Idealelastic materials show an immediate deformation after applying a jump-like stress, and an immediate reformation after removing the stress afterwards in the jump-like form again. For viscoelastic samples, this elastic behaviour occurs with a certain time delay.
The term "relaxation time" has been described. It is used in combination with tests presetting the strain (deformation) or strain rate (shear rate), eg, when performing relaxation tests. Relaxation is the process in a state at rest after a forced deformation.
On the other hand, the term "retardation time" is used for tests when presetting the stress, eg, when performing creep tests.
Retardation is the delayed response to an applied force or stress and can be described as "delay of the elasticity"
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