Shock wave attenuator pressure

I. Jaffe et al, "Determination of Shock Pressure Required to Initiate Detonation of an Acceptor in the Shock Sensitivity Test , ARS-J 32, 22-25 (1962). In experiments performed at NOL by Jaffe et al, the assembly shown in Fig 3 was used to measure the attenuation of a shock wave in a Lucite rod. The shock wave was initiated by a... 

Another favored test for the past few years has been a form of gap testing, usually cards, whereby the explosive stimulus necessary to initiate the material to detonation is determined. Again, as for impact testing, the results are presented in terms of inches or numbers of cards which attenuate the donor shock wave to non-initiation. The results are much more valuable if expressed in terms of the minimum initiation pressure necessary to initiate the system since a quantitative assessment... 

The minimum shock wave pressure that causes complete detonation of the explosive under test is a measure of shock sensitivity of the explosive and is determined with the help of a gap test . The principle of this test is to subject the explosive under test to the action of a shock wave of known pressure generated by means of a calibrated donor charge and a shock wave pressure attenuator. 

Attenuation of shock waves in air as a function of distance was detd by R.G.Stoner W.Bleakney, JApplPhys 19, 670-8(1948) CA 42, 8475(1948). They measured the velocity of propagation produced on expin in air of chges TNT or 50/50 Pentolite 1.45 to 8 lb (either spherical or cylindrical in shape) and then caled peak pressures by applying the velocity-pressure relation derived from the Rankine-Hugoniot equations... 

In all the techniques described here, it is assumed that the shock wave is plane and parallel to the wedge-and-attenuator interface. The initial shock and particle velocity vs pressure in the wedge are obtained from a graphical solution involving the wedge density, early average shock velocity, and pressure in the... 

Calculated results on shock wave loading of different inert barriers in a wide range of their dynamic properties under explosion on their surfaces of concrete size charges of different explosive materials in various initial states were obtained with the use of the one-dimensional computer hydrocode EP. Barriers due to materials such as polystyrene, textolite, magnesium, aluminum, zinc, copper, tantalum or tungsten were examined (Fig. 9.35). Initial values of pressure and other parameters of loading on the interface explosive-barrier were determined in the process of conducted calculations. Phenomena of propagation and attenuation of shock waves in barrier materials were considered too for all possible situations. 

We saw that the rarefaction traveling axially into the rear of the shock pulse in an explosive can attenuate the peak shock pressure, and thereby cause longer than ideal run distance or even cause detonation failure. Rarefactions traveling radially into the sides or edges of the impact shock wave can do the same. 

The amplified signals are recorded on a raster pattern upon which timing marks have been superimposed. Although an ideal shock wave would display a constant velocity, a real shock wave is usually attenuated with respect to its velocity. This non-ideal behaviour must be recorded in order to make corrections to the calculation of the density, pressure, and temperature of either the incident or reflected shock zones. 

The desired shock wave pressure may be obtained using different combinations of boosters and attenuators. Some examples are given in Table 2.10. 

Booster (25.4 mm thick Attenuator Shock wave pressure, MPa ... 

It should be mentioned that it is necessary to find out the relationship between the attenuator thickness and the transmitted shock wave pressure by prior tests. Some of the tests described in Section 5.9 may be applied for this kind of measurement. 

The gap test enables the determination of the minimum shock wave pressure that can cause complete detonation of the tested explosive. The explosive to be tested is subjected to the action of the shock wave of a known pressure. Such wave is generated by means of a booster and a shock wave pressure attenuator. Whether or not the shock wave caused the complete detonation of the explosive can be concluded on the basis of the mechanical effects produced after the detonation of the explosive hole cutting in a steel plate, dent depth in a witness steel block, or compression of a copper cylinder. 

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