Development of a human head FE model for the impact analysis using VOXEL approach and simulation for the assessment on the focal brain injury

In this paper, a three-dimensional digital human-head model was developed and several dynamic analyses on the head trauma were conducted. This model was built up by the VOXEL approach using 433 slice CT images (512×512 pixels) and made of 1.22 million paralelepiped finite elements with 10 anatomical tissue properties such as scalp, CSF, skull, brain, dura mater and so on. The numerical analyses were conducted using a finite element code the authors have developed. The main features of the code are 1) it is based on the explicit time integration method and 2) it uses the one point integration method to evaluate the equivalent nodal forces with the hourglass control proposed by Flanagan and Belythcko and 3) it utilizes the parallel computation with the MPI. In order to verify the developed model, the head impact experiment for a cadaver by Nahum et al. was simulated. The calculated results showed good agreement with experimental ones. A front and rear impact analyses were also performed investigate the relation between the impact direction and the positions of the high measurement of pressure and stresses in brain. The obtained results represent that brain injury has a closer relation with the Mises equivalent stress rather than the pressure. At this time, the large deformation of a frontal cranial base was observed in both frontal and occipital impact analyses. We expect that it induces the brain injury in a frontal lobe regardless of the impact positions.