Optimum crashworthiness design of tapered thin-walled tubes with lateral circular cutouts

In this paper, the effects of introducing lateral circular cutouts on crash performances of tapered thin-walled tubes are explored within a simulation-driven surrogate-based multi-objective optimization framework. The crash performances of the tubes are measured using the crush force efficiency (CFE) and the specific energy absorption (SEA) criteria, which are computed using the finite element analysis code LS-DYNA. Surrogate-based optimization approach is followed to find out that optimum values of the wall thickness, the taper angle, the cutout diameter and the numbers of cutouts in horizontal and vertical directions to maximize CFE and SEA. Four different surrogate models are used: polynomial response surfaces, radial basis functions, and Kriging models with zeroth- and first-order trend models. It is found that the optimum CFE of the tubes with lateral circular cutouts is 27.4% larger than the optimum CFE of the tubes without cutouts. It is also found that the optimum SEA of the tubes with lateral circular cutouts is 26.4% larger than the optimum SEA of the tubes without cutouts. It is observed that the optimum SEA design has slightly reduced wall thickness, significantly reduced taper angle, significantly increased cutout diameter, increased number of cutouts in horizontal direction and slightly reduced number of cutouts in vertical direction compared to the optimum CFE design. In addition, multi-objective optimization of the tubes is performed by maximizing a composite objective function that provides a compromise between CFE and SEA. It is found that the CFE dominates the behavior of composite objective function.