Resonances in Oscillatory Rheometry

Abstract

Resonance phenomena are discussed in detail. The influence of significant parameters as the moment of inertia and the measuring constants are enlightened and verified with measurements. It is shown that resonance frequencies weekly depend upon the moment of inertia and strongly on the geometrical coefficient of the measuring system. Both parameters form the configuration constant. If a measuring system is replaced, the moment of inertia changes little but the configuration constant changes more. Thus resonance frequencies can be shifted some decades. The comparison between the developed formalism and measurements gives good results for different rheological measuring modes. Even at pronounced resonances measurements provide proper results. The formalism can be used for the simulation of measuring values. However, deformation oscillations along the rotating axis generate resonances of higher order at higher frequencies. These phenomena contribute systematically errors and should be avoided.

Keywords

• oscillation rheometry
• resonance
• moment of inertia
• measuring modes
• frequency sweeps
• controller