A Study Of Lower-Limb Dynamic Responses And Injury Biomechanics In Vehicle-Pedestrian Collisions

In vehicle–pedestrian collision, the lower limbs of pedestrian are frequently injured by vehicle front structures. In order to investigate the dynamic response and injury mechanisms of the lower extremity to a lateral impact, the current study was to improve a 3D finite element (FE) model of the human lower limb in traffic accidents using finite element method. Using the FEM model predicting the risk of the knee joint ligaments, also combination with the real-world pedestrian accident to investigation the bone fracture of the lower limbs. The result of this study can form a background knowledge to research the injury biomechanics of the lower limbs.The FE model is based on anatomical structure of lower limb which consists of the pelvis, the femur, the tibia, the fibula, the patella, the foot bones, primary tendons, capsules, meniscus, and knee ligaments. The mass distribution and material properties of the bones and soft tissues are based on biomechanical data from the published literature. The model is constructed using shell and solid elements which mesh by Hypermech, also include linear spring-damper elements and consists of 29777 nodes, 30873 elements, the effective mass is 13.4kg.The model is implemented by using the finite element program LS-DYNA3D. The validity of the model of tibia segment is evaluated against three point bending test in terms of tibia stress. The whole model is validated according the cadaver test data. The dynamic response and injury risk of the long bones and knee ligaments are analyzed in different impact locations; The FE HBM-lower limb and an existing multi-body system (MBS) human model of the pedestrian are used to reconstruct the real-world vehicle-pedestrian accident and lower limb injuries, to predict the injury parameters of the femur, tibia and fibulaThe result show that the model has a good bio-fidelity by improving; The stress on the bone is concentrated in the impactor contact area, which can cause a high fracture risk;In impacts to the femur or knee, the injury of the MCL are especially higher than other ligaments due to the valgus motion of the knee joint, which could cause knee ligament rupture; In different angle impacts, the injury risk of cruciate ligaments can also become high because of the tension of these ligaments; the lowering of the bumper height can reduce of the risk of the knee ligaments; The result of reconstruction of the accident show the injury criterion indicts calculated from the reconstructions were compared with hospital reports, and the von Mises stress as a parameters which indict the fracture tolerance level of the femur, tibia, fibula are 115Mpa, 125Mpa, 125Mpa respectively. The results demonstration that this model have a good capability to predict injuries types and severity in vehicle-pedestrian impact. The HBM- lower limb will contribute to the research on lower limb injury mechanisms and development of the injury protection device. And the fracture tolerance level of the long bones can be used as a reference for this research.