BUCKLING AND POSTBUCKLING OF SPHERICAL-SHELLS WITH APICAL CUTOUT UNDER RING LOAD

The buckling and postbuckling behavior of elastoplastic spherical shel ls with circular apical, cutout under a ring load was investigated ana lytically and experimentally. A finite element code based on the updat ed Lagrangian formulation was established to analyze this buckling pro blem by considering nonlinear geometric and material properties. An it erative scheme controlled by displacement was adopted in the solution procedure to avoid numerical instability near the limit buckling load. Ring loads of both line and strip types were analyzed. A testing devi ce was used to perform buckling experiments. The ratio of diameter to thickness of the steel specimens was between 30.23 and 86.75. The infl uence of the ratio of diameter to thickness and the sizes of the epica l cutout and ring load on the limit buckling load are discussed. The a nalytical results agree satisfactorily with experimental ones for medi um carbon steel spherical shells, Convex and concave modes of postbuck ling deformation around the apex are obtained in analysis and observed in experiment for varied combinations of the sizes of ring load and a pical cutout and ratio of diameter to thickness of the spherical shell s.