Shock tube design for high intensity blast waves for laboratory testing of armor and combat materiel

Abstract

Shock tubes create simulated blast waves which can be directed and measured to study blast wave effects under laboratory conditions. It is desirable to increase available peak pressure from ~1 MPa to ~5 MPa to simulate closer blast sources and facilitate development and testing of personal and vehicle armors. Three methods were investigated to increase peak simulated blast pressure produced by an oxy-acetylene driven shock tube while maintaining suitability for laboratory studies. The first method is the addition of a Shchelkin spiral priming section which works by increasing the turbulent flow of the deflagration wave, thus increasing its speed and pressure. This approach increased the average peak pressure from 1.17 MPa to 5.33 MPa while maintaining a relevant pressure-time curve (Friedlander waveform). The second method is a bottleneck between the driving and driven sections. Coupling a 79 mm diameter driving section to a 53 mm driven section increased the peak pressure from 1.17 MPa to 2.25 MPa. Using a 103 mm driving section increased peak pressure to 2.64 MPa. The third method, adding solid fuel to the driving section with the oxy-acetylene, resulted in a peak pressure increase to 1.70 MPa.

Blast-Associated Shock Waves Result in Increased Brain Vascular Leakage and Elevated ROS Levels in a Rat Model of Traumatic Brain Injury

“…Broadly categorized, shock tubes employ either expansion of compressed gases, deflagration of gas fuels, or detonation of explosives to generate a pressure wave [ 31 , 32 ]. Often, a performance goal of a shock tube generator is a Friedlander waveform, a pressure-time curve characteristic of an explosion in free field, with no proximate surfaces interacting with the wave [ 21 ].…”

“…In compression-driven shock tubes, the initial shock wave is followed by a second pressure wave due to what is sometimes called the “jet effect” of expanding gases following the shock front. This jet effect applies a second loading to the animal transferring additional momentum, thus possibly inducing injury via mechanisms not corresponding to real blast loading [ 31 ]. Compression-driven shock tube designs are also known to create longer pressure durations which are often not observed in realistic scenarios.…”

An Optical Measurement System to Measure Velocity and Provide Shock Wave Pressure Diagrams

“…Pressure in the high-pressure area depends on the thickness and material of the diaphragm. By increasing the pressure of the driver and the instant rupture of the diaphragm, the shock wave is generated [2]. This increase is achieved by a variety of methods including explosion [3,4], combustion [5], or highpressure gas tank [6,7].…”

Note: Device for underwater laboratory simulation of unconfined blast waves

“…This approach employs a Shchelkin spiral priming section which increases the turbulent flow of the deflagration wave, thus increasing its speed and pressure, facilitating a deflagration to detonation transition (DDT).The priming section is coupled to an underwater tube oriented vertically in the water so the simulated blast wave moves outward from the center. Since blast waves decrease with distance, this geometry allows experimenters some control over blast exposure levels for testing injury thresholds in marine life and underwater blast transmission, and also for testing computational models, candidate armor materials, and other mitigation strategies.A 30.5 cm long 2.54 cm diameter polyethylene tube with a wall thickness of about 0.07 mm was secured over the end of the priming section, and both were filled with a stoichiometric mixture of oxygen and acetylene following the method of Courtney et al 11 Reaction of the oxyacetylene mix was initiated by an impact to the priming compound. The priming section was a 60.7 cm long and 16 mm inner diameter machined steel tube with grooves of a depth of 0.36 mm, as in Courtney et al 11 Figure 1 illustrates the experimental arrangement.…”

“…Previous work showed that a modular, oxy-acetylene based shock tube produced realistic blast waves in air 8 with peak pressures up to about 5 MPa. 11 High blast pressures are desirable to more accurately simulate pressures created by underwater explosions. 3 The present study investigates a new approach to simulating underwater blast waves with an oxy-acetylene based device.…”