The Effects of Stiffness on the Buckling of Cylinders with Moderate Wall Thickness

• Main Author: Ponsford, Henry Thomas
• Format: Others
• Published: 1953
• Online Access: https://thesis.library.caltech.edu/1674/1/Ponsford_ht_1953.pdf; Ponsford, Henry Thomas (1953) The Effects of Stiffness on the Buckling of Cylinders with Moderate Wall Thickness. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/JAYX-PF29. https://resolver.caltech.edu/CaltechETD:etd-05082003-160210 <https://resolver.caltech.edu/CaltechETD:etd-05082003-160210>

A series of 25 complete cylinders was tested experimentally to determine the effects of stiffening elements on the buckling of cylinders with moderate wall thickness, and to present a physical basis for an understanding of the mechanism of cylinder buckling. It was found that both axial and circumferential stiffeners spaced at distances comparable to the buckle wave length of the unstiffened cylinder will raise the buckling stress, reduce the wave length, and alter the shape of the buckling waves. It was shown that for cylinders of D/t = 400, the addition of axial stiffening as little as 2% or 3% of the cylinder wall material can raise the buckling stress by 30% over the unstiffened case. The experiments of this study lend support to a theory developed by Donnell and Wan which ascribes the reduction of the buckling stress of a real cylinder below the classical theoretical value to the initial imperfections of construction in the real cylinder. Conversely, the results cast doubt on the validity of the theory which explains the "premature" failure on the basis of external energy disturbances present in the testing laboratory. It was shown that the buckling waves of a reasonably well-made cylinder develop with extreme rapidity without the necessity of a change in cylinder length, and are fully developed in their lateral dimensions throughout the buckling process. Some previous results of Kanemitsu and Nojima which exhibited an essentially different buckling mechanism were explained as the consequence of excessive initial imperfection. A brief study of the vibrations of a cylinder under axial load demonstrated an approximate correlation between the vibration and buckling modes of the cylinder.