Description of the model Sample Clauses

Description of the model. A FE model of the 50th percentile adult human head, developed at the University of Strasbourg by Xxxx et al. [35] under RADIOSS platform and transferred to LS-DYNA (Deck and Xxxxxxxxx [29,30]) and to VPS was called The Strasbourg University Finite Element Head Model (SUFEHM). The main anatomical features includes the scalp, the brain, the brainstem and the cerebrospinal fluid (CSF) represented by brick elements and the skull, the face and two membranes (the falx and the tentorium) modeled with shell elements as shown in Table 3. The SUFEHM presents a continuous mesh that is made up with 13,208 elements (10,395 brick elements and 2,813 shell elements), including 1,797 shell elements utilized to compose the skull and 5,320 brick elements for brain. The total mass of the head model is 4.7 kg which is equivalent to the mass of a 50th percentile adult human head. The geometry of the inner and outer surfaces of the skull was digitized from a human adult male skull to ensure anatomical accuracy. Isotropic, homogeneous and elastic mechanical constitutive material models were applied to each of the SUFEHM parts except for the brain, for which viscoelasticity was assumed. The skull was modeled by a three layered composite shell. The mechanical properties of all parts of SUFEHM head model except the skull are reported in Table 3. The mechanical parameters of the material which models the subarachnoid space has been derived from experimental and numerical head modal analysis. A linear visco-elastic and isotropic law is affected to the whole brain. This law was described by Xxxxxxxx and Xxxxxxxx [34] in terms of relaxation shear modulus as defined in equation below. G(t)  G  G0  G et where G0, G∞ and β represent the short-time modulus, the long-time modulus and the decay constant respectively. Parameters were identified from experimental data on human brain tissue, i.e. in vitro results proposed by Xxxxx and Xxxxxx [40] as well as in vivo based values from Magnetic Resonance Elastography (MRE) published by Xxxxx et al. [36], with following values: G0 = 49.103 Pa, G∞ = 1.62.104 Pa, β = 145 s-1. Parts Face Scalp Brain Brain stem CSF Falx and Tentorium Density [kg/m3] 2500 1000 1040 1040 1040 1140 Young’s modulus [MPa] 5000 16.7 Viscoelastic 0.012 31.5 Poisson’s ratio 0.23 0.42 0.49 0.45 Element type Shell Brick Brick Brick Brick Shell Shell thickness [m] 1x10-2 - - - - Falx=1x10-3 Tentorium= 2x10-3

Description of the model. The Strasbourg University Finite element Neck model was developed by Xxxxx et al. [49]. The neck geometry is based on a living human subject of average size and close to 50th percentile male: [Height: 1.72 m, weight: 72 Kg, age: 33 years]. From a modeling point of view, millimetric scan sections of the subject have been taken. These scanner sections then underwent grey level processing in order to extract the bone part of the cervical column and of the skull. A rough tria mesh in STL format was then constructed. This file was then imported under the Hypermesh meshing software so that the cervical vertebrae have been completely meshed. The cervical vertebrae were modelled using shell elements, the intervertebral discs with bricks elements, the ligaments using spring elements. As far as the lower cervical spine is concerned, the authors have distinguished five types of ligaments: The anterior longitudinal ligament (ALL), the posterior longitudinal ligament (PLL), the flavum ligament (FL), the interspinal ligament (ISL) and finally the capsular ligaments (CL). For the upper cervical spine, we have modelled the posterior common ligament (C2-C0; C2-C1; C1-C0), the atloidien-axoidien anterior ligament, the transverse ligament, the yellow ligament (C2-C1), the transverse axoid ligament, the anterior occipito-atloid ligament, the alar ligament, the posterior occipito- atloidien ligament, capsular ligament C2-C1, capsular ligament Head-C1, membrane tectaria, the median occipito-odontoid ligament as well as the lateral occipito-atloidien ligament as illustrated in Figure 36 The finite element model of the neck system thus defined consists of 498 spring elements, 4308 shell elements, and 947 brick elements (Figure 37). Figure 36. Upper ligamentary system FEM Figure 37. Cervical spine FEM

Description of the model