Mechanical properties and optimal configurations of variable-curvature pressure hulls based on the equal-strength shell theory

Abstract

Cylindrical pressure hulls are widely used in deep-sea submersibles, but they are affected by limitations imposed by their mechanical characteristics. To improve the bearing capacity of pressure hulls, in this work, variable-curvature shells were proposed. Based on the membrane theory and the non-momental theory, expressions for calculating the stress and buckling load of variable-curvature shells were derived. The generalized equal-strength shell theory was taken as an important index to evaluate the bearing capacity of pressure hulls. Pressure hulls with different geometric configurations were analyzed through numerical simulations. Finally, cylindrical and circular variable-curvature shells were fabricated via additive manufacturing. Furthermore, a comparative experiment was carried out on the two types of shells. The results reveal that variable-curvature shells have better mechanical properties than cylindrical shells, which results in a lower stress in the two main directions and a higher buckling load. Additionally, variable-curvature shells are in better agreement with the equal-strength shell theory and ensure a high material utilization. The expressions for calculating the stress and buckling load in this study are found to be highly accurate.