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질산염 무기금속 화합물의 분무열분해법에 의한 High-$J_c$ YBCO 박막 제조
홍석관,김재근,김호진,조한우,유석구,안지현,주진호,이희균,홍계원,Hong, Suk-Kwan,Kim, Jae-Gun,Kim, Ho-Jin,Cho, Han-Woo,Yu, Seok-Koo,Ahn, Jin-Hyun,Joo, Jin-Hoo,Lee, Hee-Gyoun,Hong, Gye-Won 한국초전도학회 2006 Progress in superconductivity Vol.8 No.1
High $J_c$ over 1 $MA/cm^2$ YBCO film has been successfully prepared using nitrate precursors by spray pyrolysis method. Aerosol drolpets generated using a concentric spray nozzle were directly sprayed on a $LaAlO_3$(100) single crystal substrate. The cation ratio of precursor solution was Y:Ba:Cu=1:2.65:1.35. The distance between nozzle and substrate was 15 cm. Deposition temperature was ranging from $750^{\circ}C\;to\;800^{\circ}C$. Deposition pressure was 100 Torr, and oxygen partial pressure was varied from 10 Torr to 50 Torr. The microstructure, phase formation, texture development and superconducting properties of deposited films were largely changed with oxygen partial pressure. Deposited films showed a texture with(001) planes parallel to substrate plane. High quality film was obtained when film was deposited at $760^{\circ}C$ with an oxygen partial pressure of 30 Torr. The critical current density($J_c$) of the YBCO film was 1.75 $MA/cm^2$ at 77 K and self-field.
홍석관,황정호,강정진,윤경환 한국유변학회 2015 Korea-Australia rheology journal Vol.27 No.4
Because of increasing interest in the functional surfaces including micro- or nano-patterns, the mass production of such surfaces has been actively researched. Both conventional injection molding (CIM) and injection/compression molding (ICM) of micro-patterns were investigated in the present study. The molding subject is a multi-scale structure that consists of a macro-scale thin plate and micro-scale patterns formed regularly on its surface. The transcription ratios of micro pattern made by CIM and ICM for different flow length were experimentally measured, and the origin of the obtained results was identified through numerical analysis. It was found that the cavity pressure and polymer temperature are the most important factors for micro-pattern filling; in particular, the polymer temperature is the key factor determining the transcription ratio. It was also found that the difference in CIM and ICM micro-pattern transcription ratios originates from the differences in the cavity pressure history if other molding conditions are the same
홍석관,정의철,이성희,김옥래,김종덕 한국금형공학회 2022 한국금형공학회지 Vol.16 No.4
Fine blanking is a press processing technology that can process most of the product thickness into a smooth surface with a single stroke. In this fine blanking process, shear is an essential step. The punches and dies used in the shear are subjected to impacts of tens to hundreds of gravitational accelerations, depending on the type and thickness of the material. Therefore, among the components of the fine blanking mold (dies), punches and dies are the parts with the shortest lifespan. In the actual production site, various types of tool damage occur such as wear of the tool as well as sudden punch breakage. In this study, machine learning algorithms were used to predict these problems in advance. The dataset used in this paper consisted of the signal of the vibration sensor installed in the tool and the measured burr size (tool wear). Various features were extracted so that artificial intelligence can learn effectively from signals. It was trained with 5 features with excellent distinguishing performance, and the SVM algorithm performance was the best among 33 learning models. As a result of the research, the vibration signal at the time of imminent tool replacement was matched with an accuracy of more than 85%. It is expected that the results of this research will solve problems such as tool damage due to accidental punch breakage at the production site, and increase in maintenance costs due to prediction errors in punch exchange cycles due to wear.
미세폭 슬리팅 공정에서 유한요소해석을 이용한 성형 정밀도 예측
홍석관,이병문,강정진,김종덕,Hong, Seok-Kwan,Lee, Byung-Moon,Kang, Jeong-Jin,Kim, Jong-Deok 한국금형공학회 2008 한국금형공학회지 Vol.2 No.3
In the electronic products, connector which play a role of board-to-board connection is an essential part. The manufacture process of this connector involves slitting and bending stage. Recently, manufacturing the connector is becoming more and more difficult as miniaturization of the electronic products. In this study, FEM analysis was performed on slitting and bending process for connector terminal with micro width in order to predict the cause of inaccurate dimension of connector terminal which occurs in actual industrial spot.
홍석관 한국금형공학회 2018 한국금형공학회지 Vol.12 No.3
Metal 3D printing is very useful for making the injection molds containing complex conformal cooling channels. The most important issue of the 3D printed molds is cost and life cycle. However, powder bed fusion (PBF) methods are vulnerable to fatigue loading because of the presence of pores and rough surfaces. In the present study, the fatigue test was performed to obtain fatigue analysis input data for predicting the durability of a 3D printed injection mold core. The metal 3D printer used to manufacture the specimen was OPM250L from Sodick, and the metal powder material was maraging steel. The ultrasonic fatigue testing method was adopted for the fatigue test. A key advantage of the ultrasonic fatigue method is that 108 ~ 109 long cycle test data or more could be obtained within a relatively short period. Based on the results of the experiment, the effect of heat treatment was negligible. However, there was an apparent difference in durability depending on the presence or absence of the surface treatment
후육 벽 PET 용기에 대한 사출 블로우 성형의 유한요소해석
홍석관,송민재,고영배,차백순 한국금형공학회 2018 한국금형공학회지 Vol.12 No.3
Plastic containers which provides the opportunity to reduce transportation costs are lighter and less brittle than glass containers. As a results, efforts to replace glass with plastic are ongoing. The blow molding method is a typical approach in producing plastic containers. Single-stage injection blow molding (ISBM) is one of the blow molding methods. However, the difficulty in controlling the temperature during the injection molding process is considered its main disadvantage. In this study, ISBM process analysis of relatively thick walled containers such as cosmetic containers is carried out. The initial temperature distribution of the preform is deemed to be the most influential factor in the accuracy of blow molding for the thick vessel. In order to accurately predict this, all heat transfer processes of the preform are considered. The validity of this analytical procedure is verified by comparing the cross-sectional thickness with the actual product. Finally, the validated analytical method is used to evaluate the factors affecting the thickness of the final molded part. The ISBM analysis technique for thick walled vessels developed through this study can be used as an effective predictor for preform design and blow process. Key Words: Blow molding, FEM, Injection molding, ISBM