Introduction to COMSOL Multiphysics 4: Building a model

Geometry Sequences

This section contains details and some depth regarding the creation of the busbar geometry using COMSOL’s geometry tools. The step-by-step instructions will lead you through the construction of the geometry using parameters set up in Global Definitions. Using parameterized dimensions aids in the execution of what-if analyses and automatic geometric parametric sweeps.

If you have not yet done so, follow the steps under the Model Wizard and Global Definitions from the “Thorough Example: The Busbar” section, starting on page 7. Then return here for the geometry modeling.

Drawing the profile of the busbar is the first step in the geometry sequence.

Right-click Geometry 1 and select Work Plane. In the Settings window, select xz-plane from the Plane list. Click the Show Work Plane button on the Settings toolbar. Continue editing the axis and grid settings in Work Plane 1.

In the Model Builder, expand the View 2 node and click Axis. Enter the values below into the Axis and Grid settings fields and select the Manual Spacing check box. Leave the Extra X and Y fields blank. Click the Apply button .

You can use interactive drawing to create a geometry using the drawing toolbar buttons while pointing and clicking in the Graphics window. You can also right-click the Geometry node in the Work Plane 1 tree to add geometric objects to the geometry sequence.

In the next series of steps, you will create a profile of the busbar.

In the Model Builder>Work Plane 1, right-click Geometry and select Rectangle. Type L+2*tbb in the Width edit field and 0.1 in the Height edit field. Click Build Selected .

Create a second rectangle. In the Model Builder>Work Plane 1, right-click Geometry and select Rectangle. Type L+tbb in the Width edit field, 0.1-tbb in the Height edit field, and tbb in the y position edit field. Click Build Selected .

Use the Boolean Difference operation to subtract the second rectangle from the first one. In the Model Builder>Work Plane 1, right-click Geometry and select Boolean Operations>Difference.

In the Graphics window, click r1 and right-click to add r1 to the Objects to add list. Click the Activate selection button in the Objects to subtract list. Right-click to add r2 to the Objects to subtract list. Click Build Selected . You should now have a backward-facing, L-shaped profile. Continue by rounding the corners using fillets.

In the Model Builder>Work Plane 1, right-click Geometry and select Fillet. In the Graphics window, click point 3, the inner corner, and right-click to add it to the Vertices to fillet list. Type tbb in the Radius edit field. This takes care of the inner corner.

For the outer corner, right-click Geometry and select Fillet. In the Graphics window, click point 6, the outer corner, and right-click to add it to the Vertices to fillet list. Type 2*tbb in the Radius edit field. Click Build Selected .

The resulting profile should look like below.

Next you extrude the Work Plane to create the 3D busbar geometry.

In the Model Builder, right-click Work Plane 1 and select Extrude. In the Settings window, enter wbb in the Distances table to extrude to the width of the profile. Note that the Distances table allows you to enter several values in order to create sandwich structures with different layer materials. In this case, only one extruded layer is needed.

Click the Build Selected and Zoom Extents buttons. Click the Save button and save the model as busbar.mph. The root node has the same name as your file.

Next, create the titanium bolts by extruding two circles drawn in two work planes.

In the Model Builder, right-click Geometry 1 and select Work Plane. In the Settings window, under Work Plane 2, select Face parallel as the Plane type.

In the Graphics window, click the face highlighted in the figure. Once this surface is highlighted red, right-click anywhere in the Graphics window to add it to the Planar face list in the Settings window.

Face number 8 is highlighted in blue and the work plane is now positioned on top of face number 8.

Click the Show Work Plane button to draw the first circle representing the position of the first bolt. Click the Zoom Extents button .

Under Work Plane 2, right-click Geometry and select Circle. In the Settings window, define a circle with radius rad_1 and the center coordinates (0, 0). Click the Build Selected button . The geometry should look according to the figure.

Continue by creating the bolt using an extrude operation. In the Model Builder, right-click Work Plane 2 and select Extrude. In the Settings window, in first row of the Distances table, enter -2*tbb to extrude the circle a distance equal to the thickness of the busbar.

Click the Build Selected button to create the cylindrical part of the titanium bolt that runs through the busbar.

Draw the two remaining bolts.

Right-click Geometry 1 (in Model 1) and select Work Plane. In the Settings window, under Work Plane, select Face parallel as the Plane type. In the Graphics window, click the face shown in the figure. When this surface is highlighted red, right-click anywhere in the Graphics window to add it to the Planar face list in the Settings window. Face number 4 should now be highlighted in blue.

Click the Show Work Plane button .

Click the Zoom Extents button to get a better view of the geometry. To parameterize the position of the two remaining bolts, add the circles that form the cross sections of the bolts.

Under Work Plane 3, right-click Geometry and select Circle. In the Settings window, enter rad_1 in the Radius field, -L/2+1.5e-2 in the x edit field, and -wbb/4 in the y edit field in the Position section.

Click the Build Selected button .

Copy the circle that you just created to generate the third bolt in the busbar. Under Work Plane 3, right-click Geometry and select Transforms>Copy. In the Graphics window, click the circle c1 to highlight it. Right-click anywhere in the Graphics window and add the circle to the Input object list in the Settings window. In the Settings window, under Displacement, enter wbb/2 in the y field.

Click the Build Selected button .

The geometry should look like this. Continue by extruding the circleS.

In the Model Builder, right-click Work Plane 3 and select Extrude. In the Settings window, in the first row of the Distances table, enter -2*tbb. Click the Build Selected button . The geometry and its corresponding geometry sequence should look like this. Click the Save button and save the model as busbar.mph.

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