The finite element code is developed based on the displacement field proposed by Wilkins et al. to find out the natural frequencies and loss factors of fluid filled cylindrical shells with a constrained viscoelastic layer in between two facings made of composite material. The fluid effect on the natural frequencies and loss factors are taken care of by the added mass of the fluid on the structure. Effects of the fluid height, ratio of core to facing thickness and facing fibre orientation on the natural frequencies and loss factors of cylindrical shells are presented.

R. Ramasamy

Natrajan Ganesan

Computer simulation

Constraint theory

Cylinders (shapes)

Damping

finite element method

Natural frequencies

Vibrations (mechanical)

Viscoelasticity

CONSTRAINED VISCOELASTIC LAYERS

FLUID EFFECT

Loss factor

Shells (structures)

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Vibration and damping analysis of fluid filled orthotropic cylindrical shells with constrained viscoelastic damping

Computers and Structures

A formulation, based on the semi-analytical finite element method, is proposed for elastic conical shells conveying fluids. The structural equations are based on the shell element proposed by Ramasamy and Ganesan [Finite element analysis of fluid-filled isotropic cylindrical shells with constrained viscoelastic damping, Computers & Structures 70 (1998) 363-376] while the fluid model is based on velocity potential formulation used by Jayaraj et al. [A semi-analytical coupled finite element formulation for composite shells conveying fluids, Journal of Sound and Vibration 258(2) (2002) 287-307]. Dynamic pressure acting on the walls is derived from Bernoulli's equation. By imposing the requirement that the normal component of velocity of the solid and fluid are equal leads to fluid-structure coupling. The computer code developed has been validated using results available in the literature for cylindrical shells conveying fluid. The study has been carried out for conical shells of different cone angles and for boundary condition like clamped-clamped, simply supported and clamped free. In general, instability occurs at a critical fluid velocity corresponding to the shell circumferential mode with the lowest natural frequency. Critical fluid velocities are lower than that of equivalent cylindrical shells. This result holds good for all boundary conditions. © 2007 Elsevier Ltd. All rights reserved.

Journal of Sound and Vibration

Dynamic analysis of conical shells conveying fluid

This article presents the frequency and damping characteristics of sandwich conical shell structures with electro-rheological fluid (ER) core. The dynamic characteristics of conical shell for different core to facing thickness ratio (tc/tf), length to mean radius (L/R) ratio and effect of cone angle on frequency and damping for different boundary conditions are carried out. The variation of damping characteristics of electro-rheological fluid core with electric voltage is also investigated. © Springer Science + Business Media B.V. 2008.

Springer Proceedings in Physics

Free vibration analysis of truncated sandwich conical shells with constrained electro-rheological fluid damping

Conventional cylindrical shells (made of isotropic materials) filled with or submerged in fluid have been analysed historically by using closed-form solutions or by semi-analytical method. However, these shells suffer from a serious disadvantage of not having sufficient damping, which is crucial in controlling the response of the structure during severe vibrations. One practical way of reducing response levels is by using shells with viscoelastic treatment that would result in increased damping. Previous work in this area was mostly limited to study problems whose mathematical formulation was amenable to closed-form solution or semi-analytical method. In some cases researchers resorted to experimental studies. Further, almost all previous studies were limited to lower circumferential modes and to first axial mode only. In the present paper, the method proposed overcomes most of the limitations suffered by adopting the different approaches suggested in literature. The method consists of treating fluid domain with Bessel function approach and shell domain based on first-order shear deformation theory. The present approach obviates the discretisation of liquid domain thus reducing the computation time. A computer program is developed based on the proposed method and results are compared with previous works of various researchers. A good correlation is observed for all the case studies done. Hence, it is claimed that the present approach is more universal for analysing fluid-filled or submerged shells or both. Detailed parametric studies are carried out on both conventional and viscoelastic cylindrical shells. © 2007 Elsevier Ltd. All rights reserved.

Studies on fluid-filled and submerged cylindrical shells with constrained viscoelastic layer

Cylindrical shells find wide applications in many engineering fields. Free vibration analysis of cylindrical shells filled with fluid has been dealt using finite element approach for both structure and fluid domain or using finite element for structure and Bessel function approach for fluid. The present paper deals with a novel method on the usage of polynomial functions for fluid domain in contrast to the usual Bessel function approach. A semi-analytical finite element approach has been used to discretise the shell structure. The fluid domain has been analysed by using polynomial functions instead of Bessel function. The study has been carried out for conventional shells as well as viscoelastic shells. The present study obviates necessity of limiting the studies to certain boundary conditions. The results of both frequency and damping corroborate well with those found in literature. © 2005 Elsevier Ltd. All rights reserved.

Polynomial approach for calculating added mass for fluid-filled cylindrical shells

In this article, buckling and vibration behavior of a functionally graded material (FGM) sandwich beam having constrained viscoelastic layer (VEL) is studied in thermal environment by using finite element formulation. The FGM sandwich beam is assumed to be clamped on both edges. The material properties of FGM are functionally graded in thickness direction according to volume fraction power law distribution. Temperature dependent material properties of FGM stiff layer and shear modulus of viscoelastic layer are considered to carry out buckling and vibration analysis. Numerical studies involving the understanding the effect of power law index, core to stiff layer ratio on the thermal buckling temperature as well as on vibration has been carried out. In addition influence of temperature on natural frequencies and loss factors have been examined for FGM sandwich beam. © 2006 Elsevier Ltd. All rights reserved.

Thermoelastic buckling and vibration behavior of a functionally graded sandwich beam with constrained viscoelastic core

The free vibration and damping characteristics of three-layered conical shells with a viscoelastic core constrained by isotropic facings are studied using the finite element method. Results are presented for shells with various geometric and physical parameters. Three boundary conditions are considered in the analysis: clamped-clamped, simply supported and clamped at the small end and free at the other. © 1994 Academic Press Limited.

Finite element analysis of conical shells with a constrained viscoelastic layer

The vibration and damping analysis of orthotropic cylindrical shells with a constrained viscoelastic core is carried out by using a finite element based on a discrete layer theory. The material damping of the facings is also included in the analysis. Results are represented for different geometric and material properties of the shell. The data and trends presented for various cases could be useful for designers in choosing damping treatments for composite shells. © 1994 Academic Press Limited.

Journal	Data powered by TypesetComputers and Structures
Publisher	Data powered by TypesetElsevier Ltd
ISSN	00457949
Open Access	No