Development of a Biofidelic 'Legform' Impact Test Device

Current EuroNCAP test specifications attempt to predict pedestrian lower limb injury in a lateral impact with a rigid legform test device developed by the UK's TRL (Transportation Research Lab). Research shows that the measurements taken from this device (knee bending angle, knee shear, and upper tibia acceleration) do not necessarily correspond to accurate injury prediction. Recent research suggests that the primary improvement to the current test device would be a flexible legform, or one that has more biofidelity (i.e., simulates actual human lower limb response). The work presented in this paper first reviews current legforms developed for pedestrian impact testing, including the TRL impactor used in EuroNCAP tests, Honda's POLAR II pedestrian dummy, and JAMNJARI's FLEX-PLI legform impactor. Component level testing shows the FLEX-PLI performance to be close to the human lower limb response corridors. However, there are still areas of potential improvement with this design. To address these areas, this research includes the phase 1 development of a new legform impactor incorporating adjustable ligament pre-load, direct ligament strain measurements, adjustability in knee flexion to account for the gait cycle, tuned composite bone cores that match the force-deflection curves of PMHS testing, and a condyle load plate that measures knee joint compressive forces. Development techniques include solid modeling, computer-aided manufacturing, composite design and analysis, sensor specifications, and data acquisition. In so doing, the injury specifications set by the EEVC will be modified to account for the more accurate injury assessment of the improved device.