• 소음진동
• /
• 제9권2호
• /
• pp.273-284
• /
• 1999

The cylindrical shells are used as primary components of complex structures such as airplane fuselages and nuclear pressure vessels. Recently the free vibration analysis of these structures are investigated by many researchers. The engineering informations on experimental validation of the free vibration behavior on the simply supported cylindrical shells are very few. The experimental methods for realizing the physical boundary condition of simply supported edges are examined. Natural frequencies and mode shapes of the isotropic and plain weave composite simply supported shells are obtained by modal tests. A theoretical and finite element analysis are also performed in order to validate the experimental results. The experimental results indicate that the simply supported boundary conditions with bolts along the circumferential direction of shell in both ends are well achieved. Those are shown to agree with the analytical results and with the finite element analysis results. These methods can be used to realize other experimental simple support boundary conditions.

• 한국소음진동공학회논문집
• /
• 제18권9호
• /
• pp.930-936
• /
• 2008

Fluid loading of a vibrating cylindrical shell has influence on natural frequencies and vibration magnitudes of the shell and the acoustic pressure of fluid. The vibroacoustics of fluid-filled cylindrical shells need the coupled solution of Helmholtz equation and governing equation of a cylindrical shell with boundary conditions. This paper proposed the wall impedance of fluid-filled axisymmetric cylindrical shells, focusing on the inner fluid/shell interaction. To propose the impedance, shell displacements used the linear combination of in vacuo shell modes. Acoustic pressure prediction of fluid used Kirchhoff-Helmholtz integral equation with Green's function of the plane mode. For the demonstration of the proposed results, numerical applications on mufflers were conducted.

• 한국정밀공학회지
• /
• 제16권6호
• /
• pp.108-113
• /
• 1999

For cylindrical shells, the closed-form solutions are confined to the specific boundary and/or loading conditions. Though the finite element method is certainly a powerful solution approach for the structural dynamics problems, it has been well known to provide the solution reliable only in the low frequency region due to the inherent high sensitivities of structual and numerical modeling errors. Instead, the spectral element method has been proved to provide accurate dynamic characteristics of a structure even at the ultrasonic frequency region. Since the wave characteristic of a cylindrical shell becomes identical to that fo a flat plate as the frequency increases, an equivalent plate model (EPM) representing the high-frequency dynamic characteristics of the cylindrical shell is introduced herein. The EPM-based spectral element analysis solutions are compared with the known analytical solutions for the cylindrical shells to confirm the validity of the present modeling approach.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1996년도 추계학술대회 논문집
• /
• pp.943-948
• /
• 1996

In this paper. we will discuss in making large size cylindrical shells with multithickness wall sections such as straight, stepped, tapered sides. These shells are constructed of type 6061 O temper aluminum starting with a blanking size of 877 mm plate. Its diameter to length ratio of 1 to 2.78 and a 36.7％ wall reduction is achieved by our continuous deep drawing process. This process required no in-process annealing. But after cold working, these shells is performed heat treatment to T6 condition. These shells are used for the making of seamless LPG pressure vessels after the spinning process. This process is composed of deep drawing, reverse redrawing, drawing-ironing and several ironing processes. In the verification of forming process design, we used DEFORM code.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2004년도 추계학술대회논문집
• /
• pp.928-933
• /
• 2004

The vibration characteristic is a primary design factor. The cylindrical shells are used as a primary components of complex structure. also, The cylindrical shells have oblique angle. In this study, The vibrational characteristics of steel and plain wave GFRP cylindrical shell with an oblique end are given by experimental and finite element method. To be find characteristic of the oblique end, the mass of the cylindrical shell is maintained. Natural frequency and mode shapes of isotropic and plain weave composite shells are obtained by modal test. The results are compared with those of the finite element method. The simply supported boundary conditions with bolts along the circumferential direction of the GFRP shell are well achieved. Also, The clamped boundary conditions is applied to the steel specimen. Those are shown to agree well with the analytical results and finite element analysis results.

• The Journal of the Acoustical Society of Korea
• /
• 제21권4E호
• /
• pp.183-188
• /
• 2002

In this paper, the strong in-plane vibration has been experimentally observed at the end of a finite cylindrical shell. The strong in-plane vibration was generated by the evanescent wave field, which was excited along about half the length of the shell. The evanescent waves were generated due to mode conversion of elastic waves at the ends of the cylindrical shells. The results show that the strong in-plane end vibration can be generated in cylindrical shells.

• Steel and Composite Structures
• /
• 제27권1호
• /
• pp.35-48
• /
• 2018

In this paper, the response of a sandwich cylindrical shell over any sort of boundary conditions and under a general distributed static loading is investigated. The faces and the core are made of some isotropic materials. The faces are modeled as thin cylindrical shells obeying the Kirchhoff-Love assumptions. For the core material it is assumed to be thick and the in-plane stresses are negligible. The governing equations are derived using the principle of the stationary potential energy. Using harmonic differential quadrature method (HDQM) the equations are solved for deformation components. The obtained results primarily are compared against finite element results. Then, the effects of changing different parameters on the stress and displacement components of sandwich cylindrical shells are investigated.

• Geomechanics and Engineering
• /
• 제36권2호
• /
• pp.99-109
• /
• 2024

Studying the dynamic behavior of axially moving cylindrical shells in hygro-thermal environments has important theoretical and engineering value for aircraft design. Therefore, in this paper, considering hygro-thermal effect, the nonlinear forced vibration of an axially moving cylindrical shell made of functionally graded materials (FGM) is studied. It is assumed that the material properties vary continuously along the thickness and contain pores. The Donnell thin shell theory is used to derive the motion equations of FGM cylindrical shells with hygro-thermal loads. Under the four sides clamped (CCCC) boundary conditions, the Gallekin method and multi-scale method are used for nonlinear analysis. The effects of power law index, porosity coefficient, temperature rise, moisture concentration, axial velocity, prestress, damping and external excitation amplitude on nonlinear forced vibration are explored through parametric research. It can be found that, the changes in temperature and humidity have a significant effect. Increasing in temperature and humidity will cause the resonance position to shift to the left and increase the resonance amplitude.

• Structural Engineering and Mechanics
• /
• 제66권3호
• /
• pp.295-303
• /
• 2018

The semi-analytical method to study the nonlinear dynamic behavior of simply supported spiral stiffened functionally graded (FG) cylindrical shells subjected to an axial compression is presented. The FG shell is surrounded by damping and linear/nonlinear elastic foundation. The proposed linear model is based on the two-parameter elastic foundation (Winkler and Pasternak). A three-parameter elastic foundation with hardening/softening cubic nonlinearity is used for nonlinear model. The material properties of the shell and stiffeners are assumed to be FG. Based on the classical plate theory of shells and von $K{\acute{a}}rm{\acute{a}}n$ nonlinear equations, smeared stiffeners technique and Galerkin method, this paper solves the nonlinear vibration problem. The fourth order Runge-Kutta method is used to find the nonlinear dynamic responses. Results are given to consider effects of spiral stiffeners with various angles, elastic foundation and damping coefficients on the nonlinear dynamic response of spiral stiffened simply supported FG cylindrical shells.

• Structural Engineering and Mechanics
• /
• 제28권6호
• /
• pp.749-765
• /
• 2008

Free axisymmetric vibrations of layered cylindrical shells of variable thickness are studied using spline function approximation techniques. Three different types of thickness variations are considered namely linear, exponential and sinusoidal. The equations of axisymmetric motion of layered cylindrical shells, on the longitudinal and transverse displacement components are obtained using Love's first approximation theory. A system of coupled differential equations on displacement functions are obtained by assuming the displacements in a separable form. Then the displacements are approximated using Bickley-spline approximation. The vibrations of two-layered cylindrical shells, made up of several types of layered materials and different boundary conditions are considered. Parametric studies have been made on the variation of frequency parameter with respect to the relative layer thickness, length ratio and type of thickness variation parameter.