Glossary

Casson Analysis

The Casson model is used to characterize the flow behavior of fluids, exhibiting Yield StressYield stress is defined as the stress below which no flow occurs; literally behaves like a weak solid at rest and a liquid when yielded.yield stress behavior, such as chocolate, blood, or printing inks. It is expressed as:

Example: Casson analysis on two different chocolates

The figure below shows the curves of the shear StressStress is defined as a level of force applied on a sample with a well-defined cross section. (Stress = force/area). Samples having a circular or rectangular cross section can be compressed or stretched. Elastic materials like rubber can be stretched up to 5 to 10 times their original length.stress measured for milk chocolate and dark chocolate (brown and black symbols, respectively). The curves can be described by a mathematical fit based on the Casson model (continuous lines). The resulting parameters are given in the table.

• The Casson Yield StressYield stress is defined as the stress below which no flow occurs; literally behaves like a weak solid at rest and a liquid when yielded.yield stress of the dark chocolate is much higher in comparison with the milk chocolate, meaning that pumping would be more difficult, i.e., requires a higher force.
• The plastic shear viscosity is lower for the milk chocolate. This ensures smoother flow and easier chocolate transfer through pipes during manufacturing.