Dynamic Response Of Cylindrical Shell Research Articles

Dynamic response of cylindrical shell supporting structure under multiple impacts: experimental and numerical investigation

Dynamic response of cylindrical shell supporting structure under multiple impacts: experimental and numerical investigation

Nonlinear vibration of full-filled fluid corrugated sandwich functionally graded cylindrical shells

This article proposes a semianalytical approach for the nonlinear free and forced asymmetric vibration of corrugated sandwich functionally graded cylindrical shells containing fluid under harmonic radial load. The corrugation is considered with two types: trapezoidal corrugation and round corrugation. By using the Donnell shell theory, taking into account the geometrical nonlinearity of von Kármán and an equivalent model for corrugated structures, the governing equations of shell are established. The nonlinear motion equations are reduced to nonlinear differential equation in terms of time by applying the Galerkin procedure. The numerical investigations for the nonlinear dynamic response of cylindrical shells are obtained by using the fourth-order Runge–Kutta method. Numerical results show the very large effects of corrugation and fluid on the natural frequency and nonlinear vibration behavior of shells.

The dynamic response of cylindrical shell and square plate with pre-formed holes under blast loading

The dynamic response of cylindrical shells and square plate with pre-formed holes under blast loading was studied by numerical simulation. The numerical model was calibrated by the experimental data of square plates with pre-formed holes. The dynamic responses and deformation of cylindrical shells with pre-formed holes subjected to blast loading was investigated by the same numerical model. The structure response process has been divided into four specific stages which has been discussed systematically. According to the comparison of structure response process, stress concentration between these two structures under blast loading, it is concluded that the square plates have a better performance than that of cylindrical shell with or without pre-formed holes and the influence of pre-formed holes on blast-resisting of square plate is bigger than that of cylindrical shell. In addition, the global and local deformation characteristics are mainly result from the space configuration and pre-formed holes, respectively.

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

This study gives a numerical work on dynamic response of cylindrical shells submerged in an incompressible fluid subjected to earthquake, thermal and moisture loads. The cylindrical shell is reinforced by carbon nanotubes (CNTs) where the Mori-Tanaka model is used for calculating the effective material properties of the structure considering agglomeration effects. The effect of the fluid is assumed using the acoustic wave equation. The structural damping effect is considered using Kelvin-Voigt model. Sinusoidal shear deformation shell theory (SSDT) is utilized in the shell dynamical equations based on energy method and Hamilton’s principle. The problem is framed combining shell motion equations with the acoustic wave equation where the fluid-loaded terms are considered with Hankel function of second kind. Differential quadrature method (DQM) and Newmark approach are employed to solve the shell problem. The influences of fluid, boundary condition, thermal load, moisture changes, boundary condition, structural damping parameter, length to thickness ratio of shell, CNTs volume percent and agglomeration are shown on the dynamic deflection of the structure. The results show that increasing the CNTs volume percent, the dynamic deflection decreases while considering the CNTs agglomeration leads to increase in the dynamic deflection of the structure.

Study on Dynamic Response of Cylindrical Shells under Combined Load

In order to study the dynamic response of the cylindrical shell structure which is similar to the missile cabin under the combined effects of axial compressive load and radial aerodynamic load, the equilibrium equation of dynamic response of cylindrical shell is derived based on the Hamiltons principle. The displacement response of cylindrical shell is calculated through employing the numerical method. The calculation results show that the axial displacement response and the radial displacement response of cylindrical shell are much greater than the circumferential displacement response; the radial displacement will be maximum when the excitation frequencies are 285Hz, 594Hz, 1039Hz, 1062Hz, 1093Hz, 1962Hz and 1987Hz; the axial displacement will be maximum when the corresponding excitation frequencies are 81Hz and 294Hz; the peak values of displacement response in non-load plane are not all obtained at the resonance frequency and a certain effect is generated due to the modal coupling.

Max-min K-means clustering algorithm and application in response signal feature extraction

In order to overcome the problem of classical K-means clustering algorithm, such as sensitiveness to its initial cluster centers selection and easiness of falling into local optimization, this paper proposed max-min K-means clustering algorithm. The algorithm adopts max-min principle to determine initial cluster centers of K-means clustering algorithm. Comparison of clustering effects of the new method with that of muilt-restart K-means clustering algorithm on artificial data set showed the better effect and the greater excellence of max-min principle. Then, the max-min K-means clustering algorithm was applied to analyze vibration response signal of cylindrical shell automatic in order to discover space distribution feature of dynamics response. Clustering results tallied with feature of dynamic response of cylindrical shell, which validated the effectiveness and reasonableness of the new clustering method itself.

Free vibration analysis of homogeneous isotropic circular cylindrical shells based on a new three-dimensional refined higher-order theory

Closed-form formulation of three-dimensional (3-D) refined higher-order shear deformation theory (RHOST) for the free vibration analysis of simply supported–simply supported and clamped–clamped homogenous isotropic circular cylindrical shells is presented. The proposed RHOST accounts for the effects of in-plane and rotary inertias as well as the effects of transverse normal and shear strains on the dynamic response of cylindrical shells. Also, the present analysis incorporates trapezoidal shape factor of a shell element that arise due to the fact that the stresses over the thickness of the shell are to be integrated on a trapezoidal-like cross-section of a shell element to obtain the accurate stress-resultants. Therefore, the present theory refines other HOSTs established hitherto for free vibration analysis of thick circular cylindrical shells. The equations of motion are obtained using Hamilton's principle. Solutions are obtained using the Galerkin method. Numerical results, not hitherto reported in the literature, are presented for the natural frequencies of isotropic long/short and hollow/solid cylinders. Numerical results indicate that for thick cylinders with large length-to-radius ratios, approximate series truncation methods are inadequate for calculating the stress-resultants and just exact integration yields accurate stress-resultants leading to a reliable prediction of natural frequencies. Natural frequencies associated to higher-mode numbers of thick isotropic cylinders, never published in the literature before, are also considered in this paper. It is shown that stress-resultants calculated using exact integration over the cylinder cross-section are necessary to obtain accurate results of the free vibration analysis, especially for higher-mode numbers of thick isotropic cylinders. The closed-form solutions presented herein are compared with the available exact 3-D elasticity and analytical solutions in the available literature and excellent agreement is obtained. Also, the validity of the results is established with the aid of commercial finite element software.

High-frequency response of isotropic-laminated cylindrical shells modeled by a layer-wise theory

In this paper, the high-frequency response of isotropic-laminated cylindrical shells is investigated using a layer-wise theory. The cylindrical shell is discretized in an arbitrary number of layers in the radial direction, and a three-dimensional stress state is assumed in each layer. Approximate numerical results obtained by the layer-wise theory are compared with the exact wave-dispersion analytical results. The very good agreement between approximate and exact results indicates that the layer-wise theory can accurately describe of the dynamic response of cylindrical shells in the high-frequency (short-wavelength) range.

Impedance-Based Modeling of Actuators Bonded to Shell Structures

When discrete piezoelectric actuator patches bonded on structures are used for active shape, vibration, and acoustic control, the desired deformation field in the structure is obtained through the application of localized line forces and moments generated by expanding or contracting bonded piezoelectric actuators. An impedance-based model to predict the dynamic response of cylindrical shells subjected to excitation from surface-bonded induced strain actuators is presented. The essence of the impedance approach is to match the actuator impedance with the structural impedance at the ends of the actuators, which will retain the dynamic characteristics of the actuators. A detailed derivation of the actuator and structural impedance is included. It is found that the actuator's output dynamic force in the axial and tangential direction are not equal. Various case studies of a cylindrical thin shell are performed to illustrate the capabilities of the developed impedance model. Out-of-phase actuation is shown to be the most efficient in exciting the lower order bending modes of shell structures. The paper is concluded with a finite element analysis verification of the derived impedance model.

Dynamic response of cylindrical shells with discontinuity in thickness subjected to axisymmetric load

Abstract Cylindrical shells with discontinuity in the thickness and subjected to harmonic axisymmetric loads have been analyzed. The loadings considered are a uniform internal pressure and a circular ring load at the mid-section. A semi-analytical finite element method is used for the analysis. A thin shell finite element with four degrees of freedom per node is used. Three shell models are analyzed for possible reduction of maximum displacement and maximum stress by choosing the discontinuity at different locations. Numerical results are presented for clamped-clamped end conditions and for various step-ratios in the thickness, for the first three models. The weight of the shell is kept constant for the various step-ratios. It is shown that the maximum displacement and maximum stress decrease for certain types of thickness variations as presented in this paper.

A higher order theory for free vibration analysis of circular cylindrical shells

The free, undamped vibration of an isotropic circular cylindrical shell is analysed with higher order displacement model, giving rise to a more realistic parabolic variation of transverse shear strains. The method accounts for in-plane inertia, rotary inertia, and shear deformation effects on the dynamic response of cylindrical shells. The frequencies obtained from the present analysis, shear deformation theory, and Flügge theory are compared with the exact elasticity results. It is found that the frequencies predicted by the present analysis are closer to exact values than those predicted by the shear deformation theory, especially for cases with shorter wavelengths.

Dynamic Response of Cylindrical Shells to Concentrated Impact Load

The dynamic response of a cylindrical shell with finite length to a concentrated impact load on its arbitrary surface is studied. The response of radial displacement and stresses is made clear through the analysis which is carried out by using the theory considering not only radial but also in-plane inertia forces, and the effect of these inertia forces on the response of them is also examined. The relation between their maximum values and the ratio of length to radius of shell is shown, in addition to the dynamic load factor of the radial displacement.

Dynamic Response of Cylindrical Shells to Concentrated Impact Force

Dynamic Response of Cylindrical Shells to Concentrated Impact Force

Dynamic Response of Cylindrical Shells With Initial Stress and Subjected to General Three-Dimensional Surface Loads

This paper presents general solutions for both Flu¨gge’s and Donnell’s equations governing the displacements of the midsurface of a thin circular cylindrical shell, simply supported at both ends, of finite length, under initial twoway stress and subjected to general time-dependent surface loads. Analytical solutions are presented to the specific problems of a stationary radial point force and a stationary point couple. A numerical comparison of Donnell’s and Flu¨gge’s theories is made for these specific problems for a wide variety of shell parameters including initial stress. It is found for the case of a dynamic point force or point couple that Donnell’s theory is satisfactory for thin and very short shells (h/a ≤ 0.01 and l/a ≤ 2).