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Serguei Iakovlev - One of the best experts on this subject based on the ideXlab platform.

  • submerged Circular Cylindrical Shell subjected to two consecutive shock waves resonance like phenomena
    Journal of Fluids and Structures, 2013
    Co-Authors: Serguei Iakovlev, C T Seaton, Jeanfrancois Sigrist
    Abstract:

    Abstract A submerged evacuated Circular Cylindrical Shell subjected to a sequence of two external shock waves generated at the same source is considered. A semi-analytical model combining the classical methods of mathematical physics with the finite-difference methodology is developed and employed to simulate the interaction. Both the hydrodynamic and structural aspects of the problem are considered, and it is demonstrated that varying the delay between the first and second wavefronts has a very significant effect on the stress–strain state of the structure. In particular, it is shown that for certain values of the delay, the constructive superposition of the elastic waves travelling around the Shell results in a ‘resonance-like’ increase of the structural stress in certain regions. The respective stress can be so high that it sometimes exceeds the overall maximum stress observed in the same structure but subjected to a single-front shock wave with the same parameters, in some cases by as much as 50%. A detailed parametric analysis of the observed phenomenon is carried out, and an easy-to-use diagram summarizing the finding is proposed to aim the pre-design analysis of engineering structures.

  • influence of a rigid coaxial core on the stress strain state of a submerged fluid filled Circular Cylindrical Shell subjected to a shock wave
    Journal of Fluids and Structures, 2004
    Co-Authors: Serguei Iakovlev
    Abstract:

    Abstract A submerged fluid-filled Circular Cylindrical Shell containing a rigid coaxial Cylindrical core is considered. The nonstationary dynamics of such a system subjected to an external spherical shock wave is examined, with particular emphasis on the influence that a core has on the stress–strain state of the Shell. A complete diffraction–radiation problem is considered, and an analytical–numerical solution of the problem is obtained. The influence of several different cores is analyzed, and a comparison to the case of a Shell without a core is presented. Physical phenomena occurring in the Shell and in the internal fluid are studied in detail. Two- and three-dimensional graphics is used to illustrate and analyze the nonstationary dynamics of the stress–strain state. The possibility of using a rigid core as a measure of constructive safety improvement is discussed.

  • interaction of a spherical shock wave and a submerged fluid filled Circular Cylindrical Shell
    Journal of Sound and Vibration, 2002
    Co-Authors: Serguei Iakovlev
    Abstract:

    Abstract The complete three-dimensional interaction between a spherical shock wave and a submerged fluid-filled elastic Circular Cylindrical Shell is considered. A hybrid analytical–numerical solving procedure is established. An exact analytical solution in the form of double Fourier series with time-depending coefficients is obtained for the hydrodynamic pressure. Displacements of a Shell are approached analytically to reduce the problem to a set of systems of ordinary differential equations, which are treated numerically. Detailed analysis of the interaction is performed with emphasis given to the stress–strain state. A few important features of the interaction process have been found. In particular, it has been shown that the interior fluid not only substantially affects the magnitude of displacements and stresses, but also dramatically changes the nature of the interaction. It has been found that the absolute maximum of stresses can neither be caused by a direct action of a shock wave nor by a constructive superpose of elastic waves in the Shell, but by the pressure wave propagating in the interior fluid. This fact seems to be of essential importance for engineering applications, especially when safety is a primary design concern. Another important result is that the maximum stresses are attained at large times, which makes use of early time asymptotics leading to incorrect results. The proposed semi-analytical approach seems to be computationally attractive and suitable for extensive numerical simulations.

Marco Amabili - One of the best experts on this subject based on the ideXlab platform.

  • nonlinear damped vibrations of three phase cnt frc Circular Cylindrical Shell
    Composite Structures, 2021
    Co-Authors: Amit Yadav, Marco Amabili, Sarat Kumar Panda, Tanish Dey, Rajesh Kumar
    Abstract:

    Abstract This study presents a semi-analytical solution of nonlinear vibrations of Circular Cylindrical Shells made of carbon nanotube (CNT) fiber-reinforced composite (CNT-FRC). Vibrations are produced by a radial harmonic force and viscous structural damping is considered. The effective properties of a lamina of the CNT-FRC Shell are evaluated in two steps. The elastic properties of randomly distributed CNTs in a polymeric matrix (i.e., hybrid matrix) are computed by the Eshelby-Mori-Tanaka/Voigt scheme to consider the CNTs agglomeration effect in the hybrid matrix. Then, the resulting hybrid matrix is reinforced with aligned fibers in order to prepare the lamina of the CNT-FRC Shell; its effective properties are estimated by the Halpin Tsai homogenization approach. The CNT-FRC Shell is modelled incorporating the von Karman geometric nonlinearity and first-order shear deformation theory (FSDT). The nonlinear governing partial differential equations (PDEs) of the CNT-FRC Shells are derived by the Hamilton’s principle. These PDEs are discretized into ordinary differential equations (ODEs) by using the Galerkin’s method. The ODEs are solved by incremental harmonic balance method (IHB) in conjunction with the arclength continuation method to obtain the frequency-amplitude response of the Shell. The effect of different types of CNT agglomeration models, CNT mass fraction, agglomeration parameters and stacking sequence of laminates on the frequency-amplitude curves corresponding to forced and free nonlinear vibrations of the CNT-FRC Shell are studied in detail.

  • Nonlinear vibrations of a Circular Cylindrical Shell with multiple internal resonances under multi-harmonic excitation
    Nonlinear Dynamics, 2018
    Co-Authors: Ivan D. Breslavsky, Marco Amabili
    Abstract:

    The nonlinear response of a water-filled, thin Circular Cylindrical Shell, simply supported at the edges, to multi-harmonic excitation is studied. The Shell has opportune dimensions so that the natural frequencies of the two modes (driven and companion) with three circumferential waves are practically double than the natural frequencies of the two modes (driven and companion) with two circumferential waves. This introduces a one-to-one-to-two-to-two internal resonance in the presence of harmonic excitation in the spectral neighbourhood of the natural frequency of the mode with two circumferential waves. Since the system is excited by a multi-harmonic point-load excitation composed by first and second harmonics, very complex nonlinear dynamics is obtained around the resonance of the fundamental mode. In fact, at this frequency, both modes with two and three circumferential waves are driven to resonance and each one is in a one-to-one internal resonance with its companion mode. The nonlinear dynamics is explored by using bifurcation diagrams of Poincaré maps and time responses.

  • nonlinear vibrations of a Circular Cylindrical Shell with multiple internal resonances under multi harmonic excitation
    Nonlinear Dynamics, 2018
    Co-Authors: Ivan D. Breslavsky, Marco Amabili
    Abstract:

    The nonlinear response of a water-filled, thin Circular Cylindrical Shell, simply supported at the edges, to multi-harmonic excitation is studied. The Shell has opportune dimensions so that the natural frequencies of the two modes (driven and companion) with three circumferential waves are practically double than the natural frequencies of the two modes (driven and companion) with two circumferential waves. This introduces a one-to-one-to-two-to-two internal resonance in the presence of harmonic excitation in the spectral neighbourhood of the natural frequency of the mode with two circumferential waves. Since the system is excited by a multi-harmonic point-load excitation composed by first and second harmonics, very complex nonlinear dynamics is obtained around the resonance of the fundamental mode. In fact, at this frequency, both modes with two and three circumferential waves are driven to resonance and each one is in a one-to-one internal resonance with its companion mode. The nonlinear dynamics is explored by using bifurcation diagrams of Poincare maps and time responses.

  • Static and Dynamic Behavior of Circular Cylindrical Shell Made of Hyperelastic Arterial Material
    Journal of Applied Mechanics, 2016
    Co-Authors: Ivan D. Breslavsky, Marco Amabili, Mathias Legrand
    Abstract:

    Static and dynamic responses of a Circular Cylindrical Shell made of hyperelastic arterial material are investigated. The material is modeled as a combination of Neo-Hookean and Fung hyperelastic materials. Two pressure loads are implemented: distributed radial force and deformation-dependent pressure. The static responses of the Shell under these two different loads differ essentially at moderate strains, while the behavior is similar for small loads. The main difference is in the axial displacements that are much larger under distributed radial forces. Free and forced vibrations around pre-loaded configurations are analyzed. In both cases the nonlinearity of the single-mode (driven mode) response of the pre-loaded Shell is quite weak but a resonant regime with co-existing driven and companion modes is found with more complicated nonlinear dynamics.

  • reduced order models for nonlinear vibrations based on natural modes the case of the Circular Cylindrical Shell
    Philosophical Transactions of the Royal Society A, 2013
    Co-Authors: Marco Amabili
    Abstract:

    Reduced-order models are essential to study nonlinear vibrations of structures and structural components. The natural mode discretization is based on a two-step analysis. In the first step, the natural modes of the structure are obtained. Because this is a linear analysis, the structure can be discretized with a very large number of degrees of freedom. Then, in the second step, a small number of these natural modes are used to discretize the nonlinear vibration problem with a huge reduction in the number of degrees of freedom. This study finds a recipe to select the natural modes that must be retained to study nonlinear vibrations of an angle-ply laminated Circular Cylindrical Shell that the author has previously studied by using admissible functions defined on the whole structure, so that an accuracy analysis is performed. The higher-order shear deformation theory developed by Amabili and Reddy is used to model the Shell.

Moon K Kwak - One of the best experts on this subject based on the ideXlab platform.

  • free vibration analysis of a Circular Cylindrical Shell using the rayleigh ritz method and comparison of different Shell theories
    Journal of Sound and Vibration, 2015
    Co-Authors: Hyunwook Lee, Moon K Kwak
    Abstract:

    Abstract This study uses the Rayleigh–Ritz method to derive a dynamic model for the free vibration analysis of a Circular Cylindrical Shell. In particular, explicit expressions for the mass and stiffness matrices are obtained to easily implement a computer simulation under different Shell theories and boundary conditions. The dynamic model is constructed according to the Donnell–Mushtari theory, which is fully discussed herein, and then, dynamic models are constructed by using Sanders theory, Love–Timoshenko theory, Reissner theory, Flugge theory, and Vlasov theory. This paper also discusses the use of eigenfunctions of a uniform beam as admissible functions that produce compact expressions for the mass and stiffness matrices. The numerical results indicate that the Donnell–Mushtari theory is not sufficiently accurate to calculate the natural frequencies and that there is no discernible difference between the other Shell theories considered in this study.

  • active vibration control of a ring stiffened Cylindrical Shell in contact with unbounded external fluid and subjected to harmonic disturbance by piezoelectric sensor and actuator
    Journal of Sound and Vibration, 2013
    Co-Authors: Moon K Kwak, Dongho Yang
    Abstract:

    Abstract This paper is concerned with the suppression of vibrations and radiated sound of a ring-stiffened Circular Cylindrical Shell in contact with unbounded external fluid by means of piezoelectric sensors and actuators. The dynamic model of a Circular Cylindrical Shell based on the Sanders Shell theory was considered together with a ring stiffener model. The mass and stiffness matrices for a ring stiffener were newly derived in this study and added to the mass and stiffness matrices of the Cylindrical Shell, respectively. The fluid-added mass matrix, which was derived by using the baffled Shell theory, was also added to the mass matrix. Finally, the equations representing the piezoelectric sensor measurement and piezoelectric actuation complete the theoretical model for the addressed problem. The natural vibration characteristics of the ring-stiffened Cylindrical Shell both in air and in water were investigated both theoretically and experimentally. The theoretical predictions were in good agreement with the experimental results. An active vibration controller which can cope with a harmonic disturbance was designed by considering the modified higher harmonic control, which is, in fact, a band rejection filter. An active vibration control experiment on the submerged Cylindrical Shell was carried out in a water tank and the digital control system was used. The experimental results showed that both vibrations and radiation sound of the submerged Cylindrical Shell were suppressed by a pair of piezoelectric sensor and actuator.

  • free vibration analysis of a finite Circular Cylindrical Shell in contact with unbounded external fluid
    Journal of Fluids and Structures, 2010
    Co-Authors: Moon K Kwak
    Abstract:

    Abstract The free flexural vibration of a finite Cylindrical Shell in contact with external fluid is investigated. The fluid is assumed to be inviscid and irrotational. The Cylindrical Shell is modeled by using the Rayleigh–Ritz method based on the Donnell–Mushtari Shell theory. The fluid is modeled based on the baffled Shell model, which is applied to fluid–structure interaction problems. The kinetic energy of the fluid is derived by solving the boundary-value problem. The natural vibration characteristics of the submerged Cylindrical Shell are discussed with respect to the added virtual mass approach. In this study, the nondimensionalized added virtual mass incremental factor for the submerged finite Shell is derived. This factor can be readily used to estimate the change in the natural frequency of the Shell due to the presence of the external fluid. Numerical results showed the efficacy of the proposed method, and comparison with previous results showed the validity of the theoretical results.

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

  • approximate elasticity solution for a long and thick laminated Circular Cylindrical Shell of revolution
    International Journal of Solids and Structures, 1997
    Co-Authors: K Chandrashekhara, K Nanjunda S Rao
    Abstract:

    An approximate three-dimensional elasticity solution is presented for an infinite, thick, orthotropic as well as laminated Circular Cylindrical Shell of revolution subjected to distributed pinch load. The validity and the accuracy of the results of approximate solution has been established by comparing it with the results of an exact three-dimensional elasticity solution for single and multi- layered (hybrid) Shell of revolution. Numerical results have been presented for cross-ply laminated (O/90/0 and 90/O/90) infinite Circular Cylindrical Shell of revolution subjected to axisymmetric band and distributed pinch loads. These results have been compared with the classical and first-order shear deformation theories of Flugge and Donnell to assess the accuracy and limitations of the two- dimensional Shell theories.

  • assessment of Shell theories for the static analysis of cross ply laminated Circular Cylindrical Shells
    Thin-walled Structures, 1995
    Co-Authors: K Chandrashekhara, D Pavan V T G Kumar
    Abstract:

    This paper examines the accuracy of classical Shell theories (CST) according to Flugge, Sanders, Love and Donnell, with respect to the recently available three-dimensional elasticity solution, for cross-ply laminated Circular Cylindrical Shells under static loads. Further, a study has also been made to examine to what extent incorporation of first order shear deformation (FSDT), in aforementioned Shell theories, improves the results. In general, all the basic equations (for both CST and FSDT), of aforementioned Shell theories, have been presented in a unified form using tracer coefficients. A Navier type solution has been used to analyse both a simply supported Circular Cylindrical Shell of revolution and an all round simply supported Circular Cylindrical Shell panel. A parametric study has been carried out keeping in view the lamination schemes and geometrical parameters of the Shell. From the detailed comparisons of the results it has been shown that (i) Donnell's theory (CST and FSDT) could be in error for certain lamination schemes and geometrical parameters and (ii) improved results for stresses and displacements could be obtained by incorporating shear deformation on more accurate theory like Flugge (CST).

  • static analysis of a thick laminated Circular Cylindrical Shell subjected to axisymmetric load
    Composite Structures, 1993
    Co-Authors: K Chandrashekhara, B S Kumar
    Abstract:

    An exact solution for a thick, transversely isotropic, simply supported, Circular Cylindrical Shell subjected to axisymmetric load has been obtained by using a displacement function approach. This solution has been extended to unidirectional hybrid laminates. However, this solution in general is not applicable to cross-ply laminates. An approximate solution using an elasticity approach also has been presented for the analysis of hybrid and cross-ply laminates.The results obtained from the approximate solution have been compared with the exact solution. Numerical results have been presented for 3-ply laminates subjected to sinusoidal and band loads. To make the method computationally efficient, particularly for a laminated Shell, a transfer matrix approach has been presented and the application of this has been illustrated through an example of a 10-ply laminated Shell.

Francesco Pellicano - One of the best experts on this subject based on the ideXlab platform.

  • temperature gradient effect on dynamic properties of a polymeric Circular Cylindrical Shell
    Composite Structures, 2019
    Co-Authors: Antonio Zippo, Marco Barbieri, Francesco Pellicano
    Abstract:

    Abstract In this paper, an experimental study on the dynamic of Cylindrical Shells made of Polyethylene terephthalate (PET) is presented; a thermic gradient has been applied on a specimen of the present work to obtain a functionally gradient material (FGM) equivalent properties: the PET Shell had been exposed at a thermal temperature gradient in the range of its glass transition temperature of 79 °C. A complex setup has been specifically designed and built to characterise, with dynamic tests, the structural properties of the specimen on temperature change from −10 °C up to about 90 °C and under thermic gradient with different forcing load. Predicting the mechanical properties of Shells, panels and plates is one of the main concerns of structural engineers; since Shell elements present complicated stability behaviours, rich linear vibration spectra (high modal density), high sensitivity to perturbations and strong interactions with surrounding elements. The linear and dynamic behaviour have been investigated. The Shell behaviour is also investigated by means of a finite element model, in order to enhance the comprehension of experimental results.

  • experimental analysis of pre compressed Circular Cylindrical Shell under axial harmonic load
    International Journal of Non-linear Mechanics, 2017
    Co-Authors: Antonio Zippo, Marco Barbieri, Francesco Pellicano
    Abstract:

    Abstract In this paper the nonlinear dynamics of Circular Cylindrical Shells under axial static (compressive) and periodic resonant loads have been experimentally investigated, the goal is to study the dynamic scenario and to analyze nonlinear regimes. A special test rig has been developed for the experiment in order to apply a static axial load combined with a dynamic axial load. The setup allows for investigating the linear behavior under static preload by means of the usual modal testing techniques; moreover, it allows for analyzing the nonlinear response which occurs when the dynamic axial load is periodic and gives rise to complex resonances. The complex dynamics, arising when a periodic axial load excites the asymmetric (Shell like) modes, are analyzed by means of amplitude frequency diagrams, waterfall spectrum diagrams, bifurcation diagrams of Poincare maps; a deep analysis of time histories, spectra, phase portraits and Poincare maps completes the study of the complex dynamic scenario.

  • linear and nonlinear dynamics of a Circular Cylindrical Shell connected to a rigid disk
    Communications in Nonlinear Science and Numerical Simulation, 2007
    Co-Authors: Francesco Pellicano, K V Avramov
    Abstract:

    Abstract The dynamics of a Circular Cylindrical Shell carrying a rigid disk on the top and clamped at the base is investigated. The Sanders–Koiter theory is considered to develop a nonlinear analytical model for moderately large Shell vibration. A reduced order dynamical system is obtained using Lagrange equations: radial and in-plane displacement fields are expanded by using trial functions that respect the geometric boundary conditions. The theoretical model is compared with experiments and with a finite element model developed with commercial software: comparisons are carried out on linear dynamics. The dynamic stability of the system is studied, when a periodic vertical motion of the base is imposed. Both a perturbation approach and a direct numerical technique are used. The perturbation method allows to obtain instability boundaries by means of elementary formulae; the numerical approach allows to perform a complete analysis of the linear and nonlinear response.

  • parametric instability of a Circular Cylindrical Shell with geometric imperfections
    Computers & Structures, 2004
    Co-Authors: Giulia Catellani, Francesco Pellicano, D Dallasta, Marco Amabili
    Abstract:

    Abstract The static and dynamic behavior of a compressed Circular Cylindrical Shell having geometric imperfections is analyzed. The analysis is mainly performed by means of the Donnell’s nonlinear shallow-Shell theory. However, the refined Sanders Shell theory is also used for comparison. A suitable expansion of the radial displacement, able to describe both buckling and dynamic behaviors is developed; the effect of geometric imperfections is accounted for by means of a modal representation. The response of the Shell subjected to a sinusoidal axial excitation at its ends, giving rise to a parametric excitation, is considered. The effect of imperfections on the critical value of the dynamic load, that causes the loss of stability of the system, is analyzed. Interesting nonlinear dynamic phenomena are observed: direct resonance with softening behavior and parametric instability with period doubling response.