충격하중을 받는 금속재료의 동적파괴인성치 측정에 관한 연구

선동주,박명균,박세만,최영택 명지대학교 대학원 1997 대학원논문집 Vol.1 No.-

This study is concerned with the determination of dynamic crack initiation toughnesses(K_Id) and dynamic elastic-plastic fracture toughnesses(J_Id) of metallic materials at various temperatures, and utilizes Instrumented Charpy Impact Test as an experimental method. The load-time data needed for the evaluations of the toughnesses are obtained from the instrumented striking tup which has strain gauges in the form of Wheastone bridge circuits. To ensure the reliability and the accuracy of the obtained data, the data is critically scrutinized in view of three criteria: inertia effect, limited frequency response and energy. These are the general conditions that the load -time data from the instrumented tests should satisfy to be considered as proper sets of date for further evaluations. In this study dynamic fracture toughnesses are experimentally determined at various temperatures ranging from 20℃ ∼ 300℃. Because of the inherent dynamic nature of the tests, unique inertia force will develop during impact and exert strong influences to crack initiation energies. The inertia forces are theoretically determined and compared with those results obtained experimentally.

헌법

선동주 고시계사 2010 考試界 Vol.55 No.10

타이타늄 강화 PTFE 차단막을 이용한 수직적 골증대술의 임상적 평가

선동주,이동운,오연아,유정아 대한구강악안면임플란트학회 2018 대한구강악안면임프란트학회지 Vol.22 No.1

Purpose: This study reports four cases of vertical ridge augmentation using titanium reinforced Polytetrafluoroethylene (TR-PTFE) membranes. Material and Methods: Bone augmentation was performed using TR-PTFE membranes in four patients with a vertical bony defect (mean 6.5 ± 0.58 mm) who was scheduled to receive dental implants at the Department of Periodontology, Veterans Health Service Medical Center between January and December 2016. Vertical bony defects were measured intraoperatively using a probe and the exposure of membranes were assessed before and after suture removal and one month after the surgery. The gained area from the reoperation as well as the need for additional bone grafting during implant placement was assessed. Results: The exposure was maintained without inflammation in one site. Placing an implant led to an average of 5.25 ± 0.5 mm vertical augmentation, and none of the cases required additional bone transplantation. A total of ten implants were installed in 4 cases. Over at least 1-year of follow-up, all implants were functioned well. Conclusion: In this case study, bone augmentation using TR-PTFE membranes. led to satisfactory bone regeneration in defective areas with vertical bone resorption. In addition to a greater number of cases, histological assessments should be performed in the future to further substantiate these findings. Conclusion : Various bone alternatives and membranes can be used for alveolar ridge preservation. Considering that the environment differs from that in the general GBR that is performed on areas healed after extraction, it would be important for dental surgeons to make appropriate choices based on a thorough understanding of healing process. In this case report, bone augmentation using a TR-PTFE membrane led to satisfactory bone regeneration in relatively large defects. Well-controlled studies should be added and investigated to support the findings of this study.

세라믹/ 金屬接合材의 界面組織과 接合强度에 關한 數値解析 및 實驗的 硏究

박명균,박세만,최영택,선동주 明知大學校 産業技術硏究所 1997 産業技術硏究所論文集 Vol.16 No.-

In this research, both computational and experimental studies are conducted to reveal mechanical natures of bondings and consequences of joining processes for metals and ceramic pairs. In the computational part of this research a FEM analysis was utilized to effectively evaluate stress fields around ceramic-metal interfaces. Special attentions were paid to consider the low yield strength of interlayer alloys(buffer alloys). For the experimental part the effectiveness of active brazing metal methods was investigated. For the test, four different types of ceramic-metal pairs are fabricated. All the ceramic-metal pairs are brazed in vacuum at 850℃, 900℃ and 950℃. Tensile tests were conducted on the fabricated ceramic-metal pairs to evaluate bond strength between ceramics and metals. The test results show temperature effects and increases in bond strengths which is largely due to the inserted buffer layers(Mo-Mn and Ni Layer).

有限要素法을 이용한 열사이클 荷重壯態에서의 세라믹 /金屬 接合材의 强度 平價

최영택,박명균,박세만,선동주 明知大學校 産業技術硏究所 1998 産業技術硏究所論文集 Vol.17 No.-

In this work, variations of residual stresses are investigated by varying thicknesses of copper interlayers inserted for stress relaxations. Futhermore, various modes of stress distributions are evaluated under different assumptions of physical situations. departing from the simple assumption and adopting new assumption is judiciously made to study variations of residual stresses under the simple and new assumption, respectively. The simple assumption dictates that temperature distributions in the ceramic/metal joints are uniform, which amounts to longer cooling time (slow cooling), while the new assumption relaxes the condition of uniform temperature distributions allowing variations of temperatures in the ceramic/metal joints. Especially, the thermal cycles are applied to ceramic/metal joints retaining residual stresses developed during joining processes. Changes in distributions of residual stresses under the applied thermal cycles and the behavior of ceramic/ metal joints formed at elevated temperatures are evaluated from finite element analysis to produce results in good agreement with the existing experimental data.

유한요소법을 이용한 금속재료의 탄소성파괴인성치 결정에 관한 연구

박명균,최영택,박세만,선동주 明知大學校 産業技術硏究所 1998 産業技術硏究所論文集 Vol.17 No.-

In oder to predict the elastic-plastic fracture toughness for metallic materials, Finite element Method(FEM) was used for analysis of compact tension specimen. ASTM E399 test procedure was adopted for simulation of FEM. The Load-Crack Mouth Opening Displacement curve obtained from this analysis was used to detect the crack initiation point and determine the elastic-plastic fracture toughness Jic. In order to prove the results, they were compared with the results from previous experiments and they agree with experimental results.

유한요소법에 의한 금속재료의 탄소성파괴인성 예측

선동주(Dong-Ju Sun),박명균(Myung-kyun Park),박세만(Sae-Man Bahk),최영택(Young-Taek Choi) 한국가스학회 1997 한국가스학회지 Vol.1 No.1

유한요소법을 이용한 단순인장 시험편의 탄소성파괴인성치 예측

선동주(D.J.Sun),박명균(M.K.Park),박세만(S.M.Bahk),최영택(Y.T.Choi) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.11_2

In oder to predict the elastic-plastic fracture toughness for metallic materials, Finite Element Method(FEM) was used for analysis of compact tension specimen. ASTM E399 test procedure was adopted for simulation of FEM. The Load-Crack Mouth Opening Displacement curve obtained from this analysis was used to detect the crack initiation point and determine the elastic-plastic fracture toughness J_IC. In order to prove the results, they were compared with the results from previous experiments and they agree with experimental results.

3차원 탄소성 유한요소법을 통한 금속복합재료와 지르코니아 접합체의 잔류응력해석

주재황,선동주,최영택,박세만,박명균 明知大學校 産業技術硏究所 1996 産業技術硏究所論文集 Vol.15 No.-

Employing a three dimensional finite element method a thermal elasto-plastic stress analysis was conducted to investigate residual stress distributions on the joining area between a ceramic(ZrO₂) and a SiC whisker-reinforced aluminum (Al composite). For purposes of comparisons, residual stresses at the interfaces on the joining area were first analyzed for varying volume fractions of SiC whiskers utilizing two dimensional elasto-plastic models. The results from the 2-D models were compared with those from 3-D models to understand the Practical nature of residual stresses produced during industrial joining processes for ceramics and metal matrix composites. Additionally, the same procedures were applied to compute stress variations along a line passing through the joining area to obtain a physical insight and to offer a plausible explanations for fracture patterns occuring at the interfaces during bending.

특허 정보를 활용한 R&D 과제 유사도 측정 모델

김종배,변정원,선동주,김태균,김융,Kim, Jong-Bae,Byun, Jung-Won,Sun, Dong-Ju,Kim, Tae-Gyun,Kim, Yung 한국정보통신학회 2014 한국정보통신학회논문지 Vol.18 No.5

정부의 입장에서 R&D 과제간의 유사도를 분석하는 것은 불필요한 예산의 낭비를 없애고, R&D 투자의 효과를 높이는데 있어서 매우 중요한 문제이다. 그 동안, 문서의 내용을 대표하는 키워드를 중심으로 두 문서간의 유사도를 분석하거나, 문장 단위로 유사도를 분석함으로써, R&D 과제의 중복 여부를 판단하기 위한 연구들이 시도되어 왔으나, 여러 가지 이유로 아직까지 그 정확도는 매우 낮은 실정이다. 이에, 본 연구는 기 수행된 R&D 관련 특허를 조사, 수집하는 정부 R&D 특허기술동향조사사업의 특허분석 DB를 활용하여 R&D 과제간의 유사도를 분석할 수 있는 방안을 제시하고자 한다. 이를 위해, 집합 이론 및 확률 이론을 기반으로 한 유사도 측정 모델을 제시하였다. 또한, 제시한 모델의 검증을 위해 156개 과제, 160,218개의 유효특허를 기반으로 유효특허기반 과제 유사도 측정 실험을 수행하고, 그 사례를 제시하였다. For efficient investments of government budgets, It is important to analyze the similarities of R&D projects. So, existing studies have proposed a techniques for analyzing similarities using keywords or segments. However, the techniques have low accuracy. We propose a technique for similarities of projects using patent information. To achieve our goal, we suggest three metrics that are based some mathematic theories; set theory and probability theory. In order to validate our technique, we perform case studies that have 156 R&D projects and 160,218 patent informations.