Buckling of externally pressurised egg-shaped shells with variable and constant wall thicknesses

This study focused on the nonlinear elastic buckling of mass equivalent egg-shaped shells with variable and constant wall thicknesses under uniform external pressure. The shells were made of photosensitive resin and had a nominal mass of 570 g, a nominal major axis of 260.36 mm, and a nominal minor axis of 181.32 mm. Four egg shaped shells were fabricated using the aforementioned parameters and using the rapid prototype technique stereo lithography appearance. Two shells had a constant wall thickness, whereas the remaining shells had a variable wall thickness along the meridian. The geometry of all shells was accurately measured, and the shells were slowly pressurised to destruction, thus yielding good repeatability. On the basis of the measured results, the buckling performance of the tested shells was further studied numerically. The experimental data were found to be in agreement with the numerical predictions. The results revealed that the average collapse pressure for the egg-shaped shells with variable wall thickness was approximately 24% higher than that for the egg-shaped shells with constant wall thickness, thus indicating that the load-carrying capacity of the egg-shaped shells was significantly improved when variable thickness was used.