Wagner model
Wagner model is a rheological model developed for the prediction of the viscoelastic properties of polymers. It might be considered as a simplified practical form of the Bernstein-Kearsley-Zapas model. The model was developed by German rheologist Manfred Wagner.
For the isothermal conditions the model can be written as:
where:
The strain damping function is usually written as:
The strain hardening function equal to one, then the deformation is small and approaching zero, then the deformations are large.
The Wagner equation can be used in the non-isothermal cases by applying time-temperature shift factor.
