Difference between revisions of "Viscoelasticity"

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| [[Image:MultipleViscoelasticComponents.png |150px|  ]]
| [[Image:MultipleViscoelasticComponents.png |150px|  ]]
| Viscoelastic fluids: Strain rates add. (Maxwell Model)
| Viscoelastic fluids: Strain rates add.
| Viscoelastic solids: Strains add. (Kelvin-Voigt Model)
(Maxwell Model)
| Viscoelastic solids: Strains add.
(Kelvin-Voigt Model)
| And so on, with decreasing physical interpretation.
| And so on, with decreasing physical interpretation.

Revision as of 01:33, 23 September 2008

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Viscoelasticity is the property of materials that exhibit both viscous and elastic characteristics when undergoing deformation. Viscous materials, like honey, resist shear flow and strain linearly with time when a stress is applied. Elastic materials strain instantaneously when stretched and just as quickly return to their original state once the stress is removed. Viscoelastic materials have elements of both of these properties and, as such, exhibit time dependent strain. Whereas elasticity is usually the result of bond stretching along crystallographic planes in an ordered solid, viscoelasticity is the result of the diffusion of atoms or molecules inside of an amorphous material

Spring and Dashpot Models:

ViscoelasticFluid.png ViscoelasticSolid.png MultipleViscoelasticComponents.png
Viscoelastic fluids: Strain rates add.

(Maxwell Model)

Viscoelastic solids: Strains add.

(Kelvin-Voigt Model)

And so on, with decreasing physical interpretation.

The Maxwell model

Maxwell mode: Add the strain rates: MaxwellModel01.png
For the elastic component: MaxwellModel02.png
For the viscous component: MaxwellModel03.png
The resulting differential equation is: MaxwellModel04.png

Viscoelasticity - Creep test

For a creep test: A stress is applied instantaneously and maintained. The strain is measured as a function of time"

Creep Test.png

Creep Test Eqn.png

Viscoelasticity - Stress relaxation

For a stress relaxation, a rapid strain is applied and held. The problem is to determine the stress as a function of time:

StressRelaxation.png StressRelaxation Eqn.png

Viscoelasticity - Molecular relaxations

Motion of Complex FLuids.png

Experimental methods

  • Viscoelasticity
  • Osmotic pressure
  • Force microscopy: scanning, tunneling, atomic
  • Dynamic scattering over time scales
  • Static scattering – x-rays, neutrons, back-scattering
  • NMR

Canonical ideas

  • Typical energies are kT
  • Fluctuations and Brownian motion
  • Wide length scales – use coarse grain models
  • Hierarchical structures
  • Physics dominates over chemistry (so far)


  • De Gennes, P.-G.; Badoz, J. Fragile objects. Springer-Verlag: New York; 1996.
  • Einstein, A. Investigations on the theory of the Brownian motion. Dover Publications: New York; 1956.
  • Elimelech, M.; Gregory, J.; Jia, X.; Williams, R.A. Particle deposition & aggregation; Butterworth-Heinemann: Woburn, MA; 1995.
  • Hamley, I.W. Introduction to soft matter. Revised ed.; John Wiley & Sons: New York; 2007.
  • Israelachvili, J. Intermolecular and surface forces, 2nd ed.; Academic Press: New York; 1991.
  • Witten, T.; Pincus, P. Structured fluids: polymers, colloids, surfactants. Oxford University Press: New York; 2004.

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