A Finite Element Simulation Impact Comparative Study Between The Lower Legform Impactor And Lower Limbs

There are many countries have established regulations on pedestrian protection intraffic accidents, such as the European Union, Japan, Australia and so on. China alsoenacted its own regulations and standards for pedestrian protection recently. However,some studies indicate that the lower legform impactor model in regulations can’tevaluate the protection of the car-front to the legs well. This paper aims to explore thedifferences between the human lower limbs and the lower legform impactor from theaspects of the structure, collision dynamics and collision damage responses.The establishment of a finite element (FE) model of lower legform impactor wascompleted in Hypermesh9.0. Based on relevant literatures, the appropriate propertyand material parameters in the model were set. Referring to the national standards, thestatic bending, static shear and dynamic impact test simulation calibration werecarried out respectively in LS-DYNA971. Simulation results show that the lowerlegform impactor model complied with the rules well. The finite element model of aSUV vehicle was also established, and the stiffness of the front part was proved validin the simulation compared to the experiment. In need of comparative study, a finiteelement model of a typical sedan car was downloaded from the USA National CrashAnalysis Center website, which has been proved valid in many fields. The two vehiclefinite element models were simplified in order to reduce simulation cost. Furthermore,an improved finite element model of the human lower limbs was used as thebenchmark model in the comparative study. Consequently four FE crash models werecreated: human lower limbs with SUV and sedan car respectively; lower legformimpactor with SUV and sedan car respectively.The simulation results show that collision dynamics differences existed betweenthe lower legform impactor and human lower limbs. When the lower legform impactorimpacting the SUV and sedan respectively, shear displacements were5.1mm,2.2mm;bend angles were28.5°,24.1°, and tibia accelerations were249g,234g. When lowerlimbs were impacted by SUV and sedan respectively, the shear displacements were6mm,9.2mm; bend angles were44°,45°; and upper tibia accelerations were209g,211g. Comparing to the evaluation parameters of shear displacement (6mm), bendangle (19°) and tibia acceleration (170g), the results show that the impact would causelower limbs injuries since of the bend angle and upper tibia acceleration. When human lower limbs impacting the SUV and sedan respectively, ligaments were broken, boneswere not broken and the injury was defined as the moderate damage based on theabbreviated injury scale (AIS). This paper draws a conclusion that injuries due to bigbend angle and big tibia acceleration could be predicted by the lower legformimpactor. As to three parameters measured from the lower legform impactor comparedto human lower limbs, the deviation is that the bending angle and shear displacementare much smaller, but the upper tibia acceleration is much larger.