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설계하중 및 통과톤수를 고려한 유도상 아스팔트 궤도의 내구수명 예측
이성혁(S.H. Lee),이진욱(J.W. Lee),이현민(H.M. Lee) 한국철도학회 2014 한국철도학회 학술발표대회논문집 Vol.2014 No.10
유도상 아스팔트 궤도는 강화노반 상부에 부설된 아스팔트 콘크리트 층의 열차하중 분산효과에 의해 강화노반 두께를 감소시킬 수 있으며, 빗물 침투방지로 인한 노반부의 강도저하와 연약화 방지 효과, 노반 분니 방지 및 동상방지 등 다양한 장점을 가지고 있다. 이러한 장점으로 유도상 아스팔트 궤도는 미국을 비롯한 유럽 및 일본 등에서 널리 사용되고 있으며 국내에서도 도입을 위한 연구가 진행 중이다. 본 논문은 유도상 아스팔트 궤도의 적용성을 평가하기 위한 기초 연구로서 누적통과톤수를 주요 변수로 하여 아스팔트 콘크리트층의 존재에 의한 강화노반 두께 저감 가능성과 설계수명에 미치는 영향을 검토하였다. Reducing the thickness of reinforced roadbed is possible for ballasted asphalt track, due to the train-load distribution effect of asphalt concrete layer constructed on the top of reinforced roadbed. Including the advantages against mud pumping and heaving, the ballasted asphalt track also have the great merits in preventing the strength reduction of roadbed and its softening by prohibiting raindrop penetration. The virtues have made its widespread adoption in many countries in Europe as well as the USA and Japan. Research on introducing the ballasted asphalt track is on-going presently in Korea to put it into practice. This paper, as a basic research to evaluate the applicability of the ballasted asphalt track, examined the possibility of reducing the thickness of reinforced roadbed under the asphalt concrete layer and its design life, with main variables being accumulated passing tonnage.
아스팔트 및 강화노반의 두께 변화에 따른 아스팔트 직결궤도의 내구수명 평가 기초연구
이현민(H.M. Lee),이성혁(S.H. Lee),이진욱(J.W. Lee),조용성(Y.S. Cho) 한국철도학회 2014 한국철도학회 학술발표대회논문집 Vol.2014 No.10
아스팔트 직결궤도는 평탄성 확보가 쉽고 별도의 충전층이 없이 신속한 시공이 가능하다. 또한 선로유실과 지반침하 등의 문제 발생 시 신속히 유지보수 할 수 있는 장점이 있다. 독일의 경우 베를린-하노버 구간의 아스팔트 직결궤도(ATD궤도)는 부설 이후 20년간 유지보수가 불필요하고 우수한 소음저감효과가 있는 것으로 보고하고 있다. 아스팔트 직결궤도는 열차하중이 침목 또는 패널로부터 아스팔트 노반에 직접 전달되는 구조로서 아스팔트 콘크리트 층의 두께 변화에 따라 상부노반에 작용하는 응력 및 아스팔트 노반 하부 변형률이 내구수명에 큰 영향을 미칠 것으로 예상된다. 따라서 본 논문에서는 현재 개발되어 있는 아스팔트 직결궤도용 광폭 침목을 이용하여 아스팔트노반 및 강화노반의 두께 변화가 강화노반에 미치는 영향을 분석하고 목표 설계수명을 평가하고자 하였다. Directly fastened asphalt track is easy to secure flatness and possible to construct quickly without any special filler layer. It also has an advantage of maintaining and repairing immediately in case of track loss or settlement. Directly fastened asphalt track (ATD track) between Berlin and Hanover in Germany is reported that its maintenance has been unnecessary for 20 years after construction. The track is also noted for its excellence of noise reduction. Directly fastened asphalt track transfers train load directly to asphalt roadbed through sleepers or panels. According to the thickness of asphalt concrete layer, therefore, the stress acting on upper roadbed and the strain of lower asphalt roadbed are expected to have a big effect on its design life. In this respect, this paper focused on the effect of the asphalt and reinforced roadbed layer thickness on reinforced roadbed and the evaluation of its service life using currently available wider sleepers for directly fastened asphalt track.
수정된 CIP 방법을 이용한 벽면 충돌 후 액적의 퍼짐 현상에 대한 수치해석 연구
손소연(S.Y. Son),고권현(G.H. Ko),이성혁(S.H. Lee),유홍선(H.S. Ryou) 한국전산유체공학회 2010 한국전산유체공학회지 Vol.15 No.4
Interface tracking of two phase is significant to analyze multi-phase phenomena. The VOF(Volume of Fluid) and level set are well known interface tracking method. However, they have limitations to solve compressible flow and incompressible flow at the same time. ClP(Cubic Interpolate Propagation) method is appropriate for considering compressible and incompressible flow at once by solving the governing equation which is divided up into advection and non-advection term. In this article, we analyze the droplet impingement according to various We number using improved ClP method which treats nonlinear term once more comparison with original ClP method. Furthermore, we compare spread radius after droplet impingement on the wall with the experimental data and original ClP method. The result using improved ClP method shows the better result of the experiments, comparison with result of original ClP method, and it reduces the mass conservation error which is generated in the numerical analysis comparison with original ClP method.
수정된 CIP방법을 이용한 벽면 충돌 후 액적의 퍼짐 현상에 대한 수치해석 연구
손소연(S.Y. Son),고권현(G.H. Ko),이성혁(S.H. LEE),유홍선(H.S. Ryou) 한국전산유체공학회 2010 한국전산유체공학회 학술대회논문집 Vol.2010 No.5
Interface tracking of two phase is significant to analyze multi-phase phenomena. The VOF(Volume of Fluid) and level set are well known interface tracking method. However, they have limitations to solve compressible flow and incompressible flow at the same time. CIP(Cubic Interpolate Propagation) method is appropriate for considering compressible and incompressible flow at once by solving the governing equation which is divided up into advection and non-advection term. In this article, we analyze the droplet impingement according to various We number using improved CIP method which treats nonlinear term once more comparison with original CIP method. Furthermore, we compare spread radius after droplet impingement on the wall with the experimental data and original CIP method. The result using improved CIP method shows the better result of the experiments, comparison with result of original CIP method, and it reduces the mass conservation error which is generated in the numerical analysis comparison with original CIP method.
미세 딤플 가공 표면의 수력학적 윤활특성에 대한 수치해석 연구
홍사훈(S.H. Hong),이재봉(J.B. Lee),조민행(M.H. Cho),이성혁(S.H. Lee) 한국전산유체공학회 2009 한국전산유체공학회 학술대회논문집 Vol.2009 No.4
Recently, the manufacturing of micro-cavity by means of laser surface texturing (LST) technique and low friction study by the LST have been in great progress. Most of current works have been dealing with the effect of cavity on Fiction and wear. The main objective of the present study was to investigate numerically two-dimensional lubrication characteristics of micro-dimple shapes fabricated on solid surfaces, and this study utilized the commercial CFD code (Fluent V.6.3). For the evaluation, preliminary simulation was conducted and numerical predictions were compared with the analytic solution obtained from the Reynolds's equation. Mainly, the present study investigated the influence of dimple depth, pattern shapes, and film thickness on lubrication characteristics related to the reduction of friction. It is found that the existence of micro-dimpled surface makes it possible to substantially reduce the Fiction forces exerted on the surfaces. In particular, substantial decrease in shear stresses was observed as the lubricant film thickness decreases. For instance, in the case of the film thickness of 0.01 ㎜, the estimated shear stress decreases up to about 40%. It indicates that the film thickness would be important factor in designing the micro-dimpled surfaces. Furthermore, it was observed that such a optimum dimple depth would be present because the dimple depth larger than the optimum value did no longer affect the reduction in shear stresses.
정상기(Chung S.G),백남욱(Baek N.W),김연수(Kim Y.S),이성혁(Lee S.H),이한민(Lee H.M) 한국철도학회 2004 한국철도학회 학술발표대회논문집 Vol.- No.-
In DC power distribution system for urban rail transits potential relay, 64P, is used to detect the ground faults. The problem with this 64P is that though it detects the ground fault it cannot identify the faulted region. Therefore the faulted region cannot be isolated properly. It could results in power loss of the trains on the healthy regions and the safety of the passengers in the trains could be affected adversely. A new ground fault protective relaying scheme that can identify the faulted region is presented in this paper. The new concept uses the current differential scheme and the permissive scheme to identify the faulted region correctly. A device with similar characteristic to the arrestor is adapted to use the current relay for the ground fault detection. The role of the device is to block the ground leakage current in normal operating condition and enable the ground fault current to flow in ground fault condition. The algorithm of the new relay and the effect of the newly adapted device in the new relaying scheme are discussed.