• 한국표면공학회:학술대회논문집
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• 한국표면공학회 1998년도 춘계학술발표회 초록집
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• pp.82-82
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• 1998

• 동력기계공학회지
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• 제18권4호
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• pp.85-90
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• 2014

In this paper, the transient thermal and residual stress analysis of the welding of 9% Ni steel plates using the FEA software ABAQUS are presented. The 9% Ni steel plates are welded manually with welding consumables of 70% Ni based Inconel type super-alloys (YAWATA WELD B (M)), producing a multi-pass/multi-layer butt weld. For these materials, temperature dependant mechanical and thermal material properties are used in the analysis. The back gouging is considered in welding process simulation. The FE thermal results are validated by comparing the real fusion profile and heat affected zone (HAZ). In addition, the continuous indentation test was conducted to measure the strength of base metal, HAZ and weld metal.

• 한국자기학회지
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• 제23권1호
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• pp.12-17
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• 2013

금속 분말 니켈(Ni)을 HCl용액에 용해시킨 후 $H_3BO_3$, KOH을 첨가하여 Chloride 도금용액을 제조 후 Ni plate 기판에 도금하였다. 도금두께는 $3{\mu}m$로 일정하게 유지하였다. 전류밀도를 $1{\sim}30mA/cm^2$ 변화를 준 결과 전류밀도를 증가시킬수록 Ni 후막표면이 거칠어졌다. $25mA/cm^2$와 $30mA/cm^2$에서는 균열된 표면형상을 관찰하였다. 또한 XRD patterns 변화를 관찰한 결과 전류밀도가 증가할수록 FCC(111)과 FCC(220) 및 FCC(311)상의 강도는 증가한 반면 FCC(200)상의 강도는 감소하는 것을 관찰하였다. 전기도금된 Ni의 수평 및 수직 자화 값을 측정하였는데 기판에 의한 수평자화 값이 크게 나왔고, 코팅층 두께가 증가할수록 수직자화 값이 커지는 것을 확인하였다.

• Steel and Composite Structures
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• 제24권6호
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• pp.753-765
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• 2017

This paper aims to investigate the strength degradation of reinforced concrete piers wrapped with steel plates which corrode at the pier base by employing a three dimensional elasto-plastic finite element formulation. The prediction accuracy of the employed finite element analysis method is firstly verified by comparing the analytical results with test results. Then, a series of parametric studies is carried out to investigate the effects of steel plate's corrosion position along width direction, corrosion depth along plate thickness, corrosion range along width direction, and steel plate-concrete bonding degradation on the strength of the piers. It is observed that the strength degradation of the piers is closely related to steel plate's corrosion position, corrosion depth and corrosion range in the case of local corrosion on the webs. In contrast, when the base of flanges corrodes, the strength degradation of the piers is only related to steel plate's corrosion depth and corrosion range, and the influence of corrosion position on the strength degradation is very gentle. Furthermore, the strength of the piers decreases with the degradation of steel plate-concrete bonding behavior. Finally, the maximum strength of the piers obtained from numerical analysis corresponding to different bonding behavior is compared with theoretical results within an accepted error.

• 한국레이저가공학회지
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• 제3권1호
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• pp.29-37
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• 2000

For a development purpose of thick metal / metal Graded-Boundary Materials(GBM), a basic research on the fabrication of Ni-Cr/steel GBM was carried out by a laser beam and its mechanical properties and thermal characteristics were investigated. In order to produce a compositionally graded boundary region between substrate steel and added Ni-Cr alloy, a series of surface alloying treatments was performed with a high power CO$_2$ laser beam. Ni-Cr sheet was placed on a low carbon steel plate(0.18%C), and then a CO$_2$ laser beam was irradiated on the surface to produce a homogeneous alloyed layer. On this first surface-alloyed layer, another Ni-Cr sheet was placed and then the CO$_2$ laser beam was irradiated again to produce second surface-alloyed layer. Sequential repetitions of laser surface alloying treatment 4 times resulted in a graded-boundary region with the thickness of about 1.4mm. Simultaneous concentration profiles of different kinds of alloying elements(Ni and Cr) showed from 42%Ni, 45%Cr and 13%Fe on surface region to 0%Ni, 0%Cr and 99%Fe in substrate region. Also a thermal conductivity gradient resulted in graded-region and its value changed from 0.03㎈/cm s$\^{C}$ in surface region to 0.1㎈/cm s$\^{C}$ in substrate region. Microstructural observation showed that any visible root porosities and solidification shrinkage cracks were not formed in graded region between alloyed layer and substrate region during rapid cooling.

• 한국초전도ㆍ저온공학회논문지
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• 제18권1호
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• pp.37-40
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• 2016

We have investigated the addition effect of NiO magnetic nanoparticles on crystal structure, microstructure as well as superconducting properties of $MgB_2$. NiO-added $MgB_2$ samples were prepared by the solid-state reaction method. The superconducting transition temperature ($T_c$) of 37.91 K was obtained for pure $MgB_2$, and $T_c$ was found to decrease systematically on increasing the addition level of NiO. X-ray diffraction (XRD) analysis revealed that no substitution of Ni for Mg in the lattice of $MgB_2$ was occurred. The microstructural analysis shows that the pure $MgB_2$ sample consists of plate shape $MgB_2$ grains, and the grains get refined to smaller size with the addition of NiO nanoparticles. At 5 K, high values of critical current density ($J_c$) were obtained for small amount NiO-added $MgB_2$ samples as compared to pure sample. The enhancement in $J_c$ could be attributed to the refinement of $MgB_2$ grains which leads to high density of grain boundaries in NiO-added $MgB_2$ samples.

• 한국주조공학회지
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• 제33권5호
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• pp.193-203
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• 2013

The Ni-base superalloy CM247LC was directionally solidified (DS) using the Bridgman-type furnace to understand the effect of the chill plate on the microstructural evolution, such as dendrite arm spacing, microporosity, and MC-type carbide. The DS process was also modeled by the PROCAST to predict the solidification rate, thermal gradient, and resultant cooling rate in the entire length of the DS specimen. Due to the quenching effects of chill plate, four distinct areas were found to form in the specimen, in which the solidification rate was changed, during DS at a given withdrawal rate of 0.083 mm/s. Among the microstructural features investigated, the dendrite arm spacings and average size of the MC-type carbide near the chill plate were found to be influenced by the quenching effect of the chill plate. However, no significant influence was found on the size and volume fraction of microporosity, and the volume fraction of the MC-type carbide. The relationship between the microstructural features and the solidification variables was also analyzed and discussed on the basis of a combination of experimental and modeling results.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.260-263
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• 2001

Mechanical properties have been accepted to be major factor to improve wear resistance. The effect of mechanical properties on wear resistance of 0.27C-0.70Ni-1.42Cr-0.20Mo steel was studied under various test conditions. It is clear that yield strength, tensile strength, impact value, and hardness are strongly related each other. Wear resistance tests as pin on plate type and dry sand / rubber wheel type proved to be that wear depends on mechanical properties. Microstructures were also observed to make clear the wear properties. At quenching and low temperature tempering, the specimen has a good wear resistance.

• 한국표면공학회지
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• 제32권6호
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• pp.686-694
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• 1999

Insoluble anodes of the Ta/Ir mixed metal oxide for electrodeposition of Ni-W alloy in ammoniacal citrate bath were prepared by thermal decomposition method. Ti plate was etched in boiling oxalic acid solution and coated with ethanol solution of $TaCl_{5}$ and $IrCl_4$ mixed in a fixed ratio, followed by drying and treating at various temperatures. The coating layer of these insoluble anode was characterized by SEM, EDX, XRD and DSC. The decomposition rate of citric acid in plating bath was determined by measuring the $CO_2$ gas evolved at the anodes with Gas Chromatography. Evolution of $CO_2$ gas from Ta/Ir oxide anodes decreased about 5% compared with that of Pt. The $CO_2$ gas evolution was increased with the amount of Ir-oxide in the coatings. The coatings which have more than 40% ratio of Ta content and heat-treated at the temperature higher than $400^{\circ}C$ showed better efficiency

• E2M - 전기 전자와 첨단 소재
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• 제8권6호
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• pp.768-773
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• 1995

We describe a manufacturing method and characteristics on components of molten carbonate fuel cell. Cr, Al, AI$_{2}$O$_{3}$, Co, MgO powder were mixed with Ni powder for anode components and NiO was used for cathode electrode. The electrolyte plate consisted of LiAIO$_{2}$ and carbonate (Li$_{2}$CO$_{3}$/K$_{2}$CO$_{3}$=62/38) and these three were manufactured by doctor-blade method. As a result, open circuit voltage was 1.05[VI at Ni-10Cr anode and porosity was above 60[%].