3.2 Module Section¶

The module section defines the type of analysis to perform with FEBio. This section must be defined as the first section in the input file. It takes on the following format:

<Module type="[type]"/>

The module tag can also be used to specify the units of the model. Although FEBio doesn't care about units, if the user specifies the unit system, the proper units of variables are stored in the plot file and visible in FEBio Studio when opening the plot file.

To specify units, use the following syntax:

<Module type="[type]">
  <units>[unit system]</units>
</Module>

where unit system can be any of the following values.

units	Description
SI	Units follow the standard definition of the international SI unit system.
mm-N-s	Millimeter-Newton-seconds unit system
mm-kg-s	Millimeter-kilogram-seconds unit system
um-nN-s	Micron-nanoNewton-seconds unit system
CGS	Centimeter-gram-seconds unit system

If the units are not defined, FEBio will not output any units for plot variables.

For example:

<febio_spec version="4.0">
  <Module type="solid"/>
  <!-- rest of file -->
</febio_spec>

The following example defines the model's units explicitly.

<febio_spec version="4.0">
  <Module type="solid">
    <units>SI</units>
  </Module>
  <!-- rest of file -->
</febio_spec>

Notes:

In version 1.2 the Module section was optional. If omitted it was assumed that the solid module was used. Since version 2.0 the Module section is required and must be the first section in the file.
Older versions of FEBio (format specification 1.2 and before) allowed you to run a poroelastic (now called biphasic) problem by simply defining a poroelastic material. This is no longer possible. You need to define the proper Module section to run a biphasic analysis. If you have a file that no longer works as of version 1.4 of FEBio, you'll need to insert the following Module section in the file as the first section of the file.

<febio_spec version="1.2">
  <Module type="biphasic"/>
  <!-- rest of the file unaltered -->
</febio_spec>