Research On Windscreen Crack Characteritics In Pedestrian-vehicle Traffic Accidents

Pedestrians are typically vulnerable road users and stay a high injury and mortality rate among all kinds of accidents. Therefore pedestrian protection is gradually becoming an important element during the process of vehicle development. Our nation formulated the national standard "car’s impact protection for pedestrian" in 2009 as a recommended standard to use which shows that we also has accelerated the pace of study of pedestrian protection. Windscreens as major automotive parts that pedestrian head contact, its absorption behavior and failure modes are of significance for pedestrian protection and accident reconstruction. So this article mainly analyzed the dynamic impact characteristic of a certain windscreen through experiments and simulations and especially numerical studied the simulation methods and crack propagation characteristic of windscreen.Based on the national standard "car’s impact protection for pedestrian", a head impactor was designed and its three-dimensional model was built. In the coupled environment of HYPERMESH and LS-DYNA, this paper established the hexahedral finite element model of the head impactor. The material parameters of the artificial scalp were determined after repeatedly simulated experiments. Combining EEVC regulations, dynamic drop test and side impact test were carried out which results verified the effectiveness and biological response fidelity of the head impactor. And at the side impact test, the suspended angle and coaxial degree’s effect on the impact experiment were analyzed.This paper set up a test bed for the experiment that head impactor impacts windscreen. The motion characteristics and acceleration of the head impactor,crack propagation characteristics of windshield were studied.Learning different mechanics model of PVB interlayer, integrating modeling methods, this paper established four type windscreen finite element models of single layer, double layers and triple layers based on viscoelastic and elastic-plastic PVB interlayer. Comparing the acceleration/time histories of four models with the experimental curve, it was found that two-layer structure model can better agree with the experimental results.The finite element model was established of the head impactor impacting the windscreen. Factors that might affect the crack morphology were analyzed. The effect of impact angle, impact collision position, the collision speed and PVB interlayer thickness on the crack shape, the radius of the maximum ring crack and pedestrian head injury HIC values were explored. Based on mathematical regression analysis, the correlation between collision speed and maximum annular crack radius was established of glass edge point, corner and center.