Analysis And Application On Injury Biomechanics Of Lower Extremityfor Pedestrian And Occupant

China is one of the countries with the largest number of traffic accident casualties. How to avoid or reduce the injuries of road users in traffic accident is a research hotspot in the field of automotive safety. In traffic accident, lower limb injuries are the second most frequent region accounting for 29.1% of traffic injuries, witch is next only to head injuries(33.4%). Although limb injuries are rarely fatal, they are very costly and offen lead to long-term disability or impairment. Therefore, the in-depth study of the biomechanical response, injury mechanism and injury tolerance of lower limb in traffic accident has guiding significance to the design of vehicle safety and the improvement of automobile safety regulations.In order to better analyze the injury mechanism of pedestrians′ and occupants′ lower limb in road traffic accidents, lower limb biomechanical model with high precision of pedestrian and occupan were developed based on the CT data of a volunteer representing the physical characteristics of the 50 th percentile Chinese male. The lower limb model included complete anatomical structure of femur, tibia, fibula, patella as well as soft tissues such as skin, fresh, ligaments, capsule meniscus and cartilage. Considering the nonuniformity of the section of cortical bone, the long bone models were developed based on CT data with the thickness and the shape of the cortical bone section varied continuously. Linear viscoelasticity material model was chosen for knee ligaments to reflect their viscoelastic characteristic and the viscoelastic material parameters such as long-term and short-term shear modulus were identificated based on biomechanical experiments.The biofidelity of the lower limb biomechanical models were analyzed and evaluated based on the PMHS tests. The results showed that the lower limb models of pedestrian and occupant developed in this study had a high level of biofidelity, which can accurately simulate the biomechanical responses and injuries of lower limb in traffic accidents. In addition, the injury tolerances of each part of lower limb were obtained according to the verification. And the influence of the thickness of cortical bone to injury tolerance was analyzed: if the cortical bone was thinning by 1%, the injury tolerance of long bones would reduce by 0.7%.The study of biomechanical injuryof lower limb for pedestrian and occupant were conducted using the lower limb biomechanical models which were verified. For pedestrian, though filling trapezoidal bubble structure and appropriately reducing the bumper height, the safety of a brand car to lower limb of pedestrian was improved. For occupant, simulations were designed to analyse the influence of the relative collision angle upon KTH injuries in frontal crash conditions. The KTH has high injury risk when the projection angle of the impact surface normal and occupant femoral axis in horizontal plane is zero. And the KTH injury risk decreases when the absolute value of the projection angle in horizontal plane increases, especially when the impact surface rotate to the lateral of thigh. Besides, the risk of KTH is also closely related to projection angle of the impact surface normal and occupant femoral axis in sagittal plane.