Biomechanical Assessment of Brain Dynamic Responses Due to Blast Pressure Waves

Abstract

A mechanized and integrated computational scheme is introduced to determine the human brain responses in an environment where the human head is exposed to explosions from trinitrotoluene (TNT), or other high-yield explosives, in military applications. The procedure is based on a three-dimensional (3-D) non-linear finite element method (FEM) that implements a simultaneous conduction of explosive detonation, shock wave propagation, blast-head interactions, and the confronting human head. The processes of blast propagation in the air and blast interaction with the head are modeled by an Arbitrary Lagrangian-Eulerian (ALE) multi-material FEM formulation, together with a penalty-based fluid/structure interaction (FSI) algorithm. Such a model has already been successfully validated against experimental data regarding air-free blast and plate-blast interactions. The human head model is a 3-D geometrically realistic configuration that has been previously validated against the brain intracranial pressure (ICP), as well as shear and principal strains under different impact loadings of cadaveric experimental tests of Hardy et al. [Hardy W. N., C. Foster, M. Mason, S. Chirag, J. Bishop, M. Bey, W. Anderst, and S. Tashman. A study of the response of the human cadaver head to impact. Proc. 51 ( st ) Stapp. Car Crash J. 17-80, 2007]. Different scenarios have been assumed to capture an appropriate picture of the brain response at a constant stand-off distance of nearly 80 cm from the core of the explosion, but exposed to different amounts of a highly explosive (HE) material such as TNT. The over-pressures at the vicinity of the head are in the range of about 2.4-8.7 atmosphere (atm), considering the reflected pressure from the head. The methodology provides brain ICP, maximum shear stresses and maximum principal strain within the milli-scale time frame of this highly dynamic phenomenon. While focusing on the two mechanical parameters of pressure, and also on the maximum shear stress and maximum principal strain to predict the brain injury, the research provides an assessment of the brain responses to different amounts of over-pressure. The research also demonstrates the ability to predict the ICP, as well as the stress and strain within the brain, due to such an event. The research cannot identify, however, the specific levels of ICP, stress and strain that necessarily lead to traumatic brain injury (TBI) because there is no access to experimental data regarding head-blast interactions.

A constitutive model for ballistic gelatin at surgical strain rates

“…The material characterisation of ballistic gelatin presented here can find application in in situ studies that employ the material in physical phantoms (such as of breast, liver or brain) for surgical training (Malekzadeh et al (2011)) or evaluation of traumatic brain injuries, and in in silico studies investigating computational models of such processes (Chafi et al (2010)). The constitutive model and optimised material parameter values indicate that ballistic gelatin has similar properties to soft tissues in general, which is encouraging for its use as a soft tissue simulant.…”

Brain Tissue Constitutive Material Models and the Finite Element Analysis of Blast-Induced Traumatic Brain Injury

“…Hence, the second Piola-Krichho stress can be obtained by utilizing the convolution integral (Eq. (11)) [1]:…”

“…Experimental methods impose moral and technical issues before conducting any research. Many FE studies have been conducted to determine brain responses under dynamic loads to study TBIs [1][2][3][4][5][6][7][8][9][10]. Such studies have helped to e ciently develop TBI prediction tools based 1 on the current injury threshold criteria of kinematics, intracranial pressure (ICP), tissue strain, and tissue shear stress [11].…”

Blast and the Consequences on Traumatic Brain Injury-Multiscale Mechanical Modeling of Brain

“…Sections of the head model; the right half of the head model is shown with the brain, the meningeal layers (dura mater with falx and tentorium) and the scalp and skull separated. [9,11] …”