NONSYMMETRIC BUCKLE PATTERNS IN PROGRESSIVE PLASTIC BUCKLING,
STANFORD UNIV CALIF DEPT OF AERONAUTICS AND ASTRONAUTICS
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This paper presents the results of a series of experiments on the progressive plastic buckling of cylindrical shells under axial compressive load. It shows that for shell bodies with an Rt less than 100 the normal axisymmetric ring buckling will develop into nonsymmetric patterns. We demonstrate that there exist also a class of shells within this thickness-radius range for which nonsymmetric plastic buckling always occurs without the prior formation of a ring. It appears from the limited number of tests made that for a particular R, Rt, material and rate of loading there is a critical value of L, above which there is a high probability of the buckle pattern developing in a nonsymmetric fashion. It seems probable, too, that there are bands of Rt for a particular LR, R, material and rate of loading for which the buckle number will be constant. The experiments tend to indicate that the postbuckling efficiency of the shell decreases with increasing buckle number. The nonsymmetric patterns demonstrated appear to be inextensional deformations. They are very similar in character to the Yoshimura pattern which occurs as the limiting case for thin shells in axial compression and, under impact loading. Load displacement histories are presented for some of the various modes of failure demonstrated.