Imperfect Shell

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Pedro M. Reis - One of the best experts on this subject based on the ideXlab platform.

  • Buckling of pressurized spherical Shells containing a through-thickness defect
    Journal of the Mechanics and Physics of Solids, 2020
    Co-Authors: Dong Yan, Matteo Pezzulla, Pedro M. Reis
    Abstract:

    Abstract We present a study on the pressure buckling of thin, elastic spherical Shells containing a thickness defect. Methodologically, we combine precision model experiments, finite element simulations, and a reduced axisymmetric Shell model. We observe qualitatively different buckling behavior by varying the geometry of the defect: either one buckling event or two events comprising local buckling at the defect and global buckling of the entire Shell. We systematically analyze the loading path for the Imperfect Shell under prescribed pressure or volume change and identify three buckling regimes. We then explore a wide parameter space to study the dependence of the buckling regimes on the defect geometry, thus obtaining a phase diagram with quantitative relationships between critical buckling pressures and defect geometry. We find that the global buckling becomes insensitive to the defect beyond a critical value of its amplitude, and we demonstrate that the buckling regimes are governed by the three geometric parameters of the defect, namely its width, amplitude and the width of the transition region across the edge of the defect.

Vissarion Papadopoulos - One of the best experts on this subject based on the ideXlab platform.

  • Vulnerability-based robust design optimization of Imperfect Shell structures
    Structural Safety, 2009
    Co-Authors: Vissarion Papadopoulos, Nikos D. Lagaros
    Abstract:

    Abstract A stochastic vulnerability-based robust design procedure of isotropic Shell structures possessing uncertain initial geometric as well as material and thickness properties that are modeled as random fields is assessed against conventional and reliability-based robust design procedures. The main idea of the vulnerability-based design philosophy is to achieve robust optimum designs while allowing designers to determine explicitly accepted probabilities that various performance objectives will not be exceeded, by introducing additional probabilistic (vulnerability) constraints. For this purpose, a stochastic finite element methodology is incorporated into the framework of an efficient two-objective robust design optimization formulation. This combined approach is then implemented in order to obtain optimum designs of an “ImperfectShell structure involving random geometric deviations from its perfect geometry as well as a spatial variability of its modulus of elasticity and thickness. Two-objective functions, the material volume of the structure and the coefficient of variation of the buckling load of the Shell, are used for the description of the optimization problem, subject to deterministic, reliability and vulnerability constraints.

  • A computationally efficient method for the buckling analysis of Shells with stochastic Imperfections
    Computational Mechanics, 2008
    Co-Authors: Vissarion Papadopoulos, Dimos C. Charmpis, Manolis Papadrakakis
    Abstract:

    A computationally efficient method is presented for the buckling analysis of Shells with random Imperfections, based on a linearized buckling approximation of the limit load of the Shell. A Stochastic Finite Element Method approach is used for the analysis of the “ImperfectShell structure involving random geometric deviations from its perfect geometry, as well as spatial variability of the modulus of elasticity and thickness of the Shell, modeled as random fields. A corresponding eigenproblem for the prediction of the buckling load is solved at each MCS using a Rayleigh quotient-based formulation of the Preconditioned Conjugate Gradient method. It is shown that the use of the proposed method reduces drastically the computational effort involved in each MCS, making the implementation of such stochastic analyses in real-world structures affordable.

  • Optimum design of Shell structures with random geometric, material and thickness Imperfections
    International Journal of Solids and Structures, 2006
    Co-Authors: Nikos D. Lagaros, Vissarion Papadopoulos
    Abstract:

    AbstractThe optimum design of isotropic Shell structures with random initial geometric, material and thickness Imperfections is investigated in this paper and a robust and efficient methodology is presented for treating such problems. For this purpose, the concept of an initial “Imperfect” structure is introduced involving not only geometric deviations of the Shell structure from its perfect geometry but also a spatial variability of the modulus of elasticity as well as of the thickness of the Shell. An efficient reliability-based design optimization (RBDO) formulation is proposed. The objective function is considered to be the weight of the structure while both deterministic and probabilistic constraints are taken into account. The overall probability of failure is taken as the global probabilistic constraint for the optimization procedure. Numerical results are presented for a cylindrical panel, demonstrating the efficiency as well as the applicability of the proposed methodology in obtaining rational optimum designs of Imperfect Shell-type structures

Dong Yan - One of the best experts on this subject based on the ideXlab platform.

  • Buckling of pressurized spherical Shells containing a through-thickness defect
    Journal of the Mechanics and Physics of Solids, 2020
    Co-Authors: Dong Yan, Matteo Pezzulla, Pedro M. Reis
    Abstract:

    Abstract We present a study on the pressure buckling of thin, elastic spherical Shells containing a thickness defect. Methodologically, we combine precision model experiments, finite element simulations, and a reduced axisymmetric Shell model. We observe qualitatively different buckling behavior by varying the geometry of the defect: either one buckling event or two events comprising local buckling at the defect and global buckling of the entire Shell. We systematically analyze the loading path for the Imperfect Shell under prescribed pressure or volume change and identify three buckling regimes. We then explore a wide parameter space to study the dependence of the buckling regimes on the defect geometry, thus obtaining a phase diagram with quantitative relationships between critical buckling pressures and defect geometry. We find that the global buckling becomes insensitive to the defect beyond a critical value of its amplitude, and we demonstrate that the buckling regimes are governed by the three geometric parameters of the defect, namely its width, amplitude and the width of the transition region across the edge of the defect.

Nikos D. Lagaros - One of the best experts on this subject based on the ideXlab platform.

  • Vulnerability-based robust design optimization of Imperfect Shell structures
    Structural Safety, 2009
    Co-Authors: Vissarion Papadopoulos, Nikos D. Lagaros
    Abstract:

    Abstract A stochastic vulnerability-based robust design procedure of isotropic Shell structures possessing uncertain initial geometric as well as material and thickness properties that are modeled as random fields is assessed against conventional and reliability-based robust design procedures. The main idea of the vulnerability-based design philosophy is to achieve robust optimum designs while allowing designers to determine explicitly accepted probabilities that various performance objectives will not be exceeded, by introducing additional probabilistic (vulnerability) constraints. For this purpose, a stochastic finite element methodology is incorporated into the framework of an efficient two-objective robust design optimization formulation. This combined approach is then implemented in order to obtain optimum designs of an “ImperfectShell structure involving random geometric deviations from its perfect geometry as well as a spatial variability of its modulus of elasticity and thickness. Two-objective functions, the material volume of the structure and the coefficient of variation of the buckling load of the Shell, are used for the description of the optimization problem, subject to deterministic, reliability and vulnerability constraints.

  • Optimum design of Shell structures with random geometric, material and thickness Imperfections
    International Journal of Solids and Structures, 2006
    Co-Authors: Nikos D. Lagaros, Vissarion Papadopoulos
    Abstract:

    AbstractThe optimum design of isotropic Shell structures with random initial geometric, material and thickness Imperfections is investigated in this paper and a robust and efficient methodology is presented for treating such problems. For this purpose, the concept of an initial “Imperfect” structure is introduced involving not only geometric deviations of the Shell structure from its perfect geometry but also a spatial variability of the modulus of elasticity as well as of the thickness of the Shell. An efficient reliability-based design optimization (RBDO) formulation is proposed. The objective function is considered to be the weight of the structure while both deterministic and probabilistic constraints are taken into account. The overall probability of failure is taken as the global probabilistic constraint for the optimization procedure. Numerical results are presented for a cylindrical panel, demonstrating the efficiency as well as the applicability of the proposed methodology in obtaining rational optimum designs of Imperfect Shell-type structures

Matteo Pezzulla - One of the best experts on this subject based on the ideXlab platform.

  • Buckling of pressurized spherical Shells containing a through-thickness defect
    Journal of the Mechanics and Physics of Solids, 2020
    Co-Authors: Dong Yan, Matteo Pezzulla, Pedro M. Reis
    Abstract:

    Abstract We present a study on the pressure buckling of thin, elastic spherical Shells containing a thickness defect. Methodologically, we combine precision model experiments, finite element simulations, and a reduced axisymmetric Shell model. We observe qualitatively different buckling behavior by varying the geometry of the defect: either one buckling event or two events comprising local buckling at the defect and global buckling of the entire Shell. We systematically analyze the loading path for the Imperfect Shell under prescribed pressure or volume change and identify three buckling regimes. We then explore a wide parameter space to study the dependence of the buckling regimes on the defect geometry, thus obtaining a phase diagram with quantitative relationships between critical buckling pressures and defect geometry. We find that the global buckling becomes insensitive to the defect beyond a critical value of its amplitude, and we demonstrate that the buckling regimes are governed by the three geometric parameters of the defect, namely its width, amplitude and the width of the transition region across the edge of the defect.