Damage growth and recollection in aluminum under axisymmetric convergence using a helical flux compression generator

Abstract

Damage initiation and evolution, failure, and recollection processes under axisymmetric convergence were studied in the Russian-Damage experimental series, a joint effort between the Los Alamos National Laboratory and the All-Russian Institute of Experimental Physics. A helical explosive magnetic generator was used to drive a cylindrical liner shell to produce shock wave loading of a concentric cylindrical target shell. Shock wave amplitude was controlled by the liner-to-target spacing and by the magnetic field amplitude. Variation of the current pulse duration produced either a single impact, to study damage initiation through failure, or a double impact, to study failure with recollection. Both full and partial recollection of the main crack was obtained. By fielding high-precision diagnostics to measure the dynamic drive conditions and material response and by employing post-shot metallographic analysis, this project produced well-characterized experimental data across a range of damage and recollection levels for the chosen material, aluminum. We present selected experimental results to illustrate the methodology and utility of this experimental technique.

Fundamentals of Electrodynamic Technique of Numerical Designing of Helical High-Explosive Magnetic Generators

“…HEMGs with diameters of 160, 200, and 400 mm have been developed, producing the output electromagnetic energy of 0.5-20 MJ. Such HEMGs combined with explosion current switch are used in liner experiments R-DAMAGE [18], [19] and for heating thermonuclear plasmas in experiments with the MAGO/MTF chamber [20]- [25] Here MAGO/MTF is for the MAGnitnoe Obzhatie (Russian for "MAGnetic Compression")/Magnetized Target Fusion. Such HEMGs are used for the initial feeding of the disc EMGs, which are the highest power EMGs among the EMGs.…”

Numerical analysis of damage kinetics in aluminium under axisymmetric loading

“…The EPPS comprised of a helical explosive magnetic generator (HEMG), an explosive current opening switch (OS), an explosive current interrupter (CI) and a coaxial transmission line (TL) supplied the current from the explosive magnetic device to the liner unit is described in [3]. The set-up of the R-Damage tests is presented in [1][2][3][4] in detail.…”

“…Both the targets and the liner were made of the Alcan-manufactured high-purity aluminium Al-1060-O. Metallographic analysis of the pre-shot state of the material revealed a significant inhomogeneity of the aluminium microstructure [2]. There were normally distributed quasi-spherical grains in the plane perpendicular to the axis of the billet, and strongly elongated grains in the plane parallel to the axis of the billet.…”

“…the volume of defects, V s -is the volume of the solid component) is the cumulative volume of the microdefects. To determine the parameters of this model (see Table 1), we used the results of the preceding R-Damage experiments [2] due to the lack of data for the aluminum under study. The conception of critical damage ω cr was used to describe the stage of the defects' coalescence and full fracture (pressure and shear strength becomes zero in the cell) with ω cr = 0.07.…”

“…As an example of such validation of a model, the peculiarities of the damage medium behavior under weak compression were analyzed in this work with the help of numerical simulation. Data of two tests "R-Damage-8&9" [1] representing the completion stage of the experimental series "R-Damage-0-9" [2] realized jointly by the VNIIEF and LANL teams were used. The damage evolution and damaged matter recollection under axis-symmetric convergence were studied in the extruded aluminum Al 1060 while these experiments.…”