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Daniel Bonn - One of the best experts on this subject based on the ideXlab platform.
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Yield Stress materials in soft condensed matter
Reviews of Modern Physics, 2017Co-Authors: Daniel Bonn, Morton M. Denn, Ludovic Berthier, Thibaut Divoux, Sebastien MannevilleAbstract:A comprehensive review is presented of the physical behavior of Yield Stress materials in soft condensed matter, which encompasses a broad range of materials from colloidal assemblies and gels to emulsions and non-Brownian suspensions. All these disordered materials display a nonlinear flow behavior in response to external mechanical forces due to the existence of a finite force threshold for flow to occur: the Yield Stress. Both the physical origin and rheological consequences associated with this nonlinear behavior are discussed and an overview is given of experimental techniques available to measure the Yield Stress. Recent progress is discussed concerning a microscopic theoretical description of the flow dynamics of Yield Stress materials, emphasizing, in particular, the role played by relaxation time scales, the interplay between shear flow and aging behavior, the existence of inhomogeneous shear flows and shear bands, wall slip, and nonlocal effects in confined geometries.
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On different ways of measuring “the” Yield Stress
Journal of Non-newtonian Fluid Mechanics, 2016Co-Authors: M. Dinkgreve, José Paredes, Morton M. Denn, Daniel BonnAbstract:Yield Stress materials are ubiquitous, yet the best way to obtain the value of the Yield Stress for any given material has been the subject of considerable debate. Here we compare different methods of measuring the Yield Stress with conventional rheometers that have been used in the literature on a variety of materials. The main conclusion is that, at least for well-behaved (non-thixotropic) materials, the differences between the various methods are significant; on the other hand, the scaling of the measured Yield Stress with the volume fraction of dispersed phase shows the same dependence independently of the way in which the Yield Stress is obtained experimentally. The measured Yield strain is similarly found to depend on the method employed. The Yield Stress values obtained for a simple (non-thixotropic) Yield Stress fluid are only similar for Herschel–Bulkley fits and Stress-strain curves obtained from oscillatory measurements. Stress-strain curves with a continuous imposed Stress or strain rate differ significantly, as do oscillatory measurements of the crossover between G′ and G″ or the point where G′ starts to differ significantly from its linear response value. The intersection of the G′ and G″ curves as a function of strain consistently give the highest value of the Yield Stress and Yield strain. In addition, many of these criteria necessitate some arbitrary definition of a crossover point. Similar conclusions apply for a class of thixotropic Yield Stress materials, with the Stress-strain curve from the oscillatory data giving the dynamic Yield Stress and the Herschel–Bulkley fit either the static or dynamic Yield Stress, depending on how the measurement is carried out.
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Coiling of Yield Stress fluids.
Physical review. E Statistical nonlinear and soft matter physics, 2011Co-Authors: Yasser Rahmani, Mehdi Habibi, Arman Javadi, Daniel BonnAbstract:We present an experimental investigation of the coiling of a filament of a Yield Stress fluid falling on a solid surface. We use two kinds of Yield Stress fluids, shaving foam and hair gel, and show that the coiling of the foam is similar to the coiling of an elastic rope. Two regimes of coiling (elastic and gravitational) are observed for the foam. Hair gel coiling, on the other hand, is more like the coiling of a liquid system; here we observe viscous and gravitational regimes. No inertial regime is observed for either system because of instabilities occurring at high flow rates or the breakup of the filament from large heights.
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Issues in the flow of Yield-Stress liquids
Rheologica Acta, 2010Co-Authors: Morton M. Denn, Daniel BonnAbstract:Yield-Stress liquids are materials that are solid below a critical applied Stress and flow like mobile liquids at higher Stresses. Classical descriptions of Yield-Stress liquids, which have been the basis for asymptotic and computational studies for five decades, are inadequate to describe many recent experimental observations, and it is clear that the time dependence of microstructure must be taken into account in the description of many real Yield-Stress liquids.
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an attempt to categorize Yield Stress fluid behaviour
Philosophical Transactions of the Royal Society A, 2009Co-Authors: Peder Moller, Abdoulaye Fall, Vijayakumar Chikkadi, Didi Derks, Daniel BonnAbstract:We propose a new view on Yield Stress materials. Dense suspensions and many other materials have a Yield Stress—they flow only if a large enough shear Stress is exerted on them. There has been an ongoing debate in the literature on whether true Yield Stress fluids exist, and even whether the concept is useful. This is mainly due to the experimental difficulties in determining the Yield Stress. We show that most if not all of these difficulties disappear when a clear distinction is made between two types of Yield Stress fluids: thixotropic and simple ones. For the former, adequate experimental protocols need to be employed that take into account the time evolution of these materials: ageing and shear rejuvenation. This solves the problem of experimental determination of the Yield Stress. Also, we show that true Yield Stress materials indeed exist, and in addition, we account for shear banding that is generically observed in Yield Stress fluids.
Koen Dewettinck - One of the best experts on this subject based on the ideXlab platform.
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chocolate Yield Stress as measured by oscillatory rheology
Food Research International, 2011Co-Authors: V. Graef, Frédéric Depypere, Maaike Minnaert, Koen DewettinckAbstract:Abstract Liquid chocolate exhibits a non-Newtonian flow behavior that is conventionally characterized by a Yield Stress and plastic viscosity. In general, Yield Stress is determined by shear rheology experiments and the data are plotted as viscosity as a function of shear Stress or shear Stress as a function of shear rate. For the shear Stress-shear rate plot, a frequently used approach to estimate the Yield Stress is to fit the data to one of several established models, with the Casson model being the most popular. Even though ICA (former IOCCC) recommendation is not to use the Casson model, it is still frequently applied. With the Casson model, a good fit to the experimental data for the shear rate ranging from 5 s − 1 to 60 s − 1 is realized. However, this model is unable to resolve real differences between chocolate samples that manifest at shear rate values below 5 s − 1 . In this study, oscillatory rheology was applied and the Stress at the end of the linear viscoelastic region (LVR) was taken as an estimate for the Yield Stress. This method was shown to be sensitive to fat content, emulsifier concentration and type of emulsifier. Furthermore, oscillatory rheology was found to be capable to capture differences in Yield Stress of chocolates that were not differentiated using the Casson model fitting approach.
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Chocolate Yield Stress as measured by oscillatory rheology
Food Research International, 2011Co-Authors: V. Graef, Frédéric Depypere, Maaike Minnaert, Koen DewettinckAbstract:Liquid chocolate exhibits a non-Newtonian flow behavior that is conventionally characterized by a Yield Stress and plastic viscosity. In general, Yield Stress is determined by shear rheology experiments and the data are plotted as viscosity as a function of shear Stress or shear Stress as a function of shear rate. For the shear Stress-shear rate plot, a frequently used approach to estimate the Yield Stress is to fit the data to one of several established models, with the Casson model being the most popular. Even though ICA (former IOCCC) recommendation is not to use the Casson model, it is still frequently applied. With the Casson model, a good fit to the experimental data for the shear rate ranging from 5s-1to 60s-1is realized. However, this model is unable to resolve real differences between chocolate samples that manifest at shear rate values below 5s-1. In this study, oscillatory rheology was applied and the Stress at the end of the linear viscoelastic region (LVR) was taken as an estimate for the Yield Stress. This method was shown to be sensitive to fat content, emulsifier concentration and type of emulsifier. Furthermore, oscillatory rheology was found to be capable to capture differences in Yield Stress of chocolates that were not differentiated using the Casson model fitting approach. © 2011 Elsevier Ltd.
V. Graef - One of the best experts on this subject based on the ideXlab platform.
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chocolate Yield Stress as measured by oscillatory rheology
Food Research International, 2011Co-Authors: V. Graef, Frédéric Depypere, Maaike Minnaert, Koen DewettinckAbstract:Abstract Liquid chocolate exhibits a non-Newtonian flow behavior that is conventionally characterized by a Yield Stress and plastic viscosity. In general, Yield Stress is determined by shear rheology experiments and the data are plotted as viscosity as a function of shear Stress or shear Stress as a function of shear rate. For the shear Stress-shear rate plot, a frequently used approach to estimate the Yield Stress is to fit the data to one of several established models, with the Casson model being the most popular. Even though ICA (former IOCCC) recommendation is not to use the Casson model, it is still frequently applied. With the Casson model, a good fit to the experimental data for the shear rate ranging from 5 s − 1 to 60 s − 1 is realized. However, this model is unable to resolve real differences between chocolate samples that manifest at shear rate values below 5 s − 1 . In this study, oscillatory rheology was applied and the Stress at the end of the linear viscoelastic region (LVR) was taken as an estimate for the Yield Stress. This method was shown to be sensitive to fat content, emulsifier concentration and type of emulsifier. Furthermore, oscillatory rheology was found to be capable to capture differences in Yield Stress of chocolates that were not differentiated using the Casson model fitting approach.
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Chocolate Yield Stress as measured by oscillatory rheology
Food Research International, 2011Co-Authors: V. Graef, Frédéric Depypere, Maaike Minnaert, Koen DewettinckAbstract:Liquid chocolate exhibits a non-Newtonian flow behavior that is conventionally characterized by a Yield Stress and plastic viscosity. In general, Yield Stress is determined by shear rheology experiments and the data are plotted as viscosity as a function of shear Stress or shear Stress as a function of shear rate. For the shear Stress-shear rate plot, a frequently used approach to estimate the Yield Stress is to fit the data to one of several established models, with the Casson model being the most popular. Even though ICA (former IOCCC) recommendation is not to use the Casson model, it is still frequently applied. With the Casson model, a good fit to the experimental data for the shear rate ranging from 5s-1to 60s-1is realized. However, this model is unable to resolve real differences between chocolate samples that manifest at shear rate values below 5s-1. In this study, oscillatory rheology was applied and the Stress at the end of the linear viscoelastic region (LVR) was taken as an estimate for the Yield Stress. This method was shown to be sensitive to fat content, emulsifier concentration and type of emulsifier. Furthermore, oscillatory rheology was found to be capable to capture differences in Yield Stress of chocolates that were not differentiated using the Casson model fitting approach. © 2011 Elsevier Ltd.
Wallace Woon Fong Leung - One of the best experts on this subject based on the ideXlab platform.
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Measurement of low Yield-Stress materials
Journal of The Chinese Institute of Chemical Engineers, 2008Co-Authors: Wallace Woon Fong LeungAbstract:Abstract A special method has been devised to measure Yield Stress of biosolids material or cake. A material with Yield Stress is placed in a container initially resting on its base. By slowly rotating the container 90° incrementally under “quasi-equilibrium”, the profile of the material is reformed in which the height is deeper on one end and shallower on the opposite end. To measure material with low Yield Stress, an immiscible lighter liquid is introduced with the material fully immersed in the pool of the lighter liquid and the above procedure is repeated. Also the dimension of the side of the container should be much greater that of the base. Despite the Yield Stress of the material is small the interface profile between the lighter liquid and the material can be established under reduced weight due to buoyancy force of the lighter liquid. The measured material profile is compared with the theoretical prediction based on a model assuming the material establishes a hydrostatic equilibrium in its final position with the container resting on its side. The effective density used in the test is the density difference between the lighter liquid and the material, which can be made small, catered for measuring material with very low Yield Stress. The new method was used to measure xanthan gum with low Yield Stress with magnitude less than 1 Pa. The cross sectional shape of the container affects the measurement and the subsequent interpretation. Both rectangular and cylindrical geometries have been investigated and both give comparable Yield Stress for the xanthan gum being tested. The proposed method is attractive for providing reasonable and accurate measurement despite its simplicity.
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Measurement of low Yield-Stress materials
Journal of the Chinese Institute of Chemical Engineers, 2008Co-Authors: Wallace Woon Fong LeungAbstract:A special method has been devised to measure Yield Stress of biosolids material or cake. A material with Yield Stress is placed in a container initially resting on its base. By slowly rotating the container 90° incrementally under "quasi-equilibrium", the profile of the material is reformed in which the height is deeper on one end and shallower on the opposite end. To measure material with low Yield Stress, an immiscible lighter liquid is introduced with the material fully immersed in the pool of the lighter liquid and the above procedure is repeated. Also the dimension of the side of the container should be much greater that of the base. Despite the Yield Stress of the material is small the interface profile between the lighter liquid and the material can be established under reduced weight due to buoyancy force of the lighter liquid. The measured material profile is compared with the theoretical prediction based on a model assuming the material establishes a hydrostatic equilibrium in its final position with the container resting on its side. The effective density used in the test is the density difference between the lighter liquid and the material, which can be made small, catered for measuring material with very low Yield Stress. The new method was used to measure xanthan gum with low Yield Stress with magnitude less than 1 Pa. The cross sectional shape of the container affects the measurement and the subsequent interpretation. Both rectangular and cylindrical geometries have been investigated and both give comparable Yield Stress for the xanthan gum being tested. The proposed method is attractive for providing reasonable and accurate measurement despite its simplicity. © 2008 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Frédéric Depypere - One of the best experts on this subject based on the ideXlab platform.
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chocolate Yield Stress as measured by oscillatory rheology
Food Research International, 2011Co-Authors: V. Graef, Frédéric Depypere, Maaike Minnaert, Koen DewettinckAbstract:Abstract Liquid chocolate exhibits a non-Newtonian flow behavior that is conventionally characterized by a Yield Stress and plastic viscosity. In general, Yield Stress is determined by shear rheology experiments and the data are plotted as viscosity as a function of shear Stress or shear Stress as a function of shear rate. For the shear Stress-shear rate plot, a frequently used approach to estimate the Yield Stress is to fit the data to one of several established models, with the Casson model being the most popular. Even though ICA (former IOCCC) recommendation is not to use the Casson model, it is still frequently applied. With the Casson model, a good fit to the experimental data for the shear rate ranging from 5 s − 1 to 60 s − 1 is realized. However, this model is unable to resolve real differences between chocolate samples that manifest at shear rate values below 5 s − 1 . In this study, oscillatory rheology was applied and the Stress at the end of the linear viscoelastic region (LVR) was taken as an estimate for the Yield Stress. This method was shown to be sensitive to fat content, emulsifier concentration and type of emulsifier. Furthermore, oscillatory rheology was found to be capable to capture differences in Yield Stress of chocolates that were not differentiated using the Casson model fitting approach.
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Chocolate Yield Stress as measured by oscillatory rheology
Food Research International, 2011Co-Authors: V. Graef, Frédéric Depypere, Maaike Minnaert, Koen DewettinckAbstract:Liquid chocolate exhibits a non-Newtonian flow behavior that is conventionally characterized by a Yield Stress and plastic viscosity. In general, Yield Stress is determined by shear rheology experiments and the data are plotted as viscosity as a function of shear Stress or shear Stress as a function of shear rate. For the shear Stress-shear rate plot, a frequently used approach to estimate the Yield Stress is to fit the data to one of several established models, with the Casson model being the most popular. Even though ICA (former IOCCC) recommendation is not to use the Casson model, it is still frequently applied. With the Casson model, a good fit to the experimental data for the shear rate ranging from 5s-1to 60s-1is realized. However, this model is unable to resolve real differences between chocolate samples that manifest at shear rate values below 5s-1. In this study, oscillatory rheology was applied and the Stress at the end of the linear viscoelastic region (LVR) was taken as an estimate for the Yield Stress. This method was shown to be sensitive to fat content, emulsifier concentration and type of emulsifier. Furthermore, oscillatory rheology was found to be capable to capture differences in Yield Stress of chocolates that were not differentiated using the Casson model fitting approach. © 2011 Elsevier Ltd.
