Numerical interconversion of linear viscoelastic functions is an important problem in rheology. This work focuses on interconversion between creep compliance (J) and relaxation modulus (G) via the convolution relation. A discrete spectrum or Prony series is used to describe both the source (G or J) and the target (J or G) of the interconversion. A previously developed numerical template [Loy et al.,J. Rheol.59(5), 1261 (2015)] is modified to bypass singularities. It is released as an open-source computer program called PSI (Prony series interconversion). PSI is tested on a variety of materials including viscoelastic solids and liquids and used for both G→J and J→G interconversions. It is fast and numerically stable for input data that span over 20 decades in time. It fills a gap in the existing software landscape for conversion of linear viscoelastic functions.
{"title":"A computer program for interconversion between creep compliance and stress relaxation","authors":"S. Shanbhag","doi":"10.1122/8.0000695","DOIUrl":"https://doi.org/10.1122/8.0000695","url":null,"abstract":"Numerical interconversion of linear viscoelastic functions is an important problem in rheology. This work focuses on interconversion between creep compliance (J) and relaxation modulus (G) via the convolution relation. A discrete spectrum or Prony series is used to describe both the source (G or J) and the target (J or G) of the interconversion. A previously developed numerical template [Loy et al.,J. Rheol.59(5), 1261 (2015)] is modified to bypass singularities. It is released as an open-source computer program called PSI (Prony series interconversion). PSI is tested on a variety of materials including viscoelastic solids and liquids and used for both G→J and J→G interconversions. It is fast and numerically stable for input data that span over 20 decades in time. It fills a gap in the existing software landscape for conversion of linear viscoelastic functions.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48091555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Edge fracture is a viscoelastic instability characterized by the sudden indentation of a fluid’s free surface when the fluid is subjected to a high enough shear rate. During shear rheometry, the fracture can invade the fluid sample, decreasing its contact area with the rheometer fixture and rendering the measurement of viscosity and normal stresses at high-shear rates invalid. Edge fracture can also induce apparent shear banding in the fluid, complicating the interpretation of experimental results. Over the past several decades, empirical and theoretical research has unraveled the physics underlying edge fracture. The knowledge obtained has allowed rheologists to develop techniques to minimize the adverse effect of fracture in their experiments. In recent years, edge fracture has also been used to break up viscoelastic liquid bridges quickly and cleanly, showing its potential to be adapted to the design of functional dispensing nozzles. This Perspective article aims to give a historical overview of edge fracture and suggests research directions to develop methods for suppressing or harnessing the phenomenon to benefit applications of both fundamental and technological importance.
{"title":"Perspective on edge fracture","authors":"S. T. Chan, S. Varchanis, S. Haward, A. Shen","doi":"10.1122/8.0000625","DOIUrl":"https://doi.org/10.1122/8.0000625","url":null,"abstract":"Edge fracture is a viscoelastic instability characterized by the sudden indentation of a fluid’s free surface when the fluid is subjected to a high enough shear rate. During shear rheometry, the fracture can invade the fluid sample, decreasing its contact area with the rheometer fixture and rendering the measurement of viscosity and normal stresses at high-shear rates invalid. Edge fracture can also induce apparent shear banding in the fluid, complicating the interpretation of experimental results. Over the past several decades, empirical and theoretical research has unraveled the physics underlying edge fracture. The knowledge obtained has allowed rheologists to develop techniques to minimize the adverse effect of fracture in their experiments. In recent years, edge fracture has also been used to break up viscoelastic liquid bridges quickly and cleanly, showing its potential to be adapted to the design of functional dispensing nozzles. This Perspective article aims to give a historical overview of edge fracture and suggests research directions to develop methods for suppressing or harnessing the phenomenon to benefit applications of both fundamental and technological importance.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48770929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Harumi Yagi, Y. Nagatsu, Masayoshi Takano, Ryuta X. Suzuki
In this study, the interfacial flow dynamics involving a chemical reaction that produces viscoelastic material at the interface between two liquids is experimentally investigated, and the material is evaluated using interfacial large amplitude oscillatory shear (LAOS) measurements. The flow dynamics indicates fingering patterns at low injection flow rates and fracturing patterns at high flow rates in Hele-Shaw cells, where a more viscous xanthan gum solution is displaced by the less viscous Fe(NO3)3 solution with various concentrations of Fe(NO3)3. The threshold flow rate value of such a transition is different for various concentrations of Fe(NO3)3. Although such a transition without chemical reactions has been discussed, the factors responsible for the transition remain unclear. The flow dynamics in Hele-Shaw cells is considered to flow under large deformation, which exceeds the small amplitude oscillatory shear condition but is under the LAOS condition. Therefore, LAOS measurement of the viscoelastic interface is performed for various concentrations of Fe(NO3)3. Using the characteristic properties extracted from the LAOS measurements, the elastic and viscous forces of the viscoelastic interface are evaluated. We show the transition from fingering to fracturing patterns when the elastic force exceeds a certain value. These findings highlight that rheology under large deformation of the viscoelastic interface plays a crucial role in interfacial flow, where viscoelastic materials are produced by chemical reactions at the interface. In addition, this study should be an example of the successful elucidation of physical phenomena by interfacial LAOS, which has been reported in a very limited number of studies.
{"title":"Understanding the reactive interfacial flow dynamics with production of viscoelastic material through large amplitude oscillatory shear (LAOS) measurements of the viscoelastic interface","authors":"Harumi Yagi, Y. Nagatsu, Masayoshi Takano, Ryuta X. Suzuki","doi":"10.1122/8.0000650","DOIUrl":"https://doi.org/10.1122/8.0000650","url":null,"abstract":"In this study, the interfacial flow dynamics involving a chemical reaction that produces viscoelastic material at the interface between two liquids is experimentally investigated, and the material is evaluated using interfacial large amplitude oscillatory shear (LAOS) measurements. The flow dynamics indicates fingering patterns at low injection flow rates and fracturing patterns at high flow rates in Hele-Shaw cells, where a more viscous xanthan gum solution is displaced by the less viscous Fe(NO3)3 solution with various concentrations of Fe(NO3)3. The threshold flow rate value of such a transition is different for various concentrations of Fe(NO3)3. Although such a transition without chemical reactions has been discussed, the factors responsible for the transition remain unclear. The flow dynamics in Hele-Shaw cells is considered to flow under large deformation, which exceeds the small amplitude oscillatory shear condition but is under the LAOS condition. Therefore, LAOS measurement of the viscoelastic interface is performed for various concentrations of Fe(NO3)3. Using the characteristic properties extracted from the LAOS measurements, the elastic and viscous forces of the viscoelastic interface are evaluated. We show the transition from fingering to fracturing patterns when the elastic force exceeds a certain value. These findings highlight that rheology under large deformation of the viscoelastic interface plays a crucial role in interfacial flow, where viscoelastic materials are produced by chemical reactions at the interface. In addition, this study should be an example of the successful elucidation of physical phenomena by interfacial LAOS, which has been reported in a very limited number of studies.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43189442","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Surfactants at gas-liquid and liquid-liquid interfaces have profound effects on interfacial stresses that strongly influence flow in bulk phases in contact with the interface. These effects include changes in interfacial tension and the development of extra stresses that arise when the interface is deformed. Surfactants are important in nature, biological function, and numerous technologies. Understanding interfacial rheology is critical to the development of improved surfactants for these important applications. Here, we propose a novel and noninvasive technique for the investigation of interfacial rheological behavior in shear deformations. In recent years, several techniques for such measurements have been developed and utilized to study a wide range of surfactant systems. However, existing techniques may inherently be invasive making it difficult to isolate the intrinsic interfacial rheological behavior from disturbances to the interface caused by the measurement itself. The proposed technique is indirect in that it does not require the introduction of a probe to deform the interface making it noninvasive. The viability of the technique is demonstrated through comprehensive fluid dynamics modeling of the flow involving a gas-liquid interface with different rheological behaviors.
{"title":"A novel and noninvasive approach to study the shear rheology of complex fluid interfaces","authors":"D. Venerus","doi":"10.1122/8.0000649","DOIUrl":"https://doi.org/10.1122/8.0000649","url":null,"abstract":"Surfactants at gas-liquid and liquid-liquid interfaces have profound effects on interfacial stresses that strongly influence flow in bulk phases in contact with the interface. These effects include changes in interfacial tension and the development of extra stresses that arise when the interface is deformed. Surfactants are important in nature, biological function, and numerous technologies. Understanding interfacial rheology is critical to the development of improved surfactants for these important applications. Here, we propose a novel and noninvasive technique for the investigation of interfacial rheological behavior in shear deformations. In recent years, several techniques for such measurements have been developed and utilized to study a wide range of surfactant systems. However, existing techniques may inherently be invasive making it difficult to isolate the intrinsic interfacial rheological behavior from disturbances to the interface caused by the measurement itself. The proposed technique is indirect in that it does not require the introduction of a probe to deform the interface making it noninvasive. The viability of the technique is demonstrated through comprehensive fluid dynamics modeling of the flow involving a gas-liquid interface with different rheological behaviors.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49572827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Multi-phase flows, encountered in nature or in industry, exhibit non-trivial rheological properties, which we attempt to better understand thanks to model materials and appropriate rheometers. Unsaturated wet granular flows down a rough inclined plane turn out to be steady and uniform for a wide range of parameters, despite the cohesion and the grain aggregates. The cohesive Mohr–Coulomb yield criterion extended to inertial granular flows, with a cohesion stress dependent on the liquid content and an internal friction coefficient dependent on the inertial number, allows for predictions in good agreement with our experimental measurements, when one introduces a grain aggregate size, which defines the appropriate length and relaxation time scales in the inertial number. We found that the grain aggregate size depends not monotonically on the liquid content and does not scale with the cohesion length induced by the cohesion stress, due to the non-trivial distribution of the liquid within the granular material.
{"title":"Cohesion and aggregates in unsaturated wet granular flows down a rough incline","authors":"S. Deboeuf, A. Fall","doi":"10.1122/8.0000631","DOIUrl":"https://doi.org/10.1122/8.0000631","url":null,"abstract":"Multi-phase flows, encountered in nature or in industry, exhibit non-trivial rheological properties, which we attempt to better understand thanks to model materials and appropriate rheometers. Unsaturated wet granular flows down a rough inclined plane turn out to be steady and uniform for a wide range of parameters, despite the cohesion and the grain aggregates. The cohesive Mohr–Coulomb yield criterion extended to inertial granular flows, with a cohesion stress dependent on the liquid content and an internal friction coefficient dependent on the inertial number, allows for predictions in good agreement with our experimental measurements, when one introduces a grain aggregate size, which defines the appropriate length and relaxation time scales in the inertial number. We found that the grain aggregate size depends not monotonically on the liquid content and does not scale with the cohesion length induced by the cohesion stress, due to the non-trivial distribution of the liquid within the granular material.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45472537","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Esteban F. Medina-Bañuelos, B. M. Marín-Santibáñez, E. Chaparian, C. Owens, G. McKinley, J. Pérez-González
The vane-in-cup (VIC) geometry has been widely used for the rheological characterization of yield-stress fluids because it minimizes slip effects at the liquid/solid interface of the rotating geometry and reduces sample damage during the loading process. However, severe kinematic limitations arising from the spatial complexity of mixed shear and extensional flow have been identified for quantitative rheometrical measurements in complex fluids. Recently, vanes with fractal cross sections have been suggested as alternatives for accurate rheometry of elastoviscoplastic fluids. In this work, the steady fractal vane-in-cup (fVIC) flow of a Newtonian fluid and a nonthixotropic Carbopol® 940 microgel as well as the unsteady flow of a thixotropic κ-Carrageenan gel are analyzed using rheo-particle image velocimetry (Rheo-PIV). We describe the velocity distributions in all cases and show that the fVIC produces an almost axisymmetric flow field and rotation rate-independent “effective radius” when used with both the Newtonian fluid and the microgel. These findings are supported by 2D simulation results and enable the safe use of both the Couette analogy and the torque-to-stress conversion scheme for a 24-arm fVIC as well as validate it as a reliable rheometrical tool for characterization of a variety of complex fluids. With the κ-Carrageenan gel, however, axial shearing/compression while inserting the rheometric tool into the sample also accelerates syneresis that ultimately results in shear banding for Couette and fVIC flows. By comparing results obtained using the 24-arm fVIC with other conventional geometries, we investigate the effect that the lateral and cross-sectional (shearing/compressing) area of the measuring fixture have on disrupting the κ-Carrageenan gel during its insertion.
{"title":"Rheo-PIV of yield-stress fluids in a 3D-printed fractal vane-in-cup geometry","authors":"Esteban F. Medina-Bañuelos, B. M. Marín-Santibáñez, E. Chaparian, C. Owens, G. McKinley, J. Pérez-González","doi":"10.1122/8.0000639","DOIUrl":"https://doi.org/10.1122/8.0000639","url":null,"abstract":"The vane-in-cup (VIC) geometry has been widely used for the rheological characterization of yield-stress fluids because it minimizes slip effects at the liquid/solid interface of the rotating geometry and reduces sample damage during the loading process. However, severe kinematic limitations arising from the spatial complexity of mixed shear and extensional flow have been identified for quantitative rheometrical measurements in complex fluids. Recently, vanes with fractal cross sections have been suggested as alternatives for accurate rheometry of elastoviscoplastic fluids. In this work, the steady fractal vane-in-cup (fVIC) flow of a Newtonian fluid and a nonthixotropic Carbopol® 940 microgel as well as the unsteady flow of a thixotropic κ-Carrageenan gel are analyzed using rheo-particle image velocimetry (Rheo-PIV). We describe the velocity distributions in all cases and show that the fVIC produces an almost axisymmetric flow field and rotation rate-independent “effective radius” when used with both the Newtonian fluid and the microgel. These findings are supported by 2D simulation results and enable the safe use of both the Couette analogy and the torque-to-stress conversion scheme for a 24-arm fVIC as well as validate it as a reliable rheometrical tool for characterization of a variety of complex fluids. With the κ-Carrageenan gel, however, axial shearing/compression while inserting the rheometric tool into the sample also accelerates syneresis that ultimately results in shear banding for Couette and fVIC flows. By comparing results obtained using the 24-arm fVIC with other conventional geometries, we investigate the effect that the lateral and cross-sectional (shearing/compressing) area of the measuring fixture have on disrupting the κ-Carrageenan gel during its insertion.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45025603","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Michael Q. Tu, Hung V. Nguyen, Elliel Foley, M. I. Jacobs, Charles M. Schroeder
Flow-based manipulation of particles is an essential tool for studying soft materials, but prior work has nearly exclusively relied on using two-dimensional (2D) flows generated in planar microfluidic geometries. In this work, we demonstrate 3D trapping and manipulation of freely suspended particles, droplets, and giant unilamellar vesicles in 3D flow fields using automated flow control. Three-dimensional flow fields including uniaxial extension and biaxial extension are generated in 3D-printed fluidic devices combined with active feedback control for particle manipulation in 3D. Flow fields are characterized using particle tracking velocimetry complemented by finite-element simulations for all flow geometries. Single colloidal particles (3.4 μm diameter) are confined in low viscosity solvent (1.0 mPa s) near the stagnation points of uniaxial and biaxial extensional flow for long times (≥10 min) using active feedback control. Trap stiffness is experimentally determined by analyzing the power spectral density of particle position fluctuations. We further demonstrate precise manipulation of colloidal particles along user-defined trajectories in three dimensions using automated flow control. Newtonian liquid droplets and GUVs are trapped and deformed in precisely controlled uniaxial and biaxial extensional flows, which is a new demonstration for 3D flow fields. Overall, this work extends flow-based manipulation of particles and droplets to three dimensions, thereby enabling quantitative analysis of colloids and soft materials in complex nonequilibrium flows.
{"title":"3D manipulation and dynamics of soft materials in 3D flows","authors":"Michael Q. Tu, Hung V. Nguyen, Elliel Foley, M. I. Jacobs, Charles M. Schroeder","doi":"10.1122/8.0000600","DOIUrl":"https://doi.org/10.1122/8.0000600","url":null,"abstract":"Flow-based manipulation of particles is an essential tool for studying soft materials, but prior work has nearly exclusively relied on using two-dimensional (2D) flows generated in planar microfluidic geometries. In this work, we demonstrate 3D trapping and manipulation of freely suspended particles, droplets, and giant unilamellar vesicles in 3D flow fields using automated flow control. Three-dimensional flow fields including uniaxial extension and biaxial extension are generated in 3D-printed fluidic devices combined with active feedback control for particle manipulation in 3D. Flow fields are characterized using particle tracking velocimetry complemented by finite-element simulations for all flow geometries. Single colloidal particles (3.4 μm diameter) are confined in low viscosity solvent (1.0 mPa s) near the stagnation points of uniaxial and biaxial extensional flow for long times (≥10 min) using active feedback control. Trap stiffness is experimentally determined by analyzing the power spectral density of particle position fluctuations. We further demonstrate precise manipulation of colloidal particles along user-defined trajectories in three dimensions using automated flow control. Newtonian liquid droplets and GUVs are trapped and deformed in precisely controlled uniaxial and biaxial extensional flows, which is a new demonstration for 3D flow fields. Overall, this work extends flow-based manipulation of particles and droplets to three dimensions, thereby enabling quantitative analysis of colloids and soft materials in complex nonequilibrium flows.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42302055","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The properties of polymer blend nanocomposites are typically associated with spatiotemporal distribution of nanoparticles within a polymer blend system. Here, we present in situ high-temperature confocal rheology studies to assess the effect of particle size on the extent of particle agglomeration, particle migration, and subsequently their influence on the coarsening dynamics of polymer blends filled with pristine silica particles. We investigate co-continuous polypropylene-poly(ethylene-co-vinyl acetate) blends filled with five different silica particles with a diameter ranging from 5 to 490 nm. While particle size does not play a role when particles are thermodynamically driven to their preferred polymer phase, a striking effect is achieved when particles are kinetically trapped at the interface. We find that the interparticle interaction largely driven by size dependent long-range repulsive forces governs their extent of agglomeration, severely affecting their ability to stabilize co-continuous morphology. Strikingly, the largest (490 nm) particles are more effective in suppressing coarsening than 5 nm particles, while 140 and 250 nm particles are found to be the most effective. We demonstrate that kinetic trapping of primary particles of either size is influenced by the interplay of interfacial folding during melt blending and Laplacian pressure exerted at the interface. These results extend our fundamental understanding of the stabilization of co-continuous morphology in polymer blends by particles.
{"title":"Particle-size dependent stability of co-continuous polymer blends","authors":"Rajas Sudhir Shah, S. Bryant, M. Trifkovic","doi":"10.1122/8.0000642","DOIUrl":"https://doi.org/10.1122/8.0000642","url":null,"abstract":"The properties of polymer blend nanocomposites are typically associated with spatiotemporal distribution of nanoparticles within a polymer blend system. Here, we present in situ high-temperature confocal rheology studies to assess the effect of particle size on the extent of particle agglomeration, particle migration, and subsequently their influence on the coarsening dynamics of polymer blends filled with pristine silica particles. We investigate co-continuous polypropylene-poly(ethylene-co-vinyl acetate) blends filled with five different silica particles with a diameter ranging from 5 to 490 nm. While particle size does not play a role when particles are thermodynamically driven to their preferred polymer phase, a striking effect is achieved when particles are kinetically trapped at the interface. We find that the interparticle interaction largely driven by size dependent long-range repulsive forces governs their extent of agglomeration, severely affecting their ability to stabilize co-continuous morphology. Strikingly, the largest (490 nm) particles are more effective in suppressing coarsening than 5 nm particles, while 140 and 250 nm particles are found to be the most effective. We demonstrate that kinetic trapping of primary particles of either size is influenced by the interplay of interfacial folding during melt blending and Laplacian pressure exerted at the interface. These results extend our fundamental understanding of the stabilization of co-continuous morphology in polymer blends by particles.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45022451","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Undoubtedly, cement is one of the most important materials in the construction industry. For its effective use, it is particularly important to fully comprehend the rheological behavior of cement paste. When cement is mixed with water, a suspension is initially formed and the rate of hydrolysis reactions accelerates leading to the formation of a new irreversible structure, i.e., the cement paste gradually solidifies. At the same time, the viscosity of the paste initially decreases with time, while at long times it gradually increases due to the formation of the irreversible structure. We herein introduce a continuum model for predicting the rheological behavior of cement pastes. The model is developed using nonequilibrium thermodynamics, in particular, the Generalized Brackets formalism, to guarantee model admissibility with thermodynamic laws. To this end, we consider two scalar structural variables: a reversible, λrev, characterizing the reversible structure, and an irreversible one, λirr, characterizing the irreversible structure resulting from the hydrolysis reactions. Also, we consider a tensorial structural variable, the conformation tensor c, to characterize the deformation of the cement particles. The predictions of the new model compare reasonably well with available experimental data, especially at large times, and further highlight the capacity of the new model to address the thixotropic behavior of cement pastes. It is expected that the use of this model in concrete rheology simulators will allow for the in silico testing and tailor-designing of concrete to meet specific processing needs.
{"title":"Nonequilibrium thermodynamics modeling of the rheological response of cement pastes","authors":"Amalia K. Ioannou, Pavlos S. Stephanou","doi":"10.1122/8.0000643","DOIUrl":"https://doi.org/10.1122/8.0000643","url":null,"abstract":"Undoubtedly, cement is one of the most important materials in the construction industry. For its effective use, it is particularly important to fully comprehend the rheological behavior of cement paste. When cement is mixed with water, a suspension is initially formed and the rate of hydrolysis reactions accelerates leading to the formation of a new irreversible structure, i.e., the cement paste gradually solidifies. At the same time, the viscosity of the paste initially decreases with time, while at long times it gradually increases due to the formation of the irreversible structure. We herein introduce a continuum model for predicting the rheological behavior of cement pastes. The model is developed using nonequilibrium thermodynamics, in particular, the Generalized Brackets formalism, to guarantee model admissibility with thermodynamic laws. To this end, we consider two scalar structural variables: a reversible, λrev, characterizing the reversible structure, and an irreversible one, λirr, characterizing the irreversible structure resulting from the hydrolysis reactions. Also, we consider a tensorial structural variable, the conformation tensor c, to characterize the deformation of the cement particles. The predictions of the new model compare reasonably well with available experimental data, especially at large times, and further highlight the capacity of the new model to address the thixotropic behavior of cement pastes. It is expected that the use of this model in concrete rheology simulators will allow for the in silico testing and tailor-designing of concrete to meet specific processing needs.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":"1 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41491937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Magnetorheological fluids structured under precession fields are thoroughly investigated. Having complete dynamic triaxial magnetic field control, we are able to study both the structural and magnetorheological response via videomicroscopy and rheometry integration for a wide range of magnetic field configurations, once previously limited to traditional uniaxial fields. Optimal precession fields for driving the formation of more robust particle structures enhancing yield stress response are identified. It is believed that structural reinforcement comes from chain coarsening through lateral chain coalescence and particle compactness within the structures such that a lower energy configuration is found for certain field configurations. Particle level simulations supplement our understanding of lateral chain coalescence and structure strengthening.
{"title":"Magnetorheology in unsteady fields: From uniaxial DC to rotating AC fields","authors":"M. Terkel, Rosalind J Wright, J. D. de Vicente","doi":"10.1122/8.0000646","DOIUrl":"https://doi.org/10.1122/8.0000646","url":null,"abstract":"Magnetorheological fluids structured under precession fields are thoroughly investigated. Having complete dynamic triaxial magnetic field control, we are able to study both the structural and magnetorheological response via videomicroscopy and rheometry integration for a wide range of magnetic field configurations, once previously limited to traditional uniaxial fields. Optimal precession fields for driving the formation of more robust particle structures enhancing yield stress response are identified. It is believed that structural reinforcement comes from chain coarsening through lateral chain coalescence and particle compactness within the structures such that a lower energy configuration is found for certain field configurations. Particle level simulations supplement our understanding of lateral chain coalescence and structure strengthening.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48059593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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