摘要:

Shock Hugoniot compression curve for water has been measured up to less than 1 GPa. Plane and steady shock wave is produced in water by the flat plate impact of a projectile accelerated up to 500m/s by a compressed gas gun. To measure shock Hugoniot in this pressure range in higher precision, a new experimental procedure was proposed, which is based on the very large pressure dependence of the refractive index of water upon compression. By using this method, shock compression curve was determined. It was confirmed that within the pressure range covered in this experiment, shock-particle velocity Hugoniot can be described by a linear relation with a large slope. Shock temperature was calculated by using the obtained Hugoniot data combined with the values of thermodynamical variables. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303422

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

In case of shock waves in polymers in the stress range of less than 1 GPa, a strategy to measure the slope of shock velocity-particle velocity Hugoniot curve is proposed. The method is based on the measurement of sound velocity at the shocked state as well as shock and particle velocity. The slope of Hugoniot can be evaluated by combining these values with the shock thermodynamic equation. Experiments were conducted for two kinds of polyethylene samples exhibiting peculiar shape of Hugoniot curve. An in-material PVDF gauge detects both a plane shock wave in polyethylene target induced by impact with a flyer plate and a rarefaction wave reflected from free surface of the flyer. Slope of the Hugoniot analyzed at several Hugoniot points for the polyethylene samples are consistent with their peculiar shape of the Hugoniot curves. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303423

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

A series of time-resolved experiments has been done using a 50-mm-diameter light gas gun to characterize the shock uniaxial strain and high-strain-rate response of a high purity iron. The high-strain-rate uniaxial stress response of the iron was characterized using a Split-Hopkinson Pressure Bar. Shock wave experiments were done both with and without windows with a VISAR diagnostic to obtain time-resolved particle velocity data. The shock experiments with windows yield information on elastic/plastic response, transformation kinetics, sound speed, and quasi-elastic release. Experiments were conducted without windows both below and above the &agr;-to-&Vegr; phase transformation to study the effect of phase-change kinetics and the release transition on the spallation response in iron. Results of the shock and Hopkinson bar experiments are compared and contrasted to previous research on iron. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303424

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

A discrepancy still exists between key shock temperature measurements and corresponding results from laser-heated diamond anvil cells for iron. Shock melting temperatures for iron deduced from anvil interface temperature measurements exceed the melting curve from static experiments. Also, current shock sound velocity work is not reproducing earlier shock sound velocity experimental results indicating a solid-solid phase transition at 200 GPa along the Hugoniot. It has been suggested that the disparity in these measurements is due to metastability and superheating of shocked solid phases beyond equilibrium phase boundaries on the short dynamic time scale. Indeed, various shock temperature data sets on alkali halides, quartz and forsterite have exhibited superheating of these ionic and covalent solids beyond the normal melting curves. However, metals such as iron have different interatomic potentials than do atoms, in, say, ionic solids, and one would expect less metastability in shocked states. I examine these claims of metastability in light of available data and molecular dynamics calculations of the region behind the shock front. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303425

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

We have performed a series of sound velocity measurements in iron at earth’s core pressures. Experiments were carried out at shock pressures as high as 400 GPa, with particular emphasis on the pressure range between 175 GPa and 275 GPa. The measured sound velocities of iron at elevated pressures exhibit a single discontinuity near 250 GPa, corresponding to the vanishing of shear strength as the iron melts. A second discontinuity reported by Brown and McQueen in their previous iron sound velocity studies was not observed in our study. Our results are consistent with their data otherwise. Experimental details and error propagation techniques essential to determining the melting point will also be discussed. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303426

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Shock Hugoniots of metal with different initial volume and pressure have been calculated with the use of multi-phase equation of state. An application of D’yakov-Kontorovich’s criterion revealed an existence of specific sound instability in the liquid-gas region. The instability arises as a spontaneous sound emission from the shock discontinuity. The position of the instability region and its dependence on initial pressure and volume has been analyzed. Here general regularities obtained on the base of the analysis for 30 metals are discussed. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303427

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Equations of state for metals based on the soft-sphere model are presented. Parameters of the soft-sphere potential are found. Binodals with critical points, isobars, shock adiabats, and release isentropes are calculated. Comparison of the results with available experimental data is made. Monte-Carlo simulation at constant pressure is carried out with obtained parameters. The results are in a good agreement with semiempirical isobar calculations. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303428

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

To investigate direct and reverse polymorphic transition of tin, shock compression measurements have been carried out up to 50 GPa peak stress. Interface velocity measurements between tin target and LiF window have been recorded using VISAR measurement technique. Interface velocity profiles show direct and reverse polymorphic transition and melting on release. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303429

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

We have developed launch capabilities that can propel macroscopic plates to hypervelocities (8 to 16 km/s). This capability has been used to determine the first time-resolved wave-profile measurements unsing velocity interferometry techniques at impact velocities of 10 km/s. These measurements show that aluminum continues to exhibit normal release behavior to 161 GPa with complete loss of strength in the shocked state. Results of these experiments are discussed and compared with the results of lower-pressure experiments conducted at lower impact velocities. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303430

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

A high-pressure phase transition ofAl2O3from the corundum structure to theRh2O3(II)structure at over 70 GPa has been theoretically predicted, while sufficient experimental evidences have not been reported. In this study, the Hugoniot-measurement experiments were performed on a corundum-structureAl2O3single crystal to obtain the informations about the high-pressure polymorph. The Hugoniot parameters were measured by the inclined-mirror method in the pressure range up to over 100 GPa. A possible kink due to phase transition was observed on the inclined-mirror images in the pressure range higher than 70 GPa. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303431

出版商:AIP    

年代:1900

数据来源: AIP