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Journal of Rheology
Journal Prestige (SJR): 1.326  Citation Impact (citeScore): 3 Number of Followers: 7  Subscription journalISSN (Print) 0148-6055 - ISSN (Online) 1520-8516 Published by Society of Rheology  [1 journal]
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- 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 579-588, 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 time-dependent 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: 2023-02-24T12:15:08Z
DOI: 10.1122/8.0000606
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- Microscopic activated dynamics theory of the shear rheology and stress
overshoot in ultradense glass-forming fluids and colloidal suspensions-
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Authors: Ashesh Ghosh, Kenneth S. Schweizer
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 559-578, March 2023.
We formulate a particle and force level, activated dynamics-based statistical mechanical theory for the continuous startup nonlinear shear rheology of ultradense glass-forming 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 local-nonlocal event involving caging and longer range collective elasticity which controls the characteristic stress relaxation time. Theoretical predictions for the deformation-induced enhancement of mobility, the onset of relaxation acceleration at remarkably low values of stress, strain, or shear rate, apparent power law thinning of the steady-state 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 steady-state 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 steady-state 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 deformation-assisted activated motion appears to be crucial for both the transient and steady-state responses.
Citation: Journal of Rheology
PubDate: 2023-02-21T04:35:03Z
DOI: 10.1122/8.0000546
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- Tribological variable-friction coefficient models for the simulation of
dense suspensions of rough polydisperse particles-
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Authors: Jose A. Ruiz-Lopez, Sagaya S. Prasanna Kumar, Adolfo Vazquez-Quesada, Juan de Vicente, Marco Ellero
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 541-558, March 2023.
The rheology of concentrated suspensions of particles is complex and typically exhibits a shear-thickening behavior in the case of repulsive interactions. Despite the recent interest arisen, the causes of the shear-thickening 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 (full-film 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 full-lubrication regime is governed by the particle average roughness. Particle-level simulations of suspensions of hard spheres were carried out using short-range lubrication and roughness-dependent 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 shear-thickening behavior; for sufficiently rough particles, the suspension exhibits a remarkable shear-thickening, while for sufficiently smooth particles, the discontinuous shear-thickening disappears.
Citation: Journal of Rheology
PubDate: 2023-02-16T01:29:45Z
DOI: 10.1122/8.0000514
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- Rheology of non-Brownian 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 517-540, March 2023.
The shear rheology of particle suspensions in shear-thinning 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 shear-thickening to substantially shear-thinning as the degree of shear-thinning of the suspending fluid increases. Moreover, in highly shear-thinning fluids, the suspension exhibits greater shear-thinning of the viscosity than the suspending fluid itself. Our dilute body-fitted simulations show that in the absence of hydrodynamic interactions, shear-thinning can arise from the particle-induced 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 shear-thinning stresslet, this effect creates an overall shear-thinning of the viscosity. We then explore the effects of particle-particle interactions on the suspension rheology using immersed boundary simulations. We show that multiparticle simulations are necessary to obtain the shear-thinning behavior of the per-particle viscosity of suspensions in shear-thinning fluids at moderate values of [math]. Particle-particle interactions lead to a substantial decrease in the PIFS and an enhancement of the shear-thinning of the stresslet compared to the single particle simulations. This combination leads to the shear-thinning of the per-particle viscosity seen in experiments. We also find that very low values of [math] and finite values of [math] have opposing effects on the per-particle viscosity that can lead to a nonmonotonic per-particle viscosity versus shear rate in a highly shear-thinning fluid. Overall, the addition of rigid particles to highly shear-thinning fluids, such as joint synovial fluid, leads to increased viscosity and also increased shear-thinning at high shear rates.
Citation: Journal of Rheology
PubDate: 2023-02-13T12:32:13Z
DOI: 10.1122/8.0000541
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- Rheology of non-Brownian 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 499-516, 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 Oldroyd-B model. We compare the bulk rheology using immersed boundary simulations at [math] and [math] to body-fitted single-particle simulations and find that the per-particle viscosity and first normal stress difference coefficient are always shear-thickening 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 particle-particle 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 single-particle 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 shear-thickening 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: 2023-02-13T12:32:12Z
DOI: 10.1122/8.0000540
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- 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 479-497, 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 time-evolving or mutating material, the build-up or breakdown of microstructure is commonly both time- and shear-rate (or shear-stress) 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 time-translation invariant, which constrains the mutation number of the material to be extremely small. This constraint makes it difficult to accurately study shear-induced microstructural changes in thixotropic and gelling materials, and it is becoming increasingly important to develop more advanced signal processing techniques capable of robustly extracting time-resolved frequency information from oscillatory data. In this work, we explore applications of the Gabor transform (a short-time Fourier transform combined with a Gaussian window), for providing optimal joint time-frequency 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 amplitude-modulated 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 (Gabor-transformed oscillatory shear rheometry). This unconventional, but easily implemented, rheometric approach facilitates both SAOS and LAOS studies of time-evolving materials, reducing the number of required experiments and the data postprocessing time significantly.
Citation: Journal of Rheology
PubDate: 2023-02-03T12:59:01Z
DOI: 10.1122/8.0000549
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- 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 461-477, 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 power-law 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 time-dependent yield stress quite well. These findings indicate that a nonmonotonic steady-state flow curve in a structural kinetic formalism necessarily leads to time-dependent yield stress, while constant yield stress is predicted by a monotonic steady-state 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 time-dependent yield stress.
Citation: Journal of Rheology
PubDate: 2023-01-27T02:50:27Z
DOI: 10.1122/8.0000558
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- 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 433-460, 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 long-time self-diffusivity 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 self-diffusion. Even in the absence of hydrodynamics, confinement produces distinct short-time and long-time self-diffusion regimes. This finding revises the previous understanding that short-time self-diffusion is a purely hydrodynamic quantity. The entropic short-time self-diffusion is proportional to an entropic mobility, a direct analog to the hydrodynamic mobility. A caging plateau following the short-time regime is stronger and more durable without hydrodynamics, and entropic drift—a gradient in volume fraction—drives particles out of their cages. The distinct long-time 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 long-time 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) long-time dynamics as confinement tightens. We support this claim by rescaling the volume fraction as the distance from confinement-dependent maximum packing, which collapses the data for each rheological measure onto a single curve.
Citation: Journal of Rheology
PubDate: 2023-01-23T01:22:50Z
DOI: 10.1122/8.0000520
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- Particle migration of suspensions in a pressure-driven 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 417-432, March 2023.
Laboratory experiments were conducted to study particle migration and flow properties of non-Brownian, noncolloidal suspensions ranging from 10% to 40% particle volume fraction in a pressure-driven 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: 2023-01-20T01:12:11Z
DOI: 10.1122/8.0000505
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- Complex polymer topologies in blends: Shear and elongational rheology of
linear/pom-pom polystyrene blends-
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Authors: V. Hirschberg, S. Lyu, M. G. Schußmann
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 403-415, March 2023.
The shear and elongational rheology of linear and pom-pom 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 pom-pom molecule is the simplest topology to combine shear thinning with strain hardening in elongational flow. A PS pom-pom with a self-entangled 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: 2023-01-13T01:19:50Z
DOI: 10.1122/8.0000544
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- Dilute polymer solutions under shear flow: Comprehensive qualitative
analysis using a bead-spring chain model with a FENE-Fraenkel spring-
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Authors: I. Pincus, A. Rodger, J. Ravi Prakash
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 373-402, 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 shear-thinning exponents, the shear rate for the onset of shear-thinning, and high-shear 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 bead-rod models, often used to represent a polymer chain at the Kuhn-step level, with bead-spring models, which take into account the entropic elasticity. In light of these difficulties, this work aims to develop a general model based on the so-called FENE-Fraenkel spring, originally formulated by Larson and co-workers [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: 2023-01-13T01:19:48Z
DOI: 10.1122/8.0000517
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- Viscous dissipation in large amplitude oscillatory shear of unsaturated
wet granular matter-
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Authors: Ahmad Awdi, Camille Chateau, Franc̨ois Chevoir, Jean-Noël Roux, Abdoulaye Fall
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 365-372, March 2023.
The present work investigates nonlinear behavior in large amplitude oscillatory shear (LAOS) of unsaturated wet granular materials using pressure-imposed 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: 2023-01-12T12:37:45Z
DOI: 10.1122/8.0000507
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- 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 353-364, 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 well-defined 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: 2023-01-10T01:29:36Z
DOI: 10.1122/8.0000537
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- Universal flow-induced 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 315-330, March 2023.
The design of flow processes to build a macroscopic bulk material from rod-shaped 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 mixed-kinematics flow in a periodic four-roll 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 flow-induced 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 strain-rate distribution leads to a substantial decrease in the orientational alignment at high [math].
Citation: Journal of Rheology
PubDate: 2023-01-09T11:54:16Z
DOI: 10.1122/8.0000550
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- Instant yield stress measurement from falling drop size: The
“syringe test”-
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Authors: A. Geffrault, H. Bessaies-Bey, N. Roussel, P. Coussot
Abstract: Journal of Rheology, Volume 67, Issue 2, Page 305-314, 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 pinch-off at the solid-liquid 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, clay-water 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 solid-liquid 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: 2023-01-09T11:54:14Z
DOI: 10.1122/8.0000557
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- 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 331-352, 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 time-resolved 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 time-resolved 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: 2023-01-09T11:54:14Z
DOI: 10.1122/8.0000583
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