Definitions - Selections
Regardless of whether the geometry is treated as a single entity or as an assembly, you still may need to access different parts of it for definitions, such as multiple specifications of similar boundary conditions. There are different ways in which you can create selections, for example by explicit selection of objects or by geometrical location. A box selection is independent of the geometry, and allows you to change the geometry topology while still keeping the desired selection.
In this example, one selection contains the bolt regions, while other selections contain the boundaries of the pin holes that carry load.
Bolt 1
1
In the Definitions toolbar, click Explicit . An Explicit node is added under Definitions > Selections.
2
In the Settings window for Explicit, in the Label text field, type Bolt 1. You can also click any node in the model builder tree and press F2 to rename, or right-click and select Rename.
3
In the Graphics toolbar, click Wireframe Rendering in order to see also hidden boundaries better.
4
Locate the Input Entities section. From the Geometric entity level list, choose Boundary.
5
Select Boundary 41 only. Note how it is highlighted in the graphics window.
6
Select the Group by continuous tangent checkbox. Boundary 40 is automatically added to the selection list.
Bolt 2, Bolt 3, and Bolt 4
Repeat the steps completed for Explicit 1 to add a total of four Explicit nodes .
1
In the Definitions toolbar, click Explicit three times.
2
In the Model Builder click each Explicit node to open the Settings window.
3
Use the table as a guide, and in the Graphics window, select the boundaries as indicated. Click to select the Group by continuous tangent checkbox for each node.
Default Node Label
New Node Label
Select this Boundary
Explicit 2
Bolt 2
43
Explicit 3
Bolt 3
55
Explicit 4
Bolt 4
57
The node sequence under Definitions should look like this at this point:
You will now create a selection containing all the bolt holes.
Bolt Holes
1
In the Definitions toolbar, click Union .
2
In the Settings window for Union, in the Label text field enter Bolt Holes.
3
Locate the Geometric Entity Level section. From the Level list, choose Boundary.
4
Locate the Input Entities section. Under Selections to add, click the Add button .
5
In the Add dialog, in the Selections to add list, choose Bolt 1, Bolt 2, Bolt 3, and Bolt 4.
6
Click OK.
7
Locate the Color section. On Windows, select the eighth color in the first row of the palette (a pink color). On other platforms, choose Color 8 from the Color list.
Note: This assumes default settings for color themes.
Now, create selections for the two holes carrying the load.
Left Pin Hole
1
In the Definitions toolbar, click Explicit .
2
In the Settings window for Explicit, in the Label text field, type Left Pin Hole.
3
Locate the Input Entities section. From the Geometric entity level list, choose Boundary.
4
Select Boundary 4 only.
5
Locate the Color section. On Windows, select the ninth color in the first row of the palette (a light blue-gray color). On other platforms, choose Color 9 from the Color list.
Right Pin Hole
Repeat the steps above, but use the label Right Pin Hole, select Boundary 75, and use the second color in the second row (a light brown color) on Windows platform, or choose Color 12 on other platforms. Now the sequence under Definitions should look like this:
Pin Holes
Add a selection that combines the pin hole boundaries on both sides.
1
In the Definitions toolbar, click Union .
2
In the Settings window for Union, type Pin Holes in the Label text field.
3
Locate the Geometric Entity Level section. From the Level list, choose Boundary.
4
Locate the Input Entities section. Under Selections to add, click Add .
5
In the Add dialog, in the Selections to add list, choose Left Pin Hole and Right Pin Hole.
6
Click OK.
Bolt Hole Edges
Add one more selection to be used during mesh generation.
1
In the Definitions toolbar, click Adjacent .
2
In the Settings window for Adjacent, in the Label text field, type Bolt Hole Edges.
3
Locate the Input Entities section. From the Geometric entity level list, choose Boundary.
4
Under Input Selections, click the Add button .
5
In the Add dialog, select Bolt Holes in the Input selections list.
6
Click OK.
7
Locate the Output Entities section. From the Geometric entity level list, choose Adjacent edges. Note how the edges of the bolt holes are highlighted.
8
In the Graphics toolbar, click Wireframe Rendering to reset the graphics to a view with hidden surfaces.
Centroid Measurement 1
As a preparation for adding load in the pin holes you will add a local coordinate system. Start by finding the location of the pin hole center line. You can directly create parameters for the coordinates that can be referenced in other nodes.
1
In the Geometry toolbar, click Measurements  and choose Centroid Measurement .
2
On the object par1, select Point 2 and 5 only. These are two points on the outer side of the left pin hole.
3
Locate the Parameter Names section. In the x text field, type PinHoleX.
4
Then type PinHoleY and PinHoleZ, in the y and z text field respectively.
5
In the Settings window for Centroid Measurement, click Build Selected .
Cylindrical System 2
Since the load in the pin holes has a dependence on the angle, it is convenient to use a cylindrical coordinate system aligned with the pin to express the load.
1
In the Definitions toolbar, click Coordinate Systems , and choose Cylindrical System.
2
In the Settings window for Cylindrical System, locate the Settings section. Enter data as shown.
3
Locate the Coordinate Names section. From the Frame list, choose Material (X, Y, Z)
Note how two cylindrical systems with different reference orientations are created by making the orientation of the reference axis dependent on in which arm the system is referenced. This can be done by using the sign of the X-coordinate.