• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.2
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• pp.104-109
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• 2010

Lap joint friction stir welding(LFSW) is an relatively new solid state joining process. A6061-T6 aluminium alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength to weight ratio and good corrosion resistance. Test methods used in this paper, lock-in thermography, a phase difference between the defect area and the healthy area indicates the qualitative location and size of the defect. In this paper, the defects detected from the thermal image of mechanical properties for weld were evaluated and compared by the lock-in infrared thermography technique.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.535-541
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• 2020

FCAW is used mainly in the welding of carbon steel and alloy steel because it can be welded in all positions and can obtain excellent quality at sites with variable working conditions. Recently, many studies in Korea have estimated the fatigue strength, residual stress, and deformation, and to develop a fillet welding process. On the other hand, there have been few studies of the mechanical properties based on the strength, macro and magnetic particle test results for fillet welding. This study shows the following results through fillet welding, macro testing and strength testing using SM490A (solid-structure rolled steel) for thick plates using SS400 (rolled steel) for the upper plate and FCAW. The hardness test, macro test and magnetic particle test were then conducted. The hardness tests showed that all result values were smaller than the KS B 0893 standard values of 350Hv. The macro-test showed that each type of welded part was in a normal organic state and that there were no internal errors, bubbles, or impurities on the front of the welded part. Therefore, there were no concerns about lamination. The magnetic particle examination showed no problems.

• Journal of Welding and Joining
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• v.10 no.2
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• pp.1-10
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• 1992

저탄소강은 일반적으로 용접성이 우수하지만 완전한 접합 강도와 용접부에서의 결함을 방지하기 위해서는 많은 주위가 필요하다. 용접부의 기계적 성질은 그 미세구조에 따라 좌우되는데, 이 구조는 모재의 화학조성, 용접 조건 그리고 후열처리에 의하여 결정이 된다. 이와 같이 용융용 접에 의한 저탄소강의 접합부는 저탄소함량으로 응고 균열에 대한 저항이 높다. 그러나 탄소의 함량이 증가하므로서 용접성은 저하하여, 0.3% 이상에서 용접부는 과열, 과냉, 저온 균열과 porosity에 취약하게 된다. 구조용강애 있어서는 용접성에 대한 일반적인 기준이 없으므로 이 러한 재료는 모재와 용접부의 기계적 성질, 고온 및 저온 균열성, 열간 및 냉각가공성등을 고려 하게 된다. 그러나 가장 중요한 것은 용접부의 신뢰도이다. 탄소강과 저합금강에 있어서 용접은 높은 강도를 얻을 수 있어야 하며 접합부에서 모재의 원래의 특성을 유지하여야 하고 결함이 없어야 할 것이다. 이와 같은 결함은 모재의 융접 이하에서 접합을 실시하는 고상접합으로 충 분히 억제할 수가 있다. 고상접합에서는 근본적인 미세조직의 결정화도 피할 수 있으며 고온균 일과 같은 결함의 위험도 배제할 수 있다. 고상접합은 용융용접과는 달리 모재를 용융시키지 않고 고체상태에서 접합을 하는데, 신금속 및 신소재의 개발과 첨단산업의 발달로 고상접합 기 술이 크게 각광을 받고 발전하게 되었다. 이와 같은 접합기술의 발전으로 기존의 용접으로는 접합이 불가한 소재, 용접기술의 적용이 곤란한 복잡한 형상, 복합기능 소재, 고품질 및 고정밀 성이 요구되는 소재등이 접합이 가능하게 되었다. 이러한 접합기술로는 brazing, 확산접합, 마찰 용접 등이 주로 많이 이용되고 있다. Brazing은 융점이 낮은 filler metal이 모재의 사이에서 용 융상태로 유입되어 냉각되면서 접합되는 방식이고 확산접합은 모재의 접합계면에서 원자의 상호 확산으로 접합을 하게 된다. 한편 마찰용접은 계면에서 회전에 의한 마찰열고 접합하는 방식 이다. 본 기술해설에서는 이러한 고상접합 기술을 이용한 철강재료의 접합에 대하여 고찰하도록 하겠다.

• Nuclear Engineering and Technology
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• v.55 no.2
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• pp.575-579
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• 2023

In this work, pure W and W-0.5wt%HfC alloy (WHC05) were fabricated by sintering and hot-rolling following the same processing route. After exposing to a high flux deuterium plasma irradiation with the D⁺ flux to three fluences of 6.00 × 10²⁴, 2.70 × 10²⁵ and 7.02 × 10²⁵ D/m², the evolution of surface morphology, deuterium retention and hardening behaviors in pure W and WHC05 has been studied. The SEM results show the formation of D blisters on the irradiated area, and with the increase of D implantation, the size of these blisters increases from 200 ~ 500 nm (2.70 × 10²⁵ D/m²) to 1 ~ 2 ㎛ (7.02 × 10²⁵ D/m²) in WHC05 and from 1 ~ 2 ㎛ (2.70 × 10²⁵ D/m²) to > 3 ㎛ (7.02 × 10²⁵ D/m²) in pure W, respectively. A higher D retention and obvious hardening are observed in pure W than that of the WHC05 alloy, indicating an improve radiation resistance in WHC05 compared to pure W.

• Journal of Welding and Joining
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• v.34 no.5
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• pp.33-40
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• 2016

The microstructures and the creep rupture properties of dissimilar welds between the Ni-based superalloy Inconel 740H and the non-stabilized austenitic stainless steel TP316H have been characterized. The welds were produced by shielded metal arc (SMA) welding process with the AWS A5.11 Class ENiCrFe-3 filler metal, commonly known as Inconel 182 superalloy. Postweld heat treatment at $760^{\circ}C$ for 4 hours was conducted to form ${\gamma}^{\prime}$ strengthener in Inconel 740H. The austenitic weld metal produced by Inconel 182 had a dendritic microstructure, and grew epitaxially from the both sides of Inconel 740H and TP316H base metals. Since both Inconel 740H and TP316H did not undergo any solid-state transformation during welding process, there were no heat-affected-zone (HAZ) sub-regions and the coarsoned grains near the weld interface were limited to a narrow region. The hardness of Inconel 182 weld metal was ~220 Hv. The gradual hardness decrease was detected at HAZ of TP316H, and the TP316H base metal displayed the lowest hardness value (~180 Hv) whilst the Inconel 740H showed the highest hardness value (~400 Hv). Fracture after creep occurred at the center of weld metal, regardless of creep condition. It was found that during creep the cracks initiated and propagated along interdendritic regions and grain boundaries at which Laves particles enriched in Nb, Si and Cr were present. The appropriate design of weld metal was discussed to suppress the creep-induced cracking of the present dissimilar weld.

• Journal of the Korean Society for Heat Treatment
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• v.11 no.3
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• pp.168-176
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• 1998

The mechanical properties of mechanically alloyed Al-4wt%Mg alloys dispersed with $MgAl_2O_4$ dispersoilds at room and elevated temperatures were investigated. The powders in steady state during mechanical alloying consisted of Mg-supersatu rated Al solid solution and $Al_4C_3$ which resulted from the reaction of Al with C in process control agent (methanol). The hot-extruded materials consisted of uniformly dispersed fine $MgAl_2O_4$, ${\gamma}-Al_2O_3$, $Al_2O_3$ and matrix with extremly fine substructure. Tensile specimens prepared from the extruded bars were tested at room temperature to $400^{\circ}C$ under different strain rates. The tensile strength of alloys at room temperature ranged from 500 to 594MPa. At elevated temperatures, the tensile strengths and elongations decreased with increasing temperature. Adding 3% $MgAl_2O_4$ to Al-4wt%Mg increased the tensile strength of 50MPa at rowan temperature and 20MPa at $400^{\circ}C$.

• Nuclear Engineering and Technology
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• v.50 no.8
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• pp.1330-1338
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• 2018

High-density UMo/Zr monolithic nuclear fuel plates have a promising application prospect in high flux research and test reactors. The solid state welding method called co-rolling is used for their fabrication. Hot co-rolling simulations for the composite blanks of UMo/Zr monolithic nuclear fuel plates are performed. The effects of coupon sizes and mechanical property parameters on the contact pressures between the to-be-bonded surfaces are investigated and analyzed. The numerical simulation results indicate that 1) the maximum contact pressures between the fuel coupon and the Zircaloy cover exist near the central line along the plate length direction; as a whole the contact pressures decrease toward the edges in the plate width direction; and lower contact pressures appear at a large zone near the coupon corner, where de-bonding is easy to take place in the in-pile irradiation environments; 2) the maximum contact pressures between the fuel coupon and the Zircaloy parts increase with the initial coupon thickness; after reaching a certain thickness value, the contact pressures hardly change, which was mainly induced by the complex deformation mechanism and special mechanical constitutive relation of fuel coupon; 3) softer fuel coupon will result in lower contact pressures and form interfaces being more out-of-flatness.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.48 no.3
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• pp.189-196
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• 2022

Plasma refers to an ionized gas that is often referred to as "the fourth phase of matter", following solid, liquid, and gas. Plasma has traditionally been utilized for industrial applications such as welding and neon signs, but its promise in biomedical fields such as cancer treatment and dermatology has lately been recognized. Indeed, due to its beneficial effects in promoting collagen production, improving skin tone, and eliminating harmful bacteria in the skin, plasma treatment constitutes an important target for dermatological research. In this study, a plasma device for cosmetic manufacturing based on nitrogen, the main component of the atmosphere, was designed and assembled. Moreover, nitric oxide (NO) was selected since is easier to follow and evaluate than other nitrogen plasma active species, and its contents were measured to perform a quantitative and qualitative evaluation of plasma. First, an injection method, using different proximities labeled "sinking" and "non sinking" treatments, was performed to test the most efficient plasma treatment method. As a result, it was observed that the formulation obtained by a non sinking treatment was more effective. Furthermore, toner and ampoule were selected as cosmetics formulations, and the characteristics of the formulation and changes in the injected plasma state were observed. In both formulations, the successful injection of NO plasma was 2 times higher in toner formulation than ampoule formulation, and it gradually decreased with time, having dissipated after a week. It was confirmed that the nitrogen plasma used did not affect the stability of the toner and ampoule formulations at low temperature (4 ℃), room temperature (25 ℃), and high temperature (37 ℃ and 50 ℃) conditions. The results of this study demonstrate the potential of plasma cosmetics and highlight the importance of securing the stability of the injected plasma.