| As the car ownership continues to increase,the probability of road traffic accidents increases,with frontal collisions accounting for the largest proportion.At present,the problem of aging in China is becoming more and more serious.The average age of road users has been gradually increasing,and the high incidence of osteoporosis caused by aging will change the injury mechanism and tolerance of the human body.The long bones and joints of the lower extremities are prone to senile osteoporosis,and injuries to the lower extremities often occur in frontal collisions,which will bring great trouble to the victims’ lives.In recent years,the research on the injury of vulnerable groups using roads is a hot spot,but the influence of osteoporosis on lower limb collision injury is still unknown.Clarifying the impact of osteoporosis on lower extremity injury can not only provide data support for the design of lower extremit y protection devices and restraint systems,but also provide a theoretical basis for the injury guidelines for elderly dri vers with osteoporosis prescribed in future crash safety regulations.The purpose of this study is to investigate the effects of senile osteoporosis and muscle activation on lower extremity injuries during frontal collisions.By increasing the number of Hill elements,modifying the material parameters of the lower limb bones and joints,and using thinner lower limb skeletal cortical bone thickness and cancellous bone density Method to reduce bone content,and finally established a finite element model of lower limbs of elderly drivers with 18.5% and 26.2% bone mass reduction.Honda’s 2014 ACCORD was selected as a crash test vehicle,a simplified cockpit model containing a driver-restraint system was established,and frontal collision verification was performed.The real crash simulation environment was established,and the simulated acceleration and lower limb muscle activation curves of three initial impact speeds(40km/h,50km/h,60km/h)were extracted as the input of the simulation subsystem.Then,18 sets of simulation sequences were designed.The design variables included collision intensity,degree of osteoporosis of lower extremities,and whether muscles were activated.The result showed that senile osteoporosis reduced the carrying capacity of the lower extremities,and the dynamic response of the lower extremities decreases as the bone content decreases,while the biomechanical responses between different degrees of osteoporosis are similar,and the risk of fracture increases as the decreases.Different degrees of fractures occurred at the distal end of the tibia,the proximal end of the femur,the ilium and the sacrum of the lower extremity when the collision speed was 64km/h.Lower limb muscle activation significantly increased the value of the kinet ic response and the peak stress of the bones and exacerbated lower limb bone damage. |
