| The front bumper system is an important system of the front end of the vehicle.In terms of low speed collision,its main role is to protect the radiator,active intake grille,washing pot and other internal parts of the front end of the vehicle,so as to reduce the maintenance cost of the vehicle in low speed collision.Therefore,the front bumper of the vehicle should have enough strength.In the aspect of pedestrian protection,the injury of the front bumper system to the pedestrian’s leg is directly related to the strength and energy absorption space of the front bumper system.Based on this,this paper will comprehensively consider the vehicle front bumper system low-speed collision and pedestrian protection and other two aspects of the vehicle front bumper system research.Firstly,the modal characteristics,stiffness characteristics and strength characteristics of the bumper skin are analyzed.The modal analysis results show that the first-order natural frequency of the front bumper skin is greater than the excitation frequency caused by the road irregularity,which can avoid the resonance of the front bumper to a certain extent and meet the modal requirements of the front bumper.In the finite element simulation of the stiffness of the front bumper skin,by analyzing the deformation of the skin at 10 loading points,it is concluded that the stiffness characteristics of the front bumper skin meet the technical requirements of enterprises.For the strength analysis of the front bumper assembly,by comparing the maximum stress of different parts and the yield strength of its materials after loading in the X,Y and Z directions,the final conclusion is that the front bumper assembly meets the strength requirements.According to the requirements of GB 17354,the front bumper low-speed collision model was built.The simulation analysis showed that the front bumper system had a frontal impact at the speed of 4km/h and the front bumper system had a 60°Angle impact at the speed of2.5km/h.The results showed that the deformation of the front bumper beam met the design requirements.According to the current domestic each big Car company attaches great importance to the C-NCAP(China New Car Assessment Programme(China New Car Assessment procedures)set up the requirements of the relevant finite element model of the pedestrian leg collision,the simulation calculation for the leg and the vehicle front bumper 17regional crus,legs bending moment after collision,the change of the knee ligament elongation(MCL),the results show that nine of the area of the collision of calf leg bending moment of area and knee ligament elongation without the high performance limit prescribed by the C-NCAP,There are 15 areas where the thigh bending moment is not within the C-NCAP high performance limit,resulting in a low leg crash result score,so further optimization of the front bumper is required.Finally in order to improve the front bumper system in the performance of the pedestrian leg protection,support bracket in the inside of the car front,legs protect stents,headlight installation point and confirmed before installation point is optimized,according to the latest version of C-type specified in the leg NCAP crash rating score method to the optimization result,score results show that the lower leg bending moment is 2 points,increased 0.609 points;The thigh bending moment score was 2 points,which increased by 1.201 points,which was the most obvious;Knee bending moment(MCL)elongation score is 1 point,an increase of 0.293 points.It shows that the optimization direction is very reasonable,and the research results can be used as a reference for the development of pedestrian leg protection of other new models. |
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