Bending Collapse Mechanism And Crashworthiness Optimization Of Bumper Beam System Under Lateral Loading

In recent years,with the increase of per capita consumption,car ownership increases year by year.There are more and more traffic accidents.The world’s increasing emphasis on automobile collision safety.When a non-fatal low-speed collision occurs in real life,the good performance of the bumper assembly is not only reflected in the maximum absorption of kinetic energy,but also to protect the safety of vehicle occupants and pedestrians minimizing damage to vulnerable parts of the vehicle front.This study mainly discusses the dynamic bending mechanism and the optimization design of the bumper assembly.The specific work is as follows:(1)According to the bending conditions of the bumper assembly,a foam-filled enhanced structure is proposed,to analysis mechanism under dynamic bending load.Firstly,the simulation model is constructed and verified by experiments.Then,by observing the simulation model and experimental deformation,it is found that the foam filled structure can effectively improve the bending property during the deformation process,and induce the plastic deformation of the bumper assembly.At the same time,a simplified bending deformation model of the double-cap thin-walled beam filled with foam aluminum was proposed,and the deformation analytical modeling is carried out.The results show that,under a small indentation displacement,the theoretical energy absorption displacement curve is consistent with the finite element results.Finally,the practicability of the theoretical model is verified under different upper and lower cap height ratios.The results show that when the upper and lower caps are asymmetric,the energy absorption displacement curve derived from the theory is consistent with the simulation results.which can provide a preliminary solution for the energy absorption prediction of the bumper assembly under lateral loading.(2)Aiming at the different collision forms in the frontal collision of the car,three common collision scenarios was adopted to establish a finite element simulation model based on the current test conditions,namely,the trolley 100% rigid wall collision,dynamic three-point bending and 40% offset collision,and verified the accuracy of the finite element model through experiments.Then,a parallel high-efficiency global optimization algorithm based on the "Kriging Believer" strategy was used to perform multi-objective optimization for each working condition,and the difference of optimization solutions under different working conditions was analyzed.A weighting method was proposed to optimize the design of multiple working conditions,and the weight distribution was explored.The influence of the situation on the optimization results is finally based on the National Automobile Samplin g System-Crashworthiness Data System(NASS-CDS)database to determine the weighting factors of different working conditions and obtain new optimization results.It is useful for improving the crashworthiness of the trolley in 100% rigid wall collision and 40% offset collision while sacrificing the performance of dynamic three-point bending conditions.This analysis method has reference significance for the design of bumper beam system.(3)The crashworthiness of the foam-filled bumper beam system under the front pillar collision condition is analyzed and optimized.Based on the simulation,the parameters of foam filled bumper beam system are analyzed.The results show that the wall thickness parameters and foam gradient index of different parts of the bumper beam system have certain effects on the crashworthiness and deformation mode of the front pillar under collision conditions,and the gradient filling structure has some advantages in crashworthiness compared with the uniform filling structure.The multi-objective optimization design is further developed.The bruise of performance improvement at the same time realizes the lightweight design.In addition,multi-objective optimization by weighting method has carried on the multiple perspectives,analyses the impact on the effect of weight coefficient of different angles.