Creating Springs
FEBio supports several types of discrete elements that allow users to connect different parts of a model. Springs are often used to model supporting tissues and structures that are not the main structures of interest, but often needed to provide stability or loading to a model. In this tutorial, we’ll take a look at creating springs in FEBio Studio.
Creating the springs
To create springs, select the spring option on the Create tab of the Build panel.
The first step in creating springs, is to create a new discrete element group. To do that, click the New… button, next to the Group option. A new dialog box appears where you can enter a name for the group and the type of the discrete elements in this group.
Close the dialog box and return to the Build panel. Make sure the value of the Group field is the newly create group.
The next step is to select the nodes that will be joined via springs.
To select nodes, click on the node-selection button on the main toolbar (button with three blue dots). Then, click the nodes that make up one of the ends of the springs and assign them to the Nodeset1 field on the Build panel. (You can assign the nodes by clicking the green plus button in selection box.) Next, select the nodes that make up the other end of the springs and assign them to the Nodeset2 selection box. At this point, FEBio Studio will render a preview of where the springs will be created in the model.
Below the two selection boxes, you can select the method that will be used to connect the nodes with springs.
- closest point: Each node of nodeset1 will be connected to the closest (unused) node of nodeset2.
- closest line projection: A imaginary line is defined that interpolates the nodes of nodeset2. Each node on nodeset1 will be projected to this line, and then connected to the point in nodeset2 that is closest to this projection.
Finally, to add the springs to the model, click the Create button at the button of the parameters pane.
Editing Spring Parameters
After the springs are created, a new item will show up in the Model panel, under the Discrete item. The new item will have the name of the group that the springs were assigned to. Selecting the item will show the properties panes that can be used to edit the spring group.
In the Object pane, you can change the name of the spring group, and set the color that is used to draw the springs of this group in the Graphics View.
In the Properties pane, you can edit the spring properties. Note that all springs that belong to this group will be assigned the same properties.
The Selection pane lists the individual springs that belong to the group. If the lists is compacted (e.g. [items:4]), then double-click this line to expand the list. Then, you can click on each item. To select the corresponding spring in the Graphics View, double-click the item or click the arrow button on the right side of the pane.
Adding/Removing Springs
To add springs to an existing group, open the spring creation tool as above. This time, instead of creating a new group, select the group to which new springs will be added. Then, follow the same procedure as above to create springs. When you now click the Create button, the new springs will be added to the group.
To remove springs from a group, you can either select the spring in the selection box and press the Delete button to remove the spring. Alternatively, you can select the spring in the Graphics View. To select springs, select the spring selection button on the main toolbar. Then, click the spring to delete, and press the Delete key (or the Edit\Delete Selection menu item). Note that deleting springs can not be undone.