THE EFFECTS OF LARGE VIBRATION AMPLITUDES ON THE MODE SHAPES AND NATURAL FREQUENCIES OF THIN ELASTIC SHELLS. PART II: A NEW APPROACH FOR FREE TRANSVERSE CONSTRAINED VIBRATION OF CYLINDRICAL SHELLS

2002 ◽  
Vol 255 (5) ◽  
pp. 931-963 ◽  
Author(s):  
F. MOUSSAOUI ◽  
R. BENAMAR ◽  
R.G. WHITE
Keyword(s):  
Natural Frequencies ◽  
Cylindrical Shells ◽  
Mode Shapes ◽  
Elastic Shells ◽  
New Approach

Analytical and Experimental Modal Characteristics of Cylindrical Shells

2005 ◽  
Author(s):  
Basem Alzahabi
Keyword(s):  
Natural Frequency ◽  
Natural Frequencies ◽  
Cylindrical Shells ◽  
Offshore Structures ◽  
Operating Conditions ◽  
Mode Shapes ◽  
Design Stage ◽  
Scaled Model ◽  
Modal Characteristics ◽  
Acoustic Signature

Cylindrical Shells are widely used in many structural designs, such as offshore structures, liquid storage tanks, submarine hulls, and airplane hulls. Most of these structures are required to operate in a dynamic environment. The acoustic signature of submarines is very critical in such high performance structure. Submarines are not only required to sustain very high dynamic loadings at all time, but also being able maneuver and perform their functions under sea without being detected by sonar systems. Reduction of sound radiation is most efficiently achieved at the design stage, and the acoustic signatures may be determined by considering operational scenarios, and modal characteristics. The acoustic signature of submarines is generally of two categories; broadband which has a continuous spectrum; and a tonal noise which has discrete frequencies. Therefore, investigating the dynamic characteristics of cylindrical shells is very critical first step in developing a strategy for modal vibration control for specific operating conditions. Unlike those of beam structure, the lowest natural frequency does not necessarily correspond to the lowest wave index. In fact, the natural frequencies do not fall in ascending order of the wave index in cylindrical shells. Mode shapes associated with each natural frequency are combination of Radial, Longitudinal, and Circumferential modes. In this paper, a scaled model of submarine hull segment under shear diaphragm boundary conditions is analyzed analytically and numerically. Then experimental modal analysis of the scaled model utilizing a fixed response approach was performed to obtain the modal characteristics of the cylindrical shell between 0 and 800 Hz. The cylinder was excited at predetermined points with an impact hammer, while the response was measured using an accelerometer at specified fixed point. Designing a boundary condition that simulate a shear diaphragm is very challenging task by itself. A total of ten natural frequencies were found within that range with their corresponding mode shapes. The experimental data were correlated with those results obtained analytically and numerically using the finite element methods using MSC.NASTRAN software. The results were found to be in excellent agreement.

Analysis of Ring-Stiffened Cylindrical Shells

1995 ◽  
Vol 62 (4) ◽  
pp. 1005-1014 ◽  
Author(s):  
Bingen Yang ◽  
Jianping Zhout
Keyword(s):  
Natural Frequencies ◽  
Transfer Functions ◽  
Cylindrical Shells ◽  
Middle Surface ◽  
Mode Shapes ◽  
Structural Components ◽  
Modeling And Analysis ◽  
Stiffened Shells ◽  
Modeling Techniques ◽  
Stiffened Cylindrical Shells

A new analytical and numerical method is presented for modeling and analysis of cylindrical shells stiffened by circumferential rings. This method treats the shell and ring stiffeners as individual structural components, and considers the ring eccentricity with respect to the shell middle surface. Through use of the distributed transfer functions of the structural components, various static and dynamic problems of stiffened shells are systematically formulated. With this transfer function formulation, the static and dynamic response, natural frequencies and mode shapes, and buckling loads of general stiffened cylindrical shells under arbitrary external excitations and boundary conditions can be determined in exact and closed form. The proposed method is illustrated on a Donnell-Mushtari shell, and compared with finite element method and two other modeling techniques.

Frequencies and Mode Shapes for Axisymmetric Vibration of Shells

1967 ◽  
Vol 34 (1) ◽  
pp. 73-80 ◽  
Author(s):  
E. W. Ross ◽  
W. T. Matthews
Keyword(s):  
Theoretical Result ◽  
General Class ◽  
Natural Frequencies ◽  
Numerical Results ◽  
Mode Shapes ◽  
Axisymmetric Vibration ◽  
Elastic Shells ◽  
Natural Frequencies And Modes

This paper treats the axisymmetric vibration of thin elastic shells. Estimates of natural frequencies and modes are obtained for a general class of domes by applying the approximations obtained in a previous paper by one of the authors. Numerical results are obtained for ellipsoidal shells, and one new theoretical result is found.

Free Asymmetric Vibrations of Composite Full Circular Cylindrical Shells Stiffened by a Bonded Non-Central Shell Segment

2005 ◽  
Author(s):  
V. O¨zerciyes ◽  
U. Yuceoglu
Keyword(s):  
Natural Frequencies ◽  
Circular Cylindrical Shell ◽  
Cylindrical Shells ◽  
Adhesive Layer ◽  
Solution Procedure ◽  
Mode Shapes ◽  
Orthotropic Materials ◽  
First Order ◽  
Present Solution ◽  
Circular Cylindrical Shells

In this study, the “Free Asymmetric Vibrations of Composite Full Circular Cylindrical Shells Stiffened by A Bonded Non-Central Shell Segment” are analyzed and investigated in some detail. The “full” circular cylindrical “base” shell and the non-centrally bonded circular cylindrical shell “stiffener” are assumed to be made of dissimilar orthotropic materials. The “base” shell and the “stiffening” shell segment are adhesively bonded by an in-between, relatively very thin, yet linearly elastic adhesive layer. In the theoretical analysis, for both shell elements, a “First Order Shear Deformation Shell Theory (FSDST)” such as “Timoshenko-Mindlin -(and Reissner)” type is employed. The damping effects in the entire system are neglected. The sets of dynamic equations of both “base” shell and “stiffening” shell segment and the adhesive layer are combined together, manipulated and are, finally, reduced to a “Governing System of First Order Ordinary Differential Equations” in Forms of the “state vectors” of the problem. This result constitutes a so-called “Two-Point Boundary Value Problem” for the entire composite shell system, which facilitates the present solution procedure. The final system of equations is numerically integrated by means of the “Modified Transfer Matrix Method (MTMM) (with Chebyshev Polynomials)”. The typical mode shapes with their natural frequencies are presented for several sets of support conditions. The very significant effect of the “hard” and the “soft” adhesive layer on the mode shapes and the natural frequencies are demonstrated. Some important parametric studies (such as the “Joint Length Ratio”, etc.) are also presented.

scholarly journals Numerical analysis of free vibration of cross-ply thick laminated composite cylindrical shells by continuous element method

2013 ◽  
Vol 35 (1) ◽  
pp. 17-30 ◽  
Author(s):  
Ta Thi Hien ◽  
Tran Ich Thinh ◽  
Nguyen Manh Cuong
Keyword(s):  
Finite Element Method ◽  
Vibration Analysis ◽  
Natural Frequencies ◽  
Cylindrical Shells ◽  
Laminated Composite ◽  
Composite Cylindrical Shell ◽  
New Approach ◽  
Reduced Time ◽  
Element Method ◽  
Composite Cylindrical Shells

This paper presents the vibration analysis of thick laminated composite cylindrical shells by a new approach using the Continuous Element Method (CEM). Based on the analytical solutions for the differential equations of thick composite cylindrical shell taking into account shear deflection effects, the dynamic transfer matrix is built from which natural frequencies are easily calculated. A computer program is developed for performing numerical calculations and results from specific cases are presented. Numerical results of this work are compared with published analytical and Finite Element Method (FEM) results. Through different examples, advantages of CEM are confirmed: reduced size of model, higher precision, reduced time of computation and larger range of studied frequencies. 

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