The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Gareth H Mckinley - One of the best experts on this subject based on the ideXlab platform.
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Nonlinear Viscoelasticity and generalized failure criterion for polymer gels
Bulletin of the American Physical Society, 2017Co-Authors: Bavand Keshavarz, Thibaut Divoux, Sebastien Manneville, Gareth H MckinleyAbstract:Polymer gels behave as soft viscoelastic solids and exhibit a generic Nonlinear mechanical response characterized by pronounced stiffening prior to irreversible failure, most often through macroscopic fractures. Here, we describe this scenario for a model protein gel using an integral constitutive equation built upon the linear and the Nonlinear viscoelastic properties of the gel. We show that this formalism predicts quantitatively the gel mechanical response in shear start-up experiments, up to the onset of macroscopic failure. Moreover, we couple the computed stress response with Bailey’s durability criterion for brittle solids in order to predict the critical values of the stress σc and strain γc at failure. The excellent agreement between theory and experiments suggests that failure in this soft viscoelastic gel is a Markovian process and that Bailey’s failure criterion extends beyond hard materials such as metals, glasses, or minerals.
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Nonlinear Viscoelasticity and generalized failure criterion for polymer gels
arXiv: Soft Condensed Matter, 2016Co-Authors: Bavand Keshavarz, Thibaut Divoux, Sebastien Manneville, Gareth H MckinleyAbstract:Polymer gels behave as soft viscoelastic solids and exhibit a generic Nonlinear mechanical response characterized by pronounced stiffening prior to irreversible failure, most often through macroscopic fractures. Here, we aim at capturing the latter scenario for a protein gel using a Nonlinear integral constitutive equation built upon ($i$) the linear viscoelastic response of the gel, here well described by a power-law relaxation modulus, and ($ii$) the Nonlinear viscoelastic properties of the gel, encoded into a "damping function". Such formalism predicts quantitatively the gel mechanical response to a shear start-up experiment, up to the onset of macroscopic failure. Moreover, as the gel failure involves the irreversible growth of macroscopic cracks, we couple the latter stress response with Bailey's durability criterion for brittle solids in order to predict the critical values of the stress $\sigma_c$ and strain $\gamma_c$ at the failure point, and how they scale with the applied shear rate. The excellent agreement between theory and experiments suggests that the crack growth in this soft viscoelastic gel is a Markovian process, and that Baileys' criterion extends well beyond hard materials such as metals, glasses, or minerals.
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new measures for characterizing Nonlinear Viscoelasticity in large amplitude oscillatory shear
Journal of Rheology, 2008Co-Authors: Randy H Ewoldt, A E Hosoi, Gareth H MckinleyAbstract:Characterizing purely viscous or purely elastic rheological Nonlinearities is straightforward using rheometric tests such as steady shear or step strains. However, a definitive framework does not exist to characterize materials which exhibit both viscous and elastic Nonlinearities simultaneously. We define a robust and physically meaningful scheme to quantify such behavior, using an imposed large amplitude oscillatory shear (LAOS) strain. Our new framework includes new material measures and clearly defined terminology such as intra-/intercycle Nonlinearities, strain-stiffening/softening, and shear-thinning/thickening. The method naturally lends a physical interpretation to the higher Fourier coefficients that are commonly reported to describe the Nonlinear stress response. These Nonlinear viscoelastic properties can be used to provide a “rheological fingerprint” in a Pipkin diagram that characterizes the material response as a function of both imposed frequency and strain amplitude. We illustrate our new ...
Pramod A. Pullarkat - One of the best experts on this subject based on the ideXlab platform.
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a master relation defines the Nonlinear Viscoelasticity of single fibroblasts
Biophysical Journal, 2006Co-Authors: Pablo Fernandez, Pramod A. PullarkatAbstract:Cell mechanical functions such as locomotion, contraction, and division are controlled by the cytoskeleton, a dynamic biopolymer network whose mechanical properties remain poorly understood. We perform single-cell uniaxial stretching experiments on 3T3 fibroblasts. By superimposing small amplitude oscillations on a mechanically prestressed cell, we find a transition from linear viscoelastic behavior to power law stress stiffening. Data from different cells over several stress decades can be uniquely scaled to obtain a master relation between the viscoelastic moduli and the average force. Remarkably, this relation holds independently of deformation history, adhesion biochemistry, and intensity of active contraction. In particular, it is irrelevant whether force is actively generated by the cell or externally imposed by stretching. We propose that the master relation reflects the mechanical behavior of the force-bearing actin cytoskeleton, in agreement with stress stiffening known from semiflexible filament networks.
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A master relation defines the Nonlinear Viscoelasticity of single fibroblasts
Biophysical Journal, 2006Co-Authors: Pablo Fernandez, Pramod A. Pullarkat, Albrecht OttAbstract:Cell mechanical functions such as locomotion, contraction, and division are controlled by the cytoskeleton, a dynamic biopolymer network whose mechanical properties remain poorly understood. We perform single-cell uniaxial stretching experiments on 3T3 fibroblasts. By superimposing small amplitude oscillations on a mechanically prestressed cell, we find a transition from linear viscoelastic behavior to power law stress stiffening. Data from different cells over several stress decades can be uniquely scaled to obtain a master relation between the viscoelastic moduli and the average force. Remarkably, this relation holds independently of deformation history, adhesion biochemistry, and intensity of active contraction. In particular, it is irrelevant whether force is actively generated by the cell or externally imposed by stretching. We propose that the master relation reflects the mechanical behavior of the force-bearing actin cytoskeleton, in agreement with stress stiffening known from semiflexible filament networks. © 2006 by the Biophysical Society.
Pablo Fernandez - One of the best experts on this subject based on the ideXlab platform.
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a master relation defines the Nonlinear Viscoelasticity of single fibroblasts
Biophysical Journal, 2006Co-Authors: Pablo Fernandez, Pramod A. PullarkatAbstract:Cell mechanical functions such as locomotion, contraction, and division are controlled by the cytoskeleton, a dynamic biopolymer network whose mechanical properties remain poorly understood. We perform single-cell uniaxial stretching experiments on 3T3 fibroblasts. By superimposing small amplitude oscillations on a mechanically prestressed cell, we find a transition from linear viscoelastic behavior to power law stress stiffening. Data from different cells over several stress decades can be uniquely scaled to obtain a master relation between the viscoelastic moduli and the average force. Remarkably, this relation holds independently of deformation history, adhesion biochemistry, and intensity of active contraction. In particular, it is irrelevant whether force is actively generated by the cell or externally imposed by stretching. We propose that the master relation reflects the mechanical behavior of the force-bearing actin cytoskeleton, in agreement with stress stiffening known from semiflexible filament networks.
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A master relation defines the Nonlinear Viscoelasticity of single fibroblasts
Biophysical Journal, 2006Co-Authors: Pablo Fernandez, Pramod A. Pullarkat, Albrecht OttAbstract:Cell mechanical functions such as locomotion, contraction, and division are controlled by the cytoskeleton, a dynamic biopolymer network whose mechanical properties remain poorly understood. We perform single-cell uniaxial stretching experiments on 3T3 fibroblasts. By superimposing small amplitude oscillations on a mechanically prestressed cell, we find a transition from linear viscoelastic behavior to power law stress stiffening. Data from different cells over several stress decades can be uniquely scaled to obtain a master relation between the viscoelastic moduli and the average force. Remarkably, this relation holds independently of deformation history, adhesion biochemistry, and intensity of active contraction. In particular, it is irrelevant whether force is actively generated by the cell or externally imposed by stretching. We propose that the master relation reflects the mechanical behavior of the force-bearing actin cytoskeleton, in agreement with stress stiffening known from semiflexible filament networks. © 2006 by the Biophysical Society.
Bavand Keshavarz - One of the best experts on this subject based on the ideXlab platform.
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Nonlinear Viscoelasticity and generalized failure criterion for polymer gels
Bulletin of the American Physical Society, 2017Co-Authors: Bavand Keshavarz, Thibaut Divoux, Sebastien Manneville, Gareth H MckinleyAbstract:Polymer gels behave as soft viscoelastic solids and exhibit a generic Nonlinear mechanical response characterized by pronounced stiffening prior to irreversible failure, most often through macroscopic fractures. Here, we describe this scenario for a model protein gel using an integral constitutive equation built upon the linear and the Nonlinear viscoelastic properties of the gel. We show that this formalism predicts quantitatively the gel mechanical response in shear start-up experiments, up to the onset of macroscopic failure. Moreover, we couple the computed stress response with Bailey’s durability criterion for brittle solids in order to predict the critical values of the stress σc and strain γc at failure. The excellent agreement between theory and experiments suggests that failure in this soft viscoelastic gel is a Markovian process and that Bailey’s failure criterion extends beyond hard materials such as metals, glasses, or minerals.
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Nonlinear Viscoelasticity and generalized failure criterion for polymer gels
arXiv: Soft Condensed Matter, 2016Co-Authors: Bavand Keshavarz, Thibaut Divoux, Sebastien Manneville, Gareth H MckinleyAbstract:Polymer gels behave as soft viscoelastic solids and exhibit a generic Nonlinear mechanical response characterized by pronounced stiffening prior to irreversible failure, most often through macroscopic fractures. Here, we aim at capturing the latter scenario for a protein gel using a Nonlinear integral constitutive equation built upon ($i$) the linear viscoelastic response of the gel, here well described by a power-law relaxation modulus, and ($ii$) the Nonlinear viscoelastic properties of the gel, encoded into a "damping function". Such formalism predicts quantitatively the gel mechanical response to a shear start-up experiment, up to the onset of macroscopic failure. Moreover, as the gel failure involves the irreversible growth of macroscopic cracks, we couple the latter stress response with Bailey's durability criterion for brittle solids in order to predict the critical values of the stress $\sigma_c$ and strain $\gamma_c$ at the failure point, and how they scale with the applied shear rate. The excellent agreement between theory and experiments suggests that the crack growth in this soft viscoelastic gel is a Markovian process, and that Baileys' criterion extends well beyond hard materials such as metals, glasses, or minerals.
John M Dealy - One of the best experts on this subject based on the ideXlab platform.
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Nonlinear Viscoelasticity: Phenomena
Melt Rheology and its Applications in the Plastics Industry, 2013Co-Authors: John M Dealy, Jian WangAbstract:While linear viscoelastic properties are very helpful in establishing the molecular structure of polymers, the deformations that occur in processing machinery are always large and rapid, and under these conditions melt behavior is decidedly Nonlinear. One manifestation of this is that the response to a shearing deformation no longer provides a complete description of rheological behavior. The molecular processes that give rise to Nonlinear Viscoelasticity are described as well as several large and rapid deformations that used to obtain information about Nonlinear behavior. These include large-amplitude oscillatory shear and extensional flow.
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Nonlinear Viscoelasticity of pp ps sebs blends
Rheologica Acta, 2005Co-Authors: Paulo Henrique Pierin Macaubas, Nicole Raymond Demarquette, John M DealyAbstract:The Nonlinear viscoelastic behavior of polypropylene/polystyrene (PP/PS) blends compatibilized or not with the linear triblock copolymer (styrene-ethylene-/butylene-styrene, SEBS) was investigated. Start-up of steady-shear at rates from 0.1 to 10 s−1 was carried out using a controlled strain rotational rheometer and a sliding plate rheometer for strain histories involving one or several shear rates. The shear stress and first normal shear stress difference were measured as functions of time, and the morphologies of the samples before and after shearing were determined. For each strain history except that involving a single shear rate of 0.1 s−1 the blends showed typical non-linear viscoelastic behavior: a shear stress overshoot/undershoot, depending on the history, followed by a steady state for each step. The first normal stress difference increased monotonically to a steady-state value. The values of the stresses increased with the addition of SEBS. The shear stress overshoot and undershoot and the times at which they occurred depended strongly on the strain history, decreasing for a subsequent shear rate step performed in the same direction as the former, and the time at which stress undershoot occurred increased for a subsequent shear rate step performed in the opposite direction, irrespective of the magnitude of the shear rate. This behavior was observed for all the blends studied. The time of overshoot in a single-step shear rate experiment is inversely proportional to the shear rate, and the steady-state value of N1 scaled linearly with shear rate, whereas the steady-state shear stress did not. The average diameter of the dispersed phase decreased for all strain histories when the blend was not compatibilized. When the blend was compatibilized, the average diameter of the dispersed phase changed only during the stronger flows. Experimental data were compared with the predictions of a model formulated using ideas of Doi and Ohta (1991), Lacroix et al. (1998) and Bousmina et al. (2001). The model correctly predicted the behavior of the uncompatibilized blends for single-step shear rates but not that of the compatibilized blends, nor did it predict morphologies after shearing.
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Nonlinear Viscoelasticity of concentrated polystyrene solutions sliding plate rheometer studies
Journal of Rheology, 1992Co-Authors: Nicole Raymond Demarquette, John M DealyAbstract:Because of the degree to which the linearity and polydispersity of polystyrene samples can be controlled in laboratory polymerizations, the rheological properties of melts and solutions of this polymer have been extensively studied. However, in previous work the maximum strain or strain rate was limited to small values due to edge effects in the rotational rheometers used. We used a sliding plate rheometer equipped with a shear stress transducer and a birefringence apparatus to measure simultaneously the shear stress and the third normal stress difference, N3 (≡σ11−σ33), during step strain, start‐up of steady shear, and exponential shear. Depending on the strain history, the maximum strain achieved was between 20 and 80. The steady‐state shear stress in steady shear flow was found to be nearly independent of shear rate over a range of shear rates with a strong suggestion of a maximum, a phenomenon predicted by the Doi–Edwards theory. The relaxation modulus for the shear stress was found to be superposable...
