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en:grafische_darstellung_der_ergebnisse:scherdeformationsgradient_und_schergeschwindigkeit [2024/11/17 19:17] – neelesten:grafische_darstellung_der_ergebnisse:scherdeformationsgradient_und_schergeschwindigkeit [2025/09/05 10:27] (aktuell) – [Analysis of the shear deformation gradient and the shear rate] neelest
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 ======Shear deformation gradient and shear rate ====== ======Shear deformation gradient and shear rate ======
  
-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. This representation shows the extent to which the material is deformed and sheared during the extrusion process by the mechanical movement of the screw. Shear rate and shear deformation gradient are decisive variables that have a direct influence on the quality of the melt, the homogeneity and the thermal stress of the material.+===== Visualisation of the shear rate and shear deformation gradient =====
  
-===== Shear rate =====+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.
  
-The shear rate describes the relative movement of the material in the screw flight. It is one of the most important variables in the plasticising process, as it largely determines the shear energy that acts on the material.+{{ :grafische_darstellung_der_ergebnisse:rex171_grafisch_en_009.png?nolink&1000 |}}
  
-  *     **Shear rate over the screw length**: The solid lines in the graph represent the shear rate along the entire length of the screw. These show how the shear rate develops in different areas of the screw and where the strongest mechanical stresses occur. +===== Interpretation of the curves =====
-  *     Typically, the shear rate increases in zones with increased compression or narrow screw flights, where the material is subjected to greater stress. In zones with a wider flight width or lower compression, the shear rate can decrease.+
  
-{{ :grafische_darstellung_der_ergebnisse:rex171_grafisch_en_009.png?nolink |}}+  * **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.
  
-=====Shear deformation gradient=====+=====Analysis of the shear deformation gradient and the shear rate=====
  
-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 is stretched or compressed by the screw rotation and is decisive for the mechanical mixing and homogenisation of the melt. +  * **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.
- +
-====Maddock shear section ==== +
- +
-Special attention is paid to the dashed lines, which represent the shear deformation gradient and the shear rate across the web of a Maddock shear section. The Maddock shear section is a special component within the screw geometry that ensures particularly intensive shearing and homogenisation of the material. In these areas, the material and the melt are specifically deformed in order to achieve optimum mixing and melting. +
- +
-=====Meaning of the visualisation===== +
- +
-The representation of the shear rate and the shear deformation gradient along the length of the screw provides important information about the mechanical stress on the material during the plasticising process. In particular, the analysis via the Maddock shear section shows how much the material is deformed in order to obtain a homogeneous melt. This information is particularly valuable for +
- +
-  *     **Optimising melt quality:** High shear rates and deformation gradients in certain zones can lead to better homogenisation of the material, which improves the quality of the end product. +
-  *     **Avoid thermal overloads:** Excessive shear rates or excessive mechanical stress can lead to overheating of the material. Careful monitoring of the shear rate and the shear deformation gradient helps to avoid thermal damage to the material. +
-  *     **Adjusting the screw geometry:** The graphical representation provides valuable insight into the screw performance. By analysing the shear forces, targeted adjustments can be made to the screw geometry to improve the material flow and increase process stability.+
  
 ===Further topics=== ===Further topics===
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   * [[en:grafische_darstellung_der_ergebnisse:scherdeformationsgradient_und_schergeschwindigkeit]]   * [[en:grafische_darstellung_der_ergebnisse:scherdeformationsgradient_und_schergeschwindigkeit]]
   * [[en:grafische_darstellung_der_ergebnisse:schlepp-druckstroemung]]   * [[en:grafische_darstellung_der_ergebnisse:schlepp-druckstroemung]]
 +  * [[faserlaengenabbau|]]
 +  * [[faserlaengenverteilung|]]
 +  * [[spannungsanalyse|]]
 +  * [[kennlinienfeld|]]
 +  * [[entgasung|]]
 +  * [[zykluszeit|]]
   * [[en:grafische_darstellung_der_ergebnisse:kurzbericht]]   * [[en:grafische_darstellung_der_ergebnisse:kurzbericht]]
   * [[en:grafische_darstellung_der_ergebnisse:langbericht]]   * [[en:grafische_darstellung_der_ergebnisse:langbericht]]