• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 제3회 압연심포지엄 논문집 압연기술의 미래개척 (Exploitation of Future Rolling Technologies)
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• pp.403-411
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• 1999

The steel plate for shadow mask is used in a Cathode-ray tube of TV monitor and is the strictest product in surface quality because hundreds thousand of holes are perforated in a plane of 25 ${\times}$25 inches. To mass-produce this product, a reversible cold rolling mill for silicon steel was used and the rolling technology and the activity for quality improvement are described in this work. Because the steel plate is a mild steel, which is very sensitive to strip-breakage even in a low tension, we reset the minimum tension values matching to the operating conditions. The roll mark due to the multi-segmented araangement of shape controlling roll was prevented by hardening the intermediate shape controlling roll and by changing the existing working-roll into a HSS (Hig Speed Steel) roll. The scratch caused by the speed difference between a idle roll and a strip was prevented by increasing the roll roughness. With these activities, the steel plate for shadow mask can be stable. The continuous improvement of quality is, however, required for the customer satisfaction both of domestic and overseas market.

• 대한기계학회논문집A
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• 제36권11호
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• pp.1479-1485
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• 2012

철도차량 곡선구간 주행 시 곡선주행성능을 향상시키기 위한 능동형 철도차량 개발 분야에서 곡선구간을 실시간으로 인식하기 위한 기술 확보는 매우 중요하다. 그러나 고가의 전용 검측차량을 이용하거나 여러 가지 센서를 복합적으로 이용하는 기존의 곡률반경 추정방법은 실차에 적용하기에는 실용성이 미흡하다. 따라서 본 논문에서는 실차에 적용이 용이하고 경제적인 곡률반경 추정방법을 제안하였다. 새로운 방법은 철도차량 곡선구간 주행 시 발행하는 차체와 대차간의 상대변위를 측정하여 곡률반경을 실시간으로 추정할 수 있는 방법이다. 본 제안 방법의 타당성을 검토하기 위하여 모사해석 및 실차시험을 수행하였으며 그 결과, 제안한 곡률반경 추정방법의 타당성을 확인하였다.

• 한국정밀공학회지
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• 제28권11호
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• pp.1279-1287
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• 2011

Weather strip is a functional component of a car body and doors for leaking protection, isolating outside noise and vibration reduction. Insert metal inserted to the weather strip plays a key role to keep the shape of the weather strip and increase its strength. Insert metal is mainly produced by a press process, which has low productivity and 40% material loss due to the scraps. To solve the problems, a high-speed rolling process for manufacturing the insert metal of weather strip is being attempted. In this study, the insert metal is manufactured by a high-speed rolling process, and its process variables: reduction, relative velocity of rollers and the number of passes, are optimized by using the FEA and the actual tests. The prototype was manufactured by the optimal process.

• 한국정밀공학회지
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• 제29권6호
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• pp.613-620
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• 2012

Rails are subjected to damage from rolling contact fatigue, which leads to defects such as cracks. Rolling contact fatigue damages on the surface of rail such as head check, squats are one of growing problems. Another form of rail surface damage, known as "Ballast imprint" has become apparent. This form of damage is associated with ballast particles becoming trapped between the wheel and the surface of rail. These defects are still one of the key reasons for rail maintenance and replacement. In this study, we have investigated whether the ballast imprint is an initiator of head check type cracks and effect of defect size using Finite element analysis. The FE analysis were used to investigate stresses and strains in subsurface of defects according to variation of defect size. Based on loading cycles obtained from FE analysis, fatigue analysis for each point was carried out.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 B
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• pp.1230-1232
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• 2000

To reduce harmonics in the AC line and achieve a unit power factor, A 4 paralled single phase PWM AC/DC converter has been proposed. In this paper, the coupling components are derived analytically from PWM converter input transformer model and control scheme to solve this problem is proposed. Unit power factor was obtained and the AC-side current harmonics were reduced. Simulation results show the usefulness of the proposed method and applicability to PWM converter in auxiliary block of high speed train.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.1109-1114
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• 2005

The rolling contact fatigue of wheels for high speed trains is a matter of increasing importance. The wheel damages from fatigue crack makes noise up and safety down. RCF-casued accidents cause traffic congestion and economical costs as well as personal injuries. In this study, we examine the rolling contact fatigue of wheels for power car running at 300km/h. Using the results of multi-body dynamic analysis and the proposed procedure of Ekberg, we calculate the fatigue index of surface-initiated fatigue, subsurface-initiated fatigue and fatigue initiated at deep material defects. As a result. the fatigue index shows us whether fatigue will appear and in which form. In addition, we present Shakedown map on surface-initiated fatigue.

• Tribology and Lubricants
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• 제17권2호
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• pp.138-145
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• 2001

The rolling piston type rotary compressor has been widely used for refrigeration and air-conditioning systems due to its compactness and high-speed operation. The present analysis is a part of research program directed toward maximizing these advantages of refrigerant compressors. The study of lubrication characteristics in the critical sliding component is essential for the design of refrigerant compressors. Therefore, theoretical investigation of the lubrication characteristics of a rotary compressor used for refrigeration and air-conditioning systems is studied. Newton-Raphson method is used for the partial elastohydrodynamic lubrication analysis between vane and rolling piston in the rotary compressor. The results show that the rotational speed of a shaft and the discharge pressure influence significantly the friction force and the energy loss between vane and rolling piston.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1996년도 제24회 춘계학술대회
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• pp.133-141
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• 1996

The rolling piston type rotary compressor has become one of the most successful types because of its compactness and high-speed operation. The analysis described here is part of a research program directed toward maximising these advantages in refrigerant compressors. The study of lubrication characteristics in the critical sliding component is essential for the design of refrigerant compressors. Therefore, theoretical investigation of the lubrication characteristics of rotary compressor for refrigeration & air-conditioning system is studied. And the Newton-Raphson method is used for the EHI. analysis between vane and rolling piston in the rotary compressor. The results show that the rotational speed of shaft and the discharge pressure have an important effect upon the friction force and the energy loss between vane and rolling piston. This results give important basic data for the further lubrication analysis and design of the rotary compressor.

• 한국철도학회논문집
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• 제8권5호
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• pp.477-482
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• 2005

Through a year's commercial operation, Korea High Speed Railway has solved defectives from several breakages at the beginning and is going into the stage of stable operation. Among issues, wheel wear becomes a matter of primary concerns in view of vehicle's stability and maintenance. It was understood as above that wear status has been improved in the test by which railway system including vehicles and tracks was stabilized during a year's commercial operation, comparing to that with excessive wear in the trial operation prior to opening to the public. To make out wheel's wear status and characteristics of equivalent conicity at present when the service has been introduced a year ago and the average cumulative mileage of vehicles reach almost 500,000km, wheel's wear types were analyzed with the current vehicles in service.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.642-646
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• 2008

Signaling system, for which ensuring safe train operation, must be a fail-safe system with higher reliability and safety. TCS has made significant improvements both on signaling system, from relay based ground signaling system to computer based on-board system, and on driving mode, form low speed and low density driving to TCS supporting high speed and high density driving. In addition, TCS has been applied to rolling stock with a wide variety of context according to the characteristics of rolling stock or railway infrastructure. In this paper, therefore, we confirmed the basic concept of ATC system and analyzed its development process in technology context via referencing international cases and ATC systems introduced and applied in Korea. Based on those analyses, we suggested the new TCS development strategy for its suitable application to high speed line, conventional line and metro, and we also provided technical considerations related to TCS application.