A simple phenomenological non-Newtonian fluid model

In this work, a simple phenomenological generalized Newtonian law model has been proposed and tested for different polymer melts by using rheological data taken from the open literature. Viscosity is given as a specific function of three principal invariants of the deformation rate tensor, D, and its absolute value defined as D⋅D. It has been found that the model predictions are in very good agreement with the strain rate dependent steady shear and uniaxial extensional viscosities for linear and branched polyolefines. The model behaves correctly in description of steady planar and equibiaxial extensional viscosities and allows their independent strain hardening level control with respect to uniaxial extensional viscosity.