Technical Brief: Knockdown Factor for the Buckling of Spherical Shells Containing Large-Amplitude Geometric Defects

Abstract

We explore the effect of precisely defined geometric imper- fections on the buckling load of spherical shells under exter- nal pressure loading, using finite element analysis that was previously validated through precision experiments. Our nu- merical simulations focus on the limit of large amplitude de- fects and reveal a lower bound that depends solely on the shell radius to thickness ratio and the angular width of the defect. It is shown that, in the large amplitude limit, the buck- ling load depends on an single geometric parameter, even for shells of moderate radius to thickness ratio. Moreover, nu- merical results on the knockdown factor are fitted to an em- pirical, albeit general, functional form that may be used as robust design guideline for the critical buckling conditions of pressurized spherical shells.