# Retardation time

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{{Short description|Delayed response to an applied force or stress}}
{{distinguish|Retarded time}}
{{One source|date=November 2024}}
{{Use dmy dates|date=November 2024}}

'''Retardation''' is the delayed response to an applied [force](/source/force) or stress, which can be described as "delay of the elasticity".<ref>{{cite book|url=https://books.google.com/books?id=N9Fdn0MEIDIC|title=The Rheology Handbook: For Users of Rotational and Oscillatory Rheometers|first=Thomas G.|last=Mezger|date=1 January 2006|publisher=Vincentz Network GmbH & Co KG|isbn=9783878701743|via=Google Books}}</ref>

Ideal elastic materials show an immediate [deformation](/source/Deformation_(mechanics)) after applying a jump-like [stress](/source/Stress_(mechanics)), and an immediate reformation after removing the stress afterwards in the jump-like form again. For [viscoelastic](/source/viscoelastic) samples, this elastic behaviour occurs with a certain time delay.

The term "[relaxation time](/source/relaxation_time)" has been described. It is used in combination with tests presetting the strain (deformation) or [strain rate](/source/strain_rate) ([shear rate](/source/shear_rate)), e.g., when performing [relaxation tests](/source/Stress_relaxation).

On the other hand, the term "retardation time" is used for tests when presetting the stress, e.g., when performing [creep tests](/source/Creep_(deformation)).

==See also==
* [Creep-testing machine](/source/Creep-testing_machine)

==References==
{{Reflist}}

Category:Rheology

{{Classicalmechanics-stub}}

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