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Subsubsection 4.5.1.1: Exponential Up Subsection 4.5.1: Relaxation Functions Subsubsection 4.5.1.3: Fung

#### 4.5.1.2 Exponential Distortional

The material type for this relaxation function is “relaxation-exp-distortion”. The following material parameters need to be defined:
 Characteristic relaxation time [t] Characteristic time Power exponent
The reduced relaxation function for this material type is given by where In general, where is the spatial natural (Hencky) strain tensor and is the left stretch tensor. In this expression, is the second invariant of the natural strain tensor evaluated from the relative deformation gradient . is evaluated at the time when weak bonds from the generation start breaking.
Subsubsection 4.5.1.1: Exponential Up Subsection 4.5.1: Relaxation Functions Subsubsection 4.5.1.3: Fung