It is well known that the actual buckling stress of a circular cylindrical shell subjected to torsion is only about 60 to 70% of the critical stress calculated from the linear theory, as obtained by various investigators. Authors consider that this discrepancy between the theoretical and experimental values of buckling stress has its cause in the Durchschlag phenomenon, as well as the case of buckling under compression.
The existence of the Durchschlag phenomenon in the case of torsional buckling should be justified from the fact that the post-buckling shape of the shell shows a nearly developable surface, for which the extensional energy of the shell is comparable with its bending energy. According to this idea, we calculate in the present paper, the lower buckling stress for the torsional buckling, which is satisfactory for explaining the experimental results.