Study On The Head Injury Risk Of Six-year-old Child Under Horizontal Impact Of Small Unmanned Aerial Vehicles

With the wide application of the unmanned aerial vehicle(UAV)in transportation,filming,detection and other fields,it has raised concern of the public about the risks its flight brings to public safety.At present,the research on human body injury under UAV impact mainly focuses on adults,but in recent years,more fatal accidents happening to children caused by UAV falling out of control indicate that such research should take children into consideration as well.This study focuses on studying the head injuries of children and the response characteristics under UAV impact.High-quality hexahedral meshes of children’s brain is established by geometric extraction and processing as well as block projection with Truegrid.Then,with the geometric surfaces of skull,scalp and other tissues extracted,mesh models corresponding to each tissue are built in Hypermesh by stretching and nodes projection.Finally,the material of each head tissue is defined,and the finite element model of the six-year-old child based on anatomy is built.Currently,only experimental data of nine-year-old child cadaver can be retrieved from the literature.Considering that the six-year-old child is close to nine-year-old child,this paper has conducted simulations to reproduce the experiment of nine-year-old child head falling down to the ground from different heights and the compression experiment of the head.It is found in comparison that the simulation results are similar to the experimental data,proving the high biofidelity of the finite element model of the six-year-old child head.A DJI Mavic2 UAV is used for the analysis of its impact on the head of a dummy child through the design of a simulation matrix that allows the UAV to impact on the dummy head at different speeds and in diverse attitudes.Simulation analysis is made in turn against the different situations of the simulation matrix.The results of the analysis show that the faster the UAV’s impact speed,the greater the risk of head injury in children.For impact from a UAV in different attitudes,it brings the severest injury when the impact comes from the side of the UAV in level flight compared with other cases.And finally,the simulation is conducted as per the same conditions mentioned above through the model of six-year-old children’s head which is built based on anatomy with high biofidelity.It is found that most of the global dynamic resonses of the UAV at different speeds and in diverse attitudes are consistent with that conducted on the dummy mentioned above.Furthermore,the model of six-year-old child head with high biofidelity built in this paper also predicts the risks of skull rupture and brain injury,which shows that a speed equals to or above 20m/s implicates higher brain injuries in children.Based on the biomechanical model prediction result,according to the commonly used index HIC can concluded that the probability of serious AIS3+ head damage is 20%-30% when the frontal horizontal collision speed of the UAV is 20m/s.