• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.202-203
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• 2014

금형 내부의 마모를 줄이기 위한 경질 박막의 안정성 향상과 표면에 인가된 압축 잔류 응력이 고주기 피로 특성에 미치는 영향을 연구하기 위해 정밀 플라스틱 사출 금형강에 주로 사용되는 Fe-3.0%Ni-0.7%Cr-1.4%Mn-X강에 스크린 질화처리와 DLC 코팅을 시간과 단일, 복합처리의 변수를 두어 코팅하였다. PAPVD법으로 DLC($3{\mu}m$), 스크린 질화(3h, $50{\mu}m$)/DLC($3{\mu}m$) 코팅 후 고주기 피로 시험을 행하여 고주기 피로 특성을 평가하였다. 스크래치 시험, 마모 시험, 잔류응력 측정을 통해 질화 처리 여부에 따른 코팅의 안정성을 평가하였다. DLC, 스크린질화/DLC 코팅한 경우 압축 잔류 응력의 영향으로 모두 피로 수명이 향상되었고 스크린질화/DLC 코팅한 경우 그 향상폭은 더 컸다. 질화 처리 후 DLC 코팅한 경우 질화층은 버퍼레이어로 작용하여 코팅의 박리를 억제함을 확인하였다.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.1
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• pp.146-153
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• 2001

The difference of composition of composite resin may affect the mechanical properties of composite resin and the environment is important for the properties of materials. The composite resin restoration is always exposed to fluid in oral cavity and the composite resin matrix is able to absorb water, which is accompanied by some swelling of the composite The uptake of water by composites has been correlated with decreases in surface hardness and wear resistance. The purpose of this study was to investigate the effects of water storage in $37^{\circ}C$ distilled water after 7days, 30days, 60days, 120days on compressive strength and flexural strength of dental composite resin, Z-100(group 1) Spectrum(group 2), Clearfil AP-X(group 3), Pyramid(group 4), Heliomolar(group 5). The compressive and flexural strength were measured by instron machine. The following results were obtained: 1. There were significant reduction of compressive strength as water storage time increased, 7days, 30days, 60 days, 120days(p<0.05). 2. There were significant reduction of flexural strength as water storage time increased, 7days, 30days, 60days, 120days(p<0.05). 3. Group 1, 2, 3 -hybrid type showed higher compressive and flexural strength than group 5-microfine type which had lower filler contents.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.560-567
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• 2011

Wheel and rail wear is a fundamental and complicate problem in railway field. The life of railway is usually limited by wear. The wheel surface is subjected to high normal and tangential contact stress. The removal of material from the surface by wear is function of the sliding and contact stress. In the present paper, the wear characteristic depended on slip rate, contact pressure and temperature are investigated and is used to twin disc tester. The result shows that the wear in wheel-rail interface is remarkably depended on slip rate and contact pressure.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1000-1007
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• 2011

Wheel and rail wear is a fundamental and complicate problem in railway field. The life of railway is usually limited by wear. The wheel surface is subjected to high normal and tangential contact stress. The removal of material from the surface by wear is function of the sliding and contact stress. In the present paper, the wear characteristic depended on slip rate, contact pressure and temperature are investigated and is used to twin disc tester. The result shows that the wear in wheel-rail interface is remarkably depended on slip rate and contact pressure.

• Journal of KSNVE
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• v.7 no.6
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• pp.953-958
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• 1997

Corrugation of railway track can be caused by the various dynamic behaviors of traveling wheels and track. In this paper, the coupled vibrations of traveling wheel and railway track are analyzed as the cause of corrugations. To analyze the coupled vibration, the track supported by the sleepers and the traveling wheels are identified to the elastically supported infinite beam and the spring-mass system which runs at constant speed. The Hertzian contact spring is considered between the infinite beam and spring-mass system are calculated. The cause and development of rail corrugation are discussed in the view point of contact force fluctuation affected by the elastic supports and the corrugated surface profile on the track. By the obtained results, the possibilities of resonance are checked between the excitation by the corrugated surface profile and the natural frequency of contact spring-mass system. It may be thought to a development of railway corrugation.

• Journal of Welding and Joining
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• v.19 no.5
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• pp.540-547
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• 2001

This study has evaluated the wear behavior of PTA (Plasma Transferred Arc) Inconel 625 and Stellite 6 overlays on Nimonic 80A substrate. Nimonic 80A alloy was also included for comparison. In order to evaluate the wear performance, three-body abrasive wear test and pin-on-disk dry sliding wear test were performed. Microstructural development during the solidification of deposits is also discussed. Wear test results show that the wear rate of Stellite 6 deposit is lower than that of Inconel 625 deposit and Nimonic 80A. The sliding wear resistance of overlay deposits follows a similar trend to the abrasive wear resistance, but for Nimonic 80A. The main wear mechanisms were abrasive wear for Inconel 625 deposit, adhesive wear and delamination for Stellite 6 deposit in pin-on-disk dry sliding wear test and ploughing in three-body abrasive wear test. Cross sectional examinations of the worn surface of pin specimens after pin-on-disk dry sliding wear test implies that the plastic deformation near worn surface has occurred during the wear testing.

• Journal of Welding and Joining
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• v.19 no.5
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• pp.506-511
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• 2001

Weld overlay has been developed to improve the property of material surface which is used in the severe environment. Weld overlay is the process which uses an arc heat and welds different composition of alloy on the substrate for the improvements of heat resistance and wear resistance. Weld overlay has a lot of advantages which are high hardness, good processing efficiency, easy controlling of layer thickness, good quality and low cost. In this study, weld overlay was performed by MAG welding on the base metal(SS400) with filler metal which contain composite powders(Cr+C+Mn+Mo+NbC) and solid wire(JIS-YGW11). Characterization of hardness and wear resistance were analyzed by EDS, EPMA, XRD and observations of microstructure were performed to investigate characteristics of overlays. The experimental results of overlaid specimens manufactured with Cr+C+Mn+Mo+NbC powders were obtained as fellows. ${\alpha}-phase$, M(Fe, Cr)3C and NbC of overlays were increased with decreasing the wire feed rates and increasing powder feed rates. Also the hardness of overlays were increased and the specific wear were decreased.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1607-1608
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• 2015

현대사회의 고속 고급 교통수단에 대한 요구에 부응하고, 고유가 및 온실가스 등 원유 기반의 교통 시스템의 문제를 해결하기 위해 교통 수단의 다양화 연구가 활발히 진행되고 있다. 석유문제가 심각한 상황으로 전개될 경우, 대륙과 대륙 그리고 국가와 국가 사이의 장거리 이동을 할 수 있는 교통수단은 전기로 추진되는 철도이다. 현재 대중화 되어있는 바퀴 식 철도차량은 초고속 운전 시 기하급수적으로 증가하는 소음, 공기저항 동력 전달의 한계, 레일의 마모라는 문제를 가지고 있으며 이러한 문제점을 가진 철도차량의 대안으로 선형 추진 시스템 연구가 진행 중이다[1] 국내에서는 LSM(Linear Synchronous motor)에 대한 연구가 활발히 진행되고 있으나 LPM 기반 철도 차량 추진시스템에 대한 연구는 이루어지지 않고 있다. 그러나 LSM 추진 시스템에 비하여 LPM 추진 시스템은 우수한 등판 능력, 광역범위의 주행 가능 영역, 경량화에 따른 높은 에너지 효율, 건설비 저감등 다양한 장점을 가지고 있으며 충분한 전략성을 가지고 있다.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.11a
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• pp.108-110
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• 2003

서울지하철역사내의 미세먼지농도는 환기에 의한 외부대기오염의 영향이 크다는 그간의 주장과 연구조사내용과는 달리 금번 이와 관련한 일련의 조사연구에서 그의 대부분이 내부 source에 의하여 결정되는 것을 확인하였다. 그의 중요한 source로서는 운행회수 1일 4226회에 의한 레일과 바뀌, 팬토그래프와 급전시설의 마찰, 1일 이용인원 5,481,000명에 의한 바닥과 신발의 마찰에 의한 마모와 발진현상과 사람들간의 접촉에 의한 섬유상 먼지의 비산, 그리고 역사내부의 서어비스업체등에서 음식조리시 부적적한 환기시설로 인한 것 등이 주요한 요인으로 생각되나 열차의 빈번한 출입으로 인하여 발생하는 열차풍에 의한 번지발생은 source의 큰 부분을 차지한 것이라는 전제하에 본 조사를 실시하게 되었으며 그의 영향정도를 파악하였다. (중략)

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.5
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• pp.380-385
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• 2016

Railway tracks are repeatedly overstressed and damaged owing to increase in passing tonnage and numerous contact cycles between wheels of train and rails. In order to ensure safe train operation, heat-treated rails are used in addition to regular inspection and maintenance of these rails. Normal rails were treated using ultrasonic nanocrystal surface modification (UNSM) to strengthen the surface of rails. A few changes in surface properties were detected with respect to hardness and compressive residual stress after UNSM treatment. Wear and rolling contact fatigue tests were performed using rails whose surfaces were hardened by UNSM and heat-treated rails. The amount of wear and fatigue life cycles were measured to estimate the effect of UNSM on the rail material. The material of the surfacehardened rail showed improved wear and rolling contact fatigue properties.