• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.405-408
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• 2003

Generally, the life of casting mold is limited by fatigue fracture or dimensional inaccuracy originated from wear in high temperature. Although recent research of metallic materials in high temperature fatigue have been much accomplished, many studies on brittle material as a die steel in high temperature fatigue does not have been reported. Especially, the study on the fatigue behavior over the transformation temperature is not studied sufficiently because of its difficult analysis and experiment. Therefore, reliable results of brittle material in high temperature fatigue behavior are needed. In this paper, stress-strain curves and stress-life curves in die STD61 steel are carefully examined between room temperature and 90$0^{\circ}C$, as the basic experimental data are used to predict from fatigue life of casting mold.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 제3회 압연심포지엄 논문집 압연기술의 미래개척 (Exploitation of Future Rolling Technologies)
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• pp.262-271
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• 1999

This work was intended to modify the solidification structure of high speed steel roll material for hot strip mill, by the introduction of alloying elements designed to form primary carbide dispersions via melt treatment procedure. Solidification structure was modified by the melt treatment with titanium and distribution. This modifying effect could be attributed to the fact that the nuclie formed at high temperature upon inoculation induce the formation of fine equiaxed grain and primary carbide during solification, which is also likely to be responsible for the fact that TiC acts as effective nuclie for primary VC solidification.

• 소성∙가공
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• 제15권8호
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• pp.568-573
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• 2006

In order to numerically evaluate automotive hydro-formed DP-steel tubes on crash performance considering welding heat effects, the finite element simulations of crash behavior were performed for hydro-formed tubes with and without heat treatment effects. This work involves the mechanical characterization of the base material and the HAG-welded zone as well as finite element simulations of the crash test of hydro-formed tubes with welded brackets and hydro-forming of tubes. The welding heat effects on the crash performance are evaluated in efforts to improve the process optimization procedure of the engine cradle in the design stage. In particular, FEM simulations on indentations have been performed and experimentally verified for material properties of weld zone and heat affected zone.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2003년도 추계학술발표대회 개요집
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• pp.103-105
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• 2003

Currently, duplex and superduplex stainless steels are widely used for piping system in offshore unit because of its excellent combination of strength and corrosion resistance properties. Also, the usage of duplex and superduplex stainless steel is steadily increasing with getting into step with development of offshore industries. In spite of excellent merits in mechanical and chemical properties of base materials, sometimes stringent requirements in welding procedure qualification and fabrication of duplex class material have regulated not only the application of various high-efficiency welding processes but also applicable welding parameters. This study is focused on hardness requirement which is known as one of the most stringent factor in duplex class material welding and this study aims to evaluate the effects of cutting and welding methodology on hardness values of duplex and superduplex stainless steel weldments.

• 복합신소재구조학회 논문집
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• 제4권3호
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• pp.13-21
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• 2013

In this study, uniaxial compression tests were performed to investigates the stress-strain relations of Double Skinned Composite Tubular Columns reinforced with steel tube. The confined concrete has been known as the strength of concrete increases significantly. Specimens reinforced with outer and inner steel tube were tested by uniaxial compression test. To investigate the influence of concrete strength increase by confining conditions in steel tubes, 8 specimens with different thickness of tube, hollowness ratio and concrete strength were tested and compared with other researcher's concrete material model.

• 대한기계학회논문집
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• 제9권5호
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• pp.564-571
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• 1985

본 논문에서는 미시조직인자를 변화시킨 마르텐사이트-페라이트 복합조직강을 준비하여 균열선단 및 안정영역의 파괴양상과 파괴저항과의 관계를 검토하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.390-393
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• 2001

This study demonstrated the feasibility of tape casting method to fabricate soda borosilicate glass-coated stainless steel electrostatic chucks(ESC) for low temperature semiconductor processes. The glass coatings on the stainless steel substrates ranged from $100{\mu}m$ to $150{\mu}m$ thick. The adhesion of the glass coatings was found to be excellent such that it was able to withstand moderate impact tests and temperature cycling to over $300^{\circ}C$ without cracking and delamination. The electrostatic clamping pressure generally followed the theoretical voltage-squared curve except at elevated temperatures and higher applied voltages when deviations were observed to occur. The deviation is due to increased leakage current at higher temperature and applied voltage as the electrical resistivity drops.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1988년도 춘계학술대회 논문집
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• pp.46-48
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• 1988

The effect of cold reduction ratio on magnetic properties of 45% Ni-Fe permalloy was studied. To know the relationship between the crystal orientation and the magnetic properties, the pole figure was measured by X-ray diffraction method. In the case of single rolled reduction, the coercive force decreased with cold reduction ratio monotonically, but the maximum permeability, induction and squreness increased drastically. In the case of double rolled reduction (total reduction ratio is 90%), the saturation and residual induction increased slightly with secondary reduction ratio, but the maximum permeability and the coercive force had the maximum and the minimum value at the 50/50% reduction ratio respectively. And strong {100} <100> pole was developed by increasing the cold reduction ratio.

• 한국생산제조학회지
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• 제20권2호
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• pp.145-150
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• 2011

There is problem to reduce the car body weight for improving fuel consumption and $CO_2$ generation. As one of the solution, the multi material car body concept using aluminum alloys and high strength steels is proposed recently. Therefore, new welding processes by which these dissimilar material can be joined in high reliability and productivity are demanded. Laser spot welding was developed for joining of dissimilar metals. In the present work, Laser spot welding of zinc coated steel and aluminum alloy was investigated, and the process parameters were studied. Otherwise, the influences of process parameters on the weldability, the formation of intermetallic compound layer and the mechanical properties have been investigated. When intermetallic compound layer thickness was more than 1mm, specimen was failure in the interface.

• 소성∙가공
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• 제22권6호
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• pp.303-309
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• 2013

Spring-back of MS1470 steel sheets was numerically predicted using a non-linear kinematic hardening material behavior based on the Yoshida-Uemori model. From uniaxial tension and uniaxial tension-compression-tension data as well as the uniaxial tension-unloading-tension data, the parameters of the Yoshida-Uemori model were obtained. For the numerical simulations, the Yoshida-Uemori model was implemented into the commercial finite element program, ABAQUS/Explicit and ABAQUS/Standard using the user-defined material subroutines. The model performance was validated against the measured spring-back from the benchmark problems of NUMISHEET 2008 and NUMISHEET 2011, the 2-D draw bending test and the S-rail forming test, respectively.