Effect of Vehicle Front End Profile on Pedestrian Kinematics and Biomechanical Responses Using a Validated Numerical Model

Abstract

Traumatic injuries and biomechanical responses of a pedestrian depend on vehicle front end characteristics as well as the pedestrian anthropometric details in vehicle-pedestrian crashes. A number of laboratory experiments were conducted using post mortem human subjects (PMHS) to understand the biomechanics behind the injuries in a pedestrian crash. However, different vehicular front ends were used in these studies making comparisons among studies impossible. The current research work focuses on validating simulated pedestrian kinematics and accelerations responses of MADYMO full body pedestrian model with the experimental results. In general, overall kinematics of the body for pedestrian models were also compared with that recorded in the video snapshots from the cadaveric experimental tests at 50 ms time intervals. Along with the validation of kinematics of pedestrian, the acceleration responses of head, chest, pelvic and lower leg of the pedestrians were also validated against the corresponding experimental data. Other responses like head angle as well as head impact velocity during primary impact with the hood were analyzed at different impact speeds. Once the responses were validated for a particular front end of the vehicle, a series of numerical parametric studies were further conducted using several front end profiles based off a mid-sized sedan. For the parametric study, different pedestrian models representing three pedestrian sizes, a 50th male, a 5th female, and a 6 years-old child, were used in the simulations. Finite element model of a vehicle front end was changed in terms of the heights of bumper, bonnet leading-edge, and bonnet rear reference-line using a mesh-morphing technique. In most simulations, primary head impact location depends on the pedestrian size, and the secondary impact with ground at the head region is affected by type of vehicle and its front end profile. Kinematics of the pedestrians as well as the angle of primary head impact varies a great deal based upon the front-end profile of the striking vehicle (e.g., raised front-end profile or lowered front-end profile). Leg and pelvis accelerations were found to be high in vehicles with raised front end profiles. Chest and head accelerations were also found to be affected by vehicle front end profile and pedestrian size. However, it should be noted that there were some front-end profiles that help in avoiding pedestrian secondary head impact with the ground.