• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.45-48
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• 1997

The low frequency pulsed MIG welding process of new current waveform control to switch over unit pulse conditions (pulse current, pulse duration) in the fixed cycle was developed and its effect were investigated for aluminium and its alloy. By using this new welding process, the bead appearance having clear ripple pattern, such as TIG welding bead can be obtained and the gap tolerance of lap and butt welding joint can be expanded.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.13 no.3
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• pp.168-182
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• 1984

For the purpose of drying high moisture rough rice effectively, from the view point of pre-drying, some basic experiments of fluidized bed drying of rough rice were carried out. The minimum fluidization velocities $(U_{mf})$ for both rough rice and glass bead were analyzed to find out fluidizing characteristics. The main results obtained were as follows ; 1) Minimum fluidization velocity of rough rice and glass bead were 2.01m/s and 4.07m/s, respectively, when using the distributor with $16\%$ opening ratio. 2) $U_{mf}$ calculated by Shirai's empirical equation and that calculated by Wen's modified equation were inconsistent with experimental data, while $U_{mf}$ calculated by Ergun's equation was consistent with the experimental data. 3) The following equations, on the basis of Leva's equation, were obtained. $$C_{mf}=1.19\times10^{-4}(Re_p)^{-0.0318)\;(rough rice)$$ $$C_{mf}=1.02imes10^{-4}(Re_p)^{-0.0047)\;(glass bead)$$

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.10a
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• pp.298-303
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• 1997

Over the last few year, there has been a growing interest in quantitative representation of heat transfer phenomena in weld pools in order to relate the processing conditions to the quality of the weldment produced and to use this information for the optimisation and robotization of the welding process. Normally, a theoretical model offers a powerful alternative to check out the physical concepts of the welding process and to calculate the effects of varying any of parameters. To solve this problem, a transient 2D(two-dimensional) heat conduction were developed for determining bead geometry and temperature distribution for the GMA welding process. The equation was solved using a general thermofluid-mechanics computer program, PHOENICS code, which is based on the SIMPLE algorithm. The simulation results showed that the calculated bead geometry from the developed models reasonablely agree with the experiment results.

• Journal of Energy Engineering
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• v.21 no.1
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• pp.43-46
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• 2012

A fluidized bed drying approach was utilized to the synthesis of water glass based silica aerogel powders. The effects of the fluidized bed drying conditions such as the superficial velocity and temperature of hot air and bead size as well as bead/wet-gel ratio, on the physical properties such as tapping density and productivity of the aerogel powders were systematically investigated. The experimental results showed that the amount of beads mixed with wet-gels in the fluidized bed column has the most profound impact on the fluidization efficiency, greatly enhancing the yield of the aerogel powders up to 98% with a proper bead/wet-gel weight ratio as compared to 72% without using beads. No significant change was observed in the tapping density over a wide range of the fluidized drying condition. Consequently the fluidized bed drying approach shows a good promise as an alternative route for the large-scale production of the aerogel powders.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.1
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• pp.96-101
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• 2011

Under extreme test or operation condition, refrigerator endures complicated stresses state and thermal bowing deformation arises on the sidewall. Shelf rails designed in the inner case provide increased surface area to permit expansion without bowing, and also increase structural rigidity to resist bowing. In this study, we designed six different shelf patterns of refrigerator model and studied the bead on refrigerator deformation using finite element method (FEM). Analysis result shows that increasing the numbers of beads properly in refrigerator is more helpful to reduce thermal bowing deformation. In addition, the beads would decrease stress on refrigerator sidewall. However, vertical beads have no effect to reduce thermal deformation of the bowing.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.8
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• pp.142-147
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• 2009

Spinal fixation systems provide surgical versatility, but the complexity of their design reduces their strength and fatigue resistance. There is no published data on the mechanical properties of such screws. Screws were assembled according to a vertebrectomy model for destructive mechanical testing. A group of two assemblies was tested in static compression. One group was applied to surface a grit blasting method and another group was applied to surface a bead blasting method. Modes of failure, yield, and ultimate strength, yield stiffness, and cycles to failure were determined for six assembles. Static compression 2% offset yield load ranges was from 327 to 419N. Fatigue loads were determined two levels, 37.5% and 50% of the average load from static compression ultimate load. An assembly of bead blasting treatment only achieved 5 million cycles at 37.5% level in compression bending.

• Transactions of Materials Processing
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• v.9 no.3
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• pp.284-292
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• 2000

Optimization of the process parameters is carried out for process design in sheet metal forming processes. The scheme incorporates with a rigid-plastic finite element method for the deformation analysis and response surface methodology for the optimum searching of process parameters. The algorithm developed is applied to design of the draw bead force and the die radius in deep drawing processes of rectangular cups. The present algorithm shows the capability of designing process parameters which enable the prevention of the weak part of fracture during processes.

• Journal of Welding and Joining
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• v.23 no.1
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• pp.48-54
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• 2005

Laser keyhole welding is investigated using a three-dimensional Gaussian heat source, and the heat source parameters such as the keyhole depth, welding efficiency and power density distribution factor are determined in a systematic way. For partial penetration, the keyhole depth is same as the penetration and is predicted using the experimental data. The welding efficiency is calculated using the ray-tracing method and the power density distribution factor is determined from the bead shape. Full penetration is classified into the transition, normal and excessive modes depending on the degree of keyhole opening. Thermal analysis of the bead-on-plate welds is conducted using the Gaussian heat source, and the calculated weld geometries show reasonably good agreements with the experimental results.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.12
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• pp.146-153
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• 2004

We compared the fatigue characteristics of weld metal with those of base metal, and not heat-treated with heat-treated. Also, we examined the influence of bead in a viewpoint of fatigue life. From the experimental results, it has been seen that the fatigue characteristics of welded specimens grinded the toe of bead are slightly better than not grinded. We have seen that the fatigue life is affected more by the stress concentration on the profile change in the weld toe rather than by residual stress influence, because heat-treated or not had almost no influence on the fatigue characteristics.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1025-1028
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• 2004

In this paper, we studied low cycle fatigue behavior of laser welded sheet metal that used automobile body panel. Specimens were manufactured as weld condition and sheet metal using automobile manufacturing company at present. For to know mechanical properties, micro Vicker's hardness test was performed of specimens. But, we can't confirm mechanical properties of weld bead and heat affected zone because laser weld makes very narrow weld bead and heat affected zone than other welding method. Therefore, we performed low cycle fatigue test with similar weldment, dissimilar weldment, similar thickness and dissimilar weldment, and dissimilar thickness and dissimilar weldment for fatigue properties of thickness and welding direction. As well, we analysis stress distribution of base metal, weld bead, and heat affected zone according to strain load using finite element method.