• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.394-396
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• 2007

In this study, in order to see effect of the blank holding force on the friction behavior in the sheet metal forming, a sheet metal friction tester is designed and manufactured, which can measure friction forces in various forming conditions, such are lubrication, die roughness, drawing speed, radius of die corner, blank holding force, etc., and performed the friction test in which friction coefficients in various blank holding forces and pulling speeds are calculated using Coulomb's friction law. The friction test reveals that friction coefficient decreases maximum 30% as the blank holding force and the drawing speed are increased to 2.5kN and 1500mm/min, respectively.

• 소성∙가공
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• 제20권5호
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• pp.344-349
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• 2011

Variation of contact pressure causes change of friction coefficient, which in turn changes stress distribution in the sheet being formed and final springback. In the present study, U-draw bending experiments were carried out under constant blank holding force(BHF) and different blank sizes, and finite element analysis was conducted with and without considering contact pressure effect on friction. When the BHF was sufficiently high, the degree of springback was different between constant blank holding pressure condition and that with varying blank holding pressure. Finite element analysis considering the influence of contact pressure effect on friction could explain the occurrence of springback.

• 한국주조공학회지
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• 제24권5호
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• pp.290-294
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• 2004

The effect of carbon equivalent on the fading behavior of hypoeutectic ductile cast iron was investigated. The carbon content was slightly increased right after graphite spheroidization treatment and remained almost constant with holding at $1,490^{\circ}C$ after 4 minute. The residual magnesium content was decreased slowly with holding. The empirical equation expressing the relationship between this and holding time was proposed ; $C=C_o-P{\times}t$. The proportionality constant, P, was inversely proportional to carbon content.

• 소성∙가공
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• 제16권5호통권95호
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• pp.381-385
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• 2007

In order to examine the effect of the blank holding force on the friction behavior in the sheet metal forming, a sheet metal friction tester is designed and manufactured, which can measure friction forces in various forming conditions such as lubrication, die roughness, drawing speed, radius of die corner, blank holding force, etc., and the friction tests are performed, in which friction coefficients in various blank holding forces and pulling speeds are calculated using Coulomb's friction law. The friction test reveals that friction coefficient decreases as the blank holding force, the drawing speed and lubricant viscosity increase together or individually.

• 소성∙가공
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• 제18권7호
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• pp.531-537
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• 2009

The effect of blank holding force on thickness variation in simultaneous sheet forming with rectangular shape and circular has been demonstrated. Because has investigated an effect on formability of magnesium sheet, in this paper, the effect of punch radius on formability have been thinning, various crack phenomena and forming velocity. By simultaneously forming process with circular and rectangular shape, the data of simultaneously forming process with circular and rectangular shape will used to a part development such as notebook computer case, cell phone and bipolar plate of fuel cell.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 고액공존금속의 성형기술 심포지엄
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• pp.174-182
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• 1997

The technology of Semi-Solid Forging (SSF) has been actively developed to fabricate near-net-shape products using light and hardly formable materials. Generally, the SSF process is composed of slug heating, forming, compression -holding and ejecting step. After forming step in SSF, the slug is compressed during a certain holding time in order to be completely filled in the die cavity and be accelerated in solidification rate. The compression holding time that can affect microstructural characteristics and shape of products is important to make decision, where it is necessary to find overall heat transfer coefficient properly which has large effect on heat transfer between slug and die. This paper presents the procedure to predict compression holding time of obtaining the final shaped part with information of temperature and solid fraction for a cylindrical slug at compression holding step in closed-die compression process using heat transfer analysis considering latent heat by means of finite element method. The influence of the predicted compression holding time on microstructural characteristics of products is finally investigated by experiment.

• 한국주조공학회지
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• 제30권5호
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• pp.161-166
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• 2010

In this examination, the effect of Sr addition and holding time on microstructure of Al-10.5wt%Si-2wt%Cu secondary die-casting alloy was investigated. Degree of undercooling was improved with increasing the Sr content in this alloy. Up to 0.02wt%Sr addition, acicular and lamellar eutectic structure was observed in the microstructure. Meanwhile, the eutectic Si was modified toward the fine fibrous form by increasing Sr content with more than 0.03wt% and holding time of the melt. The well- modified alloys showed decreased eutectic silicon size from 3.25 ${\mu}m$ to less than 0.8 ${\mu}m$. From these results, the optimal strontium content and holding time were identified on the Al-10.5wt%Si-2wt%Cu secondary die-casting alloy.

• Korean Chemical Engineering Research
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• 제48권1호
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• pp.27-32
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• 2010

후코이단을 보습제 및 기능성화장품 소재로 사용하기 위한 후코이단 특성 및 그 효과에 대해 연구하였다. 후코이단은 미역 포자엽에서 추출하였다. 화장품 소재 시험으로는 보습력 측정, 항산화(DPPH assay, radical scavenging), 안전성(MTT assay)을 실시하였다. 후코이단의 보습력은 최고의 보습제 중의 하나인 히아루론산의 보습력보다 높았고, 분자량이 감소함에 따라 보습력이 약간 증가하였다. 후코이단은 높은 안전성과 항산화력을 보였다. 후코이단의 보습력 및 항알레르기 효과를 평가하기 위해 아토피 환자 46명에게 후코이단 크림을 6주간 적용하였다. 증상 정도를 나타내는 IGA 값이 3.04에서 2.15로 감소해 39.8%의 증상개선 효과가 있었다.

• 한국가금학회지
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• 제35권2호
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• pp.177-182
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• 2008

본 연구는 육계를 도계장에 도착한 후 수송 차량위에서 $1{\sim}2$시간, $7{\sim}8$시간, $14{\sim}15$시간 동안 계류시키면서 일반 도계장에서 사용하는 방법으로 도체를 처리하고, 통닭 및 부분육의 품질을 조사하였다. 계류 시간에 따른 통닭의 품질은 계류 시간이 짧은 $1{\sim}2$시간 처리구에서 계류 시간이 긴 $14{\sim}15$시간 처리구보다 $1^+$ 등급 출현율이 14% 정도 많이 나타났고, 특히 부분육에서 가슴육의 $1^+$ 등급 출현율이 계류 $1{\sim}2$시간 처리구에서 15% 정도 높게 나타났다. 가슴육의 PSE 출현율이 도계장내에서 육계가 수송 트럭위에서 장시간 계류함에 따라 높게 나타났다. 도체의 pH 변화는 짧은 $1{\sim}2$시간 계류보다 $7{\sim}8$시간 계류에서 보다 낮은 pH를 나타냈으나, 계류 시간이 $14{\sim}15$시간으로 장기화될 때 다시 $1{\sim}2$시간 계류와 비슷한 값을 나타냈다. 육색에서 명도는 $1{\sim}2$시간 계류 보다 $7{\sim}8$시간 계류에서 보다 낮은 명도 값을 나타내었다. 계류 시간이 $14{\sim}15$시간으로 증가함에 따라 근육 및 표피에서 다시 상승하는 경향을 나타냈다. 적색도 값은 계류 시간에 따라 큰 차이가 없었으나, 황색도 값에서는 짧은 $1{\sim}2$시간 계류에 비하여 $7{\sim}8$시간, $14{\sim}15$시간 계류에서 더 낮은 황색도 값을 나타내었다. 육색에 대해 전체적 고찰하였을 경우, 계류 $7{\sim}8$시간에서 육색 변화가 비교적 낮게 나타났다. 결과적으로 장시간 계류하는 것은 전체적으로 닭고기 품질을 저하시키는 큰 요인으로 작용하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.199-203
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• 1995

The technology of Semi-Solid Forging (SSF) has been actively developed to fabricate near-net- shape products using light and hardly formable materials, the SSF process is composed of slug heating, forming, compression holding and ejecting step. After forming step in SSF, the slug is compressed during a certain holding time in order to be completely filled in the die cavity and be accelerated in solidification rate. The compression holding time that can affect mechanical properties and shape of products is important to make decision, where it is necessary to find overall hert transfer coefficeient properly which has large effect on heat transfer between slug and die. This paper presents the procedure to predict compression holding time of octaining the final shaped part with information of temperature and solid fraction for a cylindrical slug at compression hoiding step in closed-die compression process using heat transfer analysis considering latent heat by means of finite element method. The influence of the predicted compression hoiding time on mechanical properties of products is finally investigated by experiment.