• Title, Summary, Keyword: Stiffened Cylindrical Shell

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Dynamic Behavior Analysis of Stiffened Cylindrical Shell Filled with Fluid (내부가 유체로 채워진 보강원통쉘의 동적거동 해석)

  • Youm, Ki-Un;Yoon, Kyung-Ho;Lee, Young-Shin;Kim, Jong-Kiun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.9
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    • pp.2875-2886
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    • 1996
  • This work present the experimental resutls for the free vibration of unstiffened, stiffened cylindrical shell filled with air, half water and full water. The natural frequencies and mode shapes of unstiffened, stiffened cylindrical shell are obtained experimentally also. The natural frequencies of stiffened cylindrical shell were generally highter than those of unstiffened cylindrical shell and natural requencies were decreased as cylindrical shell was filled with water. The effect of circumferential stiffener in the first mode was shown that natural frequency more increased 25% at air environment, 29% at half water environment and 37% at full water than those of unstiffened cylindrical shell, respectively. Also, the natural frequencies were decreased according to the added mass effect of fluid in the shell of unstiffened and stiffened cylindrical shell. The six mode shape results of all cases are simular and given. The natural frequencies are determined for a wide range of parameters : e.g. unstiffened shell, and filled with air, half and full water. The effects of varying the parameters on the free vibration frequencies and mode shapes are discussed.

Acoustic Radiation from a Submerged Stiffened Cylindrical Shell Excited by Resiliently Mounted Machinery (탄성지지된 기계류에 의해 가진되는 잠수된 보강 원통형 셸의 음향방사)

  • Bae, Soo Ryong;Lee, Shibok
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.25 no.1
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    • pp.33-39
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    • 2015
  • This paper investigates the underwater acoustic radiation from a periodically stiffened cylindrical shell excited resiliently mounted machinery. Underwater acoustic radiation is important to a submarine. Generally, submarine structure can be modeled as stiffened cylindrical shell immersed in water. Analytical model is derived for the far-field acoustic radiation from machinery installed inside cylindrical shell. The analytical model includes the effect of fluid loading and interactions between periodic ring stiffeners. Transmitted force from machine to a shell through isolator can be different by the impedance of shell. In this paper the effect of a shell impedance for acoustic radiation is investigated. Impedance of a shell should be considered if thickness of a shell is thin.

Stabilities of cable-stiffened cylindrical single-layer latticed shells

  • Li, Pengcheng;Wu, Minger
    • Steel and Composite Structures
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    • v.24 no.5
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    • pp.591-602
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    • 2017
  • A cable-stiffened cylindrical single-layer latticed shell that is reinforced by cable-stiffened system has superior stability behaviour compared with the ordinary cylindrical latticed shell. The layouts of cable-stiffened system are flexible in this structural system, and different layouts contribute different stiffness to the structure. However, the existed few research primarily focused on the simplest type of cable layouts, in which the grids of the latticed shell are diagonally stiffened by prestressed cables in-plane. This current work examines the stability behaviour of the cable-stiffened cylindrical latticed shells with two different types of cable layouts using nonlinear finite element analysis. A parametric study on the effect of cross-sectional of the cables, pretension in cables, joint stiffness, initial imperfections, load distributions and boundary conditions is presented. The findings are useful for the reference of the designer in using this type of structural system.

Active vibration control of nonlinear stiffened FG cylindrical shell under periodic loads

  • Ahmadi, Habib;Foroutan, Kamran
    • Smart Structures and Systems
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    • v.25 no.6
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    • pp.643-655
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    • 2020
  • Active control of nonlinear vibration of stiffened functionally graded (SFG) cylindrical shell is studied in this paper. The system is subjected to axial and transverse periodic loads in the presence of thermal uncertainty. The material composition is considered to be continuously graded in the thickness direction, also these properties depend on temperature. The relations of strain-displacement are derived based on the classical shell theory and the von Kármán equations. For modeling the stiffeners on the cylindrical shell surface, the smeared stiffener technique is used. The Galerkin method is used to discretize the partial differential equations of motion. Some comparisons are made to validate the SFG model. For suppression of the nonlinear vibration, the linear and nonlinear control strategies are applied. For control objectives, the piezoelectric actuator is attached to the external surface of the shell and the thin ring piezoelectric sensor is attached to the middle internal surface of shell. The effect of PID, feedback linearization and sliding mode control on the suppression of vibration for SFG cylindrical shell is presented.

Resisting Strength of Ring-Stiffened Cylindrical Steel Shell under Uniform External Pressure (균일외압을 받는 링보강 원형단면 강재 쉘의 강도특성)

  • Ahn, Joon Tae;Shin, Dong Ku
    • Journal of Korean Society of Steel Construction
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    • v.30 no.1
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    • pp.25-35
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    • 2018
  • Resisting strength of ring-stiffened cylindrical steel shell under uniform external pressure was evaluated by geometrically and materially nonlinear finite element method. The effects of shape and amplitude of geometric initial imperfection, radius to thickness ratio, and spacing of ring stiffeners on the resisting strength of ring-stiffened shell were analyzed. The resisting strength of ring-stiffened cylindrical shells made of SM490 obtained by FEA were compared with design strengths specified in Eurocode 3 and DNV-RP-C202. The shell buckling modes obtained from a linear elastic bifurcation FE analysis were introduced in the nonlinear FE analysis as initial geometric imperfections. The radius to thickness ratios of cylindrical shell in the range of 250 to 500 were considered.

A Study on the Design Optimization of Vibrarion Characteristics for Stiffened Cylindrical Shells (원주방향 보강재와 직교방향 보강재의 형상에 따른 원통형 쉘에 대한 진동의 최적화에 관한 연구)

  • Chang, Jin-Geon;Lee, Young-Shin;Kim, Young-Wan
    • Proceedings of the KSME Conference
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    • pp.631-636
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    • 2008
  • The cylindrical shells are mainly used in the nuclear energy structure, pressure vessel, boiler and so on. When designing of shell structures, predicting the structure change under variety boundary conditions are necessary for estimating the safety. Design variables for the design engineer include multiple material systems and boundary conditions, in addition to overall structural design parameters. Since the vibration of stiffened cylindrical shell is an important consideration for structures design, the reliable prediction method and design methodology should be required. In this study, the optimum design of stiffened cylindrical shell for maximum natural frequency was studied by analytic and numerical method.

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Analysis of Cantilever Cylindrical Shells with Edge-Stiffeners (캔틸레버 원통형 쉘의 단부보강 해석)

  • Park, Weon-Tae;Son, Byung-Jik
    • Journal of the Korean Society of Safety
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    • v.20 no.4
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    • pp.78-86
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    • 2005
  • In this study, cantilever cylindrical shells with edge-stiffeners are analyzed. A versatile 4-node flat shell element which is useful for the analysis of shell structures is used. An improved flat shell element is established by the combined use of the addition of non-conforming displacement modes and the substitute shear strain fields. Three models by load conditions are considered. Model A, B and C are loaded by point load at the free edge, line load and external pressure respectively. A various parameter examples are presented to obtain proper stiffened length and stiffened thickness of edge-stiffeners. It is shown that the thickness of shell can be reduced more than 50% for Model A, about $20{\sim}30%$ for Model B by appropriate edge-stiffeners.

Vibration Analysis of Ring Stiffened Cylindrical Shells with a Rectangular Cutout (사각개구부를 갖는 링보강 원통셸의 진동해석)

  • Kim, Yeong-Wan;Lee, Yeong-Sin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.23 no.11
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    • pp.2040-2049
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    • 1999
  • The Rayleigh-Ritz method is used to investigate the natural frequencies and mode shapes of the ring stiffened cylindrical shells with a rectangular cutout. The cutout is located on the center of the shell. The Love's thin shell theory combined with the discrete stiffener theory is adopted to formulate the analytical model of the shell. The effect of stiffener eccentricity, number, and position on vibration characteristics of the shell is examined. Also the effect of cutout size is examined. By comparison with previously published analytical and new FEM results, it is shown that natural frequencies and mode shapes can be determined with adequate accuracy.

Multi-objective optimal design of laminate composite shells and stiffened shells

  • Lakshmi, K.;Rama Mohan Rao, A.
    • Structural Engineering and Mechanics
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    • v.43 no.6
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    • pp.771-794
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    • 2012
  • This paper presents a multi-objective evolutionary algorithm for combinatorial optimisation and applied for design optimisation of fiber reinforced composite structures. The proposed algorithm closely follows the implementation of Pareto Archive Evolutionary strategy (PAES) proposed in the literature. The modifications suggested include a customized neighbourhood search algorithm in place of mutation operator to improve intensification mechanism and a cross over operator to improve diversification mechanism. Further, an external archive is maintained to collect the historical Pareto optimal solutions. The design constraints are handled in this paper by treating them as additional objectives. Numerical studies have been carried out by solving a hybrid fiber reinforced laminate composite cylindrical shell, stiffened composite cylindrical shell and pressure vessel with varied number of design objectives. The studies presented in this paper clearly indicate that well spread Pareto optimal solutions can be obtained employing the proposed algorithm.

Buckling of cylindrical shells under external pressure proposition of a new shape of self-stiffened shell

  • Araar, M.;Jullien, J.F.
    • Structural Engineering and Mechanics
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    • v.4 no.4
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    • pp.451-460
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    • 1996
  • We propose a new shape of cylindrical shell formed by multiples vaults which gives a self-stiffening against buckling. By an experimental and numerical study of cylindrical shells with a repeated defect, on the circumferential direction made only of outside oriented wave-defects, we show that multiple vault cylindrical shells can have a good behaviour in buckling. An optimal behaviour is obtained by optimization of the vaults number, with conduces to a special multiple vault cylindrical shell named "ASTER shell".