From Mild to Wild Fluctuations in Crystal Plasticity

Weiss, Jérôme; Rhouma, W. Ben; Richeton, Thiebaud; Dechanel, S; Louchet, F.; Truskinovsky, Lev

doi:10.1103/physrevlett.114.105504

Cited by 103 publications

(166 citation statements)

References 60 publications

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“…For all strain rates and both orientations (TD and RD), the exponent β of the fitting power-law function, P(I) ~ I -β , varies during the macroscopically uniform plastic flow within the interval from 1.5 to 1.8, similar to the typical (a) (b) value of 1.5 reported for hcp materials [17,20]. It considerably increases close to the onset of necking (more specifically, β ≈ 2.3 ± 0.1 for the TD sample and 2.6 ± 0.1 for the RD sample in Figure 4) and decreases again when the neck is developed.…”

Section: Statistics Of Deformation Processes On a Mesoscopic Scalesupporting

confidence: 67%

Complexity and Anisotropy of Plastic Flow of α-Ti Probed by Acoustic Emission and Local Extensometry

Lebyodkin

Amouzou

Lebedkina

et al. 2018

Preprint

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Current progress in the prediction of mechanical behavior of solids requires understanding of spatiotemporal complexity of plastic flow caused by self-organization of crystal defects. It may be particularly important in hexagonal materials because of their strong anisotropy and combination of different mechanisms of plasticity, such as dislocation glide and twinning. These materials often display complex behavior even on the macroscopic scale of deformation curves, e.g., a peculiar three-stage elastoplastic transition, the origin of which is a matter of debates. The present work is devoted to a multiscale study of plastic flow in α-Ti, based on simultaneous recording of deformation curves, 1D local strain field, and acoustic emission (AE). It is found that the average AE activity also reveals three-stage behavior, but in a qualitatively different way depending on the crystallographic orientation of the sample axis. On the finer scale, the statistical analysis of AE events and local strain rates testifies to an avalanche-like character of dislocation processes, reflected in power-law probability distribution functions. The results are discussed from the viewpoint of collective dislocation dynamics and are confronted to predictions of a recent micromechanical model of Ti strain hardening.

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Section: Statistics Of Deformation Processes On a Mesoscopic Scalesupporting

confidence: 67%

Complexity and Anisotropy of Plastic Flow of α-Ti Probed by Acoustic Emission and Local Extensometry

Lebyodkin

Amouzou

Lebedkina

et al. 2018

Preprint

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“…Above this value, the stress drop distribution exhibits a power law tail, P ( X > Δ τ ) ~ Δ τ − α , with α = 0.8 for test 24, whereas the stress rises do not. This heavy tail, characterizing “wild” fluctuations associated with infinite variance [ Weiss et al ., ], superposes with “mild” fluctuations that dominate the distribution below the threshold. The highly negative skewness and positive kurtosis values observed in these cases are almost entirely explained by these wild fluctuations.…”

Section: Results: Mechanics Of the Competition Between Faulting And Cmentioning

confidence: 99%

Cohesion versus friction in controlling the long‐term strength of a self‐healing experimental fault

et al. 2016

Self Cite

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The Coulomb's failure criterion, which postulates that failure occurs along a fault plane when the applied shear stress overcomes a resistance made of two parts of different nature, cohesion, and friction, remains the standard conceptual framework of faulting mechanics. More recently, rate‐and‐state friction laws became the main modeling tool of the seismic cycle. These laws implicitly assume that only frictional resistance sets the fault strength and its evolution. We therefore raise the question of the role of cohesion and related healing/sealing mechanisms on fault mechanics. We designed an original laboratory experiment based on a model material, an ice thin layer sitting on top of a water tank and mechanically deformed at various rates with a circular Couette‐like geometry. This allowed sliding along the fault plane over arbitrarily large slip distances, and analyzing the competition between faulting and cohesion‐healing rates, whereas frictional resistance, resulting from the fault roughness, is limited in magnitude. We show that cohesion‐healing plays an essential role in the time evolution of the interface strength under constant loading rate. In particular, the magnitudes of shear stress fluctuations are observed to be temperature and velocity weakening. The present experiment shares several properties similar to that of active faults during seismic cycles, suggesting that cohesive healing could control some of these features: scale invariance properties, Gutenberg‐Richter law of rupture event size distribution, Omori's law of energy dissipation, at least after major ruptures, time asymmetry in energy dissipation, and periods of creep under high shear stress alternating with major earthquake‐like ruptures.

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“…For example, dislocation climb and glide are understood in averagedislocation models as acting in kinetic series, whereas the shape of the lambda law high-temperature curve is indicative of two (or more) physical processes acting independently (i.e., in kinetic parallel). Equally difficult is using averagedislocation models to understand steady state dislocation flow as being a self-organized, critical phenomenon [e.g., Bak, 1996], i.e., plasticity following the Gutenberg-Richter law [Gutenberg and Richter, 1949] in which dislocation activity consists of bursts of activity following a burstsize (energy)-frequency power law, behavior that has been characterized for a variety of crystalline solids [e.g., Thomson and Levine, 1998;Miguel et al, 2001;Richeton et al, 2006;Weiss et al, 2015]. Stone [1991] developed a model for dislocation plasticity that encompasses the lambda law observations and yet, in its embrace of stress sensitivity and (Arrhenius) temperature sensitivity, remains consistent with average-dislocation perspectives.…”

Section: Introductionmentioning

confidence: 99%

Load relaxation of olivine single crystals

2016

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Single crystals of ferromagnesian olivine (San Carlos, AZ, peridot; ~Fo88‐90) have been deformed in both uniaxial creep and load relaxation under conditions of ambient pressure, T = 1500°C and pnormalO2 = 10−10 atm; creep stresses were in the range 40 ≤ σ1 (MPa) ≤ 220. The crystals were oriented such that the applied stress was parallel to [011]c, which promotes single slip on the slowest slip system in olivine, (010)[001]. The creep rates at steady state match well the results of earlier investigators, as does the stress sensitivity (a power law exponent of n = 3.6). Dislocation microstructures, including spatial distribution of low‐angle (subgrain) boundaries, additionally confirm previous investigations. Inverted primary creep (an accelerating strain rate with an increase in stress) was observed. Load relaxation, however, produced a singular response—a single hardness curve—regardless of the magnitude of creep stress or total accumulated strain preceding relaxation. The log stress versus log strain rate data from load‐relaxation and creep experiments overlap to within experimental error. The load‐relaxation behavior is distinctly different than that described for other crystalline solids, where the flow stress is affected strongly by work hardening such that a family of distinct hardness curves is generated, which are related by a scaling function. The response of olivine for the conditions studied, we argue, indicates flow that is rate limited by dislocation glide, reflecting specifically a high intrinsic lattice resistance (Peierls stress).

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From Mild to Wild Fluctuations in Crystal Plasticity

Cited by 103 publications

References 60 publications

Complexity and Anisotropy of Plastic Flow of α-Ti Probed by Acoustic Emission and Local Extensometry

Complexity and Anisotropy of Plastic Flow of α-Ti Probed by Acoustic Emission and Local Extensometry

Cohesion versus friction in controlling the long‐term strength of a self‐healing experimental fault

Load relaxation of olivine single crystals

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From Mild to Wild Fluctuations in Crystal Plasticity

Cited by 103 publications

References 60 publications

Complexity and Anisotropy of Plastic Flow of &alpha;-Ti Probed by Acoustic Emission and Local Extensometry

Complexity and Anisotropy of Plastic Flow of &alpha;-Ti Probed by Acoustic Emission and Local Extensometry

Cohesion versus friction in controlling the long‐term strength of a self‐healing experimental fault

Load relaxation of olivine single crystals

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Product

Resources

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Complexity and Anisotropy of Plastic Flow of α-Ti Probed by Acoustic Emission and Local Extensometry

Complexity and Anisotropy of Plastic Flow of α-Ti Probed by Acoustic Emission and Local Extensometry