Study Of Uniform Occupant Restraint System On Vehicle Crash Protection

Occupant restraint system is playing an important role in occupant protection in vehicle crash;meanwhile,it can also induce occupant injuries in some cases.For example,the concentrated restraint force on occupant ribcage by shoulder belt can cause rib fracture,and lap belt may penetrate into abdomen when submarining happens.Those problems have drawn some attention,and new restraint devices have been put forward.This thesis explored and evaluated a new restraint concept by using finite element method,proving that the uniform restraint concept can provide good occupant protection and the idea may also work in protection of reclined occupant.The concept was explored and preliminarily evaluated in LS-DYNA environment.Then the system was modified considering some feasibilities.To make further evaluation of the concept,a detailed seat finite element model was developed.A simulation platform was developed based on the seat model,and influence of key parameters of the uniform restraint concept was studied using sled test simulations.The concept was evaluated in 48km/h frontal crash simulations with Hybrid III dummy model and THUMS human body model.The effectiveness of uniform restraint system was also compared with that of seatbelt system.It has proved that uniform restraint system can provide occupant protection to the extent comparable to that of seatbelt system,measwhile it can reduce chest deflection and induce better ribcage deformation mode,consequently decreasing rib fracture risk.The effect of head restraint in the uniform restraint system was examined,showing that the head restraint can control head excursion in 48km/h frontal impact but has little effect on injury parameter readings.By manually optimizing restraint force level,uniform restraint system was used for occupant protection in high severety impact.As the impact speed increases to 72km/h,the system can work well,with all the injury readings below respective thresholds.Moreover,when the speed increases to 81km/h,the protection effect is acceptable,only with the chest acceleration slightly greater than 60 g.Different crash pulses were also examined,showing that crash pulse shape had some effect on occupant protection.Uniform restraint concept was used for reclined occupant protection.The idea was to restrain occupant lower body by early knee bolster engagement and meanwhile release upper body restraint,then occupant could adjust posture from reclining to upright by inertial force.The influence of knee restraint and reclined angle on occupant posture adjustment was examined.It shows that early engagement of knee restraint and relatively small reclined angle can reduce spine flextion and make posture adjustment easier.Then the idea of using knee boster and seatblet with low load limiter force level to protect reclined occupant was proved to work properly in 30km/h frontal impact.