LAUSR

Abstract Thick-walled cylinders, which are loaded by accidentally excessive internal or external pressure, axial force or both, may fail due to non-symmetric bifurcation modes with multiple axial and peripheral waves. These failure modes are most relevant to submarines, onshore- and offshore pipelines, vacuum containers, subsea structures, and pressure vessels. Continuum theory is adopted to analyze the bifurcation behavior of such cylinders, considering large elastic-plastic deformation with non-linear hardening. The presented general comprehensive solution is capable of calculating the loads and deformation at the onset of bifurcation for modes of any order in both axial and peripheral directions. As a case study, several bifurcation limit curves of different orders have been calculated using the proposed theoretical solution for a closed thick-walled long cylinder loaded radially and axially. The results are validated numerically by FEA simulations using commercial software. Limit curves of column buckling (first order) and section-collapse (second or higher order) modes of bifurcation are calculated using the proposed solution. The results demonstrate that adding tensile or compressive axial force to external pressure loading delays the occurrence of the section-collapse bifurcation mode. On the other hand, adding external or internal pressure to an axial compression force, the axial strain at column buckling is also increased. The results also explain and quantify the transition between section-collapse and column-buckling bifurcation modes. While the presented results focus on different modes of non-symmetric buckling, the theory is also capable of calculating the axisymmetric and non-symmetric bulging as well as axial necking bifurcation modes. The presented solution offers deeper insight and substantial help to the designers of thick-walled cylindrical components of structures, particularly those subject to excessive external pressure, possibly combined with an axial force.