The Optimization Of Vehicle Front-end Structure Based On Pedestrian Legform Protection

The car ownership in China has been on the rise,but China has a large population,the road traffic has become chaotic,which increases the probability of pedestrian colli-sion.Generally speaking,when the pedestrian-vehicle collision happen,the leg collides vehicle front-end structure firstly,the pedestrian leg is the riskier part to be injured in an collision accident,the front-end structure of the vehicle is the main factor affecting the protection performance of the lower limbs.This paper uses the finite element simulation analysis method to perform the front-end structure optimization of a car for good leg protection performance by using foam and honeycomb aluminum structure.In this paper,the finite element collision model of vehicle simplification model and rigid leg was established in Hypermesh,and then the LS DYNA software was used to solve the calculation.By analyzing the curves of the total energy and quality,the accu-racy of the finite element model was validated.The comparison between the simulation results of the pedestrian leg injury and the regulation threshold found that the passenger leg protection performance was poor,the tibia acceleration of Y₀ and Y₃₉₀ exceeded the safety threshold,the front-end structure was needed to be optimized.Paper introduced 3 different section of the EPP foam endergonic structure and simulation calculation was carried out respectively,the best section of EPP foam was chosen for the pedestrian leg protection effect.On the basis of this section,three foam densities were selected to simulate the performance of pedestrian leg protection of vehi-cle front-end structure in Y₀ and Y₃₉₀ position.The results showed that the effect of the optimized foam absorption structure on the protection of pedestrian leg was improved than original vehicle,but the tibia acceleration and knee bend angle peak value were more than the regulation threshold in Y₃₉₀ positon,it is necessary to introduce a more efficient cushioned structure to improve the performance of pedestrian leg protection.According to the size of the front energy absorption space,paper finally designed the 6 kinds of different lengths cell of honeycomb aluminum structure,and then 5 kinds of different thickness were given to each honeycomb structure to complete 30 groups of full-scale simulation experiment,through the analysis results of 30 groups correspond-ing to the pedestrian leg injury value in Y₀ position,the honeycomb structure with a border length of 14mm was determined because of the best pedestrian leg protection effect.On the basis of this honeycomb structure,the thickness of the front cover plate and core of honeycomb structure were used as the optimization variables,the optimiza-tion simulation and validation were carried out to minimize the MSE value in Y₃₉₀ posi-tion.Comparision of three leg injury indexes between optimized model and the original car indicated that the three indicators of pedestrian leg injury after optimization dropped sharply,the MSE value dropped from 1.794 to 0.348.In Y₀ collision position,the three indicators of pedestrian leg injury after optimization were lower than the safety thresh-old requirements,besides,the composite damage index MSE dropped from 0.518 to0.326.The design optimization of honeycomb aluminum endergonic structure greatly improved the pedestrian leg protection performance of the vehicle front-end structure.