Bulletin of the American Physical Society
2005 14th APS Topical Conference on Shock Compression of Condensed Matter
Sunday–Friday, July 31–August 5 2005; Baltimore, MD
Session J2: Detonations & Shock-Induced Chemistry III |
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Chair: Richard Dick, Air Force Research Laboratory Room: Hyatt Regency Constellation C |
Tuesday, August 2, 2005 11:00AM - 11:15AM |
J2.00001: Analysis of VOD-diameter data using an analytical two-dimensional non-ideal detonation model Sek Chan, Ian Kirby An analytical two-dimensional detonation model is described that has successfully used experimental VOD-diameter data to determine the ignition and growth behaviour of a highly non-ideal explosive. The model is based on a first order approximation of two-dimensional cylindrically symmetric steady state ZND detonation theory. A new ignition and growth model describes the kinetics. Previous analytical methods for analysing highly non-ideal explosives have used quasi-one dimensional models that determine the curvature of the shock front on the axis, and then require empirical relationships to determine the charge diameter. Consistency checks, and comparison with a hydrocode, suggest that the inaccuracies introduced by the first order approximations and assumptions of the model cause overall errors of less than 10{\%}. The model was verified by a series of experiments on an emulsion explosive. Data on detonation velocity, particle velocity and shock front curvature, as a function of charge diameter, were measured in these experiments. It is shown that three parameters defining the ignition and growth are both necessary and sufficient for matching to the experimental VOD-diameter data. The model uses these parameters to predict the shock front and particle velocity profiles, both of which agree with the experimental data to within the estimated errors. [Preview Abstract] |
Tuesday, August 2, 2005 11:15AM - 11:30AM |
J2.00002: Additional Information Showing That a Cylinder's Material and Geometry Affect Measuring an Explosive's Gurney Velocity Joseph Backofen In 2001, the thickness and properties of aluminum, steel, and copper cylinders were shown to affect the Gurney Velocity and Gurney Energy measured for Comp B explosive. This new work confirms the effects described in 2001 using experimental data for four additional explosives in cylinders of these and two more materials. The experimental data show a clear dependence between geometry, materials, and explosives. A new formula provides a relationship between an explosive's detonation rate and its Gurney Velocity as a function of cylinder and explosive geometry and densities. [Preview Abstract] |
Tuesday, August 2, 2005 11:30AM - 11:45AM |
J2.00003: Electromagnetic Radiation From The Detonation of Metal Encased Explosives William Brown, Mark Schmidt, Peter Dzwilewski, Timothy Samaras Electromagnetic radiation accompanying the detonation of chemical explosives was first reported in 1954. Such emissions result from detonations of both bare and cased explosives. However, the dominant wavelengths of emissions from these two types of explosions generally differ by as much as three or four orders of magnitude. We present results of far-field and near-field experimental measurements of electric fields emitted by metal encased explosives, and show that metal fracture is the dominate mechanism leading to these emissions. Additionally, we present results of computational analysis of explosive fracture of steel cylinders performed to investigate the correlation between the time-dependent fragment size distribution and the pattern of electromagnetic emissions. This work supported by the Defense Threat Reduction Agency under contract DTRA01-01-C-0033. [Preview Abstract] |
Tuesday, August 2, 2005 11:45AM - 12:00PM |
J2.00004: An Analytic Model of Close-Range Blast Fragment Loading Ernst Rottenkolber, Werner Arnold The effects of blast-fragmentation warheads need to be carefully characterized in a variety of applications like passive and active vehicle protection or hard target defeat and TBM defense. With these applications in mind, we have developed a collection of tools called FI-BLAST (\textbf{F}ast \textbf{I}nterface for \textbf{B}last-Fragment \textbf{L}oad \textbf{A}nalysis of \textbf{St}ructures). In the present paper we describe the essential part of these tools, namely the close range blast-fragment model. The meaning of ``close range'' is here defined as the standoff to a charge at which blast effects can inflict serious damage on massive structures. In order to quantify our model's range of validity, examples of measured and calculated momentum of bare and confined charges are given in the present paper. Short (L/D = 0.5) and long (L/D = 5) cylindrical charges are included as well as spherical charges. The presented examples demonstrate that the model gives reasonable results in the intended domains of application. [Preview Abstract] |
Tuesday, August 2, 2005 12:00PM - 12:15PM |
J2.00005: On the origin of a maximum pressure peak on the target outside of the stagnation point upon normal impact of a blunt projectile and with an underwater explosion Alexander Gonor, Irene Hooton Impact of a rigid projectile (impactor), against a metal target and a condensed explosive surface, is considered as, the important process accompanying the normal entry of a rigid projectile into a target, was overlooked in the preceding studies. Within the framework of accurate shock wave theory, and the utilization of both Tait's EOS and the relationship, D=C+sU, the flowfield, behind the bow shock wave attached to the perimeter of the adjoined surface, was defined. The maximum values of the peak pressure are 2.2 to 3.2 times higher for the metallic and soft targets (nitromethane, PBX 9502), than peak pressure values at the stagnation point. This effect changes the commonly held notion that the maximum pressure peak is reached at the projectile stagnation point. In the present study the interaction of a spherical decaying blast wave, caused by an underwater explosion, with a piece-wise plane target having corner configurations, is investigated. The numerical results based on Tait's EOS result in the determination of the vulnerable spots on the target where the maximum overpressure peak surpassed that for the head-on shock wave reflection by a factor of 5. [Preview Abstract] |
Tuesday, August 2, 2005 12:15PM - 12:30PM |
J2.00006: Semiconductor Model of Detonation Konstantin Grebenkin According to the semiconductor model of detonation [1-2], the rate of the burning wave propagation from the hot spots and, hence the energy release macrokinetics in a detonating HE, is controlled by the electron heat conductivity process in unreacted HE compressed and heated by the shock. In the given report a review on current status of the semiconductor model of detonation is presented, including the results of the recent measurements of electric conductivity of unreacted TATB-based HE loaded by shock waves [3], evaluation of the rate of the burning wave propagation from the hot spots and, finally, an improved temperature-based macrokinetic model of detonation initiation in TATB-based explosives. \newline \textbf{References} \begin{enumerate} \item Grebenkin K.F. Technical Physics Letters. 1998. V.24. p. 789 (Translated from Russian). \item Grebenkin K.F., Zherebtsov A.L., Kutepov A.L., Popova V.V. Technical Physics. 2002. v.~47, N. 11, p.~1458 (Translated from Russian). \item Gorshkov M.M., Grebenkin K.F., Zaikin V.T., et al. Technical Physics Letters. 2004. v.~30, n. 8, pp. 631 (Translated from Russian). \end{enumerate} [Preview Abstract] |
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