Pedestrian Head Impact Research Articles

Crack analysis in PVB laminated windshield impacted by pedestrian head in traffic accident

A damage-modified nonlinear viscoelastic constitutive relations model of PVB laminated windshield is suggested based on updated Lagrangian method to study the crack evolutions on windshield plate subject to pedestrian head. After verified by a classical example, the constitutive relations are implemented into FEA software. With proper material properties, the FEA model describing the pedestrian head impact with vehicle windshield in traffic accident is established. The computation results of FEA model and classical Hertzian pressure model are in good agreement. Moreover, the FEA model is used to analyse the internal stresses. Shear stress, compressive stress and tensile stress are main causes of plastic deformation, radial cracks and circumferential cracks, respectively. Internal stresses decrease as the distance away from the impacted point increases. In addition, parametric studies were carried out to study the effects of Poisson's ratio and impact velocity.

Reconstruction model of vehicle impact speed in pedestrian–vehicle accident

Reconstruction of pedestrian–vehicle accident is a worldwide problem. Numerous previous studies have been carried out on accidents with vehicular skid marks or definite pedestrian throw distances. However, little could be done if marks or throw distances cannot be obtained in accident reconstruction. This paper first describes the physical model of dynamic process of pedestrian head impact on windshield glazing. Some simplifications are made to obtain a better and more practical model, including discussing the support boundary conditions. Firstly, the paper modeled the relations between pedestrian impact speed and deflection of windshield glazing based on the impact dynamics and thin plate theory. Later, the relations of vehicle impact speed and deflection are discussed. Therefore, a model of vehicle impact speed versus deflection of windshield glazing is developed. The model is then verified by ten real-world accident cases to demonstrate its accuracy and reliability. This model provides investigators a new method to reconstruct pedestrian–vehicle accidents.

Optimization of single skin surfaces for head injury prevention – a comparison of optima calculated for global versus local injury thresholds

This paper describes optimizations of material properties for a bonnet-like plate using finite element calculations and the Euro-NCAP pedestrian head impact test. Four different head models were used for the impact simulations, a Euro-NCAP dummy head, a Hybrid III dummy head and two biomechanical head models exhibiting different mechanical properties for the brain tissue. The objective function was to minimize the displacement of the bonnet plate while satisfying constraints on the head injury criterion (HIC), the resultant contact force and, for the human head models, the strain in the brain tissue. An investigation was also conducted of the kinematics of the head models during impact, evaluating the energy distribution and the apparent mass. The analysis gave at hand that optimization of the plate with respect to impact with the Euro-NCAP and Hybrid III head models reached substantially different results compared to impact with the biomechanical head models. For the latter case, the stiffness of the brain tissue influenced which constraints were active in the final solution. The investigation of the kinematics at impact showed that a substantial portion of energy was confined within the brain during impact for the biomechanical head models. The apparent mass at impact coincided with the actual mass for the rigid dummy heads while for the human head models it was roughly the mass of the skull only.

Pedestrian Head Impact Conditions Depending on the Vehicle Front Shape and Its Construction--Full Model Simulation

For the evaluation of pedestrian protection, the European Enhanced Vehicle-Safety Committee Working Group 17 report is now commonly used. In the evaluation of head injuries, the report takes into account only the hood area of the vehicle. But recent pedestrian accident data has shown the injury source for head injury changing to the windshield and A-pillar from the hood. The head contact points are considered to fall on a parallel to the front shape of the vehicle along the lateral direction, but the rigidity of the outer side construction is different from the center area. The purpose of this study is to consider the reason for the change in injury source for recent vehicle models. The head contact points and contact conditions, speed and angle, are thought to be influenced not only by the vehicle's geometry, but also its construction (rigidity). In this study, vehicle-pedestrian impact simulations were calculated with a finite element model for several hitting positions, including the outer side areas. Full dummy sled tests were conducted to confirm the simulation results. These results show that, for impacts at the outer sides of the vehicle, the head contact points are more rearward than at the vehicle center. In addition, the speed and angle of the head contact were found to be influenced by the pedestrian height.