Multiobjective crashworthiness optimization of multi-cornered thin-walled sheet metal members

• The collapse behavior of square, hexagonal, octagonal, and newly introduced 12-edge section for stable collapse with high energy absorption capacity was characterized. This newly introduced 12-edge configuration was developed based on the idea of distributing more materials near the corner by introducing more corners in the cross-section.
• Design of experiments (DOE) based on Taguchi method along with CAE simulations was performed to evaluate the responses over a range of steels grades.
• Multiobjective optimization with the target of maximizing both specific energy absorption (SEA) and crush force efficiency (CFE), was carried out by nonlinear finite element analysis through LS-DYNA.
• Rank orders and the contribution percentage of each design factor (i.e. cross-sectional contribution, material type and wall thickness) on the SEA and CFE values were calculated.
• A clear comparison of the SEA and CFE values for different cross sections, material types, and wall thicknesses was presented and the patterns were extracted.

Plastic deformation of structures absorbs substantial kinetic energy when impact occurs. Therefore, energy-absorbing components have been extensively used in structural designs to intentionally absorb a large portion of crash energy. On the other hand, high peak crushing force, especially with regard to mean crushing force, may lead to a certain extent and indicate the risk of structural integrity. Thus, maximizing energy absorption and minimizing peak to mean force ratio by seeking for the optimal design of these components are of great significance. Along with this analysis, the collapse behavior of square, hexagonal, and octagonal cross-sections as the baseline for designing a newly introduced 12-edge section for stable collapse with high energy absorption capacity was characterized. Inherent dissipation of the energy from severe deformations at the corners of a section under axial collapse formed the basis of this study, in which multi-cornered thin-walled sections was focused on. Sampling designs of the sections using design of experiments (DOE) based on Taguchi method along with CAE simulations was performed to evaluate the responses over a range of steels grades starting from low end mild steels to high end strength. The optimization process with the target of maximizing both specific energy absorption (SEA) and crush force efficiency (CFE), as the ratio of mean crushing load to peak load, was carried out by nonlinear finite element analysis through LS-DYNA. Based on single-objective and multi-objective optimizations, it was found that octagonal and 12-edge sections had the best crashworthiness performance in terms of maximum SEA and CFE.