Blast simulator considerations for testing symmetrical specimens

An increasing number of studies use blast simulators to assess blast exposure as a potential mechanism for traumatic brain injury, post-traumatic stress disorder, and tissue damage to the eye and ear. However, the small diameter of many blast simulators limits specimen size, and it is often not feasible to test a full-scale dummy or cadaver head. It has been suggested that a plane of symmetry could be used to model realistic boundary conditions for a smaller portion of a symmetrical object. Therefore, test fixtures that occluded either 10% or 20% of the cross-sectional area of the tube were tested with and without a plane of symmetry to assess the effect of object size and the plane of symmetry. Static pressure along the tube wall and reflected pressure on the surface of the fixture were measured. Each test was conducted in duplicate at 70 kPa, 140 kPa, and 210 kPa to simulate survivable, but increasingly severe blasts. Tests with the plane of symmetry produced pressure traces that more accurately simulated idealized Friedlander waveforms. Peak overpressure and positive duration were similar in magnitude for both the 10% and 20% occlusion fixtures when the plane of symmetry was used. Future studies using blast simulators to test large, symmetrical specimens such as the human head should consider using a POS and limiting occluded area to <;20% to accurately model the in vivo response to blast overpressure.