INTRODUCTION Traumatic brain injury (TBI) has led to a large number of both military and civilian injuries and deaths in recent decades [1]. Primary blast injury, a consequence of overpressure resulting from an explosion, is believed to be a main cause of mild-TBI [2]. Almost all significant cases of blast injury include damage to the blood vessels [3]; however, the injury mechanism and mechanics are not fully understood. Computational modeling is a useful tool for investigating complicated blast wave propagation and fluid-structure interactions. The objectives of this study were twofold: (1) to investigate blast wave characteristics as a function of parameters in the LBE (Load Blast Enhanced) method for blast wave simulation and (2) to study how different wave characteristics influence the mechanical response of an isolated blood vessel modeled as a simplified cylinder. Both objectives are preliminary to the development of a more complex model simulating the response of an isolated blood vessel to primary blast exposure, as accomplished in our laboratory. METHODS Computation modeling was accomplished via the finite element solver of LS-DYNA (LSTC). LS-PrePost was used for pre- and post- processing. The computational model included three components: an ambient air layer (ρ = 1.225 kg/m 3 , 0.05 mm  2 mm  2 mm) as the shock wave receptor, an ALE (Arbitrary Lagrangian-Eulerian) air domain (ρ = 1.225 kg/m 3 , 2 mm  2 mm  2 mm) and an isotropic elastic cylindrical solid (ρ = 960 kg/m 3 , E = 10 MPa, υ = 0.45, with radius 0.2 mm and height 2 mm) representing a simplified blood vessel (Figure 1). The cylindrical solid inside the air domain was orthogonal to the centerline of the ambient layer. The LBE method was developed to simulate empirical air blast [4]. The primary variables in LBE are equivalent mass of TNT and the distance between the object and explosive. In the first part of this study, nine blast conditions (all combinations of three mass values, 0.02, 0.1 and 0.2 g, and three distances, 20, 40 and 60 mm) were explored, without the vessel material in place, to investigate relationships between LBE parameters and blast wave characteristics. The small parameter values were chosen to match experimental conditions. Values of peak pressure and positive phase duration were evaluated along the x-axis of the blast, at a depth of 0.52 mm from the front plane. Data were output every 0.001 ms. Figure 1: Schematic illustration of the finite element model. The computational domain consisted of a shock wave receptor (red), an ALE air domain (blue) and a cylindrical solid material (brown). The explosive was located along the centerline orthogonal to the front plane of the shock wave receptor. Three blast waves were subsequently selected to study the influence of wave shape on vessel mechanical response. As shown in Fig. 4 (dashed curves), a the baseline wave had a peak pressure of about 550 kPa and a positive phase duration of approximately 0.07 ms. Two other waves, one with near half the peak pressure and the same duration and one with the same peak pressure but twice the duration, were also investigated. Translational and rotational constraints in all Proceedings of the 11 th International Symposium, Computer Methods in Biomechanics and Biomedical Engineering April 3 - 7, 2013, Salt Lake City, Utah, USA BLOOD VESSEL RESPONSE UNDER VARIOUS BLAST LOADINGS: FINITE ELEMENT SIMULATION ON A SIMPLIFIED CYLINDER Nan-Wei Liu (1), Kenneth L. Monson (1,2) (1) Department of Bioengineering University of Utah Salt Lake City, UT, USA (2) Department of Mechanical Engineering University of Utah Salt Lake City, UT, USA Z Y X