A History of Research and a Review of Recent Developments
A History of Research and a Review of Recent Developments
A History of Research and a Review of Recent Developments
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130<br />
Pressure measurement <strong>and</strong> blast simulation<br />
Figure 6.6 Shock tube driven blast simulator, Reiter Alpe, Germany (from<br />
Ackerman <strong>and</strong> Klubert, ref. 6.27).<br />
0.4 m 3 , <strong>and</strong> is safe to 200 bar. The diaphragms are made from hardboard <strong>and</strong><br />
fired by plastic explosive. The structure testing area is about 50 m from the<br />
battery <strong>of</strong> driver tubes, but experiments showed that at this point the side-on<br />
pressure/time relationship is not ideal. A sharp instantaneous pressure rise is<br />
followed by exponential decay, but then there is another sudden pressure increase<br />
lasting for 50 msec. Because <strong>of</strong> this pressure increase the reflections from the<br />
walls overlap the blast wave <strong>and</strong> subsequent exponential decay suddenly ends<br />
after a time <strong>of</strong> 300 msec. During the early stages <strong>of</strong> use a 0.8 bar shot resulted in<br />
damage to the walls <strong>and</strong> ceilings <strong>of</strong> local village houses.<br />
Another blast simulator embedded in rock was constructed in the mid-<br />
1960s at the Swedish fortifications establishment Fort F, Eskilstuna, Sweden.<br />
It has been fully described by Bergman [6.28], <strong>and</strong> consists <strong>of</strong> an explosion<br />
chamber, test chamber <strong>and</strong> exhaust tunnels, as shown in Figure 6.7. Hexotol<br />
charges up to 100 kg in weight can be detonated in the explosion chamber,<br />
which give peak gas pressures <strong>of</strong> up to 6 or 7 kPa. The pressure wave passes<br />
through a diffuser which reduces the ‘spikes’ in the wave form, <strong>and</strong> it then<br />
dynamically loads the test specimen. The gas is then gradually evacuated by<br />
regulating the size <strong>of</strong> the entrance to the exhaust tunnel, <strong>and</strong> by this means the<br />
duration <strong>of</strong> the pressure pulse can be controlled. The main tunnel is square in<br />
cross section (2.1 m sides) <strong>and</strong> has a total length <strong>of</strong> 220 m. As Figure 6.7<br />
shows, the tunnel eventually discharges to atmosphere through a muzzle system.<br />
By disconnecting the exhaust loop, removing the diffuser <strong>and</strong> emptying the<br />
test section <strong>of</strong> equipment, a straight shock tube is obtained. The gas flow<br />
from the entrance can then load large military objects placed on level ground