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In this study, we use transport equations to investigate the dynamic buckling of an imperfect elastoplastic beam, including the effect of axial stress waves, when subjected to an impulsive load. Thus, the governing equations for the elastoplastic behavior of the material are extracted using mass, energy, and momentum transport equations. We assume that the passage of the shock wave through the control volume creates five phases with four boundary discontinuities, i.e., the initial elastic phase, initial plastic phase, fluid phase, secondary plastic phase, and secondary elastic phase. Transport equations are used in integral form as well as non-physical variables to eliminate the discontinuity conditions in the governing equations. These equations are also used for continuum modeling of the elastoplastic behavior of the beam under an impulsive load and a continuous model is presented. Finally, the time histories of stress, strain, and velocity wave propagation along the beam are presented, and the results are validated based on comparisons with known solutions. [ABSTRACT FROM AUTHOR]

The present study was aimed to investigate the influence of forcing frequency on nonlinear dynamic pulse buckling of imperfect rectangular plates with six different boundary conditions. The Galerkin's approximate method on the basis of polynomial and trigonometric mode shape functions is used to reduce the governing nonlinear partial differential equations to ordinary nonlinear differential equations. Moreover a numerical study of these governing equations is accomplished by Runge Kutta integration methods. The convergence of the polynomial and trigonometric mod shape functions are investigated to compute the dynamic response of plate. The effects of frequency of impulse loading and boundary conditions on the deflection histories of plate are studied. The dynamic response of plate subjected to impulsive loading with different forcing frequency is compared to results obtained by exponential impulsive loading. The results show that, by increasing the forcing frequency of impulsive loading, the maximum displacement of plate increases and converge with lower values to response of plate subjected to exponential impulse. Moreover, different boundary conditions and various pulse functions have significant influence on the dynamic response of the plate. [ABSTRACT FROM AUTHOR]

In this article, the nonlinear buckling behavior of imperfect cylinders made of isotropic, composite and functionally graded materials is studied. A continuum-based semi-analytical finite element formulation is introduced to study the nonlinear behavior of cylinders under thermal loads. A method is proposed to implement the initial geometric imperfection of the cylinder by transformation of structure due to deformation gradients. The influences of geometrical parameters, different materials and imperfection factors are investigated on pre- and post-buckling paths. A comparison is made between the classical von Kármán-based and continuum-based approaches to ensure the validation of the results and to study the applicability of the von-Kármán approximation. [ABSTRACT FROM AUTHOR]

In this paper, the nonlinear dynamic pulse buckling of imperfect rectangular plate subjected to sinusoidal, exponential, damping and rectangular pulse functions with six different boundary conditions is investigated. In order to solve the large deformation equations of plate, Galerkin method together with trigonometric mode shape functions is applied. Also, the nonlinear coupled time integration of the governing equation of plate is a solved employing fourth-order Runge–Kutta method. The effects of boundary conditions, pulse functions, initial imperfection, force pulse amplitude and geometrical parameters of the shock spectrum of a plate and deflection histories of plate for impulsive, dynamic and quasi-periodic force loads are studied. In this study, the effects of boundary conditions, pulse functions, initial imperfection, force pulse amplitude and geometric parameter in nonlinear dynamic response are investigated. According to the results for impulsive loading, the displacement response reaches its peak after shock duration and in the dynamic and quasi-static pulse loading, the maximum response of plate occurs during and before shock duration. Moreover, with increasing the loading amplitude, length of the plate and initial imperfection, the maximum displacement of plate increases. Different boundary conditions and various pulse functions have significant influence on the dynamic response of the plate. By increasing the restriction in supports, the resistance ability against deformation and stability of plate increases. [ABSTRACT FROM AUTHOR]

In this paper, the pre- and post-buckling behavior of beams made of Functionally Graded Materials (FGMs), a mixture of ceramic and metal, under separate mechanical and thermal loading, is studied. To this end, the finite element formulation is established, based on the Euler-Bernoulli beam theory. The effects of geometrical nonlinearity and imperfection are taken into account. The arc-length algorithm is employed to obtain the secondary path beyond the bifurcation point. The influences of material index, imperfection, geometrical parameters and different boundary conditions of simplysupported, clamped-simply and clamped-clamped, on the post-buckling characteristics of FGM beams, are thoroughly investigated. The results generated are compared with the existing data in the literature and good agreements are achieved. The investigation undertaken here proves the necessity of performing post-buckling analysis on FGM beams, especially with simply-supported end conditions. [ABSTRACT FROM AUTHOR]

This article introduces a new semi-analytical nonlinear finite element formulation for thin cylinders according to a continuum-based approach. A comparison between the continuum-based approach and the classical approach for the buckling behavior of isotropic and orthotropic perfect cylinders validates the results. The classical approach is defined according to thin shell theories based on the von Karman approximation. A mathematical modeling for geometry imperfection of cylinders is derived according to a continuum-based approach whose results are compared with the results of the classical approach for imperfect cylinders. The influence of neglecting some nonlinear terms in the classical approach for perfect and imperfect cylinders on the buckling path is investigated. In the buckling analysis, two methods, i.e. the perturbation and load disturbance methods, which undertake to switch to the post-buckling path, are compared to each other. [ABSTRACT FROM PUBLISHER]

In this paper the meshless local Petrov-Galerkin (MLPG) method is implemented to study the buckling of isotropic cylindrical shells under axial load. Displacement field equations, based on Donnell and first order shear deformation theory, are taken into consideration. The set of governing equations of motion are numerically solved by the MLPG method in which according to a semi-inverse method, a new variational trial-functional is constructed to derive the stiffness matrices and critical buckling loads are obtained in various boundary conditions. The moving least squares interpolation is employed to construct both trial and test functions. The present method is a truly meshless method based on a number of randomly located nodes upon which no global background integration mesh is needed and no element matrix assembly is required. In the present MLPG formulation, a local variational form is constructed over a local sub-domain instead of using the conventional weighted-residual procedure. The influences of some commonly used boundary conditions and effects of shell geometrical parameters are studied. The results show the convergence characteristics and accuracy of the mentioned method. [ABSTRACT FROM AUTHOR]

In this article, the thermal post-buckling of shells of revolution under the action of uniform thermal load is investigated. To discretize the problem, the semi-analytical finite element method has been employed. The nonlinear equations are then solved by means of the Newton-Raphson algorithm in conjunction with the Arc length method. The effect of initial imperfection is also considered. The results obtained from the present analysis are compared to the published results in the literature to show the accuracy and robustness of the present method in predicting the nonlinear thermal buckling of shells of revolution. [ABSTRACT FROM AUTHOR]

In this paper, the thermal buckling of piezoelectric composite shells of revolution under uniform and linear thermal distributions and selected boundary conditions is investigated by using the semi-analytical finite element. The effects of different parameters such as the type of temperature distributions through the thickness, fiber angles, arrangements of piezoelectric patches and amount of displacement feedback control gain are examined. The results obtained from the present analysis are validated, where possible, with those available in the literature. [ABSTRACT FROM AUTHOR]

In this paper, the thermal buckling of composite shells with selected boundary conditions under uniform and linearly distributed thermal load is investigated. The theoretical modeling procedure is based on semi-analytical finite element method. The effects of important structural parameters such as amount of cut-out at apex, fiber angles as well as temperature distributions are taken into consideration. The obtained results from the present analysis are compared with some available published results to show the accuracy and robustness of the present method. [ABSTRACT FROM AUTHOR]

Due to the importance of buckling analysis of composite structures in various industrial applications a comparative study of buckling behavior of composite plates is presented here. Mathematical modelling developed in the present work for generally laminated plates is based on generalized differential quadrature rule (GDQR) and R–R method. To show the ability and robustness of the mathematical modeling in handling buckling analysis, results obtained using GDQR and R–R are compared with each other and also with some available results based on experimental and analytical works. The efficiency and reliability of the GDQR in comparison with R–R method on the buckling behavior is also discussed. [Copyright &y& Elsevier]

In this paper, the dynamic buckling of axisymmetric circular cylindrical shells subjected to axial impact is investigated theoretically and experimentally. The von Mises yield criterion is used for the elastic–plastic cylindrical shell made of linear strain hardening material in order to derive the constitutive relations between stress and strain increments. Nonlinear dynamic circular cylindrical shell equations are solved with using finite difference method for two types of loading which are stationary cylindrical shells impacted axially and traveling cylindrical shells impacted against a rigid wall. Experimental tests for two types of loading are performed by gas gun. Theoretical and experimental results for cylindrical shells under axial impact for different loading conditions are reported and it is found that there is a good agreement between them. [ABSTRACT FROM AUTHOR]