Effects of Head Size and Morphology on Dynamic Responses to Impact Loading

Head responses subjected to impact loading are studied using the finite element method. The dynamic responses of the stress, strain, strain energy density and the intracranial pressure govern the intracranial tissues and skull material failures, and therefore, the traumatic injuries. The objectivity and consistency of the prevailing head traumatic injury criteria, i.e., the energy absorption, the gravity centre acceleration and the head injury criterion (HIC), are examined with regard to the head dynamic responses. In particular, the structural intensity (STI) (the vector representation of energy flow rate) is calculated and discussed. From the simulations, the STI, instead of the gravity centre acceleration, the HIC and the energy absorption criteria, is found to be consistent with the dynamic response quantities. The different local skull curvatures at impact have a marginal effect whereas the locations of the impact loadings have significant effects on the dynamics responses or the head injury. The STI also shows the failure patterns. In the first attached figure, the varying local curvatures at the frontal and side impact locations are shown, which was to investigate the different morphology effect on the dynamic responses of the head. In the other figure, the different morphology effect and head size effect are demonstrated. The legend in this figure can be interpreted as that the first letter (F or S) stands for the frontal or side impact location, the second letter or number represents the different morphology state or the head size. For example, S_s stands for the impact case of side impact with head size 15% smaller than that of the average adult head, while F_m1 is the case of frontal impact with the local curvature morphology state of m1.