Plastic buckling of circular cylindrical shells under nonuniform axial loads

Elastoplastic buckling of circular cylindrical shells subjected to piecewise-uniform circumferentially varying axial loads is studied within the framework of linear stability analysis in conjunction with small strain plasticity. Both J 2 flow and deformation theories with arbitrary hardening are used to model material behavior. Donnell-type equations are solved separately for each loaded segment with the interfacial continuity conditions providing the eigenvalue equation for the buckling parameter. Sample results are presented for pure bending and for uniform compression over a finite axial band. In all cases, deformation theory predicts buckling loads smaller than those obtained from flow theory. Loading nonuniformity becomes appreciable as the applied stresses concentrate over a narrow axial band. In that context we discuss the possibility of plastic buckling under the action of concentrated forces. The analysis is restricted to a membrane prebuckling state of stress and hence applicable to relatively short shells.