Publisher: Society of Rheology (Total: 1 journals) [Sort alphabetically]

Journal of Rheology
Journal Prestige (SJR): 1.326 Citation Impact (citeScore): 3 Number of Followers: 7 Subscription journal ISSN (Print) 01486055  ISSN (Online) 15208516 Published by Society of Rheology [1 journal] 
 Nondestructive rheological measurements of biomaterials with a magnetic
microwire rheometer
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Authors: Margaret Braunreuther, Maude Liegeois, John V. Fahy, Gerald G. Fuller
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 579588, March 2023.
Programmable hydrogels, such as thiolated hydrogels, are frequently used for tissue engineering and drug delivery applications, because they offer the ability to control gelation, degradation, and adhesion. Understanding how the mechanical properties of these materials change during these processes is essential as they directly impact cell fate and delivery efficacy. The rheology of hydrogels has been quantified primarily via bulk rheological methods. While such methods are effective, they require large sample volumes and result in the destruction of the sample; therefore, responses to multiple stimuli must be recorded across many different samples. We have developed a magnetic microwire rheometer that can characterize the rheology of small sample volumes while maintaining the integrity of the sample, such that the material response to a range of stimuli can be recorded for a single sample. This capability enables insights into timedependent rheological changes, such as gelation and degradation, and can be applied to characterize dynamic in situ systems that are the basis for tissue scaffolding, drug delivery vehicles, and other important biological applications.
Citation: Journal of Rheology
PubDate: 20230224T12:15:08Z
DOI: 10.1122/8.0000606

 Microscopic activated dynamics theory of the shear rheology and stress
overshoot in ultradense glassforming fluids and colloidal suspensions
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Authors: Ashesh Ghosh, Kenneth S. Schweizer
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 559578, March 2023.
We formulate a particle and force level, activated dynamicsbased statistical mechanical theory for the continuous startup nonlinear shear rheology of ultradense glassforming hard sphere fluids and colloidal suspensions in the context of the elastically collective nonlinear Langevin equation approach and a generalized Maxwell model constitutive equation. Activated structural relaxation is described as a coupled localnonlocal event involving caging and longer range collective elasticity which controls the characteristic stress relaxation time. Theoretical predictions for the deformationinduced enhancement of mobility, the onset of relaxation acceleration at remarkably low values of stress, strain, or shear rate, apparent power law thinning of the steadystate structural relaxation time and viscosity, a nonvanishing activation barrier in the shear thinning regime, an apparent Herschel–Buckley form of the shear rate dependence of the steadystate shear stress, exponential growth of different measures of a yield or flow stress with packing fraction, and reduced fragility and dynamic heterogeneity under deformation were previously shown to be in good agreement with experiments. The central new question we address here is the defining feature of the transient response—the stress overshoot. In contrast to the steadystate flow regime, understanding the transient response requires an explicit treatment of the coupled nonequilibrium evolution of structure, elastic modulus, and stress relaxation time. We formulate a new quantitative model for this aspect in a physically motivated and computationally tractable manner. Theoretical predictions for the stress overshoot are shown to be in good agreement with experimental observations in the metastable ultradense regime of hard sphere colloidal suspensions as a function of shear rate and packing fraction, and accounting for deformationassisted activated motion appears to be crucial for both the transient and steadystate responses.
Citation: Journal of Rheology
PubDate: 20230221T04:35:03Z
DOI: 10.1122/8.0000546

 Tribological variablefriction coefficient models for the simulation of
dense suspensions of rough polydisperse particles
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Authors: Jose A. RuizLopez, Sagaya S. Prasanna Kumar, Adolfo VazquezQuesada, Juan de Vicente, Marco Ellero
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 541558, March 2023.
The rheology of concentrated suspensions of particles is complex and typically exhibits a shearthickening behavior in the case of repulsive interactions. Despite the recent interest arisen, the causes of the shearthickening remain unclear. Frictional contacts have been able to explain the discontinuous shear thickening in simulations. However, the interparticle friction coefficient is considered to be constant in most simulations and theoretical works reported to date despite the fact that tribological experiments demonstrate that the friction coefficient can not only be constant (boundary regime) but also decrease (mixed regime) or even increase (fullfilm lubrication regime), depending on the normal force and the relative velocity between the particles and the interstitial liquid between them. Interestingly, the transition between the boundary regime and the fulllubrication regime is governed by the particle average roughness. Particlelevel simulations of suspensions of hard spheres were carried out using shortrange lubrication and roughnessdependent frictional forces describing the full Stribeck curve. Suspensions with different particle’s roughness were simulated to show that the particle roughness is a key factor in the shearthickening behavior; for sufficiently rough particles, the suspension exhibits a remarkable shearthickening, while for sufficiently smooth particles, the discontinuous shearthickening disappears.
Citation: Journal of Rheology
PubDate: 20230216T01:29:45Z
DOI: 10.1122/8.0000514

 Rheology of nonBrownian particle suspensions in viscoelastic solutions.
Part II: Effect of a shear thinning suspending fluid
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Authors: Anni Zhang, Eric S. G. Shaqfeh
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 517540, March 2023.
The shear rheology of particle suspensions in shearthinning polymeric fluids is studied experimentally using parallel plate measurements and numerically using fully resolved, 3D finite volume simulations with the Giesekus fluid model. We show in our experiments that the steady shear viscosity and first normal stress difference coefficient of the suspension evolve from shearthickening to substantially shearthinning as the degree of shearthinning of the suspending fluid increases. Moreover, in highly shearthinning fluids, the suspension exhibits greater shearthinning of the viscosity than the suspending fluid itself. Our dilute bodyfitted simulations show that in the absence of hydrodynamic interactions, shearthinning can arise from the particleinduced fluid stress (PIFS), which ceases to grow with increasing shear rate at low values of [math] (solvent viscosity ratio) and finite values of [math] (the Giesekus drag coefficient). In a Giesekus suspending fluid, the polymers surrounding the suspended particle are unable to stretch sufficiently at high Weissenberg numbers (Wi) and the reduced polymer stress results in a lower PIFS. When coupled with the shearthinning stresslet, this effect creates an overall shearthinning of the viscosity. We then explore the effects of particleparticle interactions on the suspension rheology using immersed boundary simulations. We show that multiparticle simulations are necessary to obtain the shearthinning behavior of the perparticle viscosity of suspensions in shearthinning fluids at moderate values of [math]. Particleparticle interactions lead to a substantial decrease in the PIFS and an enhancement of the shearthinning of the stresslet compared to the single particle simulations. This combination leads to the shearthinning of the perparticle viscosity seen in experiments. We also find that very low values of [math] and finite values of [math] have opposing effects on the perparticle viscosity that can lead to a nonmonotonic perparticle viscosity versus shear rate in a highly shearthinning fluid. Overall, the addition of rigid particles to highly shearthinning fluids, such as joint synovial fluid, leads to increased viscosity and also increased shearthinning at high shear rates.
Citation: Journal of Rheology
PubDate: 20230213T12:32:13Z
DOI: 10.1122/8.0000541

 Rheology of nonBrownian particle suspensions in viscoelastic solutions.
Part 1: Effect of the polymer concentration
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Authors: Anni Zhang, Eric S. G. Shaqfeh
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 499516, March 2023.
We study the effect of varying polymer concentration, measured by the dimensionless polymer viscosity partition function [math], on the steady shear rheology of rigid particle suspensions using direct numerical simulation of the OldroydB model. We compare the bulk rheology using immersed boundary simulations at [math] and [math] to bodyfitted singleparticle simulations and find that the perparticle viscosity and first normal stress difference coefficient are always shearthickening at all values of [math] considered. However, as [math] decreases, the polymer stress transforms the flow field near each particle from closed concentric streamlines to helical streamlines that advect stretched polymers away from the particle surface. At low [math], the polymer stress is diffuse, where the distribution of the particle induced fluid stress (PIFS) caused by the stretched polymers is spread out in the simulation domain rather than concentrated near the particle surface. Therefore in multiparticle simulations, the polymer stress can be significantly affected by particleparticle interactions. The stress generated by a given particle is disrupted by the presence of particles in its vicinity, leading to a significantly lower PIFS than that of the singleparticle simulation. In addition, at increased volume fractions and low values of [math], the polymer stress distribution on the particle surface shifts so as to increase the magnitude of the polymer stress moments, resulting in a shearthickening stresslet contribution to the viscosity that is not seen in single particle or high [math] simulations. This result indicates that for suspensions in highly viscoelastic suspending fluids that are characterized by a low [math] parameter, hydrodynamic interactions are significant even at modest particle concentrations and fully resolved multiparticle simulations are necessary to understand the rheological behavior.
Citation: Journal of Rheology
PubDate: 20230213T12:32:12Z
DOI: 10.1122/8.0000540

 Gaborheometry: Applications of the discrete Gabor transform for time
resolved oscillatory rheometry
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Authors: Joshua David John Rathinaraj, Gareth H. McKinley
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 479497, March 2023.
Oscillatory rheometric techniques such as small amplitude oscillatory shear (SAOS) and, more recently, medium amplitude oscillatory shear and large amplitude oscillatory shear (LAOS) are widely used for rheological characterization of the viscoelastic properties of complex fluids. However, in a timeevolving or mutating material, the buildup or breakdown of microstructure is commonly both time and shearrate (or shearstress) dependent, and thixotropic phenomena are observed in many complex fluids including drilling fluids, biopolymer gels, and many food products. Conventional applications of Fourier transforms for analyzing oscillatory data assume the signals are timetranslation invariant, which constrains the mutation number of the material to be extremely small. This constraint makes it difficult to accurately study shearinduced microstructural changes in thixotropic and gelling materials, and it is becoming increasingly important to develop more advanced signal processing techniques capable of robustly extracting timeresolved frequency information from oscillatory data. In this work, we explore applications of the Gabor transform (a shorttime Fourier transform combined with a Gaussian window), for providing optimal joint timefrequency resolution of a mutating material’s viscoelastic properties. First, we show using simple analytic models and measurements on a bentonite clay that the Gabor transform enables us to accurately measure rapid changes in both the storage and/or loss modulus with time as well as extract a characteristic thixotropic/aging time scale for the material. Second, using the Gabor transform we demonstrate the extraction of useful viscoelastic data from the initial transient response following the inception of oscillatory flow. Finally, we consider extension of the Gabor transform to nonlinear oscillatory deformations using an amplitudemodulated input strain signal, in order to track the evolution of the Fourier–Tschebyshev coefficients of thixotropic fluids at a specified deformation frequency. We refer to the resulting test protocol as Gaborheometry (Gabortransformed oscillatory shear rheometry). This unconventional, but easily implemented, rheometric approach facilitates both SAOS and LAOS studies of timeevolving materials, reducing the number of required experiments and the data postprocessing time significantly.
Citation: Journal of Rheology
PubDate: 20230203T12:59:01Z
DOI: 10.1122/8.0000549

 On the nature of flow curve and categorization of thixotropic yield stress
materials
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Authors: Tulika Bhattacharyya, Alan R. Jacob, George Petekidis, Yogesh M. Joshi
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 461477, March 2023.
Thixotropy is a phenomenon related to time dependent change in viscosity in the presence or absence of flow. The yield stress, on the other hand, represents the minimum value of stress above which steady flow can be sustained. In addition, the yield stress of a material may also change as a function of time. Both these characteristic features in a material strongly influence the steady state flow curve of the same. This study aims to understand the interrelation between thixotropy, yield stress, and their relation with the flow curve. In this regard, we study five thixotropic materials that show yield stress. The relaxation time of all the five systems shows powerlaw dependence on aging time with behaviors ranging from weaker than linear, linear to stronger than linear. Furthermore, the elastic modulus and yield stress have been observed to be constant for some systems while time dependent for the others. We also analyze the experimental behavior through a viscoelastic thixotropic structural kinetic model that predicts the observed experimental behavior of constant as well as timedependent yield stress quite well. These findings indicate that a nonmonotonic steadystate flow curve in a structural kinetic formalism necessarily leads to timedependent yield stress, while constant yield stress is predicted by a monotonic steadystate flow curve with stress plateau in the limit of low shear rates. The present work, therefore, shows that thixotropic materials may exhibit either monotonic or nonmonotonic flow curves. Consequently, thixotropic materials may show no yield stress, constant yield stress, or timedependent yield stress.
Citation: Journal of Rheology
PubDate: 20230127T02:50:27Z
DOI: 10.1122/8.0000558

 Confined Brownian suspensions: Equilibrium diffusion, thermodynamics, and
rheology
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Authors: Alp M. Sunol, Roseanna N. Zia
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 433460, March 2023.
We examine the impact of confinement on the structure, dynamics, and rheology of spherically confined macromolecular suspensions, with a focus on the role played by entropic forces, by comparing the limits of strong hydrodynamics and no hydrodynamics. We present novel measurements of the osmotic pressure, intrinsic viscosity, and longtime selfdiffusivity in spherical confinement and find confinement induces strong structural correlations and restrictions on configurational entropy that drive up osmotic pressure and viscosity and drive down selfdiffusion. Even in the absence of hydrodynamics, confinement produces distinct shorttime and longtime selfdiffusion regimes. This finding revises the previous understanding that shorttime selfdiffusion is a purely hydrodynamic quantity. The entropic shorttime selfdiffusion is proportional to an entropic mobility, a direct analog to the hydrodynamic mobility. A caging plateau following the shorttime regime is stronger and more durable without hydrodynamics, and entropic drift—a gradient in volume fraction—drives particles out of their cages. The distinct longtime regime emerges when an entropic mobility gradient arising from heterogeneous distribution of particle volume drives particles out of local cages. We conclude that entropic mobility gradients produce a distinct longtime dynamical regime in confinement and that hydrodynamic interactions weaken this effect. From a statistical physics perspective, confinement restricts configurational entropy, driving up confined osmotic pressure, viscosity, and (inverse) longtime dynamics as confinement tightens. We support this claim by rescaling the volume fraction as the distance from confinementdependent maximum packing, which collapses the data for each rheological measure onto a single curve.
Citation: Journal of Rheology
PubDate: 20230123T01:22:50Z
DOI: 10.1122/8.0000520

 Particle migration of suspensions in a pressuredriven flow over and
through a porous structure
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Authors: Parisa Mirbod, Nina C. Shapley
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 417432, March 2023.
Laboratory experiments were conducted to study particle migration and flow properties of nonBrownian, noncolloidal suspensions ranging from 10% to 40% particle volume fraction in a pressuredriven flow over and through a porous structure at a low Reynolds number. Particle concentration maps, velocity maps, and corresponding profiles were acquired using a magnetic resonance imaging technique. The model porous medium consists of square arrays of circular rods oriented across the flow in a rectangular microchannel. It was observed that the square arrays of the circular rods modify the velocity profiles and result in heterogeneous concentration fields for various suspensions. As the bulk particle volume fraction of the suspension increases, particles tend to concentrate in the free channel relative to the porous medium while the centerline velocity profile along the lateral direction becomes increasingly blunted. Within the porous structure, concentrated suspensions exhibit smaller periodic axial velocity variations due to the geometry compared to semidilute suspensions (bulk volume fraction ranges from 10% to 20%) and show periodic concentration variations, where the average particle concentration is slightly greater between the rods than on top of the rods. For concentrated systems, high particle concentration pathways aligned with the flow direction are observed in regions that correspond to gaps between rods within the porous medium.
Citation: Journal of Rheology
PubDate: 20230120T01:12:11Z
DOI: 10.1122/8.0000505

 Complex polymer topologies in blends: Shear and elongational rheology of
linear/pompom polystyrene blends
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Authors: V. Hirschberg, S. Lyu, M. G. Schußmann
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 403415, March 2023.
The shear and elongational rheology of linear and pompom shaped polystyrene (PS) blends was investigated experimentally and modeled using constitutive models such as the Doi–Edwards and the molecular stress function (MSF) model. The pompom molecule is the simplest topology to combine shear thinning with strain hardening in elongational flow. A PS pompom with a selfentangled backbone (Mw,bb = 280 kg mol−1) and 22 entangled sidearms (Mw,a = 22 kg mol−1) at each star was blended with two linear PS with weight average molecular weights of Mw = 43 and 90 kg mol−1 and low polydispersities (Ð
Citation: Journal of Rheology
PubDate: 20230113T01:19:50Z
DOI: 10.1122/8.0000544

 Dilute polymer solutions under shear flow: Comprehensive qualitative
analysis using a beadspring chain model with a FENEFraenkel spring
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Authors: I. Pincus, A. Rodger, J. Ravi Prakash
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 373402, March 2023.
Although the nonequilibrium behavior of polymer solutions is generally well understood, particularly in extensional flow, there remain several unanswered questions for dilute solutions in simple shear flow, and full quantitative agreement with experiments has not been achieved. For example, experimental viscosity data exhibit qualitative differences in shearthinning exponents, the shear rate for the onset of shearthinning, and highshear Newtonian plateaus depending on polymer semiflexibility, contour length, and solvent quality. While polymer models are able to incorporate all of these effects through various spring force laws, bending potentials, excluded volume (EV) potentials, and hydrodynamic interaction (HI), the inclusion of each piece of physics has not been systematically matched to experimentally observed behavior. Furthermore, attempts to develop multiscale models (in the sense of representing an arbitrarily small or large polymer chain) which can make quantitative predictions are hindered by the lack of ability to fully match the results of beadrod models, often used to represent a polymer chain at the Kuhnstep level, with beadspring models, which take into account the entropic elasticity. In light of these difficulties, this work aims to develop a general model based on the socalled FENEFraenkel spring, originally formulated by Larson and coworkers [J. Chem. Phys. 124 (2006)], which can span the range from rigid rod to traditional entropic spring, as well as include a bending potential, EV, and HI. As we show, this model can reproduce, and smoothly move between, a wide range of previously observed polymer solution rheology in shear flow.
Citation: Journal of Rheology
PubDate: 20230113T01:19:48Z
DOI: 10.1122/8.0000517

 Viscous dissipation in large amplitude oscillatory shear of unsaturated
wet granular matter
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Authors: Ahmad Awdi, Camille Chateau, Franc̨ois Chevoir, JeanNoël Roux, Abdoulaye Fall
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 365372, March 2023.
The present work investigates nonlinear behavior in large amplitude oscillatory shear (LAOS) of unsaturated wet granular materials using pressureimposed rheometric measurements that enable to explore how the material properties characterizing the flow response depend on both strain amplitude and frequency of deformation. Away from the quasistatic limit, we show that the energy dissipated per unit volume in a single LAOS cycle, which can be visualized by the area enclosed by the Lissajous curve of stress versus strain, is an increasing function of the viscosity of the wetting liquid and is also influenced by the reduced pressure (comparing the cohesive to confining forces) and the frequency. Introducing the inertial number [math] and the viscous number [math] as previously done, it is shown that the influence of surface tension, viscosity, and driving frequency can be captured by plotting the dissipated energy per unit volume versus the viscous number: a good collapse is obtained. It is shown that an increase in liquid content shifts the whole curve of the dissipated energy upwards, indicating that the overall dissipation mechanism does not change with liquid content, only the energy dissipation related to the internal structure and its breakdown changes.
Citation: Journal of Rheology
PubDate: 20230112T12:37:45Z
DOI: 10.1122/8.0000507

 On the startup behavior of wormlike micellar networks: The effect of
different salts bound to the same surfactant molecule
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Authors: Rossana Pasquino, Pietro Renato Avallone, Salvatore Costanzo, Ionita Inbal, Dganit Danino, Vincenzo Ianniello, Giovanni Ianniruberto, Giuseppe Marrucci, Nino Grizzuti
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 353364, March 2023.
We report on shear startup data for two wormlike micellar solutions, differing only in concentration and type of two binding aromatic sodium salts. The surfactant molecule is cetylpiridinium chloride at a fixed concentration (100 mM). Sodium salicylate (NaSal) and diclofenac sodium (Diclo) are used as binding salts at concentrations 68 mM NaSal and 52 mM Diclo such that both systems are fully entangled and their linear viscoelastic response is essentially identical. Both systems show the linear response typical of a wormlike micellar solution, with terminal behavior at low frequencies, a welldefined moduli crossover, and a plateau modulus. In the nonlinear regime, however, the behavior of the two systems is totally different, suggesting that the molecular structure difference of the salts and their binding activity to the surfactant molecule are both crucial to determine the fast flow behavior. The NaSal solution shows a very complex rheological response, with strain hardening and very sharp stress peaks, whereas the solution containing Diclo behaves much like ordinary linear polymers, exhibiting pronounced overshoots as well as moderate undershoots in the transient shear viscosity, before approaching the steady state. This polymerlike behavior has also been proved by successfully comparing data with predictions of a constitutive equation recently adopted for both entangled polymers and linear wormlike micelles. As far as NaSal is concerned, a phenomenological model based on rubber network theory is developed, which describes the flow singularities. A physical interpretation of the different behavior in the nonlinear regime is also suggested.
Citation: Journal of Rheology
PubDate: 20230110T01:29:36Z
DOI: 10.1122/8.0000537

 Universal flowinduced orientational ordering of colloidal rods in planar
shear and extensional flows: Dilute and semidilute concentrations
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Authors: Byoungjin Chun, Hyun Wook Jung
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 315330, March 2023.
The design of flow processes to build a macroscopic bulk material from rodshaped colloidal particles has drawn considerable attention from researchers and engineers. Here, we systematically explore and show that the characteristic strain rate of the flow universally determines the orientational ordering of colloidal rods. We employed the fluctuating lattice Boltzmann method by simulating hydrodynamically interacting Brownian rods in a Newtonian liquid moving under various flow types. By modeling a rigid rod as a chain of nonoverlapping solid spheres with constraint forces and torque, we elucidate rigid rod dynamics with an aspect ratio ([math]) either 4.1 or 8.1 under various rotational Péclet number ([math]) conditions. The dynamics of colloidal rods in dilute ([math]) and semidilute suspensions ([math]) were simulated for a wide range of [math] ([math]) under shear flows including Couette and Poiseuille flows in a planar channel geometry, and an extensional and mixedkinematics flow in a periodic fourroll mill geometry, where [math] is the number density, and [math] and [math] are the diameter and length of the rod, respectively. By evaluating the degree of orientational alignment of rods along the flows, we observed that there is no significant difference between flow types, and the flowinduced ordering of rods depends on the variation of [math] up to moderate [math] ([math]). At a high [math] ([math]), the degree of orientational ordering is prone to diversify depending on the flow type. The spatial inhomogeneity of the strainrate distribution leads to a substantial decrease in the orientational alignment at high [math].
Citation: Journal of Rheology
PubDate: 20230109T11:54:16Z
DOI: 10.1122/8.0000550

 Instant yield stress measurement from falling drop size: The
“syringe test”
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Authors: A. Geffrault, H. BessaiesBey, N. Roussel, P. Coussot
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 305314, March 2023.
We analyze different flow regimes of a filament formed by extrusion of a material through a cylindrical die. We deduce that the elongational yield stress of a simple yield stress fluid (i.e., with negligible thixotropy effects) can be determined from the mass of the droplet after filament breakage and an estimation of the critical radius at pinchoff at the solidliquid regime transition. We demonstrate that such a simple characterization is relevant in a relatively wide range of extrusion velocities, i.e., this velocity slightly affects the drop mass in this range. For the simple yield stress fluids used, Carbopol gel, claywater paste at different concentrations, and emulsion, covering a large range of yield stress values (50–1000 Pa), the elongational yield stress appears to be equal to the simple shear yield stress times a factor equal to about [math]. As a consequence, this simple test may be used to obtain, almost instantaneously and without sophisticated apparatus (a syringe and a balance are sufficient), a good estimate of the shear yield stress of simple yield stress fluids. In that case, the main source of uncertainty (up to about 20%) is the value of the critical radius at the solidliquid transition. Finally, we review the operating conditions (material properties and extrusion characteristics) for which we can expect this approach to be valid.
Citation: Journal of Rheology
PubDate: 20230109T11:54:14Z
DOI: 10.1122/8.0000557

 Understanding the transient large amplitude oscillatory shear behavior of
yield stress fluids
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Authors: Krutarth M. Kamani, Gavin J. Donley, Rekha Rao, Anne M. Grillet, Christine Roberts, Abhishek Shetty, Simon A. Rogers
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 331352, March 2023.
A full understanding of the sequence of processes exhibited by yield stress fluids under large amplitude oscillatory shearing is developed using multiple experimental and analytical approaches. A novel component rate Lissajous curve, where the rates at which strain is acquired unrecoverably and recoverably are plotted against each other, is introduced and its utility is demonstrated by application to the analytical responses of four simple viscoelastic models. Using the component rate space, yielding and unyielding are identified by changes in the way strain is acquired, from recoverably to unrecoverably and back again. The behaviors are investigated by comparing the experimental results with predictions from the elastic Bingham model that is constructed using the Oldroyd–Prager formalism and the recently proposed continuous model by Kamani, Donley, and Rogers in which yielding is enhanced by rapid acquisition of elastic strain. The physical interpretation gained from the transient large amplitude oscillatory shear (LAOS) data is compared to the results from the analytical sequence of physical processes framework and a novel timeresolved Pipkin space. The component rate figures, therefore, provide an independent test of the interpretations of the sequence of physical processes analysis that can also be applied to other LAOS analysis frameworks. Each of these methods, the component rates, the sequence of physical processes analysis, and the timeresolved Pipkin diagrams, unambigiously identifies the same material physics, showing that yield stress fluids go through a sequence of physical processes that includes elastic deformation, gradual yielding, plastic flow, and gradual unyielding.
Citation: Journal of Rheology
PubDate: 20230109T11:54:14Z
DOI: 10.1122/8.0000583
