Walls shock loads, explosions

The loads from external near-surface burst explosions are based on hemispherical surface burst relationships. Peak pressure (P psi) and scaled. impulse Ci/W psi/lb ) are plotted vs. scaled distance (R/W ft/lb ). Roof and sidewall elements, side-on to the shock wave, see side-on loads (P and i ). The front wall, perpendicular to the shock wave, sees the much higher reflected shock wave loads (P and i ). An approximate triangular pressure-time relationship is shown in Figure 5a. The duration, T, is determined from the peak pressure and impulse by assuming a triangular load. Complete load calculations include dynamic loads on side-on elements, the effect of clearing times on reflected pressure durations, and load variations on structural elements due to their size and varying distance from the explosive source. 

In the physical methods the cell walls are destroyed by physical forces, usually by mechanical load. According to one of the most widespread and cheapest methods , the walls are broken through blast-wave impact. To this effect, the blowing gas is removed from the foamed plastic and the material is saturated with a gaseous explosive (e.g. a stoichiometric O /Hj mixture, an air/Hj mixture, acetylene, or atomic oxygen) in a special chamber where blast occurs under a controlled pressure (up to 2 atm). Other physical methods suitable for preparing reticulated foams use a thermal shock or repeated compression cycles. 

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