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  • 1
    Electronic Resource
    Electronic Resource
    Anomalous shock initiation of detonation in pentaerythritol tetranitrate crystals (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 601-612 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The anomalous, low-stress, shock initiation of detonation observed in earlier studies of pentaerythritol tetranitrate single crystals was examined in more detail experimentally. Time-resolved particle-velocity histories were obtained for [110], [001] and [100] orientations of single-crystal pentaerythritol tetranitrate explosive for shock input stresses of 4–7 GPa using laser interferometry instrumentation. At about 4.2 GPa an elastic-plastic, two-wave structure was noted in [110] and [001] orientations, and a single shock wave for [100] orientation. The two-wave structure provides an explanation for the anomalous shock initiation sensitivity and intermediate velocity transition previously observed in [110] orientation at this stress level. It also explains details of fluorescent emission histories from [110] and [001] crystals previously measured. The orientation-dependent results are consistent with the model of steric hindrance to shear at the molecular level. Fits to the elastic Hugoniot data in [110] and [001] orientations are given as well as a revised fit for the bulk Hugoniot. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364201
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular mechanics modeling of shear and the crystal orientation dependence of the elastic precursor shock strength in pentaerythritol tetranitrate (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2726-2737 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The elastic precursor shock strengths of pentaerythritol tetranitrate explosive crystals were measured for [100], [101], [110], and [001] orientations using velocity interferometer system for any reflector instrumentation for samples 3–6 mm thick. Input shock strength was 1.14 GPa. Measured precursor amplitudes were 0.38, 0.58, 0.98, and 1.22 GPa, respectively, for the four orientations. Critical shear stress for the slip system with the maximum resolved shear stress for each shock orientation was computed. Details of the elastic and plastic wave profiles are discussed. Molecular mechanics modeling of the shear induced by the uniaxial strain of a plane shock wave in this molecular crystal was also performed using the amber code. This may be the first application of molecular mechanics computation to a shear problem. The modeling correctly predicts the dependence of the precursor amplitude on crystal orientation for the cases considered. The results confirm the importance of steric hindrance to shear in controlling the orientation-dependent strength in molecular crystals and sensitivity to shock initiation of detonation in molecular explosive crystals. Details of the molecular deformations and contributions to the energy barrier to inelastic shear for different orientations are given. The computational results also explain why the {110} 〈11¯1〉 slip system is observed in quasistatic deformation in spite of having the longest Burgers vector. The dynamics of sterically hindered, shock-induced shear is considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357576
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  • 3
    Electronic Resource
    Electronic Resource
    Shock response of pentaerythritol tetranitrate single crystals (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 3572-3587 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The shock response of single crystals of the explosive pentaerythritol tetranitrate was studied from 3.4 to 19 GPa. Four orientations, 〈110〉, 〈001〉, 〈101〉, and 〈100〉 were studied. The shock Hugoniot and shock initiation sensitivities were measured in wedge tests. Intermediate velocity transitions were noted. A sensitivity anomaly near 4 GPa was discovered for 〈110〉 orientations. Chemiluminescent phenomena associated with this anomaly were studied using framing photography and uv/visible spectroscopy. Both plane-wave explosive and gas-gun impact experiments were done. Analysis of the steric hindrance occurring during edge dislocation motion in the shear flow associated with shock-induced uniaxial strain was done. The results corroborate the hypothesis that the orientation dependence of shock initiation sensitivity is due to the anisotropy of plastic flow, that is, the relative ease of slip in different orientations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349253
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  • 4
    Electronic Resource
    Electronic Resource
    The Hugoniot and shock sensitivity of a plastic-bonded TATB explosive PBX 9502 (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 4881-4888 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The plane shock response of PBX 9502 was measured from 0.5 to 25 GPa. The explosive is 95-wt. % triamino-trinitrobenzene powder coated with Kel-F 800 plastic; porosity was 2.6%. Shock initiation sensitivity, the Hugoniot, and dynamic yield behavior were studied. Experiments done were explosively driven wedge tests and particle velocity history measurements using electromagnetic gauges at a light-gas gun. A new analysis of the wedge test was implemented. Based on wedge test results, an approximation for the particle velocity at the shock front is constructed, which is used in functional composition with the Hugoniot to calculate the shock path of each experiment. Optimization on the parameters of the approximation and the Hugoniot simultaneously ensures agreement of the Hugoniot with the overall kinematics of the shock growth as well as the particle velocity/shock velocity data. The individual shock paths are used to examine the single-curve buildup assumption; the assumption is not valid for PBX 9502. A ramping elastic precursor of 0.073 GPa strength was observed. The yield and weak shock behavior are interpreted in terms of porosity, crystalline anisotropy, and residual strain in the pressed, plastic-bonded explosive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340428
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  • 5
    Electronic Resource
    Electronic Resource
    Transient impact response of three polymers (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 2520-2529 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental data are presented for the transient response of three polymers, Estane, Estane with a nitro-plasticizer, and adiprene, subject to flat-plate impact. These data are analyzed in terms of a generalized Maxwell model and the theory of characteristics for the dynamical motion. Comparison of theory and experiment quantifies the high-frequency component in the Maxwell description; for Adiprene the high-frequency shear modulus and relaxation time are 300 MPa and approximately 50 ns, respectively. For estane the corresponding quantities are 300 MPa and approximately 200 ns. Low-pressure Hugoniot data are also presented for estane. An estimate of the low-pressure Hugoniot is given for Adiprene. Some experimental data are also presented for the Estane/nitro-plasticizer combination; this material is used as a binder in plastic-bonded explosives. Theory is presented for a thermodynamically consistent calculation of temperature in high-rate loading of polymers whose mechanical properties are represented by a generalized Maxwell model. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368413
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  • 6
    Electronic Resource
    Electronic Resource
    Supercritical shear in shocked pentaerythritol tetranitrate (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 2494-2495 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Supercritical shear occurs when the shear stress exceeds the strength of the perfect crystal. An estimate of the theoretical strength of the molecular crystal pentaerythritol tetranitrate is compared to experimental observations of the shock response of this explosive. It is concluded that supercritical shear may be occurring at shock stresses of several GPa in underdriven shocks where there is an elastic wave followed by a slower plastic wave. The induced simultaneous slip on sterically crowded cystallographic planes may be the mechanism for shock initiation of detonation in this explosive, at least in the low stress regime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106944
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  • 7
    Electronic Resource
    Electronic Resource
    Orientation-dependent explosion sensitivity of solid nitromethane (1993)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 97 (1993), S. 6193-6196 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100125a017
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  • 8
    Electronic Resource
    Electronic Resource
    Reproducibility of Planewave Transit Times in three explosives during initiation: Comparison to wedge experimentsWork done under the auspices of the U. S. Department of Energy, LA-UR-19-2669. (1980)
    Weinheim : Wiley-Blackwell
    Propellants, Explosives, Pyrotechnics 5 (1980), S. 139-144 
    Details
    ISSN: 0721-3115
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Planewave transit times were measured in three explosives: PBX-9404, pressed TNT, and PBX-9502. Four nominally identical disks were used on each shot to measure the reproducibility of the transit time. Standard deviations in transit times were 1%-2% if most of the wave trajectory was in the initiation phase. The standard deviation in transit times is larger than the measurement precision; this indicates a distribution in the response to the input pressure wave. Comparison was made to results of previous wedge initiation experiments. We conclude that most of the scatter in run distances to detonation found in wedge experiments is not inherent in the initiation process or the explosive quality. The scatter may be due to the imprecision of the free-surface velocity measurement coupled with the power-law character of the relation between run distance to detonation and input pressure.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prep.19800050505
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