Stochastic Simulation of the Head Impact on Windscreens

Summary

In accidents involving cars with pedestrians, the impact of the head on structural parts of the vehicle takes a significant risk of injury. If the head hits the windscreen, the injury is highly influenced by glass fracture. In pedestrian protection tests, a head impactor is shot on the windscreen while the resultant acceleration at the COG of the head is measured. To assess the risk of fatal or serious injury, a head injury criterion (HIC) as an explicit function of the measured acceleration can be determined. The braking strength of glass which has a major impact on the head acceleration, however, is not deterministic but depends on production-related micro-cracks on the glass surface as well as on the loading rate. The aim of the present paper is to show a pragmatic method, how to include the stochastic failure of glass in crash and impact simulations. The methodology includes a fracture mechanical model for the strain rate-dependent failure of glass, the experimental determination of the glass strength for the different areas of a windscreen (surface, edge, and screen-printing area), the statistical evaluation of the experimental data and the computation of a HIC probability distribution by stochastic simulation.

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