Oscillating-cup viscometer for nonlinear fluids in forced mode

We analyze the oscillating-cup viscometer to operate in the forced mode. The amplitude-frequency characteristics are studied for the viscometer with linear and nonlinear fluids depending on experimental conditions. Some methods to identify their rheological properties are proposed. We develop an analytical approach for these nonlinear problems and construct it on the basis of the exact solutions for the linear fluids. The approach gives a high degree of agreement and is simple enough to use in practice. The results extend the theory of both the viscometry of molten melts and the nonlinear oscillatory rheometry.