As an effective approach to suppress vibrations and noise, passive constrained layer damping (PCLD) treatments are widely used in engineering practice. However most of the studies concentrate on th...

Vibration and damping characteristics of sandwich plates with viscoelastic core

Earthquake induced dynamic deflection of submerged viscoelastic cylindrical shell reinforced by agglomerated CNTs considering thermal and moisture effects

Control of sound and vibration of fluid-filled cylindrical shells via periodic design and active control

Control of sound and vibration for cylindrical shells by utilizing a periodic structure of functionally graded material

This paper presents the fundamental problem of three-dimensional acoustic wave transmission through a sandwich structure with viscoelastic core excited by an obliquely plane wave. The structure consists of a functionally graded shell as an outer layer, an isotropic layer as an inner layer and also a viscoelastic core. This work considers Havriliak-Negami model for description of complex modulus of viscoelastic core. The Havriliak-Negami model is a new mathematical method for the simulation of polymeric relaxation behavior in the frequency domain. In this model, both of complex Young’s and shear moduli are frequency dependent. Moreover, considering the effective roles of shear deformation and rotary inertia, dynamic governing equations of the functionally graded cylinder, viscoelastic core and isotropic shell are derived within the frameworks of the three-dimensional theory of elasticity. Furthermore, analytical model of acoustic wave transmission based on transfer matrix method is composed of a set of fluid and structural equations which taking into account the frequency dependency of mechanical characterization for the viscoelastic core. A good agreement can be observed, comparing the present results with those of other authors. Besides, the results show that a double-walled cylinder with viscoelastic core has a better acoustic insulation in comparison with isotropic shell with the same mass. Contrary to elastic material, by thickening the viscoelastic layer, sound transmission loss decreases in mass-controlled region due to shear deformation and rotary inertia. It has been also proved that polymer with a larger loss factor has good performance in energy dissipation.

Incorporating the Havriliak–Negami model in wave propagation through polymeric viscoelastic core in a laminated sandwich cylinder

The novel features of the Havriliak-Negami model for dynamic description of viscoelastic material behavior along with the Donnell theory of shell motion are applied to study free vibrational and damping characteristics of an infinitely long viscoelastic thin circular cylindrical shell submerged in and filled with acoustic fluids. The analytical results are illustrated with numerical examples in which two fluid-filled shells of distinctive viscoelastic material properties are undergoing free vibrations in a surrounding ideal fluid medium. The natural frequencies and the associated modal loss factors as a function of the circumferential mode number at selected axial wave lengths and submergence conditions are numerically evaluated and discussed. The numerical results reveal the imperative influence of dynamic viscoelastic properties on the vibrational characteristics of the fluid-coupled system. They demonstrate an interesting correlation between the modal loss factor and the material loss factor in the vic...

M. Shahsavarifard

Papers

Dynamic Viscoelastic Effects on Free Vibrations of a Submerged Fluid-filled Thin Cylindrical Shell