Discrepancy between boundary conditions and load introduction of full-scale built-in and sub-scale experimental shell structures of space launcher vehicles

• Highlighting the importance of built-in boundary conditions.
• Performing numerical load controlled shell buckling analyses.
• Considering three different types of localized perturbations of shells.
• Emphasizing that buckling tests may overestimate load carrying capacity.

Shell buckling experiments are mostly conducted in a displacement controlled manner, that is the displacement at the loaded shell edge is increased and the load applied is measured as reaction force. The corresponding boundary conditions are realized by potting the shell edges. Real shell structures, such as primary structures of space launcher vehicles, are loaded in a load controlled manner and boundary conditions are defined by the adjacent structures and stiffening rings. Within this contribution, the discrepancy between boundary conditions and load introduction of full-scale built-in and sub-scale experimental shell structures of space launcher vehicles is studied numerically. For this purpose, dynamic explicit load controlled buckling analyses were performed using theoretical boundary conditions to idealize built-in conditions in an extreme manner and taking localized perturbations, such as those due to a single perturbation load, geometrical dimple imperfections and circular unreinforced cut outs, into account. The results are compared to displacement controlled shell buckling predictions in which boundary conditions commonly used within shell buckling experiments of sub-scale structures are taken into account.