Buckling Analysis Of Damaged Mono-shell Submarine Structure

The buckling of the structure of the submarine is one of its main technique capability factors. But the submarines on active service use the experience of the Former Soviet Union for reference and adopt double-shell, including an outer shell and a pressure hull, for a long time. But the mono-shell submarine has better hydrodynamic performance and economy, so it is paid more and more attention to. Because the pressure hull is not protected by the outer shell, the mono-shell submarine is more easily damaged than the double-shell submarine. The accident collision, taking the ground, explosion impact and weapons' hitting in wartime can induce that the hull is damaged. The pressure hull of the submarine is sensitive to imperfections and buckling, so the buckling analysis of the pressure hull of the submarine is an important subject, especially when the hull has plastic deformation.The buckling analysis of the single shell submarine with initial imperfections and the characteristics of the hull is study in the paper. But the buckling analysis of the imperfect hull is the main subject of the paper.By employing FEM analysis software, the Eigen buckling of both a ring-stiffened cylinder and a ring and stringer-stiffened cylinder are calculated. The results demonstrate the ring and stringer stiffened cylinder has higher critical load and better stability. So the ring and stringer-stiffened cylinder is advised for the characteristics of the mono-shell submarine.By employing the Von Karman-Donnell nonlinear theory for geometrically imperfect and thin cylinders and variational methods, the compatibility and equilibrium equations of the damaged hull are derived. Based on the compatibility and equilibrium equations the expression of stress function can be obtained. By employing the Ritz method, the expression of geometric nonlinear critical load of the damaged hull under hydrostatic pressure is derived in the paper.Based on the flow theory and the deflection theory, the prebuckling constitutive equations of the pressure hull are obtained. By piecewise polynomials and the Ramberg-Osgood three-parameter equation fitting the stress-strain curve, the expressions of the tangent and secant modulus are derived. The analysis method of plastic buckling for the damaged hull subjected to hydrostatic pressure is given by employing the Von Karman-Donnell nonlinear theory for geometrically imperfect and thin cylinders and the Ritz method.The calculations are carried out for ring and stringer-stiffened cylinders with variable initial imperfection amplitudes. The results of the theoretical and FEM analysis are compared. It is shown that the theoretical method is valid and credible.