Objective  A spherical bulkhead with openings has many structural parameters, and it is time-consuming and laborious to directly use the finite element method to carry out parameter research. Therefore, a combined surrogate model method for predicting characteristic stresses is proposed.

  Method  The geometric characteristic parameters of an opening spherical bulkhead are extracted and used as design variables to construct a surrogate model for the characteristic stresses of a spherical bulkhead with a single opening. After analyzing the correlation between the characteristic stresses and structural parameters using the surrogate model, a combined surrogate model method with lower dimensions of design variables is proposed. The combined surrogate model consists of a surrogate model of characteristic stresses based on the parameters of a cylindrical-toroidal-spherical shell and a surrogate model of characteristic stress correction coefficients based on the opening fence parameters and thickness of the spherical shell.

  Results  The results show that the accuracy of the combined surrogate model is significantly improved due to the lower dimensions of design variables. Compared with the results of the directly constructed surrogate model, the maximum error and average error of the characteristic stresses are reduced by 4.96%–22.95% and 0.59%–5.43% respectively. The single-opening combination surrogate model is used to predict the characteristic stresses of a typical spherical bulkhead with multiple openings, and the prediction errors of the characteristic stresses are 0.12%–11.42%.

  Conclusion  The proposed combined surrogate model for the strength of a spherical bulkhead with a single opening can be used for the rapid prediction of the characteristic stresses of spherical bulkheads with multiple openings.