Shock Experiments

The diagnostics applied to shock experiments can be characterized as either prompt or delayed. Prompt instrumentation measures shock velocity, particle velocity, stress history, or temperature during the initial few shock transits of the specimen, and leads to the basic equation of state information on the specimen material. Delayed instrumentation includes optical photography and flash X-rays of shock-compression events, as well as post-mortem examinations of shock-produced craters and soft-recovered debris material. 

G.T. Gray III, Shock Experiments in Metals and Ceramics, in EXPLOMET 90 (edited by M.A. Meyers, L.E. Murr, and K.P. Staudhammer), Marcel Dekker, New York, 1991, in press. 

The unloading wave itself provides a direct measure of the strength at pressure from the shape of the release wave. Such a measurement requires time-resolved detection of the wave profile, which has not been the usual practice for most strong shock experiments. 

Perhaps the most widely misunderstood aspect of gauge development is the role of the controlled shock-compression experiment in the development process. It is often stated that the gauges are being calibrated. In fact, it is not possible to calibrate a gauge that must be used over the wide range of conditions and over the wide range of wave profiles encountered and is destroyed in use. Only in special cases of shocks to fixed conditions is the response measured for a gauge in controlled experiments directly a suitable calibration. Even in the direct shock experiment, the controlled shock-compression experiment serves as a shock calibration only if the reproducibility of materials in the sensor is evaluated quantitatively and a persistent reproducible materials source is available. 

The most distinctive aspect of the shock work is the determination of higher-order piezoelectric constants. The values determined for the constants are, by far, the most accurate available for quartz and lithium niobate, again due to the direct nature of the measurements. Unfortunately it has not been possible to determine the full set of constants. Given the expense and destructive nature of the shock experiment, it is unlikely that a full set of higher-order piezoelectric constants can be determined. A less expensive investigation of higher-order constants could be conducted with the ramp wave or acceleration wave loading experiment described in the chapter. 

Other physiological functions of MAAs in phototrophic organisms such as organic osmolytes have been suggested, because very high concentrations can be found in cyanobacteria living in hypersaline environments (Oren 1997). However, salt shock experiments with the marine cyanobacterium Microcoleus chthono-plastes did not indicate ary major involvement of MAAs in the process of osmotic acclimation (Karsten 2002), and hence their proposed function as osmolytes has to be questioned. 

Figure 13. Left panel Schematic representation of a shock compression in the PV diagram. Right panel Building up of a Hugoniot by the Rayleigh lines (Rp obtained from different shock experiments.

Fredriksson, K., De Carli, P. (1964) Shock emplaced argon in a stony meteorite 1. Shock experiment and petrology of sample. J. Geophys. Res., 69, 1403-6. 

Schmitt R. T. (2000) Shock experiments with the H6 chondrite Kernouve pressure calibration of microscopic shock effects. Meteorit. Planet. Sci. 35, 545—560. 

This study confirms our previous result [8] that even ultrashort shock experiments with laser and electric discharge guns are well suited to reproduce shock defects known to occur in naturally shocked minerals. For example, dislocation glide and twinning activated in the experimentally shocked specimens have also been detected in weakly shocked limestones from the Ries crater [50]. 

F. Langenhorst and A. Deutsch, Shock experiments on pre-heated a- and p-quartz 1. Optical and density data. Earth Planet. Sci. Lett. 125, pp. 407-420 (1994). 

F. Langenhorst, M. Boustie, A. Migault, and J.P. Romain, Laser shock experiments with nanoseconds pulses a new tool for the reproduction of shock defects in olivine. Eardi Planet. Sci. Lett. 173, pp. 333-342 (1999). 

Six shock experiments were perfonned with shock pressures of 16.9, 19.6. 24.0. 30.7, 34.5, and 40.8 GPa. Measured densities, p, are shown in Fig. 3.14a. X-ray diffraction data were measured witli Mo-Ka radiation. Raman spectra in the range 115-1200 and 400-1400 cm i were measured for each sample [27,70],... 

We would like to express our gratitude to Drs. M. Oliaslii at Kanagawa University, M. Kato at the Institute of Space and Astronomical Science, and N. Handa at Aichi Prefectural University for constructive discussions on shock experiments and on mechanisms of shock reactions. We tliank Dr. W. Agena at uses in Denver for critically reading the manuscript. We also indebted to T. Masuda, K. Suzuki, and T. Torii at Nagoya University for tlieir teclinical assistance. This woik is partially supported by the Grant in Aid for Scientific Research, No. 07740436, No. 08740426, and No. 12640447 from the Ministry of Education, Japan, and Joint Project Fund from Japan National Oil Corporation. 

Regarding the pressure duration, the electrical discharge technique forms a bridge between laser ( nanoseconds) and high-explosive (—microseconds) shock experiments. Our electrical discharge device produces shock waves that last between —10 and 100 ns (Fig. 1.1). The shorter lime limit is valid for the highest pressure and reflects the need to use thinner projectiles to achieve the higher flyer-plate velocities. 

Using the techniques described above, we have performed systematic shock experiments on single-crystal calcite as well as on chemically pure calcite powder in the pressure range from 12.5 to 100 GPa. The shock front propagated parallel to the (1014) plane of single-crystal calcite. The calcite powder was compacted to pellets with a porosity on the order of 5 %, leading to higher shock and postshock temperatures than with the otherwise identical experimental setup. 

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