Shear rate, maximum result

The Shear rate, maximum result shows the maximum shear rate at a given node, up to the time the result was written.

For example, if the shear rate at a given node reaches a maximum of 4200 1/s at time = 1.5 seconds, this is the value given for all subsequent times.

This result is generated from a Fill analysis using 3D analysis technology.

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.

Note: Use cutting planes with this result to check the maximum shear rate that is occurring inside the solid model.

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

To reduce internal shear strain:

• Slow down the flow rate.
• Use programmed injection speeds.
• Increase wall thickness.
• Avoid differential orientation and differential shrinkage.

Note: Changes such as these can only be made using a licensed Autodesk Simulation Moldflow Adviser or Autodesk Simulation Moldflow Insight product.