Influence of Initial Imperfection on Buckling Load of Membrane Aeroshell

2018 ◽  
Vol 17 (0) ◽  
pp. 271-276
Author(s):  
Kenichi OIZUMI ◽  
Kyoichi NAKASHINO ◽  
Kazuhiko YAMADA ◽  
Kazushige MATSUMARU
Keyword(s):  
Initial Imperfection ◽  
Buckling Load

Elastic Buckling Analysis of Rigidly Jointed Single Layer Reticulated Domes with Random Initial Imperfection

1992 ◽  
Vol 7 (4) ◽  
pp. 265-273 ◽  
Author(s):  
Toshiro Suzuki ◽  
Toshiyuki Ogawa ◽  
Kikuo Ikarashi
Keyword(s):  
Single Layer ◽  
Initial Imperfection ◽  
Random Variable ◽  
Buckling Analysis ◽  
Buckling Load ◽  
Mode Shapes ◽  
Elastic Buckling ◽  
Nonlinear Buckling ◽  
Reticulated Domes ◽  
Nonlinear Buckling Analysis

In the present paper, the effect of imperfection on the elastic buckling load and mode shapes of externally-loaded single layer reticulated domes is investigated. The types of buckling concerned here are the general buckling, the local (dimple) buckling and the buckling of a member. As to the geometric parameter of a dome, the slenderness factor S is adopted which represents the openness and slenderness of the dome. The maximum value of the imperfection is assumed to be the normal random variable. The buckling loads are computed by the linear and the nonlinear buckling analysis using the finite element method. The statistical values are calculated by the three-points estimates method. The main points of interest are the influence of the shape and the extent of an imperfection on the buckling load.

Comparisons of Probabilistic and Two Nonprobabilistic Methods for Uncertain Imperfection Sensitivity of a Column on a Nonlinear Mixed Quadratic-Cubic Foundation

2008 ◽  
Vol 76 (1) ◽  
Author(s):  
Xiaojun Wang ◽  
Isaac Elishakoff ◽  
Zhiping Qiu ◽  
Lihong Ma
Keyword(s):  
Elastic Foundation ◽  
Probabilistic Method ◽  
Initial Imperfection ◽  
Theoretical Models ◽  
Buckling Load ◽  
Dimensional Euclidean Space ◽  
Limited Information ◽  
Imperfection Sensitivity ◽  
Sensitive Structure ◽  
Range Of Variation

Two nonprobabilistic set-theoretical treatments of the initial imperfection sensitive structure—a finite column on a nonlinear mixed quadratic-cubic elastic foundation—are presented. The minimum buckling load is determined as a function of the parameters, which describe the range of possible initial imperfection profiles of the column. The two set-theoretical models are “interval analysis” and “convex modeling.” The first model represents the range of variation of the most significant N Fourier coefficients by a hypercuboid set. In the second model, the uncertainty in the initial imperfection profile is expressed by an ellipsoidal set in N-dimensional Euclidean space. The minimum buckling load is then evaluated in both the hypercuboid and the ellipsoid. A comparison between these methods and the probabilistic method are performed, where the probabilistic results at different reliability levels are taken as the benchmarks of accuracy for judgment. It is demonstrated that a nonprobabilistic model of uncertainty may be an alternative method for buckling analysis of a column on a nonlinear mixed quadratic-cubic elastic foundation under limited information on initial imperfection.

scholarly journals The Effect of General Imperfections on the Buckling of Cylindrical Shells

1969 ◽  
Vol 36 (1) ◽  
pp. 28-38 ◽  
Author(s):  
Johann A´rbocz ◽  
Charles D. Babcock
Keyword(s):  
Axial Load ◽  
Circular Cylindrical Shell ◽  
Three Dimensional ◽  
Initial Imperfection ◽  
Buckling Load ◽  
Data Recording ◽  
Buckling Loads ◽  
Recording Process ◽  
Global Buckling ◽  
Experimental Values

An experimental and theoretical investigation of the effect of general imperfections on the buckling load of a circular cylindrical shell under axial compression was carried out. A noncontact probe has been used to make complete imperfection surveys on electro-formed copper shells before and during the loading process up to the buckling load. The data recording process has been fully automated and the data reduction was done on an IBM 7094. Three-dimensional plots were obtained of the measured initial imperfection surfaces and of the growth of these imperfections under increasing axial load. The modal components of the measured imperfection surfaces were also obtained. The theoretical solution located the limit points of the postbuckled states. A simplified imperfection model was used consisting of one axisymmetric and two asymmetric components. For global buckling the correlation between the theoretical buckling loads and the experimental values was found to be good.

scholarly journals Energy Absorption Due to Oblique Impact Crushing of Thin-Walled Tubes

2018 ◽  
Vol 183 ◽  
pp. 04001
Author(s):  
Tsutomu Umeda ◽  
Koji Mimura
Keyword(s):  
Strain Rate ◽  
Fuel Efficiency ◽  
Cylindrical Tube ◽  
Initial Imperfection ◽  
Oblique Impact ◽  
Buckling Load ◽  
The Mean ◽  
Thin Walled ◽  
Energy Absorbers ◽  
Crushing Behavior

From the viewpoint of improving both the crash safety and the fuel efficiency, various shaped thin-walled tubes have been utilized as energy absorbers of automobiles such as front side members, crash boxes and so forth. In the axial crushing test of the regular polygonal tube, if the number of angles was small enough, it showed a certain inherent wrinkle mode, and the mean buckling load increased with that number, while it showed the mode of cylindrical tube if that number became larger. In the oblique crushing test, the same tendency was also shown within the range that the transition from axial collapse to bending collapse did not occur. This transition considerably decreases the mean buckling load so that it is important to know the threshold crush angle for the transition. Then, the crushing behavior of regular 4-12 angled tubes were investigated with changing the crush angle mainly by the experiment. The threshold angle is sensitively influenced by the initial imperfection and the boundary condition so that both the threshold angles obtained by the experiment and by the calculation for the square tube are 8-13° smaller than that predicted by the equation proposed by Han and Park. For the carbon steel S25C, the increase of the strain rate in the axial collapse mode raises the mean buckling load, while it shows little strain rate dependence once the transition occurs.

Initial Imperfection Simulation and Effect on Shear Buckling of Corrugated Steel Webs

2011 ◽  
Vol 308-310 ◽  
pp. 2463-2470
Author(s):  
Jian Yong Song ◽  
Ya Mei Yu ◽  
Shuo Zhang
Keyword(s):  
Steel Plate ◽  
Plate Thickness ◽  
Initial Imperfection ◽  
Buckling Load ◽  
Buckling Mode ◽  
Shear Buckling ◽  
Nonlinear Shear ◽  
Calculation Analysis ◽  
Better Than

The nonlinear shear buckling of corrugated steel webs is completed by ANSYS. Consistent mode imperfection method is adopted for simulating corrugation configuration imperfection of corrugated steel plate, shear buckling calculation analysis result shows that ultimate shear buckling load of corrugated steel webs is decreased with increasing in corrugation configuration imperfection. Analysis results shows that oversized corrugation configuration imperfection will decrease the ultimate shear buckling load of corrugated steel webs, but premature buckling caused by steel plate thickness imperfection of corrugated steel webs is much better than plain steel webs, and the ultimate shear buckling load and buckling mode will not be much effected by such steel plate thickness imperfection. On this basis, the influences of corrugation configuration to ultimate shear bucking load and buckling mode are investigated.

Non-Probabilistic Models of Uncertainty in the Nonlinear Buckling of Shells With General Imperfections: Theoretical Estimates of the Knockdown Factor

1989 ◽  
Vol 56 (2) ◽  
pp. 403-410 ◽  
Author(s):  
Yakov Ben-Haim ◽  
Isaac Elishakoff
Keyword(s):  
Probabilistic Models ◽  
Theoretical Estimate ◽  
Initial Imperfection ◽  
Theoretical Models ◽  
Buckling Load ◽  
Dimensional Euclidean Space ◽  
Theoretical Treatment ◽  
Nonlinear Buckling ◽  
Initial Imperfections ◽  
Geometrical Imperfections

A non-probabilistic, set-theoretical treatment of the buckling of shells with uncertain initial geometrical imperfections is presented. The minimum buckling load is determined as a function of the parameters which describe the (generally infinite) range of possible initial imperfection profiles of the shell. The central finding of this paper is a theoretical estimate of the knockdown factor as a function of the characteristics of the uncertainty in the initial imperfections. Two classes of set-theoretical models are employed. The first class represents the range of variation of the most significant N Fourier coefficients by an ellipsoidal set in N-dimensional Euclidean space. The minimum buckling load is then explicitly evaluated in terms of the shape of the ellipsoid. In the second class of models, the uncertainty in the initial imperfection profile is expressed by an envelope of functions. The bounding functions of this envelope can be viewed as a radial tolerance on the shape. It is demonstrated that a non-probabilistic model of uncertainty in the initial imperfections of shells is successful in determining the minimum attainable buckling load of an ensemble of shells and that such an approach is computationally feasible.

scholarly journals INFLUENCE OF BUCKLING FORMS INTERACTION ON STIFFENED PLATE BEARING CAPACITY

2020 ◽  
Vol 16 (2) ◽  
pp. 83-93
Author(s):  
Gaik Manuylov ◽  
Sergey Kosytsyn ◽  
Irina Grudtsyna
Keyword(s):  
Peak Load ◽  
Initial Imperfection ◽  
Buckling Load ◽  
Local Form ◽  
Stiffened Plate ◽  
A Value ◽  
Decline Curves ◽  
Bifurcation Surface ◽  
Buckling Failure ◽  
Element Set

The work is devoted to studying the influence of initial geometric imperfections on a value of the peak load for the compressed stiffened plate with the two-fold buckling load. The finite-element set MSC PATRAN – NASTRAN was used for solving the set tasks. When modelling the stiffened plate, flat four-unit elements were used. Geometric non-linearity was assumed for calculations. The plate material was regarded as perfectly elastic. Buckling forces of stiffened plate at the two-fold buckling load were calculated (simultaneous buckling failure on the form of the plate total bending and on the local form of wave formation in stiffened ribs). Equilibrium state curves, peak load decline curves depending on initial imperfection values and the bifurcation surface were plotted.

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