Current mathematical simulation of occupant impact and interactions with the vehicle interior, in the event of crash, is based on lumped mass-spring formulations. These models lack the fidelity to simulate structural deformations and to capture the detailed contact and interactions between the occupant and the impact targets.
As a first step in improving the technology, we have developed a detailed three-dimensional finite element (FE) model which simulated thoracic impact on the steering wheel. The model consisted of Hybrid III thorax, lumbar spine and self-aligning steering wheel. The model was developed using DYNA3D and represented the dynamic large deformation response of the system by a combination of solid, beam and shell elements. Both elastic and viscoelastic material properties of various system components were experimentally identified and implemented in the model.
Initially, the accuracy of the individual component was ascertained by comparisons with corresponding experimental data. The predicted midsagittal force-deformation response of the thorax from an impactor with initial velocities: 4.3 and 6.7 m/s, respectively followed closely corresponding corridors derived from dummy and human cadaver tests. Also, the elastic-plastic response of the self-aligning structure in the steering wheel was accurately captured, and compared favorably with test results.
Then, the thoracic impact on the steering wheel was computed for three initial velocities: 6.9, 7.9 and 8.8 m/s. The predicted system kinematics and thoracic and wheel deformation and associated force histories compared well with corresponding mini-sled tests. In addition, the model provided a unique capability for predicting the evolution of the contact force between the thorax and the steering wheel.