Picatinny Arsenal Impact Test Apparatus

Fig 5—2. Parts of Picatinny Arsenal Impact Test Apparatus... 

Figure 3. Picatinny Arsenal impact test apparatus.

More consistent results than some obtained with the B of M machines are obtd with an apparatus used for many years at Picatinny Arsenal(Refs 4,13,15 16). With this machine, known as Picatinny Arsenal Impact Apparatus, samples are tested under confinement aed results are reported In inches. The usual weight hammer is 2 kg for HE s and smaller wts of 1 lbor 8 ox for initiating expls. Fora description of apparatus and procedure, see Refs 13.15 16... 

IMPACT SENSITIVITY OR SHOCK SENSITIVITY TESTS (Drop Weight or Falling Weight Tests). A list of various tests with refs is given in Vol 1, p XVII. Brief descriptions of US Bureau of Mines (BM) Apparatus and of Picatinny Arsenal (PA) Apparatus are also given on p XVII. British test called Figure of Insensitiveness (FI) is described on p XII (See also Refs 36, 38d, 41, 42, 53, 55b,... 

A.J. Clear, "Standard Laboratory Procedures for Determining Sensitivity, Brisance and Stability of Explosives", PATR 3278 (Dec 1965) [Superseding PATR FRL-TR-25 (l )6l] Impact Test with Picatinny Arsenal Apparatus (pp 2-4 and Figs 1, 2, 3 4, pp 32-35) Impact Test with US Bureau of Mines Apparatus (pp 4-7 and Figs 5, 6 7, pp... 

Picatinny arsenal (PA) impact apparatus The sample which is placed in the depression of a small steel die-cup and then capped by a thin brass cover, is used in this test. The value of minimum height at which at least one out of ten trials results in explosion gives impact sensitivity. In the case of liquids, it is filled in a die-cup and tested in a manner similar to solids. 

Both the US B of M and PA Impact Madiines have been used at Picatinny Arsenal for the testing of liquid expls, with a modification in sample handling required only in the case of the BM apparatua(Refs 12a ft 16) Dr Rotter of the Research Dept, Woolwich, England, designed an apparatus and a method of testingfRefa 3 ft 6), which is claimed to be more accurate than other known methods. This is now an official British test and the value obtained is known as Fl(Figure of Insensitiveness) (qv)... 

The effect of temperature on the impact sensitivity of thallous azide is shown in Figure 11. At - 100°C a decrease was obtained when tested with the Picatinny Arsenal apparatus. The results at room temperature indicate that... 

In Chapter 1 different processes of preparing silver azide are described, and the impact sensitivities of samples made by processes are presented in Figure 12. They were tested with the Picatinny Arsenal apparatus and also with the ball-drop apparatus. 

Curve C in Figure 16 indicates that after standing for 24 hr at 65% relative humidity the lead azide reabsorbed moisture and the sensitivity to impact decreased. Current practice is to vacuum dry primary explosives at 60°C for 24 hr prior to impact testing with the Picatinny Arsenal apparatus. 

If liquids act as thermal sinks to desensitize explosives, liquid nitrogen might be presumed to maximize the effect. Tests using a Picatinny Arsenal apparatus modified with the addition of a holder for the nitrogen indicate that of the primaiy explosives tested only dextrinated lead azide displays a decrease in impact sensitivity (Table VIII) [57]. 

Figure 19. Impact tests of lead azide and lead azide with different liquids [56] Picatinny Arsenal apparatus 1-kg weight dropped at indicated heights 20 samples per data point.

The increased sensitivity of confined, wet mixtures of lead azide led to tests with unconfined samples [57], An earlier investigation [58] indicated that wet lead azide is more sensitive to impact tlian the dry substance when measured on the Naval Surface Weapons Center ERL machine. The Picatinny Arsenal apparatus was modified to reduce the confinement of the sample by introducing a well to retain the sample in relatively large amounts of liquid. 

The impact sensitivity of DBX is slightly less than that of TNT 10 inches on the Picatinny Arsenal apparatus versus 14 inches for TNT. In the rifle bullet impact test about 49 percent of the samples exploded from the impact of a 30 caliber bullet at a distance of 2,743 meters (90 feet). The five second explosion test value is 200°C. The minimum detonating charge is 0.20 grams of lead azide and 0.10 grams of tetryl. 

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