• International Journal of Railway
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• 제1권3호
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• pp.89-93
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• 2008

Reliability of onboard power supply systems on rolling stock is a very important issue for the railway operator. While a failure of the HVAC supply results in a loss of comfort for the passengers, a failure of the supply for air compressors or for the traction cooling systems results in towing the train. This is, looking at the required availability of a train, not acceptable. An active redundancy concept for the onboard power supply maximizes the availability of the system. This paper describes such a system under the aspect of $\cdot$ Weight reduction $\cdot$ Continuous operation when changing from normal to redundant operation $\cdot$ Flexibility in train design.

• 소음진동
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• 제7권6호
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• pp.1001-1006
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• 1997

Railroad noise is one of the main causes of environmental impact. Whenever a new railroad line is planned or a housing project near an existing railroad is proposed, an estimate of the relevant noise levels is usually required. For this, it is necessary to quantify those paramters that affect the railroad noise. This paper presents an accurate prediction of railroad noise.

• Journal of Mechanical Science and Technology
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• 제18권7호
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• pp.1074-1085
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• 2004

There are many intermediate web guides in cold rolling mills process such as CRM (cold rolling mill), CGL (continuous galvanizing line), EGL (electrical galvanizing line) and so on. The main functions of the web guides are to adjust the center line of the web (strip) to the center line of the steel process. So they are called CPC (center position control). Rapid process speed cause large deviation between the center position of the strip and the process line. Too much deviation is not desirable. So the difference between the center position of the strip and the process line should be compensated. In general, the center position control of the web is obtained by the hydraulic driver and electrical controller. In this paper, we propose modelling and several controller designs for web-guide systems. We model the web and guide by using geometrical relations of the guide ignored the mass and stiffness of the web. To control the systems, we propose PID controllers with their gains tuned by the Ziegler-Nichols method, the H$\_$$\infty$/ controller model-matching method, and the coefficient diagram method (CDM). CDM is modified for high order systems. The results are verified by computer simulations.

• 소성∙가공
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• 제21권1호
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• pp.58-66
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• 2012

The work roll surface temperature rises and falls repetitively during hot slab rolling because the work roll surface is cooled continuously by water. This study focused on Std. No. 7 to determine a cooling method which significantly reduces the tangential tensile stresses on the work roll surface of the hot slab mill at Hyundai Steel Co. in Korea. A series of finite element analyses were performed to compute the temperature distribution and the tensile stresses in the circumferential direction of the work roll. The virtual slab model was used to reduce the run time considerably by assigning a high temperature to the virtual slab. Except for the heat generated by plastic deformation, this is equivalent to the hot rolling condition that a high temperature slab (material) would experience when in contact with the work rolls. Results showed that when the virtual slab model was coupled with FE analysis, the run time was found to be reduced from 2000 hours to 70 hours. When the work roll surface cooled with a certain on-off patter of water spray, the magnitude of the tangential stresses on the work rolls were decreased by 54.1%, in comparison with those cooled by continuous water spraying. Savings of up to 83.3% in water usage are possible if the proposed water cooling method is adopted.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1998년도 봄 학술발표회 논문집
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• pp.433-440
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• 1998

For many decades, railroad technology was used to set up tracks with jointed rails and lengths in accordance with rolling and handling technology. The joints lead to drawbacks in the track and in controlling rising maintenance costs. So, railroad engineers became interested in eliminating joints to increase loads, speeds and improvements in rolling, welding, and fastening technology. Continuous welded rail(CWR) track has many advantages over the conventional jointed-rail track. In the case of the elimination of rail joints, it may cause the track to be suddenly and laterally buckled by thermal forces and vehicle load. Thermal forces are caused by an increase in the temperature of railway track. For many years, many analytical and experimental investigations have been conducted to improve the safety of CWR track by various research center in many country. In this paper, CWR track model and CWRB program is developed for buckling analysis using finite element method(FEM). The finite element discretization is used for a rail element with a total of 14 degrees of freedom. The stiffness of the fasteners, tie, and ballast bed is included by a set of spring elements. The investigation on the buckling modes and temperature of CWR track is presented in this paper

• 대한산업공학회지
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• 제24권4호
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• pp.649-660
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• 1998

Steel making in Mini Mill consists of three major processing stages: molten steel making in an electric arc fuenace, slab casting in a continuous caster, and hot rolling in a finishing mill. Each processing stage has its own lot grouping criterion. However, these criteria in three stages are conflicting with each other. Therefore, delveloping on efficient lot grouping algorithm to enhance the overall productivity of the Mini Mill is an extremely difficult task. The algorithm proposed in this paper is divided into three steps hierarchically: change grouping, cast grouping, and roll grouping. An efficient charge grouping heuristic is developed by exploiting the characteristics of the orders, the processing constraints and the requirements for the downstream stages. In order to maximaize the productivity of the continuous casters, each cast must contain as many charges as possible. Based on the constraint satisfaction problem technique, an efficient cast grouping heuristic is developed. Each roll consists of two casts satisfying the constraints for rolling. The roll grouping problem is formulated as a weighted non-bipartite matching problem, and an optimal roll grouping algorithm is developed. The proposed algorithm is programmed with C language and tested on a SUN Workstation with real data obtained from the H steel works. Through the computational experiment, the algorithm is verified to yield quite satisfactory solutions within a few minutes.

• 한국정밀공학회지
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• 제29권6호
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• pp.600-606
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• 2012

Upon investigation of the damaged wheels for high speed train it was determined that the damage was caused by rolling contact fatigue during operation of train. The major problems that railway vehicle system using wheel-rail has to face during operation of railway vehicle are rolling contact fatigue, cracks in wheels, cracks in rails and wheel-rail profile wear. If these deficiencies are not controlled at early stages the huge economical problems due to unexpected maintenance cost in railway vehicle can be happened. Also, If the accurate knowledge of contact conditions between wheel and rail can be evaluated, the damage of wheel can be prevented and the maintenance operation can save money. This paper presents the applicability of electro-magnetic technique to the detection and sizing of defects in wheel. Under the condition of continuous rolling contact fatigue the damage of wheel has continuously monitored using the applied sensor. It was shown that the usefulness of the applied sensor was verified by twin disc test and the measured damaged sizes showed good agreement with the damaged sizes estimated by electro-magnetic technique.

• 대한기계학회논문집A
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• 제36권4호
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• pp.429-435
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• 2012

압연공정 중에 작업롤은 스트립과의 지속적인 마찰에 의해 마모가 발생하여, 질량 불평형이 발생하게 된다. 이러한 작업롤의 질량 불평형을 고려한 압연기의 수학적 모델을 제안하였고, 이 모델은 실험에 의해 검증되었다. 작업롤은 편심을 가진 강체 로터로 가정되어, 질량 불평형의 채터 진동에 대한 영향을 분석하였다. 스핀들의 준평형 해석을 통해 계산된 조인트 힘은 압연기의 작업롤에 외력으로 작용시켰다. 압연기의 운동방정식을 직접적분법으로 풀어 과도 응답을 얻고 주파수 분석을 수행하였다. 편심은 수직 방향의 진동보다 수평 방향의 진동에 더 큰 영향을 끼쳤는데, 작업롤 반경의 1%의 편심거리도 수평 방향 채터 주파수의 진폭을 크게 상승시킬 수 있다는 것을 확인하였다.

• 시스템엔지니어링학술지
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• 제12권1호
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• pp.113-120
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• 2016

Steel in a continuous reheat furnace is heated to higher temperature to be treated in the rolling steel process. Due to this reason the continuous reheat furnace system requires an optimal control system to adjust the temperature inside the furnace. Level 2 control systems for continuous reheat furnaces generate automatic heating set points for the level 1 system of the furnace based on the mathematical thermal model which can give a good estimation of steel heating inside the furnace and is used to adjust heating requirements to optimize furnace combustion. For the current study the analytic methodology based on the design procedure from the systems engineering to develop new level 2 control system of a continuous reheat furnace was proposed. The system analysis and the requirements of the level 2 control system were derived using the unified modeling language (UML) 2.0, and the design of database and the graphic user interface (GUI) for the level 2 control system were conducted.

• 소성∙가공
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• 제12권1호
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• pp.43-48
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• 2003

The strain state during the continuous confined strip shearing (CCSS) based on ECAP was tackled by means of a two-dimensional FEM analysis. The deformation of AA 1100 sheet in the CCSS apparatus was composed of three distinct processes of rolling, bending and shearing. The pronounced difference in the friction conditions on the upper and lower roll surfaces led to the different variation of the strain component ${epsilon}_13$ throughout the thickness of the aluminum sheet. Strain accompanying bending was negligible because of a large radius of curvature. The shear deformation was concentrated at the corner of the CCSSchannel where the abrupt change in the direction of material flow occurred. The process variables involving the CCSS-die design and frictions between tools and strip influenced the evolution of shear strains during CCSS.