scholarly journals Prediction of Vibrational Behavior of Grid-Stiffened Cylindrical Shells

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
G. H. Rahimi ◽  
M. Hemmatnezhad ◽  
R. Ansari
Keyword(s):  
Shell Theory ◽  
Cylindrical Shells ◽  
Element Model ◽  
Geometrical Parameters ◽  
Equivalent Stiffness ◽  
Theoretical Formulation ◽  
Vibrational Behavior ◽  
Thin Shell Theory ◽  
Stiffened Cylindrical Shells ◽  
Good Agreement

A unified analytical approach is applied to investigate the vibrational behavior of grid-stiffened cylindrical shells with different boundary conditions. A smeared method is employed to superimpose the stiffness contribution of the stiffeners with those of shell in order to obtain the equivalent stiffness parameters of the whole panel. Theoretical formulation is established based on Sanders’ thin shell theory. The modal forms are assumed to have the axial dependency in the form of Fourier series whose derivatives are legitimized using Stoke's transformation. A 3D finite element model is also built using ABAQUS software which takes into consideration the exact geometric configuration of the stiffeners and the shell. The achievements from the two types of analyses are compared with each other and good agreement has been obtained. The Influences of variations in shell geometrical parameters, boundary condition, and changes in the cross stiffeners angle on the natural frequencies are studied. The results obtained are novel and can be used as a benchmark for further studies. The simplicity and the capability of the present method are also discussed.

Collapse of Thin Orthotropic Elliptical Cylindrical Shells Under Combined Bending and Pressure Loads

1979 ◽  
Vol 46 (2) ◽  
pp. 363-371 ◽  
Author(s):  
J. Spence ◽  
S. L. Toh
Keyword(s):  
Shell Theory ◽  
Nonlinear Boundary ◽  
Cylindrical Shells ◽  
Normal Pressure ◽  
Nonlinear Ordinary Differential Equations ◽  
Pure Bending ◽  
Finite Deflection ◽  
Shooting Technique ◽  
Theoretical Predictions ◽  
Thin Shell Theory

The elastic collapse of thin orthotropic elliptical cylindrical shells subject to pure bending alone or combined bending and uniform normal pressure loads has been studied. Nonlinear finite deflection thin shell theory is employed and this reduces the problem to a set of nonlinear ordinary differential equations. The resulting two-point nonlinear boundary-value problem is then linearized, using quasi-linearization, and solved numerically by the “shooting technique.” Some experimental work has been carried out and the results are compared with the theoretical predictions.

Acoustic and Vibration Characteristics of Stiffened Finite Cylindrical Shells in Water under Multiple Axial-Excitations

2013 ◽  
Vol 662 ◽  
pp. 721-725
Author(s):  
Qi Zheng Zhou ◽  
De Shi Wang ◽  
Sheng Yao Gao
Keyword(s):  
Analytical Solution ◽  
Shell Theory ◽  
Acoustic Pressure ◽  
Acoustic Radiation ◽  
Cylindrical Shells ◽  
High Frequencies ◽  
Acoustic Coupling ◽  
Coupling Equations ◽  
Vibration And Sound Radiation ◽  
Thin Shell Theory

A research on the vibration and acoustic radiation of stiffened finite cylindrical shells in water under a multiple axial-excitations driven was presented. The vibro-acoustic coupling equations of shell under multiple axial-excitations based on Flügge thin shell theory were established. The displacements, surface acoustic pressure and stiffener impedances were expressed in terms of the numbers of normal modals and modes, and considering multiple excitations, the forces were expressed in terms of the numbers of normal modals and modes. Then analytical solution was derived for the vibration and sound radiation from the stiffened shell under multiple excitations. Based on the analytical solution, the influences of excitations’ positions to the vibration and acoustic radiation were investigated. The results show that for double excitations, at high frequencies, the distance between excitations was more large, the average velocity was more low. The results could be used to control the underwater vehicle’s vibration and acoustic radiation.

A Finite Element Model for Bending Buckling of Single Wall Carbon Nano-Tubes and Investigation of Geometrical Parameters on it

2008 ◽  
Author(s):  
Ali Hemmasizadeh ◽  
Reza Kamali ◽  
Ehsan Hadi ◽  
Rasoul Khandan
Keyword(s):  
Finite Element ◽  
Shell Theory ◽  
Elastic Shell ◽  
Single Walled Carbon Nanotubes ◽  
Element Model ◽  
Dynamics Simulation ◽  
Geometrical Parameters ◽  
Buckling Behavior ◽  
Carbon Nano Tubes ◽  
Walled Carbon Nanotubes

Bending buckling behavior of single-walled carbon nanotubes (SWCNTs) is modeled by means of finite element method (FEM) and the relations between critical bending buckling curvature and geometrical parameters of nanotubes are determined. Elastic modulus and wall thickness of nanotubes are chosen in a way that elastic shell theory is capable of predicting mechanical properties of nanotubes. The effect of initial internal stress state through the shell thickness is investigated. Computed results are very close to the results of molecular dynamics simulation.

Effect of Ring Support Position and Geometrical Dimension on the Free Vibration of Ring-Stiffened Cylindrical Shells

2014 ◽  
Vol 580-583 ◽  
pp. 2879-2882
Author(s):  
Xiao Wan Liu ◽  
Bin Liang
Keyword(s):  
Cylindrical Shell ◽  
Free Vibration ◽  
Shell Theory ◽  
Cylindrical Shells ◽  
Ritz Method ◽  
Geometrical Dimension ◽  
Stiffened Cylindrical Shell ◽  
Simply Supported ◽  
Ring Support ◽  
Stiffened Cylindrical Shells

Effect of ring support position and geometrical dimension on the free vibration of ring-stiffened cylindrical shells is studied in this paper. The study is carried out by using Sanders shell theory. Based on the Rayleigh-Ritz method, the shell eigenvalue governing equation is derived. The present analysis is validated by comparing results with those in the literature. The vibration characteristics are obtained investigating two different boundary conditions with simply supported-simply supported and clamped-free as the examples. Key Words: Ring-stiffened cylindrical shell; Free vibration; Rayleigh-Ritz method.

Laminated Transversely Isotropic Cylindrical Shells

1971 ◽  
Vol 38 (2) ◽  
pp. 400-407 ◽  
Author(s):  
J. A. Zukas ◽  
J. R. Vinson
Keyword(s):  
Shell Theory ◽  
Transverse Isotropy ◽  
Cylindrical Shells ◽  
Pyrolytic Graphite ◽  
Transversely Isotropic ◽  
Sample Problem ◽  
Governing Equations ◽  
Slow Cooling ◽  
Circular Cylindrical Shells ◽  
Thin Shell Theory

A theory for the analysis of stresses in laminated circular cylindrical shells subjected to arbitrary axisymmetric mechanical and thermal loadings has been developed. This theory, specifically for use with pyrolytic-graphite-type materials, differs from the classical thin shell theory in that it includes the effects of transverse shear deformation and transverse isotropy, as well as thermal expansion through the shell thickness. Solutions in several forms are developed for the governing equations. The form taken by the solution function is governed by geometric considerations. A range in which the various solution forms occur was determined numerically. As a sample problem, the slow cooling of pyrolytic graphite deposited onto a commercial graphite mandrel was considered. Investigation of normal and shear stress behavior at the pyrolytic graphite-mandrel interface showed that these stresses decrease in magnitude with increasing E/Gc ratio and increasing deposit to mandrel thickness (ha/hb) ratio. This implies that a thin mandrel and a material weak in shear are desirable to minimize the possibilities of flaking and delamination of the pyrolytic graphite.

scholarly journals Computational Approach in Formulating Mechanical Characteristics of 3D Star Honeycomb Auxetic Structure

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Mozafar Shokri Rad ◽  
Zaini Ahmad ◽  
Amran Alias
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Element Model ◽  
Honeycomb Structure ◽  
Geometrical Parameters ◽  
Theoretical Formulation ◽  
Design Guideline ◽  
Structural Cell ◽  
Auxetic Materials ◽  
Structural Applications

Auxetic materials exhibit a unique characteristic due to the altered microstructure. Different structures have been used to model these materials. This paper treats a development of finite element model and theoretical formulation of 3D star honeycomb structure of these materials. Various shape parameters of the structural cell were evaluated with respect to the basic mechanical properties of the cell. Finite element and analytical approach for various geometrical parameters were numerically used to formulate the characteristics of the material. The study aims at quantifying mechanical properties for any domain in which auxetic material is of interest for variations in geometrical parameters. It is evident that mechanical properties of the material could be controlled by changing the base wall angle of the configuration. The primary outcome of the study is a design guideline for the use of 3D star honeycomb auxetic cellular structure in structural applications.

Estimation of local myocardial stress

1982 ◽  
Vol 242 (5) ◽  
pp. H875-H881 ◽  
Author(s):  
R. F. Janz
Keyword(s):  
Shell Theory ◽  
Circumferential Stress ◽  
Element Model ◽  
Thick Wall ◽  
Ventricular Wall ◽  
Cavity Pressure ◽  
General Representation ◽  
Myocardial Stress ◽  
Local Average ◽  
Good Agreement

Two formulas are presented for estimating local average circumferential stress in the left ventricle from the cavity pressure and various quantities, available from the angiogram, which characterize the size and shape of the cavity and ventricular wall. The advantages of these formulas are as follows: 1) they are based on thick-wall shell theory; 2) they are intended for application at positions in the ventricular wall other than the base; and 3) they are based on a more general representation of ventricular geometry than a sphere, cylinder, or ellipsoid. Except for one location, both formulas predict average circumferential stresses that agree to within 25% with the corresponding stresses in a finite element model of an aneurysmal ventricle. In addition, at the equator of a thick-wall ellipsoid, the formulas are identical in form to a previously derived formula that has been shown to predict stresses that are in fair to good agreement with measured stresses in the open-chest dog heart.

Vibro-Acoustics Characteristics of Non-Uniform Ring Stiffened Cylindrical Shells Using Wave Propagation Approach

2013 ◽  
Vol 655-657 ◽  
pp. 562-567 ◽  
Author(s):  
Bing Ru Li ◽  
Yue Peng Jiang ◽  
Xuan Yin Wang ◽  
Hui Liang Ge
Keyword(s):  
Wave Propagation ◽  
Cylindrical Shells ◽  
Stiffened Cylindrical Shell ◽  
Various Boundary Conditions ◽  
Structural Loss ◽  
Basic Equations ◽  
Vibration And Sound Radiation ◽  
Uniform Ring ◽  
Thin Shell Theory ◽  
Stiffened Cylindrical Shells

Based on Donnell’s thin shell theory and basic equations, the wave propagation method is discussed here in detail, which is used to investigate the vibration and sound radiation characteristics of non-uniform ring stiffened cylindrical shells under various boundary conditions. The structure damp effects of cylindrical shells are investigated and the ring ribs were considered very narrow, and the rib forces are considered in radial direction. The conclusion are drawn that with the structural loss factor changing large, the whole pressure level are changed little, but the peak of resonance are slacking down obviously; The shell’s resonance frequency can be changed with irregular ring stiffened cylindrical shell .The work will give some guidelines for noise reduction of this kind of shell.

Non-Axisymmetric Vibrations of Stepped Cylindrical Shells Containing Cracks

2014 ◽  
Vol 934 ◽  
pp. 136-142
Author(s):  
Larissa Roots
Keyword(s):  
Shell Theory ◽  
Natural Frequencies ◽  
Cylindrical Shells ◽  
Axisymmetric Vibration ◽  
Approximate Evaluation ◽  
Linear Fracture ◽  
Local Flexibility ◽  
Circular Cylindrical Shells ◽  
Thickness Variations ◽  
Thin Shell Theory

Based on the Donnell’s approximations of the thin shell theory, this paper presents solutions for the problem of free non-axisymmetric vibration of stepped circular cylindrical shells with cracks. The shell under consideration is sub-divided into multiple segments separated by the locations of thickness variations. It is assumed that at thejth step there exists a circumferential surface crack with uniform depthcj. The influence of circular cracks with constant depth on the vibration of the shell is prescribed with the aid of a matrix of local flexibility. The latter is related to the coefficient of the stress intensity known in the linear fracture mechanics. Numerical results are obtained for cylindrical shells of stepped thickness containing cracks at re-entrant corners of steps. Shells with various combinations of boundary conditions can be analyzed by the proposed method. Furthermore, the influences of the shell thicknesses, locations of step-wise variations of the thickness and other parameters on the natural frequencies are examined. The results can be used for the approximate evaluation of dynamic parameters of cylindrical shells with cracks and flaws.

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