• 한국분말재료학회지
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• 제21권3호
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• pp.207-214
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• 2014

In this study, nano-scale copper powders were reduction treated in a hydrogen atmosphere at the relatively high temperature of $350^{\circ}C$ in order to eliminate surface oxide layers, which are the main obstacles for fabricating a nano/ultrafine grained bulk parts from the nano-scale powders. The changes in composition and microstructure before and after the hydrogen reduction treatment were evaluated by analyzing X-ray diffraction (XRD) line profile patterns using the convolutional multiple whole profile (CMWP) procedure. In order to confirm the result from the XRD line profile analysis, transmitted electron microscope observations were performed on the specimen of the hydrogen reduction treated powders fabricated using a focused ion beam process. A quasi-statically compacted specimen from the nano-scale powders was produced and Vickers micro-hardness was measured to verify the potential of the powders as the basis for a bulk nano/ultrafine grained material. Although the bonding between particles and the growth in size of the particles occurred, crystallites retained their nano-scale size evaluated using the XRD results. The hardness results demonstrate the usefulness of the powders for a nano/ultrafine grained material, once a good consolidation of powders is achieved.

• 한국식품과학회지
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• 제32권1호
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• pp.225-230
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• 2000

세 가지 시판 어육연제품에 대한 TPA 매개변수들이 여러 압착조건들에 의해 평가되었다. 지름(D)과 높이 (L)의 비율(D/L)이 1, 1.5, 2인 시료가 1.7. 3.3, 6.7 cm/min의 속도로 50%, 65%, 80% 압착되었다. TPA 매개변수인 경도, 응집력, 탄력성, 껌성. 씹힘성이 얻어졌으며 통계분석에 의해 비교 분석되었다. TPA 매개변수는 시료의 단면적으로 나눔으로써 수정되었다. 본 실험결과 TPA 매개변수들은 세 가지에 형태의 어묵 모두에서 D/L과 압착율에 의해 크게 영향을 받으므로 시료의 크기, 변형의 정도 그리고 변형속도 등의 압착 실험조건이 시료간에 크게 차이가 나면 각 시료들의 TPA 매개변수들은 서로 비교될 수 없음을 보여 주었으며, 어육연제품에 대한 TPA 최적 실험 조건들은 D/L = 1.5, 압착율 = 80%, 압착속도 = 1.7-6.7 cm/min로 나타났다.

• Journal of Welding and Joining
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• 제35권3호
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• pp.44-51
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• 2017

In the present study, AA 5083-O plates are joined by friction stir welding technique. A universal milling machine was used to perform the welding process of the work-pieces which were fixed on the proper position by a vice. The joints were friction stir welded by two tools with different pin profiles; cylindrical threaded pin and tapered smooth one at different rotational speed values; 400 rpm and 630 rpm, and different welding speed values; 100 mm/min and 160 mm/min. During FSW of each joint, the temperature was measured by infra-red thermal image camera. The welded joints were inspected by visually as well as by the macro- and microstructure evolutions. Furthermore, the joints were tested for measuring the hardness and the tensile strength to study the effect of changing the FSW parameters on the mechanical properties. The results show that increasing the rotational speed results in increasing the peak temperature, while increasing the welding speed results in decreasing the peak temperature for the same tool pin profile. Defect free welds were obtained at lower rotational speed by the threaded tool profile. Moreover, the threaded tool pin profile gives superior mechanical properties at lower rotational speed.

• 한국가구학회지
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• 제28권2호
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• pp.111-117
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• 2017

Recently, as people's interest in wood has increased, the use of wood as household and landscape decking materials has increased. As the deck material, imported wood such as synthetic wood, Ipe, and Malas was used in addition to the existing preserved wood, but recently deck use has been activated as part of the activation of domestic materials. As an important quality factor in the selection of such decking materials, various durability along with weatherability for long - term use is required for maintenance. Generally used tropical hardwoods have excellent weatherability and durability without additional preservative treatment. However, the domestic larch is a wood species with a higher specific gravity and durability than ordinary conifers. However, it has not yet been used as a deck material due to lack of comparative studies on its characteristics. Therefore, hardness and durability of wood were measured using six specimens of Ipe, Massaranduba, Malas, Douglas-fir, Larch and Torrefied-Larch. Density Profile was used to measure the density, and Brinell hardness test and resistance test against momentary impact were carried out for the test of resistance to static load. Also, The hardness and durability of wood were measured by castor test with resistance test against dynamic load, as well as, nail down test by experiment on surface hardness and durability. As a result of the experiment, the hardness was increased in proportion to the density, and it was confirmed that the imported lumber was harder and durable than the domestic larch.

• 한국산림과학회지
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• 제56권1호
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• pp.66-76
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• 1982

사방시공지(砂防施工地)에 널리 조림(造林)되는 리기다소나무의 근계분포(根系分布)와 토양(土壤)의 견밀도(堅密度)의 관계(関係)를 구명(究明)하고자 표본지(標本地)를 선정(選定) 대표목(代表木)의 경사하측(傾斜下側)에 환상(環状)의 토양단면(土壤斷面)을 만들어 각토층별(各土層別)로 토양경도(土壤硬度)를 산중식(山中式) Soil hardness tester로 측정(測定)하고 수근(樹根) (중세근(中細根))의 분포(分布)를 조사(調査)하여 분포(分布)한바 다음과 같이 요약(要約)할 수 있었다. 1) 토양(土壤)의 견밀도(堅密度)는 토심(土深)이 깊어짐에 따라 점차(漸次) 증가(增加)하여 평균(平均) 지표경도(指標硬度)는 I층(層)에서 14.6mm II층(層)에서 16.2mm, III층(層) 17.2mm, IV층(層)에서는 18.3mm, V층(層)에서는 19.8mm였다. 2) 수근(樹根) (중세근(中細根))은 표층(表層)에 이를수록 많이 분포(分布)하여 토층(土層)이 깊어짐에 따라 그 수(數)가 감소(減少)하여 I층(層) 수근(樹根)의 수(數)를 1(31%)로 할때 II층(層)은 0.84(26%), III층(層)은 0.6(18%), IV층(層)은 0.4(12%), V층(層)도 0.4(13%)이다. 3) 토양(土壤)의 견밀도(堅密度)와 수근(樹根)의 분포(分布)는 음(陰)의 상관관계(相関関係)에 있어 견밀도(堅密度)가 높아지면 이에따라 수근(樹根) 수(數)는 감소(減少)한다. 각(各) 토층별(土層別) 토양(土壤)의 견밀도(堅密度)와 수근분포(樹根分布)의 상관계수(相関係数)는 I층(層)은 -0.3875, II층(層)은 -0.5299, III층(層)은 -0.5573, IV층(層)은 -0.6922, V층(層)은 -0.7325, 전체평균(全体平均)은 -0.9469로서 모두 유의적(有意的)이었다. 4) 리기다소나무의 수근(樹根) (중세근(中細根))의 성장(成長)에 최적합(最適合)한 토양(土壤)의 견밀도(堅密度)는 지표경도(指標硬度)는 12.0~14.9mm로서 이 계급(階級)에 속(屬)하는 지표경도(指標硬度)는 33%이고 수근(樹根)의 분포(分布)는 41.8%이다. 또 지표경도(指標硬度) 20.9mm까지는 82%이나 수근(樹根) 93.2%가 분포(分布)하고 있어 지표경도(指標硬度) 20.9mm이하(以下)까지가 리기다소나무의 수근(樹根)의 생장(生長)에 적합(適合)하다고 사료(思料)된다.

• 한국정밀공학회지
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• 제22권12호
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• pp.124-130
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• 2005

The research on surface modification technology has been advanced to improve the properties of engineering materials. ion implantation is a novel surface modification technology to enhance the mechanical, chemical and electrical properties of substrate's surface using accelerated ions. In this research, nitrogen ions were implanted into aluminum substrates which would be used for mold of rubber materials. The composition of nitrogen ion implanted aluminum alloy and nitrogen ion distribution profile were analyzed by Auger Electron Spectroscopy (AES). To analyze the modified surface, properties such as hardness, friction coefficient, wear resistance, contact angle, and surface roughness were measured. Hardness of ion implanted specimens was higher than that of untreated specimens. Friction coefficient was reduced, and wear resistance was improved. From the experimental results, it can be expected that ion implantation of nitrogen enhances the surface properties of aluminum mold.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.499-504
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• 2002

The microstructural change associated with the hardness profile in friction stir welded, age-hardenable 6005 Al alloy had been evaluated. Frictional heat and plastic flow during friction stir welding created the fine recrystallized grain (Stir Zone, SZ), the elongated and recovered grain (Thermo-Mechanical Affected Zone, TMAZ) in the weld zone. Heat affected zone (HAZ), which could be only identified by hardness test because there is no difference in the grain structure compared with that of the base metal, was formed beside the weld zone. A softened region had been formed near the weld zone during friction stir welding process. The softened region was characterized by the dissolution and coarsening of the strengthening precipitate during the friction stir welding. The sound joints of 6005 Al alloys were successfully formed under a wide range of the friction stir welding conditions.

• 소성∙가공
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• 제16권5호통권95호
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• pp.375-380
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• 2007

The bimetals of home appliances are mainly manufactured by cladding process and these are almost consisted with Cu alloy and Ni alloy. But it is very difficult to clad these alloys, because the brittle $Cu_3O_4$ oxide film formed easily on Cu alloy surface during cladding process. Clad rolling and heat treatment processes were applied for the development of bimetals by using the Ni alloy and the 3 types of Cu alloys. Optical microstructure, micro-hardness, specific resistance, and deflection and line profile of newly processed bimetals specimens were observed and measured in this paper. Inter-diffusion was observed between Cu and Ni element in the interface of heat treated Cu alloy and Ni alloy clad material. The C1220 and Invar36 clad material showed the best property of deflection among the 3 kind of clad materials.

• 한국표면공학회지
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• 제44권5호
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• pp.207-212
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• 2011

In this study, the change in diffusion coefficient and wear characteristic with depth in the carbonitriding layer of SCM415 steel was discussed. To determine the diffusion coefficient, depth profile of carbon was measured from the surface using the Glow Discharge Spectrometer. In otherwise, measurements of carbide fraction, micro vickers hardness of surface and observation of microstructure have been implemented through the SEM image. $Fe_3$(C,N) layer and effective depth were increased as the time for carbonitriding takes longer. According to wear experiment, the results showed that wear resistance was improved by $Fe_3$(C,N) layer and effective depth.

• 소성∙가공
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• 제9권1호
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• pp.43-51
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• 2000

The die wear is one of the main factors affecting product accuracy and die life in hot forging process. It is desired to analyze die wear by developing wear prediction method combined with FE-simulatin and experiment. Lots of researches have been done into the wear analysis of cold forging die, and the results of those researches were successful, but there have been little applications to hot forging die giving successful results. That is because hot forging process has many factors influencing die wear, and there was not accurate in-process data. In this research, change of die surface hardness by thermal softening during the lifetime was obtained by experiment, and hardness distribution of cross section was measured. This wear analysis was applied to hot forging die, and gave comparatively good results compared with actual wear profile.