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Model Checking

Note: Access the Material Results Check dialog by clicking Check Results. The Material Results Check dialog checks the data models determined by the MPL data fitting server. It allows you to see easily if there are any warnings or errors.

The Material Results Check dialog checks the PVT and viscosity parameters against the following four sets of values:

  • Minimum recommended (Warning limit).
  • Maximum recommended (Warning limit).
  • Minimum physical (Error limit).
  • Maximum physical (Error limit).

Viscosity Model Checking

The Newtonian viscosity, eta0 , is calculated for the minimum and maximum melt temperature. If not in 100 < eta0 < 1000000 range, a warning is produced, and if not in 10 < eta0 < 5000000 range, an error is produced. The warnings and errors are displayed in the Material Results Check dialog. If an error is reported, you should include a wider range of shear rate data and re-submit it for data fitting.

PVT Model Checking

Compressibility

As the applied pressure increases, the specific volume should decrease (the material is being squeezed into a higher density state). The Material Results Check feature divides the pressure range (0-500 MPa) into six steps, and temperatures between the minimum mold temperature and the maximum melt temperature into 20 steps. It then calculates the specific volume for each step and checks that the specific volume decreases if pressure increases. If negative compressibility is encountered, an error is produced for pressures where p < 300 MPa and is not inside the transition zone. Otherwise a warning is generated. All warnings and errors are displayed in the Material Results Check dialog. If a warning is generated, you should check the following items.

  1. Have you entered the raw data correctly in the template?
  2. Review the warning or error message, and determine if the raw data at the temperature and pressure should be excluded as an experimental outlier. If so, you should re-fit the data and verify whether it passed.
  3. Assuming iso-thermal testing, you should determine if any raw data sets are experimentally incorrect. If so, either delete the data set or re-test. You should then re-fit the data and verify whether it passed.

Heat Expansion

As the temperature increases, the specific volume should increase (the material is thermally expanding into a lower density state). The Material Results Check feature divides the pressure range (0-500 MPa) into six steps, and temperatures between the minimum mold temperature and maximum melt temperature into 20 steps. It then calculates specific volume for all these points and checks that the specific volume increases if temperature increases. If negative heat expansion is encountered, an error is produced for pressures where p < 300 MPa and is not inside the transition zone. Otherwise a warning is generated. All warnings and errors are displayed in the Material Results Check dialog. If a warning is generated, you should follow the same steps given above for resolving compressibility issues.

Density

The Material Results Check feature checks that the solid density and melt density correspond to PVT. It generates a warning if the ratio is above 1.1, and an error if the ratio is above 1.4.

If a warning is generated, you should check the following items.

  1. Review the solid density raw data. Typically it is the average value so you should check for any experimental outliers.
  2. The melt density is typically derived from the PVT data so you should check the process by which it was determined.

If any of these PVT issues occur the raw data should be amended and resubmitted for data fitting.

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