Ph.D. Program in Mechanical Engineering.Sönmez, Fazıl Önder.Tanlak, Niyazi.2023-03-162023-03-162014.ME 2014 T36 PhDhttps://digitalarchive.library.bogazici.edu.tr/handle/123456789/15206Thin-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.30 cm.Thin-walled structures.xvi, 81 leaves ;