The mechanisms governing the activation of dislocation sources in aluminum at different strain rates
File(s)
Published version
OA Location
Author(s)
Gurrutxaga Lerma, BENAT
Balint, DS
Dini, D
Sutton, AP
Type
Journal Article
Abstract
This article examines the time to activate Frank–Read sources in response to macroscopic strain rates ranging from 101 s−1 to 1010 s−1 in aluminium under athermal conditions. We develop analytical models of the bowing of a pinned dislocation segment as well as numerical simulations of three dimensional dislocation dynamics. We find that the strain rate has a direct influence on both the activation time and the source strength of Frank–Read sources at strain rates up to 106 s−1, and the source strength increases in almost direct proportion to the strain rate. This contributes to the increase in the yield stress of materials at these strain rates. Above 106 s−1, the speed of the bowing segments reaches values that exceed the domain of validity of the linear viscous drag law, and the drag law is modified to account for inertial effects on the motion of the dislocation. As a result the activation times of Frank–Read sources reach a finite limit at strain rates greater than 108 s−1, suggesting that Frank–Read sources are unable to operate before homogeneous nucleation relaxes elastic stresses at the higher strain rates of shock loading. Elastodynamic calculations are carried out to compare the contributions of Frank–Read sources and homogeneous nucleation of dislocations to plastic relaxation. We find that at strain rates of 5×107 s−1 homogeneous nucleation becomes the dominant generation mechanism.
Date Issued
2015-08-12
Date Acceptance
2015-08-10
Citation
Journal of the Mechanics and Physics of Solids, 2015, 84, pp.273-292
ISSN
1873-4782
Publisher
Elsevier
Start Page
273
End Page
292
Journal / Book Title
Journal of the Mechanics and Physics of Solids
Volume
84
Copyright Statement
© 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC
BY license (http://creativecommons.org/licenses/by/4.0/).
BY license (http://creativecommons.org/licenses/by/4.0/).
License URL
Sponsor
Engineering & Physical Science Research Council (EPSRC)
Grant Number
N/A
Subjects
Science & Technology
Technology
Physical Sciences
Materials Science, Multidisciplinary
Mechanics
Physics, Condensed Matter
Materials Science
Physics
Frank-Read sources
Homogeneous nucleation
Source activation time
Dislocation dynamics
Yield point
SHOCK-INDUCED PLASTICITY
ATOMISTIC SIMULATIONS
EDGE DISLOCATION
SINGLE-CRYSTAL
DEFORMATION
METALS
NUCLEATION
PRESSURE
DYNAMICS
MOTION
Mechanical Engineering & Transports
01 Mathematical Sciences
02 Physical Sciences
09 Engineering
Publication Status
Published