Elastic-plastic buckling of deep sea spherical pressure hulls

This paper focuses on the buckling of titanium alloy spherical pressure hulls subjected to uniform external pressure. Hulls were spherical shells with 1000 mm median radius and had uniform wall thickness of 25-80 mm. The linear and nonlinear buckling of geometrically perfect hulls were examined numerically and verified analytically in linear range. The nonlinear buckling of hulls with eigenmode geometrical imperfections were evaluated numerically using the modified Riks method, in which imperfection size ranged from 2 to 10 mm. The critical buckling load of geometrically perfect and imperfect hulls was obtained based on elastic-perfectly plastic material modelling, in which the yield strength varied from 800 to 1300 MPa. A semi-analytical formula to predict the load carrying capacity of hulls was derived based on the numerical computations, which was verified against previous laboratory experiments conducted years ago and numerical benchmark study. Results of analytical, numerical, and experimental investigations were given in tables and figures.