Abstract: The front-end structure of a developing car was optimized to achieve the target of Flexible
Pedestrian Legform (Flex PLI) with a full mark of 6 score in a crash under the Euro-New Car Assessment
Program (Euro-NCAP). The energy-absorbing devices for front cross members and lower braced structures
were optimized using the Computer-Aided Engineering (CAE) technique. Soften-hole was widened to 35 mm,
and conduct-surface was added against press-break for energy-absorbing devices. Two connective structures
were removed from lower braced structures. The thickness oflower braced structures was reduced to 0.8 mm.
The result shows that the absorbers perform better in deformation, and absorb 22 kJ more. The tibia-mid upper
bending moment is reduced by 106 Nm. With the work of lower support, the middle part of legform moves 25
mm more in X direction while the bottom of legform moves 15 mm less in X direction, and reduces the medial
collateral ligament elongation by 17.8 mm. Therefore, a full mark 6 is obtained.

Key words: vehicle safety, pedestrian protection, flexible pedestrian legform (Flex PLI), front-end structure, optimization design, Euro-New car assessment program (Euro-NCAP)