Shear rate result

The Shear rate result shows the rate of shear strain (the velocity gradient through the cross-section) in the mold-cavity at the time the result was written.

This is an intermediate result which is available for all analysis technologies.

Note: For compression-type molding processes, this result is plotted displayed on the deformed mesh as the default setting. With this default setting, if you click through the time steps you can watch the polymer as it is compressed into the part shape. To turn it off, so that all you see is the result on the part, right-click the result, select Properties and uncheck Display on deformed mesh.

Using this result

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 Shear rate result may have small portions of the cross–section that are above the the maximum material limit while the bulk shear rate remains below this limit. Regions above the limit could be subject to material degradation, embrittlement and poor surface finish.

When the maximum shear rate is much larger than the bulk shear rate, it is useful to look at the shear rate as an XY graph.

Things to look for

• High shear rates tend to occur in the feed system (where the greatest velocities are).
• To reduce the shear rate, increase the cross–section or decrease the flow rate