• Title/Summary/Keyword: axisymmetric shell element

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A Robustness of Hierarchic Element Formulated by Integrals of Legendre Polynomial (적분형 르장드르 함수에 의한 계층요소(階層要素)의 통용성(通用性))

  • Woo, Kwang Sung
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.12 no.1
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    • pp.43-50
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    • 1992
  • The purpose of this study is to ascertain the robustness of p-version model with hierarchic intergrals of Legendre shape functions in various applications including plane stress/strain, axisymmetric and shell problems. The most important symptoms of accuracy failure in modern finite elements are spurious mechanisms and a phenomenon known as locking which are exhibited for incompressible materials and irregular shapes which contain aspect ratios(R/t, a/b), tapered ratio(d/b), and skewness. The condition numbers and energy norms are used to estimate numerical errors, convergence characteristics and algorithmic efficiencies for verifying the aforementioned symptoms of accuracy failure. Numerical results from p-version models are compared with those from NASTRAN, SAP90, and Cheung's hybrid elements.

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Study on Deformation of Miniature Metal Bellows in Cryocooler Following Temperature Change of Internal Gas (내부 기체의 온도 변화에 따른 극저온 냉각기용 소형 금속 벨로우즈의 변형에 관한 연구)

  • Lee, Seung Ha;Lee, Tae Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.4
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    • pp.429-435
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    • 2015
  • A bellows is an important temperature control component in a Joule-Thomson micro-cryocooler. It is designed using a very thin shell, and the inside of the bellows is filled with nitrogen gas. The bellows is made of a nickel-cobalt alloy that maintains its strength and elastic properties in a wide range of temperatures from cryogenic to $300^{\circ}C$. The pressure of the gas and the volume within the bellows vary according to the temperature of the gas. As a result, the bellows contracts or expands in the axial direction like a spring. To explore this phenomenon, the deformation of the bellows and its internal volume must be calculated iteratively under a modified pressure until the state equation of the gas is satisfied at a given temperature. In this paper, the modified Benedict-Webb-Rubin state equation is adopted to describe the temperature-volume-pressure relations of the gas. Experiments were performed to validate the proposed method. The results of a numerical analysis and the experiments showed good agreement.

Analysis of the Mechanical Behavior of Bellows for Electromagnetic Control Valve (전자기 제어 밸브를 위한 벨로우즈의 기계적 거동에 관한 연구)

  • Son, In-Seo;Hwang, Seon;Shin, Dong-Kil
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.3
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    • pp.432-437
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    • 2016
  • The behavior of a bellows for an electromagnetic control valve was investigated. The bellows consists of an outer metal bellows, inner spring, and metal caps. The bellows needs to have sensitive and precise motion against external loads and pressure loads in order to control the position of the valve accurately. The spring constant of the inner spring and load-displacement curve of the bellows set were measured using a test machine. The inner spring showed a linear relation between load and displacement. The bellows set showed small stiffness at small displacement, and then the stiffness slightly increased upon subsequent displacement. Based on the measured data, finite element analysis was performed. Axisymmetric conditions were applied, and shell elements were used. The effective material properties of the outer bellows material were extracted. Additional analysis was performed, and the behavior of the bellows was analyzed using the finite element model.