Development and Validation of a Knee-Thigh-Hip LSDYNA Model of a 50th Percentile Male.

Silvestri, Chiara

Etd

Development and Validation of a Knee-Thigh-Hip LSDYNA Model of a 50th Percentile Male.

Public

With the introduction of air bags, occupant safety in frontal car crashes has been improved for upper regions of the body, such as the head and thorax. These improvements, however, have not helped improve the safety for the lower extremities, increasing their percentage of injuries in car crashes. Though lower extremity injuries are usually not life threatening, they can have long lasting physical and psychosocial consequences. An LSDYNA finite element model of the knee-thigh-hip (KTH) of a 50th percentile adult male was developed for exploring the mechanics of injuries to the KTH during frontal crash crashes. The model includes a detailed geometry of the bones, the mass of the soft tissue, and a discrete element representation of the ligaments and muscles of the KTH. The bones were validated using physical tests obtained from the National Highway Traffic and Safety Administrationâ€™s (NHTSA) test database. The geometry, the material properties and the failure mechanisms of bone materials were verified. A validation was also performed against a whole-body cadaver test to verify contributions of passive muscle and ligament forces. Failure mechanisms in the tests and simulations were compared to ensure that the model provides a useful tool for exploring fractures and dislocations in the KTH resulting from frontal vehicle crashes. The validated model was then used to investigate injury mechanisms during a frontal car crash at different occupant positions. The role of muscle forces on these fracture mechanisms was explored and simulations of frontal impacts were then reproduced with the KTH complex at different angles of thigh flexion, adduction and abduction. Results show that the failure mechanism of the lower limb can significantly depend on the occupant position prior to impact. Failure mechanisms in the simulations were compared to results found in literature to ensure the model provides a useful tool for predicting fractures in the lower limb resulting from out-of-position frontal vehicle crashes. The FE model replicate injury criteria developed for ligament failure and suggested lowering the actual used axial femur force threshold for KTH injures both in neutral and out-of-position KTH axial impacts.

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