Shape optimization of thin-walled tubes under high-velocity axial and transverse impact loadings

Thin-walled tubes are one of the most commonly used parts in structural ap- plications. More specifically, they are used as passive safety measures in vehicles like bumper-beams and crash-boxes. They take loads either mainly in the axial direction or transverse direction. The objective of this study is to develop a design optimization methodology to maximize the crash-worthiness of such parts. The method is applied to obtain optimal shape designs of a bumper-beam and a crash-box. They are modeled under the loading conditions in standard EuroNCAP tests in which the vehicle hits a deformable barrier with 40% offset by 64 km/h speed. The crash event is simulated us- ing explicit finite element method. A lumped parameter model is developed to account for the structural response of the main vehicle body by a parametric system identi- fication method. The tubes are optimized by a hybrid search algorithm combining genetic algorithm and Nelder&Mead simplex search. The results indicate significant improvement in the crash-worthiness of the tubes.