The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform

Roger Ohayon - One of the best experts on this subject based on the ideXlab platform.

  • Vibration of axisymmetric composite piezoelectric shells coupled with Internal Fluid
    International Journal for Numerical Methods in Engineering, 2017
    Co-Authors: Walid Larbi, Jean-François Deü, Roger Ohayon
    Abstract:

    This paper presents the theoretical and finite element formulations of piezoelectric composite shells of revolution filled with compressible Fluid. The originality of this work lies (i) in the development of a variational formulation for the fully coupled Fluid/piezoelectric structure system, and (ii) in the finite element implementation of an inexpensive and accurate axisymmetric adaptive laminated conical shell element. Various modal results are presented in order to validate and illustrate the efficiency of the proposed Fluid–structure finite element formulation.

  • Partitioned vibration analysis of Internal Fluid‐structure interaction problems
    International Journal for Numerical Methods in Engineering, 2012
    Co-Authors: José A. González, K. C. Park, Carlos A. Felippa, Roger Ohayon
    Abstract:

    SUMMARY A partitioned, continuum-based, Internal Fluid–structure interaction (FSI) formulation is developed for modeling combined sloshing, acoustic waves, and the presence of an initial pressurized state. The present formulation and its computer implementation use the method of localized Lagrange multipliers to treat both matching and non-matching interfaces. It is shown that, with the context of continuum Lagrangian kinematics, the Fluid sloshing and acoustic stiffness terms originate from an initial pressure term akin to that responsible for geometric stiffness effects in solid mechanics. The present formulation is applicable to both linearized vibration analysis and nonlinear FSI transient analysis provided that a convected kinematics is adopted for updating the mesh geometry in a finite element discretization. Numerical examples illustrate the capability of the present procedure for solving coupled vibration and nonlinear sloshing problems. Copyright © 2012 John Wiley & Sons, Ltd.

  • Vibration of axisymmetric composite piezoelectric shells coupled with Internal Fluid
    International Journal for Numerical Methods in Engineering, 2007
    Co-Authors: Walid Larbi, Roger Ohayon
    Abstract:

    This paper presents the theoretical and finite element formulations of piezoelectric composite shells of revolution filled with compressible Fluid. The originality of this work lies (i) in the development of a variational formulation for the fully coupled Fluid/piezoelectric structure system, and (ii) in the finite element implementation of an inexpensive and accurate axisymmetric adaptive laminated conical shell element. Various modal results are presented in order to validate and illustrate the efficiency of the proposed Fluid–structure finite element formulation. Copyright © 2007 John Wiley & Sons, Ltd.

  • partitioned formulation of Internal Fluid structure interaction problems by localized lagrange multipliers
    Computer Methods in Applied Mechanics and Engineering, 2001
    Co-Authors: K. C. Park, Carlos A. Felippa, Roger Ohayon
    Abstract:

    Abstract A partitioned formulation of compressible Internal Fluid–structure interaction problems is presented by employing a displacement model for both the Fluid and structure. Partitioning is effected by a localized version of the method of Lagrange multipliers, which assigns two independent sets of Lagrange multipliers to the structural and Fluid interfaces. Two major features of the present formulation include: an interface compliance normalization that helps capture the predominant physics of interaction phenomena when the interfaces are characterized by two radically different rigidities, and a novel transformation of the displacement model into a Fluid-pressure model that is suitable for both transient and vibration analyses. The present formulation first solves for the interface Lagrange multipliers, which are subsequently used to solve for the structural displacements and the Fluid displacement or pressure by employing two independent analysis modules.

  • Partitioned formulation of Internal Fluid–structure interaction problems by localized Lagrange multipliers
    Computer Methods in Applied Mechanics and Engineering, 2001
    Co-Authors: K. C. Park, Carlos A. Felippa, Roger Ohayon
    Abstract:

    Abstract A partitioned formulation of compressible Internal Fluid–structure interaction problems is presented by employing a displacement model for both the Fluid and structure. Partitioning is effected by a localized version of the method of Lagrange multipliers, which assigns two independent sets of Lagrange multipliers to the structural and Fluid interfaces. Two major features of the present formulation include: an interface compliance normalization that helps capture the predominant physics of interaction phenomena when the interfaces are characterized by two radically different rigidities, and a novel transformation of the displacement model into a Fluid-pressure model that is suitable for both transient and vibration analyses. The present formulation first solves for the interface Lagrange multipliers, which are subsequently used to solve for the structural displacements and the Fluid displacement or pressure by employing two independent analysis modules.

O. A. Ershova - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of the energy transmission in spatial piping systems with heavy Internal Fluid loading
    Journal of Sound and Vibration, 2008
    Co-Authors: Sergey Sorokin, N. Olhoff, O. A. Ershova
    Abstract:

    The energy transmission in spatial elastic water-filled pipes is considered. A solution of the wave propagation problem in the framework of the general theory of elastic cylindrical shells with Internal Fluid loading is used as a reference. It is shown that energy transmission phenomena may be adequately described by means of the reduced theory in the frequency range of practical interest. The boundary integral equations method is specialised for this reduced theory and two generic problems of the energy transmission in piping systems are solved. The first one is concerned with analysis of the distribution of the transmitted energy between two branches in a pipeline with a single joint and between alternative transmission paths in each branch. Besides the frequency and the type of excitation, the influence of an angle between connected pipes is studied. The second problem is related to analysis of the energy transmission in a pipe with multiple regularly spaced junctions and attention is focused at formation of frequency band gaps due to periodicity of location of branches.

  • The energy generation and transmission in compound elastic cylindrical shells with heavy Internal Fluid loading—from parametric studies to optimization
    Structural and Multidisciplinary Optimization, 2006
    Co-Authors: S. V. Sorokin, N. Olhoff, O. A. Ershova
    Abstract:

    The methodology of boundary integral equations is applied for analysis and optimization of the power flows in elastic compound cylindrical shells with heavy Internal Fluid loading. Two generic model problems are solved and the roles of various physical parameters involved in the problem formulation are assessed. It is shown that the efficiency of an optimization procedure heavily relies on a careful parametric study of wave propagation and correct physical interpretation of its results.

K. C. Park - One of the best experts on this subject based on the ideXlab platform.

  • Partitioned vibration analysis of Internal Fluid‐structure interaction problems
    International Journal for Numerical Methods in Engineering, 2012
    Co-Authors: José A. González, K. C. Park, Carlos A. Felippa, Roger Ohayon
    Abstract:

    SUMMARY A partitioned, continuum-based, Internal Fluid–structure interaction (FSI) formulation is developed for modeling combined sloshing, acoustic waves, and the presence of an initial pressurized state. The present formulation and its computer implementation use the method of localized Lagrange multipliers to treat both matching and non-matching interfaces. It is shown that, with the context of continuum Lagrangian kinematics, the Fluid sloshing and acoustic stiffness terms originate from an initial pressure term akin to that responsible for geometric stiffness effects in solid mechanics. The present formulation is applicable to both linearized vibration analysis and nonlinear FSI transient analysis provided that a convected kinematics is adopted for updating the mesh geometry in a finite element discretization. Numerical examples illustrate the capability of the present procedure for solving coupled vibration and nonlinear sloshing problems. Copyright © 2012 John Wiley & Sons, Ltd.

  • partitioned formulation of Internal Fluid structure interaction problems by localized lagrange multipliers
    Computer Methods in Applied Mechanics and Engineering, 2001
    Co-Authors: K. C. Park, Carlos A. Felippa, Roger Ohayon
    Abstract:

    Abstract A partitioned formulation of compressible Internal Fluid–structure interaction problems is presented by employing a displacement model for both the Fluid and structure. Partitioning is effected by a localized version of the method of Lagrange multipliers, which assigns two independent sets of Lagrange multipliers to the structural and Fluid interfaces. Two major features of the present formulation include: an interface compliance normalization that helps capture the predominant physics of interaction phenomena when the interfaces are characterized by two radically different rigidities, and a novel transformation of the displacement model into a Fluid-pressure model that is suitable for both transient and vibration analyses. The present formulation first solves for the interface Lagrange multipliers, which are subsequently used to solve for the structural displacements and the Fluid displacement or pressure by employing two independent analysis modules.

  • Partitioned formulation of Internal Fluid–structure interaction problems by localized Lagrange multipliers
    Computer Methods in Applied Mechanics and Engineering, 2001
    Co-Authors: K. C. Park, Carlos A. Felippa, Roger Ohayon
    Abstract:

    Abstract A partitioned formulation of compressible Internal Fluid–structure interaction problems is presented by employing a displacement model for both the Fluid and structure. Partitioning is effected by a localized version of the method of Lagrange multipliers, which assigns two independent sets of Lagrange multipliers to the structural and Fluid interfaces. Two major features of the present formulation include: an interface compliance normalization that helps capture the predominant physics of interaction phenomena when the interfaces are characterized by two radically different rigidities, and a novel transformation of the displacement model into a Fluid-pressure model that is suitable for both transient and vibration analyses. The present formulation first solves for the interface Lagrange multipliers, which are subsequently used to solve for the structural displacements and the Fluid displacement or pressure by employing two independent analysis modules.

Majid Elyasi - One of the best experts on this subject based on the ideXlab platform.

  • Improvement of the rotary draw bending process in rectangular tubes by using Internal Fluid pressure
    The International Journal of Advanced Manufacturing Technology, 2018
    Co-Authors: Ali Zardoshtian, Hossein Sabet, Majid Elyasi
    Abstract:

    The rotary draw bending has been conducted in square sections usually through techniques such as using the mandrel and wiper, which are mainly associated with inevitable defects such as wrinkling, thinning, folding, tearing, sagging, and cross-sectional distortion in the bending area. In this research, the improvement in the bending process of Al6063 rectangular tubes has been evaluated experimentally and numerically by applying the Internal Fluid pressure. Since the rectangular tube sealing is difficult in practice, designing a sealing system suitable for both ends of the tube has been tried. This was done to investigate the effect of different Fluid pressures and without Fluid pressure at the bending ratio of 3. Also, the amount of increasing in the thickness and wrinkling of the intrados area and decreasing in the thickness and sagging of the bent tube extrados is examined. The results showed that wrinkling, sagging, and cross-sectional distortion in the bending area has been reduced significantly. As a consequence, at a certain pressure, those kinds of defects almost disappeared due to the strain distribution caused by stress arising on the Internal surface of the tube.

  • Improvement of the rotary draw bending process in rectangular tubes by using Internal Fluid pressure
    International Journal of Advanced Manufacturing Technology, 2018
    Co-Authors: Ali Zardoshtian, Hossein Sabet, Majid Elyasi
    Abstract:

    © 2017, Springer-Verlag London Ltd. The rotary draw bending has been conducted in square sections usually through techniques such as using the mandrel and wiper, which are mainly associated with inevitable defects such as wrinkling, thinning, folding, tearing, sagging, and cross-sectional distortion in the bending area. In this research, the improvement in the bending process of Al6063 rectangular tubes has been evaluated experimentally and numerically by applying the Internal Fluid pressure. Since the rectangular tube sealing is difficult in practice, designing a sealing system suitable for both ends of the tube has been tried. This was done to investigate the effect of different Fluid pressures and without Fluid pressure at the bending ratio of 3. Also, the amount of increasing in the thickness and wrinkling of the intrados area and decreasing in the thickness and sagging of the bent tube extrados is examined. The results showed that wrinkling, sagging, and cross-sectional distortion in the bending area has been reduced significantly. As a consequence, at a certain pressure, those kinds of defects almost disappeared due to the strain distribution caused by stress arising on the Internal surface of the tube.

N. Olhoff - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of the energy transmission in spatial piping systems with heavy Internal Fluid loading
    Journal of Sound and Vibration, 2008
    Co-Authors: Sergey Sorokin, N. Olhoff, O. A. Ershova
    Abstract:

    The energy transmission in spatial elastic water-filled pipes is considered. A solution of the wave propagation problem in the framework of the general theory of elastic cylindrical shells with Internal Fluid loading is used as a reference. It is shown that energy transmission phenomena may be adequately described by means of the reduced theory in the frequency range of practical interest. The boundary integral equations method is specialised for this reduced theory and two generic problems of the energy transmission in piping systems are solved. The first one is concerned with analysis of the distribution of the transmitted energy between two branches in a pipeline with a single joint and between alternative transmission paths in each branch. Besides the frequency and the type of excitation, the influence of an angle between connected pipes is studied. The second problem is related to analysis of the energy transmission in a pipe with multiple regularly spaced junctions and attention is focused at formation of frequency band gaps due to periodicity of location of branches.

  • The energy generation and transmission in compound elastic cylindrical shells with heavy Internal Fluid loading—from parametric studies to optimization
    Structural and Multidisciplinary Optimization, 2006
    Co-Authors: S. V. Sorokin, N. Olhoff, O. A. Ershova
    Abstract:

    The methodology of boundary integral equations is applied for analysis and optimization of the power flows in elastic compound cylindrical shells with heavy Internal Fluid loading. Two generic model problems are solved and the roles of various physical parameters involved in the problem formulation are assessed. It is shown that the efficiency of an optimization procedure heavily relies on a careful parametric study of wave propagation and correct physical interpretation of its results.

  • green s matrix and the boundary integral equation method for the analysis of vibration and energy flow in cylindrical shells with and without Internal Fluid loading
    Journal of Sound and Vibration, 2004
    Co-Authors: Sergey Sorokin, J B Nielsen, N. Olhoff
    Abstract:

    Abstract This paper presents several aspects of the dynamics of a cylindrical shell with and without heavy Internal Fluid loading, which have not been studied before in detail. Firstly, a consistent formulation of boundary integral equations for a shell of finite length is derived based on the energy conservation principle and the reciprocity theorem. This derivation naturally leads to identification of principal components of the energy flux through an arbitrary cross-section of a shell and to formulation of Green's matrix for an infinitely long shell at each individual circumferential wave number. Secondly, an inspection into the energy re-distribution between several transmission paths in a near field (in a boundary layer at the vicinity of a loaded cross-section) is performed, which sheds light on the role of evanescent waves in motions of a driven shell. Thirdly, the influence of excitation conditions on steady fluctuations of the overall energy flow between transmission paths in a far field is explored for the case, when several propagating waves exist in a shell both with and without Internal Fluid loading. Besides, a systematic verification of the solution offered by the boundary equations method is given through comparison of eigenfrequencies with those computed in finite element modelling for various boundary conditions. Analysis of dispersion curves and input mobilities is also presented.