Plastic buckling of initially imperfect stiffened cylinders in axial compression

Bibliography: leaves 117-118.Bifurcation in the plastic range of axially compressed stringer-stiffened cylinders is investigated. The shell under consideration is assumed to have an initial imperfection in the form of a sinusoidal deviation both axially and circumferentially.The constitutive relation employed here is J 2 deformation theory of plasticity. This relation, as well as kinematic assumptions regarding the behaviour of the panels and stiffeners which constitute the stiffened shell is used in the principle of virtual work to obtain a set of non-linear algebraic equations whose solution provides complete information about the prebuckling equilibrium path. Bifurcation from the primary path is examined by making use of a functional whose first variation is zero when two solutions to the problem are possible. This leads to an eigenvalue problem, the eigenvalue being the critical compressive load and the eigenfunction being the corresponding buckling mode. Results are presented or shells of different geometries and material properties, a limited comparison of theoretical results as obtained by this analysis with available experimental data is also made