SHEARING FLOWS OF BKZ FLUID

Available experimental data of shearing flows are used to test the BKZ fluid model. The strain-energy function is assumed in the form U equals M(s)g(I//1,I//2), where M(s) is obtained from the small-amplitude oscillatory shearing data. The function F is then calculated from simple shearing data (either shear stress or first normal stress difference). Nonuniqueness of F is seen in the results and it is suggested that the BKZ fluid model can be used only up to moderate shear rates. The stress growth after the start of simple shearing is also predicted and compared with experimental data. The prediction of stress relaxation after the cessation of simple shearing is also made and is qualitatively in agreement with experimental data. The experimental data on several PS solutions given by Ashare were used to calculate the material functions defined in this paper.