Quantifying the accuracy of numerical collapse predictions for the design of submarine pressure hulls

Abstract

An overview of current design practices for submarine pressure hulls is presented, along with the results of a survey of the literature that was conducted to determine standard nonlinear numerical modelling practices for those structures. The accuracies of the conventional submarine design formulae (SDF) and nonlinear numerical analyses for predicting pressure hull collapse are estimated by comparing predicted and experimental collapse loads from the literature. The conventional SDF are found to be accurate within approximately 20%, with 95% confidence, for intact pressure hulls. The accuracy of a wide range of nonlinear numerical methods, including axisymmetric finite difference and general shell finite element (FE) models, is found to be within approximately 16% with 95% confidence. The accuracy is found to be within 9% when only higher fidelity general shell FE models are considered. It is shown how the observations taken from the survey could serve as a starting point for establishing modelling guidelines, quantifying the accuracy of nonlinear FE analysis in pressure hull collapse calculations, and introducing this method into a design procedure by way of a partial safety factor.