Types of Viscoelasticity
Linear viscoelasticity is when the function is separable in both creep response and load. All linear viscoelastic models can be represented by a Volterra equation connecting stress and strain:
or
where
- t is time
- is stress
- is strain
- and are instantaneous elastic moduli for creep and relaxation
- K(t) is the creep function
- F(t) is the relaxation function
Linear viscoelasticity is usually applicable only for small deformations.
Nonlinear viscoelasticity is when the function is not separable. It usually happens when the deformations are large or if the material changes its properties under deformations.
An anelastic material is a special case of a viscoelastic material: an anelastic material will fully recover to its original state on the removal of load.
Read more about this topic: Viscoelasticity
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