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Rheometer

About: Rheometer is a research topic. Over the lifetime, 5759 publications have been published within this topic receiving 125849 citations.


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Journal ArticleDOI
Roger W. Chan1
TL;DR: This study investigated the feasibility of an alternative approach for data extrapolation, namely the principle of time-temperature superposition (TTS), and showed that TTS may be a feasible approach for estimating the viscoelastic shear properties of vocal-fold tissues at frequencies of phonation
Abstract: Empirical data on the viscoelastic shear properties of human vocal-fold mucosa (cover) were recently reported at relatively low frequency (0.01–15 Hz). For the data to become relevant to voice production, attempts have been made to parametrize and extrapolate the data to higher frequencies using constitutive modeling [Chan and Titze, J. Acoust. Soc. Am. 107, 565–580 (2000)]. This study investigated the feasibility of an alternative approach for data extrapolation, namely the principle of time–temperature superposition (TTS). TTS is a hybrid theoretical–empirical approach widely used by rheologists to estimate the viscoelastic properties of polymeric systems at time or frequency scales not readily accessible experimentally. It is based on the observation that for many polymers, the molecular configurational changes that occur in a given time scale at a low temperature correspond to those that occur in a shorter time scale at a higher temperature. Using a rotational rheometer, the elastic shear modulus (G′)...

40 citations

Journal ArticleDOI
01 Oct 2004
TL;DR: The observations suggest that the instability studied here is subcritical and leads to a flow that is oscillatory and far from viscometric, useful in applications such as microfluidics, membrane separations, and polymer processing.
Abstract: We perform a set of experiments to study the nonlinear nature of an instability that arises in low-Reynolds-number flow past polymer gels. A layer of a viscous liquid is placed on a polydimethylsiloxane (PDMS) gel in a parallel-plate rheometer which is operated in stress-controlled mode. As the shear stress on the top plate increases, the apparent viscosity stays relatively constant until a transition stress where it sharply increases. If the stress is held at a level slightly above the transition stress, the apparent viscosity oscillates with time. If the stress is increased to a value above the transition stress and then decreased back to zero, the apparent viscosity shows hysteretic behavior. If the stress is instead decreased to a constant value and held there, the apparent viscosity is different from its pretransition value and exhibits sustained oscillations. This can happen even if the stress is held at values below the transition stress. Our observations suggest that the instability studied here is subcritical and leads to a flow that is oscillatory and far from viscometric. The phenomena reported here may be useful in applications such as microfluidics, membrane separations, and polymer processing. They may also provide insight into the rheological behavior of complex fluids that undergo flow-induced gelation.

40 citations

Journal ArticleDOI
TL;DR: The results show the potential of high frequency rheometry for analyzing subtle differences in rheology of pharmaceutically relevant protein solutions at microliter volume.

40 citations

Journal ArticleDOI
TL;DR: In this article, the hydraulic properties of free-surface flows of viscoplastic fluids were investigated in an inclined conveyor-belt channel allowing us to generate gravity-driven surges which remain stationary in the laboratory frame.
Abstract: We present experimental results focused on the hydraulic properties of free-surface flows of viscoplastic fluids. The objective is to investigate the possibility of predicting macroscopic flow properties on the base of conventional rheometrical characterization of the fluids. The experiments are performed in an inclined conveyor-belt channel allowing us to generate gravity-driven surges which remain stationary in the laboratory frame. Two different types of materials are studied: Kaolin slurries and Carbopol microgels. Global height–velocity relationships and local velocity profiles are measured in the uniform zone for different experimental conditions (slope angle, rheological parameters). These data are then compared to theoretical predictions based on the Herschel–Bulkley constitutive law and independent measurements of the rheological parameters. Great care has been devoted to the determination of experimental uncertainties, including those associated with the rheometrical characterization. For Kaolin, the experimental results show excellent agreement with theoretical predictions. With Carbopol, on the contrary, a systematic discrepancy between measured and theoretical flow heights is observed. The velocity profiles do nevertheless remain consistent with a Herschel–Bulkley rheology, and we show that all experimental data can be explained by increasing the rheological parameters (yield stress and consistency) by 10–20 % compared to the values measured in the rheometer. Potential interpretations for this discrepancy are discussed.

40 citations

Journal ArticleDOI
01 Jan 2002
TL;DR: In this paper, a review of the relevant rheology literature is reviewed, focusing on the properties of thin films of low molecular weight liquids at elevated pressures, including shear thinning, viscoelasticity and cohesive failure.
Abstract: Thin liquid films at elevated pressures have a unique property. A sufficiently high shear stress can be generated in steady shear without encountering the thermal softening limit or interfacial slip that it is possible to observe, in low molecular weight liquids, various non-Newtonian effects ordinarily thought to be reserved for high polymers. These include shear thinning, viscoelasticity and cohesive failure. The relevant rheology literature is reviewed. Only the properties of the continuum are addressed here, omitting near-surface effects.Within the last 10 years in particular, both experiment and molecular simulation have shown that many analogies may be made between lubricants and liquid polymers when allowance is made for the much shorter relaxation time of the low molecular weight liquid. Shear thinning, elasticity and liquid failure are all aspects of the shear response of thin films of low molecular weight liquids at elevated pressures.

40 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023240
2022487
2021164
2020196
2019201
2018162