Study On Influence Of Human Upper Body On The Pedestrain Lower Extremity In Impact Test

With the deepening of the automotive safety research, the pedestrian safety issuesare increasingly taken into account by scholars around the world. Recently, manycountries and areas, such as European Union and Japan, have drawn up a series ofregulations about pedestrian safety in road traffic accidents. China also implementedthe the national standards of GB/T24550-2009car-pedestrian collision protection in2009. However, some studies indicate that the lower legform impactor used inregulations can’t reflect the real situation of vehicle-pedestrian collision well, and theinjury evaluation performance remains to be optimized. Lacking support of upper bodyalso has a significant influence on the evaluation performance of lower legformimpactor. So, this thesis mainly discusses the leg injuries in car-pedestrian, car-leg andcar-legform collisions, in order to analyze the influence of pedestrian upper body onleg injuries.Base on the literature research, this article has certificated the simulation modelof vehicle, pedestrian, single leg and lower legform impactor with HyperMesh12.0andLS-DYNA971, then established and solved the impact simulations of SUV-pedestrian,SUV-single leg, SUV-legform, sedan-pedestrian, sedan-single leg and sedan-legform.Analyzed the injuries in the collisions, and investigated the differences of knee bendingangle, knee shear displacement and tibia acceleration in the situations of with andwithout support of upper body.Taking the results and the trends of injury parameters of the simulation ofvehicle-pedestrian collisions as a benchmark, compare them to other injury value fromvehicle-single leg and vehicle-legform simulation, and these conclusions werediscovered. First, as the impact position in the SUV-pedestrian collision is above thecenter of knee joint, the whole upper leg impacts the car front. Lacking the upper bodymass(UBM), it reduces the knee bending angle. And due to the mass of single leg islower than a whole person, according to the law of conservation of momentum, theformer will get a larger velocity, thus leading to a larger shear displacement of kneejoint and tibia acceleration. Second, as for sedan with much lower car front, without aflexible traction from upper body and block from car front-end, the femur bends fastand impacts to the bonnet, which results in a much larger bending angle. Because of thetension of ligament, it makes the shear displacement and tibia acceleration smaller than the benchmark. Third, the results of the legform-car impact are much larger than thebenchmark, because the inertia of lower legform impactor is smaller than whole person,and it results in a quick response. The minimum deviation ratio is24.6%, the maximumis up to369.2%, which obviously indicates the influence of UBM on pedestrian lowerextremity impact test can’t be ignored. This research qualitatively analyzed theinfluence of human upper body on the pedestrian lower extremity in impact test. It’shelpful to improve the accuracy of the lower limb impact test to evaluate automobilesafety.