摘要:

We present a molecular dynamics method based on the Gauss’ principle of least constraint to calculate the shock polar of various liquids. Comparison of numerical results obtained from Gauss mechanics and Newton mechanics (this last case corresponding to the propagation of a real shock wave in the sample) shows that the two methods give the same final thermodynamic state. However, Gauss mechanics is interesting because the equilibrium state is reached very quickly (about10−13&hthinsp;s) and not many particles (a few thousand) are required for the simulation. Then, Gauss mechanics appears to be a very efficient method to evaluate a thermodynamic state obeying particular relation, such as Hugoniot, in a systematic way. Simulations on liquid argon and nitromethane are presented. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303452

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Shock-induced vaporization of matter under expansion from high energy states is of interest as an experimental method to determine two-phase region boundaries and position of critical point of liquid-vapor transition. High speed of expansion of matter on the boundary leads to formation of the so-called “boiling wave.” Intensive heat and mass transfer with hot shocked helium on the boundary give the opportunity to investigate states not only near binodal but also liquid spinodal. Another possibility to achieve near critical point pressures and temperatures is the heating of material by hot driving plasma under launching. This additional heating gives the possibility to achieve temperatures and pressures exceeding critical parameters of tungsten—one of the most refractory metals. New experimental results and issues of such investigation with nickel and tungsten is analyzed in the proposed paper. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303453

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The paper studies isentropic expansion of shock-compressed tungsten, nickel and tin porous samples from 60–150 GPa Hugoniot states to states taking place at release to air. The obtained data is compared to computations with two wide-range model equations of state. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303454

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

An experimental configuration to provide data on the response of foams to shocks generated by an explosive donor was described in an earlier paper. In the original technique Laser interferometery was used to monitor the wave transmitted through the samples. The diagnostics have recently been improved by adding PVDF pressure gauges. It has been shown that pressure gauges give results which are consistent with those obtained using the inherently more accurate velocity gauges. The use of pressure gauges has allowed the transmitted wave to be monitored at more locations in the experiment than was achievable with interferometery alone. Control experiments using non-porous samples, and a series of experiments with foams of equal density but formed from materials having three different solid densities, are described. The results are available for Equation of State development and the “benchmarking” of 1 and 2D hydrocodes. The program was supported by hydrocode calculations using EoS formulations developed at AWE. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303455

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

A prototype equation of state (EOS) browser application has been developed at LLNL. This browser provides an interactive, graphical user interface that allows EOS data to be analyzed, visualized, and compared with experimental data. The user can view our EOS table data in both tabular and graphical form, can obtain lists of table ranges, and can view material information. In addition, the browser allows the user to utilize the interpolation routines of our EOS package to produce the same interpolated EOS data that would be passed to a simulation code, and to analyze this data in many different ways. Interpolated data can be obtained through use of a query function, and lists of interpolated data over various ranges can be produced. Analysis functions include the calculation and display of isotherms, isochores, isobars, adiabats, and shock Hugoniots. Moreover, experimental data can be overlaid onto these plots in order to establish confidence in particular EOS tables. It is expected that this browser environment will be a valuable tool for scientists who use large simulation codes that access equation of state data. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303456

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Equilibrium chemistry has been demonstrated to give reasonable predictions of the equation of state of the reaction products of energetic materials. One advantage of chemistry-based equations of state is the possibility of predicting a reasonably accurate temperature, which is essential for use with detailed models of reactive flow. A framework for reactive flow modelling is presented which allows improved equations of state to be used with more rigorous representations of unreacted and partially-reacted explosive, and with models of phenomena occurring in non-ideal explosives, such as the late release of energy by carbon condensation. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303457

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Optimized extended JCZ3 procedures which have been implemented through the “JAGUAR” computer routines result in accurate detonation properties for wide ranges of conditions including the C-J state and high volume expansions. In order to obtain improved results at highly overdriven conditions, optimized EXP-6 parameters have been established for formic acid by the use of experimental Hugoniot data for PBX-9501. The procedures of this study enable the highly accurate calculation of detonation properties of explosives for a very wide range of volumes. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303458

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

An equation of state (EOSs) for the products of a high explosive (HE) requires calibration in order to determine the appropriate value of material-specific parameters. This calibration is normally done with respect to experimental data, and for HE EOSs, the cylinder test is generally used. A database of experimental cylinder test results has been compiled. In a cylinder test, a metallic cylinder (usually copper) filled with the HE of interest is detonated. The cylinder expansion is observed using a streak camera, and detonation velocity is determined using time-of-arrival pins. Optimization, through matching test conditions and results to an EOS form, either directly or indirectly, gives the EOS parameter set. The current database of tests will be presented, as will progress in using this database to calibrate the parameters of the Jones-Wilkins-Lee EOS form. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303459

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The JCZ and BKW EOS are widely used to compute P-V-T relationships of the gaseous products of CJ detonations, but these computations need experimental verification. Quantitative comparisons of computed and experimental CJ parameters over a wide range of initial density&rgr;0are a good test of the validity of the above EOS. Particularly useful for such comparisons are two empirical linear functions:D=A+B&rgr;0and&rgr;CJ=a+b&rgr;0,and the adiabatic exponent&kgr;1for the CJ state. Reliable measured values of A and B exist for many explosives. Our previous publications obtained a, b, and&kgr;1based on experimental D’s and selected experimentalPCJ.Agreement among EOS computed and experimental values of A or B is unsatisfactory. This means that EOS-basedB&rgr;0/D,a critical factor in obtaining the CJ Gru¨neisen coefficient, Jones &agr;, and partial derivatives of many CJ variables can be in error. Computations ofaorbby variants of JCZ or BKW EOS differ from the empiricalaandb. Consequently, EOS-based&kgr;1’s,PCJ’s,and many CJ parameters that depend on&kgr;1may be in error. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303460

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Experiments have been done to obtain product isentropes of the plastic bonded TATB explosive PBX 9502. A thin aluminum flyer was thrown at an explosive disk so as to generate a state in excess of the Chapman-Jouguet pressure. Because the flyer is thin, the shock wave is followed by a release wave that lowers the pressure in the explosive products. The explosive disk was backed by a LiF tamper/window. Particle velocity at the explosive—window interface was measured with a velocity interferometer (VISAR) and measured particle velocity records were used to construct isentropes. Unexpected behavior is seen in the shape of the isentropes. Experimental details and the resulting isentropes will be presented. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303461

出版商:AIP    

年代:1900

数据来源: AIP