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The effect of the explosive binder 5 w/o‐Kel‐F‐800 on the initiation threshold sensitivity of LX‐15 had been measured. The initiation threshold (kinetic energy of flyer plate) versus explosive grain size shows constant difference of 5.5 ± 0.5 J/cm2 between threshold curves of HNS and LX‐15 explosives (HNS plus 5 w/o‐Kel‐F‐800). This result can be explained by hot spots model.

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Die Ziindschwellenempfindlichkeit des Sprengstoffs HNS in Abhangigkeit von seiner KorngroBeDie Ziindschwellenempfindlichkeit von HNS wurde in Abhiingigkeit von der KorngroBe gemessen unter Venvendung einer elektrischen Kanone bei zwei Plattendicken. Die Ziindschwelle (kinetische Energie der Flugplatte) in Abhangigkeit von der KorngroRe zeigt, daR die Grenzwertkurve drarnatisch ansteigt bei einer KorngroRe groBer als 5,4 pm (bei einer Plattendicke von 76,2 prn und Sprengstoffdichte von 1,6 g/cm3). Die Mindestwerte fur die kritische Energie wurden berechnet zu 12,15 & 0,5 J/cm2 bei einer Plattendicke von 76,2 pm bzw. zu weniger als 7,O J/cm2 bei einer Plattenmcke von 20,O pm. SummaryThe initiation threshold sensitivity of HNS versus explosive grain size has been measured, using an electric gun, with two flyer thicknesses. The initiation threshold, (kinetic energy of flyer plate), versus explosive grain size shows that the threshold curve increases dramatically at grain size over 5.4 prn (for flyer thickness 76.2 urn at explosive density 1.6 g/cm3). Minimum critical energies were calculated to be 12.15 f 0.5 J/crn2 and less than 7.0 J/cm2, for flyer thicknesses 76.2 pm and 20.0 prn, respectively. Variation du seuil de sensibilitC a I'amorqage de l'hexanitrostilbkne en fonction de sa granulomitrie On a analysC I'influence de la granulomitrie de l'hexanitrostilbkne sur son seuil de sensibilitC ? I 1'arnorGage i i l'aide d'un canon Clectrique en utilisant deux diffkrentes Cpaisseurs de clinquant. L'tvolution du seuil d'amoqage (Cnergie cinktique de la plaque projetCe) en fonction de la granulomitrie montre que la sensibilite croit considCrablement, dks que la taille des grains dkpasse 5,4 pm (pour un clinquant de 76,2 pm d'Cpaisseur et une masse volumique de I'explosif de 1,6 g/ crn3). Les valeurs minimales pour I'Cnergie critique, fournies par le calcul, sont de 12,lS ? 0,5 J/cm2 pour une Cpaisseur de clinquant de 76,2 prn et de moins de 7,O J/cmZ pour une Cpaisseur de clinquant de 20,O prn.The explosive HNS was prepared by method described in Refs. 6 and 7 . We developed a recrystallization method of controlling the distribution of particle sizes around the mean value required grain size. Two batches were prepared at different times in order to prove the constitency of the recrystallization method. The values of each particle size were measured by Hiac Particle Size Analyzer -PA-770, and summarized in Table 1. In Figs. l a , l b , we show typical examples of HNS with different grain sizes as were detected by SEM (Scanning Electronic Microscope).

The shock initiation threshold of HNAB (Hexanitroazobenzene) explosive has been measured using pressure pulses generated by flyer plate impact. The flyer plates were accelerated by an electrically exploded metallic foil (electric gun) up to velocity of 2.5 mm/m̈s generating impact pressures, P, up to 7.3 GPa lasting between τ = 40 ns to 210 ns, where τ is the duration of the impact. One dimensional semi‐empirical model was developed to describe the exploding foil process. We found a good agreement between the semi‐empirical model and the experimental data. It was found that as the pressure duration gets longer, the initiation threshold curve swings away from the P2τ= constant. For long (200 ns) pulses, the initiation criterion becomes one of a constant pressure. This constant threshold pressure is 2.9 GPa at 1.6 g/cm3 (grain size is 5 m̈m). The effect of the explosive density and grain size on initiation threshold can be explained by hot spots and porous explosive concept. A critical energy for initiation threshold of 12 J/cm2 was derived from our measurements (with flyer thickness 76 m̈m and grain size 5 m̈m).