• Transactions of Materials Processing
• /
• v.6 no.3
• /
• pp.239-249
• /
• 1997

The behaviour of alloys in the semi-solid state strongly depends on the imposed stress state and on the morphology of the phase which can vary from dendritic to globular. To optimal net shape forging of semi-solid materials, it is important to investigate for filling phenomena in forging process of arbitrarily shaped dies. To produce a automotive part which has good mechanical property, the filling pattern according to die velocity and solid fraction distribution has to be estimated for arbitrarily shaped dies. Therefore, the estimation of filling characteristic in the forging simulation with arbitrarily shaped dies of semi-solid materials are calculated by finite element method with proposed algorithm. The proposed theoretical model and a various boundary conditions for arbitrarily shaped dies is investigated with the coupling calculation between the liquid phase flow and the solid phase deformation. The simulation process with arbitrarily shaped dies is performed to the isothermal conditions of two dimensional problems. To analysis of forging process by using semi-solid materials, a new stress-strain relationship is described, and forging analysis is performed by viscoelastic model for the solid phase and the Darcy's law for the liquid flow. The calculated results for forging force and filling limitations will be compared to experimental data. The filling simulation of simple products performed with the uniform billet temperature(584$^{\circ}C$) from the induction heating by the commercial package MAGMAsoft. The initial step of computation is the touching of semi-solid material with the end of die gate and the initial concept of proposed system just fit with the capability of MAGMAsoft.

• Journal of the Korean Academy of Esthetic Dentistry
• /
• v.25 no.2
• /
• pp.79-87
• /
• 2016

Single visit monolithic restoration can be proceed with digital workflow which consist of intraoral scanning, dental CAD(computer aided design) and restoration milling with CAM(Computer aided manufacturing). While zirconia has more than 900MPa of flexural strength compared with 400MPa for lithium disilicate, shortened fabricating time of lithium disilicate is considered to be a better choice for fabricating single visit full contour monolithic restoration. However, new zirconia materials which are TZI C(Dentsply Sirona) and LUXEN Enamel(Dental Max), new induction heating method of sintering furnace, and new sintering protocols for MoSi2 heating elements sintering furnace offer significantly reduction of full contour monolithic zirconia restoration fabrication time with greater translucency. These new developments lead single visit zirconia restoration in reality.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.27 no.2
• /
• pp.65-69
• /
• 2017

AlN single crystal was thermally treated at 1600, 1700 and $1800^{\circ}C$ in the ambient pressure of under 100 torr. AlN single crystal was obtained by PVT (Physial Vapor Transport) method using by a facility having a growth part which was heated by RF (Radio Frequency) induction heating. The single crystal specimens surface was evaluated by optical microscope and it was recognized that their morphology was varied with the heat treatment temperature and a set ambient pressure. In this report, the optical microscopic results were reported. According to the increase of temperature the crystal surface was etched thermally. It was evaluated by appearance of small pits on the crystal surface.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.163-166
• /
• 1997

Aluminium foam material is a highly porous material having complicated cellular structure defined by randomly distributed air pores in metallic matrix. this structure gives the aluminium a set of properties which cannot be achieved by any of conventional treatments. The properties of aluminium foam material significantly depend on its porosity, so that a desired profile of properties can be tailored by changing the foam density. Melting method is the one of foaming processes, which the production has long been considered difficult to realize becaues of such problems as the low foamability of molten metal, the varying size of. cellular structures, solidification shrinkage and so on. These problems, however, have gradually been solved by researchers and some manufacturers are now producing foamed aluminum by their own methods. Most of all, the parameters of solving problem in electric furnace were stirring temperature, stirring velocity, foaming temper:iture, and so on. But it has not considered about those in induction heating, foaming velocity and foaming temperature in semi-solid state yet. Therefore, this paper presents the effects on these parameter to control cell size, quantity and distribution.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2004.11a
• /
• pp.98-99
• /
• 2004

(1) Using high-frequency induction heating sintering and spark plasma sintering method, the densification of WC-Ni hard materials was accomplished using ultra fine power of Ni and WC. (2) Nearly fully dense WC-Ni could be obtained within 1 min. (3) Relative density and mechanical properties of WC-Ni obtained by HFIHS were high than those obtained by SPS. And WC grain size made by HFIHS was smaller than that made by SPS. (4) The fracture toughness and hardness values of WC-8Ni, WC-10Ni, and WC-12Ni made by HFIHS were $13MPa{\cdot}m^{1/2}\;and\;1950kg/mm^2,\;13.5Mpa{\cdot}m^{1/2}\;and\;1810kg/mm^2,\;14.4MPa{\cdot}m^{1/2}\;and\;1690kg/mm^2$, respectively for 60MPa and an induced current for 90% output of total capacity, 15KW. (5) The fracture toughness and hardness values of WC-8Ni, WC-10Ni, and WC-12Ni made by SPS were $12.2MPa{\cdot}m^{1/2}\;and\;1796kg/mm^2,\;12.9MPa{\cdot}m^{1/2}\;and\;1725kg/mm^2,\;13.6MPa{\cdot}m^{1/2}\;and\;1597kg/mm^2$, respectively for 60MPa and the electric current of 2500 A

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.7
• /
• pp.17-25
• /
• 2017

To resolve the problem of the temperature rise in LED or OLED lighting, until now a thick metal film has been used as a heat-sink. Conventionally, this thick metal film is made by the electroplating method and used as the heat-dissipating plate of the electronic devices. However, nowadays there is increasing need for a Cu metal film with a thickness of several hundred micrometers that can be formed by the dry deposition method. In this work, we designed and fabricated a Cu film deposition system where the heating element is separated from the ceramic crucible, which makes ultra-rapid deposition possible by preventing heat loss. In addition, the resulting induction heating also contributes to the high deposition rate. By tuning the various parameters, we obtained a $100-{\mu}m$ thick Cu film whose heat conductivity is high and whose thickness uniformity is better than 2%, while the deposition rate is as high as $1000{\AA}/s$.

• Proceedings of the KWS Conference
• /
• 2010.05a
• /
• pp.84-92
• /
• 2010

현재 가동 중인 몇몇 가압 경수로 원전 안전 1등급 설비의 이종금속 용접부는 일차수응력부식균열(PWSCC : Primary Stress Corrosion Cracking) 발생의 세가지 조건(민감 재질, 부식 환경, 인장응력)을 동시에 충족하고 있다. 즉, 이종금속 용접부는 PWSCC에 민감한 재질인 Alloy 600 계열 합금으로 제작 또는 용접되어 있으며 고온 수화학 부식 환경 하에 놓여있다. 아울러 오스테나이트 스테인리스 강의 예민화 예방을 위한 용접 후열처리 미실시로 높은 인장 용접 잔류응력이 작용하고 있다. 이러한 이종금속 용접부의 특성상 PWSCC가 발생할 잠재성이 있을 뿐만 아니라 국내외적으로 Alloy 600 계열 합금으로 제작 및 용접된 가압 경수로 원전 안전 1등급 설비의 이종금속 용접부에 실제 PWSCC가 발생된 사례들이 다수 보고되고 있다. 운전 환경 및 재질 변화 없이 PWSCC 발생을 예방하기 위해서는 인장 잔류응력을 이완시켜 낮은 인장 또는 압축 응력화하여야 한다. 이러한 인장 잔류응력 이완방법들로는 PWOL(Pre-emptive Weld Overlay), 레이저 피닝(Laser Peening), MSIP(Mechanical Stress Improvement Process), 워터 제트 피닝(Water Jet Peening), IHSI(Induction Heating Stress Improvement) 방법들이 있는데 공정 시간이 짧고 열 에너지 원이 필요 없으며 전체적인 소성 변형을 야기시키지 않는 레이저 피닝을 본 연구의 대상 방법으로 한다. 본 연구에서는 동적 유한요소 해석을 통해 용접 잔류응력을 이완시키는 레이저 피닝의 효과를 검증하고 용접 잔류응력에 미치는 레이저 피닝 변수의 영향을 고찰하고자 한다. 내부 보수용접이 수행된 경수로 원전 가압기 노즐 이종금속 용접부에 레이저 피닝을 적용한 경우에 대해 상용 유한요소 해석 프로그램인 ABAQUS를 이용하여 동적 유한요소해석을 수행한 결과, 고온 수화학 일차수와 접하는 Alloy 600 계열 합금 내면에서의 인장 잔류응력이 상당히 이완됨을 확인하였다. 또한, 최대충격 압력이 증가할수록, 충격압력 지속시간이 증가할수록, 레이저 스팟 직경이 증가할수록 내표면 인장 잔류응력 이완 정도는 감소하나 이완되는 영역의 깊이는 증가함을 알 수 있다. 또한, 레이저 피닝 방향이 잔류응력 이완에 미치는 영향은 미미함을 알 수 있다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.11a
• /
• pp.18-19
• /
• 2005

EDDC(Evaporation using Drum in Dual Chamber) deposition system was manufactured for 100m long superconducting coated conductor. It is composed of reaction chamber, evaporation chamber and differential chamber. The drum is located across the differential and exposed to both of the evaporation chamber and the reaction chamber, and the tape is wound on the drum. The elements of superconducting material are co-evaporated from respective element boats in the evaporation chamber and deposited on the drum and reacted with oxygen in the reaction chamber. This process repeats by rotating the drum. When the total pressure of the reaction chamber was 5 mTorr, that of the evaporation chamber was $5{\sim}10^{-5}$Torr. This atmosphere can be achieved by means of differential pumping. There are four evaporator in the evaporation chamber. One is the radiation heating evaporator and the others are the high frequency induction evaporator. EDDC is one of promising methods for commercialization of superconducting coated conductor.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.34 no.3
• /
• pp.173-178
• /
• 2001

This study was performed to know the hypocholesterolemic effect of depolymerized alginate obtained by hydrolysis of alginate through a heating process at $121^{\circ}C$. The changes of total cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides and phospholipid levels in serum, as well as the atherogenic index were elucidated in rats for 35 days. In order to evaluate single-dose toxicity of HAG-50 in rats via oral routes, induction any mortalities and abnormal signs in clinical finding, body weight, gross findings and histopathological finding, and estimation of $LD_{50}$ were elucidated. Total cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides and phospholipid levels in the serum significantly decreased and resulted in the decrease of atherogenic index in rats fed diets containing $5\%\;and\;10\%$ HAG-50 (p<0.01). HAG-50 did not induce any mortalities and abnormal signs in clinical findings, body weights, gross findings and histopathological findings in single-dose toxicity test via oral routes of rats, after which it was impossible to estimate $LD_{50}$ values.

• The Korean Journal of Food And Nutrition
• /
• v.10 no.3
• /
• pp.302-308
• /
• 1997

The purpose of this study was to investigate the extraction yield and quality stability as to the oleoresin process with large amount of onion at one time. The first mixed-product is raw onion juice which was reduced the compression and concentrated by Brix 70% mixed together wit the residue which was extracted and concentrated by ethanol, the second product manufactured by the same method above after the autoclaving with onion, and the other product is made by grinding by 50mesh to freeze-dried onion. Each of yields were 7.3, 9.1 and 0.8% and each of total sugar content was 616.4, 712.3 and 150.3mg/g. Therefore the product extracted by ethanol from freeze-dried onion was very low in yield and total sugar content. By the index of the overall odor intensity, contents of total pyruvate were 1,733.7, 520.6, and 2,716.5$\mu\textrm{g}$/g for each product. As a result, oleoresin onion processing that desired to use raw onion was remarkable for odor recovery. For the homogenous mixture with concentrate of onion juice and ethanol extract were emulsified by the addition of 2% of PGDR(polyglycerol condensed ricinoleate) and agitation(10,000rpm, 30 minutes). At this time, interfacial tension was 1.9 dyne/cm and the formation of emulsion was for 96.2% when left over 24hours in 6$0^{\circ}C$. When it was to be centrifuged(2,000$\times$G, 80 minutes) after emulsification, the volume of emulsion level without seperation was 92.6%, and very high in emulsification stability. The induced heating-oxidize with soy bean oil and sesame oil added to 1% of onion oleoresin, induction-time extension effect appeared with antioxidant activity that was applicable for 80.8~82.2% as to the effect of addition of 0.02% BHA.