The purpose of this paper is to describe the secondary buckling analysis of rectangular plates under axial compression by the finite element method. This method, which is proposed by the author et al., is a kind of lagragian formulation, and is very convenient for the nonlinear analysis of beams and plates. In this paper, as typical examples of this method, the results of uniformly compressed square plates with four types of boundary conditions is presented. In detail, the post-buckling path of the square plates is calculated, and also the secondary buckling value and the deformation mode are caluculated, which is obtained when the deformation after the buckling becomes large and unstable again. Finally, this method is available for the analysis of rectangular plates with initial imperfection or reinforced members, but is not used for such cases in this paper because of the shortage of page.
In this paper the authors applied an analytical method, which was used in the previous paper, Jour. Japan Soc, Aero. Space Sci., Vol. 15, No. 162, by means of the well-known Rayleigh-Ritz's procedure, to the analysis of the natural vibration characteristics of the aircraft structural models. General analytical equations were formulated for these. Numerical examples were considered for models consisting of combination beam and cantilevered built-up wings, applying the formula to these special cases and a model consisting of a cylindrical fuselage and built-up wings with an aspect ratio of about 7. At the same time, vibration test of these models were carried out. Comparisons of both results showed that there were fairly good correlations between them, though there are some troubles, which were examined numerically, in the calculation of eigenvalues. It is concluded that this analytical method cannot be overlooked, as it is one of the most suitable ways of predicting vibration characteristics of these structures in the earlier design phase, although the powerful finite element method is widely applied to these complicated or real airplane structures.
Unstiffened truncated conical shells were tested for flutter at a Mach number 2.0 in the NAL 1-by 1-meter blowdown wind tunnel. The shells were made of super-invar in order to avoid the thermal stresses and had a ratio of slant length to small radius 1.61 and a semivertex angle of 14°. The experimental results were in good agreement with a flutter boundary calculated by the FEM based on a Donnell-type theory. Vibration and external pressure buckling tests were also performed with good agreement be- tween theory and experiment.
Inthispaperbucklingofcylindricalsandwich shells with closed ends under uniform external pressure is analyzed. External pressure distributed uniformly Over the end closures turns into axial loads on the two facings. The ends of the cylinder are constrained such that they experience no radial or circumferentia ldisplacements and they are free from bending moments.Analysis on this theme was treated by M.E.RAVILLE (FPL 1844-B). He considered, however, only the external pressure over the cylindrical surface. Buckling theory used here is the classical small deflection theory. Buckling stresses can be obtained from the equation of a complicated sixth order determinant, and were calculated numerically. Computed results for critical buckling loads are expressed for various parameters such as thickness-radius ratio or length-radius ratio, and the buckling characteristic curves are shown by which how the critical load varies with the values of these parameters is revealed.