Optimal shape design of thin-walled tubes under high-velocity axial impact loads

• Optimal shapes of crash-boxes are studied for maximum crashworthiness under axial impact loading.
• A lumped-mass model is developed to mimic the behavior of the main vehicle body.
• Energy absorbed by the deformable barrier is accounted for by a correction factor on vehicle mass.
• For different weighting factors in the objective function, different optimal shapes are obtained.
• Mass constraint does not become active.

In this study, the objective is to maximize the crashworthiness of thin-walled tubes under axial impact loads by shape optimization. As design variables, parameters defining the cross-sectional profile of the tube as well as parameters defining the longitudinal profile like the depths and lengths of the circumferential ribs and the taper angle are used. The methodology is applied to the design optimization of a crash-box supporting the bumper beam of a vehicle for the loading conditions in standard EuroNCAP crash tests. The crash event is simulated using explicit finite element method. While the crash-box is fully modeled, the structural response of the remaining parts during the tests is taken into account by developing a lumped-parameter model. A hybrid search algorithm combining Genetic and Nelder & Mead algorithms is developed. The results indicate significant improvement in the crashworthiness over the benchmarks designs.