Finite element analysis of a ram brain during impact under wet and dry horn conditions.

In this study, ram impacts at 5.5 m/s are simulated through finite element analysis in order to study the mechanical response of the brain. A calibrated internal state variable inelastic constitutive model was implemented into the finite element code to capture the brain behavior. Also, constitutive models for the horns were calibrated to experimental data from dry and wet horn keratin at low and high strain rates. By investigating responses in the different keratin material states that occur in nature, the bounds of the ram brain response are quantified. An acceleration as high as 607 g's was observed, which is an order of magnitude higher than predicted brain injury threshold values. In the most extreme case, the maximum tensile pressure and maximum shear strains in the ram brain were 245 kPa and 0.28, respectively. Because the rams do not appear to sustain injury, these impacts could give insight to the threshold limits of mechanical loading that can be applied to the brain. Following this motivation, the brain injury metric values found in this research could serve as true injury metrics for human head impacts.