The objectives of this work are: (1) to characterize the human head dynamic response under shock conditions by a new three-dimensional (3D) finite element model (FEM); and (2) to transfer the results to a physical model intended for "measuring" the shock severity. The proposed 3D FEM distinguishes the different anatomical features of the cerebral matter. Model validation is based on it's theoretical modal analysis compared to the in vivo mechanical impedance recordings of the head. Modal analysis of the model shows three vibration modes. The mode shapes are illustrated by brain rotations around the Z1, Y1-Y'1 and X1 axis. The new proposed physical head model has an internal mass modeling the cerebral mass. The modelling of the mechanical liaisons between the brain and skull was achieved by visco-elastic liaisons. The adjustable elastic component permits 3 degrees of freedom relative to the brain-skull movement (two X, Y translations and the rotation around Z). The resonance frequencies of these three degrees of freedom were fixed by the theoretical modal analysis of the 3D FEM. These new head models are especially suitable for distinguishing the risk of focal lesion or sub-dural haematoma from diffuse axonal injury (DAI) risks. (A)
Samenvatting