Buckling modes of circular cylindrical shells under axial compression.

Abstract

Geometrically near-perfect, circular cylindrical photoelastic shells having radius-to-thickness ratios of the order 100-440 have been tested in pure axial compression. The critical buckling loads were found to agree within 10-14% of the classical value, or within a few percent of the reduced buckling load taking into account the clamped end constraint. High-speed photographs of the buckling process were obtained using two cameras viewing the change in the 45° isoclinics over the entire cylinder's length and over 60% of the cylinder's perimeter. A theoretical analysis of the inception of buckling using Koiter's mode shapes has demonstrated that the classical buckling mode was observed in these experiments for the first time. Further analysis of the nonlinear postbuckling mode shapes, just after initial buckling, predicted the subsequent wave forms observed. It was also determined that the shallow shell equations used to describe large-deflection postbuckling behavior do not predict isoclinic patterns that are observed in the later stages of buckling. Consequently, it is concluded that postbuckling load calculations based on these equations are inaccurate beyond the early stages of buckling for the shells tested. E F L lx,ly m,n p