Simulation Analysis And Optimization Of Restraint System In Small Offset Collision Of Car

On the conditions of the small offset collision,the rigid barrier is impinged on the front of vehicle with a speed of 64km/h and a 25%overlap rate.The abilities of energy absorption of the structure of the front longitudinal beam and other structures are insufficient,resulted a significant increase in the vertical steering direction of the vehicle and an increased intrusion of the passenger compartment,compared with other conditions.Even if the car body structure and the restraint system meet the requirements of 100%frontal collision and40%offset collision,the occupant protection effect under small offset collision conditions still has relatively large defects.In 2016,the number of domestic female drivers was 97.38million,accounting for 27.23%of the total number of drivers,and the number is increasing year by year,so the importance of female occupant protection is increasingly prominent.For the reason of female driver have large differences in body size and physique with men,the mechanism of injury in the collision process is unique.However,the current evaluation and research on small offset collision conditions and female driver protection are still lacking.The main research contents of this thesis include the following sections.Firstly,based on the physical collision test,the restraint system model under 100%frontal collision conditions is built,and the key characteristics of the seat belt and airbag are simulated to ensure the validity of the model.Benchmarking verification was performed through the comparison between simulation results and experimental results.Secondly,converted the boundary conditions of the constrained system model into small offset collision conditions,then the occupant motion and damage under 100%frontal collision and small offset collision conditions were compared.The occupant characteristics of the damage caused by the small offset collision conditions were summarized.With reference to the requirements of the occupant movement form in the regulations,a targeted improvement scheme for the restraint system is proposed.Thirdly,compare the male driver and female driver corresponding injury limits in the regulations,and analyze the differences in injury tolerance between the two body parts.The movement characteristics and injuries of the two dummy were compared under the same restraint system,and the damage characteristics of the female driver were analyzed.Fourthly,in order to optimize the restraint system parameters which taking into account of the female driver's,Isight software is used to establish the relevant agent model:the design parameters are determined by screening the relevant parameters through sensitivity analysis;the restraint condition is to ensure that the male dummy damage value is above the good level in the C-IASI damage evaluation;the target value is the comprehensive injury which takes into account both male and female dummy.The optimal scheme is obtained by NSGA-II optimization algorithm and reversed into the simulation model.Finally,the effectiveness and feasibility of the optimization scheme are analyzed.The results of this paper show that:?1?For the small offset collision conditions with complex motion forms and large local deformation,a more perfect boundary condition application method is proposed.The advantage of this method is:compared to the method of extracting the acceleration curve,this method reproduced more accurate results including movement and deformation forms of the relevant vehicle body mechanism and interior structure in the vehicle collision result,and has the ability to take into account of the external force response.?2?For the small offset collision condition,the movement of the dummy head from the surface of the DAB and the impact of the impact on the A-pillar is effectively avoided by the double protection of the CAB and the shaped DAB.The shaped DAB realizes the purpose of protecting the occupant under two working conditions by extending the range of the left and right ends,which improving the protection effect of the small offset collision condition and reducing the impact on the 100%frontal collision working condition.?3?Comparing the injuries of male and female drivers under the same restraint system,the results show that the restraint system developed for male driver cannot match female driver very well,for the female driver are lower and more advanced than males.The X-direction acceleration,pelvic acceleration,and left and right thigh strength of the female head increased by 25.7%,34.8%,52.6%,and 17.5%,respectively,compared with male dummy,and the phenomenon of occupant dive occurred.?4?Based on the agent model,achieved the purpose of optimizing the restraints of multiple drivers.The optimization scheme mainly reduces the contact rigidity between the occupant and the airbag by increasing the area of the ventilating hole of the shaped airbag by 19.75%and the ignition timing by 23.33%.The WIC values of the final 50-percent male occupant and the 5-percent female occupant improved by 14.1%and 10.7%,respectively.The effect was mainly reflected in the reduction of the head HIC₃₆ and chest compression,and effectively prevented the female occupant from diving.Based on computer simulation technology,this paper models and optimizes the system of female driver under small offset collision conditions.The optimization includes the improvement of frontal airbag and the matching of related parameters,which provides reference for the development of car-related safety system.