Creep

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Revision as of 21:13, 8 December 2011 by Lauren (Talk | contribs) (Definition)

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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.

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