• Journal of Magnetics
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• v.22 no.1
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• pp.133-140
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• 2017

Split magnetic fluid sealing is a combination of magnetic fluid rotary and plane sealing. Using the theory of equivalent magnetic circuit design as basis, the author theorized the pressure resistance performance of magnetic fluid plane sealing. To determine the pressure resistance of magnetic fluid plane sealing, the author adopted the method of finite element analysis to calculate the magnetic field intensity in the gap between plane sealing structures. The author also analyzed the effect of different sealing gaps, as well as different ratios between the sealing gap and tooth and solt width, on the sealing performance of split magnetic fluid. Results showed that the wider the sealing gap, the lower the sealing performance. Tooth width strongly affects sealing performance; the sealing performance is best when the ratio between tooth width and sealing gap is 2, whereas the sealing performance is poor when the ratio is over 8. The sealing performance is best when the ratio between the solt width and sealing gap is 4, indicating a slight effect on sealing performance when the ratio between the solt width and sealing gap is higher. Theoretical analysis and simulation results provide reference for the performance evaluation of different sealing equipment and estimation of critical pressure at interface failure.

• The Journal of the Acoustical Society of Korea
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• v.30 no.4
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• pp.223-230
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• 2011

Korean bell is hung with some air gap between the bell bottom and the ground. In addition, it has a peculiar acoustic element, so called resonance cavity below the bell. A proper design of the air gap and cavity size dramatically amplifies the bell sound by resonance effect. Bell interior cavity, air gap and resonance cavity consist of an acoustic cavity system. When the acoustic cavity frequency coincides with the natural frequency of the bell body, the frequency component is significantly amplified. On the Sacred Bell of the Great King Seongdeok, this study proposes a resonance condition of the cavity system considering air gap effect for the first time. With the exact dimension of the bell, boundary element analysis is performed using SYSNOISE. Finally, this study reveals how the temperature in season influences the resonance condition and proposes a concept of variable type resonance cavity. By using the variable type resonance cavity, the cavity size is controlled on site and exact resonance is available regardless of temperature difference in season.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.441-446
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• 2011

To investigate aerodynamic performance of high-lift devices, 2D design is the base of the success of high-lift system design for transport aircraft, which can shorten the periods of three-dimensional design and analysis. For the simulation coupled viscous and inviscous euler method (MSES) is used. In this parametric study, Gap and Overlap which can define position of flap is used as design variables and we investigale relation between angle of attack and flap position for lift enhancement.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.252-255
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• 2009

The roll gap set-up in the finishing mill is one of the most important technologies in the hot plate rolling process. As the target thickness can be obtained by the correct set-up of the roll gap, improving the roll gap set-up technology is very critical for plate thickness accuracy. The main cause of thickness variation in hot plate mills is the non-uniform temperature distribution along the length of the slab. The objective of this study is to adjust the roll gap set-up for the thickness accuracy of plate in hot rolling process considering top-end temperature drop. Therefore this study has concentrated on determining the correct amounts of roll gap to compensate thickness variation due to top-end temperature drop. The off-line simulation of compensated roil gap significantly decreases top-end thickness variation.

• Computational Structural Engineering
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• v.6 no.4
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• pp.99-105
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• 1993

In this paper a useful method on evaluating the joint stiffness of a bolted member was introduced using optimization technique on the basis of Finite Element Method. A finite element model having one directional gap element at boundary area was introduced to compensate the prying force in jointed members which might be caused by geometrical configuration of members. Results showed a good agreement with classical method in certain range and will be available to define the appropriate design margin of pre-load design.

• Journal of the Korea Institute of Military Science and Technology
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• v.2 no.2
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• pp.92-98
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• 1999

Dynamic behavior of missile which is fired in canister is analyzed by flexible multibody dynamics. The bending elasticity of missile is very important in case that missile is fired in the inclined launcher. In this paper, the force element model for the missile launching stage and the finite element model of missile are developed. The FEA model of missile is condensed into five lumped mass element model and the consistence between FE model and lumped mass model of missile is verified by modal analysis. As a result of analysis, sabot reaction force and pitch rate of missile for the variation of gap size and force element are obtained.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.5
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• pp.460-467
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• 2002

This paper deals with the distribution characteristics of the current density and axial magnetic flux density on the vacuum interrupter with axial magnetic field type using 3 dimension finite element analysis. An axial magnetic field parallel to the current flow in the arc column can improve the current breaking capacity of vacuum interrupter by affecting the arc mode. The axial magnetic flux density on the contact electrode surface is analyzed by inputting external current as a function of the transient time for sine half wave. And it also is analyzed within the gap distance of the contact electrode. The peak value of current but is decreased with the descending current on the contact electrode surface and within the gap distance of the contact electrode. The residual magnetic field is generated on the contact electrode surface and within the gap distance in the instant of zero current, which is due to the influence of eddy currents. The phase shift due to eddy currents, defined as time difference between the maximum value of current and axial magnetic field, is about 1ms in the center point of gap distance.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.8
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• pp.957-964
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• 2011

This investigation presents a finite element method to obtain the transmission properties of bulk elastic waves in piezoelectric band gap structures(phonon crystals) for varying frequencies and modes. To this end, periodic boundary conditions are imposed on a three-dimensional model while both in-plane and out-of-plane modes are included. In particular, the mode decoupling characteristics between in-plane and out-of-plane modes are identified for each electric poling direction and the results are incorporated in the finite element modeling. Through numerical simulations, the proposed modeling method was found to be a useful, effective one for analyzing the wave characteristics of various types of piezoelectric phononic band gap structures.

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.6
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• pp.611-624
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• 2001

A precise fit of the implant prosthesis is one of the most important factors in preventing mechanical complications. To analyze the degree of the misfit of implant prosthesis, a modal testing experiment was accomplished. And. to interpret the modal testing analysis mathematically, three-dimensional finite element models were established. In the experimental modal testing analysis, with a laser displacement meter, FFT analyzer, impact hammer, etc., natural frequencies of the models with various degree of prosthesis fit were determined after the frequency response function were calculated. In the finite element analysis, the natural frequencies and mode shapes of the models which simulated those of experimental modal testing were computed. The results were as follows: 1. Natural frequencies of the prosthesis-abutment were related to the contact state between components. 2. In the modal testing experiment, the natural frequencies increased from $50{\mu}m$ to $200{\mu}m$ gap and reached a plateau. 3. In the finite element analysis, the natural frequencies decreased gradually according to the in crease of the gap size. 4. In the finite element analysis, the mode shapes of model 1 with misfitting prosthesis showed different patterns from those without misfitting prosthesis. 5. The devices including a laser displacement meter used in this study were useful for measuring the natural frequencies of an implant prosthesis which had various degrees of fit.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.06a
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• pp.201-210
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• 2000

The noncontacting groove end face seal is one of various approaches to sealing gases with a single seal. Gas pumped into groove maintains operating gap and lubricates between primary ring and mating ring. So it removes heat and decreases face wear. In this paper, K-type and T-type grooved seals have been analyzed numerically using the finite element method. It explains the effects of groove shapes in gas seals along rotating speeds with a temperature gradient, face distortion, stress and so on. The calculated FEM results show the operating gap and rotating speed are strongly related to the leakages of a gas seal and that T-type groove seal shows a good thermal performance compared to K-type groove seal.