Enhancing material efficiency of energy absorbers through graded thickness structures

• A graded thickness tube along axial direction is introduced.
• The gradient exponent has a direct effect on controlling the absorbed-energy.
• The graded column is superior to the uniform thickness column.
• A comparative study on different surrogate models is conducted.

At present, there has been constant aspiration of advanced thin-walled structures in vehicular industries for more efficient usage of materials to achieve much lighter weight and even higher energy absorption. In this paper, functionally graded thickness (FGT) tubes with a varying wall thickness are introduced and their energy-absorbing efficiency is enhanced. Apart from the geometrical parameters such as diameter and length, the gradient exponent that controls the variation of thickness distributions has also a significant effect on the increase in absorbed-energy. Numerical model is validated by performed crashing experiments of FGT tube. Parametric analysis demonstrates that the FGT column is superior to the uniform thickness (UT) column. Further, the multiobjective optimization (MOO) of FGT tubes is conducted for axial impacting by considering specific energy absorption (SEA) and crashing force efficiency (CFE) as objectives, and the diameter, initial length and gradient exponent of thickness variation as the design variables. The multiobjective particle swarm optimization algorithm (MOPSO) is applied to obtain the Pareto optimal solutions. In addition, a comparative study on different surrogate models, such as response surface method (RSM), Kriging method (KRM), and radial basis function (RBF), is also carried out to gain insights into their relative performance and features in computational modeling and design optimization. It is indicated that the performance of FGT tubes can be significantly improved by optimizing the geometrical parameters and gradient exponent.