The creation of three-dimensional finite element models for simulating head impact biomechanics

Abstract

NOTATION βDecay factor λ X , λ Y , λ Z X, Y and Z dimension length scale factors C 10 , C 01 Temperature dependent coefficients G 0 Short term shear modulus G ∞ Long term shear modulus t Time Abstract: A new 3 dimensional finite element representation of the human head complex has been constructed for simulating the transient occurrences of simple pedestrian accidents. This paper describes the development, features and validation of that model. When constructing the model, emphasis was placed on element quality and ease of mesh generation. As such, a number of variations of the model were created. The model was validated against a series of cadaveric impact tests. A parametric study (a High/Low study) was performed to investigate the effect of the bulk and shear modulus of the brain and cerebrospinal fluid (CSF). The influence of different mesh densities on the models and the use of different element formulations for the skull were also investigated. It was found that the short-term shear modulus of the neural tissue had the predominant effect on intracranial frontal pressure, and on the predicted Von-Mises response. The bulk modulus of the fluid had a significant effect on the contre-coup pressure when the CSF was modelled using a coupled node definition. Differences of intracranial pressure were reported that show the sensitivity of the method by which the skull is modelled. By simulating an identical impact scenario with a range of different finite element models it has been possible to investigate the influence of model topologies. We can conclude that careful modelling of the CSF (depth/volume) and skull thickness (including cortical/ trabecular ratio) is necessary if the correct intracranial pressure distribution is to be predicted, and so further forms of validation are required to improve the finite element models' injury prediction capabilities.

Reconstruction of real world head injury accidents resulting from falls using multibody dynamics

“…Results obtained could also provide useful input data for more complex models of the human head, such as a finite element (FE) model [26] [27] [28]. This type of model is able to calculate full-field stresses, strains and strain rates in the brain resulting from impact, and would thus theoretically be able to predict more accurately the location and severity of brain injury resulting from impact.…”

Characterization of persistent concussive syndrome using injury reconstruction and finite element modelling

“…The geometry of the model was taken from a male cadaver using medical imaging techniques (Horgan and Gilchrist, 2003). The model includes the scalp, skull, dura, CSF, pia, falx, tentorium, grey and white matter, cerebellum, and brain stem.…”

“…The brain tissue was modelled using a linearly viscoelastic model combined with large deformation theory. The behaviour of this tissue was characterized as viscoelastic in shear with a deviatoric stress rate dependent on the shear relaxation modulus (Horgan and Gilchrist, 2003). Volumetric/hydrostatic compression of the brain tissue was considered elastic.…”

“…The Mooney-Rivlin hyperelastic material model was used for the brain to maintain these properties, in conjunction with a viscoelastic material property in ABAQUS, giving the material a decay factor of β= 145 s -1 (Horgan and Gilchrist, 2003). The hyperelastic law was given by:…”

“…This algorithm allowed no separation of the contacting pia and CSF layers. Modelling of the CSF was done using solid elements with the bulk modulus of water and a low shear modulus (Horgan and Gilchrist 2003;Horgan and Gilchrist, 2004). For the sliding interfaces a friction coefficient of 0.2 was used (Miller et al, 1998).…”