Damage Analysis And Restraint System Optimization Of The Rear Occupants Based On THUMS Model In Front Impact

The riding environment of the rear occupants is more complicated,and the rear restraint system needs to take into account the safety of occupants of all ages and different body types.At present,the new car assessment programs of various countries pay more attention to the safety of the front occupants,which makes the automaker configure a more advanced restraint system in the front row,while the configuration of rear row restraint system is relatively simple,and does not have the conditions for configuring airbags and knee pads.the rear row of a dummy in the crash test is usually the 5th percent female dummy and a child dummy?such as C-NCAP,Euro-NCAP,and J-NCAP?,lacking the safety of medium and large body occupants.All of these situations make the safety of rear occupants facing severe challenges.Aiming at this challenge,this paper establishes the rear finite element restraint system model of a vehicle based on the C-NCAP front 100%collision test data and verifies its effectiveness;under the same working condition and restraint system configuration,the 5th percentile Female dummy was replaced with THUMS 50th percentile and Hybrid-III 50th percentile to evaluate the protective effect of the restraint system for medium-sized occupants and to compare the differences of THUMS dummy and Hybrid-III dummy in human dynamics and damage response.Then,based on the THUMS dummy,explore the influence of different seat belt configuration parameters?common three-point seat belt,load-limited seat belt,three-point seat belt with pre-tensioner and load limiter and inflatable belts?on the damage of the dummy,and finally combine the polynomial agent model and The NSGA-II genetic algorithm builds an optimization platform,and the weighted damage criterion WIC is used as the optimization goal.The optimization of parameter matching of the restraint system is carried out to improve the protection performance of the medium-sized occupants.The research results show that the rear restraint system of the original model has a poor protection efficiency on the 50th percentile dummy,the head of 50th percentile THUMS dummy and the Hybrid-III dummy head have a second impact with the front seat.The head of the dummy will be seriously damaged by the AIS4 grade,the chest will be seriously injured by the AIS3 grade,and the THUMS dummy's interspinous ligament elongation will be 202%,and the neck ligament will also be damaged by the ligament tear;by comparative analysis the damage response of the two dummies verifies the applicability and comprehensiveness of the THUMS dummy in the evaluation of the damage.In addition,the parameter analysis of the restraint system shows that the pre-tensioner and load limiter seatbelt has the best effect on the protection of the chest and neck.The chest deflection?32mm?,and elongation of interspinous ligament?193%?of the preloaded pre-tensioner and load limiter seatbelt dummy are the minimum values of the corresponding damage indicators in the four configurations;the normal seat belt restrains the dummy and causes the neck and chest of the dummy to be seriously damaged;the protective efficiency of the inflatable belt on the head is optimal,the head HIC₁₅?566?,intracranial pressure?56.6kPa?,intracranial equivalent stress?4.9kPa?and skull equivalent stress?6.6kPa?are smaller than the damage index corresponding to the other three configurations,and can effectively reduce the risk of rib fracture.In order to improve the restraint effectiveness of the rear-row restraint system to the 50th percentile dummy,the NSGA-II genetic algorithm is used to optimize the parameter matching of the rear-row restraint system,so that the dummy head HIC₁₅,intracranial pressure,intracranial equivalent stress and equivalent stress of the skull was reduced by 62.4%,57.5%,32.8%and 35.75%,respectively.The WIC value of the optimized target decreased by 32%,which indicated the effectiveness of the optimization scheme and verified that the optimization scheme can simultaneously consider safety of the 5th percentile dummy and the 50th percentile dummy.