A Study On The Biomechanical Of Occupant Ankle Injuries In Car Frontal Impact

The form and mechanism of ankle injury are complex and diverse in the car frontal collision accident.In the current study of ankle injury,the experimental load is relatively simple,the loading conditions are simplified.Limited by the variability of the sample,the small number of trials,the limit in measurement conditions of the material properties and the limited development and validation level of the mathematical model,they can not be applied to the study of ankle injury under complex loads.The model,which is established based on Europe and America human data,are quite different to the Chinese human body for the geometric data.Therefore,it is of great significance to establish an accurate Chinese 50th percentile male foot-ankle-lower leg finite element(FE)model and study the biomechanics of ankle injury for the actual situation of the collision.A previously developed and preliminarily validated Chinese 50th percentile male lower leg FE model was employed in this study.According to Chinese human statistical data,improving the foot of the model,increasing the ankle ligament parts,updating the model material,adjusting the model's sitting position.Then,the improved Chinese 50th percentile male foot-ankle-lower leg FE model was obtained.According to the ankle injury mechanism,the foot-ankle-lower leg model was verified under the front foot impacting,axial impact loading,internal/external rotation loading,dorsiflexion loading,inversion/eversion loading and combined the aboves loading.The results show that the mechanical response and damage results of the model are consistent with the experimental data of PMHS.The accuracy and bio-fidelity of established FE model was proved.The results of ankle injury in the internal rotation and external rotation of the pedal impact load show that the main ankle injury is ligament failure.There is a 13%change of the ankle joint torque corresponds to the ligament failure in the rotation range of ±15°.The most vulnerable position was the internally rotated(15°)posture.A method to study the damage tolerance was propose according to the main injury mechanism(axial load,dorsiflexion and inversion/eversion)of the driver's ankle in the frontal collision and the injury type and injury parameter change caused by the change of the loading rate in the simulation.In this way,the three-dimensional injury surface boundary with tibial force,dorsiflexion angle and inversion/eversion angle was established.The effects of four factors:axial loading rate,internal/external rotation angle,dorsiflexion angle,inversion/eversion angle on the ankle injury parameters were analyzed by orthogonal experiment.The results show that,ankle injuries are occurred in eleven of nine virtual tests.The most sensitive parameter to tibial force is axial loading rate.The most sensitive parameter to ankle moment is axial loading rate,followed by dorsiflex angle and inversion/eversion angle.There is litter effect on tibial force and ankle moment for internal/external rotation angle.To validate the injury surface developed in this study,the low speed(20 km/h)and high speed(48 km/h)conditions were designed to simulate the vehicle frontal collision based on the FE model of the driver constraint system.The results showed that,the first injury of ankle and foot at low speed and high speed was ligament failure and ankle fracture.The injury parameters are basically consistent with the injury boundary.The boundary of the three dimensional injury surface of ankle under combined axial loading,dorsiflexion and inversion/eversion is effective.