Numerical Simulation Reconstruction Of Pedestrian Traffic Accidents And Study On Injury Mechanism Of Craniocerebral Injury

Objective:The problem of accurate reconstruction of traffic accidents and the mechanism of craniocerebral injury is still one of the difficult and key problems in forensic medical identification of traffic accidents.This research aims to use various techniques and methods such as forensic medicine,engineering mechanics,and injury biomechanics to improve the accuracy of pedestrian traffic accident reconstruction.At the same time,from the perspective of biomechanics,parameterized simulation was carried out on the injury forms and injury mechanisms of pedestrian craniocerebral injury under the three different working conditions of collision,fall and rolling,so as to establish the regression curve of craniocerebral injury mode in traffic accidents.It provides a new and reliable biomechanical basis and a powerful technical support for the identification of the mechanism and mode of craniocerebral injury in the forensic identification of traffic accidents.Methods:Based on a typical pedestrian collision case,the inverse vehicle reconstruction technique is applied to restore the accident vehicle,and the multi-rigid body modeling software MADYMO is used to establish the car-pedestrian multi-rigid body model,and the non-dominated ranking genetic algorithm（NSGA-II）,the neighborhood cultivation genetic algorithm（NCGA）and the multi-objective particle swarm optimization algorithm（MOPSO）are used to reconstruct the multi-rigid body dynamics of the collision accident.The effects of different optimization algorithms on the convergence speed and the optimal approximate solution of the reconstruction process are investigated.The optimal initial collision parameters are used as the boundary conditions for the finite element simulation,and the predicted cranial injury results obtained from the simulation are compared with the actual accident cranial injury.Based on multi-rigid body reconstruction technology and finite element reconstruction technology,different conditions of traffic accident cranial collision,fall and crush are simulated by THUMS model,and a total of 84 groups of simulation conditions are simulated.Crash injury loading conditions:the human body is facing the vehicle as the 0 point,the human body coronal axis as the center of the counterclockwise rotation every 45 degrees to set a collision direction,a total of 5collision directions（0°,45°,90°,135°,180°）,the collision speed range of 20km/h～80km/h,every 10km/h set a collision speed for a total of 7 collision speeds.Loading conditions for fall injury:extracting different boundary conditions for each simulation when the skull and brain are in contact with the ground in 5 collision directions and 7collision speeds under the collision conditions.Crush injury loading conditions:the crush direction is frontal and dorsal（0°,180°）,and the crush speed is consistent with the collision.The biomechanical response of the cranial brain of pedestrians in traffic accidents under different injury-causing mechanisms was investigated through stress and strain changes,and the characteristic patterns of cranial brain injury under different injury-causing conditions were compared and analyzed;the biomechanical response of various parts of the cranial brain was biomechanically analyzed through Von Mises stress,intracranial pressure,MPS,CSDM_0.25,shear stress,cranial strain and other biomechanical indicators,and the injury response of traffic accidents was established The regression curves of craniocerebral injury causation mode are established.At the same time,the application value of numerical reconstruction technology in the mechanism of craniocerebral injury in traffic accidents is discussed with real cases.Results:Based on the vehicle reconstruction technology,the vehicle size and shape can be accurately restored,and the multi-rigid body dynamics method,finite element method and multi-objective algorithm can be used to solve the accident process of auto-pedestrian collision in reverse and analyze the injury mode and damage mechanism.The results show that NSGA-II and NCGA show better convergence speed and results than MOPSO in the optimization process,and the kinematic response and biomechanical response can be compared with the accident process and consequences for accurate reconstruction of auto-pedestrian traffic accidents.Based on the parametric analysis of cranial brain injury under three working conditions of collision,fall and crush in traffic accidents based on simulation reconstruction technology,the changes of biomechanical indexes of the cranial brain under three different working conditions can be observed,and the crush injury has more adequate kinetic energy transmission,more extensive cranial brain injury and more prone to overall deformation than the impact and fall injuries.The angle of action and the speed of action of the force have important effects on the injury of the cranial brain.On the whole,the mechanical parameters of cranial injury show an increasing trend with increasing speed in all three conditions.At the same time,the change of mechanical response of different parts of the cranial brain in traffic accidents was statistically analyzed,and the cranial injury mode equation of traffic accidents based on the cranial injury indicators of different parts of the cranial brain was established,and its validity and application value were verified by actual cases.Conclusions:Numerical simulation technology provides a new technical means for the reconstruction of pedestrian traffic accidents and the mechanical analysis of craniocerebral injury.The application of vehicle reconstruction techniques,multi-rigid body dynamics,finite element method and multi-objective algorithms can provide accurate reconstruction of pedestrian traffic accidents.The results of craniocerebral biomechanical response and the determination equation of craniocerebral injury can provide biomechanical parameters to support the analysis of pedestrian death and craniocerebral injury mechanism in traffic accidents,and provide new and reliable research and identification ideas for the key and difficult issues of craniocerebral injury mechanism in traffic accident identification.To a certain extent,this research makes up for the traditional methods and means of identification of craniocerebral injury in traffic accidents,supplements and explains the mechanism of craniocerebral injury from the perspective of biomechanics,and provides reliable mechanical evidence for the related judicial identification.