In our previous papers, accuracy of numerical methods for two dimensional lifting airfoils in inviscid flow were investigated. In this paper, these works are extended to the spanwise problem, namely quasi-lifting lines. Two interpolation methods and five Vortex Lattice Methods are compared, which have cotφ/2 mode and δ mode of chordwise load distributions respectively. In addition, one hybrid method is also investigated. Accuracy of numerical solutions are estimated using "normalwash comparison method+relative error method." Interpolation methods need about six times larger computational time than those of Vortex Lattice Methods at the same numbers of loading points. For numerical accuracy, the Vortex Lattice Method having semi-circle spanwise division without tip-inset is best. Vortex Lattice Methods and interpolation methods converge to slightly different solutions, which result from the assumptions of dissimilar chordwise load distributions. The discrepancy between them however causes no practical problems.
Using the pseudo-equilibrium hybrid element, we formulate the equation of motion which the structures are subjected to the plastic large deformation. And the dynamic responses of cylindrical shell, which is simply supported at both ends and compressed in the direction of its axis, are examined. In this study it is restricted us to consider an axisymmetrical deformation. As a result, it is recognized that the amplitude of prescribed load and the deformation velocity cause the apparent differences of deformation modes compared with the static one.
The shear buckling strengths of twelve kinds of CFRP laminated square panels clamped on each edge were investigated experimentally and analytically. The experiments were performed by a newly designed test apparatus. Finite element method based on modified HELLINGERREISSNER principle was employed in order to analyse the post-buckling large-deflection behavior. Except unidirectional laminated panels, there is almost satisfactory agreement between the analytical and experimental results for both the buckling load and the post-buckling behavior, and the following properties are disclosed. 1) The buckled shape is three half-wave type and the failure occurs without secondary buckling phenomena. 2) Both buckling load and maximum load vary depending on the stacking sequence of twelve plies of lamination. 3) As for the panels which contain a lot of +45° plies, the effects of material nonlinearity of shear modulus appear before failure. 4) In the case of the present length-thickness ratio which is 200mm/1.4mm, the maximum load is fairly greater than the buckling load, and therefore CFRP panels can be used in the post-buckling state. However, it is noteworthy that the CFRP panel fails almost elastically, different from duralumin plates. 5) From the view point of the maximum load, the FEM analysis yields either [3(0°, 90°)/sym.] or [3(90°, 0°)/sym.] is the optimum lamination, however the experiment yields [2(90°, 0°), -45°, +45°/sym.] is optimum.