Parameters Influencing the First Normal Stress Difference

17 PARAMETERS INFLUENCING THE FIRST NORMAL STRESS DIFFERENCE 

The time-temperature correspondence principle holds not only for the viscosity but also for the normal stresses. In the latter case, however, the 

The shear rate dependence of the viscosity and that of the normal stress difference Ni for a viscoelastic fluid follow opposite trends. Thus the first parameter decreases with increasing values of k, while the second increases. It is noteworthy to remark once more that viscoelastic fluids may present nonlinear effects, expressed by the normal stresses, in regions in which the shear stress is a linear function of the shear rate. However, these viscoelastic systems are still called Newtonian fluids due to the fact that the viscosity is independent of the shear rate. 

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Parameters Influencing the First Normal Stress Difference 557... 

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