Vibration and damping analysis of multilayered fluid filled cylindrical shells with constrained viscoelastic damping using modal strain energy method
TL;DR: A semianalytical finite element for doubly curved, multilayered shells of revolution, based on an extension of the displacement field proposed by Wilkins et al., is proposed in this paper.
About: This article is published in Computers & Structures.The article was published on 2000-04-01. It has received 24 citations till now. The article focuses on the topics: Modal testing & Natural frequency.
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TL;DR: In this paper , the modal damping and frequency response of functionally graded fiber-reinforced composite cylindrical shells considering the internal damping is analyzed. But the results of the analysis were not validated by comparing the results with those in the literature and finite element simulation.
Abstract: This paper presents research on the modal damping and frequency response of functionally graded fiber-reinforced composite cylindrical shells considering the internal damping. Based on the Love shell theory and energy approach, the dynamical equations of cylindrical shells are established. In the process of variable separation, the Haar wavelet series and trigonometric functions are respectively to represent the axial and circumferential modes. Based on the microscopic damping prediction method and multi-cell model of hybrid materials, the equivalent damping and elastic characteristics of composite materials are determined. Then the damping and frequency response characteristics are solved by the complex modulus method. The present analysis is validated by comparing the results with those in the literature and finite element simulation. The effects of fiber content and distribution, lamination and geometry configuration on damping and frequency response properties are further analyzed. The analysis show that the damping decreases monotonically with the increase of fiber volume fraction. The damping behaviors may be improved by changing the fiber distribution type and stacking sequence. Increasing the internal damping of composites can obviously reduce the vibration amplitude in the resonance region, especially in the high frequency range.
7 citations
TL;DR: In this paper, a thermal-vibration joint test system is developed for investigating the thermal modal characteristics of the ship's foundation under different temperatures, which consists of a transient aerodynamic heating environment simulation system and a vibration excitation and acquisition system.
Abstract: How to further reduce vibration and noise is a major challenge for modern ship design. High-temperature environment will significantly influence the mechanical properties (such as elastic modulus and stiffness) of the ship’s foundation. These properties will have a serious impact on the inherent vibration characteristics of the foundation. In this paper, a simplified foundation is taken as the research object, and a thermal-vibration joint test system is developed for investigating the thermal modal characteristics of the foundation under different temperatures. The joint test system consists of a transient aerodynamic heating environment simulation system and a vibration excitation and acquisition system. Finite element method (FEM) is used to analyze the distribution of thermal fields. The influence of the ceramic rods and the different ambient temperatures on the modal characteristics of the foundation is studied. The results indicate that the effect of ceramic rods on the modal characteristic of the foundation is negligible. The results also show that the greater the vibration response amplitude is as the temperature increases and the first-order natural frequency does not change, the smaller the second-order natural frequency and the damping ratio will become smaller. The variation of natural frequency and damping ratio of the foundation under different temperature conditions can provide a reliable experimental basis for the design of the vibration and noise reduction of the ship’s foundation in the thermal-vibration environment.
6 citations
TL;DR: In this paper, the buckling and vibration behavior of a viscoelastic sandwich cylinder in a thermal environment analyzed using the semi analytical finite element method is presented, and the analysis is carried out using a decoupled thermo mechanical formulation.
Abstract: This paper presents the buckling and vibration behavior of a viscoelastic sandwich cylinder in a thermal environment analyzed using the semi analytical finite element method. The analysis is carried out using a decoupled thermo mechanical formulation. The temperature field in the shell domain is evaluated using an eight-noded axisymmetric ring element. Buckling and vibration analyses are carried out using a two-noded sandwich shell element in the semi-analytical finite element method. Buckling temperatures are calculated for sandwich shells with two different core materials. The effect of temperature-dependent core shear modulus on buckling temperature and vibration behavior has been investigated for sandwich shells with different mechanical boundary conditions. Variations of natural frequencies and loss factors with temperature have also been examined for sandwich shells with two different core materials.
6 citations
Cites background from "Vibration and damping analysis of m..."
...[ 2 ] have analyzed the vibration behavior of multi-layer fluid filled tanks by making use of semi–analytical finite element method....
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TL;DR: In this article , two new methods for solving nonlinear eigenvalue problems of the viscoelastic damped cylindrical shell are proposed, which do not need to perform eigenvector calculations.
Abstract: The dynamic model of the cylindrical shell partially attached with a viscoelastic free damping layer is established by a semi-analytical method, and the complex boundary conditions of the cylindrical shell are simulated by using the non-uniform distribution of spring groups. Two new methods for solving nonlinear eigenvalue problems of the viscoelastic damped cylindrical shell are proposed. One method is named as the Vector Iteration method based on Approximate Eigenvalues (VIAE), and the solution process can be described as: the iteration equation is obtained by the characteristic equation; the approximate eigenvalue and the initial eigenvector are used for the iteration calculation; in each iteration, the eigenvectors are normalized and the nonlinear eigenvalues are obtained by using the Rayleigh quotient. Another method is named as the Secant Method of Characteristic Polynomials (SMCP). In this method, the iteration equation of the eigenvalue is derived by the secant method. Furthermore, the approximate eigenvalues of the system are used as the initial iteration eigenvalues and the nonlinear eigenvalues of the system can be approximated through several iteration calculations. Finally, the proposed modeling method and algorithm are verified by the experiment of the actual cylindrical shell attached the ZN-1 viscoelastic material at the free end. The two new methods were also compared with the classical Eigenvector Increment Method (EIM). The comparison results show that the VIAE algorithm has the highest efficiency, and both the VIAE and SMCP algorithms have wider applicability because they do not need to perform eigenvector calculations.
4 citations
TL;DR: In this paper , the buckling loads of a composite sandwich structure, which is reinforced by a honeycomb layer and filled with viscoelastic damping material, are analyzed by applying von Karman anisotropic plate equations for large deflection.
Abstract: In this study, the buckling loads of a composite sandwich structure, which is reinforced by a honeycomb layer and filled with viscoelastic damping material, are analyzed. By applying von Karman anisotropic plate equations for large deflection, the governing equation of the composite sandwich structure is determined, and the deflection of the structure is further defined by a double triangular series. According to the dynamic equivalent effective stiffness obtained by the homogenous asymptotic method and Hill’s generalized self-consistent model based on the Halpin–Tsai model, limiting the dynamic load buckling of the composite honeycomb reinforced sandwich structure embedded with viscoelastic damping material under axial compression can be achieved. The factors that influence the composite sandwich’s buckling loads are discussed and compared, such as the load and geometry parameters, the thickness of the honeycomb reinforcement layer and the honeycomb’s width. Finally, the results obtained by the present method are validated by the existing literature.
2 citations
References
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TL;DR: A review of computational models for sandwich plates and shells, predictor-corrector procedures, and the sensitivity of the sandwich response to variations in the different geometric and material parameters can be found in this article.
Abstract: The focus of this review is on the hierarchy of computational models for sandwich plates and shells, predictor-corrector procedures, and the sensitivity of the sandwich response to variations in the different geometric and material parameters. The literature reviewed is devoted to the following application areas: heat transfer problems; thermal and mechanical stresses (including boundary layer and edge stresses); free vibrations and damping; transient dynamic response; bifurcation buckling, local buckling, face-sheet wrinkling and core crimping; large deflection and postbuckling problems; effects of discontinuities (eg, cutouts and stiffeners), and geometric changes (eg, tapered thickness); damage and failure of sandwich structures; experimental studies; optimization and design studies. Over 800 relevant references are cited in this review, and another 559 references are included in a supplemental bibliography for completeness. Extensive numerical results are presented for thermally stressed sandwich panels with composite face sheets showing the effects of variation in their geometric and material parameters on the accuracy of the free vibration response, and the sensitivity coefficients predicted by eight different modeling approaches (based on two-dimensional theories). The standard of comparison is taken to be the analytic three-dimensional thermoelasticity solutions. Some future directions for research on the modeling of sandwich plates and shells are outlined.
740 citations
TL;DR: In this article, an efficient method for finite element modeling of three-layer laminates containing a viscoelastic layer is described, and modal damping ratios are estimated from undamped normal mode results by means of the modal strain energy method.
Abstract: An efficient method is described for finite element modelling of three-layer laminates containing a viscoelastic layer. Modal damping ratios are estimated from undamped normal mode results by means of the modal strain energy method. Comparisons are given between results obtained by the MSE method implemented in NASTRAN, by various exact solutions for approximate governing differential equations, and by experiment. Results are in terms of frequencies, modal damping ratios, and mechanical admittances for simple beams, plates, and rings. Application of the finite element -- MSE method in design of integrally damped structures is discussed.
542 citations
TL;DR: In this article, the authors re-examined the definition of loss factor in terms of energy quantities, particularly as it applies to composite viscoelastic systems, and proposed simple relations which express the loss factors of series-parallel arrays of massless VRSs.
Abstract: The definition of loss factor in terms of energy quantities is re‐examined, particularly as it applies to composite viscoelastic systems. A restatement of this definition in terms of a corresponding viscoelastic spring is used to show that this definition is extremely useful for massless (ideal viscoelastic spring) systems, but may be applied unambiguously to spring systems with a single attached mass only at resonance. Simple relations are presented which express the loss factors of series‐parallel arrays of massless viscoelastic springs in terms of properties of the individual components. Implications of these relations in damping of composite structures are discussed. (This work was supported in part by the Aeronautical Systems Division, U. S. Air Force.)
319 citations
TL;DR: In this paper, the effects of the shear parameter on the frequency and loss factors for various geometric properties and boundary conditions are also discussed for cylindrical shells with different core to facing thickness and length to radius ratios.
80 citations