• Journal of the Korean Geotechnical Society
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• v.31 no.11
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• pp.33-40
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• 2015

Volcanic rocks in Jeju Island indicate the differences in geological and mechanical characteristics from region to region, and have vesicular structure caused by various environmental factors. In this study, triaxial compressive strength tests were conducted for intact rocks sampled in northeastern onshore and offshore, southeastern offshore and northwestern offshore of Jeju Island. The estimated cohesion and internal friction angle from the results of triaxial compression tests were compared and analyzed with absorption, a parameter representing the vesicular properties of basalts in Jeju Island. As a result, it was found that the relationship between cohesion and absorption could be classified clearly, considering two different linear relationships in bulk specific gravity and absorption. As the absorption increases, the cohesion decreases exponentially. In addition, the internal friction angle decreases almost linearly with increasing in the absorption, regardless of the relationships in bulk specific gravity and absorption.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.1
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• pp.155-164
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• 2002

The journal bearings use in machine parts which move relative to each other and those reduce friction and wear of journals. The journal bearings are designed to operate in the hydyodynamic lubrication regime, but elastohydrodynamic lubrication nay occur if the pressures are too high or the running speeds are too low at machine elements. It is the phenomenon that the lubricant film is broken and some parts of surfaces are in rolling contact, so that wear will increase in mixed lubrication regime. The purpose of this study is to minimize the wear rate of journal bearings for extending machine life. The wear mate in mixed lubricated regime is selected as objective function because most of wear of the journal bearings develops in elastohydrodynamic lubrication. The journal bearings we represented by a bearing radius, shaft radius, and bearing width, but the bearing radius only is selected as design variables due to a bearing radius has an influence on friction loss, stability limit velocity, and film parameter, which are used as constraints. For numerical calculation, PLBA, that is a class of the RQP algorithm, is used.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.1
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• pp.55-61
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• 2017

Recently several researches have been conducted to develop sliding track system in which friction between concrete track and bridge slab has been reduced. This paper investigated shear load carrying capacity of lateral supporting concrete block which should be implemented to resist lateral load due to train in sliding track system. In order to evaluate shear load carrying capacity of lateral supporting concrete block, analytical model has been developed considering concrete friction and rebar dowel action along construction joint. The proposed model predicted test results on the shear load carrying capacity from literature conservatively by 13~23% because effect of aggregate interlock along crack surface was neglected. Since construction joint status is ambiguous on construction site, it can be concluded that the proposed model can be used for reasonable design of lateral supporting concrete block. Based on the proposed model, design proposal for lateral supporting concrete block has been established.

• The Journal of Engineering Geology
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• v.23 no.3
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• pp.217-225
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• 2013

We carried out geometrical, kinematic, and geomechanical analyses on a lineament (the Imgok fault) near Gangneung, observed in ASTER images and aerial photographs, and field surveys. Earthquake focal mechanism solutions, used to estimate the present-day stress state, revealed that the direction of maximum compression is approximately N$70^{\circ}$E and that the stress condition is in favor of either strike-slip or reverse movement on the fault. The strike of the fault is not ideal for slip under the present-day stress field and thus the fault has a low slip tendency. However, the fault may be able to slip if the frictional coefficient (${\mu}$), representing the resistance of the fault to slip, is sufficiently low (e.g., ${\mu}$ < 0.25).

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.5
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• pp.515-524
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• 2008

The ultimate behavior of high-tension bolted joints with various plate thickness and bolt size is investigated using nonlinear F.E. analysis and experimental study. The relation with sliding load, bolt deformation, and failure modes are presented based on plate thickness and bolt size. Three kinds of the bolt diameter(M20, M22, M24) and five types of the steel plates (l2mm, 16mm, 20mm, 30mm, 40mm) are considered for the ultimate behavior of the bolted joints. The numerical model, constructed by commercial F.E. program, ABAQUS, of ultimate behavior of bolted joints is introduced and verified by experimental results. The force-displacement and force-axial strain relations are measured and compared with the results by 3D finite element analysis.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.3
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• pp.95-102
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• 2018

As a recent technical approach, a high-speed planing hull was tried to realize a friction reducing system by simultaneously actuating the triple streamlined step hull form in association with optimum speed of 35 knot planing for fishing boat. In this approach, the streamlined step hull form with triple structure of type was attached under the bottom of high-speed planing hull, while a friction resistance is reduced in the process of running at the speed of 35 knot. In addition, this research was to make a performance test as to the manufactured product and acquire the purposed values and the development items. Actually, after manufacturing the desired prototype of high-speed planing hull, the significant items, fuel efficiency (second) and amount of fuel consumption (degree) including maximum speed (knot) were estimated for a performance test. And tensile strength (MPa) and bend strength (MPa) as to the completed prototype like a high speed planing hull were also acquired during the test.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.227-227
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• 2010

동력 전달을 위한 구동 부품에 대한 내마모성 개선을 통한 에너지 효율 및 부품의 수명 향상에 대한 사회적 관심이 급증하고 있다. 특히, 최근에는 자동차용 구동부품에 저마찰 내마모 특성이 우수한 Mo-N-Cu 나노복합체 박막에 대한 연구가 활발하게 진행되고 있다. 본 연구에서는 Mo-N-Cu 나노복합체 박막을 마그네트론 스퍼터링 증착법을 활용하였고, 이때 Mo 및 Cu 타겟을 적용하여 동시에 증착하였다. 진공 챔버의 진공도는 $5{\times}10^{-6}\;Torr$ 이하의 초기 진공도를 확보한 이후, 알곤 및 질소 가스를 주입하여 공정 압력이 5 mTorr 수준이 되도록 하였다. 이때 N2/(Ar+N2) = 0.5를 유지하였다. Mo-N-Cu 박막내에 Cu 함량 변화를 위해 Mo 캐소드는 D.C. 1 kW로 고정하고 Cu 캐소드에 R.F. 파워를 0, 40, 60, 80 W로 변화하였다. 박막의 두께는 증착시간을 변화하면서 $1\;{\mu}m$ 이상이 되도록 하였다. Cu 캐소드에 인가된 파워의 변화에 따라 Mo-N-Cu 박막내 Cu 함유량은 10 at.%까지 변화되는 것을 EDX 분석을 통해 확인하였다. 또한 증착된 Mo-N-Cu 박막의 표면 및 단면에 대한 FE-SEM 분석을 통하여 전형적인 주상구조를 지닌 MoN 박막에서 Cu 함량이 증가할수록 Mo-N-Cu 박막의 결정성을 방해하는 것을 확인하였다. 또한 XRD 분석을 통하여 박막의 결정 구조 분석을 하였고, Nano Indentor를 통하여 30 GPa 수준의 고경도를 지닌 박막이 형성됨을 확인하였다. 박막의 내마모 특성 평가를 위해 ball-on-disk 트라이보미터를 활용하여 마찰계수 평가를 수행하였고, Cu 함유량의 변화에 따라 마찰계수가 MoN 박막의 경우 0.8에서 Cu 함량이 5 at.%에서 0.15로 급격하게 낮아짐을 확인하였다.

• Tribology and Lubricants
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• v.35 no.3
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• pp.183-189
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• 2019

The driver seat of an automobile is in direct contact with the driver and provides the driver with a safe and comfortable ride. The seat consists of a frame, a rail, and many recliners. In recent years, strength and operating force measurement testing of the recliner have become vital for designing car seats. However, performance evaluation requires expensive testing equipment, numerous seat products, and considerable time. Therefore, the trend is to reduce experimentation through interpretation. This study examines the lubrication of solid lubricant for automotive seat recliners and confirms the friction and wear performance. In this study, the lubrication behavior of solid lubricants for car seat recliners is investigated to ascertain the friction and wear performance and to provide accurate values for the strength analysis. The friction material consists of a pin and a plate made from steel, which is widely used in recliners. The friction and wear under lubrication conditions are measured by a reciprocating friction wear tester. The friction coefficient is obtained according to the load and speed. Based on the obtained results, it is possible to achieve a reduction in the error of the test value and the analysis by providing the friction coefficient and wear of the lubricant. The results can be applied to the analysis of automobile seat design.

• Journal of the korean Society of Automotive Engineers
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• v.3 no.1
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• pp.1-4
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• 1981

Clutch disc 의 facing은 사용할 때마다 마찰로 인하여 마멸된다. 마멸함에 따라 clutch cover의 구조상 clutch cover의 release lever가 올라와 clutch release bearing (thrust bearing)과의 간 극이 작아져서 드디어 이 간극이 없어지게 되면 release lever가 clutch release bearing을 누르게 되어 평상에도 clutch가 절반 정도로 떨어지는 상태로까지 됨으로써 clutch의 완전한 연결을 할 수 없어 slip이 일어나게 된다. 이상과 같은 문제점들을 해소하기 위하여 clutch의 control system을 수시로 조정하지 않으면 안되며 이러한 번거로움을 피하기 위하여 release lever가 올라옴으로써 release bearing과의 간극이 작아져서 자동적으로 일정한 간극을 유지하여 clutch의 slip을 방지하고 clutch기구의 내구성을 향상시키기 위한 것이 무조정식 release cylinder, 혹은 clutch adjuster이다. 이에 대한 신형식 두 종류의 구조, 작동 및 특징에 대하여 해설하여 본다.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.9-13
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• 2003

The objective of this study is structural analysis of rope brake for elevator. The finite element model was developed to compute the stress, strain and friction force for rope brake. The ANSYS code was used for this analysis. In order to structural analysis of rope brake, many variables such as internal pressure, boundary condition, load condition and constraints were considered.