Dislocation Mechanics of High-Rate Deformations

Armstrong, Ronald W.; Li, Qizhen

doi:10.1007/s11661-015-2779-6

Cited by 51 publications

(21 citation statements)

References 93 publications

(150 reference statements)

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“…Follansbee et al, 1984) and with the experimental data obtained by Klopp et al (1985) for FCC aluminium. It is also noted that, as conventional knowledge holds for FCC metals (see Armstrong and Li, 2015), our model predicts a very small strain rate sensitivity of the source activation strength for strain rates below 10 4 s À 1 .…”

Section: Numerical Computation Of the Strain Rate Dependence Of The Fsupporting

confidence: 64%

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The mechanisms governing the activation of dislocation sources in aluminum at different strain rates

Gurrutxaga-Lerma

Balint

Dini

et al. 2015

Journal of the Mechanics and Physics of Solids

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a b s t r a c tThis article examines the time to activate Frank-Read sources in response to macroscopic strain rates ranging from 10 1 s À 1 to 10 10 s À 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 FrankRead sources at strain rates up to 10 6 s À 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 10 6 s À 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 10 8 s À 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 Â 10 7 s À 1 homogeneous nucleation becomes the dominant generation mechanism.

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Section: Numerical Computation Of the Strain Rate Dependence Of The Fsupporting

confidence: 64%

“…Furthermore, the formation of twins is known to play a dominant role in the high strain response of HCP materials (see Price, 1963;Huang and Gray, 1989;Armstrong and Li, 2015).…”

Section: Alternative Mechanisms For Generation Of Dislocationsmentioning

confidence: 99%

The mechanisms governing the activation of dislocation sources in aluminum at different strain rates

Gurrutxaga-Lerma

Balint

Dini

et al. 2015

Journal of the Mechanics and Physics of Solids

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“…Agreement has been shown also [50] with Z-A prediction for an upturn of SHPB results reported for tantalum crystal and polycrystal materials [51]. Latest measurements reported for aluminium at very high pressures [52] have been described as well on the same Z-A-type model basis [53].…”

Section: Discussionsupporting

confidence: 69%

Bertram Hopkinson's pioneering work and the dislocation mechanics of high rate deformations and mechanically induced detonations

Armstrong

2014

Phil. Trans. R. Soc. A.

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Bertram Hopkinson was prescient in writing of the importance of better measuring, albeit better understanding, the nature of high rate deformation of materials in general and, in particular, of the importance of heat in initiating detonation of explosives. This report deals with these subjects in terms of post-Hopkinson crystal dislocation mechanics applied to high rate deformations, including impact tests, Hopkinson pressure bar results, Zerilli–Armstrong-type constitutive relations, shock-induced deformations, isentropic compression experiments, mechanical initiation of explosive crystals and shear banding in metals.

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“…Accordingly, the interpretation of the obtained results should be carefully handled. The applied strain rate can influence both hardening mechanisms and dislocation network properties (see, e.g., [140][141][142][143][144]). In other words, one should note that the observed mechanisms are not an artifact of the high strain rates used in the atomistic simulation.…”

Section: Atomistic Simulation Of Nanoindentationmentioning

confidence: 99%

Review of Nanoindentation Size Effect: Experiments and Atomistic Simulation

2017

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Nanoindentation is a well-stablished experiment to study the mechanical properties of materials at the small length scales of micro and nano. Unlike the conventional indentation experiments, the nanoindentation response of the material depends on the corresponding length scales, such as indentation depth, which is commonly termed the size effect. In the current work, first, the conventional experimental observations and theoretical models of the size effect during nanoindentation are reviewed in the case of crystalline metals, which are the focus of the current work. Next, the recent advancements in the visualization of the dislocation structure during the nanoindentation experiment is discussed, and the observed underlying mechanisms of the size effect are addressed. Finally, the recent computer simulations using molecular dynamics are reviewed as a powerful tool to investigate the nanoindentation experiment and its governing mechanisms of the size effect.

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Dislocation Mechanics of High-Rate Deformations

Cited by 51 publications

References 93 publications

The mechanisms governing the activation of dislocation sources in aluminum at different strain rates

The mechanisms governing the activation of dislocation sources in aluminum at different strain rates

Bertram Hopkinson's pioneering work and the dislocation mechanics of high rate deformations and mechanically induced detonations

Review of Nanoindentation Size Effect: Experiments and Atomistic Simulation

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