In the context of liquids and soft matter, rheology aims to relate stresses with rate of change of strain or strain rates in a continuum-mechanics setting.
Questions tagged [rheology]
20 questions
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Objective time derivative that is not a Lie derivative
Summary
Led by an interest into the concept of "Material Objectivity", I am asking myself:
Are there objective time rates that are not Lie derivatives?
The long read
I am trying to understand the notion of "Material Objectivity" and "Objective Time…
Sanya
- 2,467
3
votes
2 answers
Viscoelastic Kelvin-Voigt model and inelastic strain
In a viscoelastic medium, the total strain can be assumed as the sum of elastic strain and inelastic strain (ref1,2):
\begin{align} \label{eq1}
(1): \mathcal{E}^t_{ij}= \mathcal{E}^e_{ij}+\mathcal{E}^i_{ij}
\end{align}
The inelastic strain is a…
Saint Paul
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Why is shear stress equal to half of yield stress?
Why is the value for acceptable shear stress equals to half of yield stress? $$ \tau = \frac{\sigma_{yield}}{2} $$
P.s Along the math behind it would be possible to explain this with visual consepts?
Jek Denys
- 69
2
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2 answers
Viscous fluid equivalent of hyperelasticity
A hyperelastic solid is defined as one for which the stress tensor $\sigma$ can be written as the derivative of some stored energy function $W$ w.r.t. the strain $\varepsilon$:
$\sigma = \frac{\partial W}{\partial\varepsilon}.$
Hyperelastic solids…
Daniel Shapero
- 211
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physical significance of the 'time of relaxation ' and 'time of observation'
Deborah number (used frequently in rheology) is defined as the ratio of the time of observation to the time of relaxation. In his article The Deborah Number, M. Reiner the man who coined the term has mentioned that if the time of observation is high…
Thomson1
- 35
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Reference request: an introduction to objective rates and constitutive equations
As a hobby, I am trying to better understand the theory around objective rates, frame invariance and objective constitutive equations in non-Newtonian fluid mechanics. Unfortunately, I have been unable to find a reference at the level I'm interested…
1
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0 answers
Can you use formula for viscosity derived from Stokes' law to calculate viscosity of non-Newtonian fluid if constant force is applied?
I would like to drop a ball into a test tube containing mixed corn starch and water ( in different ratios) and use Stokes law to get the viscosity for the fixed weight of the ball that I used. Would this be a correct method? Thanks.
Pls Help
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Time derivative term in Navier Stokes equation for fluid in porous media
I was reading the research paper Homogenization of peristaltic flows in piezoelectric porous media and came across the hydrodynamic equation:
$$\mu \nabla^2 v^f -\underline{ \rho_f (\dot{v}^f + w \cdot \nabla) v^f)} = \nabla p -f $$
where $\mu$ is…
user134613
- 108
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vote
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Sense for a viscoelastic term of Maxwell type
I go reference the book of Jan Prüss (Evolutionary Integral Equations and Applications, 2012) as needed. In this book (pg. 128) it is explored some concepts of stress and strain considering the behaviour of a homogeneous isotropic linear material in…
1
vote
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How do I quantify an adhesive's ability to stick in contrast to flow?
Let's say you glue a ball to a shovel.
How do you quantify this adhesive's and ball's ability to stick to the shovel, moving at different speeds, in air and then while the shovel digs into the ground?
This suggests an adhesive could work so "well"…
StackQuest
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Can an electrorheological non-Newtonian fluid be in a definite shape for a short time?
I have seen this Experiment: ELECTRORHEOLOGICAL FLUIDS and balloon Experiment (Stops flow with Static Electricity),
and have seen that simple cornstarch is affected by electrostatic forces.
The mixture of cornstarch and oil is a non-Newtonian…
kryomaxim
- 3,558
1
vote
1 answer
Derivation of the upper convected time derivative
I read on wikipedia theat the upper convected time derivatvie is the rate of change of some tensor property of a small parcelof fluid that is written in the coordinate system rotating and stretching with the fluid. But concretely how do we obtain…
J.A
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Is it possible for viscosity to increase with concentration of a nano material in a polymer solution without any increase in storage or loss moduli?
I am introducing small amounts of nanocellulose (<5%wt) to aqueous gum Arabic solutions (<20%wt.) I found that the viscosity increases with nanocellulose concentration but the storage and loss moduli are relatively unaffected. Is this possible?
Kev
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1 answer
How can you get the isotropic Young's modulus and Poisson's ratio from rheology data?
I wanted to ask on how to get the Young's modulus and Poisson's ratio for a viscoelastic biomaterial. I have rheological data from the characterization of the biomaterial, the G' and G'' (storage and loss moduli). I also have strain sweep and…
Tenna
- 1
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Maxwell model subject to reversing constant strain rate
I've been reading about viscoelastic models and using Excel to plot some of their characteristics. I'm particularly interested in their response to a constant strain rate which reverses periodically and goes into tension as well as compression.
I've…
