• Proceedings of the KWS Conference
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• 2005.11a
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• pp.243-245
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• 2005

Recently many research are going on in the field of application of Laser-Arc hybrid welding for superstructures such as shop-structures, transport vehicles etc. However, the study on heat distribution and welding residual stress of hybrid weld by numerical simulation leaves much to be desired. Therefore in this study an optimized welding condition and numerical simulation for hybrid welding by using previous numerical analysis which is used to calculate the heat source for hybrid welding has been analyzed.

• Journal of Welding and Joining
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• v.28 no.4
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• pp.55-60
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• 2010

The purpose of this paper is to propose a mathematical model of welding current for the P-GMAW by modifying the well known GMAW model. Welding power circuit is simply modeled as a RL electric circuit and solved as an ODE equation. The welding current depends on the joint shape, molten pool and welding parameters. To compare the molten pool effect to the welding current, CFD numerical simulation technique was adopted. Welding experiment is also conducted with the same welding parameters as used in numerical simulations to verify the proposed welding current model. The current model which is considered molten pool shape, is more fit to experiment result.

• Nuclear Engineering and Technology
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• v.34 no.6
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• pp.574-585
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• 2002

The microstructural characteristics and its related mechanical properties of RPV cladding have been investigated using small punch (SP) tests. SA508 Cl.3 RPV steel plates were overlay cladded with the type ER309L welding consumables by submerged arc welding process. Although the RPV clad material had a small portion of 5 ferrite phase, it still showed the ductile to brittle transition behavior The transition temperature was determined by the SP test and it depended on the content of $\sigma$ phase, specimen size, and determination methods. The fracture appearance of SP specimen was changed from circumferential to radial cracking as test temperature became low, and below the transition temperature region, ER309L cladding usually fractured along the 6 ferrite by the low temperature failure of ferrite phase.

• Journal of Welding and Joining
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• v.12 no.2
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• pp.108-118
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• 1994

In the present study, the dynamic crack initiation toughness and total absorbed energy behavior of Heat Affected Zone(HAZ) was experimentally evaluated for SS41 steel welding. The materials were submerged arc-welded SS41 steel plate with thickness 19mm. The test temperature range was from $20^{\circ}C$(room temperature) to $-70^{\circ}C$ The HAZ of welding were divided into three sub-zones for analysis; H1, H2, H3, according to the distance from the fushion line. From the experimental studies, the reference value of dynamic crack initiation toughness $(J_{Id(R)})$ can be use to estimate dynamic fracture toughness characteristics of steel welding.

• Journal of the Korean institute of surface engineering
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• v.25 no.6
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• pp.299-308
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• 1992

Titanium nitride(TiN) has been synthesized by nitrogen ion irradiation onto the Ti thin film deposited on STD11 and SKH9 tool materials. The effect of irradiation flux and substrate temperature on the formation behavior and mechanical properaties of TiN were investigated through X-ray diffraction analysis, hardness and pin-on-disc wear testings. Nitrogen ion irradiation onto arc evaporated Ti thin film produced TiN of < 200> orientation at elevated temperature and thereby enhancing surface microhardness by 50% at maximum. Wear resistance was also improved by nitrogen irradiation at most process conditions. The enhancement of wear resistance appeared to be more effective for the nitrogen irradiated conditions at room temperature than at elevated temperature.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.04a
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• pp.9-18
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• 1996

The primary objective of this paper is to grasp many characteristics of buckling behavior of latticed spherical domes under various conditions. The Arc-Length Method proposed by E.Riks is used for the computation and evaluation of geometrically nonlinear fundamental equilibrium paths and bifurcation points. And the direction of the path after the bifurcation point is decided by means of Hosono's concept. Three different nonlinear stiffness matrices of the Slope-Deflection Method are derived for the system with rigid nodes and results of the numerical analysis are examined in regard in geometrical parameters such as slenderness ratio, half-open angle, boundary conditions, and various loading types. But in case of analytical model 2 (rigid node), the post-buckling path could not be surveyed because of Newton-Raphson iteration process being diversed on the critical point since many eigenvalues become zero simultaneously.

• Structural Engineering and Mechanics
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• v.49 no.6
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• pp.727-743
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• 2014

Geometrically nonlinear analysis of planar beam and frame structures made of functionally graded material (FGM) by using the finite element method is presented. The material property of the structures is assumed to be graded in the thickness direction by a power law distribution. A nonlinear beam element based on Bernoulli beam theory, taking the shift of the neutral axis position into account, is formulated in the context of the co-rotational formulation. The nonlinear equilibrium equations are solved by using the incremental/iterative procedure in a combination with the arc-length control method. Numerical examples show that the formulated element is capable to give accurate results by using just several elements. The influence of the material inhomogeneity in the geometrically nonlinear behavior of the FGM beam and frame structures is examined and highlighted.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.05a
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• pp.19-23
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• 2004

Light is an environmental element which is essential for a man to live and do creative activities in residential area. Especially, modern people arc used to live under artificial light interior surroundings for much time. Currently, the average illumination level of the present apartment is improving, but it still does not reach the recommended level because the present apartment's luminous environment is only based on the life behavior which puts its priority to clear vision. Therefore, it is necessary that proper standard illumination must be used for various use and purpose. From this point of view, this paper investigated the essence of light in the residential area and the luminous environment for apartments was measured. This paper finally suggested well-coordinated lighting condition, derived from the measurement and analysis of luminous environment in these cases.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.531-532
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• 2006

The effects of compaction pressure and sintering temperature on the densification of Fe-40wt%Ni alloy nanoparticles were analyzed. The Fe-Ni nanoparticles were fabricated by an arc-discharge method and then, compacted at three different pressures and sintered at 550 to $900\;^{\circ}C$. Densification was completed at temperature as low as $600\;^{\circ}C$ and high-pressure compaction was found to enhance densification. Densification behaviors and microstructure developments have been investigated through density measurements, electron microscopies, and hardness measurements.

• Journal of Welding and Joining
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• v.16 no.1
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• pp.114-124
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• 1998

The effect of matrix phase (austenite, pearlite, martensite) on the low stress abrasion resistance in the chromium-carbide-type high Cr white iorn hardfacing weld deposites has been investigated. In order to examine matrix phase, a series of alloys with different matrix phase by changing the ratio of Cr/C system by heat treatment were employed. The alloys were deposited twice on a mild steel plate using self-shielding flux cored arc welding process. The low stress abrasion resistance of the alloys against sands was measured by the Dry Sand/Rubber Wheel Abrasion Test(RWAT). Even though formation of pearlite phase in the matrix showed higher hardness than that of austenite, there was no observable difference in wear resistance between the pearlite and austenite phase for the same amount of chromium-carbide in the matrix. On the other hand, the formation of martensitic phase,, from heat treated austenitic alloys (high content of Cr), enhanced wear resistance due to its fine secondary precipitates.