• 한국구조물진단유지관리공학회 논문집
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• 제18권1호
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• pp.19-30
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• 2014

본 연구에서는 강주탑 기부와 기초콘크리트 연결 구조에 대해서 국내에서 특수교량의 강주탑 기부 설계에 보편적으로 적용하고 있는 명석해협대교(明石海峽大橋) 시방기준과 비선형 FEM 해석결과를 비교하였다. 명석해협대교(明石海峽大橋) 시방기준은 1970년도에 만들어진 일본 기준으로 주탑 기부와 PS 강봉 및 기초콘크리트를 스프링으로 선형 모델링하여 설계하는 방법으로서 43년이 지난 지금까지도 간편성을 이유로 이 기준을 적용하고 있다. 그러나 비선형 FEM 해석결과의 비교를 통해 특수 장대교의 강주탑 기부의 해석 및 설계에 이 기준을 적용하는 것은 여러 가지 문제점이 있음을 알 수 있었으며, 풍하중, 지진하중에 주요하게 저항하면서도 다양한 부재들로 복잡하게 연결된 강주탑 기부에 대해서는 한계상태설계법으로 발전하려는 현 시대에 맞추어 실제 거동을 반영하는 비선형 FEM해석을 적용해야 할 것이다.

• Computers and Concrete
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• 제8권1호
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• pp.97-110
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• 2011

In this paper, FEM procedure is applied to the static and dynamic analyses of R/C structures. Simple R/C shell structure is solved by using FEM procedures and the experimental evaluations are performed to represent the applicability of FEM procedure to R/C structures. Also, R/C columns are analyzed numerically and experimentally. On the basis of these results, FEM procedures are applied to the R/C cooling tower structures assembled by huge R/C shell structure and a lot of discrete R/C columns. In this analysis, the parallel computing procedures are introduced into these analyses to reduce the computational effort. The dynamic performances of R/C cooling tower are also solved by the application of parallel computations as well. From the numerical analyses, the conventional FEM procedures combined with computational technologies enables us to design the huge R/C structures statically and dynamically.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 추계학술대회
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• pp.396-400
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• 2003

This paper has studied thermal characteristics of machine tool to develope high speed spindle and optimum design condidering the thermal deformation. Comparing the test data of temperature measurement and structural analysis data using FEM, we verifiedthe test validity and predicted thermal deformation, influence of spindle generation of heat, and established cooling system to prevent the thermal deformation. 1) The temperature rise of spindle system depends on increasing number of rotation and shows sudden doubling increment of number of rotation over 7,000rpm. 2) Oil jacket cooling can be effective cooling method below 8,000rpm but, over 8,000rpm, it shows the decrement of cooling effect. 3) Comparing FEM analysis results and revolution test results, we can confirmn approximate temperature change consequently, it is possible to simulate temperature rise and thermal distribution on the inside of spindle system. 4) We can confirm that simulated approach by FEM analysis can be effective method in thermal-appropriate design..

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.363-368
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• 2004

Maglev vehicles, which are levitated and propelled by electromagnets, often run on elevated guideways comprised of steel, aluminum and concrete. Therefore, an analysis of the dynamic interaction between the Maglev vehicle and the guideway is needed in the design of the critical speed, ride, controller design and weight reduction of the guideway. This study introduces a dynamic interaction simulation technique that applies FEM. The proposed method uses FEM to model the elevated guideway and the Maglev vehicle, which is different from conventional studies. Because the proposed method uses FEM, it is useful to calculate the deformation of the elevated guideway, the dynamic stress, and the motion of the vehicle. By applying the proposed method to an urban transit Maglev vehicle, UTM01, the dynamic response is simulated according to velocity increase and can be reviewed again. From the result of the study, we concluded that FEM simulation of the dynamic interaction between the maglev vehicle and the guideway is possible.

• Applied Microscopy
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• 제47권1호
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• pp.55-62
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• 2017

This paper describes experiments aimed at characterizing the behavior of field electron emitters fabricated by coating carbon fibers with epoxylite resin. Polyacrylonitrile carbon fibers of type VPR-19, thermally treated at $2,800^{\circ}C$, were used. Each was initially prepared in a "uncoated" state, by standard electro polishing and cleaning techniques, and was then examined in a scanning electron microscope. The fiber was then baked overnight in a field electron microscope (FEM) vacuum chamber. Current-voltage characteristics and FEM images were recorded on the following day or later. The fiber was then removed from the FEM, coated with resin, "cured" by baking, and replaced in the FEM. After another overnight bake, the FEM characterization measurements were repeated. The coated fibers had significantly better performance than uncoated fibers. This confirms the results of earlier experiments, and is thought to be due in part to the formation of a conducting channel in the resin over layer. For the coated fiber, lower voltages were needed to obtain the same emission current. The coated fibers have current-voltage characteristics that show smoother trends, with greater stability and repeatability. No switch-on phenomena were observed. In addition, the emission images on the phosphor-coated FEM screen were more concentrated, and hence brighter.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 C
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• pp.565-567
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• 2000

In this paper, the discharge characteristics of AC PDP, one of the leading technologies currently under development for large-area flat displays, is computed by using Finite Element Method(FEM) combined with Flux-corrected Transport(FCT) algorithm. Up to now, many simulations of AC PDP have been mainly done by Finite Difference Method(FDM). But we simulated the AC PDP by using FEM-FCT method which discretizes the region of interest with unstructured grids. FEM-FCT method can reduce the computational cost because of refining locally where the physical quantities have steep gradients and is more efficient in solving discharge problems, such as a AC PDP. Results are presented in Ne-Xe(4%) gas mixture for a gas pressure of 400 Torr and as the discharge proceeds, the space and time variations of the electron and ion densities, potential and wall charges on the dielectric are described. Results from our simulation by FEM-FCT are similar to those from simulation by FDM and are more efficient in computational cost reduction.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 A
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• pp.47-50
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• 1997

The FEM(Finite Element Method) can be used to analysis SRM(Switched Reluctance Motor) as it can account for the salient pole geometry of the stator and rotor and the nonlinear properties of the magnetic materials. However, FEM requirers a lot of computer memory and computing time because, the kind of SRM drivers is verity and the switching strategies are various for one SRM driver. In this paper we proposed the method of analysis of a SRM which results are similar to FEM and has very short computing time. The Inductance and torque for each phase current at each rotor position are calculated by using two-dimensional nonlinear FEM analysis. Using the look-up table of inductance and torque and the voltage equations of SRM we obtained the phase current and torque. To verify proposed algorithm, 3 phase 6/4 SRM is analysed and found a good agreement with FEM results. And computing time is about 1/1600 of the FEM analysis.

• 대한기계학회논문집 C: 기술과 교육
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• 제5권2호
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• pp.81-87
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• 2017

315Fr 컴프레서용 모터가 진동 기준을 초과하는 문제가 발생하였고 이를 해결하기 위한 FEM해석과 모드실험을 수행하였다. 먼저 자유단 조건하의 해석과 실험을 수행하여 해석을 위한 조건을 확인하였다. 해석을 위한 Mesh, 재질, 경계 조건을 검토하였다. 여기서 얻은 결과를 바탕으로 볼트가 고정된 상태의 FEM 해석과 모드 실험을 수행하여 진동의 원인을 확인하였다. 모드실험 결과 121.7Hz에 Rolling 모드가 있음을 확인하였고 해석을 통해서도 동일한 결과를 얻을 수 있었다. 이 결과를 바탕으로 진동 기준을 초과하는 원인은 120Hz에 존재하는 Rolling 운동과 2X, 2fl 가진 주파수의 공진에 의한 것임을 알게 되었다. 여기서 얻은 결과를 바탕으로 추후 시리즈 설계에 있어서는 시험 모델 제작이나 실험 없이 해석만으로 문제점을 예측하고 해결할 수 있는 기술을 보유하게 되었다.

• Tribology and Lubricants
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• 제22권3호
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• pp.119-126
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• 2006

In this paper, the contact behavior characteristics of a primary sealing components such as a seal ring and a seal seat has been presented for a small hydro-power turbine. Using the non-linear FEM analysis, the maximum temperature, the axial displacement, radial differences between a seal ring and a seal seat, and maximum contact normal stress have been analyzed for three optimized sealing profiles in which are designed based on the FEM analysis and Taguchi's experimental method. The three primary sealing profiles between a seal ring and a seal seat are strongly related to a leakage of a water for a hydro-power turbine and wear of a primary sealing component. The computed results show that the contact rubbing area between a seal ring and a seal seat is very important for reducing a friction heating and wear in a sealing gap, and increasing a contact normal stress in primary sealing components. Based on the FEM computation, models II and III in which have a small rubbing surface of seal rings show low dilatation of primary sealing components, and high normal contact stress between a seal ring and a seal seat. Thus, the FEM computed results recommend a short contacting width of a primary sealing component for reducing a leakage and thermal distortions, and expanding a seal life. This means that a conventional primary sealing component may be switched to a reduced sealing face of seal rings.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.318-321
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• 2005

In vibro-acoustic analysis, the commercial CAE tools, such as SYSNOISE, is usually used to take into account of the coupled effects of fluid acoustics and structural vibration. The acoustic field can be solved by either FEM or BEM, while the vibration field is usually solved by FEM. The interior or exterior acoustic problems with the coupled effects of the structural boundary could be solved by the commercial tools. The commercial tools, however, could not solve the problems in case that both the interior and exterior acoustic field is coupled with the structural boundary. In this paper, a realistic method based on FEM/BEM coupling scheme is presented to analyze the acoustic radiation from the internal source in a chamber to external acoustic field through elastic structural boundary. Several numerical examples are implemented to validate the developed program.