Shock Propagation In Crustal Rock. (9999)
Ahrens, Thomas J., Duffy, Thomas S., Rubin, Allan M., Sekine, Toshimori
New equation of state data for a weathered granite shocked to about 125 GPa are reported and combined with the Westerly granite data of McQueen et al. 1967. From measurements of partially released...
Measurements of the Longitudinal Modulus of Pierre Clay Shale at Varying Strain Rates (9999)
Bless,Stephan J., Ahrens,Thomas J.
The propagation speed of finite-amplitude compressional waves of strain-rate .001-.0001 per sec in Pierre clay shale have been measured using shock wave techniques. The inferred longitudinal modulus...
Tschauner, Oliver, Asimow, Paul D., Kostandova, Natalya, Ahrens, Thomas J., Ma, Chi, Sinogeikin, Stanislas, ...
We observed micrometer-sized grains of wadsleyite, a high-pressure phase of (Mg,Fe)_2SiO_4, in the recovery products of a shock experiment. We infer these grains crystallized from shock-generated...
Shock compression of preheated molybdenum to 300 GPa (2009)
Asimow, Paul D., Sun, Daoyuan, Ahrens, Thomas J.
Shock compression experiments on samples at elevated initial temperature provide a test of the Mie-Grüneisen method of predicting off-principal Hugoniot states. Pure molybdenum, preheated to 1673 K,...
Mosenfelder, Jed L., Asimow, Paul D., Frost, Daniel J., Rubie, David C., Ahrens, Thomas J.
We present new equation-of-state (EoS) data acquired by shock loading to pressures up to 245 GPa on both low-density samples (MgSiO_3 glass) and high-density, polycrystalline aggregates (MgSiO_3...
The crystal structure of calcite III (2007)
Joseph R. Smyth, Thomas J. Ahrens
. The crystal structure of calcite III has been deduced from existing high pressure powder X-ray diffraction patterns, based on the assumption that it is a displacive modification of the calcite I...
Shock Propagation in Crustal Rock (2006)
Anderson, William W., Ahrens, Thomas J.
The shock Hugoniot and adiabatic release curves of sedimentary rocks display a range of different behaviors that affect the decay of shock waves propagating away from a confined source. Many of the...
Decreased values of cosmic dust number density estimates in the solar system (2005)
Willis, Michael, Burchell, Mark J., Ahrens, Thomas J., Krüger, Harald, Grün, Eberhard
Deflection and Fragmentation of Near-Earth Asteroids (2004)
Ahrens, Thomas J., Harris, Alan W.
Collisions by near-earth asteroids or the nuclei of comets pose varying levels of threat to man. A relatively small object, approximately 100 m diameter, which might be found on an impact trajectory...
Melting at the Limit of Superheating (2004)
Luo, Sheng-Nian, Ahrens, Thomas J., Swift, Damian C.
Theories on superheating-melting mostly involve vibrational and mechanical instabilities, catastrophes of entropy, volume and rigidity, and nucleation-based kinetic models. The maximum achievable...
Impact-Induced Melting of Near-Surface Water Ice on Mars (2004)
Stewart, Sarah T., Ahrens, Thomas J., O'Keefe, John D.
All fresh and many older Martian craters with diameters greater than a few km are surrounded by ejecta blankets which appear fluidized, with morphologies believed to form by entrainment of liquid...
Giant Impact Induced Atmospheric Blow-Off (2004)
Ahrens, Thomas J., Shen, Andy H., Ni, Sidao
Previous calculations indicate that the Earth suffered impacts from objects up to Mars size. Such a giant impact may have produced a temporary ejecta-based ring that accreted to form the Moon. To...
Luo, Sheng-Nian, Ahrens, Thomas J., Çağin, Tahir, Strachan, Alejandro, Swift, Damian C.
The maximum superheating and undercooling achievable at various heating (or cooling) rates were investigated based on classical nucleation theory and undercooling experiments, molecular dynamics (MD)...
Shock wave induced vaporization of porous solids (2003)
Shen, Andy H., Ahrens, Thomas J., O'Keefe, John D.
Strong shock waves generated by hypervelocity impact can induce vaporization in solid materials. To pursue knowledge of the chemical species in the shock-induced vapors, one needs to design...
Superheating systematics of crystalline solids (2003)
Luo, Sheng-Nian, Ahrens, Thomas J.
Systematics of superheating (theta= T/Tm–1) of crystalline solids as a function of heating rate (Q) are established as beta= A(Q)(theta+ 1)theta2, where the normalized energy barrier for...
Superheating systematics of crystalline solids (2003)
Luo, Sheng-Nian, Ahrens, Thomas J.
Systematics of superheating (theta= T/Tm–1) of crystalline solids as a function of heating rate (Q) are established as beta= A(Q)(theta+ 1)theta2, where the normalized energy barrier for...
Depth of Cracking beneath Impact Craters: New Constraint for Impact Velocity (2002)
Ahrens, Thomas J., Xia, Kaiwen, Coker, Demirkan
Both small-scale impact craters in the laboratory and less than 5 km in diameter bowl-shaped craters on the Earth are strength (of rock) controlled. In the strength regime, crater volumes are nearly...
Austin, Daniel E., Ahrens, Thomas J., Beauchamp, J. L.
We report on the design and testing of a compact impact-ionization time-of-flight mass spectrometer for analysis of cosmic dust, suitable for use on deep space missions. The instrument, Dustbuster,...
Shock Effects in Carbonate Minerals and Rocks. (2002)
Vizgirda,Joana, Ahrens,Thomas J.
The ESR spectra of Mn(++) in naturally and laboratory shocked calcite crystals and coral core samples were studied and variations in several spectral parameters were found to be correlative with...
Shock Effects in Carbonates. (2002)
Vizgirda,Joana, Ahrens,Thomas J.
Permanent deformation of very small crystallites of carbonate minerals, such as those occurring in the Eniwetok core, has been examined using the following techniques: (a) Peak broadening of X-ray...
Shock wave propagation in porous ice (2000)
Stewart, Sarah T., Ahrens, Thomas J.
We present data on shock wave propagation in porous ice under conditions applicable to the outer solar system. The equation of state of porous ice under low temperature and low pressure conditions...
Vitreous GeO2 response to shock loading (2000)
Liu, C., Ahrens, Thomas J., Brar, N. S.
Shock wave profiles in vitreous GeO2 (6.56 Mg/m^3) under planar loading were measured using stress gauges to 14 GPa. New and previous data yield Hugoniot: D=0.974 (km/s)+1.711 u for shocks of 6 to 40...
Shock temperatures in calcite (CaCO3): Implication for shock induced decomposition (2000)
Gupta, Satish C., Love, Stanley G., Ahrens, Thomas J.
The temperatures induced in crystalline calcite upon planar shock compression (95–160 GPa) are reported from two-stage light gas-gun experiments. The temperatures are obtained fitting 6-channel...
Shock induced vaporization of anhydrite CaSO4 and calcite CaCO3 (2000)
Gupta, Satish C., Ahrens, Thomas J., Yang, Wenbo
Discovery of abundant anhydrite (CaSO4) and gypsum (CaSO4.2H2O) in the otherwise carbonate sediments comprising the upper portion of the rocks contained within the Chicxulub impact crater has...
EVALUATION OF EQUATION OF STATE DATA. (1998)
Ahrens,Thomas J., Anderson,Don L.
Equations of state for earth materials are necessary for the calculation of intense stress-wave propagation and seismic coupling resulting from explosions or impacts on or within the earth's crust....
Holographic Study of Wave Propagation in Granite. (1998)
Aprahamian,Robert, Jacoby,Jerold J., O'Keefe,John D., Ahrens,Thomas J.
Three techniques of holographic interferometry were developed to study the repsonse of geological materials to propagating stress waves. Two of these techniques, stored-beam interferometry and...
Dynamic Consolidation of Super Hard Materials. (1998)
Yang, Wenbo, Bond, G. M., Tan, Hua, Ahrens, Thomas J., Liu, G.
Shock consolidation experiments were conducted via flyer impact on synthetic diamond (6-12 microns) and cubic boron nitride (c-BN) (4-8 microns) admixed with SiC whisker, Si3N4 whisker, SiC powder...
Shock Propagation In Crustal Rock. (1998)
Ahrens, Thomas J., Duffy, Thomas S., Rubin, Allan M., Sekine, Toshimori
New equation of state data for a weathered granite shocked to about 125 GPa are reported and combined with the Westerly granite data of McQueen et al. The shock velocity (U sub s)-particle velocity...
Dynamic Response of Ceramics. (1998)
Ahrens, Thomas J., Chen, Guangging, Tyburczy, James A.
Both solid to gas (CaSO4 + SiO yields SiO3 + S02 and Si3N4 + 3C (diamond) and 3SiC + 2 N2) can be shock-induced at ballistic velocities. Because of the endothermic nature of the gas-producing...
Shock Propagation in Crustal Rocks: Sandstone, Limestone and Shale. (1998)
Ahrens, Thomas J., Anderson, William W., Zhao, Yusheng
We present shock compression and release data for Coconino Sandstone, Solenhofen and Bedford limestones, and Chambless shale. Urnestone, sandstones, and shale display three separate phases on the...
Equation of State of Clay, Shale and Slate. (1998)
Anderson, William W., Zhao, Yusheng, Ahrens, Thomas J.
New shock compression and release adiabat data to approx. 150 GPa are reported for kaolinite clay and rocks derived from clay- and mica-rich materials. The kaolinite data yield an STP isentropic bulk...
Shear Wave Generation from Contained Explosions (1998)
Ahrens, Thomas J., Liu, Cangli
The usefulness of the amplitude ratio of seismic phases such as Lg/P, as well as the ratio of magnitudes to discriminate explosions from earthquakes depends, in part, on the efficiency of shear wave...
Shock-Induced Damage in Rock and Concrete (1998)
Liu, Charles C., Ahrens, Thomas J.
We have developed a technique for measuring the depth time history of rigid body penetration into brittle materials under a deceleration of ^10(exp 5) g. A series of 4140 steel projectile...
Wave Generation from Explosions in Cavities in Rock (1998)
Liu, Cangli, Ahrens, Thomas J.
We have developed a measurement mehtod to monitor P- and S-waves generated from laboratory-scale explosions in meter-sized rock media at a series of stations, and invented a unique device to drill...
Dynamic Consolidation of Cubic Boron Nitride and Its Admixtures. (1998)
Cubic boron nitride (c-BN) powders admixed with graphite-structured boron nitride powder (g-BN), silicon carbide whisker (SCW), or silicon nitride whisker (SNW) were shock compacted to pressures up...
Shock Propagation in Crustal Rock. (1998)
Anderson, Willliam W., Ahrens, Thomas J.
We present shock compression and release data for Coconino Sandstone and Solenhofen and Bedford limestones. Both limestone and sandstone display three separate phases on the Hugoniot curve. For...
Dynamic compression of an Fe–Cr–Ni alloy to 80 GPa (1997)
Duffy, Thomas S., Ahrens, Thomas J.
Wave profiles were measured in an Fe–Cr–Ni alloy (stainless steel 304) shock compressed to Hugoniot stresses between 7 and 80 GPa. A single-stage propellant gun was used to generate shock states...
Loss of High Frequency Upon Propagation through Shock-Damaged Rock, (1996)
Ahrens, Thomas J., Liu, Cangli
The attenuation of stress waves in samples of gabbroic rock subjected to shock loading up to 11 GPa is studied. We determine the attenuation coefficients, alpha sub p, for samples with different...
Evans, Noreen J, Ahrens, Thomas J, Gregoire, DC
New data on Ru/Ir abundance ratios are presented for nonmarine (Hell Creek, Montana; Frenchman River, Saskatchewan) and marine Cretaceous-Tertiary boundary sites (Brazos River, Texas; Beloc, Haiti;...
Inward electrostatic precipitation of interplanetary particles (1994)
Rulison, Aaron J., Flagan, Richard C., Ahrens, Thomas J.
An inward precipitator collects particles initially dispersed in a gas throughout either a cylindrical or spherical chamber onto a small central planchet. The instrument is effective for particle...
Shock-wave viscosity measurement (1991)
Miller, Gregory H., Ahrens, Thomas J.
The problem of measuring the viscosity of fluids under shock-loading conditions is discussed. The authors examine in detail the method of Sakharov et al. (1965) and Zaidel' (1967) for measuring shear...
Shock induced polymorphic transition in quartz, carbon, and boron nitride (1990)
A theory describing the polymorphism induced by shock waves in silicates, oxides, sulfides, and many inorganic solids is presented. Shock wave experiments conducted on these and other materials...
Shock consolidation of diamond and graphite mixtures to fused polycrystalline diamond (1988)
Potter, David K., Ahrens, Thomas J.
The production of fused compacts of polycrystalline diamond was achieved by subjecting porous (35%–49% porosity) mixtures of diamond crystals plus graphite (13–16 wt. %) to dynamic shock...
Shock-induced melting and shear banding in single-crystal NaCl (1988)
Schmitt, Douglas R., Ahrens, Thomas J., Svendsen, Bob
Radiative color temperatures were measured in single-crystal sodium chloride under shock compression parallel to [100] over a pressure range from 20 to 35 GPa. Color temperatures from 2500 to 4500 K...
Dynamic consolidation of diamond powder into polycrystalline diamond (1987)
Potter, David K., Ahrens, Thomas J.
The formation of a polycrystalline solid compact, by fusing an initially porous aggregate of diamond crystals under dynamic shock pressure (7.5–18 GPa), is shown to depend critically on the size of...
Shock-induced radiation spectra of fused quartz (1983)
Kondo, Ken-ichi, Ahrens, Thomas J., Sawaoka, Akira
An optical multichannel analyzer is applied to observe shock-induced radiation spectra of fused quartz in the 23–31 GPa shock-pressure range. Characteristics of sample-driver interface strongly...
The temperature of shock-compressed water (1982)
Lyzenga, G. A., Ahrens, Thomas J., Nellis, W. J., Mitchell, A. C.
Temperatures from 3300–5200 K were measured in liquid H2O shocked to 50–80 GPa (500–800 kbar). A six-channel, time-resolved optical pyrometer was used to perform the measurements. Good...
Multiwavelength optical pyrometer for shock compression experiments (1979)
Lyzenga, G. A., Ahrens, Thomas J.
A system for measurement of the spectral radiance of materials shocked to high pressures (~100 GPa) by impact using a light gas gun is described. Thermal radiation from the sample is sampled at six...
Lyzenga, Gregory A., Ahrens, Thomas J.
The release of solids from a state of shock compression at a free surface is examined. For isentropic release, the postshock specific volume V[prime]0 is shown to be constrained by V[prime]0?...
Igor Fedorovitch Stravinsky, 1882-1971: a practical guide to publications of his music (1974)
De Lerma, Dominique-René, Ahrens, Thomas J.
1st ed.
Igor Fedorovitch Stravinsky, 1882-1971: a practical guide to publications of his music (1974)
De Lerma, Dominique-René, Ahrens, Thomas J.
1st ed.
Shock wave measurements on solid hydrogen and argon (1973)
Lagus, Peter L., Ahrens, Thomas J.
Hugoniot data for solid argon (initially at 77°K and 1 bar) and solid hydrogen (initially at 5°K and 1 bar) have been obtained to 143 kbar and 6.4 kbar, respectively, using the projectile impact...
Explosive Gas Blast: The Expansion of Detonation Products in Vacuum (1971)
Ahrens, Thomas J., Allen, Charles F., Kovach, Robert L.
A series of 0.2- to 3-gm HNS charges were detonated in vacuums of 10^−3 to 10^−5 Torr. The resultant freely expanding, detonation product, gas blast achieves terminal velocities of 8 to 12 km/sec...
Heat of Formation of O2– (1969)
Gaffney, Edward S., Ahrens, Thomas J.
A series of Born–Mayer-type calculations are used to calculate the lattice energies of simple oxides (MgO, BeO, CaO, and ZnO). Repulsion and other non-Coulombic contributions to the lattice energy...
Calibration of an Image-Converter Streak Camera (1969)
Ahrens, Thomas J., Spetzler, Hartmut
A new technique for time calibrating an image-converter streak camera by repetitively photographing a standard signal displayed on a wide-band sweep-delay oscilloscope is described.
Material Strength Effect in the Shock Compression of Alumina (1968)
Ahrens, Thomas J., Gust, W. H., Royce, E. B.
The Hugoniot elastic limits (HEL) of a high-density aluminum oxide ceramic (Lucalox) and a slightly lower-density ceramic (porosity approximately 4%) were determined to be 112±13 and 83±5 kbar,...
A decrease in resistivity of MgO from >10^(5) to ~10^(3)Ω·cm is observed when thin single crystals are shocked in the [001] direction to 920±70 kbar. This effect may be produced by several...