One of the main research lines in the automotive industry is safety, active and passive safety. Inside passive safety, development areas are body structure and the absorption energy process, the restraint systems, in adult occupant or referred to child restraint systems, and compatibility, against another vehicle or thinking about pedestrians.
Inside pedestrian protection, there are three different body regions to analyze. These regions are the head, adult and child head, the upper leg form and pelvis and, finally, the lower extremities.
Most of fatal injuries belong to the head anatomic region, but lower extremities are crucial because it is the first body region to contact to the vehicle. This contact between lower extremities and the vehicle can change the dynamic sequence of the rest of the body whilst the impact. It must be taken into account that these injuries require of a long recovery time and they condition people mobility.
Simulation models used in the automotive industry are becoming as a basic tool to develop new vehicle generations, reducing the development time and the time to market.
Main variables appearing in the pedestrian protection analyze that the vehicle can achieve are referred to the geometric configuration and to the materials that they parts are formed.
So, to improve the behaviour and the knowledge in the lower extremities pedestrian protection, three variables are used. These variables are the tibia acceleration, the knee bending and the shear displacement in the knee. The configuration of the front of the car is essential to introduce new and innovative solution in the new generation of vehicle, with the target to reduce injuries in pedestrian in case of accident.
Correlation indicators between results of the real model, the complete model and the simplified model created show that to obtain a basic simulation model is possible to analyse the influence of the geometric variables and the materials of the front of the car.
Nowadays front of vehicles configuration, the influence of the mechanic properties of the polymeric material of the front is reduced, because the main impact is between the lower extremities and the crossbeam, which is a metallic component and with a high stiffness.
Mathematical expressions obtained after analysing the simulation models and the configuration front matrix show that a mathematic model is possible to be obtained for each of the variables analyzed, corresponding to the acceleration, the knee bending and the shear displacement.
The validation analysis of the mathematic model has been done comparing the results of this simplified model with the results obtained in the laboratory with real vehicles. The correlation is accurate and there is a difference less than a 5% in the values of acceleration, knee bending and shear displacement.
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