Application Of Electromagnetic Force Research Articles

A novel lapping method for ultraprecision cylindrical rollers based on precision evolution

The geometrical precision of cylindrical rollers is a crucial factor influencing the rotation accuracy of the cylindrical roller bearing and limits of the rotation speed, load bearing capacity and serving life of the bearings. A novel lapping method with a circulating system for batch machining of ultraprecision cylindrical rollers is presented based on the principle of precision evolution. The variations of roller diameter and roundness are improved due to the effect of selective material removal. That is, more material is removed at the convex position for a single roller, and also for the balls with larger diameters, because higher stress concentrated in these areas will lead to plastic deformation and failure. Self-rotation of the rollers was realized by the application of electromagnetic force. Batch lapping of cylindrical rollers was carried out on a newly developed lapping system for approximately 500 rollers. After lapping 90 cycles, the variation of roller diameter for the randomly selected ten rollers, roundness and surface roughness were 0.76 µm, 0.4 µm and 14.93 nm, respectively. Additionally, the variation of roller diameter of 100 randomly selected rollers was 0.97 µm. This geometrical accuracy is higher than that of the highest standard class G1. This method realized the machining of ultraprecision rollers without size sorting and provided a solution for machining rollers with higher diameter consistency than that of the normal industrial manufacturing method. Based on the principle of precision evolution, this work provides a novel machining approach for batch machining of high precision cylindrical rollers.

Direct numerical simulation on relevance of fluctuating velocities and drag reduction in turbulent channel flow with spanwise space-dependent electromagnetic force**Project supported by the National Natural Science Foundation of China (Grant No. 11672135) and a Foundation for the Author of National Excellent Doctoral Dissertation of China (Grant No. 201461).

Based on the Fourier–Chebyshev spectral method, the control of turbulent channel flow by space-dependent electromagnetic force and the mechanism of drag reduction are investigated with direct numerical simulation (DNS) methods for different Reynolds numbers. A formula is derived to express the relation between fluctuating velocities and the friction drag coefficient. With the application of electromagnetic force, the in-depth relations among the fluctuating velocities near the wall, Reynolds stress, and the effect of drag reduction for different Reynolds numbers are discussed. The results indicate that the maximum drag reductions can be obtained with an optimal combination of parameters for each case of different Reynolds numbers. The fluctuating velocities along the streamwise and normal directions are suppressed significantly, while the fluctuating velocity along the spanwise direction is enhanced dramatically due to the spanwise electromagnetic force. However, the values of Reynolds stress depend on the fluctuating velocities along the streamwise and normal directions rather than that along the spanwise direction. Therefore, the significant effect of drag reduction is obtained. Moreover, the maximum drag reduction is weakened due to the decay of control effect for fluctuating velocities as the Reynolds number increases.

Vortex structures and drag reduction in turbulent channel flow with the effect of space-dependent electromagnetic force

The flow of a weakly conductive fluid (i.e. seawater) can be controlled by electromagnetic forces, which holds promising applications in the drag reduction. In this paper, a fully developed weakly conductive turbulent flow controlled by a space-dependent electromagnetic force is investigated with direct numerical simulation (DNS) methods for different Reynolds numbers. With the application of electromagnetic force, the in-depth relations among characteristic structures in the flow field, mean Reynolds shear stress and the effect of drag reduction for different Reynolds numbers are discussed. The numerical results indicate that the well-organized quasi-streamwise vortex structures induced by electromagnetic force are generated with the optimal values of the amplitude and the wave number. The Reynolds shear stress is suppressed and the maximum of drag reduction is obtained with the effect of these structures. However, with the increase of Reynolds number, the wave number of optimal electromagnetic force increases, resulting in the decrease of scale of the well-organized quasi-streamwise vortex structures, which leads to the decrease of the height of these vortex structures. Therefore, the maximum rate of drag reduction decreases due to the decrease of the effective depth with the increase of Reynolds number.

Application of External Electromagnetic Forces for Resistance Spot Welding of Р6М5 Instrumental Steel Parts

Background . Joining of working part of the instrument using mechanical methods or brazing doesn’t ensure its good fixation and isn’t technologically reasonable for mass production purposes . This problem can be solved by application of electromagnetic forces for resistance welding methods based on physical effect on joint formation process. Objective . The aim of the paper is estimation of technological possibilities of resistance spot welding with electromagnetic stirring for joining of instrumental steels. Methods . Transversal opposite-symmetric magnetic field is generated in the working zone. It has equal value but opposite direction of magnetic induction relative to contact plane of parts to be joined for stirring of molten metal with ponderomotive forces. Results . Positive changes of parameters of joint formation were detected. They define mechanical properties of joints. Control of molten metal hydrodynamics resulted in decreasing of sponginess-type imperfections in the central area of the nut. It was shown that changes in thermal processes, leading to decreasing of cooling speed, result in decrease of hardened structures in the moulded zone which, in turn, results in decreasing of microhardness of structure elements. Conclusions . Reasonability and effectiveness of application of electromagnetic forces for resistance spot welding of instrumental steels was proven.

Effects of Magnetic Field on Surface Dielectric Breakdown of Contaminated Printed Wiring Board

With the development of miniaturization and high accumulation of electrical devices, the demand for insulation reliability of printed wiring boards that are installed in these electric and electronic parts is rising. In recent years, there is an increasing need for electrical devices in various complex field environments, which include magnetic field and electrical field. Accordingly, it is necessary to investigate the influence of complex fields on surface insulation breakdown of printed wiring board. In this paper, surface dielectric breakdown phenomena of contaminated printed wiring board under dc magnetic fields were investigated. We employed a dc magnetic field which was made at 100mT, 200mT, 300mT and then up to 500mT according to the laboratory target. The relationship between the number of electrolyte drops to insulation breakdown and relative angle between magnetic field and electrical field was examined. The relative angle between magnetic field and electrical field was 0, 90 and 270 degrees. Loading electrolyte drops between the two electrodes on the sample surface made humid conditions. The study revealed that leakage current increases with 270 degree and decreases with 90 degree under 300mT. The number of drops to breakdown decreased with 270 degree and increases with 90 degree with increasing magnetic fields. Discharge current characteristics under different magnetic field conditions were discussed by using a wavelet transform. The results indicated that the scintillation discharge energy showed a tendency toward increase with 270 degree and decrease with 90 degree when applied magnetic field was applied under 200mT. It is considered that the area of scintillation discharges occurrence was changed by application of electromagnetic force.

5-3 半導体製造プロセスにおける電磁力の応用 : マクロとナノスケールの融合

5-3 半導体製造プロセスにおける電磁力の応用 : マクロとナノスケールの融合

Physical principles in therapeutic apheresis.

Physical modality could have some impact on new apheresis technologies because it is nonbiologic and controllable for its operating conditions. In this article, the application of electromagnetic force and light scattering force to bioseparation and biostimulation was explored.

Recent development and prospect of electromagnetic processing of materials

Application of electromagnetic force to materials processing, so called Electromagnetic Processing of Materials (EPM) has been recognized as a cutting edge technology, especially in the fields of advanced materials processing. The backgroundto promote EPMis described. The present state of EPMis given through a brief introduction of several examples of the applications of a high frequency magnetic field, a DC magnetic field, DC magnetic and electric fields, and a traveling magneticfield. Furthermore, a high static magnetic field has been applied to generate compression waves in molten metals. As otherexamples of the application of a high static field, the crystal orientations in thin films in vapordeposition and electrodeposition processes and those in carbon fibers in a graphitization process are described. Finally the future view of EPM is revealed.

高温超伝導体の電磁力応用

高温超伝導体の電磁力応用