Vehicle Bumper System Optimization

Topology optimization of a vehicle bumper system to improve design

Project Sponsor: Honda R&D Americas

Figure 1: The defined load cases from left to right: center, upper, lower

Figure 2: Topology results for single case optimization: Center, upper, and lower load cases

Figure 3: Evolution of the topology using multiple load cases and increased mass fraction.

Topology optimization of vehicle bodies for crashworthiness has historically been a difficult challenge. This study examined a vehicle's bumper system. An effective bumper design reduces the possibility that expensive and vital vehicle components will be damaged in a low-speed collision.

There are other factors that must be taken into account in the bumper design. A heavy system worsens gas mileage and causes higher vehicle emissions, and excess material increases manufacturing costs.

Digitally optimizing a bumper system helps to design a bumper that performs well in all conditions while still meeting other design criteria.

Single and Multiple Load Case Optimizations

Figure 4: CAD geometry was swept along the same profile as the reference model

Three load cases were defined using LS-DYNA explicit solver (Figure 1). These three load cases included a center load, an upper load and a lower load. The center load simulated a flat crush mode, such as if the vehicle collided with a solid wall or another vehicle with the same ride height. The upper and lower loads simulated the vehicle colliding with another vehicle that has a different ride height. These designs and are shown in Figure 2.

Each design performed well in its own load case. However, since each design only considers one load case, their performance was inadequate when subjected to other load cases.

Bumper systems are subjected to multiple forces at once in real-world collisions, so the three designs from the single load case optimizations were combined to create a bumper that performs well in all load cases (Figure 3).

Testing the Final Design

The final step was to generate a CAD geometry from the topology result. This cross-section was then swept along the same profile as the reference model (Figure 4). The design was subjected to the center, upper and lower load cases mentioned above, and an improvement in performance was noted for each load case. The optimized design absorbed more energy and deformed less than the reference design (Figure 5). Additionally, the optimized design weighed only 0.02 kilograms more than the reference design, so the vehicle's fuel economy and emissions were hardly affected.

Figure 5: The new design (right) performed better than the reference design (left) in this simulated collision.

Project Contributors
Emily Nutwell
Satchit Ramnath
Nikola Aulig
Duane Detwiler

More information and data for this project can be found here.