Modeling of Bonnet for Pedestrian Research in LS-DYNA

Pedestrians are the most vulnerable road users and crash statistics implies that continuous efforts are needed to reduce the causalities and mitigate their effects; both in passive and active safety. Current thesis is an attempt to provide a FE model which can be utilized for the analysis of the pedestrian kinematics. The author has focused on the bonnet modeling in LS-DYNA; furthermore, the modeling task was developed to provide the model of other influencing components in vehicle’s front end namely: fenders, engine cover, battery cover and frame. Through the use of GeoMagic studio, CATIA, HyperMesh, LS-Prepost and LS-DYNA, the FE models of all previously cited parts are prepared respectively. To investigate the response of the model to head and torso impacts, Euro-NCAP Head-form impacts tests were simulated and the responses evaluated. Also a FE model of a rigid torso impactor is modeled in LS-DYNA based on a mechanical torso impactor designed at Autoliv and the simulation results were compared and evaluated with the impact tests performed at Autoliv. A first investigation deals with the response of the bonnet when exposed to different loads at different positions on the bonnet. It was found that the kinematics was influenced mainly by the stiffness of the collision point and particularly if the rigid parts were engaged in the impact and the size of the gap between the hood and the rigid components. A second study involves the comparison between the results of available experiments and those obtained in reconstruction of these experiments. Despite showing comparable peak acceleration and impact duration, the results indicated a significant discrepancy in terms of the shape and slope at the beginning of the impact. Finally, through the use of a parametric study, the effects of thickness, material, positioning tolerance, velocity tolerance, impactor angle and control shell part were investigated.