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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6<br />
Pressure measurement <strong>and</strong> blast<br />
simulation<br />
6.1 EXPERIMENTAL PRESSURE MEASUREMENT<br />
The accurate measurement <strong>of</strong> dynamic loads on structures is a dem<strong>and</strong>ing<br />
subject, not least in that the measuring apparatus should not interfere with<br />
the load distribution it is trying to measure. The physical properties <strong>of</strong> blast<br />
waves as they strike the structure are most commonly recorded in terms <strong>of</strong><br />
pressure, <strong>and</strong> the design <strong>and</strong> use <strong>of</strong> pressure gauges (or transducers) suitable<br />
for recording the history <strong>of</strong> blast wave pressure is an important aspect <strong>of</strong><br />
structural loading research.<br />
What are referred to as side-on gauges have been frequently used for blast<br />
measurement over the years. Sensing elements are mounted in housings which<br />
are contoured to <strong>of</strong>fer minimum resistance or disruption <strong>of</strong> natural forces. All<br />
types <strong>of</strong> side-on gauge are unidirectional, <strong>and</strong> most use piezo-electric materials<br />
that respond to pressures on their surface. Natural materials <strong>of</strong> this type are<br />
tourmaline or quartz, <strong>and</strong> there are several synthetic materials <strong>of</strong> which lead<br />
zirconate is a good example. Piezo-electric devices have a linear response over<br />
a good pressure range, but are inclined to brittleness <strong>and</strong> will not measure<br />
statically applied loads. Considerable development <strong>of</strong> side-on blast pressure<br />
gauges, using stacks <strong>of</strong> piezo-electric discs placed in a streamlined housing,<br />
has taken place over the years in the USA, particularly at the Ballistics <strong>Research</strong><br />
Laboratory <strong>and</strong> certain research laboratories <strong>and</strong> institutes. These developments<br />
have been described by Baker [6.1], <strong>and</strong> Figure 6.1, taken from his study,<br />
shows diagramatically the BRL side-on blast gauge (or gage). Even numbers<br />
<strong>of</strong> piezo-electric discs were interleaved with metal foil discs, <strong>and</strong> set so that<br />
there was alternate polarity. All discs <strong>of</strong> one polarity were connected via tabs<br />
to an insulated electrical lead, <strong>and</strong> discs <strong>of</strong> the opposite polarity were earthed<br />
(or grounded) to the metal <strong>of</strong> the housing. The diameter/thickness ratio <strong>of</strong> the<br />
complete gauge was greater than 10:1 to minimize the effect <strong>of</strong> the gauge<br />
pr<strong>of</strong>ile on blast flow. The diameter <strong>of</strong> the housing was rather large, <strong>and</strong> a more<br />
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