Energy absorption of metallic cylindrical shells with induced non-axisymmetric folding patterns

Metallic cylindrical shells are common structural elements. They can be used for controlled absorption of kinetic crash energy, e.g. in automobile and train structures. The energy absorption process of metallic shells subjected to axial loading is based on the formation of plastic folds. In order to optimise the energy absorption behaviour of such metallic cylindrical shell structures, the influence of different induced folding modes is investigated with the help of experiments as well as numerical finite element (FE) calculations and a simplified analytical model by Marsolekʹs Energieabsorptionsverhalten zylinderschalenförmiger Struktureiemente aus Metall und Faserverbundwerkstoff, dissertation. In quasi-static and dynamic tests a special load introduction device is used to induce non-axisymmetric folding patterns with different circumferential folding wave numbers. The load-deformation characteristics and the energy absorption capability resulting from different folding modes are compared. Explicit FE simulations using a fine mesh are performed. The simulation results are compared with the experimental results. The geometry of the trigger mechanism is optimised by varying the fraction of the shell circumference used for load introduction in FE simulations. In addition a simplified analytical model is developed, which is based on a detailed geometric idealisation of the folding process with stationary and moving plastic folds. It allows to predict the average crush force. The results of the analytical model confirm the tendencies found in experiments and FE simulations.