Thin-walled Cylindrical Shells Research Articles

An experimental investigation on interactive behavior of thin walled cylindrical shells

AbstractCylindrical shells are widely used in many kinds of applications under different cases of load combination. Nevertheless, only a small number of researches have been executed on cylindrical shells under pure bending in combination with external pressure. The present experimental research studies the buckling behavior of long cylindrical steel shells under combined pure bending and peripheral pressure. This study shows that initial sectional deformation developed by preloading considerably affects the buckling capacity of such shells. Moreover, it was found that primary load appreciably expedites the initiation of the buckling by activating the possible geometrical imperfections once shells are exposed to secondary load.

Form of circumferential weld-induced imperfections for tapered-wall cylindrical shell structures

Initial geometric imperfections have a great effect on the buckling strength of thin-walled cylindrical shells under axial compression, and the circumferential weld-induced imperfection is usually the most deleterious imperfection form. Two axisymmetric imperfection forms proposed by Rotter and Teng have widely been employed in the buckling analysis of cylindrical shells. However, the applicability of the two forms for tapered-wall cylinders needs further study, since they are derived from the elastic bending theory for long thin-walled cylinders with a constant wall thickness. This paper presents a modified form of circumferential imperfection for tapered-wall cylinders. Finite element analyses are carried out by employing the trapezoidal strain field approach to model the welding process, and the obtained circumferential depression shapes are used to evaluate the availability of the modified imperfection form. It is shown that the modified imperfection form is reasonable for any wall thickness ratio bet...

Experiments on imperfect cylindrical shells under uniform external pressure

The load-carrying behavior of cylindrical thin-walled shell structures under load pressure is strongly dependent on the nature and magnitude of the imperfections invariably caused by various manufacturing/welding processes. Weld-induced geometric imperfections have been reported to have especially detrimental effects on the buckling resistance of shells under uniform external pressure. Buckling and post buckling capacity of the shells depend considerably on the cross-sectional form and depth of the geometric imperfections. It also relies on the H/R and R/t ratios (H=height, R=radius, and t=thickness of a cylindrical shell). In the present study, we manufactured and tested a series of specimens having 4t and 8t magnitudes of imperfections with different ratios of H/R and R/t. The results of testing under different codes are compared. This study shows considerable reduction in the buckling resistance of the shells.

Similarity Design Method of Test Model of Thin-walled Short Cylindrical Shell with Complex Annular Labyrinth

Similarity Design Method of Test Model of Thin-walled Short Cylindrical Shell with Complex Annular Labyrinth

On The Axial Crushing Behavior of a Thin-Walled Cylindrical Shell With a Hollow Foam Core

On The Axial Crushing Behavior of a Thin-Walled Cylindrical Shell With a Hollow Foam Core

Experimental and theoretical investigation of deformation and fracture of subcutaneous fat under compression

The subcutaneous fat is considered as a structural material undergoing large inelastic deformations and failure under uniform compression. In calculation, the fat is replaced with a set of cells operating in parallel and suffering failure independently of one another. An elementary cell is considered as a closed thin-wall cylindrical shell filled with an incompressible liquid. All cells in the model are of the same size, and their material is hyperelastic, whose stiffness grows in tension. By comparing experimental data with the mathematical shell model, three parameters are determined to describe the hyperelastic behavior of the cells in transverse compression. A mathematical model with seven constants is presented for describing the deformation of subcutaneous fat under compression. The results obtained are used in a model of human thorax subjected to a local pulse action corresponding to the loading of human body under the impact of a bullet on an armor vest.

The Application of Hasofer-Lind Method in Reliability Design of Thin-Walled Cylindrical Shell

Hasofer-Lind method was applied to reliability design of cylindrical shell with internal pressure. The respective reliability design thickness of different diameter ratio was obtained in the case and compared with the thickness by the second moment reliability design method. The results showed that the wall thickness of cylindrical shell with internal pressure is the thinnest by using Hasofer-Lind method. And it is closest to the wall thickness of the second moment method in which the performance function was defined as the difference in actual wall thickness and the wall thickness needed for cylindrical shell with internal pressure.

Lightweight Design for Thin-Walled Cylindrical Shell Based on Action Mechanism of Bamboo Node

Lightweight design is needed for many engineering structures, but conventional design methods cannot always meet requirements. Natural organisms have developed many types of structures with excellent properties and ingenious construction, and they can provide many new design ideas. In this paper, a thin-walled cylindrical shell, one of the most common structures, is designed to resist buckling based on the study of bionics. First, the structure and function of bamboo node are described, and a statistical analysis of internode length-to-diameter ratio in bamboo is performed to investigate structural characteristics of bamboo node. Then, through buckling analysis of three relevant experimental models, the action mechanism of bamboo node is investigated, and two rules for application of this structure in engineering are proposed. Finally, a bionic design method is introduced, and a lightweight design for a thin-walled cylindrical shell based on this method is presented. A comparison between the bionic shell and a conventional one shows that the weight was reduced by as much as 20.5%.

Analysis of free oscillations of thin-walled cylindrical shells containing a compressible liquid

Free oscillations of a thin-walled cylindrical cell containing a compressible liquid were investigated. At some values of the parameters of the system, its eigenfrequencies were determined, and the influence of the geomet- ric and physical parameters of the cylindrical shell-liquid system on the free oscillation of cylinder was in- vestigated. Introduction. Shells as elements of machines and constructions are widely used in aircraft industry, shipbuild- ing, and so on. Therefore, in recent years the problems associated with the dynamic behavior of thin-walled structures that are in contact with environment under operating conditions attract considerable interest of researchers. The frequencies and forms of free oscillations of spherical and cylindrical shells coming in contact with elas- tic and liquid media were investigated in (1, 2). Approximate simple formulas were obtained by asymptotic methods for calculating the frequency and determining the form of oscillations of the system considered; this limits the use of the results obtained, because in a number of cases the possibility of carrying out a qualitative analysis of investigated processes is eliminated. Statement of the Problem. In this work we consider free asymmetric oscillations of an infinite thin-walled cylindrical shell containing a compressible liquid. Since finding the eigenfrequencies of the cylindrical shell-liquid sys- tem is associated with the solution of transcendental equations, the frequency of oscillations of a shell without a liquid is expressed in terms of the frequency of oscillations of the system in an explicit form; this allows one to investigate the spectra of the system's frequencies both analytically and graphically. The equations of radials oscillations of cylindrical shells have the form (3) ∂ 2 u

Buckling in Eccentrically Discharged Silos and the Assumed Pressure Distribution

Eccentric discharge in slender metal silos is known to be one of the most critical load conditions, responsible for many silo buckling disasters in the past. The high failure rate may be significantly attributed to difficulties in devising a suitable wall pressure representation for this condition. Where the flow of stored solids is eccentric and has partial contact with the wall in a slender silo, the solid exerts much lower pressures than the adjacent stationary solid. This pressure drop leads to very high local axial compression and causes buckling failure. Experimentally measured pressures indicate that a significant rise in pressure may occur just outside the flow channel, but its form and magnitude are not yet well understood because very detailed and expensive instrumentation is needed to obtain data that can define it. This paper explores the nonlinear structural behavior and buckling of a slender metal silo with and without specific inclusion of an adjacent rise in pressure, to determine whether it is a necessary part of any design pressure representation. To assist this investigation, the mechanics of the nonlinear behavior of a cylindrical silo under this load condition is explored using the analogy of a propped cantilever slice beam. Advantage is taken of a particular load condition that leads, by chance, to buckling at the same load factor for both linear and geometrically nonlinear analyses. This special case permits the detrimental effect of wall flattening and the beneficial effect of the changing prebuckling stress pattern to be explored to give a deeper insight into the behavior. The slice-beam analogy may also be generalized to describe the nonlinear behavior of any thin-walled cylindrical shell under meridional strip-like loads acting on part of the circumference.

Cylindrical shell bending theory for orthotropic shells under general axisymmetric pressure distributions

The axisymmetric linear bending theory of shells is treated for thin-walled orthotropic cylindrical shells under any smooth axial distribution of normal and shear pressures. The equations are developed, solved and explored in this paper. The derivation is presented in terms of a generalised Hooke’s Law with coupling between the axial membrane stress resultant and axial bending moment. This formulation permits the shell to be alternatively treated as a composite isotropic cylinder with axial stiffeners, rendering it useful for many practical problems. A linear kinematic relationship is assumed between the generalised strains and displacements. Expressions for the linear axial bending half-wavelength are presented for special cases of the stiffness matrix.The equations developed here are simple enough to be applied to the analysis of anisotropic thin-walled cylindrical shells using basic spreadsheet tools, removing the need to perform an onerous finite element analysis. Engineering applications potentially include corrugated metal, axially-stiffened or reinforced concrete silos under granular solid pressures, tanks under hydrostatic pressures, tubular piles under earth pressures, gas-filled cisterns and chimneys.

Adhesion of a Compliant Cylindrical Shell Onto a Rigid Substrate

The mechanical deformation of an ideal thin-walled cylindrical shell is investigated in the presence of intersurface interactions with a planar rigid substrate. A Dugdale–Barenblatt–Maugis (DBM) cohesive zone approximation is introduced to simulate the convoluted surface force potential. Without loss of generality, the repulsive component of the surface forces is approximated by a linear soft-repulsion, and the attractive component is described by two essential variables, namely, surface force range and magnitude, which are allowed to vary. The nonlinear problem is solved numerically to generate the pressure distribution within the contact, the deformed membrane profiles, and the adhesion-delamination mechanics, which are distinctly different from the classical solid cylinder adhesion models. The model has wide applications in cell adhesion and nanostructures.

Contributions to member stresses due to overall wind-induced behaviors of thin-walled cylindrical shell

The exterior walls of thin-walled cylindrical shells cannot be clearly identified as structural frames or cladding/components according to the current wind loading codes. Wind loading effects on such members depend not only on the overall wind-induced behavior of the cylinder, but also on imposed local wind pressures. In this paper, we identify the contributions of the largest wind loading effects on the overall behaviors of a structure. Fluctuating wind pressures measured from a 1:250 scaled cylinder model were investigated by the proper orthogonal decomposition (POD) method and used to generalize wind loads for analysis. The finite element model and an equivalent lumped-mass model corresponding to the prototype of the scaled model were built as analysis models. Expanded wind pressures were applied directly to the finite element model to calculate the wind loading effects, focusing on structural member stresses. Dynamic displacements obtained from the lumped-mass model were used to analyze the loading effects due to the overall behavior only. The contributions to the largest loading effects due to overall behaviors were identified and are presented in this paper.

Slender thin cylindrical shells under unsymmetrical strip loads

Modern procedures for the design of shell structures against buckling have their basis in analytical studies of axisymmetric shell geometries under the very simple load cases of uniform compression, external pressure and torsion. Studies of more complex but realistic stress states were based on prebuckling analyses using either membrane theory or linear bending theory because even these involved considerable mathematical complexity. As a result, only limited conclusions for practical design could be drawn and the effects of geometric nonlinearity could not be assessed. With recent advances in computing power and nonlinear finite element programs, it is now possible to undertake nonlinear analyses of complex load patterns that would have been very difficult to do only a decade or so ago.A number of practical load cases lead to a strip of pressure down one meridian, of which the best known ones are probably wind on tanks, eccentric discharge in silos, local thermal differentials, and partial fluid filling of a cylinder. This paper explores some of the rather unexpected stress patterns and modes of buckling that are predicted to develop in thin-walled cylindrical shells under such unsymmetrical strips of normal pressure. The results of a parametric study are presented to show the influence of the circumferential spread of the pressure strip on the structural behaviour. It is shown that the structural response to such loads may be very different, depending on whether the load acts inward or outward, and whether geometric nonlinearity and geometric imperfections are also included in the assessment.

Vibration and stability of ring-stiffened thin-walled cylindrical shells conveying fluid

Based on the Flügge shell theory, equations of motion of ring-stiffened thin-walled cylindrical shells conveying fluid are developed with the aid of the Hamilton's principle. Analysis is carried out on the vibration and stability of the ring-stiffened shells conveying fluid, and the effects of fluid velocity, the Young modulus, the size, and the number of the ring stiffeners on the natural frequency and the instability characteristics are examined. It is found that stiffeners can reduce the number of circumferential waves for the fundamental mode, and increase the shell's natural frequency, and thus the critical fluid velocity. For the number of longitudinal half waves being equal to one, the natural frequency and the corresponding critical fluid velocity are the largest for the internal-ring stiffened shell and are the smallest for the symmetrical-ring stiffened shell. The natural frequencies and the corresponding critical fluid velocity predicted by the established model increase with the increase in the Young modulus, the size, or the number of the stiffeners.

Effect of Volumetric Fiber Fraction on Failure Strength of Thin-Walled GFRP Composite Cylindrical Shell Externally Pressurized

Externally pressurized thin-walled GFRP composite cylindrical shell strength was studied against failure. Fiber breakage, matrix breakage, interlaminate shear deformation, delamination shear deformation and micro buckling failure were investigated employing maximum failure criteria as volumetric fiber fraction factor varied. One-ply cylindrical shell with fiber angle orientation of 0 degree was modeled in ABAQUS finite element simulation and the result was varied using analytical approaches. Moreover, the pressure fluctuations for various volumetric fiber fraction factors were quadratic according to plotted graphs obtained. Meanwhile, MATLAB software was used for theoretical analysis. The comparison of two approaches was proved to be accurate. Subsequently, failure strength of various laminated GFRP cylindrical shell with different fiber angle orientations at each ply was studied for diverse volumetric fiber fraction factors. Stacking sequence, fiber angle orientations were mainly effective on failure strength.

Numerical buckling analysis of thin cylindrical shells with combined distributed and local geometrical imperfections under uniform axial compression

In this paper, individual and combined effects of distributed and local geometrical imperfections on the limit load of an isotropic, thin-walled cylindrical shell under axial compression are investigated. First eigen affine mode shape imperfection pattern (FEAMSIP) is taken as distributed geometrical imperfections and dent as local geometrical imperfections. Limit load of the cylindrical shells are determined using non-linear static finite-element analysis module of general purpose FE software ANSYS. A parametric study on the effect of both imperfection patterns is done by varying the size and orientation of the dent. From the numerical results obtained, it is found that distributed geometrical imperfections namely, FEAMSIP have more influence on buckling strength than local geometrical imperfections namely dent.

EFFECTS OF CFRP REINFORCEMENTS ON THE BUCKLING BEHAVIOR OF THIN-WALLED STEEL CYLINDERS UNDER COMPRESSION

This paper presents a novel way of strengthening thin-walled steel cylindrical shells against buckling during axial compression in which a small amount of fiber-reinforced polymer (FRP) composite, coated from both sides can increase the buckling strength effectively. The effects of the reinforcement and the angle of fiber orientation as well as initial geometric imperfections on the buckling load-carrying capacity have been made clear through the three kinds of analytical procedures; the conventional linear eigen value buckling analysis, the reduced stiffness (RS) buckling analysis and the fully nonlinear numerical experiments. These multiple treatments suggest obtaining valuable information for the design of FRP-based hybrid structural elements and discusses influence of FRP to increase the load-carrying capacity of the thin-walled metallic structures having complex buckling collapse behavior. This paper also discusses how the angle of fiber orientation affects on the buckling strength and the associated buckling modes of the thin-walled shells.

Failure Strength of Thin-walled Cylindrical GFRP Composite Shell against Static Internal and External Pressure for various Volumetric Fiber Fraction

A study on a Circular cylindrical thin-walled shell failure made of GRP composite subjected to static internal and external pressure was carried out. The results were acquired using analytical and FEM simulation approaches for various volumetric fiber fractions. Fiber breakage, matrix breakage, interlaminate shear deformation, delamination shear deformation and micro buckling failure were investigated employing maximum failure criteria against internal and external pressure. One-ply cylindrical shell with fiber angle orientation of 0 degree was modeled in ABAQUS finite element simulation and the result was varied using analytical approaches. Moreover, the pressure fluctuations for various volumetric fiber fraction were quadratic according to plotted graphs. Meanwhile, MATLAB software was used for theoretical analysis. The comparison of two approaches was proved to be accurate. Subsequently, failure strength of various laminated GFRP cylindrical shell with different fiber angle orientations at each ply was studied for diverse volumetric fiber fraction factors. Stacking sequence, fiber angle orientations were mainly effective on failure strength.

Determination of stress–strain characteristics of thin polymer films on cylindrical specimens

An experimental method (TWCS method) was applied to determine the flexural elastic modulus E and some other stress-deformation characteristics of a thin-walled circular cylindrical polymer shell at compression. A methodology of test sample preparation and fixation as well as means of the measurement of the load P and the respective displacement ∆ were developed. Two modes of testing the equipment were used in which the sequences of measuring P ∆ → and P ∆ → were implemented. Repeatability of measurements was evaluated. Optimal geometric parameters of test samples and the range of determinable values of modulus E were defined. A procedure of the calculation of the relationship between the tensile stress σ and relative elastic tensile deformation e in the most deformed area of the sample was developed. Applicability of the TWCS method for multiple assessments of changes of deformational characteristics by using a single sample was proved. It was shown that creep, creep recovery, and stress relaxation tests can be performed by the TWCS method.