Crashworthiness and lightweight optimization to applied multiple materials and foam-filled front end structure of auto-body

Auto-body's front end structure, such as bumper and crash box, has the vital function of protecting other components from damage during low-velocity collision; moreover, it should accomplish excellent lightweight effect under the insurance of crashworthiness. This article combined the two approaches of lightweight improvement that listed as using structural optimization and replacing original materials with high strength and high mass efficiency materials or employing reinforced materials to conduct the crashworthiness optimization of assembly of bumper, crash box, and front rail. The original materials of bumper, crash box, and front rail were replaced by aluminum alloy 6060, TRIP800, and DP800, respectively. Aluminum foam was filled in bumper to replace the original reinforced plate and also was filled in crash box to increase energy absorption. The comparisons were made between an optimal selection from the multiple materials designs and the single material design. During optimization, crashworthiness criteria were defined as constraint conditions, and response surface surrogate model and genetic algorithm with elite strategy were employed to solve mathematical model of minimum mass. In single material optimization, the result already achieved the energy absorption increased by 10.1%, the peak collision force and the crumple distance decreased by 11.1% and 12.6%, respectively, and the total mass decreased by 11.1%. As for multiple materials optimization, the results obtained further optimal values. It is found that foam-filled bumper can overcome the disadvantage of bumper mid-bending that causes bumper failure of load bearing, and foam filler has the interaction effect with crash box as well, through which it received a significant growth of energy absorption. The application of multiple materials design greatly expands the potential of crashworthiness and lightweight optimization.