| Under the background of increasing global automobile holdings,energy shortages and environmental pollution,electric vehicles are the only long-term solution for future transportation,but electric vehicles have not been able to achieve high-capacity and lightweight battery technologies.Therefore,automotive lightweight technology for the development of electric vehicles is still of great significance.In addition,the lightweight effect of composite materials has great potential,and applications of composite materials are becoming more and more widespread.In the future,automotive structural materials are expected to enter the era of composite materials.As the front-end structure of BIW,the bumper beam of is particularly important for the low-speed frontal crash conditions.The paper mainly focuses on the layer design of the anti-collision beam of carbon fiber composite materials.Firstly,it determines the optimal combination of the cross-sectional shape and the lamination sequence.Secondly,it optimizes the thickness of anti-collision beam structure by multi-objective optimization and improves the collision performance.The weight reduction effect is nearly 65%.After the optimized structure of the anti-collision beam is connected with the energy absorption box and the front side beam structure,the deformation mode is reasonable during the high-speed collision process.The specific research content of the thesis mainly includes the following aspects:Firstly,according to the standards for front and rear protection devices of automobiles and the provisions of C-NCAP,the finite element models for low-speed and high-speed crash simulation of front-end structures of automobiles are respectively established,and 50 km/h high-speed collision is applied to steel anti-collision beams,and actual vehicle test is conducted to verify the accuracy of the model;a low-speed collision of 4km/h is made on the steel anti-collision beam,and the simulation curves of the energy absorption,the collision force of the energy absorbing box cross section,and the collision intrusion of the anti-collision beam are obtained,which are references of the follow-up design of the carbon fiber composite material.Secondly,according to the design engineering experience of the commonly used anti-collision beam cross-sections and the classical laminate theory,a new type of anti-collision beam of composite material is first designed.First of all,the low-speed crash simulation analysis is performed,and the performances of the steel anti-collision beam are compared with that of the carbon fiber composite,the huge lightweight advantages of composite are obvious;then the impact properties of anti-collision beams are studied in terms of cross-sectional shape and layer sequence,and the combined effects of the two factors are tested in full-factor experiments.The comprehensive balance method is used to analyze multiple index tests to determine the optimal combination of cross-sectional shape and layup sequence.Thirdly,the multi-objective optimization of the thickness of the anti-collision beam is conducted,and the design idea of changing the thickness of the different plates of beam is proposed.The multi-objective optimization is performed,targeting collision force and mass of the beam as goals,and the amount of the absorbed energy and collision intrusion as constraint.Compared to the pre-optimization structure,the energy absorption of the optimized structure was improved by 4.7%,the collision force was reduced by 47%,the mass was reduced by 46.6%,and the collision intrusion of beam was increased by 13.0%,but still meet the stiffness requirements.The structural quality of the steel anti-collision beam is 2.321kg,and the final optimized structure quality is 0.825kg,the weight reduction reaches 64.5%,which fully validates the huge lightweight advantages of the composite.Connect the optimized anti-collision beam structure to the energy absorber box,and perform high-speed collision simulation.The simulation deformation results are reasonable. |
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