Deformation of spherical shells under a wind load

Strength of Materials -     

The buckling of cross-ply laminated non-homogeneous orthotropic composite conical thin shells under a dynamic external pressure

Summary.  The subject of this investigation is to study the buckling of cross-ply laminated orthotropic truncated circular conical thin shells with variable Young's moduli and densities in the thickness direction, subjected to a uniform external pressure which is a power function of time. After obtaining the dynamic stability and compatibility equations we reduce both of them to a time dependent ordinary differential equation with variable coefficient by using Galerkin's method. The critical dynamic and static loading, the corresponding wave numbers, the dynamic factors, critical time and critical impulse are found analytically by applying the Ritz type variational method. The dynamic behavior of cross-ply laminated truncated conical shells is investigated with: (a) lamina that present variations in the Young's moduli and densities, (b) different numbers and ordering of layers, (c) variable semi-vertex angles, and (d) external pressures which vary with different powers of time. It is concluded that all these factors contribute to appreciable effects on the critical parameters of the problem in question. Received June 13, 2002; revised December 10, 2002 Published online: May 8, 2003 This research project was initiated with the support of DAAD when Dr. Sofiyev was in Germany for a research project. The project was successfully accomplished with generous support of TUBITAK (The Scientific and Technical Research Council of Turkey).     

Stability of spirally stiffened shells under external pressure

Based on the use of a semizero-moment theory of thin shells, simple computational formulas for determination of the critical pressure on the shell have been obtained; these formulas contain all the necessary mechanical and geometric characteristics of the shell and the structure which are, in essence, a generalization of the well-known and widely used formulas for homogeneous isotropic shells. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 1, pp. 196–198, January–February, 2006.     

Variational analysis of delamination growth for composite laminated cylindrical shells under circumferential concentrated load

The growth of delamination in cylindrical shells under external pressure may lead to structural failure. Based on the variational principle of moving boundary (Qian WC. Variational calculus and finite element. Beijing: Science Press; 1980 [in Chinese].) and considering the contact effect between delamination regions, in this paper, the nonlinear governing equations for the delaminated cylindrical shells are derived, and the corresponding boundary and matching conditions are given. Moreover, according to the Griffith criterion, the formulas of energy release rate along the delamination front are obtained. As the numerical example, the delamination growth of axisymmetrical laminated cylindrical shells is analyzed, and the effects of delamination sizes and depths, geometrical parameters, material properties and laminate stacking sequences on delamination growth are discussed.     

Buckling optimization of hybrid-fiber multilayer-sandwich cylindrical shells under external lateral pressure

This paper describes a method of analyzing the maximum buckling strength of hybrid-fiber multilayer-sandwich cylindrical shells under external lateral pressure with respect to fiber orientations and weighting factors. Formulae for optimizing these parameters are presented and conditions for the application of these formulae are discussed. A discriminant is derived for assessing whether the hybrid sandwich cylindrical shells for given different unidirectional composites should reach the extreme value of critical pressure.     

The nonlinear stability of axisymmetric functionally graded material annular spherical shells under thermo-mechanical load

The authors of this article investigate the nonlinear stability of axisymmetric functionally graded annular spherical shells with temperature-dependent material properties subjected to thermo-mechanical loads and resting on elastic foundations. Equilibrium and compatibility equations are derived by using the classical thin shell theory in terms of the shell deflection and the stress function. Approximate analytical solutions are assumed to satisfy simply supported boundary conditions and Galerkin method is applied to obtain the closed-form of load–deflection paths. An analysis is carried out to show the effects of material and geometrical properties and combination of loads on the stability of the shells.     

Instability of moderately thick, laminated, cylindrical shells under combined axial compression and pressure

This paper presents theoretical predictions on the buckling of cylindrical shells subjected to simultaneous loading of axial compression and lateral pressure. The theoretical analysis took into account the effects of transverse shear deformation. The equilibrium equations and the related boundary conditions were derived by variational methods. The buckling equations were derived through the perturbation technique. A solution procedure is developed for computer-generated numerical results. This procedure is based on the Galerkin method. Solutions are obtained and results used to examine the effects of shear deformations for several stacking sequences, length-to-radius ratios, and radius-to-thickness ratios. The numerical results are presented both in tabular and in graphical forms.     

Experimental investigation of cylindrical shells with an opening under an external pressure pulse

The results of experimental investigation of the deformation of a shell with a circular opening under a pulse of uniform external pressure are presented. A multifactor regression equation is derived on the basis of experimental data. The resultant equation is analyzed statistically. Relationships suitable for the practical computation of the residual deflection and critical pulse are given.Translated from Problemy Prochnosti, No. 2, pp. 68–71, February, 1990.