Difference between revisions of "Viscoelastic"

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(Newtonian Liquid)
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A Hookean solid is one that displays perfectly elastic behavior. This corresponds to the fact that an applied shear stress produces a shear strain in response. Recall that the shear stress (<math>\sigma</math>) is given by the applied force over the area, namely <math>\sigma = F/A</math>, and the shear strain (<math>e</math>) is given by <math>e = \Delta x/y</math>. See Figure 1 for clarification.
 
A Hookean solid is one that displays perfectly elastic behavior. This corresponds to the fact that an applied shear stress produces a shear strain in response. Recall that the shear stress (<math>\sigma</math>) is given by the applied force over the area, namely <math>\sigma = F/A</math>, and the shear strain (<math>e</math>) is given by <math>e = \Delta x/y</math>. See Figure 1 for clarification.
  
[[Image:Cube.png|thumb|Figure 1]]
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[[Image:Cube.png|thumb|Figure 1, taken from reference [1]]]
  
 
For a Hookean solid, we simply have the shear stress proportional to the applied stress by a proportionality constant called the shear modulus (<math>G</math>), <math>\sigma = Ge</math>.
 
For a Hookean solid, we simply have the shear stress proportional to the applied stress by a proportionality constant called the shear modulus (<math>G</math>), <math>\sigma = Ge</math>.
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==Example==
 
==Example==
Since viscoelastic behavior comes in various forms,  
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Since viscoelastic behavior comes in various forms, it is instructive to look at a simple example.
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In Figure 2,
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[[Image:Example.png|thumb|Figure 2, taken from reference [1]]]
  
  
 
==References==
 
==References==

Revision as of 17:26, 12 September 2009

Definition

A substance that displays behavior that is both viscous and elastic is said to be viscoelastic. In this sense, viscoelastic materials are said to be a combination of the ideal (elastic) Hookean solid and the (viscous) Newtonian liquid, along with a time a dependence.

Hookean Solid

A Hookean solid is one that displays perfectly elastic behavior. This corresponds to the fact that an applied shear stress produces a shear strain in response. Recall that the shear stress (<math>\sigma</math>) is given by the applied force over the area, namely <math>\sigma = F/A</math>, and the shear strain (<math>e</math>) is given by <math>e = \Delta x/y</math>. See Figure 1 for clarification.

Figure 1, taken from reference [1]

For a Hookean solid, we simply have the shear stress proportional to the applied stress by a proportionality constant called the shear modulus (<math>G</math>), <math>\sigma = Ge</math>.

Newtonian Liquid

In the case of a Newtonian liquid, the shear stress is proportional to the first time derivative of the shear strain by a constant called the viscosity (<math>\eta</math>), <math>\sigma = \eta \dot{e}</math>.

Example

Since viscoelastic behavior comes in various forms, it is instructive to look at a simple example.

In Figure 2,

Figure 2, taken from reference [1]


References