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  • 1
    Electronic Resource
    Electronic Resource
    Spall fracture properties of aluminum and magnesium at high temperatures (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 8310-8317 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of the dynamic tensile strength of aluminum and magnesium have been carried out by investigations of the spall phenomena over a wide range of temperatures, shock-wave intensities, and load durations. Free-surface velocity profiles were recorded with VISAR and used to provide the spall strength measurements. The initial temperature of samples was varied from room temperature to near the melting point. The peak compressive pressure in the shock waves was varied from 5 to 50 GPa for aluminum and from 2 to 10 GPa for magnesium. The load duration was varied by more than one order of magnitude. The free-surface velocity measurements showed a precipitous drop in the spall strength of preheated samples as temperatures approached the melting point. No significant influence of the peak pressure on the spall strength was observed. The strain-rate dependencies of the spall strength could be represented as power functions with a power index of 0.060 for aluminum and 0.072 for magnesium. Unexpectedly large amplitudes for the Hugoniot elastic limit of both aluminum and magnesium were observed at temperatures approaching the melting point. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362542
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  • 2
    Electronic Resource
    Electronic Resource
    Time-resolved shock-wave experiments on granite and numerical simulations using dynamic phase mixing (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5155-5165 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A recently developed model for simulating the dynamic behavior of silicate materials is applied to the loading and unloading properties of granite. Four time-resolved wave profile measurements on granite are presented and used to supplement Hugoniot data to constrain the model. This model is based on a dynamic process-dependent description of phase mixing. In the solid–solid mixed-phase region, the loading states are determined from a simple two-parameter constraint equation which relates the mass fraction of the high pressure phase λ to the Gibbs free-energy difference between the phases ΔG. On release, the reverse phase transition is modeled as a two-stage transition with each stage described by a two-parameter equation with the same form as the loading equation. In all four of the simulations, the loading behavior of the shock-wave experiment is well represented. For three of the experiments the release behavior is accurately simulated up to the point at which the measured interface speed reaches its first minimum. For the remaining experiment the simulation matches only the earliest release behavior and then rapidly deviates from the measured data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359748
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  • 3
    Electronic Resource
    Electronic Resource
    Hydrodynamic compressibility of silicon carbide through shock compression of metal-ceramic mixtures (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 197-202 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Shock-compression experiments were performed on 50% by volume ceramic-metal mixtures of silicon carbide and copper at pressures of 15–30 GPa. The objective of these experiments was to determine the hydrodynamic compressibility (dynamic pressure-volume response) of silicon carbide through shock measurements on the ceramic-metal composite and the application of analytic mixture theory. Compression states inferred for silicon carbide above 20 GPa appear consistent with hydrodynamic behavior and are in agreement with compression curves extrapolated from ultrasonic data. Dynamic strength or viscosity effects apparently complicate shock compression of the ceramic-metal composite at the lower shock pressures. Shock release experiments on the composites provide further high-pressure equation-of-state data for the ceramic-metal mixture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355883
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  • 4
    Electronic Resource
    Electronic Resource
    Plate impact response of ceramics and glasses (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 3862-3869 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Soft-recovery plate impact experiments have been conducted to study the evolution of damage in polycrystalline Al2O3 samples. Examination of the recovered samples by means of scanning electron microscopy and transmission electron microscopy has revealed that microcracking occurs along grain boundaries; the cracks appear to emanate from grain-boundary triple points. Velocity-time profiles measured at the rear surface of the momentum trap indicate that the compressive pulse is not fully elastic even when the maximum amplitude of the pulse is significantly less than the Hugoniot elastic limit. Attempts to explain this seemingly anomalous behavior are summarized. Primary attention is given to the role of the intergranular glassy phase which arises from sintering aids and which is ultimately forced into the interfaces and voids between the ceramic grains. Experiments are reported on the effects of grain size and glass content on the resistance of the sample to damage during the initial compressive pulse. To further understand the role of the glass, plate impact experiments were conducted on glass with chemical composition comparable to that which is present in the ceramic. These experiments were designed to gain further insight into the possibility of "failure waves'' in glasses under compressive loading.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356066
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  • 5
    Electronic Resource
    Electronic Resource
    Geometric statistics and dynamic fragmentation (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 1210-1222 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The present study is focused on the distributions in particle size produced in dynamic fragmentation processes. Previous work on this subject is reviewed. We then examine the one-dimensional fragmentation problem as a random Poisson process and provide comparisons with expanding ring fragmentation data. Next we explore the two-dimensional (area) and, less extensively, the three-dimensional (volume) fragmentation problem. Mott's theory of random area fragmentation is developed, and we propose an alternative application of Poisson statistics which leads to an exponential distribution in fragment size. Both theoretical distributions are compared with analytic and computer studies of random area geometric fragmentation problems, including those suggested by Mott, the Voronoi construction, a variation of the Johnson–Mehl construction, and several methods of our own. We find that size distributions from random geometric fragmentation are construction dependent, and that a conclusive choice between the two distributions cannot be made. A tentative application of the maximum entropy principle to fragmentation is discussed. The statistical theory is extended to include a concept of statistical heterogeneity in the fragmentation process. Finally, comparisons are made with various, dynamic fragmentation data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336139
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  • 6
    Electronic Resource
    Electronic Resource
    Shock viscosity and the prediction of shock wave rise times (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 692-701 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The present study is focused on viscouslike behavior of solids during large-amplitude compressive stress-wave propagation. Maximum strain rate in the plastic wave has been determined for 30 steady- or near steady-wave profiles obtained with velocity interferometry methods. The materials include six metals, aluminum, beryllium, bismuth, copper, iron, and uranium, and two insulating solids, magnesium oxide and fused silica. A plot of Hugoniot stress versus maximum strain rate for each material is adequately described by η(overdot)=aσmh. The exponent m is approximately 4 for all materials while the coefficient a is material dependent. A model is developed which incorporates the observed trends of the shock viscosity data in a three-dimensional framework. Finite-difference calculations using the model reproduce the experimental wave profile data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336184
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  • 7
    Electronic Resource
    Electronic Resource
    Shock and release wave properties of yttria-doped tetragonal and cubic zirconia (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4868-4874 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Velocity interferometry diagnostics are used to monitor transmitted compressive shock and release waves in yttria (Y2O3)-stabilized tetragonal and cubic zirconia. In tetragonal zirconia compressive yielding due to lattice slip or lattice instability is observed at 13–17 GPa and again at 30–31 GPa. This represents an additional fine structure to the dynamic compression of zirconia that has not previously been observed. A correlation with initial sample density is seen for the lower-amplitude yield. A single yield over the range of the data occurs at 5–6 GPa for cubic zirconia. Approximately 4%–6% porosity in the cubic zirconia accounts for initial yield somewhat lower than earlier studies. From unloading wave profile measurements, initial release wave velocities at the Hugoniot state and stress derivatives of these data are determined. Release moduli data increase monotonically over a Hugoniot stress range of 11–45 GPa. A stress derivative of this data of K'l = 1.85 is obtained. Stress derivatives determined directly from the initial release slope of individual profiles are significantly higher and suggest deformation or phase transformation kinetics on release. Release waves from Hugoniot states of 11–13 GPa suggest formation of a rarefaction shock and may imply a dynamic stress-induced transformation not indicated by the shock profile. A tensile spall strength of 1.6 GPa was determined for the tetragonal zirconia. This high value may be related to the large fracture toughness of this transformation-toughened ceramic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350631
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  • 8
    Electronic Resource
    Electronic Resource
    Fragmentation of the universe (1983)
    Springer
    Astrophysics and space science 94 (1983), S. 401-412 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have tested the hypothesis that the universe underwent a single fragmentation event, separating into protogalactic volumes at a relatively early stage after the Big Bang. Assuming that the present total luminosity of each galaxy is proportional to its mass, we plotted the number and mass distribution of a thousand nearby galaxies just as we would in an analysis of fragments from a laboratory high-explosive experiment. The results are consistent with the single-fragmentation hypothesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00653729
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  • 9
    Electronic Resource
    Electronic Resource
    Strain-rate dependent fracture initiation (1980)
    Springer
    International journal of fracture 16 (1980), S. 471-478 
    Details
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Résumé La théorie de la mécanique de la rupture linéaire élastique dynamique dans le cas d'une mise en charge de Heavyside sur une fissure isolée est utilisée pour la formulation d'une réponse à une sollicitation à vitesse de déformation constante sur une fissure unique. L'équation numérique de la solution de Heavyside est démontrée comme susceptible de conduire aux contraintes d'amorçage d'une fissure qui sont dépendantes de la vitesse de déformation imposée. On montre que les contraintes d'amorçage de la rupture sont relativement indépendantes de la dimension de la fissure et de la forme de la fissure. On utilise les résultats pour expliquer la contrainte à la rupture dépendant de la vitesse de déformation, telle qu'elle est observée dans certains matériaux pierreux, et qui se trouvent être davantage une réponse structurelle qu'une propriété de base du matériau.
    Notes: Abstract The theory of linear elastic dynamic fracture mechanics for Heaviside loading of an isolated crack is employed to formulate the response to constant strain-rate loading of a single crack. Numerical integration of the Heaviside solution is shown to lead to fracture initiation stresses that are dependent upon the imposed strain rate. These fracture initiation stresses are also shown to be relatively independent of the crack size and crack shape. The results are used to explain the strain-rate dependent fracture stress observed in some rocks as being a structural response, rather than a basic material property.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00016585
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  • 10
    Electronic Resource
    Electronic Resource
    Fragmentation of metal rings by electromagnetic loading (1983)
    Springer
    Experimental mechanics 23 (1983), S. 393-400 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A method is described for performing fragmentation studies on rapidly expanding metal rings. A fast-discharge capacitor system generates magnetic forces which accelerate the rings to maximum radial velocities of approximately 200 m/s corresponding to circumferential-strain rates of approximately 104/s at fragmentation. Streak-camera techniques are used to record the time-resolved motion of the rings. Fracture-strain and fragmentation experiments have been performed on samples of OFHC copper and 1100-0 aluminum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02330054
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