Creating Your First Model in FEBio Studio

Prepared for FEBio Studio 2.0

Overview

This tutorial is the first part in a series of introductory tutorials on FEBio Studio and demonstrates how to setup a simple structural mechanics analysis with FEBio Studio. It walks the user through the steps of creating the geometry, meshing the geometry, and assigning materials and boundary conditions. The next tutorials will show you how to run this analysis and visualize the results.

Step 1: Creating a New Model

After opening FEBio Studio on your machine, the Welcome screen is presented. To start a new model, click the New Model link on the Welcome screen, or select the menu File\New Model. A dialog box appears that allows you to select the FEBio module that you want to use (see here for more information on FEBio modules).

Choose the “Structural Mechanics” module. Enter a name for the model (or accept the default) and click OK.

It is important to save your model often. To save your model, select the menu File\Save, clicking on the save icon in the upper left corner, or by pressing Ctrl+S.

Step 2: Creating the Model Geometry

In this step, the geometry of the model is created.

Step 3: Adding a Mesh to the Model

Now that the geometry is defined, we need to create the finite element mesh that FEBio needs to solve the problem.

Step 4: Creating a Material

With the geometry and mesh created, we can move on to defining the physical properties of the model. We’ll start by creating a material that defines the constitutive behavior of the box.

1. Open the dialog for creating materials by selecting Physics -> Add Material from the menu, by right clicking on Materials in the Model panel on the left side of the window, and then selecting Add Material, by pressing Ctrl + M, or by clicking on the Add Material icon in the toolbar .
2. From the Category dropdown menu choose uncoupled Material, and select Mooney-Rivlin from the Material list. You can use the filter option to filter the available options. Click OK.
   
3. In the Model panel, ensure that Material 1 [Mooney-Rivlin] is selected under Materials.
4. Under the Properties section, set the following: density = 1, c1 = 1, c2 = 0, bulk modulus = 100
5. Apply this material to the box by clicking on the box in the graphics view, and then clicking the green plus icon under the Selection pane in the Model panel.
6. The box should have changed color to indicate that the material has been applied.

   

Step 5: Assigning Boundary Conditions

Next, boundary conditions will be applied. Boundary conditions prescribe the solution on parts of the geometry’s boundary and are often necessary to guarantee a unique solution to the finite element problem.

FEBio Studio makes a distinction between two types of boundary conditions (BC): nodal BC, and surface BC. Most boundary conditions can be found under the nodal BCs. Despite its name, it is possible to assign both node selection and surface selections to nodal BCs. Once the model runs in FEBio, the corresponding node sets are extracted from the selection that was assigned to the nodal BC. A surface BC, on the other hand, requires a surface selection. For these boundary conditions, FEBio requires additional information that it needs the surface definition for. For example, the “normal displacement” displaces a node in the direction of its local surface normal.

This tutorial requires only two simple boundary conditions. The left side of the box (-X) will be constrained from moving. A prescribed displacement will be applied to the right side (+X) of the box.

1. Add a boundary condition by selecting Physics\Add Nodal BC from the menu, by right clicking on Boundary Conditions in the Model panel on the left side of the window, and then selecting Add Nodal BC, or by pressing Ctrl + B.
2. Select Zero displacement from the list, give the boundary condition a descriptive name, such as “Fixed Left”, and click OK.
   
3. Under the Properties section in the Model panel, check all three boxes (X-displacement, Y-displacement, and Z-displacement). This ensures that nodes on the surfaces to which this boundary condition are applied, will be unable to move in any direction.
   
4. In order to select a single surface, click on the blue square located in the top toolbar . Click on the surface located on the left (or negative x) side of the box. If you cannot see that side of the box, rotate the view by clicking and dragging anywhere in the model view area. When properly selected, the surface should be highlighted in blue.

   

5. Ensure that your boundary condition is selected by clicking on it under Boundary Conditions in the Model panel. Add the selected surface to the boundary condition by pressing the green plus icon under the Selection section in the Model panel. If done correctly a new surface should be added to the list next to the green plus icon.

   

6. Deselect the currently selected surface by clicking on the background of the graphics view area, or by pressing the Esc key. It is important to deselect the left surface because when a new boundary is created, it would otherwise automatically be applied to any selected surfaces.
7. Add another boundary condition. Select zero displacement from the list, give the boundary a descriptive name, such as “Fixed Right”, and click OK.
8. Under the Properties section in the Model panel, check Y-displacement, and Z-displacement.
9. Add the surface located on the right (or positive x) side of the box to this boundary condition. This will prevent the right side of the box from moving in the y and z directions.
10. Add another boundary condition. This time, select Prescribed displacement from the list, give the boundary a descriptive name, such as “Prescribed”, and click OK.
11. Under the Properties section in the Model panel, select X-displacement for the Dof (Degree of freedom) parameter, and assign a value of 1 to value.
    
12. Add the surface located on the right (or positive x) side of the box top this boundary condition. This will cause the right side of the box to move a distance of 1 in the x direction.

Step 6: Adding an Analysis Step

Finally, we need to create an analysis step to define what type of analysis we want to do.

1. Add an analysis step by selecting Physics -> Add Analysis Step from the menu, or by right clicking on Steps in the Model panel on the left side of the window, and then selecting Add Analysis Step.
2. Properties for the analysis step should now be visible under the Properties section in the Model panel. For this analysis leave all settings as they are. The default analysis will perform a (quasi-) static analysis over 10 timesteps, ramping up the prescribed displacement from 0 to the prescribed value.

The model is now complete. Make sure to save the model. To learn how to run the model in FEBio Studio, proceed to the next tutorial.

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