• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.59-66
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• 1998

This paper presents friction and wear related results of thermite and gas pressure welded rails under various environmental contact conditions. A welded rail which is fabricated by thermite welding and gas pressure one has been tested over full range of test conditions in a pin-on-disk wear testing machine. The results show that the friction coefficient and wear rates of a welded rail are heavily dependent on the contact pressures and sliding environments for two welding methods such as thermite and gas pressure weldings.

• Tribology and Lubricants
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• v.17 no.6
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• pp.459-466
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• 2001

In this study, the effects of oxide layer formed on the contact parts of TiN coated ball and steel disk on friction characteristics in various sliding conditions were investigated. AISI52100 steel ball was used for the substrate of coated ball specimens, which were prepared by depositing TiN coating with 1(m in coating thickness. AISI1045 steel was used for the disk type counter-body. To investigate the effect of oxide layer on the contact parts of two materials, the tests were performed both in air for forming oxide layer on the contact parts and in nitrogen environment to avoid oxidation. From the test results, the frictional characteristic between the two materials was predominated by iron oxide layer that formed on wear tract of counter-body and this layer caused friction transition and high friction. And the adhesive wear occurred from steel disk to TiN coated ball caused the formation of oxide layer on counter parts between the two materials.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.787-792
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• 1996

The method of manipulation by striking a part and letting it slide until it comes to rest, has been very little studied. However, the manipulation method is not uncommon in our daily lives. We analyze the dynamic behavior of a rigid polygonal part being striked and sliding on a horizontal surface under the action of fiction. There are two parts in this problem; one is the impact problem, and the other is the sliding problem. We characterize the impact and sliding dynamics with friction for polygonal parts, and present the possibility of reverse calculation for motion planning of striking operations. Using a high speed video camera, the computer simulation results are experimentally verified.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.2
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• pp.176-184
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• 2001

The VDC(Vehicle Dynamics Control) is a control system whose target is to improve vehicle stability under critical motion. The system has a good potential of becoming a standard active safety unit in passenger vehicles since it can be implemented on top of the ABS/TCS system with little extra cost. This, however, is possible only when the signals that the VDC system demands can be obtained with sufficient accuracy. In this research, estimators for the road friction coefficient and body sideslip angle have been designed. The two variables have great influence upon performance of the VDC system but not directly measurable. For the estimator design, the Newton method and the nonlinear observer theory have been exploited. The performance of the estimator have been verified via simulations on critical driving conditions.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05d
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• pp.241-246
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• 1996

지진시 미끄럼 등과 같이 전형적인 비선형거동을 하는 구조물에 대한 동적해석을 수행하는 경우 먼저 입력지진의 가속도 시간이력에 대한 기준선 조정이 필요할 때가 있다. 인공적으로 작성된 지진기록의 경우 때로 가속도 시간이력을 적분하여 속도 및 변위 시간이력을 얻었을 때 증가하는 형태로 나타나 이로 인하여 비선형응답이 비정상적으로 커질 수 있기 때문이다. 본 논문에서는 바닥이 마찰거동을 하는 구조물에 대해 간단히 모델하여 이러한 예를 보였으며 또한 주로 사용되는 기준선 조정방법들의 응답영향을 비교하였다. 그 결과 입력지진의 기준선 조정을 하지 않는 것이 항상 보수적인 결과만을 보여 주지 않는다는 점과 기준선 조정의 방범에도 표준화가 필요하다는 점을 파악할 수 있었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.246-248
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• 2005

본 논문은 23kV 가스절연개폐기에서의 윤활제 고착시 발생되는 현상을 조사하였다. 내부 개폐접점부의 마찰저항을 줄이고 가동전극의 윤활한 동작을 위해 사용되는 그리스 (grease)를 과다하게 도포할 경우 고착과 함께 가동전극의 미끄럼운동에 영향을 주는 것이 확인되었다. 영향 평가로는 물성시험과 투 개방 음향특성을 분석하였다. 본 논문의 결과는 개폐장치의 제조품질 개선 및 정전감소에 기여할 것으로 사료된다.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1996.04b
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• pp.35-40
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• 1996

Friction and wear behavior of MoS$_{2}$ bonded films were evaluated at a Block-on-Ring typed tribo-tester, and their properties were compared with those of Falex tester in terms of the wear life of the films. Test results showed that friction and wear properties were significantly affected by the test methods of different contact configuration, and the wear life at a Block-on-Ring type tribo-tester was mostly governed by the resin binder. To obtain long wear life of the films, various combinations of solid-resin-content ratio and chemical resin modification were attempted and evaluated. Adhesion properties of resin binders were also measured and compared by using a scratch tester.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.50-58
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• 2000

A linear elastic fracture mechanics analysis of multiful subsurface cracks propagation in a half-space subjected to moving thermomechanical surface traction was peformed using the finite element method. The effect of frictional heat at the sliding surface on the crack growth behavior is analyzed in terms of the thermal load and peclet number. The crack propagation direction is predicted in light of the magnitudes of the maximum shear and tensile stress intensity factor ranges. When moving thermomechanical surface traction exists, subsurface horizontal cracks are propagation in-plane crack growth rate at the beginning but they are propagation out-of-plane crack growth rate by the frictional heat which is occurrence by the repeated sliding contact.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.401-405
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• 2001

The effects of oxide layer formed on TiN coated ball and counter-body have been investigated from the frictional point of view during sliding tests. AISI52100 steel ball was used for the substrate of coated specimens. Two types of coated specimens were prepared by depositing TiN coating with 1 and 4$\mu\textrm{m}$ in coating thickness. AISI1045 steel was used for the disk type counter-body. To investigate the effect of oxide layer on the contact parts of two materials, the tests were performed both in ambient for forming oxide layer on the contact parts and in nitrogen environment to avoid oxidation.

• International Journal of Highway Engineering
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• v.12 no.1
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• pp.29-37
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• 2010

Porous pavements can provide road users with beneficial characteristics such as skid resistance and surface water drainage under rainy condition, and they cause less tire-road noise than conventional hot mix asphalt(HMA) pavements. However, voids of porous pavements are easily clogged by road debris at early stages, which leads to frequent maintenance works. Therefore, this study focused on the way of minimizing void clogging in porous pavements. During mixture design, the quantity of coarse aggregate has been increased to form many straight void conduits (SVCs) in porous HMAs. These SVCs were found to be effective resisting the void clogging problems. Four different porous HMAs(19mm, 13mm, 10mm, and 8mm) were developed and placed on highway roads. Their performances were validated with field tests during the past four years.