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Quan Wang - One of the best experts on this subject based on the ideXlab platform.
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Instability analysis of double-walled carbon nanotubes subjected to axial compression
Journal of Applied Physics, 2008Co-Authors: Quan WangAbstract:The Buckling of short double-walled carbon nanotubes subjected to compression is investigated through molecular dynamics in the paper. The inner wall is discovered to have helically aligned Buckling Mode while the outer wall is reported to have shell Buckling Mode with kinks. Such Buckling Modes are attributed to the interaction of the two walls via the van der Waals effect. In addition, a Buckling strain higher than the Buckling strains of two constituent inner and outer walls is found in the double-walled tube within a certain size range. The causes for such a phenomenon are analyzed and discussed.
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Torsional Buckling of double-walled carbon nanotubes
Carbon, 2008Co-Authors: Quan WangAbstract:The mechanical instability of doubled-walled carbon nanotubes subject to torsion motion is investigated through molecular dynamics. A newly revealed Buckling Mode with one or three thin, local rims on the outer tube was discovered while the inner tube shows a helically aligned Buckling Mode in three dimensions. The distinct Buckling Modes of the two tubes imply the inapplicability of continuum mechanics Modeling in which it is postulated that the Buckling Modes of the constituent tubes have the same shape. In view of this problem, a new concept of the equivalent thickness of double-walled carbon nanotubes is introduced, which enables the Kromm shell Model to be applied to the derivation of the torsional Buckling angle without the restraint of the two tubes having identical shapes.
Wei-chau Xie - One of the best experts on this subject based on the ideXlab platform.
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Buckling Mode localization in rib stiffened plates with misplaced stiffeners kantorovich approach
Chaos Solitons & Fractals, 2000Co-Authors: Wei-chau Xie, Isaac ElishakoffAbstract:Abstract Buckling Mode localization in rib-stiffened plates with randomly misplaced stiffeners is studied in this paper. The method of Kantorovich on reducing a partial differential equation to a system of ordinary differential equations is employed to obtain the deflection surface of the rib-stiffened plates under axial compressive load. The edges of the plates normal to the stiffeners can be either simply supported or clamped. The solutions of the deflection surface are then expressed in the form of transfer matrices. The expressions of the solutions obtained for the case of one edge simply supported and one edge clamped and the case of two edges clamped are similar to those for the case of two edges simply supported. When the two edges are simply supported, the method of Kantorovich yields the exact results. Localization factors, which characterize the average exponential rates of growth or decay of amplitudes of deflection, are determined using the method of transfer matrix. The method of Kantorovich is a general approximate method, which is applicable for various support conditions.
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Buckling Mode localization in rib stiffened plates with misplaced stiffeners a finite strip approach
Chaos Solitons & Fractals, 2000Co-Authors: Wei-chau Xie, A. IbrahimAbstract:Abstract Buckling Mode localization in rib-stiffened plates with randomly misplaced stiffeners is studied in this paper. A method of finite strip is employed to establish the equations of equilibrium for the rib-stiffened plates under axial compressive load. The equations of equilibrium are then expressed in the form of transfer matrices. Localization factors, which characterize the average exponential rates of growth or decay of amplitudes of deflection, are determined using the method of transfer matrix. The results obtained from a finite strip formulation agreed very well with those obtained from a previous study using an analytical approach. The method of finite strip presented in this study is suitable for studying the localization phenomenon in Buckling Modes of rib-stiffened plates, especially those with nonuniform cross sections.
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Buckling Mode localization in rib-stiffened plates with misplaced stiffeners – a finite strip approach
Chaos Solitons & Fractals, 2000Co-Authors: Wei-chau Xie, A. IbrahimAbstract:Abstract Buckling Mode localization in rib-stiffened plates with randomly misplaced stiffeners is studied in this paper. A method of finite strip is employed to establish the equations of equilibrium for the rib-stiffened plates under axial compressive load. The equations of equilibrium are then expressed in the form of transfer matrices. Localization factors, which characterize the average exponential rates of growth or decay of amplitudes of deflection, are determined using the method of transfer matrix. The results obtained from a finite strip formulation agreed very well with those obtained from a previous study using an analytical approach. The method of finite strip presented in this study is suitable for studying the localization phenomenon in Buckling Modes of rib-stiffened plates, especially those with nonuniform cross sections.
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Buckling Mode localization in rib-stiffened plates with randomly misplaced stiffeners
Computers & Structures, 1998Co-Authors: Wei-chau XieAbstract:Abstract Buckling Mode localization in rib-stiffened rectangular plates with randomly misplaced stiffeners is studied in this paper. Localization factors, which characterize the average exponential rates of growth or decay of amplitudes of deflection, are determined using the method of transfer matrix. The smallest positive Lyapunov exponent of the corresponding discrete dynamical system is the localization factor of interest. For a plate simply supported at the rib-stiffeners, the Buckling behaviour of the plate is similar to that of a multispan continuous beam. The effect of misplacement of the rib-stiffeners on Buckling Mode localization increases with the increase of the flexural rigidities of the stiffeners. The larger the values of the torsional rigidities of the rib-stiffeners, the larger the values of the localization factors and the degrees of localization in the Buckling Modes.
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Buckling Mode localization in nonhomogeneous beams on elastic foundations
Chaos Solitons & Fractals, 1997Co-Authors: Wei-chau XieAbstract:Abstract Buckling Mode localization in nonhomogeneous beams on elastic foundations is studied in this paper. The classical theory of localization for randomly disordered nearly periodic structures is extended to nonhomogeneous continuous structures. Lyapunov exponents, which characterize the average exponential rates of growth or decay of amplitudes of deformation, are determined using the method of transfer matrix. The smallest positive Lyapunov exponent is the localization factor of interest. As an alternative approach, Green's function method coupled with a finite element formulation is applied to evaluate the localization factors. The results obtained in this paper provide an explanation on localized Buckling observed in experiments.
Amr Mohamed Khalil - One of the best experts on this subject based on the ideXlab platform.
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wall thickness variation effect on tank s shape behaviour under critical harmonic settlement
alexandria engineering journal, 2016Co-Authors: Ahmed Fahmy, Amr Mohamed KhalilAbstract:Abstract The purpose of this study was to investigate the effect of wall thickness variation on tank’s wall Buckling Mode under the effect of critical harmonic settlement for open top tanks. The study was performed on four tanks which have the same geometric and material properties except wall thickness, for each case the tank was subjected to several settlement waves which has the same settlement amplitude, and the Buckling Mode and critical vertical settlement results were compared. For Buckling Mode, the results show that tanks with wall thickness at a close range have similar Buckling Mode behaviour and in case using too thick wall the Buckling Mode starts to change. And for the effect on critical vertical settlement, the results show that vertical settlement is sensitive to any variation in wall thickness beside that settlement value changes with the effected wave number and this variation could change the whole behaviour of the tanks. The study recommended that in case of performing analysis for a tank with neglecting the variation in wall thickness values, the value of chosen wall thickness should be the average of wall thickness values obtained from the designed equation.
Changfeng Chen - One of the best experts on this subject based on the ideXlab platform.
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aspect ratio dependent Buckling Mode transition in single walled carbon nanotubes under compression
Journal of Applied Physics, 2011Co-Authors: Jeremy Feliciano, Chun Tang, Yingyan Zhang, Changfeng ChenAbstract:Using molecular dynamics simulations, we study axial compressive behavior of single-walled carbon nanotubes (SWCNTs) with a wide range of aspect ratios (length to diameter ratio). It is shown that the difference in aspect ratio leads to distinct Buckling Modes in SWCNTs. Small-aspect-ratio SWCNTs primarily exhibit shell Buckling; they switch to a column Buckling Mode with increasing aspect ratio. Further compression of the already column buckled large-aspect-ratio SWCNTs results in a shell Buckling. This shell Buckling Mode is distinct from that of small-aspect-ratio SWCNTs in that it originates from the column Buckling induced bending deformation. The transition strain from column Buckling to shell Buckling of large-aspect-ratio SWCNTs is predicted using an analytical expression. The underlying mechanism is discussed by analyzing the variation of C-C bond lengths and angles.
Ahmer M Wadee - One of the best experts on this subject based on the ideXlab platform.
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interactively induced localization in thin walled i section struts Buckling about the strong axis
Structures, 2015Co-Authors: Elizabeth L Liu, Ahmer M WadeeAbstract:Abstract A variational Model describing the behaviour of a thin-walled I-section strut suffering from local–global Buckling Mode interaction is presented where global (Euler) Buckling about the strong axis is the critical Mode. A system of differential and integral equations is derived that describe the equilibrium states from variational principles and are solved numerically using the continuation and bifurcation software A uto -07 p for the perfect case. Initially stress relieved out-of-straightness imperfections are subsequently introduced and the nonlinear response is Modelled. The Modelled interaction is between the critical global Buckling Mode about the strong axis and local Buckling in the flange and web simultaneously, where the flange–web joint is assumed to be free to rotate as a rigid body. The initial eigenMode is shown to be destabilized at a secondary bifurcation where interactive Buckling is triggered. A progressive change in the Buckling Mode is then observed, initially with local Buckling localizing at the mid-span of the compression flange, which also triggers sympathetic local Buckling in the web. The results from the analytical Model have been validated using the commercial finite element (FE) software A baqus with good comparisons presented for the initial post-Buckling behaviour. The strut also exhibits sensitivity to initial out-of-straightness imperfections, with a notable decrease in the ultimate load as the imperfection size increases. The ultimate loads for a range of imperfection amplitudes are found using both analytical Models and FE analysis, with very good correlation observed.
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cellular Buckling in i section struts
Thin-walled Structures, 2014Co-Authors: Ahmer M Wadee, Li BaiAbstract:An analytical Model that describes the interactive Buckling of a thin-walled I-section strut under pure compression based on variational principles is presented. A formulation combining the Rayleigh–Ritz method and continuous displacement functions is used to derive a system of differential and integral equilibrium equations for the structural component. Numerical continuation reveals progressive cellular Buckling (or snaking) arising from the nonlinear interaction between the weakly stable global Buckling Mode and the strongly stable local Buckling Mode. The resulting behaviour is highly unstable and when the Model is extended to include geometric imperfections it compares excellently with some recently published experiments.
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Buckling Mode interaction in prestressed stayed columns
Proceedings of the Institution of Civil Engineers - Structures and Buildings, 2013Co-Authors: Ahmer M Wadee, Leroy Gardner, Tyrone A HuntAbstract:Prestressed stayed columns offer an innovative and aesthetically attractive solution where designs demand long and slender elements under compression. The addition of cross-arms and pretensioned ca...
