Lattice wave emission from a moving dislocation

Abstract

A dislocation moving in a lattice accelerates and decelerates due to the lattice periodicity and emits lattice waves. Simulations of this process in square and triangular lattices have been presented. Under a small stress, less than 70-80 % of the Peierls stress, a dislocation moving from an unstable position cannot overcome the next Peierls hill because it loses energy by emitting lattice waves. With a larger stress a long-distance motion of a dislocation is possible. When a dislocation moves slowly, lattice waves of dipolar type are emitted in the direction perpendicular to the motion of the dislocation. When the dislocation velocity is about half of the shear wave velocity, a V-shaped pattern of strong lattice vibration forms behind the moving dislocation because of the restricted propagation directions of the excited lattice waves. When the dislocation velocity exceeds 70% of the shear wave velocity, pair creation of dislocations occurs, which leads to dislocation cascading. A dislocation can move faster than the shear wave velocity in the square lattice, and there is no discontinuous change between subsonic and supersonic motions. The dislocation velocity is not proportional to the applied stress. The energy loss of the moving dislocation is about one order of magnitude larger than the theoretical value estimated by phonon-scattering mechanisms, even at room temperature.

Dynamic Discrete Dislocation Plasticity

“…Hirth and Lothe (1991) identified this as an instability of the core of the dislocation. Kinematic generation of dislocations remains a largely unexplored area; however, it has been described in some MD simulations, notably by Weinee and Pear (1975), Schiotz, Jacobsen, and Nielsen (1995), Koizumi, Kirchner, and Suzuki (2002), and Tsuzuki, Branicio, and Rino (2009). In the latter two, the dissociation was not identified as such, but core instabilities were reported nonetheless.…”

“…It is commonly observed, both experimentally (Johnston & Gilman, 1959;Nix & Menezes, 1971) and in MD simulations (Bitzek & Gumbsch, 2004Koizumi et al, 2002;Olmsted et al, 2005;Tsuzuki et al, 2008), that dislocation glide is severely overdamped (Gilman, 1969) and directly proportional to the dislocation's velocity in a manner similar to a viscous drag force in fluid motion (Gilman, 1969;Hirth, 1996;Hirth & Lothe, 1991;Hull & Bacon, 2011). This was in fact first established by Leibfried (1950), who proposed the drag force of the form…”

Dynamics of steps along a martensitic phase boundary I: Semi-analytical solution

“…However, there are some important differences. In particular, the dislocation model assumes a periodic potential, which results in the breakdown of a steady dislocation motion at a sufficiently high subsonic velocity (Flytzanis et al, 1974) and leads to nucleation of new dislocations on the same slip plane (Koizumi et al, 2002). Meanwhile, the three-parabola potential used here to model the phase transition delays the breakdown of steady subsonic motion.…”

A moving screw dislocation interacting with an imperfect piezoelectric bimaterial interface

“…These solutions should be useful for analyzing the interaction between the interface imperfection and the velocity of the moving dislocation, and the corresponding impact on the involved material properties (e.g., [2,4]). Numerical results are presented to verify the obtained solution and to demonstrate the significant influence of the interface imperfection and the velocity of the dislocation on the induced electroelastic fields.…”

“…Its density and velocity are closely related to the plastic deformation of the crystal [2]. A moving dislocation in the defect structure can also introduce dislocation multiplication behind it [3], and its velocity in a crystal can be changed due to the lattice periodicity [4]. Recently moving dislocation problems in piezoelectric solids have attracted much attention.…”