Evaluation of Head Response to Blast Using Sagittal and Transverse Finite Element Head Models

• Main Authors: Singh, Dilaver, Cronin, Duane S, Lockhart, Philip A, Haladuick, Tyler N, Bouamoul, Amal, Dionne, Jean-Philippe
• Format: Report
• Language: English
• Subjects: ALE MESHES; ALE(ARBITRARY LAGRANGIAN EULERIAN); Anatomy and Physiology; BLAST; BRAIN; Explosions; FINITE ELEMENT ANALYSIS; FOREIGN REPORTS; HEAD(ANATOMY); IMPROVISED EXPLOSIVE DEVICES; KINEMATICS; MATHEMATICAL MODELS; Numerical Mathematics; PRESSURE; PRESSURE WAVE DYNAMICS; SAGITTAL MODELS; TISSUES(BIOLOGY); TRANSVERSE MODELS; TRAUMATIC BRAIN INJURIES; WAVE PROPAGATION

Blast injuries associated with exposure to Improvised Explosive Devices (IEDs) are becoming increasingly important in modern military conflicts, with mild traumatic brain injury (mTBI) reported as a significant incidence. Unlike automotive impacts, blast injuries are dominated by pressure wave dynamics, so appropriate finite element models need elements small enough to accurately model wave propagation. Although three-dimensional effects are important, the associated required mesh size results in a computationally prohibitive model. To address this, two fully coupled three dimensional slice blast-head models, in the sagittal and transverse planes, were developed using solid hexahedral elements. The head models were developed using geometry from the Visible Human Project, and were embedded in an Arbitrary Lagrangian Eulerian (ALE) mesh to simulate the surrounding air. Blast loads corresponding to 5 kg C4 at 3, 3.5, and 4 m standoffs were simulated by applying the expected pressure wave curve to the ALE mesh as a boundary condition. The brain tissue was treated as a homogeneous continuum and modeled using a linear viscoelastic constitutive model. The models were also investigated with an idealized inviscid brain material to provide an upper bound on expected strains in brain tissue. The predicted peak accelerations in both the sagittal and transverse models were in good agreement with comparable physical tests on surrogate heads, although somewhat overpredicted at the 4 m standoff. Maximum intracranial pressure values for the sagittal and transverse models were significant, ranging from 170 400 kPa and 200 300 kPa for sagittal and transverse models respectively. In general, both models reported principal strains lower than those reported for automotive crash scenarios (0.2+). However, the strain rates were on the order of 500 s-1, significantly greater than rates observed in automotive models (10-100 s-1). Prepared in collaboration with the University of Waterloo, Waterloo, ON, Canada, and the Allen Vanguard Corporation, Ottawa, ON, Canada.