Sinusoidal normal stress measurements with the Weissenberg rheogoniometer

In measuring sinusoidal normal stress difference of concentrated polymer solutions in a Weissenberg rheogoniometer, the resistance to motion of the upper platen due to the sample between the cone and plate should be taken into account. Correction terms are derived. The theoretical predictions of Lodge and others concerning the relationship between oscillatory normal stress difference and oscillatory shear stress are found to agree with experimental data if these corrections are applied.