Setting units for files opened in Femap


Units in .modfem files

Units written by QY CAD Simulation to Femap model files (*.modfem) are based on:

  • Model data, in meters

  • Study data, in SI units (meters, newtons, kilograms, seconds, and degrees Centigrade).

Femap uses a system of consistent units, which are based on the solid geometry units in each .modfem file. Then it applies conversion factors, if necessary, to align the analysis units to the same system.

How Femap interprets units from QY CAD data

In the Femap database, solid geometry defaults to inches (for English data) or to meters (for metric data).

Users working with QY CAD ANSI template files typically have no issues with units since Femap is configured to handle this case by default. ANSI units are consistent with inches, pound-force, seconds, a consistent unit of mass (slinch), and degrees Fahrenheit.

However, when working with QY CAD ISO and other metric templates whose length readout unit is millimeters or meters, you may want to set consistent units in Femap for your QY CAD models and simulation data.

Example:

Assume that your metric template is based on millimeters, and that you changed the unit of measure defined for stress and pressure on the Units tab in the QY CAD Options dialog box to megapascals (MPa). Also assume that you created a structural study in QY CAD Simulation and applied a pressure load.

  • When you save the study as a .modfem file, the model data is converted from millimeters to meters.

  • When Femap reads the QY CAD .modfem file, it applies the appropriate scale and conversion factors to obtain a consistent set of SI units, which is the standard based on meters. Therefore, in a structural study, Femap selects pascal (Pa), not megapascal, as the matching SI unit for stress and pressure. This means that you see a numeric discrepancy between QY CAD and Femap analysis results. This is not wrong, but it is different.

Opening QY CAD Simulation files in Femap

When you save a QY CAD Simulation study using the Save Femap Model File shortcut command, and then import it into Femap:

  • Femap uses the PLMXML interface and the QY CAD adapter to read the QY CAD model file.

  • Femap converts the data in the *.modfem file to whatever its current settings are.

  • You can use an option inside Femap to apply the appropriate scale factor so that the units are consistent between Femap and QY CAD.

    For more information about how to do this, see:

Transferring a model from QY CAD to Femap

When you use the Tools tab→Environs group→Femap command on the ribbon in QY CAD, you are transferring a QY CAD model via the Femap API into a Femap session. When opening the file using this method, the API only informs Femap that objects are certain sizes and values. There is no opportunity to convert units or adjust the model.

Saving FEA documents Set units for .modfem files opened in Femap

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