Choosing an adequate mathematical model in problems with high pulsed energy deposition

The problems of choosing the optimal mathematical model for a prescribed range of parameters of a pulsed action are discussed. A preliminary analysis performed by similarity and dimensional-analysis methods using interpolation equations of state of the matter shows that the complete system of equations of gasdynamics can be simplified by dropping individual terms which are not important in a given parameter range. The results of an analysis are presented in the form of nomograms, which also make it possible to identify the class of fast and energy-intensive gasdynamic processes more accurately than at an intuitive level. Zh. Tekh. Fiz. 68, 44–47 (May 1998)     

Dynamic compressibility,release adiabats,and the equation of state of stilbene at high energy densities

The shock adiabat of porous stilbene (1,2-diphenylethylene) up to the pressure P = 41 GPa and the dynamic compressibility of this material in reflected shock waves up to 77 GPa are studied experimentally. The run of the expansion isentropes of stilbene down to 0.1 GPa is determined. The experimental findings are used to construct a semi-empiric equation of state of stilbene for a wide range of high-energy states.     

Melting of Titanium by a Shock Wave Generated by an Intense Femtosecond Laser Pulse

JETP Letters - Laser shock peening with ultrashort laser pulses has been studied by hydrodynamic and atomistic simulations, as well as experimentally. It has been shown that, in contrast to...     

Acceleration of Metallic Flyers at Angara-5-1 Facility

The acceleration of a flyer by a magnetic field allows studying the dynamic characteristics of matter in submicrosecond processes. At the Angara-5-1 facility, pressure is created by a magnetic field of the current with the linear current density of up to 5 MA/cm. The velocity of up to 10 km/s was obtained in the first experiments on acceleration of a duralumin flyer 1 mm thick. Two methods are used for registration of the flyer velocity: laser shadow photography and VISAR interferometric method. This paper presents the results of experiments on determining the velocity of a flyer by the VISAR method. Particular attention is paid to the problem of suppression of spurious signals in the VISAR registration system. The first problem was electromagnetic interference emerging when the Angara-5-1 facility is activated, when megavolt voltages and megaampere currents are generated within a hundred nanoseconds. The second problem was bremstrahlung radiation emerging when magnetic self-isolation is established in vacuum transmission lines. This radiation affects the optics, fiber optic cables, and photomultipliers. The suppression of these two sources of interference ensured the reliable registration of the VISAR signals. The results obtained by the two laser methods—shadow photography and VISAR—coincide with each other and with the results of numerical simulation of flyer acceleration. The experimental results and simulation results are compared.

     

Shock compression of some porous media in conical targets: numerical study

Axially symmetric flows in conical solid targets filled by porous aluminum, graphite or polytetrafluoroethylene under impact of an aluminum plate with the velocity of 2.5 km/s are simulated numerically within the framework of the model of the hypoelastic ideal-plastic solid. The porosity of the samples is taken into account by conservation laws at the leading shock wave; the medium behind that is supposed to be nonporous. Equations of state for all materials in question are used to describe thermodynamic properties of the impactor and target over a wide range of pressures and temperatures taking into account phase transformations. The maximal over space and time pressure as a function of the initial relative density is presented and discussed.     

Erratum to: Several Articles in JETP Letters

JETP Letters - An Erratum to this paper has been published: https://doi.org/10.1134/S0021364022350016     

Thermodynamic functions of the heated electron subsystem in the field of cold nuclei

The paper presents electronic heat capacities and thermal pressures calculated for aluminum and tungsten at densities ρ₀ ≤ ρ ≤ 2ρ₀ in the case when the temperature of electrons is finite (a few electron-volts) and nuclei are cold. Calculations were done with the all-electron full-potential linear muffin-tin orbital method (FP-LMTO) and compared with data obtained with the Liberman's average-atom model and the Vienna Ab-initio Simulation Package code (VASP) which uses pseudopotentials. It is shown that results obtained with different approaches qualitatively agree within the ranges of electron temperatures and densities under consideration, and quantitatively agree within 10% in most cases.     

Equation of State of Al Based on the Thomas–Fermi Model

A wide‐range semiempirical equation of state for aluminum applicable both at near‐normal conditions and in dense plasma is presented. The finite‐temperature Thomas–Fermi model is used for the thermal contribution of electrons thus diminishing the number of fitting parameters and giving information about a mean ion charge. The constructed equation of state agrees with majority of available shock‐wave data (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)