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김두인,안효석,최동훈,Kim, Doo-In,Ahn, Hyo-Sok,Choi, Dong-Hoon 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.10
In a micro-scale contact, capillary force and van der Waals interaction significantly influence the contact between asperities of rough surfaces. Little is, however, known about the variation of these surface forces as a function of chemical property of the surface (wet angle), relative humidity and deformation of asperities in the real area of contact. A better understanding of these surface forces is of great necessity in order to find a solution for reducing friction and adhesion of micro surfaces. The objective of this study is to investigate the surface forces in micro-scale rough surface contact. We proposed an effective method to analyze capillary and van der Waals forces in micro-scale contact. In this method, Winkler spring model was employed to analyze the contact of rough surfaces that were obtained from atomic force microscopy (AFM) height images. Self-mated contact of DLC(diamond like carbon) coatings was analyzed, as an example, by the proposed model. It was shown that the capillary force was significantly influenced by relative humidity and wet angle of the DLC surface. The deformation of asperities to a critical magnitude by external loading led to a considerable increase of both capillary and van der Waals forces.
김두인,최동훈,안효석,Kim, Du-In,Choe, Dong-Hun,An, Hyo-Seok 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.4
Gerotor is a planar mechanism consisting of a rotor and lobes which form a closed space, namely a chamber. As active contact points between a rotor and lobes are subjected to very high contact stresses, wear in one or both of the rotor and lobe cannot be avoided. Therefore, in the design of Gerotor used in hydraulic motors a compromise between high torque output and contact stress is of great importance and a thorough analysis of design parameters should be conducted to achieve this compromise. In this study, a contact point is modelled as a linear spring in consideration of equivalent curvature to analyze the contact stress. As the contact stress calculation in this problem is a statically indeterminate type, a numerical iterative scheme has been adopted to obtain the solution. To fully understand the influence of design parameters on the contact stress, the relationship between pressure force, equivalent curvature, contact force and contact stress are analyzed. It is shown that the equivalent curvature of the contact point is a dominant factor that affects the maximum contact stress.
김두인,김광호 한국표면공학회 2009 한국표면공학회 학술발표회 초록집 Vol.2009 No.-
탐침현미경(Atomic Force Microscope)을 이용하여 탐침과 표면사이에 나노스케일의 접촉 반경을 가지는 접촉부를 만든 후 접촉부의 접촉 강성(contact stiffness)을 관찰하였다. 다양한 습도 조건하에서 접촉 강성의 변화를 측정한 결과, 습도에 의해 접촉부의 인장 거동이 달라짐을 확인할 수 있었으며, 습도 변화에 따라 인장 거동의 천이점이 존재함을 확인할 수 있었다.
독일의 원자력 수출과 핵무기 비확산-대한민국의 Sonderweg (특별한 길) ?-Ⅲ
김두일,Kim, Du-Il 한국원자력산업회의 2008 원자력산업 Vol.28 No.8
모험적이고 도전적이었던 1970년대의 원자력 정책과 1980년대 이후의 명분과 실리를 적절히 유지한 독일의 Sonderweg을 살펴보았다. 전통적인 기술 기반, 지식 기반의 사회 구조와 더불어 국민들의 성숙된 시민 의식과 사회 공동체 의식이 원자력과 같이 민감한 이슈에 대한 원숙한 대응을 가능케 한 것 같다. 이번 호 에서는 독일의 원자력 수출에 영향을 미친 대외적 영향에 대해 살펴보고 독일의 Sonderweg에 대한 평가와 대한민국의 Sonderweg은 어떻게 전개되어야 할지에 대해 살펴본다.