• Title/Summary/Keyword: 박막이론(membrane theory)

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구형 압력용기의 초소성 성형 공정에서 두께변화 예측에 관한 이론해석

  • Yoon, Jong-Hoon;Lee, Ho-Sung;Jang, Young-Soon;Yi, Yeong-Moo
    • Aerospace Engineering and Technology
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    • v.2 no.2
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    • pp.133-141
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    • 2003
  • When superplastic forming process is employed in manufacturing spherical pressure vessel, the thickness and spherical profile are not constant and varies during the forming process. In the current study, theoretical analysis for the prediction of thickness change was carried out under the consideration of membrane theory which has been employed in Kuglov et. al.'s study. Then the thickness of initial blank to obtain the required thickness at the final forming step, the time vs. pressure profile which yields uniform deformation in blank, and the thickness distribution according to the position at each forming step have been determined. The employed model and the developed analytical code were verified throughout comparing the theoretical predictions at each forming stage with the experimental results shown in literature.

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Membrane-duct: its theory and feasibility (박막형 소음기: 이론과 적용 가능성)

  • Kim, Yang-Hann;Chun, Young-Doo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.1648-1653
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    • 2000
  • Theoretical analysis of noise reduction by a membrane-duct system is presented. When acoustic waves propagate in the membrane-duct, the part of membrane is also excited and its motion is coupled with interior medium. For an infinite plane membrane-duct system, a simple coupled governing equation is derived and solved. One of the characteristics of dispersion relation is that evanescent waves occur below critical frequency. Attaching damping materials to the membrane may improve the absorption efficiency of acoustic energy. The results show that the membrane-duct system can be applied to diminish and absorb low frequency noise in duct instead of passive muffler, such as simple expansion chamber or absorption material.

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Wave Deformation by Submerged Flexible Circular Disk (몰수된 원형 유연막에 의한 파랑변형)

  • 조일형;김무현
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.12 no.3
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    • pp.116-129
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    • 2000
  • The interaction of incident monochromatic waves with a tensioned, flexible, circular membrane submerged horizontally below free surface is investigated in the frame of three-dimensional linear hydro-elastic theory. The velocity potential is split into two parts i.e. the diffraction potential representing the scattering of incident waves by a rigid circular disk and the radiation potential describing motion induced waves by elastic responses of flexible membrane. The fluid domain is divided into three regions, and the diffraction and radiation potentials in each region are expressed by the Fourier Bessel series. The displacement of circular membrane is expanded with a set of natural functions, which satisfy the membrane equation of motion and boundary conditions. The unknown coefficients in each region are determined by applying the continuity of pressure and normal velocity at the matching boundaries. The results show that various types of wave focusing are possible by controlling the size, submergence depth, and tension of membrane.

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Incorporation of Sheet Forming Effects in Crash Simulations Using Ideal Forming Theory and Hybrid Membrane/shell Method (이상공정이론 및 하이브리드 박막/쉘 방법을 이용한 박판성형품의 충돌거동 해석)

  • 류한선;정관수;윤정환;한정석;윤재륜;강태진
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2003.10a
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    • pp.148-151
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    • 2003
  • In order to achieve reliable but cost-effective crash simulations of stamped parts, sheet forming process effects were incorporated in simulations using the ideal forming theory mixed with the 3D hybrid membrane/shell method, while the subsequent crash simulations were carried out using a dynamic explicit finite element code. Example solutions performed for forming and crash simulations of I- and S-shaped rails verified that the proposed approach is cost-effective without sacrificing accuracy. The method required a significantly small amount of additional computation time, less than 3% for the specific examples, to incorporate sheet forming effects to crash simulations. As for the constitutive equation, the combined isotropic-kinematic hardening law and the non-quadratic anisotropic yield stress potential as well as its conjugate strain-rate potential were used to describe the anisotropy of AA6114-T4 aluminum alloy sheets.

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Analysis of Deep Drawing of Planar Anisotropic Materials Using the Rigid- Plastic Finite Element Method (강소성 유한요소법을 이용한 평면 이방성 재료의 디프 드로잉 해석)

  • 김형종;김동원
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.2
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    • pp.248-258
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    • 1992
  • Three-dimensional rigid-plastic finite element formulation based on the membrane theory was described and a computer program for large deformation analysis was developed. In the formulation, normal and planar anisotropy of sheet material and rotation of the principal axes of anisotropy was taken into consideration. Sheet metal was assumed to be rigid-plastic material obeying Hill's quadratic yield criterion and its associated flow rule. Deep drawing process, as a preliminary test, for normal anisotropic material was analyzed in order to examine the validity of developed finite element program. The results were consistent with the existing finite element solutions or experimental data. The present study was mainly concerned with the influence of planar anisotropy on deformation behaviour. Finite element analysis and experiment were carried out for the whole process of deep drawing of planar anisotropic material. The computational and experimental results on the shape of ear, strain distribution and punch load were in good agreement.

Design considerations and field applications on inflatable structure system to protect rapidly flooding damages in tunnel (해저터널 급속차폐를 위한 팽창구조체의 설계 및 현장적용에 대한 연구)

  • Kim, Hyeob;Kang, Si-On;Yoo, Kwang-San;Kim, Sang-Hwan
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.19 no.2
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    • pp.161-177
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    • 2017
  • This paper presents the design considerations and field applications on inflatable structure system to protect rapidly flooding damages in large section tunnel. This inflatable structure system is very valuably used to protect passively and rapidly the possibilities of tunnel damages by flooding threats and unusual leakage to be occurred during and after underground infrastructure. In particular, this system should be necessary in subsea tunnel. The predominant factors in the design of inflatable structure system are the leakage and friction characteristics between the inflater and tunnel liner. The analytical and experimental studies are performed to develop the design considerations and to examine the design parameters of the inflatable structure system. The analytical solutions are developed using membrane theory to suggest the design considerations. The relative friction tests of several fabric materials are also carried out to determine the friction characteristics according to the different friction conditions between inflater and tunnel surface. The test results show that the friction coefficients in wet surface condition are about 20% lower than the values in dry surface condition. In addition, virtual design of tunnel protection system for two virtual subsea tunnel sites which is under reviewing in Korea, is carried out based on this research. It is expected that the results of this research will be very useful to understand the inflater structure design and development the technology of tunnel protection structures in the future.