The Influence of Shape Imperfections on the Stability of thin Spherical Shells

The main provisions of the numerical procedure for the study of nonlinear deformation and stability of thin spherical shells with simulated imperfections of their shape using the computational procedure of the finite element analysis software NASTRAN are formulated. The shell imperfections are modeled in the form of their stability loss with varying the maximum amplitude of imperfections using the developed software adapted to the NASTRAN complex. The nonlinear deformation and stability of a hemisphere and a spherical segment under the action of external surface pressure are investigated. The results of the analysis of the stability of spherical shells with different thicknesses and limit conditions in linear and nonlinear formulations are presented. The influence of imperfections on the pre-critical and post-critical stress-strain state of shells and the critical loading values are evaluated. It is shown that geometrical imperfections of thin spherical shells in the form of stability loss can lead to a decrease in the critical values of loading and change the forms of deformation.