• Title/Summary/Keyword: stiffness problem

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GEOMETRICALLY AND MATERIALLY NONLINEAR ANALYSIS FOR A COMPOSITE PRESSURE VESSEL

  • 도영대;김형근
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 1995.05a
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    • pp.141-153
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    • 1995
  • An incremental Total Lagrangian Formulation is implemented for the finite element analysis of laminated composite pressure vessel with consideration of the material and geometric nonlinearities. For large displacements/large rotations due to geometric nonlinearities, the incremental equations are derived using a quadratic approximation for the increment of the reference vectors in terms of the nodal rotation increments. This approach leads to a complete tangent stiffness matrix. For material nonlinearity, the analysis is performed by using the piecewise linear method, taking account of the nonlinear shear stress-strain relation. The results of numerical tests include the large deflection behavior of the selected composite shell problem. When compared with the previous analysis, tile results are in good agreement with them. As a practical example, filament wound pressure vessel is analyzed with consideration of the geometrically and materially nonlinearity. The numerical results agree fairly well with the existing experimental results.

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A study on the Effect of Aggregate Particle Shape on Property of Concrete (콘크리트용 부순 굵은 골재의 입형이 콘크리트의 물리적 성질에 미치는 영향에 관한 연구)

  • Seo Ki Won;Lee Wook Jae;Kim Hag Youn;Kim Nam Ho
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.11a
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    • pp.209-212
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    • 2004
  • Recent economic development caused a vast use of mineral resources in Korea. Consequently, a supply of poor quality course aggregate (poor particle shape as well as poor gradation) in construction material become a social problem. In this study, an effect of aggregate particle shape on property of concrete was evaluated. The flat and elongation ratio of crushed aggregate was controled to 8, 15, 25, 35, and $47\%$ in order to evaluate fresh concrete behavior as well as physical properties in hardened concrete. Test result shows a poor aggregate particle shape cause a significant increase in entrapped air in fresh concrete, while no significant effect on hardened concrete property, such as strength as well as stiffness. This increase in entrapped air, however, believed to cause a significant decrease in concrete durability.

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Comparison of EG/AD/S and EG/AD model ice properties

  • Kim, Jung-Hyun;Choi, Kyung-Sik
    • International Journal of Ocean System Engineering
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    • v.1 no.1
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    • pp.32-36
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    • 2011
  • EG/AD/S type model ice was originally selected as the primary model ice material for the MOERI ice tank in Korea. The existence of a sugar component in the EG/AD/S mixture may cause a serious maintenance problem. In order to understand the influence of sugar in the original model ice, a series of tests with EG/AD/S and EG/AD model ices were performed, and their material properties compared. Because the target strength of model ice in the full-scale MOERI ice tank is expensive and difficult to control, tests were performed under cold room conditions using a miniature ice tank. This paper describes the material properties of EG/AD/S and EG/AD model ices, such as flexural strength, compressive strength and elastic modulus. In order to obtain the desired strength and stiffness levels for the model ice, a warm-up process was introduced.

The Analysis of Eigenvalue Problems of Timoshenko Beams Using Curvature-based Beam Elements (곡률 보요소에 의한 Timoshenko 보의 고유치 문제 해석)

  • 양승용;이재관;신효철
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.11
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    • pp.2694-2703
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    • 1993
  • In the vibration analysis of Timoshenko beams by the finite element method, it is necessary to use a large number of elements or higher-order elements in modeling thin beams. This is because the overestimated stiffness matrix due to the shear locking phenomenon when lower-order displacement-based elements are used yields poor eigensolutions. As a result, the total number of degrees of freedom becomes critical in view of computational efficiency. In this paper, the curvature-based formulation is applied to the vibration problem. It is shown that the curvaturebased beam elements are free of shear locking and very efficient in the vibration analysis.

Analysis of elastic foundation plates with internal and perimetric stiffening beams on elastic foundations by using Finite Differences Method

  • Orbanich, C.J.;Ortega, N.F.
    • Structural Engineering and Mechanics
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    • v.45 no.2
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    • pp.169-182
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    • 2013
  • The mechanical behavior of rectangular foundation plates with perimetric beams and internal stiffening beams of the plate is herein analyzed, taking the foundation design into account. A series of dimensionless parameters related to the geometry of the studied elements were defined. In order to generalize the problem statement, an initial settlements was considered. A numeric procedure was developed for the resolution by means of the Finite Differences Method that takes into account the stiffness of the plate, the perimetric and internal plate beams and the soil reaction module. Iterative algorithms were employed which, for each of the analyzed cases, made it possible to find displacements and reaction percentages taken by the plate and those that discharge directly into the perimetric beams, practically without affecting the plate. To enhance its mechanical behavior the internal stiffening beams were prestressed and the results obtained with and without prestressing were compared. This analysis was made considering the load conditions and the soil reaction module constant.

Development of Application Technique for a Car Body with Aluminium Sandwich Panels (샌드위치 판재의 차량적용 기술개발)

  • Lee, Myeong-Ho;Yu, Yong-Mun;Yun, Ui-Park;Lee, Gyeong-Nam;Lee, Jung-Yun;Geum, Yeong-Tak
    • Transactions of Materials Processing
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    • v.7 no.6
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    • pp.603-609
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    • 1998
  • An aluminium sandwich sheet is the material fabricated by adhering two aluminum panels to one plastic core. When it has the same bending stiffness as an steel panel it is 65% lighter than steel panel and 30% lighter than aluminum panel. Therefore it is notified exclusively as good substitutive materials for steel body to improve fuel efficiency. An aluminium sandwich sheet, however, has a problem of the lower formability than steel in automotive application. In this paper we intend to develop application technologies of an aluminum sandwich sheet for auto body panels from selecting composed materials of aluminium sandwich sheets to fabricating prototype. We selected aluminium sandwich panels fabricated by Hoogovens company. Through formability tests we have designed the hood part on auto body panels and fabricated a mould and a prototype.

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Development of Application Technique for a Car Body with Aluminium Sandwich Panels (샌드위치 판재의 차량적용 기술개발)

  • ;dbdydans
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1998.06a
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    • pp.131-139
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    • 1998
  • An aluminium sandwich sheet is the material fabricated by adhering two aluminum panels to one plastic core. If it has the same bending stiffness as an steel panel, it is 65% lighter than steel panel and 30% lighter than aluminum panel. Therefore it is marked exclusively as god substitutive materials of steel body for improving fuel efficiency. But an aluminium sandwich sheet has problem of the lower formability than steel for automotive application. In this paper we intend to develop application technologies of an aluminum sandwich sheet for auto body panels from the selecting composed materials of aluminium sandwich sheets to fabricating prototype. We selected aluminium sandwich panels fabricated by Hoogovens company. Through formability tests we have finished the design and fabricated a mould and a prototype.

Dynamic Analysis of Rotary Compressor with Rotor Misaligment (축어긋남을 갖는 로터리 컴프레서의 동적해석)

  • 정의봉;김태학
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1997.10a
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    • pp.82-87
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    • 1997
  • Large dynamic loads act on the rotor in rotary compressors. There are unbalance forces due to eccentric parts and gas forces induced by the pressure difference between compression and suction gases. Rotor-journal bearing system is nonlinear since the stiffness and damping coefficients of the lubricating oil film are not constant in the bearings. The system is considered as a coupled problem of flexible rotor and the journal bearings. Bearing reaction force is calculated from pressure of oil film using Reynolds equations in journal bearings. Pressure distribution in journal bearing is analyzed by finite difference method. The dynamic response of rotor and bearing characteristic are discussed when rotary compressor has a relative misalignment.

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Rotordynamics Design Sensitivity Analysis of an APU Gas Turbine having a Spline Shaft Connection (스플라인-축 연결을 갖는 보조동력장치 가스터빈의 로터다이나믹 설계민감도 해석)

  • Lee, An-Sung;Ha, Jin-Woong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.11a
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    • pp.593-598
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    • 2000
  • In this paper the critical speed analysis and design sensitivity investigation are carried out with an APU(auxiliary power unit) gas turbine having a spline shaft connection. The DDM(direct differential method) is directly applied to formulate the critical speed design sensitivity problem of a general nonsymmetric-matrix rotor-bearing system. The design sensitivity analysis have shown that the critical speed change rate to the support modeling of the spline shaft connection point is extremely negligible, and thereby its design uncertainty is lifted. It has also been confirmed that the critical speeds up to the 4th are not sensitive to the design stiffness coefficients of 4-main bearings or supports, including two air foil bearings. Further, the critical speed change rate to the shaft-element length have shown quantitatively that the spline shaft has some limited influence on the 4th critical speed.

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Dynamic Reanalysis of Base-Isolated Systems Using a Perturbation Technique (섭동법에 의한 면진구조계의 동적 재해석)

  • Kim, Hee-duck
    • Journal of the Korean Society of Industry Convergence
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    • v.4 no.2
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    • pp.167-175
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    • 2001
  • In this study, a general perturbation method is presented to reanalysis dynamic response of base-isolated systems. The perturbation is expanded to general order and which provide the formulation of perturbed solutions. in which eigensolutions of non-modified system are treated as unperturbed solutions. The accuracy of present method is tested using a 2-DOF system with isolator, where the stiffness and damping coefficients of isolator are changed, respectively, The reanalyzed eigensolutions and response using perturbed solutions are successfully approached to exact ones after just first perturbation. Supposing the practical criterion as ${\pm}5%$ error, the modification range of -50%~30% from original system can be allowed for the first order perturbation. Using higher order solutions, the applicable range will be wide.

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