High frequency parallel plate probe for the measurement of the complex viscosity of liquids

In this work an instrument is described which measures the complex shear viscosity of liquids in the kHz frequency range. The instrument is driven electromagnetically and operates in resonant mode. The measurement of the primary data, from which the rheological properties of the fluid sample are inferred, does not include any deflection amplitude measuring step and is purely digital. Models allowing the interpretation of the probe primary data in terms of fluid complex viscosity are presented. The theoretically predicted mechanical behaviour of the probe is compared with the measured one and the rheometric ability of the device is discusse

High frequency parallel plate probe for the measurement of the complex viscosity of liquids

ISSN:0035-4511ISSN:1435-152

Extreme Yield Figures for Universal Strength Criteria

We propose a universal, generally applicable yield criterion that describes a single convex surface in principal stress space encompassing extreme yield figures as convexity limits. The novel criterion is derived phenomenologically exploiting geometrical properties of yield surfaces in principal stress space. It is systematically compared with known yield criteria using different forms of visualization. Using a I1-substitution the criterion is applicable to materials with pressure-sensitive behavior and contains well-known strength criteria. Introducing appropriate parameter restrictions, it can be applied for the modeling of ductile and brittle material behavior. The implementation of the present criterion eliminates the necessity of choosing a specific yield criterion for a particular material. The proposed criterion allows for excellent approximation of experimental data. It is applied to measured data of concrete and provides better accuracy than existing criteria from literature