Development and Validation of Sedan Pedestrian Bucks Using Finite Element Simulations: Application in Study the Influence of Vehicle Automatic Braking on the Kinematics of the Pedestrian Involved in Vehicle Collisions

Previous vehicle-to-pedestrian simulations and experiments using pedestrian dummies and cadavers have shown that factors such as vehicle shape, pedestrian anthropometry and pre-impact conditions influence pedestrian kinematics and injury mechanisms. Generic pedestrian bucks, that approximate the geometrical and stiffness properties of current vehicles, would be useful in studying the influence of vehicle front end structures on pedestrian kinematics and loading. This study explores the design of pedestrian bucks, intended to represent the basic vehicle front-end structures, consisting of five components: lower stiffener, bumper, hood leading edge and grille, hood and windshield. The deformable parts of the bucks were designed using types of currently manufactured materials, which allow manufacturing the bucks in the future. The geometry of pedestrian bucks was approximated based on the contour cross-sections of two sedan vehicles used in previous pedestrian dummy and cadaver tests. Other cross-sectional dimensions and the stiffness of the buck components were determined by parameter identification using FE simulations of each sedan vehicle. In the absence of a validated FE model of human, the FE model of the POLAR II pedestrian dummy was used to validate a mid-size sedan (MS) pedestrian buck. A good correlation of the pedestrian dummy kinematics and contact forces obtained in dummy - MS pedestrian buck with the corresponding data from dummy - MS vehicle simulation was achieved. A parametric study using the POLAR II FE model and different buck models: a MS buck and a large-size sedan (LS) buck were run to study the influence of an automatic braking system for reducing the pedestrian injuries. The vehicle braking conditions showed reductions in the relative velocity of the head to the vehicle and increases in the time of head impact and in the wrap-around-distances (WAD) to primary head contact. The head impact velocity showed greater sensitivity to the different buck shapes (e.g., LS buck vs. MS buck) than to the braking deceleration. The buck FE models developed in this study are expected to be used in sensitivity and optimization studies for development of new pedestrian protection systems. The full text of this paper may be found at: http://www-nrd.nhtsa.dot.gov/pdf/esv/esv21/09-0485.pdf For the covering abstract see ITRD E145407.

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