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Shear deformation gradient and shear rate
Visualisation of the shear rate and shear deformation gradient
Under the menu item Graphic > Shear deformation gradient /Shear rate a detailed graphical representation of the mechanical shear stress along the length of the screw is called up.
Interpretation of the curves
- Red curve: The red solid curve represents the shear rate along the screw and is a direct measure of the shear stress on the plastic.
- Blue curve: The blue curve represents the shear deformation gradient. The shear deformation gradient is a physical quantity that describes the rate of material deformation, i.e. how much the material is deformed by the mechanical forces. This variable provides information on how the material stretches or compresses as a result of the screw rotation and is a measure of the laminar shear mixing effect.
- Red dotted curve: The red dotted line represents the shear rate across the web of shear parts.
- Blue dotted curve: The blue dotted line represents the shear deformation gradient across the web of shear components.
Analysis of the shear deformation gradient and the shear rate
- Shear rate (red curves): The shear rate has a strong influence on the shear dissipation and thus on the temperature development and melting rate in the extruder. In principle, the shear rate should not be too high, as this is associated with material damage.
- Shear deformation gradient (blue curves): The shear deformation gradient is a measure of the laminar mixing effect. A higher value is therefore advantageous for the mixing effect. However, distributive mixing is not taken into account here and the shear deformation gradient must therefore not be overestimated in comparison to mixing elements.