• 소성∙가공
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• 제20권2호
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• pp.99-103
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• 2011

Many parameters influence the frictional behavior of steel sheet during stamping. The contact pressure between a die and a sheet during stamping is one of them. Thus, this parameter is investigated for high strength steel (HSS) sheets, which are widely used for auto body panels due to their potential for weight reduction. Since HSS extend the limits of contact pressure for mild steel, the effect of this parameter on friction cannot be ignored. To investigate the influence of contact pressure on the frictional behavior of steel sheets, a flat type of friction test was conducted on three different steel sheets under various contact pressures. For bare steel sheets, the curve representing the relationship between contact pressure and friction coefficient exhibits a U shape. Coated steel sheets show a similar tendency except at low contact pressure. For these materials, when the contact pressure is very low, the friction coefficient slightly increases with pressure before it starts to decrease. The test results show that the effect of contact pressure on frictional behavior of steel sheet is not negligible even for contact pressures that are lower than the strength of HSS sheet.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.244.2-244.2
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• 2013

Contact Pattern을 Plasma Etching을 통해 Pattering 공정을 진행함에 있어서 Plasma 내에 존재하는 High Energy Ion 들의 Bombardment 에 의해, Contact Bottom 의 Silicon Lattice Atom 들은 Physical 한 Damage를 받아 Electron 의 흐름을 방해하게 되어, Resistance를 증가시키게 된다. 또한 Etchant 로 사용되는 Fluorine 과 Chlorine Atom 들은, Contact Bottom 에 Contamination 으로 작용하게 되어, 후속 Contact 공정을 진행하면서 증착되는 Ti 나 Co Layer 와 Si 이 반응하는 것을 방해하여 Ohmic Contact을 형성하기 위한 Silicide Layer를 형성하지 못하도록 만든다. High Aspect Ratio Contact (HARC) Etching 을 진행하면서 Contact Profile을 Vertical 하게 형성하기 위하여 Bias Power를 증가하여 사용하게 되는데, 이로부터 Contact Bottom에서 발생하는 Etchant 로 인한 Damage 는 더욱 더 증가하게 된다. 이 Damage Layer를 추가적인 Secondary Damage 없이 제거하기 위하여 본 연구에서는 원자층 식각방법(Atomic Layer Etching Technique)을 사용하였다. 실험에 사용된 원자층 식각방법을 이용하여, Damage 가 발생한 Si Layer를 Secondary Damage 없이 효과적으로 Control 하여 제거할 수 있음을 확인하였으며, 30 nm Deep Contact Bottom 에서 Damage 가 제거될 수 있음을 확인하였다. XPS 와 Depth SIMS Data를 이용하여 상기 실험 결과를 확인하였으며, SEM Profile 분석을 통하여, Damage 제거 결과 및 Profile 변화 여부를 확인하였으며, 4 Point Prove 결과를 통하여 결과적으로 Resistance 가 개선되는 결과를 얻을 수 있었다.

• Nuclear Engineering and Technology
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• 제54권8호
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• pp.2989-2998
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• 2022

Line contact structures, such as the contact between graphite brick and graphite tenon, widely exist in high-temperature gas-cooled reactors. Due to the stress concentration effect, the line contact area is one of the dangerous positions prone to failure in the nuclear reactor core. In this paper, the failure mechanism of line contact structures composed of IG11 nuclear graphite column and brick were investigated by means of experiment and finite element simulation. It was found that the failure process mainly includes three stages: firstly, the damage accumulation in nuclear graphite material led to the characteristic yielding of the line contact structure, but no macroscopic failure can be observed at this stage; secondly, the stresses near the contact area met Mohr failure criterion, and a crack initiated and propagated laterally in the contact zone, that is, local macroscopic failure occurred at this stage; finally, a second crack initiated in the contact area and developed in to a Y-shape, resulting in the final failure of the structure. This study lays a foundation for the structural design and safety assessment of high-temperature gas-cooled reactors.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.117-119
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• 2002

In this paper, the geometry effectiveness and contact modes as functions of real contact length on a cap ring have been analyzed for high pressure sealing mechanism in reciprocating actuator. The reaction force and elastic strain energy density are very important parameters for analyzing the sealing performance of an ACGT ring seal. For the high pressure of 800bar and the maximum speed of 3m/s, the main piston is reciprocating along the linear line against the cylinder wall. The computed results indicate that the length ratio of a cap ring is more influential design parameter compared to that of the tribological contact mode. Thus, this paper recommends the discrete contact area rather than a conventional flat contact model. Especially, the sealing capacity is more improved when the length ratio of a cap ring is below 0.625.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.229-230
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• 2002

This paper presents the hot spot behaviors on the rubbing surface of ventilated disk brake by using finite element method. The depth of asperities on the rubbing surface is usually $2-3\;{\mu}m$ so the real contact area is microscopically. Non-uniform contacts between the disk and the pads lead to high local temperatures, which may cause the material degradation, and develops hot spots, thermal cracking, and brake system failures at the end. High contact asperity flash temperatures in rubbing systems, which is strongly related to the hot spot. It was generally known that high temperature over about $700^{\circ}C$ may form martensite on the cast iron which is material for automotive disk brakes. In this paper, the contact stress, temperature distribution and strain have been presented for the specific asperities of real contact area microscopically by using coupled thermal-mechanical analysis technique.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 추계학술대회 논문집 전기설비전문위원
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• pp.72-75
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• 2008

The Electromagnetic Interference(EMI) in railway applications is largely due to doing the power conversion for traction and Auxiliary system on the Highspeed Electric Multiple Unit-400X(HEMU-400X). In order to research on EMI in railway applications, it were included how much the HEMU-400X generates it and it has an effect on the equipments of electric system which resulted from Power Line Disturbance (PLD) phenomenon by the loss of contact during its running. In this study, the dynamic characteristic of a contact wire and pantograph suppling electrical power to high-speed trains are investigated. The analysis of the loss of contact based on Power Simulator program software is performed to develop power line disturbance model suitable for high speed operation. It is confirmed that a contact wire and pantograph model are necessary for studying the dynamic behavior of the pantograph system.

• 한국전기전자재료학회논문지
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• 제14권2호
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• pp.123-129
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• 2001

The optimal high temperature processing conditions for the formation of Ohmic contact of Ti/Al/Pt/Au multiple layers were established for the fabrication of n$^{+}$-GaN/AlGaN/GaN HFET device. Contact resistivity as low as 3.4x10$^{-6}$ ohm-$\textrm{cm}^2$ was achieved by the annealing of the sample at 100$0^{\circ}C$ for 10 sec. using the RTA (Rapid Thermal Annealing) system. The fabricated HFET (Heterostructure Field Effect Transistor) with a structure of n'-GaN/undoped AlGaN/undoped GaN exhibited a low knee voltage of 3.5 V and a maximum source-drain current density of 180 mA/mm at Vg=0V.V.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(I)
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• pp.204-209
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• 2003

The railway vehicle is composed of many suspension components, such as 1st springs, 2nd dampers, that have an influence on the dynamic characteristics of high speed train. Also, the wheel/rail shapes and its contact mechanism affect the dynamic behavior of high speed train. but these geometric contact characteristics are nonlinear functions of the wheelset lateral displacement and it do not exact dynamic analysis for high speed train. there is a need to develop a new wheel/rail contact module for dynamic behavior and wheelset model is divided motor box, wheel box and wheel body. This wheel is moved by motor box and constrained by joint. It is almost same a train and its result is more exactly.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.142-143
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• 2006

Recently, automotive engines have changed to the silent chain system in order to reduce noise and to improve reliability. High contact fatigue strength is needed for the sprockets of silent chain system. As a result, a high-contact-fatigue-strength P/M material was developed using the technology of surface rolling, which densifies the surface layer of sintered parts. It was established that the contact fatigue strength of the developed material was a great improvement over that of the conventionally used sintered material.

• International Journal of Railway
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• 제2권4호
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• pp.187-192
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• 2009

Running test of the Korean High-Speed Train using remote controlled measuring system have been executed on the high speed track in order to evaluate and verify the performance of the train. In this paper, influencing factors on the contact force which represents dynamic characteristics between the pantograph and contact wire are analyzed, according to the track condition, span type and running condition. By the analytical study on the test data, we figured out that contact force and dynamic characteristics of the pantograph are mainly affected by running behavior of the train and the span distance which the train passes.