How to Prepare a Bone Model for FEA

Transferring the model to 3-matic:

1. Open your femur FEA file in Mimics Core.
2. Copy the wrapped femur object in the Objects pane, and paste it into the Object Tree in 3-matic.
3. Rename the model to Femur and change its color to a bone-like shade in the Properties pane at the bottom of the interface.
4. Review the object metadata, such as volume and triangle count, to understand the current state of the model.

Visualizing and smoothing the surface mesh:

1. Change the view via the blue circle icon on the left-hand side of your screen. Click Filled with Triangle Edges to show triangle edges or use the shortcut Shift + F3.
2. Apply the Smooth tool, located under the Fix menu, to address rough or irregular areas.
3. Choose your desired Smooth factor in the Operations pane and click Apply.

Uniform remeshing:

1. Open the Uniform Remesh tool from the Remesh menu to create a more regular triangle structure.
2. Set the Target triangle edge length (e.g., 1.5 mm) under Parameters in the Operations pane.
3. Review the estimation of generated triangles and memory usage before clicking Apply.

Checking mesh quality:

1. Launch the Fix Wizard under the Fix menu to ensure the model is free of intersecting triangles before volume meshing.
2. Select all diagnostic items except for Overlapping triangles, which are less relevant for this workflow.
3. Click Update, select Follow advice repeatedly until all values in the list turn green, then click Apply.

Creating a volume mesh:

1. Select the Create Volume Mesh tool, located under the Remesh menu.
2. Under Mesh Parameters, set the Maximum edge length to a value slightly larger than the surface mesh edge length.

Visualizing the internal volume mesh:

1. Navigate to the Section List in the Object Tree, and right-click on Standard Section — Y to Show it.
2. In the Standard Section — Y tab within the Properties pane, check the box next to Clip and change the Position of the plane.
3. Analyze the mesh metadata by clicking Analyze Mesh under Object Tree — Femur — Metadata.

Converting to Tet10 elements:

1. Open the Convert Volume tool in the Remesh menu.
2. Select the Femur in the Object Tree and choose the Conversion Type Tet4 to Tet10, then click Apply.
3. Save your project.

Transferring back to Mimics Core:

1. Select the volume mesh in the 3-matic Object Tree and press Ctrl + C.
2. Switch to Mimics Core and press Ctrl + V to paste the mesh.
3. The mesh will appear in the Objects list, represented by a cube with dots on its corners.

Assigning material properties:

1. Open the Assign Material tool from the FEA menu.
2. Select the Femur copy and click OK.
3. If following the Gray value-based method, assign properties based on the Hounsfield units of the original CT scan.
4. For all voxels with Hounsfield units of 100 and lower, assign a single density value of 50 kilograms per cubic meter.
5. For Hounsfield units of 101 and higher, instead of assigning a constant value, assign a lower and upper value and then divide the interval into 10 parts with ascending densities.

Configuring material type 1 parameters:

1. Set the Gray value range from a minimum of -90 to a maximum of 100.
2. Input the parameters: a density of 50, Young's modulus values of 0.004 and 2.01, and a Poisson coefficient of 0.3.

Configuring material type 2 parameters:

1. Click the + icon next to Material Type 1 to create a Material Type 2 tab.
2. Select the Material Type 2 tab and set the minimum Gray value to 101. Leave the maximum at its default value.
3. Check the box next to Density.
4. For Point 1, 100 Hounsfield units corresponds to a density of 50.
5. For Point 2, fill in the maximum Hounsfield units corresponding to a density of 1900.
6. Fill in the rest of the Material expressions as you did for Material Type 1.
7. Click Apply and then Close to end the material assignment.

Final property visualization:

1. Launch the Clipping tool, represented by an icon showing a green object and dotted lines surrounding it.
2. Select the Coronal view and toggle Texturing to None.
3. Observe the clipping plane as it updates based on the image slice seen in the coronal view.

Exporting to a solver program:

1. Navigate to the File menu, select Export, click Meshes, and select the correct program.
2. Select the Femur_copy mesh in the Objects pane, choose your Output directory, then click Apply.
3. Use the Save as tool to save the project under Femur FEA Final.