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비전 변형률 측정 시스템을 이용한 마이크로 박판소재의 물성평가 기술
이혜진,이낙규,최석우,이근안,신준희,김태주,주은덕 한국공작기계학회 2008 한국공작기계학회 춘계학술대회논문집 Vol.2008 No.-
This paper is concerned with the precision material property measurement of a micro metal thin foil (Ni-99.9%) that is used in MEMS technology. Since these MEMS components require great precision and accuracy, evaluation of reliability such as the life cycle endurance test, impact test, and residual stress test is necessary for these components. However, in practice, real reliability tests are not easy to perform due to consideration of various factors. Rather than actual testing, it would be much easier to evaluate the reliability of components by the analytical approach. Although the analytical method is utilized by numerical software tools, it is obviously necessary to acquire fundamental properties of materials through real test methods. But the acquisition method of micro strain data is so difficult in micro tensile testing, because the micro tensile testing specimen has several micros thickness and small size of shape. So we research on the measurement method of micro strain data using a vision image analysis.
유동환경용 FSS 전극 유전체 장벽 방전 구조 플라즈마 발생기의 X-Band 내 RCS 감소 효과
오태주(Taejoo Oh),조창석(Changseok Cho),안욱현(Wookhyun Ahn),육종관(Jong-Gwan Yook),이장재(Jangjae Lee),유신재(Shinjae You),임진우(Jinwoo Yim),하정제(Jungje Ha),배지훈(Gihun Bae),유흥철(Heung Cheol You),이용식(Yongshik Lee) 한국전자파학회 2021 한국전자파학회논문지 Vol.32 No.11
본 논문에서는 주파수 선택 표면(FSS: frequency selective surface)을 전극으로 활용한 유전체 장벽 방전 (DBD: dielectric barrier discharge) 플라즈마 발생기를 제안하고, 이를 기반으로 2차원 평면형 타겟의 레이다 단면적(RCS: radar cross section)을 감소시키는 것을 실험적으로 검증한다. 주파수 선택 표면의 통과대역이 레이다 신호의 대역과 일치하도록 설계함으로써 기존 평행판 커패시터형 DBD 발생기와 달리 발생기를 타겟에 부착하는 과정에서 발생하는 타겟의 RCS 왜곡과 레이다 신호의 편파에 따라 응답이 달라지는 현상을 최소화할 수 있다. 나아가서 유전체 테두리를 활용함으로써 전극과 4.572 mm의 간격을 두고 존재하는 접지면 사이의 공간을 완전 격리시켜 유동환경에서도 안정적인 플라즈마 방전이 가능하다는 것을 확인하였다. 제안된 플라즈마 발생기를 제작하여 플라즈마 최적 방전 및 RCS 측정 실험을 통해 X-band 에서 최대 2.9 dB의 RCS 감소 효과를 얻을 수 있음을 실험적으로 검증하였다. In this study, an frequency selective surface (FSS) electrode of a dielectric barrier discharge (DBD) plasma generator, with a two-dimensional planar target, for radar cross section (RCS) reduction is proposed and measured. The electrode of the proposed plasma generator is based on a cross FSS array conductor. Therefore, it is possible to minimize the amount of RCS change according to the efficient plasma discharge and polarization of the signal from the radar. In addition, a frame of FR-4 dielectric material is placed between the 4.572 mm gap of the ground surface and the electrode to reduce RCS owing to stable plasma discharge in a fluid environment in which the aircraft operates. The proposed plasma generator is fabricated to determine the optimal plasma discharge and RCS measurement. The measurement results showed a 2.9 dB RCS reduction in the X-band.
Changho Lee,Taejoo Lee,Yoon Suk Choi 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.11
Machine learning of the creep rupture life dataset, which consists of test temperatures, stresses and rupture lives, receivedless attention in the community due to numerous physics-based and empirical models already available for the prediction ofthe creep rupture life, and a limited number (typically about 10 to 40) of available creep rupture life data points consideredto be too small to be trained for the reliable prediction. A simple data analytics approach was developed for the quick andreliable assessment of the creep rupture life. The proposed approach involves linear regression as a major algorithm and thefour features [two generic features (temperature (T) and stress (σ)) and two physics-informed features (ln σ and −1/T)], andexhibited superior creep rupture life predictions (validated by the 41 creep datasets of ferritic Cr steels) without any violationof creep phenomenology and data overfitting. In particular, the proposed approach was extremely useful to assess thefidelity of the Laron–Miller relation for a given creep rupture life dataset and to find an optimum Larson–Miller constantthat minimizes a deviation from the ideal Larson–Miller relation. An analytical model was also developed based on curvefitting of Larson–Miller parameters calibrated by the optimum Larson–Miller constant. The proposed analytical model gaveadditional improvement in creep rupture life prediction, particularly for creep datasets, of which creep rupture lives wereslightly less predicted by the data analytics approach. The two proposed models provided a synergistic effect in creep rupturelife prediction when interactively used.
비전 변형률 측정 시스템을 이용한 마이크로 박판소재의 물성평가 기술
이혜진(Hye-Jin Lee),이낙규(Nak-Kyu Lee),최석우(Seogou Choi),이근안(Geunan Lee),신준희(Junhee Shin),김태주(Taejoo Kim),주은덕(Andy Chu) 한국생산제조학회 2008 한국생산제조시스템학회 학술발표대회 논문집 Vol.2008 No.5
This paper is concerned with the precision material property measurement of a micro metal thin foil (Ni-99.9%) that is used in MEMS technology. Since these MEMS components require great precision and accuracy, evaluation of reliability such as the life cycle endurance test, impact test, and residual stress test is necessary for these components. However, in practice, real reliability tests are not easy to perform due to consideration of various factors. Rather than actual testing, it would be much easier to evaluate the reliability of components by the analytical approach. Although the analytical method is utilized by numerical software tools, it is obviously necessary to acquire fundamental properties of materials through real test methods. But the acquisition method of micro strain data is so difficult in micro tensile testing, because the micro tensile testing specimen has several micros thickness and small size of shape. So we research on the measurement method of micro strain data using a vision image analysis.
금속소재 마이크로 형상 압축성형을 위한 데스크탑 마이크로 성형시스템 기술
이혜진(Hye-Jin Lee),김성욱(Seongouk Kim),김태주(Taejoo Kim),신준희(Junhee Shin),주은덕(Andy Chu),이낙규(Nak-Kyu Lee) 한국생산제조학회 2008 한국생산제조시스템학회 학술발표대회 논문집 Vol.2008 No.5
In this Research, the desktop micro forming manufacturing system has been developed. A micro forming system has been achieved in Japan and it's developed micro press is limited to single forming process. To coincide with the purpose to be more practical, research and development is necessary about the press which the multi forming process is possible. Micro patterned metal components are used in so many precision engineering fields. This micro pattern plays an important part in the functional movement of precision module. This micro pattern on the metal component can be made by EDM(Electro Discharge Machining). But this EDM method has low productivity because EDM tools can be worn easily. If another manufacturing process is developed with high productivity, industries can product the competitive goods. So we research on the forming process and system to make micro functional pattern on the metal component.
금속소재 마이크로 형상 압축성형을 위한 데스크탑 마이크로 성형시스템 기술
이혜진,김성욱,김태주,신준희,주은덕,이낙규 한국공작기계학회 2008 한국공작기계학회 춘계학술대회논문집 Vol.2008 No.-
In this Research, the desktop micro forming manufacturing system has been developed. A micro forming system has been achieved in Japan and it's developed micro press is limited to single forming process. To coincide with the purpose to be more practical, research and development is necessary about the press which the multi forming process is possible. Micro patterned metal components are used in so many precision engineering fields. This micro pattern plays an important part in the functional movement of precision module. This micro pattern on the metal component can be made by EDM(Electro Discharge Machining). But this EDM method has low productivity because EDM tools can be worn easily. If another manufacturing process is developed with high productivity, industries can product the competitive goods. So we research on the forming process and system to make micro functional pattern on the metal component.