Sign-up for free online course on ANSYS simulations!Step 4: Specify geometry
Overview
Since we are using the 2D Spar element, we can represent each truss member by a line. A line can be created by joining two keypoints (ANSYS terminology for vertices). So we'll need three keypoints, located at A, B and C in the figure below. We'll locate the origin of the coordinate system at C and number the keypoints at A, B and C as 1, 2 and 3, respectively.
Create Keypoints
Main Menu > Preprocessor > Modeling > Create > Keypoints > In Active CS
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Enter 1 for Keypoint number
Enter 0 for X and 2.8 for Y
(The Z value defaults to zero)
Click Apply (which accepts the input and then brings back the dialog box for further input)
Note that you can move to the next field using the Tab key.
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The keypoints will now be displayed in the Graphics window along with a triad that indicates the origin of the coordinate system (coincident with keypoint 3 in our case) and the axes.
Check Keypoints
To check if the keypoints have been created correctly:
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This brings up a window listing the coordinates and rotation angles for the keypoints. Verify that you have the following:
You can rotate the coordinate system associated with each keypoint and that is what the rotation angles THXY, THYZ and THZX refer to. In our case, we don't need to rotate the keypoint coordinate system and so the rotation angles are identically zero.
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This brings up the so-called pick menu.
Click on the keypoint you want to delete. A square appears around that keypoint indicating that it is selected. (Repeat for other keypoints as necessary.)
Click OK in the pick menu.
You should see the keypoint disappear in the Graphics window. You can also check that the keypoint has been deleted using Utility Menu > List > Keypoints. You can then re-create the keypoint.
Save your work
Once you have successfully created the keypoints, save your work using
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Utility Menu > File > Save as Jobname. db
Create Lines from Keypoints
Main Menu > Preprocessor > Modeling > Create > Lines > Lines >In Active Coord
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To create the line between keypoints 1 and 3, click on keypoint 1 and then keypoint 3. Similarly, create lines between keypoints 1 & 2 and keypoints 2 & 3.
Close the Lines in Active Coord pick menu by clicking on Cancel.
Close the Lines and Create menus.
Check Lines
Take a look at the list of lines that have been created:
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The first four columns in the list should be:
The order of the keypoints for a line doesn't matter i.e. line l1 could go from keypoint k1 to k2 or equivalently, k2 to k1.
Close the window listing lines.
Modifying Lines (If Necessary)
If a line doesn't look right, you can delete and re-create it. To delete a line:
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Click on the line you want to delete in the Graphics window. Click OK. This deletes the line.
Save your work
Once you have successfully created the lines, click on Toolbar > SAVE_DB to save the database.Go to Step 5: Mesh geometry