BTG Research developed laboratory scale shock tubes in diameters from 7.6 mm to 79 mm that can reliably apply shock waves with realistic blast wave profiles to small areas of a test subject or candidate armor material. By varying the geometry of the driving section and the placement of the sample, a range of peak pressures and positive pulse durations can be applied.
The prevalence of blast induced traumatic brain injury in recent conflicts has motivated laboratory scale experiments on biomedical effects of blast waves and studies of blast wave transmission properties of various materials in hopes of improving armor design to mitigate these injuries. Many currently employed shock tube designs have limitations such as significant shot to shot variations in peak pressure, pressure durations longer than typically encountered from real threats (antipersonnel mines, hand grenades, improvised explosive devices), and waveforms that do not accurately represent the Friedlander waveform of free-field blast waves. Blast-driven shock tubes generate more realistic loading profiles but require facilities and personnel certified to store and work with explosive materials. Currently available compression-driven and blast-driven shock tube designs are also expensive to build.
The table top and modular, oxy-acetylene driven shock tubes developed at BTG Research are economical to build and operate and generate reproducible, relevant pressure-time profiles. The design and characterization of these shock tubes has been described in some detail so that other research groups can implement similar systems. These shock tubes are expected to be useful for comparing the blast transmission properties of various materials, quantifying the response of biological materials and animal models to blast injury, characterizing the behavior of various sensors to blast rates of loading, characterizing material properties at blast rates of loading, and providing experimental data for input to mathematical models of blast wave interactions with structures.
The figure at left shows an example of peak pressure and positive pulse duration achieved by adjusting the driver parameters for a 51 mm diameter shock tube. The figure at center shows the change in peak with distance from the opening of the shock tube for several driver/driven section combinations (solid symbols are experimental data; lines are the results of an analytical model fit to each data set).
Oxy-acetylene driven laboratory scale shock tubes for studying blast wave effects.
Development and characterization of laboratory scale shock tubes for studies of blast wave effects.
A table-top blast driven shock tube.