Interscale momentum exchange in dynamically deformed heterogeneous medium

The dynamics of dislocation wall generation in metals and alloys under shock loading

“…We suggest a computer model, clearly demonstrating the fragmentation process through the formation and evolution of the walls and arrays of edge dislocations under the action of an external stress impulse and the stress fields of various configurations of pre-existing wedge grain-boundary disclinations generated during the pre-existing subgrain formation. Our modeling shows that (i) the shock duration used in experiments [14,15] is enough to complete the fragmentation process within the initial subgrain, and (ii) the necessary stress impulse magnitude well agrees with that which was used in these experiments.…”

“…Identical processes in shock-conditioned copper and tantalum were first observed by Andrade et al [12] and by Nesterenko et al [13], respectively. Recently Meshcheryakov et al [14,15] reported that under certain conditions of shock compression, the dynamic recrystallization was also observed in the shear bands in the D16 aluminum alloy.…”

“…In contrast, the "negative" dislocations cannot reach the line connecting the disclinations, and group in some walls and arrays which form new domain boundaries in the area x > 0. It is interesting that the most stable dislocation structure is formed there under the applied shear stress s ¼ 0:5 GPa which corresponds to the conditions of experiments [14,15]. When the initial model disclination structure is a quadrupole (Fig.…”

“…During the shock wave propagation (it was 650 ns in experiments [14,15]), these dislocation walls are expected to catch newly generated edge dislocations that can lead to the rapid transformation of the low-angle boundaries to the high-angle ones, thus completing the fragmentation process.…”

“…It is also worth noting that until now, the 2D D 4 -approach has been applied to simulations in quasi-static conditions under which the fragmentation process develops during hundreds of seconds [28][29][30][31][32]. In the shock-loading experiments of interest [14,15], the duration of the impact impulse was of about 650 ns and, therefore, http://dx. …”