Dynamic energy barrier estimation for spherical shells under external pressure

Abstract

The energy barrier concept is developed for the case of dynamic loading of spherical shells. Simple semi-analytical formulae were obtained for the energy barrier for perfect shells and structures with geometrical imperfections. They were applied to the case of spatial step pressure to estimate dynamic buckling load of geometrically imperfect shells. It has been shown that dynamic effect can be caught properly by separating additional energy which causes local buckling of the shell. The calculated dynamic knockdown factor was in good agreement with numerical solution and experimental data. The methodology and formulae were also developed for the metastability estimation of real structure and for establishing knockdown factor taking into account possible external perturbations. The suggested approach improves current NASA (SP-8032, 1969) recommendations for design buckling pressure which are overly conservative.