The brain is modeled with Neo-Hookean hyperelasticity. The Neo-Hookean form of strain energy potential is given by:
where:
 = strain energy per unit reference volume |
 = first deviatoric strain invariant |
 = initial shear modulus of the material |
 = material incompressibility parameter |
 = determinant of the deformation gradient  |
The following input defines Neo-Hookean hyperelasticity:
tb,hyper,1,,,NEO tbdata,1,3000,0.005
The following input specifies isotropic brain permeability:
fpx=4.8e-8 tb,pm,1,,,perm tbdata,1,fpx,fpx,fpx
The following input assignes a Biot coefficient of 1.0 to the brain:
tb,pm,1,,,biot tbdata,1,1.0
Thermal effects are considered:
| Brain Thermal Properties | |
|---|---|
| Coefficient of thermal expansion (/ °C) | 4.14E-5 |
| Density (kg/m-3) | 900 |
| Thermal conductivity (W / °C) | 500 |
| Specific heat (J / kg °C) | 3000 |
The thermal properties are assigned via the following input:
mp,alpx,1,4.14e-5 mp,reft,1,0 mp,dens,1,900 tb,therm,1,,,cond tbdata,1,500 tb,therm,1,,,spht tbdata,1,3000