• Tribology and Lubricants
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• 제13권3호
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• pp.93-101
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• 1997

The numerical results on the stress distributions of rail-wheel contact problems are presented for three models in a high-speed rail system. These models which have straight and tapered (1:40 and 1:20) contact geometries between the wheelset and rail are analyzed using the finite element approach. From the simulation results we found that the tapered geometry (1:20) of railwheel contact base line showed very stable contact stress distributions for a whole contact position between the wheel and rail in a curved rail section. The FEM computed results may present an optimized slope geometry of rail-wheel contact in a high-speed railway system.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 추계학술대회 논문집
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• pp.585-586
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• 2006

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.610-614
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• 1996

Sealing of lubricat-air mixture in the high performance machining conte is one of most the important characteristics to carry out enhanced lubrication. High speed spindle requires non-contact type of sealing mechanism. Evaluating an optimum seal design to minimize leakage is concerned in the aspect of flow control. Effect of geometry and leakage path are evaluated according to variation of sealing geometry, Velocity, pressure, turbulence intensity of profile is calculated to fina more efficient geometry and variables. This offers a methodological way of enhancement seal design for high speed spindle. The working fluid is regarded as two phases that are mixed flow of oil phase and air phase. It is more reasonable to simulate an oil jet or oil mist type high speed spindle lubrication. Turbulence and compressible flow model are used to evaluate a flow characteristic, This paper arranges a geometry of mostly used non-contact type seal and analyzes leakage characteristics to minimize a leakage on the same sealing area.

• Tribology and Lubricants
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• 제24권2호
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• pp.90-95
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• 2008

An elastic-plastic contact analysis is developed using a semi-analytical method. The elastic contact is solved within a Hertz theorem. The reciprocal theorem with initial strains is then introduced, to express the surface geometry as a function of contact stress and plastic strains. The irreversible nature of plasticity leads to an incremental formulation of the elastic-plastic contact problem, and an algorithm to solve this problem is set up. Closed form expression, which give residual stresses and surface displacements from plastic strains, are obtained by integration of the reciprocal theorem. The distribution of contact stress, residual stress and plastic strain are obtained by the changed surface geometry.

• EDISON SW 활용 경진대회 논문집
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• 제3회(2014년)
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• pp.409-411
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• 2014

Based on the first-principles computations, the nature of the microscopic geometry of the molecule-electrode contacts was addressed. The single-molecule junction was prepared by connecting hexanediothiolate (HDT) to Au(111) electrodes via one, two, and three Au adatoms having coordination number of one (CN1), two (CN2), and, three (CN3), respectively. The contact atomic structure and energy of the stretched Au-HDT-Au junction was observed. The analysis revealed that the contact geometry with lowest coordination number (CN1) is energetically more stable than CN2 and CN3.

• JSTS:Journal of Semiconductor Technology and Science
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• 제14권5호
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• pp.588-593
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• 2014

Current crowding problem can worsen the internal quantum efficiency and the negative-voltage ESD of InGaN-based LEDs. In this paper, by using photon emission microscope and thermal emission microscope measurement, we confirmed that the electric field and the current of the InGaN-based LED sample are crowded in specific regions where the distance between p-type metal contact and n-type metal contact is shorter than other regions. To improve this crowding problem of electric field and current, modified metal contact geometry having uniform distance between the two contacts is proposed and verified by a numerical simulation. It is confirmed that the proposed structure shows better current spreading, resulting in higher internal quantum efficiency and reduced reverse leakage current.

• 한국기계가공학회지
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• 제12권6호
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• pp.101-108
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• 2013

An aircraft fuel hose is a kind of high pressure hose, and generally consists of a nipple, a socket, an inner tube, and a reinforcement layer to increase the tensile strength. Especially the nipple supports the other components in manufacturing stages such as the swaging or crimping processes however, the nipple also serves to prevent leakage in cases of hose engagement with a hydraulic system. To ensure the seal of the hose assembly, a beam seal fitting with metal-to-metal contact is usually adopted at the end of a nipple. Therefore, the geometry of the beam is an important parameter to be determined to make sure there is sufficient contact force. This study aims to investigate the effects of beam seal geometry on the contact force by changing the inclined angle and the thickness of the beam. The results reveal that the proper thickness and inclined angle of the beam seal are 0.45 mm and $8.5^{\circ}$, respectively.

• 한국철도학회논문집
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• 제15권5호
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• pp.447-453
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• 2012

본 논문은 경부 고속선과 같이 사전이도가 주어지는 기설 전차선로에서 전차선 장력만을 증가시켜 임시적인 속도 향상 도모하는 경우에 팬터그래프와 습동하는 전차선의 접촉 평면상의 기하학적 형상의 변화가 어떻게 될 것인가를 검토한 것이다. 검토를 위하여 우선 사전이도가 있는 경우에도 정확히 드로퍼 길이를 계산해 낼 수 있는 드로퍼 길이 계산 수식에 대하여 알아보았다. 다음으로 드로퍼 길이 계산 수식을 프로그램화한 전용계산 프로그램을 이용하여 경부고속선 전차선로의 49.5m 경간을 대상으로 전차선 장력을 20kN에서 23kN 및 25kN으로 증가시켰을 때 사전이도량의 변화를 계산하여보았다. 그리고 경부 2단계 구간 현장에서 실제 장력 증가 실험을 실시하여 사전이도량의 변화를 측정하였다. 측정 결과는 계산 값과 비교 검토를 수행하였으며, 결론적으로 전차선 장력을 증가시켜도 기하학적 형상의 변화는 미미하며 집전 성능에 별 영향이 없을 것임을 확인하였다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.255-256
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• 2002

In this paper, the frictional behavior according to the contact geometry was investigated using a micro-tribotester built inside a Scanning Electron Microscope (SEM) and an Atomic Force Microscope (AFM). FFT (Fast Fourier Transform) analysis for friction was conducted as a method to interpret the contact condition. From the experimental results, it could be concluded that the relative dimensions and distribution of contact asperities on the surface could be predicted by the power spectrum and main frequency in the FFT analysis of the friction signal.

• 한국기계연구소 소보
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• 통권15호
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• pp.5-17
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• 1985

Dynamics of railway vehicles are strongly influenced by the wheel/rail contact forces. Wheel/rail contact geometric characteristics are important parameters to determining wheel/rail contact forces. In general, geometric relations between wheel and rail are represented by nonlinear functions of the wheelset lateral excursion and the relative yaw angle. There are some analytical and experimental studies to show the influences of the wheelset lateral displacement on wheel/rail geometric relations. Recently radial steering bogie which is designed to have flexible yaw motions of wheelsets was developed to improve curve negotiation performance. The radial steering bogie makes it important problem to study the effects of wheelset yaw motion on wheel/rail geometric relations. This paper describes the method to analyze 3-dimensional wheel/rail contact geometry considering wheelset yaw motion and describes also some computer simulation results.