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Moderately thick perfect cylindrical shells under axial compression first exhibit an axisymmetric buckling mode, where a localization of buckling patterns, referred to as an elephant foot bulge, is caused by the first plastic bifurcation. However, the transition from the axisymmetric buckling mode to a nonaxisymmetric buckling mode, referred to as a diamond buckling mode, may occur due to the next bifurcation if we continue the loading under displacement control. Herein, this phenomenon is examined, based on a rigorous plastic bifurcation analysis. As a result, it is observed that the circumferential wave number of the diamond buckling mode increases with the decrease of the wall thickness. The boundary conditions also considerably influence the occurrence of diamond buckling. It is found that the strain concentration is intensified for the diamond buckling modes, compared with the axisymmetric modes.

This paper investigates the cyclic-localization behavior of axisymmetric plastic buckling patterns of cylindrical shells in terms of its influence on strength deterioration. Since localization occurs due to a plastic bifurcation in the postpeak range, we first present a rigorous method to analyze the plastic bifurcation under the two-axial stress state, which is characteristic of the axisymmetric buckling. In this analysis, we also use an accurate cyclic plasticity constitutive model. The validity of the proposed theoretical approach to localization behavior is confirmed by a cyclic loading test on thick cylindrical shells. Then, using the proposed method, we precisely examine the effects of structural parameters as well as boundary conditions on localization behavior.