Abstract:
This paper details the creation and application of a finite element model designed to investigate injury mechanisms of the lower extremities in vehicle collisions. The model is built upon anatomically correct digitized bone surfaces of the pelvis, femur, patella, and tibia, with muscles, tendons, and ligaments incrementally added to the basic bone structure. The nonlinear large deformation finite element code DYNA3D was used to simulate two types of occupant loading scenarios. This method was chosen because it provides a consistent way to discretize structures, accurately describes complex geometry and material inhomogeneities, and can accommodate large deformations, as well as anisotropic, viscoelastic, or nearly incompressible material behaviors characteristic of biological tissues. The model was used to simulate a sled test where the pelvis was fixed and the foot was fixed to the vehicle's toepan, using actual toepan displacement data as a boundary condition. The simulation showed qualitative agreement with existing sled test data and revealed high levels of stress in the patella, tibial shaft, and femoral head region. A second simulation involved a knee impacting a generic knee bolster, which calculated excessive stress levels in the knee and pelvic regions that correspond to observed fracture patterns. The authors acknowledge that the model makes certain assumptions, such as treating the leg as a passive system without active muscular contraction, but the modeling approach accurately captures the mechanics of lower extremity motion and is considered a valuable tool for understanding injury processes and mechanisms. Further work is needed to refine the model, but it currently meets its objective.
