Photograph supplied by Michael Nemeth, NASA Langley Research Center, Hampton, Virginia
This and the next two slides are from "Structural behavior and compressive strength of circular cylinders with longitudinal stiffening", NASA TN D-1251, May 1962 by James P. Peterson, Ralph O. Whitley and Jerry W. Deaton
Results of compression tests on 17 circular cylinders with [internal] longitudinal stiffening are presented and discussed. In addition, supplementary studies of the compressive load-shortening characteristics of plates with large width/thickness ratios and of the strength of [wide] columns consisting of longitdinally stiffened sheet which buckled prior to [wide]column failure are given and employed in analyses of the cylinder tests. Correlation between experiment and analysis was achieved in predicting local buckling of the skin and in predicting the load-shortening characteristics of the cylinders. Correlation was also achieved in predicting the panel [general] instability loads of the longer cylinders, but the shorter cylinders failed at loads considerably less than those predicted, evidently by a mode of deformation not considered in the analysis.
The internal stringers have Z cross sections.
In this photograph the local buckles are easy to see, but the general buckling mode is a bit harder to see. Try squinting to perceive the general buckling mode better. The general buckling mode has one half wave in the axial direction and about four circumferential waves over 180 degrees.
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