The Shear rate, bulk result plot shows the magnitude of the shear rate through a cross-section.
Shear rate, bulk is derived from the wall-shear stress and the fluidity, and characterizes the magnitude of the shear rate through a cross-section. A representative viscosity is first calculated from the fluidity and the thickness of the part. The Shear rate, bulk is then calculated from the wall-shear stress and this representative viscosity.
The shear rate is a measure of how quickly the layers of plastic are sliding past each other. If this happens too fast, the polymer chains break and the material degrades.
The bulk shear rate should not exceed the maximum value recommended for the material in the material database. Exceeding this value would likely lead to polymer degradation.
As temperature does, shear rate varies with thickness. A bulk shear rate gives an overview of the shear rate distribution in the filling stage. In contrast to the bulk temperature, the bulk shear rate is not an average or weighted average of the shear rate across the thickness. An average or weighted average is not suitable because the shear rate can vary widely across the part thickness.