Design And Verification Of Helmet Based On The Head Damage During Collision

As shown in the latest global road safety status report published by the World Health Organization in 2015,the number of people killed in road traffic in 2013 was 1.25 million.In all people who died as a result of road traffic accidents,half are pedestrians(22%),cyclists(4%)and motorcyclists(23%).And this data is basically stable.Among them,the head is the place where pedestrians and bicycle riders have the highest probability of causing death in traffic accidents.Therefore,it is imperative to take effective protection measures for the above-mentioned people.The development of biomechanics of head injury is reviewed at first.The structural division of the human head and the evaluation criteria for head injuries are introduced in detail.At present,the methods of studying head injury mainly include physical model method,animal experiment method,cadaveric experiment method and finite element method.The evaluation criteria mainly include Wayne State Tolerance Curve(WSTC),Head Severity Index(SI),Head Injury Creator(HIC),and AIS(Head Injury Creator).Abbreviated Injury Scale),Glasgow Coma Scale,and brain tolerance limits.Second,use the handheld 3D scanner and CATIA software to reverse the design based on the real helmet.A more realistic 3D model is established.Mainly modeled for helmet shells and energy absorbing liners.The corresponding finite element model is constructed according to the model.Furthermore,the helmet model is coupled to the existing human head model.Drawing on the latest research results in the setting of relevant parameters.Strict selection of contact forms,parameters and coupling conditions that have been tested and verified.Simulate the dynamic response process at the time of the collision in accordance with the collision process specified in the regulations.Verify the accuracy of the coupled model.Finally,based on European regulations and national standard GB-811,the Von Mises stress is used as the evaluation index,and the helmet material is used as the optimization parameter to optimize the design of the helmet.According to the influencing factors and their levels,two three-factor and three-level orthogonal experiments were designed.The existing helmet was optimized from the material properties,and the optimal scheme was determined and verified.Through the modeling of the helmet and coupling with the head model,simulation were carried out to study the key material parameters affecting the energy absorption characteristics of the helmet.According to the results of two groups of experiments,density is the most significant factor affecting the energy absorption effect,followed by Young's modulus,and finally Poisson's ratio.For the case,the order of influence degree is the same.Among the six parameters,only the hypothetical test F value of the energy absorbing liner is obviously larger than the critical value of hypothetical test F,while the other five factors are less than the critical value of hypothetical test F.This shows that the density of the energy absorbing liner is the material parameter that has the greatest influence on the energy absorbing characteristics of the helmet.After wearing the optimized helmet,the maximum von Mises stress of the skull was reduced from 25.26 kPa to 20.35 kPa,which was reduced by 26.04%.The maximum von Mises stress of the brain was reduced from 4.34 kPa to 3.38 kPa,which was 22.12% lower.These results provide important data support for further optimized design of the helmet.