A History of Research and a Review of Recent Developments

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