Structural Rearrangements That Govern Flow in Colloidal Glasses

Schall, Peter; Weitz, David A.; Spaepen, Frans

doi:10.1126/science.1149308

Cited by 544 publications

(539 citation statements)

References 22 publications

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“…To take into account the long range effects of the plastic events, first predicted by Argon 23 and later evidenced in molecular dynamics simulations 24 and experiments on colloids 25 we change the above homogeneous equation to a field description with a stress propagator G(r − r ′ ) accounting for the stress redistribution due to a plastic event,…”

Section: Modelmentioning

confidence: 99%

Spontaneous formation of permanent shear bands in a mesoscopic model of flowing disordered matter

2012

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This study proposes a coherent scenario of the formation of permanent shear bands in the flow of yield stress materials. It is a well accepted point of view that flow in disordered media is occurring via local plastic events, corresponding to small size rearrangements, that yield a long range stress redistribution over the system. Within a minimalistic mesoscopic model that incorporates these local dynamics, we study the spatial organisation of the local plastic events. The most important parameter in this study is the typical restructuring time needed to regain the original structure after a local rearrangement. In agreement with a recent mean field study [Coussot et al., Eur. Phys. J. E, 2010, 33, 183] we observe a spontaneous formation of permanent shear bands, when this restructuring time is large compared to the typical stress release time in a rearrangement. The bands consist of a large number of plastic events within a solid region that remains elastic. This heterogeneous flow behaviour is different in nature from the transient dynamical heterogeneities that one observes in the small shear rate limit in flow without shear-banding [Martens et al., Phys. Rev. Lett., 2011, 106, 156001]. We analyse in detail the dependence of the shear bands on system size, shear rate and restructuring time. Further we rationalise the scenario within a mean field version of the spatial model, that produces a non monotonous flow curve for large restructuring times. This explains the instability of the homogeneous flow below a critical shear rate, that corresponds to the minimum of the curve. Our study therefore strongly supports the idea that the characteristic time scales involved in the local dynamics are at the physical origin of permanent shear bands.

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Section: Modelmentioning

confidence: 99%

Spontaneous formation of permanent shear bands in a mesoscopic model of flowing disordered matter

2012

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“…Amorphous solids, including metallic, polymeric, and colloidal glasses, possess complex mechanical response to applied deformations, such as plastic flow [1][2][3][4], strain localization [5][6][7][8][9], creep flow [7,10,11], and fracture [12][13][14]. In crystalline materials, topological defects reflecting the symmetry of the crystalline phase govern response to deformation.…”

Section: Introductionmentioning

confidence: 99%

Effects of cooling rate on particle rearrangement statistics: Rapidly cooled glasses are more ductile and less reversible

et al. 2017

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Amorphous solids, such as metallic, polymeric, and colloidal glasses, display complex spatiotemporal response to applied deformations. In contrast to crystalline solids, during loading, amorphous solids exhibit a smooth crossover from elastic response to plastic flow. In this study, we investigate the mechanical response of binary Lennard-Jones glasses to athermal, quasistatic pure shear as a function of the cooling rate used to prepare them. We find several key results concerning the connection between strain-induced particle rearrangements and mechanical response. We show that the energy loss per strain dU loss /dγ caused by particle rearrangements for more rapidly cooled glasses is larger than that for slowly cooled glasses. We also find that the cumulative energy loss U loss can be used to predict the ductility of glasses even in the putative linear regime of stress versus strain. U loss increases (and the ratio of shear to bulk moduli decreases) with increasing cooling rate, indicating enhanced ductility. In addition, we characterized the degree of reversibility of particle motion during a single shear cycle. We find that irreversible particle motion occurs even in the linear regime of stress versus strain. However, slowly cooled glasses, which undergo smaller rearrangements, are more reversible during a single shear cycle than rapidly cooled glasses. Thus, we show that more ductile glasses are also less reversible.

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“…Apart from the stress-induced instantaneous flow of yield, recent experiments and numerical simulations also demonstrated that a glass subject to stress, which is much smaller than its normal yield strength, can also undergo an extreme slow flowing, which is hard to be detected within a short period of time due to the slowness [4][5][6][7] . On the other hand, the universal nano-scaled localized b-relaxation in metallic glassy state has been observed before the large-scale a-relaxation, which has been demonstrated to be related to the nano-scaled microscopic hidden flowing phenomenon [8][9][10][11][12] .…”

mentioning

confidence: 99%

“…The characteristic changes and their intrinsic correlations with GLT process are still far from being thoroughly studied. Recent studies on the atomic-scale glassy structure have revealed the existence of liquid-like sites in glassy state 4,18,19 , which are presumed to be responsible for the viscoelastic flow behaviour in glasses [20][21][22] . Meanwhile, the studies on glasses have demonstrated that the b-relaxation is identified to play an essential role in the GLT process 2,8,9,11,23 , and the b-relaxation has comparable activation energy with that of the deformation unit and strongly correlated with mechanical brittle-to-ductile transition in MGs 20,21,[24][25][26] , indicating that the b-relaxation is closely related to the initiation and evolution of the localized liquid-like deformation units or flow units in MGs [27][28][29][30] .…”

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confidence: 99%

Evolution of hidden localized flow during glass-to-liquid transition in metallic glass

et al. 2014

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For glasses, the structural origin of their flow phenomena, such as elastic and plastic deformations especially the microscopic hidden flow before yield and glass-to-liquid transition (GLT), is unclear yet due to the lack of structural information. Here we investigate the evolution of the microscopic localized flow during GLT in a prototypical metallic glass combining with dynamical mechanical relaxations, temperature-dependent tensile experiments and stress relaxation spectra. We show that the unstable and high mobility nano-scale liquid-like regions acting as flow units persist in the glass and can be activated by either temperature or external stress. The activation of such flow units is initially reversible and correlated with b-relaxation. As the proportion of the flow units reaches a critical percolation value, a mechanical brittle-to-ductile transition or macroscopic GLT happens. A comprehensive picture on the hidden flow as well as its correlation with deformation maps and relaxation spectrum is proposed.

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Structural Rearrangements That Govern Flow in Colloidal Glasses

Cited by 544 publications

References 22 publications

Spontaneous formation of permanent shear bands in a mesoscopic model of flowing disordered matter

Spontaneous formation of permanent shear bands in a mesoscopic model of flowing disordered matter

Effects of cooling rate on particle rearrangement statistics: Rapidly cooled glasses are more ductile and less reversible

Evolution of hidden localized flow during glass-to-liquid transition in metallic glass

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