• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.491-494
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• 2002

To assess the electrostatic interaction of surfaces at the triple contact line, the electrostatic field is analyzed by using the finite element method. The Helmholtz free energy is used as a functional which should be minimized under an equilibrium condition. The numerical results are compared with the nonlinear analytical solution for a two-dimensional charged interface and linear solution for a wedge shaped geometry, which shows fairly good agreement. The method is applied to the analysis of electrostatic influence on the contact angle on a charged substrate. The excess free energy found to increase drastically as the contact angle approaches to zero. This excess free energy Plays an opposite role to the Primary electrocapillary effect, as the contact angle gets smaller. This enables an alternative explanation for the contact-angle saturation phenomenon occurring in electrical control of surface tension and contact angle.

• 한국정밀공학회지
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• 제18권10호
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• pp.53-60
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• 2001

Surface roughness plays a significant role in friction, wear, and lubrication in machine components. Most engineering surfaces have the nongaussian height distribution. So, in this study, contact simulations are conducted for not only gaussian surfaces but also nongaussian surfaces. Nongaussian rough surface considering the kurtosis is generated numerically And the effects of kurtosis on real contact area fraction, average gap, and mean asperity contact pressure are studied. It will be shown that the real contact area fraction and the mean asperity contact pressure are sensitive to the characteristics of surface geometry according to kurtosis.

• 한국전기전자재료학회논문지
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• 제21권9호
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• pp.868-871
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• 2008

We propose an optical-based measuring instrument of catenary system in electric railway. This system was made to utilize line scan camera as inspecting system to measure the stagger and height of overhead contact wire in railway and composed with optical type source and FPGA-based image acquisition system with PCI slot. Vision acquisition software has been used for the application to programming interface for image acquisition, display, and storage with a frequency of sampling. To check the validity of our approach for the intended application, we monitored height and stagger in the overhead wire of a high-speed catenary system in Korea. The proposed optical-based measuring instrument to measure the contact wire geometry such as the hight and stagger shows promising on-field applications for online condition motoring. We expect that a new generation of real-time instruments with demanding various conditions motoring requirement in railway can be easily integrated into optical-based measuring instrument system.

• Journal of Mechanical Science and Technology
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• 제19권spc1호
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• pp.411-421
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• 2005

The development and implementation of an appropriate methodology for the accurate geometric description of track models is proposed in the framework of multibody dynamics and it includes the representation of the track spatial geometry and its irregularities. The wheel and rail surfaces are parameterized to represent any wheel and rail profiles obtained from direct measurements or design requirements. A fully generic methodology to determine, online during the dynamic simulation, the coordinates of the contact points, even when the most general three dimensional motion of the wheelset with respect to the rails is proposed. This methodology is applied to study specific issues in railway dynamics such as the flange contact problem and lead and lag contact configurations. A formulation for the description of the normal contact forces, which result from the wheel-rail interaction, is also presented. The tangential creep forces and moments that develop in the wheel-rail contact area are evaluated using : Kalker linear theory ; Heuristic force method ; Polach formulation. The methodology is implemented in a general multibody code. The discussion is supported through the application of the methodology to the railway vehicle ML95, used by the Lisbon metro company.

• 한국기계연구소 소보
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• 통권18호
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• pp.87-97
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• 1988

The algorithm for relation of contact status, track shift, and contact force caused from wheel/rail contact geometry is presented. Grafting this algorithm into a algorithm of general program analyzing mechanical system, the program for time domain simulation of railway vehicle dynamics, called CASOTD, was developed. In addition, as applied example of CASOTD, the dynamic simulation of railway vehicle running on a rail joint and a irregularly alinemented rail is done in this paper.

• 농업과학연구
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• 제47권2호
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• pp.327-335
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• 2020

The purpose of this study was to analyze the load distribution and contact safety factor for the power take off (PTO) gear of a 71 kW class agricultural tractor. In this study, a simulation model of the PTO gear-train was developed using Romax DESGINER. The face load factor and contact safety factor were calculated using ISO 6336:2006. The simulation time was set at 2,736 hours considering the lifetime of the tractor, and the simulation was performed for each PTO gear stage at the engine rated power conditions. As a result of the simulation, the face load factors for the driving gear at the PTO 1^st, 2^nd and 3^rd stages were 1.644, 1.632, and 1.341, respectively. The contact safety factors for the driving gear at the PTO 1^st, 2^nd and 3^rd stages were 1.185, 1.216, and 1.458, respectively. As the PTO gear stage was increased, the face load factor decreased, and the contact safety factor increased. The load distributions for all the PTO gears were concentrated to the right of the tooth width. This causes stress concentrations and shortens the lifespan of the gears. Therefore, it is necessary to improve the face load factor and the contact safety factor with macro-geometry and micro-geometry.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제31회 춘계학술대회
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• pp.194-200
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• 2000

The sealing performance of an elastomeric O-ring seal using NBR and FFKM has been analyzed for the contact stress behaviors that develop between the O-ring seal and the surfaces with which it comes into contact. The leakage of an O-ring seal will occur when the pressure differential across the seal just exceeds the initial (or static) peak contact stress. The contact stress behaviors that develop in compressed O-rings, in common case of restrained geometry(grooved), are investigated using the finite element method. The analysis includes material hyperelasticity and axisymmetry. The computed FEM results show that the contact stress behaviors are related to materials of NBR and FFKM and temperature of vaccum chamber.

• Tribology and Lubricants
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• 제19권1호
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• pp.9-14
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• 2003

The sealing performance of an elastomeric O-ring using the double layered material has been analyzed fer the contact stress behaviors that develop between the O-ring seal and the surfaces with which it comes into contact. The leakage of an O-ring will occur when the pressure differential across the seal Just exceeds the initial (or static) peak contact stress. The contact stress behaviors that develop in compressed O-rings, in common case of dovetail grooved geometry, are investigated using the finite element method. The FE analysis includes material hyperelasticity and axisymmetry. The computed FEM results show that the contact stress behaviors are related to the ratio of diameter between the inner ring and the outer ring, and the temperature of vacuum chamber.

• 대한수학회지
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• 제55권1호
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• pp.161-174
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• 2018

The aim of this article is to study the k-almost Ricci soliton and k-almost gradient Ricci soliton on contact metric manifold. First, we prove that if a compact K-contact metric is a k-almost gradient Ricci soliton, then it is isometric to a unit sphere $S^{2n+1}$. Next, we extend this result on a compact k-almost Ricci soliton when the flow vector field X is contact. Finally, we study some special types of k-almost Ricci solitons where the potential vector field X is point wise collinear with the Reeb vector field ${\xi}$ of the contact metric structure.

• 자원리싸이클링
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• 제7권5호
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• pp.41-45
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• 1998

간단한 기하학적 원리에 의해 접촉각을 계산할 수 있는 방안을 모색하였다. 접촉각 측정에 일반적으로 이용되는 기기를 사용하지 않고, 단지 고체 표면의 용액 렌즈가 형성하는 접촉원의 지름과 렌즈의 높이를 측정함으로써 상당한 신뢰성을 가진 접촉각의 크기를 계산할 수 있었다. 이 방법의 신뢰성을 확인하기 위하여 동일한 용액 렌즈에 대해 일반적인 접촉각 측정 장치로 접촉각을 측정하여 그 값들을 상호 비교한 결과 오차 한계의 범위내에서 거의 일치함을 확인하였다.