The viscosity of the plastic changes as a function of shear rate (and temperature) and I'm not sure how I should be modeling this material.
When you are looking at a plastic flow simulation you can model the viscosity variation with any of the following variation methods: 2nd order polymer, 1st order polymer, and Power Law.
2nd order polymer: This is the most elaborate and encompassing variation method available in Simulation CFD. Use of this model does require some data processing in Excel. There is an excel sheet attached to this article that you can use to calculate the 6 coefficients that define the 2nd order polymer material definition.
1st order polymer: This model will take in to account Shear and Temperature effects. Use of this model does require some data processing in excel. There is an excel sheet attached to this article that you can use to calculate the 3 coefficients that define the 1st order polymer material definition. To use this spreadsheet you will need to leverage the SOLVER function in Excel.
After you apply the material to your volumes in Simulation CFD, make sure that you change the material environment settings to be variable instead of fixed.
Some common questions:
Do you know of a good method to extract data from my chart? I do not have a table of my rheology data. One option is to use a tool that is available on the internet located here. This will help you estimate point values off a curve more accurately.
Is there a difference between Shear Rate and Strain Rate? Not for this software.
Should I model the plastic flow with the laminar or turbulence solver? Running with the laminar solver is suggested.
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