Radial Magnetic Pressure Research Articles

Response of reactive species generation and biological inactivation to electromagnetically assisted cold plasma jets

External static electric and magnetic fields aligned parallel to the propagation direction of a plasma jet affect its dynamic characteristics and the response of reactive species present. A positive electric field was shown to enhance the intensity of ionization waves and the number of positive ions, thereby promoting the generation of aqueous OH and the inactivation of tumor cells subjected to the plasma jet. Correspondingly, the concentration of aqueous O2− and sterilization by the plasma jet gradually increase with increasing negative electric field intensity. The application of an external magnetic field induces a deformation of the plasma plume, manifesting specifically as a radial contraction/expansion of the plasma plume inside/outside the quartz tube because of the influence of magnetic pressure. In addition, with the external magnetic field, the generation of reactive species and the biological inactivation within the plasma jet are improved and can be attributed to the enhanced discharge arising mainly from electrons confined by the axial magnetic field and the radial magnetic pressure. Our work shows that external magnetic fields are well suited to improving the energy efficiency with regard to plasma jet applications, whereas external electric fields provide a means to manipulate the flux and composition of reactive species over the substrate downstream.

External axial magnetic field enhances discharge and water treatment of cold plasma jets

In this Letter, the effect of an external axial magnetic field on the propagation characteristics of a helium plasma jet and plasma-activated water was investigated. Stacked magnets surrounding the quartz tube significantly enhance the brightness and length of the ionization wave. The discharge enhancement is more pronounced at a position farther along the tube axis than near the jet nozzle. Under the action of the external magnetic field, the concentrations of aqueous reactive oxygen species, including H2O2, OH, and O2−, significantly increase with the increasing electron density, whereas the vitality of melanoma cells effectively drops. A magnetic fluid model suggests that the discharge enhancement arises mainly from the confinement of the radial motion of electrons imposed by the axial magnetic field and the radial magnetic pressure, suggesting that the external magnetic field may be beneficial in improving the effects of plasma jet applications.

Effect of coil length and relative position on electromagnetic tube bulging

A loose coupling method is adopted to study electromagnetic tube bulging, and effect of processing parameters on electromagnetic tube bulging is analyzed. The results show that critical relative length increases with the increasing of coil length, when coil approaches infinite length, critical length approximates 1. With the rise of relative position, radial magnetic pressure acting on the top end of tube increases, when relative position is equal or greater than 30 mm, radial magnetic pressure of tube top end remains unvaried. Relative position of 30–50 mm is optimal position for electromagnetic tube flanging.

Incremental electromagnetic-assisted stamping (IEMAS) with radial magnetic pressure: A novel deep drawing method for forming aluminum alloy sheets

A new forming method denoted as incremental electromagnetic-assisted stamping (IEMAS) with radial magnetic pressure is proposed in this paper, which was adopted for the deep drawing of a cylindrical cup. In comparison with the traditional stamping process, the forming depth could be increased by 31% after three consecutive coil discharges. A 3D finite element model was built to determine the reason for the increase in forming depth. We found that a radial magnetic force is generated at the sheet center when placing the coil at the end of the sheet, which will produce a material flow from the sheet flange to the region corresponding to the corner of the die after the coil discharge. This ensures that the sheet does not become too thin in a certain region. Therefore, deeper cylindrical cups can be manufactured by IEMAS with radial magnetic pressure.

Deep Drawing of Cylindrical Cup Using Incremental Electromagnetic Assisted Stamping with Radial Magnetic Pressure

A new forming method named incremental electromagnetic assisted stamping with radial magnetic pressure is proposed to draw a deep cylindrical cup. The method combines with traditional stamping, electromagnetic sheet forming and electromagnetic launch technology. Three types of discharge coils are imbedded in die and blank holder, respectively. The 3D finite element model is set up to predict the complex deformation process. The forming process and principle of the new method are discussed. The values of material flow, stress and thickness in different forming processes are compared. In comparison with traditional stamping, incremental electromagnetic assisted stamping with radial magnetic pressure can significantly increase the value of material at sheet end flow inward, decrease the tensile stress and thickness reduction at the easily broken position, and obtain uniform stress distribution. Therefore, deeper cylindrical cup could be manufactured by incremental electromagnetic assisted stamping with radial magnetic pressure.

Characterization of the audible magnetic noise emitted by traction motors in railway rolling stock

This paper first presents the analytical models of an ALSTOM simulation software, DIVA, which computes the vibratory and acoustic behavior of a variable-speed induction machine due to Maxwell forces. This radial magnetic pressure in the air-gap makes the stator vibrate in the audible range, creating the so-called magnetic noise characterized by high tonality. On the basis of these analytical models, the main magnetic vibrations due to slotting, pulse-width modulation (PWM) harmonics and their interaction are then analytically characterized. Their number of nodes, velocity and propagation direction are experimentally validated by visualizing the stator deflection shapes. Finally, some experimental validations of the simulation tool are presented. Both analytical results and simulations show that some quieter motors can be designed with motor geometry (especially slot numbers) and PWM strategy.

Effect of tube size on electromagnetic tube bulging

The commercial finite code ANSYS was employed for the simulation of the electromagnetic tube bulging process. The finite element model and boundary conditions were thoroughly discussed. ANSYS/EMAG was used to model the time varying electromagnetic field in order to obtain the radial and axial magnetic pressure acting on the tube. The magnetic pressure was then used as boundary conditions to model the high velocity deformation of various length tube with ANSYS/LSDYNA. The time space distribution of magnetic pressure on various length tubes was presented. Effect of tube size on the distribution of radial magnetic pressure and axial magnetic pressure and high velocity deformation were discussed. According to the radial magnetic pressure ratio of tube end to tube center and corresponding dimensionless length ratio of tube to coil, the free electromagnetic tube bulging was studied in classification. The calculated results show good agreements with practice.

Simulation of electromagnetic tube bulging based on loose coupling method

A loose coupling method is used to solve the electromagnetic tube bulging. ANSYS/ EMAG is used to model the time varying electromagnetic field with the discharge current used as excitation, in order to obtain the radial and axial magnetic pressure acting on the tube, the magnetic pressure is then used as boundary conditions to model the high velocity deformation of tube with DYNAFORM. The radial magnetic pressure on the tube decreases from the center to the tube end, axial magnetic pressure is greater near the location equal to the coil height and slight in the other region. The radial displacement of deformed workpieces is distributed uniformly near the tube center and decreases from the center to the end; Deformation from the location equal to coil height to the tube end is little. This distribution is consistent with the distribution of radial pressure; Effect of the axial magnetic pressure on deformation can be ignored. The calculated results show well agreements with the experimental results.

Effect of field shaper on magnetic pressure in electromagnetic forming

Field shaper is used as a practical forming tool in electromagnetic forming, which has important influence on the distribution of magnetic field and magnetic pressure. This paper carries out a numerical simulation of magnetic pressure acting on the tube during electromagnetic tube-compression forming with field shaper by means of the FEA software ANSYS. Effects of the field shaper on magnetic pressure are analyzed. The results indicate that greater radial magnetic pressure can be achieved with field shaper than the case without it. With the increase of the effective area of field shaper, the magnetic pressure decreases, and the uniform force area of the tube increases. With the increase of thickness of field shaper wall, magnetic pressure decreases. The distribution of magnetic pressure from simulation is validated with the measurements of the deformed tube by electromagnetic tube-compression forming experiments.

Effects of Mutlipole Cusp Field to the Initial Plasma of Theta Pinch

It is shown that the initial wall hanging current of a theta pinch can be separated from the discharge tube wall by the multipole cusp field. The radial distribution of the azimuthal current was measured by several magnetic probes arranged radially. Under our experimental conditions the plasma current of the initial phase was clearly separated everywhere from a wall at 20 mTorr. The separation was incomplete at higher pressure because of the large reversed field. The average radial magnetic pressure of the multipole field and the condition to separate the plasma current from the tube wall were derived from the simple model that the plasma was the cylindrical column of the perfect conductivity. The experimental results well agreed with the estimation based on this model.