An Analytical Method and Experimental Validation of Stress Concentration Factors (SCFs) of Spherical Hulls with Opening Reinforcements Under External Pressure

The presence of openings in spherical pressure hulls compromises the structural integrity and induces stress concentrations at the opening area. The strength assessment of shell openings remains a challenge in shell strength theory, even if using an approximated algorithm. While finite element analysis (FEA) is commonly employed, it is computationally prohibitive for iterative design. To address this gap, this study proposes a novel theoretical framework to calculate the Stress Concentration Factor (SCF) for spherical hulls with complex opening reinforcements under external pressure. A geometric transformation method based on the Equal Area Criterion (EAC) is established to convert complex reinforcement geometries into analytical forms. The accuracy is validated through comprehensive FEA and full-scale hydrostatic pressure tests on titanium-alloy manned hulls. The results demonstrate that the proposed method has high accuracy and exhibits excellent applicability, with deviations from experimental data generally within 5%. This study establishes a rapid assessment framework with high accuracy, providing a valuable engineering tool for deep-sea structural design.