Access Type

Open Access Dissertation

Date of Award

January 2014

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Mechanical Engineering

First Advisor

King H. Yang

Second Advisor

Trilochan Singh

Abstract

Current regulations for assessing pedestrian safety use a simplified test setup that ignores many real-world factors. In particular, the level of protection is assessed using a free-motion headform impacting the vehicle's hood at a fixed angle. As such, this test setup does not capture the effect due to the vehicle front-end profile, nor does it comprehend injury due to a possible secondary impact of the pedestrian's head with ground. This thesis aims to numerically simulate vehicle to pedestrian crashes to develop knowledge that may suggest ways to improve safety above and beyond the regulatory tests. Inputs to the simulations include the vehicle front-end profile, impact speed, and pedestrian size. Outputs include the angle of primary head impact to the hood, the extent of head injury (HIC), and whether or not there is a secondary head impact with the ground.

One key finding is that head impact angles, and hence head injury measures, vary greatly due to changes in vehicle front-end profile. This suggests that the current test setup for assessing pedestrian head impact, which assumes a fixed head-impact angle, could be improved to better capture the kinematics of real-world pedestrian crash events. One improvement could be the use of a full scale pedestrian dummy or human body model rather than a free motion headform. A second finding is that severity of head injury is much greater in a secondary head impact with ground than in the primary impact with the hood. Moreover, it is possible to avoid the secondary head impact with ground by careful designing of vehicle front-end profile. More research needs to be carried out to prove that concepts developed through numerical simulations also works in physical tests.

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