Generation and Analysis of Blast Waves from a Compressed Air-Driven Shock Tube

Abstract

Shock tubes provide means to investigate blast phenomena without the use of explosives. A literature review has shown that several previously reported shock tubes intended for blast wave injury studies were improperly configured, and specimens were often subject to pressure-time artifacts inherent to the device’s operation, rather than pure blast waves. This paper discusses an open-ended shock tube specially designed for blast injury studies, and develops a methodology and guidelines for conducting blast wave experiments and data analysis. It is shown that locating test articles downstream the axis of the shock tube results in pressure-time data significantly contaminated by venting of operational gases. Venting pressure spikes can produce total impulse an order of magnitude larger than the impulse associated to the intended blast wave, creating an experimental artifact that makes questionable to attribute specimen injury to the blast wave itself. By locating the specimen off-axis the shock tube at various distances away from the exit, pure blast waves with a wide range of peak overpressures, durations, and impulses can be achieved. This paper also presents a methodology for scaling shock tube generated blast wave data to a TNT equivalent.