Micromechanics of emergent patterns in plastic flows

Biswas, Santidan; Grant, Martin; Samajdar, I.; Haldar, Arunansu; Sain, Anirban

doi:10.1038/srep02728

Cited by 15 publications

(17 citation statements)

References 20 publications

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“…1 corresponds to the local crystal orientation, θ , and the bottom panel represents the nearest neighbour characteristics, N coord , of each particle. A careful study shows that arrays of dislocations are mainly arranged along the grain boundaries with high misorientations, which is consistent with Frank condition, n ∝ sin dθ , where n is the line density along the grain boundary with the corresponding misorientaion dθ 2122.…”

Section: Resultssupporting

confidence: 71%

Irreversibility transition of colloidal polycrystals under cyclic deformation

Jana

Alava

Zapperi

2017

Sci Rep

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Cyclically loaded disordered particle systems, such as granular packings and amorphous media, display a non-equilibrium phase transition towards irreversibility. Here, we investigate numerically the cyclic deformation of a colloidal polycrystal with impurities and reveal a transition to irreversible behavior driven by the displacement of dislocations. At the phase transition we observe enhanced particle diffusion, system size effects and broadly distributed strain bursts. In addition to provide an analogy between the deformation of amorphous and polycrystalline materials, our results allow to reinterpret Zener pinning of grain boundaries as a way to prevent the onset of irreversible crystal ordering.

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Section: Resultssupporting

confidence: 71%

Irreversibility transition of colloidal polycrystals under cyclic deformation

Jana

Alava

Zapperi

2017

Sci Rep

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“…One of the key question concerns the relationship between the rhe-ological behavior and the microscopic rearrangements that are ultimately responsible for the macroscopic mechanical behavior. While in crystalline solids it has been firmly established that yielding is mediated by defects, 4,5 identifying the microscopic elementary events leading to flow in amorphous materials is more challenging, due to the their disordered structure.…”

Section: Introductionmentioning

confidence: 99%

A microscopic view of the yielding transition in concentrated emulsions

2014

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We use a custom shear cell coupled to an optical microscope to investigate at the particle level the yielding transition in concentrated emulsions subjected to an oscillatory shear deformation. By performing experiments lasting thousands of cycles on samples at several volume fractions and for a variety of applied strain amplitudes, we obtain a comprehensive, microscopic picture of the yielding transition. We find that irreversible particle motion sharply increases beyond a volume-fraction dependent critical strain, which is found to be in close agreement with the strain beyond which the stress-strain relation probed in rheology experiments significantly departs from linearity. The shear-induced dynamics are very heterogenous: quiescent particles coexist with two distinct populations of mobile and 'supermobile' particles. Dynamic activity exhibits spatial and temporal correlations, with rearrangements events organized in bursts of motion affecting localized regions of the sample. Analogies with other sheared soft materials and with recent work on the transition to irreversibility in sheared complex fluids are briefly discussed.

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“…Recent works focus on the irreversible (or plastic) rearrangements at the microscopic level [1][2][3][4][5][6][7], resulting from an applied deformation or stress, which are ultimately responsible for the macroscopic mechanical behavior. Research on amorphous solids is also relevant to crystalline materials [8]. On the one hand, simulations and experiments have revealed that particles in the grain boundaries (GBs) separating crystalline grains exhibit glassy dynamics [9,10].…”

Section: Introductionmentioning

confidence: 99%

Plasticity of a Colloidal Polycrystal under Cyclic Shear

2014

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We use confocal microscopy and time-resolved light scattering to investigate plasticity in a colloidal polycrystal, following the evolution of the network of grain boundaries as the sample is submitted to thousands of shear deformation cycles. The grain boundary motion is found to be ballistic, with a velocity distribution function exhibiting non-trivial power law tails. The shearinduced dynamics initially slow down, similarly to the aging of the spontaneous dynamics in glassy materials, but eventually reach a steady state. Surprisingly, the cross-over time between the initial aging regime and the steady state decreases with increasing probed length scale, hinting at a hierarchical organization of the grain boundary dynamics. The mechanical properties of amorphous solids are a topic of intense research. Recent works focus on the irreversible (or plastic) rearrangements at the microscopic level [1][2][3][4][5][6][7], resulting from an applied deformation or stress, which are ultimately responsible for the macroscopic mechanical behavior. Research on amorphous solids is also relevant to crystalline materials [8]. On the one hand, simulations and experiments have revealed that particles in the grain boundaries (GBs) separating crystalline grains exhibit glassy dynamics [9,10]. On the other hand, polycrystals may be regarded as an amorphous assembly of crystalline grains separated by GBs. In fact, driven polycrystals display mechanical features similar to those of amorphous solids [11] and GB process has been shown to be at the origin of the plasticity of polycrystals in the limit of small grain sizes [11][12][13][14][15].A large number of numerical works have explored the microscopic dynamics induced in amorphous systems by a continuous shear, finding quite generally diffusive dynamics at the particle level [1][2][3], once the affine component of the displacement is removed, as also confirmed by experiments on sheared colloidal glasses [2,7,16]. By contrast, the effect of a cyclic shear has been less investigated, in spite of its relevance to the fatigue tests commonly adopted in material science. Furthermore, cyclic deformation tests allow one to unambiguously identify irreversible rearrangements (as opposed to the non-affine displacement measured in continuous shear, which may be reversible) and to follow the evolution, or aging, of the dynamics as the sample is kept under an oscillatory deformation.Similarly to the case of continuous shear, the microscopic dynamics in cyclically deformed amorphous solids have been found to be diffusive (or even subdiffusive), in simulations [18,19] as well as in experiments on colloids [2,20] or granular matter [21,22]. Aging effects have been reported for macroscopic quantities, e.g. pressure or compacity [23,24], or for the microscopic dynamics. In the latter case, however, aging has been probed over a few tens of cycles at most [22,25].In this Letter, we report on experiments probing the irreversible rearrangements induced in a colloidal polycrystal by thousands of sh...

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Micromechanics of emergent patterns in plastic flows

Cited by 15 publications

References 20 publications

Irreversibility transition of colloidal polycrystals under cyclic deformation

Irreversibility transition of colloidal polycrystals under cyclic deformation

A microscopic view of the yielding transition in concentrated emulsions

Plasticity of a Colloidal Polycrystal under Cyclic Shear

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