The use of a generalized model based on the relaxation spectrum for calculation of the first normal stress difference from a flow curve

In this work a derivation has been made of a model based on the relaxation spetrum. This model can be used for the calculation of the first normal stress difference from a flow curve. The model has been generalized in order to describe better shear rate dependence of the first normal stress difference. Predictions of the generalized model are compared with experimental data. The comparison has been made for materials with dependencies taken from the literature, and also for materials investigated by the authors of this work.