ROBUST DESIGN CRITERION FOR AXIALLY LOADED CYLINDRICAL SHELLS – SIMULATION AND VALIDATION

A currently used guideline for cylinder structures under axial compression is the NASA SP-8007 which is based on empirical data from the 1960s. This guideline provides knock-down factors (KDF) for the lower bound of the buckling load which depend on the cylinder radius-to-thickness ratio but neglect the influence of the cylinder length L. Experimental results indicated an influence of the cylinder length on the buckling load but a clear dependency could not be established because of the insufficient amount of available data. A comprehensive numerical investigation was performed in order to study the influence of length effect on the lower bound of the buckling load. The numerical analysis is based on the single boundary perturbation approach (SBPA) for cylindrical shells. The results verify that there is a significant influence of the cylinder length L on the lower bound of the buckling load. Semi-analytic knock-down factors for the stability failure of axially loaded cylindrical shells were determined which can be used for a simple and fast approximation of the lower bound of the buckling load. The corresponding SBPA thresholds were validated with a number of high fidelity buckling experiments and deliver much higher KDFs than currently used empirical guidelines.