Blunt Injury Response of Occupant Lower Extremity during Automotive Crashes: A Finite Element Study

More than half of occupant lower extremity (LEX) injuries during automotive frontal crashes are in the knee-thigh-hip (KTH) complex. The objective of this study is to develop a better understanding of the KTH injury mechanisms and injury thresholds using a new finite element (FE) human model. A detailed biofidelic occupant LEX FE model is developed based on the component surfaces reconstructed from the medical image data of a 50 percentile male volunteer in a sitting posture. The hexahedral element type is used to mesh the majority of the deformable skeleton and soft tissues. Appropriate constitutive material models are assigned to each component with the corresponding parameters rigorously identified in the ranges of published test data. Eight loading cases are simulated and the model’s predictions are validated at both regional and global levels to the latest corresponding test data recorded in cadaveric testing. These validations are focused on the predictions of frontal Crash-Induced Injuries (CII) recorded in vehicle crashes, which includes the femoral mid-shaft/head fractures, tibia distal-third fracture, and knee ligament failures (e.g. posterior cruciate ligament (PCL)). Then, a sensitivity study is performed using the validated KTH model to investigate the effect of the hip joint angle to the acetabulum injury tolerance in frontal impacts. The results indicate a tendency of less stress concentration in the illac wing and a 16% to 36% hip injury tolerance increase with the hip joint flexion angle increasing from -30 to +20 relative to the neutral posture.