Difference between revisions of "Creep"

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where the left hand side is the strain rate due to creep, ''Q'' is the activation energy of creep, ''d'' is the grain size, <math>\sigma</math> is the stress in the material, ''T'' is the temperature, and ''m'' and ''b'' are constants that depend on the mechanism of creep.
 
where the left hand side is the strain rate due to creep, ''Q'' is the activation energy of creep, ''d'' is the grain size, <math>\sigma</math> is the stress in the material, ''T'' is the temperature, and ''m'' and ''b'' are constants that depend on the mechanism of creep.
  
For a general visco-elastic material, such as a polymer,
+
For a general visco-elastic material, one can use one of several material
 +
 
 
==See also:==
 
==See also:==
  

Revision as of 21:13, 8 December 2011

Started by Lauren Hartle, Fall 2011.

Definition

Creep is the time dependent change in Strain of a material subject to a constant Stress. Creep is distinct from Plastic flow, which is often defined as time-independent permanent deformation. A Creep test and Stress relaxation test attempt to quantify the same material behavior: the timescale and functional form of molecular and/or atomic rearrangement that occurs when a material is irreversibly deformed. The mechanism of creep differs depending on the material. In a crystal, mechanisms for creep include the movement of dislocations and the diffusion of atoms along grain boundaries or through grains.

The general equation for describing creep is:

<math> \frac{\mathrm{d}\varepsilon}{\mathrm{d}t} = \frac{C\sigma^m}{d^b} e^\frac{-Q}{kT}</math>

where the left hand side is the strain rate due to creep, Q is the activation energy of creep, d is the grain size, <math>\sigma</math> is the stress in the material, T is the temperature, and m and b are constants that depend on the mechanism of creep.

For a general visco-elastic material, one can use one of several material

See also:

Creep of ice, Creep test

Keyword in references:

Homogeneous flow of metallic glasses: A free volume perspective

Stress Enhancement in the Delayed Yielding of Colloidal Gels