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Strength measurements on dry Indiana limestone using Ramp loading techniques

AIP Conference Proceedings

Reinhart, William D.; Vogler, Tracy V.; Chhabildas, L.C.

An accurate method for controlling strain rates in dynamic compressions studies involves using the non-linear elastic property of fused silica to transform an initial shock into a ramp wave of known amplitude and duration. Fused silica when placed between a dry Indiana limestone specimen and a projectile produces strain rates in the range of 104/s. Ramp-loading strain rates are higher than what can be produced on Hopkinson bars and lower than what shock experiments attain. The strength determined at the elastic limit under ramp loading compared to Hopkinson bar measurements shows a significant strength increase with increasing strain rate. © 2007 American Institute of Physics.

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TYPE Conference YEAR 2007
ScopusOSTI

Mesoscale and continuum calculations of wave profiles for shock-loaded granular ceramics

AIP Conference Proceedings

Vogler, Tracy V.; Borg, J.P.

Attenuating wave profiles from shock experiments on tungsten carbide powder are compared to calculations from the continuum P-λ model and a 2-D mesoscale model to gain insight into the suitability of the two models. When calibrated, both models accurately capture the Hugoniot response of the powder and the arrival times of unattenuated steady waves. Their amplitudes are more accurately given by the mesoscale model since its reshock states are above the Hugoniot as seen experimentally; the P-λ model, in contrast, reshocks along the Hugoniot. When the attenuating wave is in the range of the Hugoniot data, the models predict attenuation correctly. However, when attenuation falls below the Hugoniot data both models are somewhat inaccurate, and the material response seems to lie between the two models. The final aspect considered is the wave rise time, which is qualitatively correct for the mesoscale model but completely inaccurate for the P-λ model. © 2007 American Institute of Physics.

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TYPE Conference YEAR 2007
ScopusOSTI

Statistics of the Hugoniot elastic limit from line VISAR

AIP Conference Proceedings

Furnish, Michael D.; Vogler, Tracy V.; Alexander, Charles S.; Reinhart, William D.; Trott, Wayne T.; Chhabildas, Lalit C.

Material heterogeneity appears to give rise to variability in the yield behavior of ceramics and metals under shock loading conditions. The line-imaging VISAR provides a way to measure this variability, which may then be quantified by Weibull statistics or other methods. Weibull methods assign a 2-parameter representation of failure phenomena and variability. We have conducted experiments with tantalum (25 and 40 μm grains) and silicon carbide (SiC-N with 5 μm grains). The tantalum HEL variability did not depend systematically on peak stress, grain size or sample thickness, although the previously observed precursor attenuation was present. SiC-N HEL variability within a single shot was approximately half that of single-point variability in a large family of shots; these results are more consistent with sample-to-sample variation than with variability due to changing shot parameters. © 2007 American Institute of Physics.

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TYPE Conference YEAR 2007
ScopusOSTI

Shock response of dry sand

Reinhart, William D.; Chhabildas, Lalit C.; Vogler, Tracy V.

The dynamic compaction of sand was investigated experimentally and computationally to stresses of 1.8 GPa. Experiments have been performed in the powder's partial compaction regime at impact velocities of approximately 0.25, 0.5, and 0.75 km/s. The experiments utilized multiple velocity interferometry probes on the rear surface of a stepped target for an accurate measurement of shock velocity, and an impedance matching technique was used to deduce the shock Hugoniot state. Wave profiles were further examined for estimates of reshock states. Experimental results were used to fit parameters to the P-Lambda model for porous materials. For simple 1-D simulations, the P-Lambda model seems to capture some of the physics behind the compaction process very well, typically predicting the Hugoniot state to within 3%.

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TYPE SAND Report YEAR 2007
DOIOSTI
Results 101–125 of 151
Results 101–125 of 151