Include(Specifications/FebioFeatures, "Specifications", 2, from="== Set Definitions for Elements, Nodes, and Surfaces ==", to="=== Progress ===")

Progress

As part of the release of FEBio2 a new file format for the input files is planned. This new format defines the Geometry in terms of named element sets, where an element set groups elements of the same type and material. Multiple named element sets can be defined. The structure is very similar to the Abaqus format in terms of element definitions. For example:

<Elements type="hex8" mat="1" name="Part01">
   <elem id="1">1,2,3,4,5,6,7,8</elem>
   <elem id="2">9,10,11,12,13,14,15,16</elem>
</Elements>
<Elements type="quad4" mat="2" name="Part02">
   <elem id="3">17,18,19,20</elem>
</Elements>

A similar structure can be added for surfaces and node sets. A specific case study might be helpful in determining the specifics of this capability.

-- ["aerdemir"] DateTime(2013-12-20T09:20:59Z) This is great initiative. Will it be possible to add the same element(node/surface) to different sets? Will set information be available in the output file? We will provide a test problem.

I've implemented support for surfaces in the new FEBio file format. Users defines surfaces in the Geometry section of the input file. These surfaces can be used in the contact and surface_load sections of the input file to define the contacting or loaded surfaces. For example:

<Geometry>
        <Elements type="hex8" name="Part01">
                ...
        </Elements>
        <Surface name="surface01">
                <quad4 id="1">1,2,3,4</quad4>
                ...
        </Surface>
        <Surface name="surface02">
                <quad4 id="1">1,2,3,4</quad4>
                ...
        </Surface>
</Geometry>
<Contact>
        <contact type="sliding_with_gaps">
                <laugon>0</laugon>
                <penalty>1</penalty>
                <surface type="master" set="surface01"/>
                <surface type="slave"  set="surface02"/>
        </contact>
</Contact>

This example defines two surfaces through the "surface" elements. Each surface defines a name which will be used to reference back to this surface. In the contact definition the master and slave surfaces are then defined using the "set" attribute which references the previously defined surfaces using the name.

A similar capability was added for node sets. A user can now define a node set in the Geometry section and then use this node set in the fix and prescribe boundary conditions.

<Geometry>
        <NodeSet name="nodeset1">1:100:5,101,102,103,120:130</NodeSet>
</Geometry>
<Boundary>
        <fix bc="x" set="nodeset1"/>
</Boundary>

The following example implements the test problem using the set definitions attachment:sets01.feb .

-- ["belgiansteve"] DateTime(2014-06-04T16:49:31Z) Support for exporting surfaces was added to PreView. In version 1.14 you can name the surfaces for boundary loads and contact definitions. When the surfaces are named, PreView will create a surface section for each named surface in the output file and only puts a reference to the surface in the load or contact definition (as in the examples above).

-- ["belgiansteve"] DateTime(2014-06-25T17:00:32Z) The FEBio plotfile format now stores the names of all sets, including node sets, surfaces and parts as they are defined in the FEBio input file. It now also includes the node list for all user-defined node sets. Preliminary support was added to PostView for reading the node sets and the set names. Custom file parsers can now use this information to extract data specific to a certain set from the plot file. For domains and surfaces, data can be extracted directly for a given set and state (i.e. time step). Nodal values are still stored for all nodes, but by extracting the node set list, it should be easy to figure out the values just for the nodes belonging to that specific node set.