Brain deformation in linear head impact

In this study, a 2D model of the head underwent linear impact and the experiments were simulated by finite element models. A cylinder with a diameter of 100mm and height of 20mm was filled with 5% gelatin, which was used as the brain surrogate material. The physical model was mounted onto a High Speed Computer Controlled Impact System to generate inertial loading of approximately 50 G average deceleration. The deformation of the samples was studied through image processing. Finite element (FE) analysis was used to simulate the experiments. The impact tests were modeled with two methods: a Lagrangian formulation with single point integration and an Arbitrary Lagrangian Eulerian (ALE) formulation with single point integration and void using LS-Dyna FE code. In the model with slip contact, the normal and shear strains reached more than 20% in some regions, which confirmed the risk of axonal injury in the linear impacts applied in this study. It was seen that in the Lagrangian models, in order to stabilize the simulation, high bulk moduli needed to be used; however, this resulted in much smaller void generation in the posterior region of the model. It was shown that the void generation reaches the experimental values by introducing 1-2 mm initial gaps between brain and skull. The ALE model was more stable and less sensitive to the bulk modulus, but showed smaller deformations.