• 제목/요약/키워드: Static Equilibrium Analysis

검색결과 178건 처리시간 0.023초

플로팅 링 저널 베어링 정특성의 실험적 고찰 (Static Properties of Floating Ring Journal Bearings)

  • 송진대;양보석
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2006년도 춘계학술대회논문집
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    • pp.1150-1153
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    • 2006
  • Many commercial high speed and lightly loaded rotating machineries incorporate floating ring bearings (FRBs) owing to their low cost and reduced power losses. Many researchers have developed various analytical models to predict the performance and the stability of those rotor-bearing systems with FRBs. However, most of the models failed to predict stability of the rotor-bearing systems with FRBs. FRBs comprise two fluid films in series and the ratio of floating ring speed to journal speed reflects the equilibrium state of the two fluid films. Therefore the speed ratio is one of the main concerns in the analysis of FRBs. This paper provides the experimental results of the speed ratio which enables one to verify of the analysis model for FRBs.

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LIMIT ANALYSIS OF CONTINUOUS STRUCTURES USING MATHEMATICAL PROGRAMMING

  • Victor-A.Pulmano;Loi, Francis-Tin
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 1992년도 가을 학술발표회 논문집
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    • pp.7-19
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    • 1992
  • An efficient approach to limit analysis is presented whereby a continuous perfectly plastic structure is replaced by a discrete mathematical model. It is formulated as a mathematical programming problem using the static theorem of plasticity. The discretization is accomplished by writing the governing equilibrium equations in finite difference form, and is combined with piecewise linearization of the nonlinear yield curve, thus converting the formulation into a linear programming exercise. Examples of reported cases involving plates and shells are solved to illustrate the ease of application of the present method, its flexibility and accuracy - features which it make attractive to practising engineers.

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Non-conventional formulations for the finite element method

  • de Freitas, J.A. Teixeira;de Almeida, J.P. Moitinho;Peraira, E.M.B. Ribeiro
    • Structural Engineering and Mechanics
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    • 제4권6호
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    • pp.655-678
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    • 1996
  • The paper reports on alternative hybrid/mixed formulations being developed by the Structural Analysis Research Group of Institute Superior T$\acute{e}$cnico. These formulations open the scope and increase the power of the finite element method by allowing different fields to be independently approximated, within certain consistency criteria, and by enhancing the use of a wide range of approximation functions. They have been applied to the analysis of 2-D problems, laminar structures and solids, using different constitutive relations, both in quasi-static and dynamic regimes. The fundamental properties of the formulations are identified and assessed and their performance is illustrated using simple, linear applications.

비선형설계모형을 이용한 대중교통요금구조평가 (A Nonlinear Programming Model for Evaluating Public Transit Fare Structure)

  • 조중래
    • 대한교통학회지
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    • 제7권2호
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    • pp.17-27
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    • 1989
  • A nonlinear programming model for evaluating public transit fare system is proposed. The model finds transit fare level and the structure that maximizes gross fare-box revenue subject to constraints on minimum ridership and the form of the fare equations. It is assumed that the demand for transit is a function of fare and its own-fare elasticity. It is assumed that the demand for transit is a function of fare and its own-fare elasticity. It is also assumed that the conditions including fare of the other modes are unchanged ; i.e., partial equilibrium. Empirical study has been performed for the case of Seoul subway system. This study includes an analysis of fare structure ; flat system and distance-based fare system. Sensitivity and comperative static analysis for elasticity has been also demonstrated.

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사각형 판 유한 요소들의 정적 성능 비교 분석 I (Comparative Study on the Performance of Quadrilateral Plate Elements for the static Analysis of Limear Elastic structures( I );Displacements)

  • 이병채;이용주
    • 전산구조공학
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    • 제3권4호
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    • pp.91-104
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    • 1990
  • 사각형 판 유한요소의 정적 성능을 여러 가지 문제에 대한 수치 실험을 통해 비교 분석하였다. Kirchhoff이론과 Mindlin이론에 근거한 변위요소, 평형요소, Mixed 또는 Hybrid요소들을 대상으로 문헌조사를 통해 우수요소를 선정하였으며 사각형 판 문제, 마름모형 판 문제, 원형 판 문제, 외팔보형 판 문제를 다양한 격자, 경계조건에 대해 풀어 해를 비교하였다. Kirchhoff요소에서는 12자유도요소로 Armanios의 요소, 24 자유도 요소로 Watkins요소의 거동이 우수하였으나 전반적으로 Mindlin요소에 비해 거동이 떨어진다. Mindlin요소 중에서는 Hinton의 요소가 효율성, 수렴성, 신뢰성의 면에서 가장 우수하나 마름모형 판 문제나 뒤틀린 격자 문제등에서는 거동이 좋지 않으므로 계속 연구할 필요가 있다.

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Evaluation of vierendeel peripheral frame as supporting structural element for prevention of progressive collapse

  • Khaloo, Alireza;Omidi, Hossein
    • Steel and Composite Structures
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    • 제26권5호
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    • pp.549-556
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    • 2018
  • Progressive building collapse occurs when failure of a structural component leads to the failure and collapse of surrounding members, possibly promoting additional failure. Global system collapse will occur if the damaged system is unable to reach a new static equilibrium configuration. The most common type of primary failure which led to the progressive collapse phenomenon, is the sudden removal of a column by various factors. In this study, a method is proposed to prevent progressive collapse phenomena in structures subjected to removal of a single column. A vierendeel peripheral frame at roof level is used to redistribute the removed column's load on other columns of the structure. For analysis, quasi-static approach is used which considers various load combinations. This method, while economically affordable is easily applicable (also for new structures as well as for existing structures and without causing damage to their architectural requirements). Special emphasis is focused on the evolution of vertical displacements of column removal point. Even though additional stresses and displacements are experienced by removal of a structural load bearing column, the proposed method considerably reduces the displacement at the mentioned point and prevents the collapse of the structural frame.

Static Aeroelastic Response of Wing-Structures Accounting for In-Plane Cross-Section Deformation

  • Varello, Alberto;Lamberti, Alessandro;Carrera, Erasmo
    • International Journal of Aeronautical and Space Sciences
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    • 제14권4호
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    • pp.310-323
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    • 2013
  • In this paper, the aeroelastic static response of flexible wings with arbitrary cross-section geometry via a coupled CUF-XFLR5 approach is presented. Refined structural one-dimensional (1D) models, with a variable order of expansion for the displacement field, are developed on the basis of the Carrera Unified Formulation (CUF), taking into account cross-sectional deformability. A three-dimensional (3D) Panel Method is employed for the aerodynamic analysis, providing more accuracy with respect to the Vortex Lattice Method (VLM). A straight wing with an airfoil cross-section is modeled as a clamped beam, by means of the finite element method (FEM). Numerical results present the variation of wing aerodynamic parameters, and the equilibrium aeroelastic response is evaluated in terms of displacements and in-plane cross-section deformation. Aeroelastic coupled analyses are based on an iterative procedure, as well as a linear coupling approach for different free stream velocities. A convergent trend of displacements and aerodynamic coefficients is achieved as the structural model accuracy increases. Comparisons with 3D finite element solutions prove that an accurate description of the in-plane cross-section deformation is provided by the proposed 1D CUF model, through a significant reduction in computational cost.

탄성변형으로 인한 틸팅패드 저널베어링의 예압 변화 (Elastic Deformation Induced Preload Change in Tilting Pad Journal Bearing)

  • 이동현;서준호
    • Tribology and Lubricants
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    • 제39권3호
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    • pp.102-110
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    • 2023
  • This study aims to quantify the variation in the performance of a tilting pad journal bearing (TPJB) owing to the elastic deformation of its pad. To this end, we first defined a parameter, "elastic preload", and predicted the changes in the performance of the TPJB, as a function of the preload amount. We used the iso-viscosity Reynolds equation, which ignores the temperature rise due to viscous shear in thin films, and the resultant thermal deformation of the bearing structure. We employed a three-dimensional finite element model to predict the elastic deformation of the bearing pad, and a transient analysis, to converge to a static equilibrium condition of the flexible pads and journal. Conducting a modal coordinate transformation helped us avoid heavy computational issues arising from a mesh refinement in the three-dimensional finite element pad model. Moreover, we adopted the Hertzian contact model to predict the elastic deformation at the pivot location. With the aforementioned overall strategy, we predicted the performance changes owing to the elastic deformation of the pad under varying load conditions. From the results, we observed an increase in the preload due to the pad elastic deformation.

Glass Dissolution Rates From MCC-1 and Flow-Through Tests

  • Jeong, Seung-Young
    • 한국방사성폐기물학회:학술대회논문집
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    • 한국방사성폐기물학회 2004년도 학술논문집
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    • pp.257-258
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    • 2004
  • The dose from radionuclides released from high-level radioactive waste (HLW) glasses as they corrode must be taken into account when assessing the performance of a disposal system. In the performance assessment (PA) calculations conducted for the proposed Yucca Mountain, Nevada, disposal system, the release of radionuclides is conservatively assumed to occur at the same rate the glass matrix dissolves. A simple model was developed to calculate the glass dissolution rate of HLW glasses in these PA calculations [1]. For the PA calculations that were conducted for Site Recommendation, it was necessary to identify ranges of parameter values that bounded the dissolution rates of the wide range of HLW glass compositions that will be disposed. The values and ranges of the model parameters for the pH and temperature dependencies were extracted from the results of SPFT, static leach tests, and Soxhlet tests available in the literature. Static leach tests were conducted with a range of glass compositions to measure values for the glass composition parameter. The glass dissolution rate depends on temperature, pH, and the compositions of the glass and solution, The dissolution rate is calculated using Eq. 1: $rate{\;}={\;}k_{o}10^{(ph){\eta})}{\cdot}e^{(-Ea/RT)}{\cdot}(1-Q/K){\;}+{\;}k_{long}$ where $k_{0},\;{\eta}$ and Eaare the parameters for glass composition, pH, $\eta$ and temperature dependence, respectively, and R is the gas constant. The term (1-Q/K) is the affinity term, where Q is the ion activity product of the solution and K is the pseudo-equilibrium constant for the glass. Values of the parameters $k_{0},\;{\eta}\;and\;E_{a}$ are the parameters for glass composition, pH, and temperature dependence, respectively, and R is the gas constant. The term (1-Q/C) is the affinity term, where Q is the ion activity product of the solution and K is the pseudo-equilibrium constant for the glass. Values of the parameters $k_0$, and Ea are determined under test conditions where the value of Q is maintained near zero, so that the value of the affinity term remains near 1. The dissolution rate under conditions in which the value of the affinity term is near 1 is referred to as the forward rate. This is the highest dissolution rate that can occur at a particular pH and temperature. The value of the parameter K is determined from experiments in which the value of the ion activity product approaches the value of K. This results in a decrease in the value of the affinity term and the dissolution rate. The highly dilute solutions required to measure the forward rate and extract values for $k_0$, $\eta$, and Ea can be maintained by conducting dynamic tests in which the test solution is removed from the reaction cell and replaced with fresh solution. In the single-pass flow-through (PFT) test method, this is done by continuously pumping the test solution through the reaction cell. Alternatively, static tests can be conducted with sufficient solution volume that the solution concentrations of dissolved glass components do not increase significantly during the test. Both the SPFT and static tests can ve conducted for a wide range of pH values and temperatures. Both static and SPFt tests have short-comings. the SPFT test requires analysis of several solutions (typically 6-10) at each of several flow rates to determine the glass dissolution rate at each pH and temperature. As will be shown, the rate measured in an SPFt test depends on the solution flow rate. The solutions in static tests will eventually become concentrated enough to affect the dissolution rate. In both the SPFt and static test methods. a compromise is required between the need to minimize the effects of dissolved components on the dissolution rate and the need to attain solution concentrations that are high enough to analyze. In the paper, we compare the results of static leach tests and SPFT tests conducted with simple 5-component glass to confirm the equivalence of SPFT tests and static tests conducted with pH buffer solutions. Tests were conducted over the range pH values that are most relevant for waste glass disssolution in a disposal system. The glass and temperature used in the tests were selected to allow direct comparison with SPFT tests conducted previously. The ability to measure parameter values with more than one test method and an understanding of how the rate measured in each test is affected by various test parameters provides added confidence to the measured values. The dissolution rate of a simple 5-component glass was measured at pH values of 6.2, 8.3, and 9.6 and $70^{\circ}C$ using static tests and single-pass flow-through (SPFT) tests. Similar rates were measured with the two methods. However, the measured rates are about 10X higher than the rates measured previously for a glass having the same composition using an SPFT test method. Differences are attributed to effects of the solution flow rate on the glass dissolution reate and how the specific surface area of crushed glass is estimated. This comparison indicates the need to standardize the SPFT test procedure.

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새로운 연산가능일반균형모형을 이용한 온실가스 감축정책의 영향 분석 (New Computable General Equilibrium Analysis of the Effects of Greenhouse Gas Emissions Reduction Policies)

  • 한민수;문진영
    • 자원ㆍ환경경제연구
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    • 제30권2호
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    • pp.169-205
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    • 2021
  • 본 연구는 온실가스 감축정책이 세계경제에 미치는 영향을 정량적으로 분석하였다. 이를 위해서 생산에 따른 온실가스 배출, 온실가스 배출에 의한 비효용의 발생, 각국 정부의 온실가스 감축정책이라는 세 가지 요소를 포함하고 있는 다국가-다산업 정태적 연산가능일반균형모형을 개발하였다. 이렇게 개발된 모형의 파라미터 값을 추정하고 모형에 적용할 수 있는 가장 최근의 방법론(exact hat algebra)을 사용해서 모형의 해를 계산하였다. 모형의 예측에 따르면 국가별 개별적인(unilateral) 온실가스 감축정책의 강화는 해당 국가의 국내 생산과 탄소 배출을 감소시키지만, 생산이 다른 국가로 재배치되기 때문에 반드시 세계의 탄소 배출량을 감소시키지는 않는 것으로 나타났다. 반면 모든 주요국들이 동시에 OECD(2016)에서 제안된 강화된 감축정책을 추진할 경우에 전 세계의 온실가스 배출을 감소시킬 수 있는 것으로 나타났다. 우리분석결과는 온실가스 감축정책이 효과를 발휘하기 위해서는 주요국들의 조율된(aligned) 감축노력이 필요하다는 점을 시사한다.