Comparative Analysis Of Chest Responses Of Adults And Children Under The Horizontal Impact Of Small Unmanned Aerial Vehicles

Light and small unmanned aerial vehicles(UAVs)have been applied to various situations in life,but they also bring potential safety hazards to people.At present,there have been certain research of UAV’s impact on human head at home and abroad,while there is still little research of it’s impact on the chest that occupies a larger body area.In addition,in accidents caused by UAVs,adults and children have different mechanical responses when their chests are impacted.Therefore,it is necessary to study the difference between injuries caused by the UAV impacting on an adult’s chest and that on a child’s.First,this paper explores the research background and current situation of huma n chest injuries brought by UAV impact,as well as the main research methods of adults and children’s chest injuries,assessment criteria and tolerance limits of human chest injuries.Then,on the basis of preliminary finite element models of adults and children’s chests that the research team has already had,further modification and improvement are done to finally build biomechanical finite element models of adults and children’s chests with relatively high biofidelity.The modeling process is first to obtain the original 3D structure of the scapula,clavicle,muscle and others that are not included in the original model by threshold segmentation and processing of their CT images through Mimics,and then to smooth these tissue structures;what followed is to use Hypermesh and Truegrid to divide the meshes according to the structural characteristics of each tissue of the chest,and finally to define the material attributes of each tissue.Finally,the finite element models of adults and children’s chests with high fidelity is established.Based on the existing cadaver collision experiments in the literature,the models for adults and children are verified respectively,and the results show that both of them have high biofidelity.Next,the impact simulations of Hybrid Ⅲ adult dummy model and the 6YO child dummy model are conducted at different speeds of a DJI Mavic2 UAV,and the injuries are assessed by global response indexes of 3ms-acceleration,chest compression,viscous criterion and CTI chest comprehensive injury.According to the prediction results,at the same speed,the global indexes of the child dummy far exceed that of the adult dummy,which indicates that children are more vulnerable to injuries than adults.Finally,the UAV is set up under the same flight conditions as in the dummy simulation to conduct the impact simulation of the finite element models of adults and children’s chests based on anatomy built in this paper.The global response in the biomechanical finite element model is close to,and is slightly higher than the calculation of the dummy simulations.The adult does not show a high injury risk under the impact condition of 20m/s(AIS3+),while some of the injury indexes of the child dummy exceed the limit under the impact condition of 9m/s(AIS3+).The injuries of head tissues are predicted by the biomechanical model and the results show that the UAV will bring injury to the chest in the adult finite element model at a speed of 15m/s,and bring injury to the heart and lung tissues of children at 7m/s.In different attitude impact of UAV,the damage of side impact is the lowest;At the same speed,both the adults and children’s finite element models show that the soft tissues of children are more vulnerable to injuries than that of adults.In addition,the bone structure shows no injuries,which is consistent with the global response indexes.There are 75 figures,12 tables and 68 references.