Approximate Method of Calculating Critical Shock Initiation conditions and run distance to detonation

Abstract

Niiherungsrnethode zur Berechnung der Bedingungen fur die kritische StoRziindung und die Anlaufstrecke bis zur Detonation Ein Naherungsmodell fur den Dmckaufbau hinter der Front einer ziindenden StoBwelle wird entwickelt. Dieses Model1 fiihrt zu dem allgemein verwendeten P2t-Kriterium, wobei der Druckexponent nicht auf den Wert 2 begrenzt ist. Beziehungen fur die Wellenlaufzeit und die Anlaufstrecke bis zur Detonation werden ebenfalls erhalten. Die Anwendung des Modells wird veranschaulicht durch Venvendung von Sprengstoffen, die in der Literatur beschrieben werden. Es wird gezeigt, daB die kritische StoSziindung und die Laufzeit bis zur Detonation in guter Annaherung uber einen weiten Bereich von StoBbedingungen aus Ergebnissen von ein oder zwei relativ einfachen Experimenten schnell bestimmt werden kann. Die Rechenmethode konnte fir verschiedene Anwendungen niitzlich sein. Mkthode d'approximation pour le calcul des conditions critiques d'amorqage par choc et de la profondeur d'amorsageOn propose un modtle d'approximation pour dCcrire la montte en pression derritre le front d'une onde de choc d'amorGage. Ce modtle conduit au crittre P2t gCnCralement utilist, mais dans lequel I'exposant de la pression n'est pas forcCment Cgal ti 2. On obtient Cgalement des relations pour la durCe de parcours de l'onde de choc et pour la profondeur d'amorGage. Les possibilitCs qu'offre le modtle sont illustrees par son application h diffkrents explosifs dCcrits dans la IittCrature. On montre ainsi qu'il est possible, au moyen d'une ou de deux experience relativement simples, de prkvoir rapidement et avec une bonne approximation le seuil critique de 'amorGage par choc et la profondeur d'amorqage pour une large gamme de conditions. Cette mCthode de calcul devrait prtsenter un inter& pour diverses applications. SummaryAn approximate model for pressure buildup behind the front of an initiating shock wave is developed. This model leads to the widely used P't initiation criterion, but the pressure index is not limited to a value of two. Expressions for wave run time and distance to detonation are also obtained. The use of the model is illustrated using explosives widely discussed in the literature. It is shown that critical shock initiation and run distance to detonation can be rapidly estimated to good approximation over a wide range of shock conditions from the results of one or two relatively simple experiments. The calculational method may be useful for various applications. P u t = P't/QOU = E,P, u and U are pressure, particle velocity and propagation velocity of the shock, t is the duration of shock pressure, Qo is ambient charge density, and E, is an experimental constant for

High-Speed Laser-Launched Flyer Impacts Studied with Ultrafast Photography and Velocimetry

“…The ability of an impactor to initiate explosives depends both on shock pressure and shock duration. A P 2 t = constant relation is most commonly used to describe explosives initiation thresholds [45,46], so, for example, the shock pressure must be increased by four if the duration is reduced by two. As we have shown in Fig.…”

Nanoshocks in Molecular Materials

“…It is difficult to explode energetic materials with short duration nanoshocks. The likelihood of initiating an explosive is usually proportional to P 2 τ, where τ is the shock duration, so nanoshock initiation requires higher pressures than the usual explosive initiator, which is ordinarily a microsecond duration shock. As an alternative, very sensitive explosives must be studied.…”

Shock Initiation of Nano-Al + Teflon: Time-Resolved Emission Studies

“…We performed some experiments with 25 μm thick flyer plates, rather than the usual 50 μm flyers, to see the effects of cutting the shock duration in half. Ordinarily one expects the initiation pressure P in to obey the relation , P in n t = constant …”