Research On Stability Of Pressure Cylindrical Shell Based On Stiffness Reduction

The submarines develop rapidly with ocean development and application in military. As the main structural style of submarine pressure hull, all kinds of initial defects of cylindrical shells are generated inevitably during producing and manufacturing, which affect the load-carrying capacity of cylindrical shells badly. Therefore, it has important theoretical significance and practical engineering significance to study the effects of axisymmetric initial imperfection, local initial dents and non- axisymmetric initial imperfection on load-carrying capacity. The main contents are as follows:(1) The total potential energy of stiffened cylindrical shells is divided into constant term,linear term and square nonlinear term. It's explicit that the nonlinear term of total potential energy affects the stability load of cylindrical shell. Then the stiffness reduction method is applied in studying the effect of each stifness on stability load-carrying of cylindrical shells by dividing nonlinear total potential energy into membrane stiffness, bending stiffness and geometry stiffness which affected by external forces.(2) The buckling load calculation formula of cylindrical shells with axisymmetric initial imperfection is derived by building the geometrical equations of cylindrical shells with axisymmetric initial imperfection. The effects laws of axisymmetric initial imperfection on shell stability and general stability of stiffened cylindrical shells are analyzed while structural parameters are change. The formula to calculate membrane stiffness reduced coefficient and spectrogram of cylindrical shells with axisymmetric initial imperfection is given out by studying the effect mechanism of axisymmetric initial imperfection on stability of cylindrical shells.(3) The cylindrical shells with local initial dents are divided into local dent parts and complete parts. The formula to calculate critical buckling load of cylindrical shells with local dents is derived by applying geometrical equations of cylindrical shells with axisymmetric initial imperfection in local dent parts. The effects of local dents on shell stability and general stability of stiffened cylindrical shells are analyzed while structural parameters and dents parameter are change. The formula to calculate membrane stiffness reduced coefficient and spectrogram of cylindrical shells with local dents is given out by studying the effect mechanism of local dents on stability of cylindrical shells.(4) The geometrical equations of cylindrical shells with buckling wave initial imperfection are built according to thin shell theory and the formula to calculate the buckling load is derived. The effects of non-axisymmetric initial imperfection on shell stability and general stability of stiffened cylindrical shells are studied while structural parameters are change. The formula to calculate membrane stiffness reduced coefficient and spectrogram of cylindrical shells with non-axisymmetric initial imperfection is given out by studying the effect mechanism of non-axisymmetric initial imperfection on stability of cylindrical shells.The comparison of buckling load of cylindrical shells with non-axisymmetric initial imperfection calculated by the formula in this paper with rules and tests is conducted to verify the reliability and practicability of the methods in this paper.