• 소성∙가공
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• 제16권4호
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• pp.229-233
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• 2007

The present work focuses on the prediction of birefringence in injection-molded part and its improvement by rapid mold heating. To calculate birefringence, flow-induced residual stress is computed through a fully three-dimensional injection molding analysis. Then the stress-optical law is applied from which the order of birefringence can be evaluated and visualized. The birefringence patterns are predicted for a rectangular plate with a variation of mold temperature, which shows that the amount of molecular orientation and birefringence level decreases with an increase of mold temperature. The effect of mold temperature on the order of birefringence is also studied for a thin-walled rectangular strip, and the relevant results are compared with experimental measurements. Both predicted and experimental patterns of birefringence are in agreements on the observation that the birefringence level diminishes significantly when the mold temperature is raised over the glass transition temperature.

• 한국주조공학회지
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• 제21권4호
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• pp.246-252
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• 2001

Variation in the microstructure of Mg-5%Al semi-solid slurry during isothermal heating was investigated in relation to initial microstructure, holding time, and holding temperature. Specimens with three different initial microstructures were isothermally heated. Dendritic structure in as-cast ingot was decomposed into solid globules in the semi-solid slurry during isothermal holding, while in the recrystallized specimens prepared by extrusion or rolling the size of solid particles was continuously increased during the heating. Effects of mold temperature and liquid fraction of slurry on the mold filling ability were also studied. Very thin section (0.4 mm) could be successfully filled up to 50 mm by 60% liquid slurry when the mold was heated to $600^{\circ}C$.

• Journal of Welding and Joining
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• 제26권4호
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• pp.66-72
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• 2008

Because of high intensity and easy controllability of the heat source, high frequency induction heating has been concerned and studied for the steel forming process in the ship building industry. However, the heating and forming characteristics have to be further properly modelled and analyzed for the process to be utilized with its optimal working parameters. In this study, a modelling with thermo-elasto-plastic analysis is performed using the FEM to study heat flow and deformation of the steel plate during the forming process with the electro-magnetic induction heating. The numerical model is then used to study the effect of the inductor shape on the magnitude of angular deformation of the plate during the forming process. It is revealed that the square shape of inductor induces the largest deformation among the rectangular inductors.

• 한국산학기술학회논문지
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• 제8권6호
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• pp.1313-1318
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• 2007

다양한 곡률반경의 연속에 의하여 살 두께 차가 큰 jar50ml의 성형가공시간 단축과 품질향상을 위하여 금형을 급속 냉각시키면 void, 후로우 및 변형 등의 불량이 발생하게 된다. 제품내측과 외측의 온도조절을 충분히 할 수 있는 캐비티부와 코아부에 나선형 냉각회로 구조와 가열과 냉각을 자동 제어할 수 있는 시스템을 Jar금형에 적용함으로 우수한 품질과 생산성향상의 효과를 얻을 수 있다.

• 동력기계공학회지
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• 제9권3호
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• pp.66-70
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• 2005

Structural components for aerospace, electronics and automobile industry are the main applications for magnesium alloys due to their lightweight and high specific strength. The adoption of magnesium alloys in sheet forming processes is still limited, due to their low formability at room temperature caused by the hexagonal crystal structure. In this paper, the authors aim to improve the formability of AZ31 magnesium alloy. For this, experiment and finite element analysis on used warm deep drawing process with a local heating and cooling technique were done. Both die and blank holder were heated at various warm temperature while the punch was kept at room temperature by cooling water.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.385-388
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• 2005

The use of magnesium alloys meets the need of reducing weight of componests(especially in automotive and aerospace industry) keeping unmodified their mechanical properties. The adoption of magnesium alloys in sheet forming processes is still limited, due to their low formability at room temperature caused by the hexagonal crystal structure. In this study, the authors aim to understand the process condition which can lead to a successful improvement in the formability of a magnesium alloy(AZ31). Experiment and simulations of deep drawing were doned at various warm temperature for the blank and tool(holde and die)while the punch was kept at room temperature by cooling wale. in order to confirm that the deep drawing performance of magnesium alloy can be considerably enhanced with using the local heating and cooling technique.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 금형가공,미세가공,플라스틱가공 공동 심포지엄
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• pp.9-12
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• 2005

The rapid thermal response (RTR) molding is a novel process developed to raise the temperature of mold surface rapidly to the polymer melt temperature prior to the injection stage and then cool rapidly to the ejection temperature. The resulting filling process is achieved inside a hot mold cavity by prohibiting formation of frozen layer so as to enable thin wall injection molding without filing difficulty. The present work covers flow simulation of thin wall injection molding using the RTR molding process. In order to take into account the effects of thermal boundary conditions of the RTR mold, coupled analysis with transient heat transfer simulation is suggested and compared with conventional isothermal analysis. The proposed coupled simulation approach based on solid elements provides reliable thin wall flow estimation fur both the conventional molding and the RTR molding processes

• 소성∙가공
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• 제31권2호
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• pp.96-102
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• 2022

The multi-point dieless forming technology is one of flexible forming technologies that can form 3D curved surfaces of various shapes utilizing a lot of punch arrangements. A new technology that can simultaneously apply high-temperature forming and flexible forming technology by fusing local heating effect to such multi-point dieless forming technology was proposed in the present study. A simple local heating multi-point dieless forming apparatus was fabricated to confirm the applicability of this new technology. This equipment was designed to be used as a heat source by inserting heating cartridges in the head of the multi-point punch. Cartridges were used for all individual punches. Using the manufactured equipment, the time to raise the temperature to the target temperature and the surface temperature of the punch head part in contact with the plate were measured. In addition, forming experiments were carried out according to sheet material temperature (100 ℃, 200 ℃, and 300 ℃) to obtain forming results for each condition. The applicability and feasibility of this technology were confirmed through experimental results.

• 한국식품영양과학회지
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• 제39권6호
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• pp.843-852
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• 2010

옥수수를 이용한 고품질의 가공식품을 개발하기 위한 연구의 일환으로 옥수수의 품종별 및 가열처리에 따른 기능성 폴리페놀화합물인 hydroxycinnamic acid derivatives(HADs) 및 안토시아닌 색소의 함량 변화를 조사하였다. 국내산 3가지 옥수수 품종(찰옥수수, 감미옥수수 및 사료용 옥수수)의 일반성분 함량을 측정한 결과, 수분함량은 4.13~10.07%, 무질소화합물 65.57~81.75%, 단백질 6.51~15.15%, 지방 3.16~12.35%, 섬유소 2.09~7.81%, 회분 1.40~1.96% 범위로, 찰옥수수의 일반성분의 함량은 비슷하였으나 감미종 옥수수는 찰옥수수보다 단백질과 지방 함량이 높은 반면, 당 함량은 낮았으며, 특히 감미종 중 감미옥 품종은 지방과 섬유소 함량이 옥수수 품종 중 가장 높은 함량을 나타내었고, 사료용 옥수수는 단백질 및 지방 함량이 매우 낮았으며, 특히 단백질 함량은 옥수수 품종 중 가장 낮았다. 옥수수 품종 중 찰옥수수는 5가지 HADs 함량이 골고루 분포하고 있는 반면, 사료용 옥수수는 2가지 FCAs의 함량은 낮은 반면, 3가지 PCs 함량이 가장 높았으며, 특히 P3394 품종이 가장 높았다. 감미 옥수수는 찰옥수수보다 FCAs의 함량은 대체로 높은 반면, PCs는 사료용보다 적어 대체로 찰옥수수와 사료용 옥수수의 중간 정도의 HADs 함량을 나타내었다. 찰옥수수 품종 중 박사찰옥수수의 총 안토시아닌 색소 함량은 2.03 mg/g(건물중), 알록이찰옥수수는 3.43 mg/g, 그리고 흑찰옥수수의 함량은 4.35 mg/g으로서 흑미백찰옥수수의 총 안토시아닌 색소 함량이 가장 높았다. 가열처리에 따라 흑찰옥수수의 2가지 FCAs는 다소 증가한 반면, 3가지 PCs는 거의 변화가 없었으며, 가열처리 중 볶음, retort 및 팽화처리는 FCAs를 증가시켰고 특히 팽화처리 시 크게 증가하였다. 가열처리에 따른 흑찰옥수수의 총 안토시아닌 색소 함량을 측정한 결과, 대조구 함량은 4.35 mg/g이었으나 retort 처리(4.45 mg/g) 경우를 제외하고 대부분 가열처리에 따라 함량이 감소하는 경향을 나타내었으며, 특히 팽화처리 경우 안토시아닌 함량이 크게 감소하여 거의 소실되었다. 흑미백찰옥수수로부터 주된 안토시아닌 색소인 pelargonidin 3-glucoside(P3G)를 분리 및 동정하였으며, 가열처리에 따른 P3G의 함량 변화를 측정한 결과, retort 처리 경우 함량이 다소 증가한(20.03 mg%) 반면, 그 외 볶음, 마이크로파 및 압출성형 처리에 의해 대체로 감소하였으며, 특히 팽화처리 경우 색소가 거의 소실되었다. 이러한 결과를 종합해 볼 때 옥수수의 기능성성분인 HADs 및 안토시아닌 색소 함량은 옥수수 품종 및 가공처리에 따라 다소 달라짐을 알 수 있었으며, 특히 옥수수 품종 중 항암, 항고혈압, 항당뇨 및 항노화성 FCAs 및 안토시아닌 색소 함량이 높은 흑찰옥수수의 대량 보급과 더불어 고압가열처리(retort)에 의한 고품질의 흑찰옥수수 가공품 개발이 요구된다.

• 한국세라믹학회지
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• 제41권11호
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• pp.797-803
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• 2004

마이크로파 가열장치를 이용하여 마이크로파 조사에 따른 SiC와 MO$_2$ 시료에 대한 발열실험을 수행하였고, 이 실험에서 얻은 발열특성 결과들을 고려하여 $UO_2$+5wt% CeO$_2$ 성형체에 대한 산화소결 실험을 수행하였다. 그리고 마이크로파와 전기로에서 각각 소결된 MO$_2$ 소결체의 특성변화를 비교분석하였다 마이크로파 조사에 따른 MO$_2$시료의 발열온도는 입력전력의 증가에 따라서 급속히 증가하였으며, 출력전력은 주로 보조가열재인 SiC와 MO$_2$ 시료가 마이크로파와 반응하는 정도에 따라서 변하였다. 마이크로파에 의하여 소결된 소결체의 밀도는 전기로에서 동일한 조건으로 소결된 소결체의 밀도보다 약 2% T.D. 낮았다. 소결체의 미세조직은 전기로에서 제조된 소결조직에 비하여 마이크로파에 의해 제조된 소결체의 기공분포가 불규칙적이었으나, 평균결정립 크기는 크게 나타났다.