유압벌지실험을 이용한 순 티탄늄 판재의 소성유동곡선 평가(제2보)

김영석(Kim, Young-Suk),김진재(Kim, Jin-Jae) 한국산학기술학회 2016 한국산학기술학회논문지 Vol.17 No.4

본논문에서는대형 선박의 판형열교환기등에 널리 이용되고있는 순 티타늄판재의소성변형을 유한요소해석하기 위한 기초 데이터로서 순 티타늄 판재의 유동곡선을 평가하였다. 순 티타늄 판재의 프레스 가공 시에 판재에는 국부적으로 큰 소성변형이 발생하고 있다. 그러나 기존의 단축 인장실험에서 얻을 수 있는 소성변형률이 낮아서 티타늄 판재의 가공공정 설계를 위한 유한요소해석의 정밀도를 떨어뜨리는 경우가 있다. 본 연구에서는 큰 소성변형률 까지 안정적으로 성형이 가능한 유압벌지실험을 수행하여 재료의 소성변형에서 가공경화특성을 나타내는 유동곡선으로써 진응력-진변형률 선도를 구하였고 그 결과를 인장실험 결과와 비교하였다. 순 티타늄 판재의 유압벌지실험에서 재료의 변형률은 3D 디지털 영상 상관법을 이용한 ARAMIS 시스템으로 실시간 측정된다. 이 유압벌지실험으로부터는 소성 변형률이 0.65 이상 까지도 안정적으로 재료의 소성유동곡선을 얻을 수 있었으며 그 결과는 Kim-Tuan 이 문헌 17[Y.S. Kim, J.H. In, Korean Acadmia-Ind. Coop. Soc.,(be in print), 2016] 의 연구에서 제안한 가공경화식으로 잘 핏팅됨을 알 수 있었다. In this study, the plastic flow curve of commercially pure titanium sheet (CP Ti) actively used in the plate heat exchanger etc., was evaluated. The plastic flow curve known as hardening curve is a key factor needed in conducting finite element analyses (FEA) for the forming process of a sheet material. A hydraulic bulge test was performed on the CP Ti sheet and the strain in this test was measured using the DIC method and ARAMIS system. The measured true stress-true strain curve from the hydraulic bulge test (HBT) was compared with that from the tensile test. The measured true stress-true strain curve from the hydraulic bulge test showed stable plastic flow curve over the strain range of 0.7 which cannot be obtained in the case of the uniaxial tensile test. The measured true stress-true strain curve from the hydraulic bulge test can be fitted well by the hardening equation known as the Kim-Tuan model.

New Stress-Strain Model for Identifying Plastic Deformation Behavior of Sheet Materials

김영석(Young Suk Kim),팜콕트완(Quoc Tuan Pham),김찬일(Chan Il Kim) Korean Society for Precision Engineering 2017 한국정밀공학회지 Vol.34 No.4

In sheet metal forming numerical analysis, the strain hardening equation has a significant effect on calculation results, especially in the field of spring-back. This study introduces the Kim-Tuan strain hardening model. This model represents sheet material behavior over the entire strain hardening range. The proposed model is compared to other well known strain hardening models using a series of uniaxial tensile tests. These tests are performed to determine the stress-strain relationship for Al6016-T4, DP980, and CP Ti sheets. In addition, the Kim-Tuan model is used to integrate the CP Ti sheet strain hardening equation in ABAQUS analysis to predict spring-back amount in a bending test. These tests highlight the improved accuracy of the proposed equation in the numerical field. Bending tests to evaluate prediction accuracy are also performed and compared with numerical analysis results.

도서관인의 명암(明暗) - 도서관도 이젠 도서관의 친구(Friends of the Library)가 필요하다

김영석,Kim, Young-Suk 한국도서관협회 2009 圖協會報 Vol.50 No.1

Technical Advances in Robotic Pavement Crack Sealing Machines and Lessons Learned from the Field

김영석,하스칼,성백준,오에욱,Kim Young-Suk,Carl T. Haas,Sung Baek-Jun,Oh Se-Wook Korean Institute of Construction Engineering and M 2000 한국건설관리학회 논문집 Vol.1 No.1

도로면 유지보수 공법 중 크랙실링은 그 특성상 작업수행과 관련하여, 노무자의 안전을 위협하는 다양한 위험, 열악한 작업환경으로 인한 생산성 및 품질저하, 교통체증으로 인한 차량이용자의 간접비용 상승 등 많은 잠재적 문제점을 내포하고 있을 뿐만 아니라 노무 의존도가 높고 년간 막대한 사업예산을 요하는 국가 기반 유지보수 사업이다. 선진 외국의 경우, 도로면의 초기균열에 대한 보수공법으로써 크랙실링이 일반화되어있고 과거 10여년에 걸쳐 이를 자동화하기 위한 연구노력이 활발히 진행 중이다. 본 논문은 미국을 중심으로 지금껏 개발되어진 크랙실링 자동화 로봇의 프로토타입을 간략히 소개하고 미 연방교통국(FHWA)과 텍사스 주 교통국(TxDOT)의 지원하에, 텍사스 오스틴 주립대학 건설자동화 연구소에서 개발된 크랙실링 자동화 로봇의 연구성과 및 1999년 현장실험 결과를 토대로 크랙실링 자동화 로봇의 타당성 및 적용성 그리고 개발기술의 응용성을 시험한다. 크랙실링 자동화 로봇의 개발과 활용을 통하여 도로의 수명 연장 및 년간 막대한 도로 유지보수 사업예산의 절감이 가능할 것으로 사료되며 개발된 자동화 기술은 추후 빌딩외벽, 대규모 저장탱크 등 도로 이외의 건축.토목 구조물에 발생된 균열의 탐지 및 보수에도 널리 활용될 수 있을 뿐만 아니 라 동영상 처리기술 등의 멀티 미디어 기술과 무선정보통신망을 응용한 본사와 현장간 실시간 안전진단 및 분석에도 그 활용효과가 클 것으로 기대된다.

심뇌통(心腦通),강지연수단(降脂延壽丹) 및 청심조기탕(淸心調氣湯)의 고지혈증(高脂血症)에 대(對)한 실험적(實驗的) 연구(硏究)

김영석,문상관,고창남,조기호,배형섭,이경섭,노상겸,조효란,곽위성,Kim, Young-Suk,Moon, Sang-Kwan,Ko, Chang-Nam,Joh, Ki-Ho,Bae, Hyung-Sup,Lee, Kyung-Sup,Bao, Pei-Rong,Cao, Xiao-Lan 대한한방내과학회 1998 大韓韓方內科學會誌 Vol.19 No.1

In order to evaluate the effects of SIMNETONG, GANGJIYOUNSOODAN and CHUNGSIMJOKITANG(Xinnao-Tong, Jiangzhiyanshou-Dan and Qingxintiaoqi-Tang) on hyperlipidemia, the experimental study was performed in rats without or with hyperlipidemia induced by 2% cholesterol fed-diet or Triton WR-1339. And the levels of serum total cholesterol, triglyceride, HDL-cholesterol, LDL-cholesterol and phospholipid were measured. The results are summarized as follows : In the model of hyperlipidemia induced by 2% cholesterol Fed-diet 1. Both low & highly concentrated GANGJIYOUNSOODAN showed significantly decreasing effects on the level of serum total cholesterol while SIMNETONG & CHUNGSIMJOKlTANG didn't. 2. GANGJIYOUNSOODAN, SIMINETONG and CHUNGSIMJOKITANG showed decreasing effects on the level of serum triglyceride with no statistical significance. 3. Only highly concentrated GANGJIYOUNSOODAN showed increasing effects on the level of serum HDL-cholesterol while the others had no effects. 4. Only highly concentrated GANGJIYOUNSOODAN had decreasing effects on the level of serum LDL-cholesterol while the others had no effects. 5. Highly concentrated GANGJIYOUNSOODAN and CHUNGSIMJOKITANG showed significantly decreasing effects on the level of serum phospholipid while the other had no effects. In the model of hyperlipidemia induced by Triton WR-1339 6. SIMNETONG, GANGJIYOUNSOODAN and CHUNGSIMJOKITANG showed slightly decreasing effects on the levels of serum total cholesterol and triglyceride with no statistical significance. 7. None of SIMNETONG, GANGJIYOUNSOODAN and CHUNGSIMJOKITANG showed any effects on the level of serum HDL-cholesterol. 8. Highly concentrated GANGJIYOUNSOODAN and CHUNGSIMJOKITANG showed decreasing effects on the level of serum LDL-cholesterol but the other had no effects. 9. All of highly concentrated SIMNETONG, GANGJIYOUNSOODAN and CHUNGSIMJOKITANG showed decreasing effects on the level of serum phospholipid with statistical significance. These results show that GANGJIYOUNSOODAN and CHUNGSIMJOKITANG, in orders, have antihyperlipidemic effects. Further study on the mechanism and on the herb screening of these prescription should be followed.

엠보싱 알루미늄 판재의 기계적특성과 스프링백 평가 (제1보)

김영석(Kim, Young-Suk),조준행(Cho, Jun-Haeng),Van-Cuong Do,신동우(Do, Van-Cuong) 한국산학기술학회 2015 한국산학기술학회논문지 Vol.16 No.2

엠보싱된 알루미늄 판재는 표면적이 증가하여 방열효과가 뛰어나고 가공경화에 의해 굽힘강성이 증가하여 자동차 열차단기에 널리 사용된다. 하지만 판재의 특성상 주름발생률이 높아 프레스 성형에 많은 제약이 따른다. 본 연구에서는 3차원 구조 알루미늄 판재의 프레스 성형성 평가를 위한 기초연구로 3차원 구조 엠보싱 콘 형상 판재의 기계적특성을 평가 하고 굽힘실험을 통해 프레스 가공 후 발생하는 스프링백을 정량적으로 평가하였다. 엠보싱 판재는 패턴의 방향에 따라 인장특성이 상이하다. 특히 평행 엠보싱 시편의 경우 항복응력이 감소하며 대각 엠보싱 시편의 경우 항복응력이 증가하게 되고 영률의 감소가 크게 나타난다. 그 결과 굽힘 성형가공 후에 스프링 백에 영향을 미친다. Embossed aluminum sheets were been used in heat insulation purpose for automative exhaust parts because of increasing their surface areas and stiffness reinforcement. However, there are many restrictions because of high rate of wrinkle occurrence on press working. We have performed the tensile and bending tests for embossed sheets to clarity its mechanical properties and springback characteristics. Embossed aluminum sheets showed a different flow stress after plastic yielding due to flattening the embossed cone shape. Above all, yield stress of parallel embossed specimen decreases while its diagonal one increases and the decrease of young’s modulus in the embossed sheets contributes to the increase of springback amount.

MEMS 부품 제조를 위한 나노 리소그래피 공정의 3차원 분자동력학 해석

김영석,이승섭,나경환,손현성,김진,Kim, Young-Suk,Lee, Seung-Sub,Na, Kyoung-Hoan,Son, Hyun-Sung,Kim, Jin 대한기계학회 2003 大韓機械學會論文集A Vol.27 No.10

The atomic force microscopy (AFM) based lithographic technique has been used directly to machine material surface and fabricate nano components in MEMS (micro electro mechanical system). In this paper, three-dimensional molecular dynamics (MD) simulations have been conducted to evaluate the characteristic of deformation process at atomistic scale for nano-lithography process. Effects of specific combinations of crystal orientations and cutting directions on the nature of atomistic deformation were investigated. The interatomic force between diamond tool and workpiece of copper material was assumed to be derived from the Morse potential function. The variation of tool geometry and cutting depth was also evaluated and the effect on machinability was investigated. The result of the simulation shows that crystal plane and cutting direction significantly influenced the variation of the cutting forces and the nature of deformation ahead of the tool as well as the surface deformation of the machined surface.

뇌허혈시 청폐사간탕이 뇌혈류 및 산화질소에 미치는 영향에 대한 실험적 연구

김영석,정우상,박성욱,문상관,고창남,조기호,배형섭,이두익,Kim, Young Suk,Jung, Woo Sang,Park, Seong Uk,Moon, Sang Kwan,Go, Chang Nam,Cho, Ki Ho,Bae, Hyung Sup,Lee, Kyung Sup,Lee, Doo Ick 대한중풍순환신경학회 2005 대한중풍.순환신경학회지 Vol.6 No.1

Objectives: Chungpyesagan-tang is a famous oriental Objectives: medicine treatment frequently used to stroke in Korea. The objective of this study is to evaluate the mechanism of the therapeutic effect of Chungpyesagan-tang on stroke in rat. Methods: We compared the difference in regional cer Methods: ebral blood flow, nitric oxide (NO) synthesis between the control and the Chungpyesagan-tang-treated group after ligating middle cerebral artery. Results: In our study, cerebral blood flow increased more in the stroke rats which had been fed by Chungpyesagan-tang than in the control. Chungpyesagan-tang induced vascular NO synthesis, but had no effect on neuronal NO synthesis. Conclusion: The mechanism of Chngpyesagan-tang's therapeutic effect on ischemic stroke could be explained by increasing cerebral blood flow and vascular NO synthesis.

다결정체의 탄소성 대변형해석

김영석,김정석,Kim, Young-Suk,Kim, Jung-Suk 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.8

Elastic-plastic finite element(FE) simulation was performed for polycrystalline solids subjected to plane strain tensile loading. Using Asaro's double slip crystal plasticity model, the polycrystalline solids were modeled by assigning different initial slip directions to each grain. From the FE calculations, the microscopic deformation characteristics of polycrystalline solids were analyzed. Moreover, the effect of grain size and grain boundaries on the deformation characteristics were clarified.

O, O'-Diethyl DL-1-Aminobenzylphosphonate와 그의 유도체들을 포함한 p-Acetamidobenzenesulfonamide의 합성

김영석,홍석인,김용준,Young Suk Kim,Suk In Hong,Yong Joon Kim 대한화학회 1983 대한화학회지 Vol.27 No.4

새로운 O, O'-diethyl-1-aminobenzylphosphonate와 그의 유도체들을 포함한 다음의 6가지의 p-acetamidobenzenesulfonamide를 합성하였다. O, O'-diethyl N-(p-acetamidobenzenesulfonyl) aminobenzylphosphonate, N-(p-acetamidobenzenesulfonyl) aminobenzylphosphonic acid, O,O'-diethyl N-[N-(p-acetamidobenzenesulfonyl) glycyl] aminobenzylphosphonate, O,O'-diethyl N-[N-(p-acetamidobenzenesulfonyl)-DL-alanyl] aminobenzylphosphonate, O,O'-diethyl N-[N-(p-acetamidobenzenesulfonyl)-L-leucyl] aminobenzylphosphonate, O,O'-diethyl N-[N-(p-acetamidobenzenesulfonyl)-L-phenylalanyl]aminobenzylphosphonate. 모든 화합물은 흰색 결정으로 얻었으며 적외선 분광법과 원소분석으로 확인되었다. Six new compounds of p-acetamidobenzenesulfonamides which contain O, O'-diethyl-1-aminobenzylphosphonate and their derivatives were prepared: O, O'-diethyl N-(p-acetamidobenzenesulfonyl) aminobenzylphosphonate, N-(p-acetamidobenzenesulfonyl) aminobenzylphosphonic acid, O,O'-diethyl N-[N-(p-acetamidobenzenesulfonyl) glycyl] aminobenzylphosphonate, O,O'-diethyl N-[N-(p-acetamidobenzenesulfonyl)-DL-alanyl] aminobenzylphosphonate, O,O'-diethyl N-[N-(p-acetamidobenzenesulfonyl)-L-leucyl] aminobenzylphosphonate, and O,O'-diethyl N-[N-(p-acetamidobenzenesulfonyl)-L-phenylalanyl]aminobenzylphosphonate. All the compounds were obtained as white crystals and characterized by means of elemental analysis and infrared spectroscopy.