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Determination of the Yield Stress of Disperse Systems



Author(s)

Dimiter Hadjistamov

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DOI:10.17265/2161-6213/2018.7-8.003

DECE GmbH, Helvetierstr.15, Riehen 4125, Switzerland

The yield stress is defined as the stress below which the substance is an elastic solid, while above it is a liquid with a plastic viscosity. This yield stress is the stress at the yield point. We will report of probably the only system with yield stress according to this definition. The yield stress will be determined from the first visible difference between shear stress and residual shear stress. Shear flow start-up experiments and following stress relaxation will be performed. The relative residual shear stress indicates the strengthening of the structure. It will be reported about systems with pronounced one and two yield stress regions, where the shear stress changes insignificantly with the shear rate. The yield stress regions of these systems can be determined from the flow or viscosity curves and from the residual shear stress curve. System with flow curves without a pronounced yield stress region will be investigated and furthermore the conditions to have a yield stress will be determined. The definition for the yield stress will be modified/extended.

Yield point, plastic flow behaviour, yield stress, yield stress region.