• 제목/요약/키워드: 인발속도

검색결과 29건 처리시간 0.027초

Structural Analysis of Cheju-style Plastic Greenhouse Model for Crop Growing Based on the Wind Load (풍하중을 고려한 제주형 작물재배용 비닐하우스모델의 구조해석)

  • 민창식;김용호;권기린
    • Journal of Bio-Environment Control
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    • 제7권3호
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    • pp.181-190
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    • 1998
  • An elastic analysis under wind load was performed for the double layered plastic greenhouse model developed particularly for minimizing damages under typhoons at Cheju Citrus Research institute in Seagipo city. General EVA film was used for the inner covering and the developed special film which would break the wind pressure down was used for the outer covering. The wind tunnel test showed this special film reduced the wind speed up to 86 to 98% under well controlled situation. Based on the elastic analysis performed in the study, the behavior of the greenhouse was changed significantly due to the boundary conditions. Not like other researchers before we applied dead load of the concrete support to the ground pipe and fixed support boundary conditions at the 4 corner pipes. The analysis shows that the greenhouse was lifted and pulled the pipe out of the ground due to the sucking wind pressure. The behavior of the greenhouse was quite similar to that one real greenhouse failure. Therefore, not only we need to find the realistic boundary conditions for the supports, but also need to find how to rest the pipe supports on the ground without economic loss.

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An Analysis for Drawing of Strip by UBET with Rigid Elements (강체요소를 이용한 인발 공정의 상계요소 해석)

  • Choi, Il-Kuk;Choi, Young;Hur, Kwan-Do
    • Proceedings of the KSME Conference
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    • 대한기계학회 2001년도 춘계학술대회논문집C
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    • pp.598-603
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    • 2001
  • For metal forming analysis, upper-bound solution is practical method because the solution is overestimated. It is limited to determine stresses on tools by using upper-bound solution. In this study, new scheme to calculate stresses on tools based on upper bound solution is proposed. To verify the proposed scheme, plane strain drawing has been considered. The stresses on tools obtained by the proposed scheme are compared with results of rigid plastic FEM. And the stresses on tools have been determined by the proposed scheme in the forging within plane strain deformation.

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소성가공에서 Tribology

  • 오박균
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 한국윤활학회 1988년도 제7회 학술강연회초록집
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    • pp.1-11
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    • 1988
  • Tribology라는 용어는 마찰, 마모, 윤활의 과학, 기술을 한마디로 나타내는 말이다. 우리들의 일상생홀, 산업활동, 특히 소성가공에서 Tribology의 역활의 중요성은 새삼 강조할 필요가 없다. 소성가공에서 가공방식, 공구, 소재, 온도, 속도에는 무수한 조합이 있고, 마찰-마모-윤활의 상효연관 또한 복잡하다. 역학, 열전달, 물리학, 화학적과정이 동시에 상호작용을 하면서 진행하는 이 시스템에서는 크게는 공작기계로부터 작게는 micron정도의 표면과 윤활막 뿐만 아니라, 경우에 따라서는 ${\AA}$ 정도의 정체불명체가 결정적인 역활을 한다. 본 고에서는 냉간압연, 단조, 인발등에 Tribology를 응용하는 입장에서 Tribology system의 일부를 공구와 재료의 윤활제를 개재한 micro 접촉상황을 중심으로 분류정리하고, 이것과 공업적 소성가공에서 공구 - 재료접촉면현상과 그 연계를 가능한 한 이해하기 쉽게 서술하였다. 이를 통하여 소성가공기술자 및 연구자가 소성가공의 목적을 달성하는 가운데, Tribology 적으로 양호한 결과를 경제적으로 얻고자하는 시행, 개발, 연구에 대해 도움이 되고자 한다.

Design and evaluation of renovated NSI T/O PC sleeper (개량형 NSI 분기기용 PC침목 설계와 성능평가)

  • Park, Choon-Bok;Kwon, Ho-Jin;Lee, Young-Sou;Yoon, Byung-Hyun;Shin, Won-Sun
    • Proceedings of the KSR Conference
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    • 한국철도학회 2007년도 춘계학술대회 논문집
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    • pp.1129-1137
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    • 2007
  • 50kg NSI PCT(Prestress Concrete Timber, sleeper) is developed for the purpose of low maintenance cost, Extend life cycle, Track stability, Friendly Environment, Good running quality. In this study, as a part of research which is to make renovated NSI turnout, the main objective of this study is the optimization of PC sleeper's section, the number of PS tension wire. For this purpose, the finite element analysis was conducted to evaluate the serviceability and the safety of NSI PC sleeper developed.

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A Protection Capacity Evaluation of Vessel Protective Structures by Quasi-Static Collision Analysis (준정적 충돌해석을 통한 선박충돌방공호의 방호능력평가)

  • Lee, Gye-Hee
    • Journal of the Computational Structural Engineering Institute of Korea
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    • 제24권6호
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    • pp.691-697
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    • 2011
  • In this study, the vessel collision protective structure and the vessel were modeled numerically and the quasi-static collision analysis was performed to evaluate the maximum protection capacity. In the modeling process of protective structure, the nonlinear behaviors of structure and the supporting conditions of ground including pull-out action were considered. In that of collision vessel, the bow of vessel was modeled precisely, because of the nonlinear behaviors were concentrated on it. For the efficient analysis, the mass scaling scheme was applied, also. To evaluate the differences and efficiency, the dynamic analyses were performed for the same model, additionally. Based on the obtained energy dissipation curves of the structure and the vessel, the moment that the collision force affected to the bridge substructures was determined and the maximum allowable collision velocity was evaluated. Because of the energy dissipation bound can be recognized clearly, this scheme can be used efficient in engineering work.

Numerical Analysis on Effect of Permeability and Reinforcement Length (Drainage Path) in Reinforced Soil (보강토에서의 투수성과 보강재길이(배수거리)의 영향에 대한 수치해석)

  • Lee, Hong-Sung;Hwang, Young-Cheol
    • Journal of the Korean GEO-environmental Society
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    • 제8권3호
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    • pp.59-65
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    • 2007
  • Excess pore pressures in low permeability soils may not dissipate quickly enough and decrease the effective stresses inside the soil, which in turn may cause a reduction of the shear strength at the interface between the soil and the reinforcement in MSE walls. For this condition the dissipation rate of pore pressures is most important and it varies depending on wall size, permeability of the backfill, and reinforcement length. In this paper, a series of numerical analysis has been performed to investigate the effect of those factors. The results show that for soils with a permeability lower than $10^{-3}cm/sec$, the consolidation time gradually increases. The increase in consolidation time indicates the decrease in effective stress thus it will result in decrease in pullout capacity of the reinforcement as verified by the numerical analyses. It is also observed that larger consolidation time is required for longer reinforcement length (longer drainage path).

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Modeling and Analysis of Dynamic Characteristic for Bundle Fluid System (집속체 유동계의 모델링과 운동 특성해석)

  • Kim, Jong-Sung;Heo, Yu;Kim, Yoon-Hyuk
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 한국정밀공학회 2003년도 춘계학술대회 논문집
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    • pp.1643-1646
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    • 2003
  • Drawing is a mechanical operation that attenuates thick material to an appropriate thickness for the next processing or end usage. When the input material has the form of a bundle or bundles made of very thin and long shaped wire or fibers, this attenuation operation is called "bundle drawing" or "drafting" Drafting is being used widely in manufacturing staple yarns. which is indispensable for the textile industry. However, the bundle processed by this operation undertake more or less defects in the evenness of linear density. Such irregularities cause many problems not only for the product quality but also for the efficiency of the next successive processes. Since long there have been many researches tying to find out factors affecting the irregularity of linear desity, to obtain optimal drafting conditions, to develop efficient measuring and analysis methods of linear density of bundle, etc., but there exists yet no fundamental equation describing the dynamic behavior of the flowing bundle during processing. In this research a mathematical model for the dynamic behavior of the bundle fluid is to be set up on the basis of general physical lows representing physical variables, i.e. linear density and velocity as the dynamic state of bundle. The conservation of mass and momentum balance was applied to the fluid field of bundle. while the movement of′ individual material was taken into account. The constitutive model relating the surface force and the deformation of bundle was introduced by considering a representative prodedure that stands for the bundle movement. Then a fundamental equations system could be simplified considering a steady state of the process. On the basis of the simplified model, the simulation was performed and the results could be confirmed by the experiments under various conditions.

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An Evaluation of Solid Removal Efficiency in Coagulation System for Treating Combined Sewer Overflows by Return Sludge (CSOs처리를 위한 응집침전시스템에서 슬러지 반송에 의한 고형물 처리효율평가)

  • Ha, Sung-Ryong;Lee, Seung-Chul
    • Journal of Korean Society of Environmental Engineers
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    • 제35권3호
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    • pp.171-178
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    • 2013
  • In this study, the sludge that occurs in the initial operation of coagulation system developed for the treatment of CSOs were returned to the flocculation reactor. The purposes of this study were to analyze the Characteristics of flocs that are generated through the recycling sludge and settling characteristics of sludge, and to evaluate the possibility that high concentrations of particulate matter in the initial inflow of CSOs could be used as an weighted coagulant additive. As a result, the concentration of treated CSOs pollutants at the beginning of the CSOs influent with a large amount of particulate matter over 20 ${\mu}m$ was low, after gradually increasing the concentrations of them. The flocs generated from the sludge return were similar in size compared to flocs generated through injection of micro sands, and settling velocity in case of return sludge injection was decreased from 55.1 cm/min to 21.5 cm/min. SVI value of the sludge accumulated at the bottom of the sedimentation tank was 72, and settled sludge volume decreased rapidly due to the consolidation of sludge to the time it takes to 10 minutes. these mean that sludge used for recycling has good settling characteristic. A condition of returned sludge which is 0.1% return of 0.3% extraction was formed in the balance of settlement and extraction. In this case, This condition was to be adequate to maintain the proper concentration such as 100~200 mg/L of TS and 50~100 mg/L of VS in the flocculation reactor. The usage of the return sludge containing particulate matters of CSOs as an weighted coagulant additive was able to secure a stable treated water quality despite the change of influent water quality dynamically. Furthermore, it can be expected to reduce the alum dosage along with the sludge production.

Strength Performance Evaluation of Deck Using Reinforced Plastic Connector (강화플라스틱 연결구를 이용한 데크의 내력 성능평가)

  • Song, Yo-Jin;Jung, Hong-Ju;Lee, Dong-Heub;Kim, Kyung-Dae;Hong, Soon-Il
    • Journal of the Korean Wood Science and Technology
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    • 제41권1호
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    • pp.12-18
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    • 2013
  • Existing wood decks brings out negligent accident because fastener can be pulled-out by cyclic load of pedestrians. When deck and joist are connected, it also causes the problems, which are cracking of wood decks and rapid decay by material of fastener. In this study, strength property of deck unit using reinforced plastic connector made by domestic A company was evaluated. Southern yellow pine (Pinus palustris Miller) were used for deck material. Bending strength of deck units were implemented for fastener type and joist spacing (400, 600 mm). In the result, carbon steel screw into reinforced plastic connector was the best in average bending strength(Joist spacing : 400, 600 mm). In the result of bending strength for joist-width (40, 50, 70, 80 mm), the average maximum bending strength was measured when the joist spacing was 40 mm.