Start-up shear of concentrated colloidal hard spheres: Stresses, dynamics, and structure

Koumakis, Nick; Laurati, Marco; Jacob, Alan R.; Mutch, Kevin J.; Abdellali, A.; Schofield, Andrew B.; Egelhaaf, Stefan U.; Brady, John F.; Petekidis, George

doi:10.1122/1.4949340

Cited by 62 publications

(99 citation statements)

References 85 publications

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“…The function ϕ(γ c ) goes to saturation faster at the higher value of the parameter D. The parameter ϕ 0 is the limit value of ϕ. Namely, at the large deformations (in our case at γ c > 0.6) the long axis of the elliptic contour in the distribution g c (x, y) is oriented at the angle ϕ 0 ≈ 45 • with respect to the gradient direction (see also Refs. [11,20,32]). As it follows from Refs.…”

Section: B Critically-sized Crystalline Nuclei Under Shearmentioning

confidence: 99%

“…This is confirmed by results of large number of studies (Refs. [1,7,14,[23][24][25][26][27][28][29][30][31][32]). So, for example, Kumaraswamy and co-workers [22] have revealed experimentally that non-spherical ordered structures oriented along the shear direction occur for the case of polydisperse isotactic polypropylene melt under intensive shear.…”

Section: Introductionmentioning

confidence: 99%

“…External boundaries of the distribution gc(x, y) are shown by the dashed circle and ellipses. Bottom: projections of the pair distribution function onto shear-gradient xy-plane obtained for hard-sphere glassy systems at different shear strains: (e) 1%, (f) 10%, (g) 20% and (h) 60% (taken from Refs [21,32]…”

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confidence: 99%

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Morphology of critically sized crystalline nuclei at shear-induced crystal nucleation in amorphous solid

Galimzyanov

Мокшин

2018

Journal of Rheology

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In this work we study morphological characteristics of the critically-sized crystalline nuclei at initial stage of the shear-induced crystallization of a model single-component amorphous (glassy) system. These characteristics are estimated quantitatively through statistical treatment of the nonequilibrium molecular dynamics simulation results for the system under steady shear at various (fixed) values of the shear rateγ and at different temperatures. It is found that the sheared glassy system is crystallized through nucleation mechanism. From analysis of a time-dependent trajectories of the largest crystalline nuclei, the critical size nc and the nucleation time τc were defined. It is shown that the critically-sized nuclei in the system are oriented within the shear-gradient xy-plane at moderate and high shear rates; and a tilt angle of the oriented nuclei depends on the shear rate. At extremely high shear rates and at shear deformation of the system more than 60%, the tilt angle of the nuclei tends to take the value 45 • respective to the shear direction. We found that this feature depends weakly on the temperature. Asphericity of the nucleus shape increases with increasing shear rate, that is verified by increasing value of the asphericity parameter and by the contour of the pair distribution function calculated for the particles of the critically-sized nuclei. The critical size increases with increasing shear rate according to the power-law, nc ∝ (γτc) 1/3 , whereas the shape of the critically-sized nucleus changes from spherical to the elongated ellipsoidal. We found that the nc-dependencies of the nuclei deformation parameter evaluated for the system at different temperatures and shear rates are collapsed into unified master-curve. arXiv:1711.04989v1 [cond-mat.mtrl-sci]

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Section: B Critically-sized Crystalline Nuclei Under Shearmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Morphology of critically sized crystalline nuclei at shear-induced crystal nucleation in amorphous solid

Galimzyanov

Мокшин

2018

Journal of Rheology

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“…Reinhardt et al 17 studied the distortion of the pair correlation function under start-up shear. Koumakis et al 18 reported on stresses in the start-up phase of shearing, in particular on the dependence of the stress overshoot on the Peclet number and on the volume fraction, using both simulation and experiments with sterically stabilized PMMA spheres using confocal microscopy and rheological measurements. Stress overshoot in start-up and cessation of shear and the connection to the microscopic fluid structure have also been studied 19 .…”

Section: Introductionmentioning

confidence: 99%

Memory-induced motion reversal in Brownian liquids

Treffenstädt

Schmidt

2020

Soft Matter

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We study the Brownian dynamics of hard spheres under spatially inhomogeneous shear, using event-driven Brownian dynamics simulations and power functional theory. We examine density and current profiles both for steady states and for the transient dynamics after switching on and switching off an external square wave shear force field. We find that a dense hard sphere fluid (volume fraction ≈ 0.35) undergoes global motion reversal after switching off the shear force field. We use power functional theory with a spatially nonlocal memory kernel to describe the superadiabatic force contributions and obtain good quantitative agreement of the theoretical results with simulation data. The theory provides an explanation for the motion reversal: Internal superadiabatic nonequilibrium forces that oppose the externally driven current arise due to memory after switching off. The effect is genuinely viscoelastic: in steady state, viscous forces oppose the current, but they elastically generate an opposing current after switch-off.

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“…During this overshoot period, the material performs a transition from solid-like to fluid-like behavior. It has been the focus of recent work to study the process of yielding in more detail [1][2][3][4][5][6][7][8]. There, we find many different definitions of yield points, each characterizing a different aspect of yielding.The simplest approach of defining a yield strain in glasses is taking the strain at the overshoot maximum γ peak .…”

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confidence: 99%

Shearing small glass-forming systems: A potential energy landscape perspective

Blank-Burian

Heuer

2018

Phys. Rev. E

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Understanding the yielding of glass-forming systems upon shearing is notoriously difficult since it is a strong non-equilibrium effect. Here we show that the concept of the potential energy landscape (PEL), developed for the quiescent state, can be extended to shearing. When introducing an appropriate coarse graining of the extended PEL for sheared systems, one can distinguish two fundamentally different types of plastic events, namely inherent structures (IS) vs. minimized structure (MS) transitions. We apply these concepts to non-cyclic and cyclic shearing of small systems, which allow us to characterize the properties of elementary plastic events. Whereas the general properties of the stress-strain curves are similar to larger systems, a closer analysis reveals significantly different properties. This allows one to identify the impact of the elastic coupling in larger systems. The concept of MS enables us to relate the stress overshoot of a single trajectory to the emergence of an MS transition. Furthermore, the occurrence of limit cycles can be characterized in great detail for the small systems and connections to the properties of the PEL can be formulated. Possible implications of our small-system results for the macroscopic limit are discussed.PACS numbers: I. INTRODUCTIONA common feature of amorphous glass forming materials like metallic glasses, colloidal particles or foams is an overshoot in the stress-strain curve when applying a constant shear rate when starting at rest. During this overshoot period, the material performs a transition from solid-like to fluid-like behavior. It has been the focus of recent work to study the process of yielding in more detail [1][2][3][4][5][6][7][8]. There, we find many different definitions of yield points, each characterizing a different aspect of yielding.The simplest approach of defining a yield strain in glasses is taking the strain at the overshoot maximum γ peak . For the data of 3D Lennard-Jones-type systems, shown in [1], one obtains a value around 0.09, largely independent of system size. Another approach [5] uses an overlap function to determine whether there has been a larger rearrangement between two configurations. The yield is then defined as the point where half of the systems had such a transition. The same results are obtained by using susceptibilities [9]. When using oscillatory shear also the equality of the storage modulus G and the loss modulus G can be used to characterize the transition from elastic to non-elastic behavior [10], although yielding a slightly larger value. This rheological crossover strain can also be related to a sharp transition in the anisotropy of the structure factor [8].Interestingly, via oscillatory shear experiments and simulations in the low-temperature limit a critical strain γ nl can be defined, marking the onset of non-linear behavior [1,[10][11][12][13]. Whereas for strain amplitudes γ max < γ nl one observes limit cycles of the trajectory [1,6,10,11], for γ max > γ nl the system irreversibly leaves its initial region...

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Start-up shear of concentrated colloidal hard spheres: Stresses, dynamics, and structure

Cited by 62 publications

References 85 publications

Morphology of critically sized crystalline nuclei at shear-induced crystal nucleation in amorphous solid

Morphology of critically sized crystalline nuclei at shear-induced crystal nucleation in amorphous solid

Memory-induced motion reversal in Brownian liquids

Shearing small glass-forming systems: A potential energy landscape perspective

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