A bumper model with dynamic contact stiffness for simulations of pedestrian legform impacts

Car-to-pedestrian accidents have become a global problem, and car manufacturers have made great efforts to redesign the car for pedestrian protection. For fast computer simulations of pedestrian legform-to-bumper impacts, which are usually needed for the large design-of-experiments matrix, quite a number of simplified bumper models have been built to represent detailed finite element models adopted from full-vehicle models. However, it has been a difficult balance between simplifying the structure to achieve fast computation and keeping the essential characteristics to obtain valid results. This paper documents a development and validation of a simplified bumper system model. The spring stiffness properties are determined by considering the loading rate effect and the local deformation effect of the vehicle’s front-end structure, which is essential for legform impact simulations. To validate the simplified bumper system model, the simulation results from the simplified bumper system model and from a detailed bumper system model are compared. This study also indicates that, to improve the responses of the legform bending and shear, the vehicle’s bumper should be modelled as two separate spring systems since the impact interaction is within the knee joint centre of the legform.

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