Extending yield-stress fluid paradigms

Nelson, Arif Z.; Bras, Rafael E.; Liu, Jingping; Ewoldt, Randy H.

doi:10.1122/1.5003841

Cited by 46 publications

(61 citation statements)

References 44 publications

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“…Yield stress materials can be classified according to their microstructure as repulsive-dominated jammed glasses, networked gels with attractive interactions or a combination thereof [39,40]. According to [39], Carbopol gels are classified into the first category.…”

Section: Introductionmentioning

confidence: 99%

Rheological Characterization of Carbopol® Dispersions in Water and in Water/Glycerol Solutions

Varges

Costa

Fonseca

et al. 2019

Fluids

116

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The influence of the solvent type on the rheological properties of Carbopol ® NF 980 dispersions in water and in water/glycerol solutions is investigated. The material formulation, preparation procedure, common experimental challenges and artifact sources are all addressed. Transient and steady-state experiments were performed. For both solvent types, a clearly thixotropic behavior occurs slightly above the yield stress, where the avalanche effect is observed. For larger stresses, thixotropy is always negligible. Among other findings, it is observed that, for a given Carbopol concentration, the dispersion in the more viscous solvent possesses a lower yield stress and moduli, a larger power-law index, and a longer time to reach steady state.

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Section: Introductionmentioning

confidence: 99%

Rheological Characterization of Carbopol® Dispersions in Water and in Water/Glycerol Solutions

Varges

Costa

Fonseca

et al. 2019

Fluids

116

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“…Editor: Nam H. Kim. materials where material function targets are chosen to optimize performance. Only once the necessary properties are selected, the design of the necessary rheologically complex material can begin, wherein the required material structure or formulation can be chosen to meet these needs [25,26]. Thus, the strategy is to be problem-driven rather than solution-driven.…”

Section: Introductionmentioning

confidence: 99%

“…This paper focuses on a methodology for answering that question with linear viscoelastic materials/systems including the nontrivial problem of selecting design-appropriate modeling using material properties (represented by the right, curved, upward arrow). Successful identification of targeted properties then leads to microstructure and formulation design (material selection or material synthesis) [25][26][27][28], which is beyond the scope of the work here. Fig.…”

Section: Introductionmentioning

confidence: 99%

Setting Material Function Design Targets for Linear Viscoelastic Materials and Structures

Corman

Rao

Bharadwaj

et al. 2016

Journal of Mechanical Design

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Rheologically complex materials are described by function-valued properties with dependence on a timescale (linear viscoelasticity), input amplitude (nonlinear material behavior), or more generally both (nonlinear viscoelasticity). This complexity presents a difficulty when trying to utilize these material systems in engineering designs. Here, we focus on linear viscoelasticity and a methodology to identify the desired viscoelastic behavior. This is an early-stage design step to optimize target (function-valued) properties before choosing or synthesizing a real material. In linear viscoelasticity, it is not obvious which properties can be treated as independent design variables. Thus, it is nontrivial to select the most design-appropriate constitutive model, to be as general as possible, but not violate fundamental restrictions. We use the Kramers–Kronig constraint to show that frequency-dependent moduli (e.g., shear moduli G′(ω) and G″(ω)) cannot be treated as two independent design variables. Rather, a single function such as the relaxation modulus (e.g., K(t) for force-relaxation or G(t) for stress relaxation) is an appropriate function-valued design variable. A simple case study is used to demonstrate the framework in which we identify target properties for a vibration isolation system. Viscoelasticity improves performance. Different parameterizations of the kernel function are optimized and compared for performance. While parameterization may limit the generality of the kernel function, we do include a nonobvious representation (power law) that is found in real viscoelastic material systems and in the spring-dashpot paradigm would require an infinite number of components. Our methodology provides a means to answer the question, “What viscoelastic properties are desirable?” This ability to identify targeted behavior will be useful for subsequent stages of the design process including the selection or synthesis of real materials.

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“…Particular attention has been devoted to oil-extraction, drilling muds and transport of waxy oils in pipe-lines [14][15][16]. Recent studies point out the necessity of a viscoelastic contribution in characterising previously-considered simple yield-stress materials as Carbopol in particle-settling and other complex flows, where a combination of shear and extensional deformations promote viscoelastoplastic and thixotropic response [17][18][19][20], and for which novel measurements of extensionally-active features are of importance [21]. Moreover, plastic-to-liquid like transition has been considered as a consequence of a dynamic structure-destruction and reformation, hence, introducing a thixotropic ingredient to explain such a response [15,22].…”

Section: Introductionmentioning

confidence: 99%

Predictions for circular contraction-expansion flows with viscoelastoplastic & thixotropic fluids

López-Aguilar

Webster

Tamaddon-Jahromi

et al. 2018

Journal of Non-Newtonian Fluid Mechanics

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In this predominately predictive modelling finite volume/element study, a comparative analysis is performed for time-dependent and viscoelastoplastic flow in a circular contraction-expansion geometry of aspect-ratio 10:1:10. For this, a hybrid finite volume/element scheme is employed. A new and revised micellar model is investigated, under the denomination of BMP+_p, which reflects a bounded extensional viscosity response and an N1Shear-upturn at large deformation rates (lost in earlier model-variants), a versatile model capable of supporting plasticity, shear-thinning, strain softeninghardening and shear-banding. Many of these features are common to wormlike micellar and polymer solutions. Then, findings are contrasted against a De Souza model. Two flow regimes are addressed: plastic flow (low flow-rate Q≤1 units, solvent-fraction <10-2) and viscoelastic flow (larger-Q>1; minimised plasticity; =1/9); as quantified via flow-structure, yield-fronts and pressure-drops. Under the plastic regime, elasticity-increase causes asymmetry about the contraction-plane, whilst yieldstress and enhanced strain-hardening promote solid-like features, apparent through augmented unyielded-regions and rising pressure-drops. Concerning the viscoelastic regime and vortexstructures, extensional-deformation experienced correlates with hardening expectation in uniaxialextension, whilst streamline activity in vortex-cells correlates with normal-stress response in shear. Adjustment in strain-hardening/softening response with Q-rise, provides translation from weaker salient-corner vortex centres to stronger elastic corner-vortices; yet, when softening finally prevails, asymmetric upstream/downstream salient-corners vortex patterns are recovered. For strong-hardening and solvent-dominated ~0.8 fluids (as with Boger fluids), an intermediate lip-vortex-formation phase is noted, alongside coexistence of salient-corner vortices. Such a vortex-coexistence phase is distinctly absent in solute-concentrated fluids.

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Extending yield-stress fluid paradigms

Cited by 46 publications

References 44 publications

Rheological Characterization of Carbopol® Dispersions in Water and in Water/Glycerol Solutions

Rheological Characterization of Carbopol® Dispersions in Water and in Water/Glycerol Solutions

Setting Material Function Design Targets for Linear Viscoelastic Materials and Structures

Predictions for circular contraction-expansion flows with viscoelastoplastic & thixotropic fluids

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