Influence of localized imperfections on the buckling of cylindrical shells under axial compression (original) (raw)
Imperfection sensitivity of cylindrical shells under axial compression
ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik, 2000
In the framework of the cellular bifurcation theory, we investigate the effect of distributed and/or localized imperfections on the buckling of long cylindrical shells under axial compression. Using a double scale perturbative approach including modes interaction, we establish that the evolution of amplitudes of instability patterns is governed by a nonhomogeneous second order system of three non-linear complex equations. The localized imperfections are included by employing jump conditions for their amplitude and permitting discontinuous derivatives. By solving these amplitude equations, we show the influence of distributed and/or localized imperfections on the reduction of the critical load. To assess the validity of the present method, our results are compared to those given by two finite element codes.
Buckling of thin-walled cylindrical shells under axial compression
International Journal for Numerical Methods in Engineering, 2009
Lightweight thin-walled cylindrical shells subjected to external loads are prone to buckling rather than strength failure. The buckling of an axially compressed shell is studied using analytical, numerical and semi-empirical models. An analytical model is developed using the classical shell small deflection theory. A semi-empirical model is obtained by employing experimental correction factors based on the available test data in the theoretical model. Numerical model is built using ANSYS finite element analysis code for the same shell. The comparison reveals that the analytical and numerical linear model results match closely with each other but are higher than the empirical values. To investigate this discrepancy, non-linear buckling analyses with large deflection effect and geometric imperfections are carried out. These analyses show that the effects of non-linearity and geometric imperfections are responsible for the mismatch between theoretical and experimental results. The effect of shell thickness, radius and length variation on buckling load and buckling mode has also been studied. Copyright © 2009 John Wiley & Sons, Ltd.
Nonlinear Engineering, 2013
Imperfection sensitivity of cylindrical shells subjected to axial compressive load is investigated by means of non-linear buckling analysis and post-buckling analysis. Non-linear buckling analysis involves the determination of the equilibrium path (or load-deflection curve) upto the limit point load by using the Newton-Raphson approach, whereas post-buckling analysis involves the determination of the equilibrium path beyond the limit point load and up to the collapse load by using the arc-length approach. Limit point loads evaluated from these two approaches for various imperfection magnitudes show an excellent agreement which clearly confirms the numerical results obtained.
Thin-Walled Structures, 1991
Buckling and postbuckling behaviour of perfect and imperfect cylindrical shells of finite length subject to combined loading of external pressure and axial compression are considered. Based on the boundary layer theory which includes the edge effect in the buckling of shells, a theoretical analysis for the buckling and postbuckling of circular cylindrical shells under combined loading is presented using a singular perturbation technique. Some interaction curves for perfect and imperfect cylindrical shells are given. The analytical results obtained are compared with some experimental data in detail, and it is shown that both agree well. The effects of initial imperfection on the interactive buckrng load and postbuckling behaviour of cylindrical shells have also been discussed NOTATION
Imperfection sensitivity of cylindrical shells under axial compresssion
In the framework of the cellular bifurcation theory, we investigate the effect of distributed and/or localized imperfections on the buckling of long cylindrical shells under axial compression. Using a double scale perturbative approach including modes interaction, we establish that the evolution of amplitudes of instability patterns is governed by a nonhomogeneous second order system of three non-linear complex equations. The localized imperfections are included by employing jump conditions for their amplitude and permitting discontinuous derivatives. By solving these amplitude equations, we show the influence of distributed and/or localized imperfections on the reduction of the critical load. To assess the validity of the present method, our results are compared to those given by two finite element codes.
International Journal of Non-Linear Mechanics, 2002
The present experimental study aims at providing better inputs for improvement of the buckling load predictions of sti ened cylindrical shells subjected to combined loading. The work focuses on two main factors which considerably a ect the combined buckling load of sti ened shells, namely geometric imperfections and boundary conditions. Six shells with nominal simple supports were tested under various combinations of axial compression and external pressure. The vibration correlation technique is employed to deÿne the real boundary conditions. The geometric imperfections of the integrally sti ened shells are measured in the present experiments in situ and are used as inputs to a multimode analysis which yields the corresponding "knockdown" factor for various combinations of loading. Thus, when employing the repeated buckling procedure for obtaining interaction curves, each point on the curve is adjusted (using the multimode analysis) for the measured "new" surface of the shell and this results in more realistic interaction curves. The geometrical imperfections of the preloaded shells can also serve as an input to the International Imperfection Data Bank for future studies on the correlation between the manufacturing method of the shell and their geometric imperfections. ?
Buckling strength of thin cylindrical shells under localised axial compression
2002
The buckling strength of a thin cylindrical shell is important in many applications in civil engineering. On the one hand, current design rules are principally based on an empirical interpretation of test data and hence very simple loading conditions are applied. On the other hand, experimental and theoretical observations show significant stress non-uniformity and hence a deviation from the buckling strength expected under uniform load. Reliable quantification of this effect is still challengingly difficult. This paper explores a typical thin cylindrical silo shell under localized axial compression. Two different buckling phenomena are identified with corresponding, and distinct, buckling mode forms. The influence of geometric imperfections on the buckling strength of the shell is also considered.
Buckling under axial compression of long cylindrical shells with random axisymmetric imperfections
Quarterly of Applied Mathematics, 1969
The buckling of long cylinders with homogeneous random axisymmetric geometric imperfections under uniform axial compression is studied by means of a modified truncated hierarchy technique. It is found that the buckling load of the cylinder depends only on the spectral density of the random imperfections. In particular, for small values of the standard deviation of the axisymmetric imperfection the buckling load depends only on the value of the spectral density at a specific wave number.
Nuclear Engineering and Design, 2009
The load carrying behaviour of cylindrical thin-walled shell structures under pressure load is strongly dependent on the nature and magnitude of the imperfections invariably caused by various manufacturing processes. The present paper examines instabilities of long homogeneous and isotropic thin elastic tubes, characterized by geometric imperfections like eccentricity or ovality, on the buckling behaviour in conditions for which, at present, a complete theoretical analysis was not found in literature. Moreover, the additional aspect of the influence of the welded joint geometry and position is investigated over a wide range of diameter to thickness ratio, extending the findings of previous works. The problem of buckling for variable load conditions is relevant in the context of NPP applications as, for instance the optimisation of an integrated and innovative LWR Steam Generator (SG) tubes, according to the updated ASME rules.