( in Russian).