A Study On Head-Brain Dynamic Responses And Protections Of Pedestrians In Vehicle-Pedestrian Collisions

Pedestrians are the most vulnerable road users, and frequently involved in vehicle traffic accidences. The head-brain injuries in vehicle-pedestrian collisions account for 30% of all reported injuries on different body regions, which often resulted in a fatal consequence. And such injuries can result in disabilities and inparements, which lead to significant social costs."How to make Pedestrians more safer"has become an issue with worldwide concern.The aim of this thesis is to simulate the dynamic responses and biomechanical responses using a vehicle-pedestrian impact mathematic model, to analyse the influences of vehicle speed, stiffness and dimension of front structure to pedestrian head-brain injuries, and to discuss the means of pedestrian protection from vehicle collisions.The studies of pedestrian safety have been widely carried out using different approaches,including full scale dummy tests, cadaver tests, accident reconstructions, analysis of accident data and computer simulations. In this study the vehicle-pedestrian impact model was developed using multi-body program MADYMO. The pedestrian was simulated using the Chalmers Pedestrian 50% Male Adult Model, the passenger car model was developed based on the front geometry of a production car. The mechanical property of the car model was defined based on results from EuroNCAP dynamic tests. Factorial test method was adopted in this thesis, to analyse the influences of passenger car front structures and stiffness on pedestrian head-brain injuries. In the parameter study the car frontal geometry and stiffness was defined based a reference to passenger vehicles produced in different countries at impact speeds of 20, 30, 40, and 50 km/hThe results from this study were analyzed and discussed in terms of injury mechanism. The result turned out to be of that: first of all, vehicle speed had the significant influence to head-brain injuries, it would lead fatal injuries when the speed exceed 40km/h; Secondly, stiffnesses of car front parts also affected the level of head-brain injury, and properly reducing the stiffnesses had the benefits of improving head protection; Thirdly, the height of bonnet leading edge was also important to pedestrian head-brain injuries, and other dimension parameters, more or less, had relationships to the outputs.This study provided an effective approach and simulation models for research on injury biomechanics and development of safer vehicle for pedestrian protection.