• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1343-1344
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• 2008

This paper analyses current densities induced inside a worker using AC arc welder when he wears a protective cloth. Applying the boundary element method, we calculate current densities induced in organs inside a worker in case he was located at 1[cm], 15[cm], 20[cm] far from a power cable of AC arc welder. As results of study, we find a maximum current density induced in all organs may be lower than 10[$mA/cm^2$] if he wears a protective cloth. We also know high permeability materials can lower current density more than high conductivity materials.

• Structural Engineering and Mechanics
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• v.65 no.4
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• pp.389-400
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• 2018

An exact solution for the title problem was obtained in closed-form fashion considering general boundary conditions. The expressions of moment, shear and shear coefficient (or shear factor) of cross section under the effect of arbitrary temperature distribution were first derived. In view of these relationships, the differential equations of Timoshenko beam under the effect of temperature were obtained and solved. Second, the characteristic equations of Timoshenko beam carrying several spring-mass systems under the effect of temperature were derived based on the continuity and force equilibrium conditions at attaching points. Then, the correctness of proposed method was demonstrated by a Timoshenko laboratory beam and several finite element models. Finally, the influence law of different temperature distribution modes and parameters of spring-mass system on the modal characteristics of Timoshenko beam had been studied, respectively.

• Advances in aircraft and spacecraft science
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• v.5 no.5
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• pp.515-531
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• 2018

In this manuscript, buckling response of the functionally graded material (FGM) nanoplate is investigated. Two opposite edges of nanoplate is under linear and nonlinear varying normal stresses. The small-scale effect is considered by Eringen's nonlocal theory. Governing equation are derived by nonlocal theory and Hamilton's principle. Navier's method is used to solve governing equation in simply boundary conditions. The obtained results exactly match the available results in the literature. The results of this research show the important role of nonlocal effect in buckling and stability behavior of nanoplates. In order to study the FG-index effect and different loading condition effects on buckling of rectangular nanoplate, Navier's method is applied and results are presented in various figures and tables.

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.57-64
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• 2005

Aerodynamic characteristics of three-dimensional wings in ground effect for Aero-levitation Electric Vehicle(AEV) are numerically investigated for various fairing shapes at the junctions of 3D Wings. Numerical results show that a sizeable three-dimensional comer flow separation occurs with formation of an arch vortex at the junction of main and vertical wings, and also that this is predicted the main cause of the high lift-to-drag(L/D) reduction rate of the main wing. To avoid the comer flow separation, the main idea of this study is to reduce the cross section gradient of the comer flow tube near the trailing edge for various fairing shapes. Improvements on L/D ratios of the wings are pursued by breaking the coherence of superimposed adverse pressure gradients at the wing junction when the cross section gradient is changed slowly at the trailing edge.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.121-125
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• 2008

In this study, the characteristics of internal flow and the heat transfer performance of dimpled plate heat exchanger were numerically investigated. For the numerical analysis, conjugate heat transfer method between cold fluid - plate - hot fluid was studied with appropriate boundary conditions. Velocity magnitude, temperature and pressure distribution were obtained from the simulation. Correlations for fanning f-factor and Colburn j-factor were obtained from numerical results and compared to the experimented data.

• Journal of Mechanical Science and Technology
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• v.18 no.10
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• pp.1869-1879
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• 2004

The present study has numerically investigated two-dimensional flow over three circular cylinders in an equidistant side-by-side arrangement at a low Reynolds number. For the study, numerical simulations are performed, using the immersed boundary method, in the range of g* < 5 at Re= 100, where g* is the spacing between two adjacent cylinder surfaces divided by the cylinder diameter. Results show that the flow characteristics significantly depend on the gap spacing and a total of five kinds of wake patterns are observed over the range: modulation-synchronized (g* (equation omitted) 2), inphase-synchronized (g* (equation omitted) 1.5) , flip-flopping (0.3 < g* (equation omitted) 1.2) , deflected (g* (equation omitted) 0.3), and single bluff-body patterns (g* < 0.3). Moreover, the parallel and symmetric modes are also observed depending on g* in the regime of the flip-flopping pattern. The corresponding flow fields and statistics are presented to verify the observations.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.6
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• pp.935-941
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• 1998

Experiments were carried out for a cubic cavity flow. Contrinuous shear stress is supplied by driven flow for high Reynolds number and three kinds of aspect ratios. Velocity vectors are obtained by PIV and they are used as velocity components for Poisson equation for pressure, Related boundary conditions and no-slip condition at solid wall and the linear velocity extrapolation on the upper side of cavity are well examined for the present study. For calculation of pressure resolution of grid is basically $40{\times}40$ and 2-dimensional uniform mesh using MSC staggered grid is adopted. The flow field within the cavity maintains a forced-vortex formation and almost of the shear stress from the driving inflow is transformed into rotating flow energy and the size of the distorted forced-vortex increases with increment of Reynolds number

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.2
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• pp.41-53
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• 1994

In this paper, rotating-bending fatigue tests of the SiC-whisker- reinforced 6061-T6 aluminum alloy and 6061-T6 alumiunm alloy made by power metallurgy were carried out to investigate the fatigue characteristics of plain and notched specimens at room temperature. The fatigue mechnisms in both materials were clarified through successive surface observations using the plastic replica method. In the case of the SiC-whisker-reinforced composites, there are whisker rich and poor zones and the fatigue crack is nucleated from the end of whiskers near the boundary. On the other hand, in the case of the 6061-T6 aluminum alloy, the fatigue crack is nucleated from defects and propagates by shear. Moreover, the results were discussed based on linear notch mechanics.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.242-247
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• 2000

In this study, the Rayleigh's energy method and the Rayleigh-Ritz method on the basis of Flugge's shell theory was used to analyze the dynamic characteristics of the scroll compressor housing with clamped boundary condition. The frequencies and mode shapes from theoretical calculation were compared with those of commercial finite element code, ANSYS. In order to validate the theory, modal test was also performed by impact test and FFT analysis.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.3
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• pp.44-51
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• 1997

Unsteady-state temperature distributions and thermal deformations of the spindle of a high precision lathe are studied in this paper. Three dimensional model is built for analysis, and the amount of heat generation of bearing and the thermal characteristic values including heat transfer coefficient are estimated. Temperature distributions and thermal deformations of a model are analyzed using the finite element method and the thermal boundary values. Numerical results are compared with the measured data. The results show that the thermal deformations and the temperature distributions of the dpindle of a high precision lathe can be reasonably estimated using the three dimensional model and the finite element method.