Research On Pedestrian Head Protection Properties Of Laminated Glass By Numerical Simulation

Collision between the pedestrian head and the windscreen is a vital cause of injuries and death in traffic accidents.Improving the head protection properties of windscreens is a key question in the research field of pedestrian protection techniques.In this dissertation,based on Design of Experiments and statistical analysis,the influence of impact conditions and structure/material parameters of laminated glass on the head protection properties of laminated glass is studied by means of numerical simulation.The safety performance of PVB/SGP laminated glass is also compared and the important design parameters of laminated glass are optimized with safety performance and light weight as targets.The dynamic responses of the headform under different impact conditions are obtained by the tests of headform impacting PVB/SGP laminated glass,which provide the experimental basis for validating the numerical simulation model of laminated glass.The dynamic response characteristics of impacts between headforms and PVB/SGP laminated glass are compared and analyzed.Taking Head Injury Criteria?HIC?and headform 3ms resultant acceleration a_3ms as evaluation indexes,it is concluded that PVB laminated glass has better head protection properties when the headform vertically impacts the laminated glass center at a speed of 30 km/h.The modeling method of PVB/SGP laminated glass finite element models are discussed with the aspects of different element types and unit connection modes,mesh types and grid sizes,material models and failure criteria.The finite element models of PVB/SGP laminated glass are established by comparing with the experimental data under different impact conditions,which lays a foundation for the numerical study of the influence factors of laminated glass safety.HIC value and a_3ms are selected as the evaluation indexes of the head protection properties of laminated glass.The change rules of the head protection properties of laminated glass with impact velocities,impact angles and impact positions are studied by using control variable method.The influence mechanism of different impact conditions on the head protection properties is also described.The head protection properties of PVB laminated glass is better than that of SGP laminated glass in the range of impact conditions adopted in the dissertation.The significant degrees of influences of different laminated glass structure/material parameters on the head protection properties are ranked by main effect analysis and variance analysis,using the L₂₇(3¹³)orthogonal test with the headform HIC value serving as the evaluation index.The most significant factors affecting the safety performance of laminated glass are shown as follows:the thickness of the outer glass,the thickness of the inner glass,the maximum arch height in the vertical direction and the Young's modulus of the interlayer material.A quadratic polynomial statistical model describing the headform HIC value and the above mentioned four structure/material parameters is established by using the response surface center composite design,and the accuracy and reliability of the empirical model is verified.The influence laws of the four structure/material parameters on the head protection properties of laminated glass are also described considering the interation effects.The multi-objective optimization of the four structural/material parameters of laminated glass is conducted with safety performance and light weight as targets,which may shed light on the design criteria of pedestrian friendly windscreens.The results of this dissertation provide a reference for the numerical simulation method of the brittle-polymer laminated structure,and provide theoretical guidance for the development of the windscreen head protection technology for vulnerable road users.