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.
When the Shear rate result is displayed, scale the result using and select the Scaling tab to show very high shear rates. The bulk shear rate should be less than the maximum recommended for the material.
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.