Buckling of Open Cylindrical Shells with Imperfections

Buckling of open cylindrical shells with free longitudinal edges and simply supported ends, subjected to an axial compression, with imperfections due to end eccentricity or initial deflections, is examined. Field equations based on large deflection theory are reduced to a set of nonlinear finite difference equations and a computer technique for solving this set by the Newton-Raphson method is presented. Equilibrium paths and deflection patterns for examples with three types of imperfections (constant end moment, constant end eccentricity and specified initial deflection) are presented. The equilibrium paths exhibit an asymmetric type of postbuckling behavior; that is, negative imperfections which initially cause the shell to deflect outward would cause a buckling load lower than the linear buckling load without imperfections; whereas, positive imperfections would cause the opposite if there is no external disturbance. The behavior of a shell with Poisson's ratio μ ≠ 0 and circumferential displacement equal to zero at the ends, is similar to a shell with negative imperfections since the axial compression would induce an outward (negative) displacement.