Instabilities of high speed dislocations

Research output: Contribution to journalLetter

Authors

Colleges, School and Institutes

External organisations

  • Imperial College London

Abstract

Despite numerous theoretical models and simulation results, a clear physical picture of dislocations traveling at velocities comparable to the speed of sound in the medium remains elusive. Using two complementary atomistic methods to model uniformly moving screw dislocations, lattice dynamics and molecular dynamics, the existence of mechanical instabilities in the system is shown. These instabilities are found at material-dependent velocities far below the speed of sound. We show that these are the onset of an atomistic kinematic generation mechanism, which ultimately results in an avalanche of further dislocations. This homogeneous nucleation mechanism, observed but never fully explained before, is relevant in moderate and high strain rate phenomena including adiabatic shear banding, dynamic fracture, and shock loading. In principle, these mechanical instabilities do not prevent supersonic motion of dislocations.

Details

Original languageEnglish
Article number145502
Number of pages6
JournalPhysical Review Letters
Volume121
Issue number14
Publication statusPublished - 2 Oct 2018

ASJC Scopus subject areas