• 한국자기학회지
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• 제3권3호
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• pp.201-207
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• 1993

$Pr_{15}Fe_{77}B_{8}$ 조성의 합금을 Ar분위기에서 유도용해로를 이용하여 주조하 였다. 이 합금을 석영관에 넣어 고주파 유도로를 이용하여 용해한 후 0.6 nm의 분출구를 통해 회전하는 Cu wheel위에 분사하여 비본형태로 제조하였다. 이 리본을 열간변형하여 결정방향성을 주었는데 이를 위 해 먼저 $680^{\circ}C$에서 $21.8\;kg/mm^{2}$의 압력으로 hot-press하여 92%의 densification을 갖는 시편을 얻을 수 있었다. 이 시편을 다양한 조건하에서 die-upset을 행하였다. 변형율이 높을 수록 $_{i}H_{c}$는 저하되었으나, $B_{r}$은 현저하게 증가되었으며, XRD 분석 결과(006)면에서의 회절강도가 증가되었다. 따라서 압축방향으로 자화용이축이 형성되었음을 알 수 있었다. Die-upset시의 변형속도가 빠를 수록 $_{i}H_{c}$는 증가되었으나, $B_{r}$은 감소되었다. 가공온도에 따른 $B_{r}$의 변화는 $750^{\circ}C$ 까지 상승한 후 감소되었다. 이 조성의 $4{\pi}M_{s}$는 11.8 kG였고 $750^{\circ}C$에서 0.05 mm/sec의 가공속도로 변형률 0.8로 die-upset한 경우에는 $B_{r}$이 11.0 kG로 우수한 자기이방성을 가지고 있으나, die-upset후에 $_{i}H_{c}$가 낮은 문제점이 있다.

• Design & Manufacturing
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• 제2권5호
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• pp.30-33
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• 2008

Injection Molding is the most effective process for mass production of plastic parts. The injection molding process is composed with several steps such as Filling, Packing, Holding, Cooling, Ejecting. Among them, filling and packing process should be considered carefully to improve accuracy of dimension, surface quality of plastic parts. Usually the quality above-mentioned is managed with weight of part after molding on the field. In this paper, a series of experiment for molding automotive front bumper was conducted with cavitity temperature sensor to optimize switch-over time(V-P switching), hot runner vale gate sequence time during filling and packing step for the purpose of uniform quality, weight at every molding. As a result, it was found that it is effective method to use temperature sensor in injection molding for quality control of plastic molding.

• Journal of Biosystems Engineering
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• 제35권6호
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• pp.408-412
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• 2010

Rheological properties of cereals such as rye are great important for the design of die for extrusion and the development of models for extrusion process. Therefore, this study was carried out to analyze the rheological properties according to moisture content of rye flour and extrusion temperature. Rheological properties of rye flour were investigated by using a capillary rheometer for moisture content of three levels (30, 35, 40%) and extrusion temperature of three levels (120, 130, $140^{\circ}C$). Determination coefficients for the relationship between apparent shear stress ($\tau_{ap}$) and apparent shear velocity ($\gamma_{ap}$) were relatively high in the range of 0.973 ~ 0.997 under each extrusion condition. The values of consistency index (K) was decreased with increasing moisture content and extrusion temperature. However, the value of flow behavior index (n) presented the highest value at moisture content of 35%, but it was not affected by extrusion temperature.

• Journal of the Korean Wood Science and Technology
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• 제45권6호
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• pp.703-719
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• 2017

Miscanthus had a higher lignin content (19.5 wt%) and carbohydrate (67.6 wt%) than other herbaceous crops, resulting in higher pellet strength and positive effect on combustion. However, miscanthus also contains a high amount of hydrophobic waxes on its outer surface, cuticula, which limits the pellet quality. The glass transition of lignin and cuticula were related to forming inter-particle bonding, which determined mechanical properties of pellet. To determine the effects of surface waxes, both on the pelletizing process and the pellet strength were compared with raw and extracted samples through solvent extraction. In addition, to clarify the relationship between pellet process parameters and bonding mechanisms, the particle size and temperature are varied while maintaining the moisture content of the materials and the die pressure at constant values. Furthermore, kraft lignin was employed to determine the effect of kraft lignin as an additive in the pellets. As results, the removal of cuticula through ethanol extractions improved the mechanical properties of the pellet by the formation of strong inter-particle interactions. Interestingly, the presence of lignin in miscanthus improves its mechanical properties and decreases friction against the inner die at temperatures above the glass transition temperature ($T_g$) of lignin. Consequently, it could found that the use of kraft lignin as an additive in pellet reduced friction in the inner die upon reaching its glass transition temperature.

• 한국기계가공학회지
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• 제13권1호
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• pp.52-58
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• 2014

This study consists of two parts. The first discusses the development of a single production forming machine which was reported in earlier papers. The second outlines the development of a multi-production forming machine, which consists primarily of a film feeding unit, an unwinding unit, and a heating block unit. The heating block unit of the multi-production forming machine has 30 members per die. An analysis of the stress deformation and temperature deviation of this machine is carried out using ANSYS Workbench and CFX-11 under the design conditions. According to this analysis, the maximum deflection in the Z-direction is $0.05104{\mu}m$ and the maximum temperature deviation is $0.7^{\circ}C$ when the temperature of the heating block unit is $175^{\circ}C$. It was also found that these values are structurally safe. The advantage of the developed multi-production forming machine is demonstrated to be in its offering of a proper voice test.

• Journal of Welding and Joining
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• 제16권4호
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• pp.92-97
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• 1998

Because of the low melting temperature of solder, each temperature cycle initiates an irrecoverable creep deformation at the solder interconnection which connects the package body with the PCB. The crack starts and propagates from the position where the creep deformation is maximized. This work has tried to compare and analyze the thermal fatigue life of solder interconnection which is affected by the lead material, the size of die pad, chip thickness, and interface delamination of 48-Pin TSOP under the temperature cycle ($0^{\circ}C$~1$25^{\circ}C$). The crack initiation position and thermal fatigue life which are calculated by using FEA method are well matched with the results of experiments. The thermal Fatigue life of copper lead frame is extended around 3.6 times longer than that of alloy 42 lead frame. It is maximized when the chip size is matched with the length of the lead. It tends to be extended as the thickness of chip got thinner. As the interfacial delamination between die pad and EMC is increased, the thermal fatigue life tends to decrease in the beginning of delamination, and increase after the delamination grew after 45% of the length of die pad.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.190-194
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• 2007

The forging process design and microstructure evolution for gas turbine disk of a Waspaloy is investigated in this study. Parameters related to deformation are die and preform geometry, and forging temperature of die and workpiece. Die and preform design are considered to reduce the forging load, and to avoid the forging defects. Blocker and finisher dies for multistage forging are designed and the initial billet geometry is determined. The control of hot forging parameters such as strain, strain rate and temperature also is important because the microstructure change in hot working affects the mechanical properties. The dynamic recrystallization evolution has been studied in the temperature range 900-$1200^{\circ}C$ and strain rate range 0.01-1.0s-1 using hot compression tests. Modeling equations are required represent the flow curve, recrystallized grain size, recrystallized volume fraction by various tests. In this study, we used to thermo-viscoplastic finite element modeling equation of DEFORM-2D to predict the microstructure change evolution during thermo-mechanical processing. The microstructure is updated during the entire thermal and deformation processes in forging.

• 한국식품영양과학회지
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• 제34권4호
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• pp.544-548
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• 2005

사출구 온도$(110,\;120^{\circ}C)$와 사출구멍 직경(1.0, 2.0, 3.0 mm)을 달리하여 제조한 압출성형 인삼의 추출패턴, 추출속 도상수, 추출수율 및 조사포닌 함량의 변화를 분석하였다. 인삼 추출물의 갈색도와 적색도는 유효성분의 지표가 되므로 인삼의 추출패턴과 추출속도상수를 알아보기 위해 침출시간(1 min에서 50 min)에 따른 갈색도와 적색도를 구하였다. 갈색도와 적색도는 추출시간 1분에서 50분까지 증가하는 경향을 보였다. 또한 갈색도와 적색도 추출속도상수는 사출구온도가 $110^{\circ}C$에서 $120^{\circ}C$로 증가함에 따라 증가하였으며 사출구 온도 $110^{\circ}C$, 사출구멍 직경 2.0 mm에서 추출속도상수가 가장 낮았다. 원료 백삼분말의 추출수율은 $21\%$를 나타냈으며 백삼 압출성형물의 추출수율은 약 $40\%$를 보여 압출성형공정을 통해 추출수율이 약 2배 증가하였다. 사출구 온도가 $110^{\circ}C$에서 $120^{\circ}C$로 증가함에 따라 추출수율은 증가하였으며 사출구멍 직경이 1.0 mm에서 3.0 mm로 증가함에 따라 증가하는 경향을 보였다. 본 실험에서 사출구온도 $120^{\circ}C$와 직경 3.0 mm의 사출구멍 1개 에서 추출수율이 가장 높았다. 사출구 온도에 따른 조사포닌 함량은 직경 3.0 mm인 사출구멍 1개인 경우, 사출구 온도 $110^{\circ}C$와 $120^{\circ}C$에서 각각 높은 값을 나타내었다. 압출성형 인삼의 추출율과 추출 속도의 증가는 압출성형공정을 통한 기공의 형성과 전단력에 의한 세포벽의 파괴에 기인한 것으로 판단되었다.\%$로 가장 많이 함유되어 있었다. 비타민 A는 올리브 잎 5.10 mg/100 g, 월계수 잎 6.49 mg/100 g로 나타났고 비타민 C는 올리브 잎 36.64 mg/100 g, 월계수 잎 13.86 mg/100 g로 나타났다. 올리브 잎과 월계수 잎 모두에서 비타민 $B_1,\;B_2$, niacin이 소량 함유되어 있었으며 $B_6$과 $B_{12}$은 검출되지 않았다.한다면 더욱 명확해질 수 있으리라 생각된다. 1일 30 mg이라는 양은 우리들이 섭취할 때는 80 mg(1포)에 해당하는 양이다. 따라서 사람에 따라 차이가 있을 수 있으나 일반적으로 꾸준히 1일 1포 이상의 섭취는 체내 중금속 농도를 감소시키는데 도움을 줄 수 있으리라 판단된다.으나(p<0.05) DPAn-6와 DHA의 합에는 변화가 없었다. 따라서 뇌 성숙 발달 과정동안 n-3 지방산 결핍은 뇌의 DHA의 결핍을 초래하고 이러한 비정상적인 조건에서 DPAn-6의 증가를 유발하였으며 이러한 지방산 조성의 변화와 공간과 후각에 기초를 하는 기억 학습 능력 저하의 관련성에 대해서는 앞으로 연구가 진행되어져야 할 것으로 사료되어진다.저해율이 $70\%$ 이상인 해조류는 파래, 미역, 다시마, 톳이었고, 김은 $68\%$로 나타나 해조류 간에 차이는 적었다. 이상에서 Ames test와 MTT assay를 통해 해조류 에탄올 추출물의 항돌연변이 효과와 암세포 성장억제 효과를 검색한 결과, 톳, 파래와 다시마는 항돌연변이 효과 및 암세포 성장억제 효과가 우수한 것으로 나타났고, 암세포에 대한 항암 효과는 각 시료마다 정도의 차이는 있으나 5종의 해조류 모두 암세포 증식을 억제하는 것으로 나타났다. 이 결과는 해조류가 개발 가능한 고부가가치의 기능성식품 소재임을 확인한 것으로서, 이를 위해서는 갈조류,

• 소성∙가공
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• 제10권2호
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• pp.101-110
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• 2001

The thermal problem of press work is classified into two cases. First, the temperature of forming die passively rises due to the heating effect of plastic deformation. The warm forming is the second case in which the external heating is applied to the die and blank holder. So, the purpose of this study is to provide database for the forming characteristics at various temperature conditions. In this study, the tensile test was carried out for the commercial steel sheets such as SCPI and SCP3C with the thickness of 0.7mm and 1.4mm respectively. The tensile strength, total elongation, Lankford value and the flow curve have been obtained at the temperature of $25^{\circ}C$, $50^{\circ}C$, $100^{\circ}C$, $150^{\circ}C$, $200^{\circ}C$, $250^{\circ}C$ and $300^{\circ}C$, respectively. From the results, we can see that both the tensile strength and total elongation decrease as the temperature increases. In the light of anisotropy, the effect of thickness is dominant than the material specs. For the temperature dependency of flow curves, there are only small differences for the work-hardening exponent, and the strength intensity decreases monotonically as temperature increases. The present results we useful as input data for the analysis of sheet metal forming processes with the various temperature conditions.

• 한국생산제조학회지
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• 제9권3호
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• pp.9-17
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• 2000

The use of ceramic inserts in steel forging tools offers significant technical and economic advantages over other materi-als of manufacture. These potential benefits can however only be realised by optimal design of the tools so that the ceramic insert are not subjected to stresses that led to their premature failure. In this paper the data on loading of the tools is determined from a commercial forging simulation package as the contact stress distribution on the die-workpiece interface and as temperature distributions in the die. This data can be processed as load input data for a finite-element die-stress analysis. Process simulation and stress analysis are thus combined during the design and a data exchange program has been developed that enables optimal design of the dies taking into account the elastic detections generated in shrink fitting the die inserts and that caused by the stresses generated in the forging process. The stress analysis of the dies is used to determine the stress conditions on the ceramic insert by considering contact and interference effects under both mechanical and thermal loads. Simulation results have been validated as a result of experimental investigation. Laboratory tests on ceramic insert dies have verified the superior performance of the Zirconia and Silicon Nitride ceramic insert in order to prolong maintenance life.