• Journal of Magnetics
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• v.21 no.2
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• pp.215-221
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• 2016

We conducted a phased electromagnetic forming process analysis (EFPA) over time through a coupling of electromagnetic analysis and structural analysis. The analysis is conducted through a direct linkage between electromagnetic analysis and structural analysis. The analysis process is repeated until the electric current is completely discharged by a formed coil. We calculate the forming force that affects the workpiece using MAXWELL, a commercial electromagnetic finite element analysis program. Then, we simulate plastic behavior by using the calculated forming force data as the forming force input to ANSYS, a commercial structure finite element analysis program. We calculate the forming force data by using the model shape in MAXWELL, a commercial electromagnetic finite element analysis program. We repeat the process until the current is fully discharged by the formed coil. Our results can be used to reduce the error in data transformation with a reduced number of data transformations, because the proposed approach directly links the electromagnetic analysis and the structural analysis after removing the step of the numerical analysis of a graph describing the forming force, unlike the existing electromagnetic forming process. Second, it is possible to simulate a more realistic forming force by keeping a certain distance between nodes using the re-mesh function during the repeated analysis until the current is completely discharged by the formed coil, based on the MAXWELL results. We compare and review the results of the EFPA using the peak value of the forming force that acts on the workpiece (which is the existing analysis method), and the proposed phased EFPA over time approach.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.8
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• pp.695-701
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• 2002

Maxwell displacement current (MDC) measuring technique has been applied on the study of monolayers of fatty acid and polyamic acid mixture. The displacement current was generated from monolayers on the water surface by monolayer compression and expansion. Displacement current was generated when the area per molecule was about 132 $^2$and 115 $^2$just before the initial rise of the surface pressure during the 1st and 2nd mixed monolayer compressions cycle, respectively. Maxwell displacement currents were investigated in connection with mixed monolayer compression cycles. It was found that the maximum of MDC appeared at the molecular area just before the initial rise of surface pressure in compression cycles. Ultra thin film of fatty acid and polyamic acid mixture was prepared on the hydrophilic quartz plate by Langmuir-Blodgett (LB) method. The precursor LB film was heated in a vacuum dry oven at 12$0^{\circ}C$ in order to convert it into the LB film of polyimide. The absorption spectra of LB films were also induced photoisomerization by UV and visible light irradiation.

• Journal of ILASS-Korea
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• v.20 no.1
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• pp.53-58
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• 2015

In this study, we prepare the Ag nanofluids synthesized by the chemical reduction method and measure the extinction coefficient of those nanofluids at a wavelength of 632.8 nm. The Ag nanofluids are synthesized by the chemical reduction method using silver nitrate ($AgNO_3$) and sodium borohydride ($NaBH_4$) in water and ethylene glycol (EG). For stable dispersion of Ag particles in the base liquids, polyvinyl pyrrolidone (PVP) is added as a surfactant. The extinction coefficient of manufactured Ag nanofluids is measured by an in-house developed measurement system at the wavelength of 632.8 nm. The results show that the extinction coefficient of water-based and EG-based Ag nanofluids is linearly increased with respect to the particle loadings. Moreover, it is shown that the extinction coefficient of EG-based Ag nanofludis is higher than that of water-based Ag nanofluids. Finally we compare the experimental results with both the Maxwell-Garnett model and Rayleigh scattering approximation model, and they demonstrate that the Rayleigh scattering approximation model is reasonably predict the extinction coefficient of Ag nanofluids using hydraulic diameter of silver nanoparticle.

• Smart Structures and Systems
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• v.9 no.5
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• pp.427-439
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• 2012

The present paper deals with the analytical solution of a functionally graded piezoelectric (FGP) cylinder in the magnetic field under mechanical, thermal and electrical loads. All mechanical, thermal and electrical properties except Poisson ratio can be varied continuously and gradually along the thickness direction of the cylinder based on a power function. The cylinder is assumed to be axisymmetric. Steady state heat transfer equation is solved by considering the appropriate boundary conditions. Using Maxwell electro dynamic equation and assumed magnetic field along the axis of the cylinder, Lorentz's force due to magnetic field is evaluated for non homogenous state. This force can be employed as a body force in the equilibrium equation. Equilibrium and Maxwell equations are two fundamental equations for analysis of the problem. Comprehensive solution of Maxwell equation is considered in the present paper for general states of non homogeneity. Solution of governing equations may be obtained using solution of the characteristic equation of the system. Achieved results indicate that with increasing the non homogenous index, different mechanical and electrical components present different behaviors along the thickness direction. FGP can control the distribution of the mechanical and electrical components in various structures with good precision. For intelligent properties of functionally graded piezoelectric materials, these materials can be used as an actuator, sensor or a component of piezo motor in electromechanical systems.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.11
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• pp.1591-1599
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• 2017

In power electronics applications which switching frequency is below audible frequency, the acoustic noise and vibration design of magnetics are as important as the efficiency. In the case of the powder core, which is widely used in grid-connected inverters, many researches have been progressed in terms of efficiency. However, there are only few research have been progressed related with acoustic noise and vibrations. In this paper, the Sendust(Fe-Si-Al) powder core material which has low magnetostriction and low core loss is analyzed in terms of acoustic noise and vibration induced by Maxwell force and magnetostriction. Three building structures such as, rectangular, toroidal, and oval shape are designed for 4kW grid-connected inverter, because magnetic properties and the audible noises of the inductor are varied by magnetic core building structures. The effects of the Maxwell force and magnetostriction behaviors varied with core shapes are analyzed by finite element method and experiments. In addition, experiment results of the inductor efficiency are presented according to core building structures.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.847-849
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• 1996

As the power demands increases, one of the most important data is inside electric field of equipment in designing of insulators ami insulated wire for EHV distribution line. So far finite element analysis method is widely used to calculate this electric field. However as the shape of insulator becomes complicated, it is difficult in producing the mesh which suitable the shape. Especially, we have many difficulty that produce dense fine mesh only where the electric field is concentrated. Therefore in this paper, we perform the each conditional analysis of electric field using the Maxwell 3D Simulator to recover this defects. And we try to analyze electric field through the conventional 2 dimensional and 3 dimensional analysis in case of salt contamination on the surface of a insulator.

• Polymer(Korea)
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• v.35 no.3
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• pp.232-237
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• 2011

The relaxation spectra of polyacrylonitrile-poly(vinyl chloride) copolymer filament fibers were obtained by applying the experimental stress relaxation curves to the theoretical equation of relaxation spectrum. The theoretical equation of relaxation spectrum was derived from the Ree-Eyring and Maxwell model. The experimental of stress relaxation was carried out using a tensile tester with a solvent chamber. The determination of relaxation spectra was performed by computer calculation. From the relaxation spectra, the fine structures, viscoelastic properties and hole volumes of solid polymers were studied. It was observed that the relaxation spectra of these samples were directly related to the distribution of molecular weights and self diffusions of flow segments.

• Korean Journal of Food Science and Technology
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• v.18 no.3
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• pp.215-220
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• 1986

Mechanical properties of 9-30% starch gels from naked and covered barley were investigated with rheometer or rotation viscosimeter. The compression-penetration curves of 20 and 30% gels were characterized by deformations containing elastic, plastic and fracture regions under the load of 0-2kg. The compressive stress relaxation test showed that the viscoelastic properties of 20% gels may be represented by four element Maxwell model consisting of two Maxwell element in parallel. Also, stress-decay under the steady shear of 9% covered starch gel was able to be interpreted by linear viscoelastic model and stress-decay process was suggested to be effective to investigate the effect of temperature or additives on gel structure.

• Journal of Drive and Control
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• v.9 no.1
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• pp.32-36
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• 2012

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.11B no.4
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• pp.137-145
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• 2001

The magnetic force calculation methods, the Maxwell＇s stress tensor method, virtual work method, and nodal force method, are reviewed and the equivalence of them are theoretically proved. The methods are applied to the magnetic force calculation of 2D linear and nonlinear problems, and 3D nonlinear problem. As the results, the convergence of the methods as the number of elements increases, accuracy of the methods, and integral path dependence of the methods are discussed. Finally some recommendations on the usage of the methods, including the determination of the integral path, are given.