Buckling Load Prediction of Oblate Ellipsoidal Shells Using Force Stiffness Technique

Non-destructive evaluation techniques are increasingly applied to estimate the buckling load of shell structures without inducing failure. This study employs the force-stiffness (F-s) method to evaluate the buckling load of oblate ellipsoidal shells subjected to external pressure. Experiments on five steel shells with comparable R/t ratios are conducted, recording pressure, strains, and crown deflections up to failure. Using deflection data up to 80% of the buckling load, the F-s technique predicts buckling with ~90% accuracy, while incorporating crown strain data improves accuracy to ~95%. All shells fail within a pressure range of 2.7-3.4 MPa. The method is further validated on 3D-printed aluminum shells, showing promising consistency, though additional testing is required to refine accuracy. Finally, the F-s approach is demonstrated for real-time prediction of a large-scale shell, nearly three times larger than the experimental models, highlighting its scalability and potential for structural applications.