The buckling of cylindrical shells with an initial imperfection under axial compression loading

An experimental and theoretical investigation of the effect of a specific type of initial imperfection on the buckling load of a circular cylindrical shell under axial compression loading was carried out. The imperfection studied was axially symmetric in shape and had the form of a half sine wave in the length direction. Both inward and outward bowing imperfections were considered. The experiments were carried out with shells fabricated by a copper electroforming process. The shells had no longitudinal seams and had unintended imperfections of the order of the wall thickness. The buckling stress for the intended imperfection studied was only slightly influenced over a considerable range of imperfection amplitudes. The theoretical solution located the bifurcation points of the prebuckled axially symmetric state. The solution showed that outward bowing shells should have the same buckling stress as a perfect cylindrical shell and inward bowing shells should have a lower buckling stress than the perfect cylinder