Effects Of Magnetic Flux Density Research Articles

EDM ASSISTED BY MAGNETIC FIELD FOR ARMOURED STEEL

The present paper presents a study on the performance of electrical discharge machining (EDM) assisted by magnetic field for armoured steel (HV500). Response surface methodology (RSM) has been utilized to model, analyze and determine the optimal parameters setting in the EDM process assisted by magnetic field. The process performance criteria such as; material removal rate (MRR), tool wear rate (TWR), were evaluated. Peak current, magnetic flux density, duty factor, and dielectric fluid pressure have been considered the main factors affecting EDM assisted by magnetic field performance. RSM was employed to develop the experimental models. The EDM process assisted by magnetic field process has proved its adequacy to machine armoured steel alloy under acceptable metal removal rate and minimum tool wear rate. The metal removal rate generally increases with the increase of the magnetic flux density and peak current value. The effect of duty factor was limited and dielectric fluid pressure has a moderate effect. Further, the minimum tool wear rate has been obtained at the parametric combination of higher magnetic flux density and higher duty factor when machined by EDM assisted by magnetic field with copper electrodes. It has also been clarified that the effect of magnetic flux density was limited on metal removal rate with graphite electrodes. It has also been found that the minimum tool wear rate was obtained at the parametric combination of higher magnetic flux density, higher peak current and lower duty factor, when machined by EDM assisted by magnetic field, with graphite electrodes.

Study of the tribological properties of rolling element bearings under the effect of magnetic field

Purpose The purpose of this study was to examine the effect of the magnetic field to the friction coefficient in the rolling element bearings which exists in electric motors. Design/methodology/approach To achieve this, the test rig was modified to adjust the density of the magnetic flux applied to the rolling ball element bearing. Experiments were carried out in the magnetic field from 0 to 7.5 mTesla at magnetic flux density range from 15, 40 and 65 N constant loads. Also, its rotary speed selected as 100, 200, 400, 800 to 1200 rpm, respectively. Findings In the majority of the experiments, it was observed that the magnetic field affected the friction coefficient. This influence reduced the friction coefficient in some experimental conditions and increased in some of them. Originality/value In the literature, there are very few studies on the effect of magnetic flux density to the friction coefficient in these rolling element bearings. It has become clear that more studies have been conducted on the effects of the magnetic field and/or electrical current on bearing damages and failures. This aspect is a study with specificity.

Ferrofluid droplet manipulation using an adjustable alternating magnetic field

Magnetically actuated droplet manipulation offers a promising tool for biomedical and engineering applications, such as drug delivery, biochemistry, sample handling in lab-on-chip devices and tissue engineering. In this study, characteristics of an adjustable alternating magnetic field generated by a magnetic coil for droplet manipulation was investigated which enables more control on droplet transport, and it can be considered as a suitable alternative for moving magnets or an array of micro-coils. By adjusting the magnetic flux density, the duty cycle and applied magnetic frequency, the manipulation of water-based ferrofluid droplets with a bio-compatible surfactant for different volumes was comprehensively examined. Also, the platform was able to manipulate the ferrofluid droplets completely immersed in oil. This solves the problem with droplet evaporation which has previously been reported for droplet manipulation on the surface. Furthermore, an analytical model is proposed for the movement of the ferrofluid droplet on the hydrophobic surface. The model predictions are in good agreement with experimental results. Also, the effects of magnetic flux density, duty cycle, frequency and the distance between the coils on the mixing process were studied. Results showed that the droplet movement on the hydrophobic surface was fully synchronized with the generated signal while the droplet moved backward in the oil after the magnetic field was turned off. By decreasing magnetic flux density, droplet volume, duty cycle, as well as increasing applied magnetic frequency, the step lengths become more uniform, the resolution of droplet displacement increases, but the average-velocity decreases.

Comment on the Paper “Effect of Magnetic Flux Density and Other Properties on Temperature and Velocity Distribution in Magnetohydrodynamic (MHD) Pump”

Comment on the Paper “Effect of Magnetic Flux Density and Other Properties on Temperature and Velocity Distribution in Magnetohydrodynamic (MHD) Pump”

Magnetic field assisted laser fabrication and electrical characterizations of metal dry Biolectrode with surface microstructures

Magnetic field assisted laser fabrication is proposed to process metal dry bioelectrode with surface microstructures. The effects of magnetic flux density on the geometrical dimension of surface microstructures of bioelectrode is investigated. The electrode-skin contact impedance is then studied using the two-electrode measurement method. Finally, electromyography (EMG) signal is recorded using bioelectrodes processed in different magnetic flux density. Our results show that the magnetic field has obvious influences on the height and bottom width of microstructure of bioelectrode. When a magnetic field of 100 mT is selected, larger height-width ratio of microstructures is obtained, which provides a stronger ability to penetrate stratum corneum. Consequently, much lower contact impedance is obtained. Signal-noise ratio (SNR) of EMG signal shows a correlation coefficient of 0.9836 with height-width ratio of microstructures on the surface of metal dry bioelectrodes. Raw EMG signals recorded by metal dry bioelectrodes in 100 mT magnetic field show a high SNR up to 27.350, which is slightly higher than that of traditional Ag/AgCl wet bioelectrodes (26.689). By stationary wavelet transform (SWT) de-noising, noise interfused in raw EMG signals is suppressed effectively. Moreover, the de-noised EMG signal recorded using metal dry bioelectrodes processed in 100 mT magnetic field still remains a fairly high SNR.

Performance Analysis of Heaving Float Wave Energy Converter with Liquid Metal MHD Generator

Heaving float wave energy converter/conversion (WEC), which makes use of liquid metal magnetohydrodynamics (LMMHD) generator, converts directly the linear motion of heaving float into electrical power. In this paper, effect of magnetic flux density on performance of heaving float LMMHD-WEC is analytically investigated. The results reveal that the capture width ratio, the load voltage, the output power, the system efficiency have maximum values with the increase of magnetic flux density.

Effect of Magnetic Flux Density on the Population of Salmonella Species in River Njoro Water

In this study, the experimental results of the concentration of Salmonella species in water exposed to magnetic flux density are presented. Water samples were collected from River Njoro, Nakuru County, Kenya. The initial Salmonella species counts for the samples were obtained using Membrane Filtration techniques. The samples were then exposed to different magnetic flux densities (2mT, 6mT and 10mT) at time intervals of 6 hours and 18 hours for each magnetic flux. Membrane filtration was also done after magnetic treatment of the samples. The data obtained was photographed and presented in tables and bar graphs. The maximum disinfection efficiency was 77 % for bacteria exposed to a magnetic flux of 10 mT for 6 hours. This study proved that magnetic field can be used as inhibitory factor against the Salmonella species.

Property-adjustable forming medium induced extension of sheet metal formability under variable magnetic field

Deformation states of sheet metals are determined by the in-plane stress distribution, which is closely related to forming load transmitted by forming medium. Mechanical properties of conventional forming medium, such as mineral oil, gas, and polyurethane, can hardly be controlled during the whole forming process. However, if the mechanical properties of forming medium can be freely altered, the stress state of sheet metal may become controllable. As a result, the magneto-rheological (MR) fluid was employed as a property-adjustable forming medium in this paper, which attempted to extend sheet formability in a controllable way. Effects of magnetic flux density (B) and iron particle content (φ) on yield stress of MR fluid in compression mode were analyzed at first. Magneto-rheological pressure bulging (MRPB) tests for Al1060-O sheet were conducted under different sets of parameters. Effects of B and φ on forming load were presented to show the adjustable mechanical properties of forming medium. Extended forming limit diagram (e-FLD) was proposed to describe the variation of sheet forming limit. The results indicate that sheet forming limit can be extended by monotonously increasing B in a certain range. The appropriate range of B is correlated to φ. The through-thickness shear stress caused by the transverse friction between MR fluid and sheet metal is considered to be responsible for this increase. The proposed process is demonstrated to be an efficient method to control the sheet formability, and more practical application may be expectable.

Free-surface flow of liquid oxygen under non-uniform magnetic field

The paramagnetic property of oxygen makes it possible to control the two-phase flow at cryogenic temperatures by non-uniform magnetic fields. The free-surface flow of vapor-liquid oxygen in a rectangular channel was numerically studied using the two-dimensional phase field method. The effects of magnetic flux density and inlet velocity on the interface deformation, flow pattern and pressure drop were systematically revealed. The liquid level near the high-magnetic channel center was lifted upward by the inhomogeneous magnetic field. The interface height difference increased almost linearly with the magnetic force. For all inlet velocities, pressure drop under 0.25 T was reduced by 7–9% due to the expanded local cross-sectional area, compared to that without magnetic field. This work demonstrates the effectiveness of employing non-uniform magnetic field to control the free-surface flow of liquid oxygen. This non-contact method may be used for promoting the interface renewal, reducing the flow resistance, and improving the flow uniformity in the cryogenic distillation column, which may provide a potential for enhancing the operating efficiency of cryogenic air separation.

Effects of Magnetic Flux Density on the Population of Escherichia coli in River Njoro Water

In this study, the experimental results of the concentration of Escherichia coli in water exposed to magnetic flux density are presented. Water samples were collected from River Njoro, Nakuru County, Kenya. The initial Escherichia coli (E.coli) counts for the samples were obtained using Membrane Filtration techniques. The samples were then exposed to different magnetic flux densities (2mT, 6mT and 10mT) at time intervals of 6 hours and 18 hours for each magnetic flux. Membrane filtration was also done after magnetic treatment of the samples. The data obtained was photographed and presented in tables and bar graphs. The maximum disinfection efficiency was 82.2% for bacteria exposed to a magnetic flux of 10 mT for 6 hours. This study proved that magnetic field can be used as inhibitory factor against the E.coli.

Aggregation process of paramagnetic particles in fluid in the magnetic field.

Magnetic targeting is a promising therapeutic strategy for localizing systemically delivered magnetic responsive drugs or cells to target tissue, but excessive aggregation of magnetic particles could result in vascular embolization. To analyze the reason for embolization, the attractive process of magnetic particles in magnetic field (MF) was studied in this paper by analyzing the form of the aggregated paramagnetic particles while the particle suspension flowed through a tube, which served as a model of blood vessels. The effects of magnetic flux density and fluid velocity on the formation of aggregated paramagnetic particles were investigated. The number of large aggregated clusters dramatically increased with increment in the magnetic flux density and decreased with increment in the fluid velocity. The analysis of accumulative process demonstrates the MF around initially attracted particles was focused, which induced the formation of clusters and increased the possibility of embolism. Bioelectromagnetics. 37:323-330, 2016. © 2016 Wiley Periodicals, Inc.

Effect of magnetic flux density on Sn crystallographic orientation in a solder joint system

Electromigration (EM) in Sn-based solder joints has recently been recognized as a reliability issue in high performance semiconductor devices for high end computing systems. EM in power modules is also of concern for the next generation hybrid electric vehicles. It is well known that the EM lifetime becomes significantly longer when the c axis of the Sn crystals is normal to the direction of electron flow. However, there has been no effective way to realize this alignment for the electronics industry. In the present study, the effect of external magnetic flux density on Sn crystallographic orientation was investigated at 0.5 and 1.3 T. The external magnetic field was applied to a solder joint at the solid–liquid coexistence period during solidification. The c axis of the Sn grains started to align normal to the external magnetic field direction at 0.5 T, and completed at 1.3 T.

Effects of magnetic fields on Fe-Si composite electrodeposition

Abstract Coatings containing Fe-Si particles were electrodeposited on 3.0wt% Si steel sheets under magnetic fields. The effects of magnetic flux density (MFD), electrode arrangement and current density on the surface morphology, the silicon content in the coatings and the cathode current efficiency were investigated. When a magnetic field was applied parallel to the current and when the MFD was less than 0.5 T, numerous needle-like structures appeared on the coating surface. With increasing MFD, the needle-like structures weakened and were transformed into dome-shaped structures. Meanwhile, compared to results obtained in the absence of a magnetic field, the silicon content in the coatings significantly increased as the MFD was increased for all of the samples obtained using a vertical electrode system. However, in the case of an aclinic electrode system, the silicon content decreased. Furthermore, the cathode current efficiency was considerably diminished when a magnetic field was applied. A possible mechanism for these phenomena was discussed.

Yield shear stress model of magnetorheological fluids based on exponential distribution

The magnetic chain model that considers the interaction between particles and the external magnetic field in a magnetorheological fluid has been widely accepted. Based on the chain model, a yield shear stress model of magnetorheological fluids was proposed by introducing the exponential distribution to describe the distribution of angles between the direction of magnetic field and the chain formed by magnetic particles. The main influencing factors were considered in the model, such as magnetic flux density, intensity of magnetic field, particle size, volume fraction of particles, the angle of magnetic chain, and so on. The effect of magnetic flux density on the yield shear stress was discussed. The yield stress of aqueous Fe3O4 magnetreological fluids with volume fraction of 7.6% and 16.2% were measured by a device designed by ourselves. The results indicate that the proposed model can be used for calculation of yield shear stress with acceptable errors.

Investigation of thermal behavior and fluid motion in DC magnetohydrodynamic pumps

Motivated by increasingly being used MHD micropumps for pumping biological and chemical specimens, this study presents a simplified MHD flow model based upon steady state, incompressible and fully developed laminar flow theory in rectangular channel to offer the characteristics of MHD pumps for prediction of pumping performance in MHD flow. The nonlinear governing equations of motion and energy including viscous and Joule dissipation are solved numerically for velocity and temperature distributions. To aim this goal a finite difference approximation based code is developed and utilized. In addition, the effects of magnetic flux density, applied electric current and channel size on flow velocity field as well as thermal behavior are investigated in various working medium with different physical properties. Also the entropy generation rate is discussed. The simulation results are in good agreement with experimental data from literature.

Effects of magnetic flux density and substrate bias voltage on Ni films prepared on a flexible substrate material using unbalanced magnetron sputtering assisted by inductively coupled plasma

The authors fabricated Ni films on a flexible substrate material using unbalanced magnetron sputtering assisted by inductively coupled plasma. The effects of magnetic flux density BC and substrate DC bias voltage VS on the Ni film structures were investigated. For VS = −40 V, the average surface grain size DG measured by atomic force microscopy for BC = 0, 3, and 5 mT was 88.2, 95.4, and 104.4 nm, respectively. In addition, DG increased with VS. From x-ray diffraction measurements, the (111) and (200) peaks were clearly visible for the fabricated Ni films. The ratio of the integrated intensities of I(111)/I(200) increased with VS. For VS = −40 V and BC = 3 mT, a film resistivity ρ of 8.96 × 10−6 Ω cm was observed, which is close to the Ni bulk value of 6.84 × 10−6 Ω cm. From these results, the authors determined that the structure of the fabricated Ni films on the flexible substrate material was affected by the values of BC and VS.

Research on Distribution of Magnetic Particles Based on Magnetic Field Control Grinding Wheel

In order to solve the problem of the randomly arrangement of the diamond abrasives, a novel orderly arrangement grinding wheel was developed, which used magnetic field to control the magnetic particles to drive diamond abrasives orderly arrangement. Effects of magnetic flux density on magnetic particle distribution was studied. And effects of magnetic particle proportion on magnetic particle distribution was studied. Grinding experiments were carried out on the tungsten carbide YG8 and surface roughness after grinding was also analyzed.

An investigation into magnetic electrolytic abrasive turning

The magnetic electrolytic abrasive turning (MEAT) process as a non-traditional machining is used to obtain surface finishing like mirror. MEAT provides one of the best alternatives for producing complex shapes with good finish in advanced materials used in aircraft and aerospace industries. The improvement of machining accuracy of MEAT continues to be a major challenge for modern industry. MEAT is a hybrid machining which combines two or more processes to remove material. The present research focuses on the development of precision electrochemical turning (ECT) under the effects of magnetic field and abrasives. The effect of magnetic flux density, electrochemical conditions and abrasive parameters on finishing efficiency and surface roughness are investigated. An empirical relationship is deduced.

A study on the magneto-assisted spiral polishing on the inner wall of the bore with magnetic hot melt adhesive particles (MHMA particles)

The spiral polishing mechanism employed a fast turning screw rod to drive the abrasive for workpiece surface polishing. In this study, the powerful ring magnet installed around the workpiece would attract the self-developed magnetic hot melt adhesive particles (MHMA particles) during the process of polishing, driving the SiC particles against the workpiece, the inner wall of the bore. At the same time, the flexibility of MHMA particles helped improve the surface quality of the bore by preventing the SiC particles from heavily scratching it. The effects of magnetic flux density, size and concentration of SiC particles, concentration of MHMA particles, viscosity of silicone oil, revolution speed of the spindle as well as machining time and machining gap on operation temperature, slurry viscosity, surface roughness, and material removal were discussed and the best parameter combination was identified based on the results of the experiment. The effects of each machining parameter on the finished surface topography of the workpiece were also examined. Both analysis of variance and F-test indicated that magnetic flux density and the concentration of MHMA particles were the two most important variables affecting the surface roughness. In other words, magnetic force helped improve spiral polishing. Furthermore, the results showed that adding new MHMA particles to the slurry greatly improved the surface quality, at a rate of 90 %, and reduced the workpiece surface roughness from 0.9 μm down to 0.094 μm.

Effects of magnetic flux density and substrate temperature on Ni films prepared by means of unbalanced magnetron sputtering assisted by inductively coupled plasma

We prepared Ni films on glass substrates by means of Unbalanced Magnetron Sputtering Assisted by Inductively Coupled Plasma (UM-ICP). The effects of the magnetic flux density BC and the substrate temperature TS on their structures were investigated. We found that the surface grain size observed with an atomic force microscope became large as BC and TS increase. We also found that the (111) plane measured by X-ray diffraction was preferentially orientated on the films under BC=5 mT at TS=60°C. These indicate that the energetic particle bombardment under BC and the increase of TS promote the surface diffusion on the Ni films. The ferromagnetic domain patterns observed with a magnetic force microscope showed the stripe domain structure having the domain width increasing with increasing TS and the fractal dimension of 1.88.