Manipulating Geometry and Meshing in FEMAP

This tutorial demonstrates how quickly FEMAP can modify geometry and create finite element models using the Meshing Toolbox, and Mid-surfacing and Non-Manifold Add tools

Tutorial Overview

This demonstration will show how quickly FEMAP can modify geometry and create a finite element model.

Are you looking for an indepth tutorial of FEA in Femap from start to finish?
View our Femap tutorial page (includes the geometry file that you can use).

We will walk step-by-step through the process of importing and modifying geometry in order to create a finite element model from that geometry.

To help us do that, we will be using the Mid-surfacing and Non-manifold Add Tools.

We will then cover meshing and property generation using the Meshing Toolbox.

In this article:

Importing CAD Geometry
Geometry Manipulation
Midsurfacing
Correcting Free Edges
Creating Meshing Surfaces
Final Steps and Conclusion

Importing CAD Geometry

The first thing to do is import the CAD geometry. To do that, go to File > Import > Geometry and then select the geometry file you want to import.

importing geometry

File > Import > Geometry

Solid Model Read Options

Scale factor is 39.97 to convert meters to inches

Set the geometry scale factor to 39.37 because the geometry is in meters and we want our graphic to come in inches.

FEMAP is neutral when it comes to units, so you can use any units you want – as long as you remain consistent.

The imported geometry comes into the active layer.

Isolate the geometry that will be using for meshing (in this case, the grey solid).

To do so, create a new layer that the geometry will go into. (We named ours “Bracket Solid”)

3. new layer4. bracket solid

Then place the solid into that layer.

5. solid in new layer

Modify > Layer > Solid

6. solid in new layer
Select “Show Selected Only” to isolate the geometry we’re looking for.

7. show only layer8. solid only

Geometry Manipulation

The next thing to do is prepare the geometry for mid-surfacing. As you can see, it has fillets, holes, and other things that we don’t want to model.

To clean the geometry, go to Meshing Toolbox > Feature Removal.

9. feature removal

Meshing Toolbox > Feature Removal

Removing Holes

First remove the small holes around the larger holes. They are not necessary to represent the structure.

Move to the loops command. To remove the holes, just select any curve on the circle.

10 removing small holes

Click on any curve along the circle to remove it


11 no more holes

All small holes removed!

Removing Fillets

Next remove the fillets. The fillets are going to cause issues with the mid-surfacing tool.

Go to Feature Removal > Surfaces.

12 selecting fillets

Feature Removal > Surfaces

To remove fillets properly, you have to select all the surfaces in a loop. Otherwise you could run into errors with the geometry modification.

Continue to select all the surfaces in one continuous loop. If you want to check the surfaces that you have selected, you can highlight it; showing clearly the surfaces you have selected.

13. highlight

Selected Surfaces Highlighted

Click OK and it will remove all those surfaces, leaving nice sharp corners. Repeat this step to remove all unnecessary fillets.

Now that all the fillets in the model are removed, we are ready to start mid-surfacing.

Removed fillets leaves us with sharp corners.

Clean Sharp Corners

Midsurfacing

Create a new layer to put the surfaces into (we named ours Bracket Midsurfaces) and turn the layer on.

15. bracket midsurfaces layer

Next perform the mid-surfacing command by going to Geometry > Mid-surface > Automatic. Select all the surfaces on the bracket.

16. midsurface automatic

To determine the target thickness, you can measure the thickness of the bracket. Since most of the thicknesses on the bracket are similar, we just measured one area and selected a target thickness of 0.2 inches.

Select “Combine Midsurfaces” so that it will combine all the surfaces it creates into one solid, allowing us to avoid any coincidental curves.

17. automatic midsurface generation

Target thickness of 0.2 inches and “Combine Midsurfaces” selected

Now that the surfaces have successfully been created, they can be viewed by turning off the Bracket Solid layer, leaving the 2D surfaces that were created.

18. viewing midsurfaces

Turn the “Bracket Solid” layer off to view the 2D Midsurfaces

Checking Free Edges

Check the free edges on these surfaces just to make sure that it performed correctly.

To do that, go to the Meshing Toolbox. Turn on the “Toggle Entity Locator” and select Free Edges.

19. toggle entity locator20. free edges
As you can see it created some free edges where we don’t want them.

Zoom in to see what the mid-surfacer did. As you can see, it created a sliver surface that we’re going to want to get rid of, and messed up the end of the foot. We’re going to get rid of those surfaces and recreate them.

21. messed up midsurfaces

 

Correcting Free Edges

First select and delete those surfaces.

22. deleting midsurfaces

Now recreate those surfaces by going to Geometry > Surface > Corners.

23. geometry surface corners

Geometry > Surface > Corners

Select the corners of the surfaces you want to create.

24. selecting corners

Next add the circles back by projecting them onto the surface.

First project the curves from the solid onto the surface. To do that go to Geometry > Curve – From Surface > Project and select the surface. Then select the curves you want to project onto that surface.

curve to surfaceprojecting curves

We also want to do that to the bottom to create our property regions for the bottom surface. Redo the command Geometry > Curve – From Surface > Project. Now the circles on that surface can be deleted.

deleted circles

Now that the surfaces have been created, add them to the solid of the rest of the bracket.

To do that, use the non-manifold add command. Geometry > Surface > Non-manifold add.

25. non manifold adds

Geometry > Surface > NonManifold Add

Select the surfaces. When you perform this command it will display the free edges, showing that we no longer have the unwanted free edges.

Creating Meshing Surfaces

Breaking Up the Surfaces

Now we’re ready to start breaking these surfaces into meshing surfaces. Go to the Geometry Editing tab under the Meshing Toolbox.

We will start at the feet.

Meshing around a hole can prove challenging. One of the geometry meshing tools that makes this easy is the Pad command.

26. pad

Using the “select”, select a curve on any circle and it will create a pad around that circle that will create a math-mesh, creating a nice circle. Repeat the pad command on all of the feet.

27. padding

Continue breaking up the surfaces into meshing surfaces by using to the point-to-edge command. This is good for creating more rectangular surfaces, which are good for meshing. It can then be broken up further by using the point-to-point command.

28 point to edge 31 point to point

Determining where you want to break up surfaces will come from  experience and trail-and-error.

Meshing

Now that the surfaces have been broken up, we’re ready to start meshing. The bottom has a variable thickness so we will create multiple property regions with varying thicknesses.

First create the material and property regions. Create a new material and load one in from the FEMAP presets. (We chose aluminum 7050)

32 new material

Next create 3 properties. First property with a thickness of 0.2 inches, second property with a thickness of .375 inches, and the third property region with a thickness of .225 inches.

first property property 2 third property

To begin meshing, go to the meshing toolbox and select the mesh surface command. From here we can select the property we want to start meshing with (the 0.2 inches property).

Set the mesh size to 0.2 inches. Select Mapped Mesh and choose the Auto Mapped Approach. Use the select tool to select the surfaces to mesh.

34 mesh surface

Tip:
If the mesh does not show up, it is likely because it switched over to a wrong layer. To fix this go to Modify > Mesh > selecting the mesh on that surface and picking the mid-surfacing layer.

When meshing the bottom, the outside ring has the thicker property so switch to the second property (Bracket t=0.375″).

On the inside, we don’t want to size any of those so we turn mesh sizing off and change property over to the last option (Bracket t=0.225″).

mesh sizing off

Final Steps

35 wrong surface mesh

As you can see, all the mesh looks the same, so how can you tell where your property regions are?

We can select coloring with property colors as opposed to element coloring.

They will still all the same color. To change the property colors, go to Modify > Color > Property > Select All > Random

Once the colors have been randomized, turning off the filled edges, nodes, and surfaces allows you to see the property regions that were created.

37 property regions

Lastly check the free edges to make sure there are no unwanted free edges. And we can see, there are no unwanted free edges.

38 free edge view39 no unwanted free edges

And just like that we have our finished mesh of the bracket!

Conclusion

As you have seen from this demonstration, FEMAP can quickly create meshes of your objects, and also provides the tools you need to deal with any troublesome geometry.

Find out how to analyze this meshed bracket