Experimental and Analytical Studies of Blast Wave Effects on Major Organ Systems of the Body
Evidence of acute nonauditory injury in animals from intense blast overpressure (BOP) exposure and the possibility of chronic injury from BOP in the crew area of conventional weapons has prompted the need for detailed biomechanical models to assist the U. S. Army in defining damage risk criteria (DRC) for humans. The methodology uses mathematical models and computer codes to construct a causal, verifiable connection between the external blast environment and the local tissue stresses. Direct, in vitro observation of the damage process and measurement of the tissue strength leads to the determination of critical stress thresholds for damage that define the mechanical conditions producing injury.
Load distribution on a torso model exposed to blast waves of 3–30 psi peak pressure were used to validate gas dynamics calculations of the blast-body interaction and to develop a preliminary blast load relationship. A finite element model (FEM) of the thorax cross section of the sheep has been constructed and parametric calculations varying the material properties has revealed that the only sensitive quantities are the density and compressibility of the lung parenchyma and the effective shear modulus of the thoracic cavity. All of the material properties of the lung required for the thorax model have been measured for a variety of species and the ability of the lung parenchyma to support a low speed compression wave has been directly observed. Comparison of the FEM predictions against the currently available animal data on intrathoracic pressure response have been satisfactory and the variation of ITP under iso-impulse conditions agrees well with data.
A perfusion technique has been developed that allows in vitro investigation of the mechanical origins of injury to the gastrointestinal tract. The results strongly point to the role of local gas bubbles in the gut sections that lead to large motions and stresses in the neighboring gut walls and eventually cause injury.
KeywordsFinite Element Model Blast Wave Blast Loading Blast Injury Effective Shear Modulus
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