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Time sequence of local post-buckling deformations in an axially compressed blade-stiffened flat panel

This is Fig. 29 from the 1997 modejump paper. Shown here are six edge-on views of the locally post-buckled axially compressed PANEL I. (PANEL I = optimized panel generated by PANDA2 with the PANDA2 mode-jumping constraint turned off during optimization cycles, that is, with mode jumping permitted at any applied load factor.)

These six frames were selected from output from the STAGS nonlinear transient analysis phase conducted at constant load factor, PA = 0.7013, which is the STAGS load factor just above the load level at which STAGS failed to converge to a nonlinear static equilibrium state in a previous STAGS execution for the prediction of nonlinear static equilibrium under increasing load.

Each frame corresponds to a peak value of dynamic hoop stress shown in the next slide.

During this transient phase that immediately follows the first nonlinear static instability phase, the deformation history is characterized mainly by local buckles in the panel skin sliding to and fro (leftward and rightward) along the axis of the stiffened panel.

Note that in Frame (a) there are about 8 axial half-waves; in Frame (d) there are about 9 axial half-waves; and in Frame (f) there are about 10 axial half-waves in the local post-buckled deformation pattern predicted by STAGS. This is dynamic mode jumping.

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