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Deep-sea structures face extreme pressures and manufacturing defects, creating complex uncertainties in design. This study presents a reliability-based approach to evaluate the critical buckling load and safety factors for a Ti-6Al-4V ELI pressure-resistant spherical shell at 5000 meters depth. A bilinear material model, based on tensile testing, captures the shell's plastic behavior, and a first-order linear buckling mode with 0.3% of the inner diameter is considered as the initial imperfection. The Average Conditional Exceedance Rate (ACER) method, combined with nonlinear finite element analysis, is used to predict critical buckling loads over probability levels from 10−1 to 10−7. Results show that ACER provides accurate load estimation and 95% confidence intervals, even with limited data, aiding the selection of safety factors. Integrating these reliability analysis results early in the design phase helps avoid overly conservative or insufficient designs, enhancing the safety and cost-effectiveness of deep-sea pressure hulls.HighlightsThe critical buckling load of titanium alloy deep-sea pressure spheres under nonlinear conditions using the ACER method for reverse extreme value prediction;Different safety margins are evaluated with incorporating dispersion of material properties to provide reference in the design process.
Li et al. (Thu,) studied this question.