AN ADVANCED METHODOLOGY FOR WINDSCREEN MODELLING IN LS DYNA

Laminated Safety Glass (Glass/PVB/Glass) is widely used for the automobile windscreens. Poly vinyl butaryl (PVB) placed in between two glass layers constructs the laminated glass. The very purpose of using the interlayer is to avoid separation of glass pieces after breakage and thereby reduce the possibility of injury to occupant and pedestrians. The stiffness of the windscreen plays vital role in roof crush, frontal impact and pedestrian load cases. Pedestrian load cases are inherent part of the EURO NCAP, KNCAP and JNCAP. Head Injury Criteria (HIC) value decides the rating of pedestrian load case. To perform head impact tests on windscreen is tedious task since it involves the replacement of the whole windscreen for each impact point. To avoid this and for the purpose of cost saving it is very important to develop the reliable windscreen failure methodology in CAE, to model the behavior of windscreens after impact. The present study is carried out on Ls-Dyna solver for pedestrian head impact on windscreen. Methodology for correlation of acceleration pulse is developed by using the material cards in Ls-Dyna. This new material card has the capability to handle tension and compression strengths differently. The propagation of crack in glass layers can be visualized and hence the crack pattern of the glass can be predicted. Glass laminates fails when the stress exceeds the maximum principle normal stress. The crack pattern in the region of impact becomes visible once the energy criteria is reached. PVB interlayer continues to provide stiffness after the impact. Head-form impacts are simulated at four locations of the windscreen and results are validated with test. The correlation activity is performed by monitoring the HIC values, pulse trend and crack pattern. Similar trend of acceleration pulse is obtained with the good agreement of first and second peaks with test