Investigation of the effect of density of expanded polypropylene bumper filling on pedestrian collision performance by finite element method

Bumper energy absorber lays between bumper and crush box in vehicles. It is described as a passive safety structure that absorbs the energy conducted by the bumper during the crash. Although they are very efficient at low-speed crushes such that pedestrian-involved or parking accidents, their effectiveness is neglected at high-speed crushes as they can absorb energy less than significant. In this study, bumper energy absorber is examined through computer-associated simulations to investigate the effect of different material densities of bumper energy absorber on pedestrian-involved accidents. For this reason, the points of contact of a pedestrian are determined as rigid square, and cylindrical, separately. Also, the crush is arranged as if the point of contact is at the middle and quarter part of the bumper of a vehicle. The simulation result shows that the force acting on the pedestrian increases with respect to an increase in the density of the bumper energy absorber because even in low-speed crushes, the bumper deforms to the point where it reaches the energy absorber structure. Moreover, the bumper energy absorber is directly involved in the center collision thanks to its natural design shape. On the other hand, before the bumper energy absorber involves the collusion, the bumper involves the collusion directly and creates the reaction force.